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Catalyst Characterization - Science topic

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If feed gas flow rate is 50 cc/min how can i calculate.
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Zakia Akter Sonia, Just divide the gas flow rate by the catalyst volume, here in cc, and multiply by 60 to refer to one hour.
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How significant is the FTIR study of mixed metal oxide photocatalysts like WO3-TiO2 nanocomposites?
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Hi Aarif Shah , in gas phase catalysis FTIR can be quite useful to probe the chemistry of the surface. (In water phase, may be not much will be seen because of water interference, you can perhaps do it, who knows)
If you have a pure metal oxide powder. The FTIR spectra (ATR is preferred) of the powder will already give a few important information about the surface. First, the water molecules that may have from the atmosphere. H2O can adsorb both as molecules, but also in the dissociated form: H and OH. H2O will also be present in the condensed form due to capillary condensation. Now, the dissociated H2O is interesting! Because it denotes a catalytic process. In TiO2, the active sites dissociates the water and then the H and OH are sitting on the active sites. On FTIR a small shoulder at 3596 cm-1 denotes dissociated water for TiO2. Same is observed for ZnO. Around 1600 cm-1 adsorption of molecular water is denoted by a peak. Further absorption bands from the metal oxide itself are difficult to interpret. But things can still be improved because data science is developing as well.
Now if you are investigating the photocatalysis with WO3 and TiO2, then you can study degradation of a surface organic molecule with FTIR. The C-H stretches of long chain organic molecules show strong absorption in the 2800 cm-1 to 3000 cm-1 region. This absorption peak you can monitor during the degradation. During degradation, CO2 peaks will also evolve. In this work, we exploited the FTIR analysis for studying TiO2, WO3, ZnO and CuO. You may find this interesting:
What is also interesting is DRIFT (Diffuse reflectance FTIR). So this is FTIR where you probe the diffusely reflected signal from the sample after IR incidence. For catalysis it is particularly interesting because it gives only the surface chemistry due to reflection based probing. DRIFT cells are accessories that can bought along with normal FTIR set-ups. An in-situ DRIFT cells where vacuum can be created or gas phase reaction can be carried out is an inexpensive but powerful set-up!
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Actually I have prepared Al-VPO. But I did not get any peak of Al in the XRD pattern of Al-VPO. So it might be well dispersed or amorphous? If so then which is the active sites if I'll use it for any oxidation reaction?
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XRD should show peaks for crystalline and amorphous phases as well. Loading may be low and not as reported (5%).
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Please suggest a method to determine this practically. Please avoid mentioning the publications having the final results. The guidelines or procedure for measurement is required. Any related discussion or fruitful comments are warmly welcomed.
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It can be calculated from UV data of photocatalyst as well as DRS data of photocatalyst. While using UV data Tauce's equation is used. While in other case kubelka munk equation is ised
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Microsoft excel sheet required.
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As far as I know, the TGA results should show decreases in weight but my spent catalyst (Ni/ZrO2-SiO2) weight increased.
I know weight gain should only happen if the samples react with the atmosphere: oxidize. But then the graph shows a straight line (100%) until 400-500 ˚C and then it started to increase. No decreases at all.
I suspect that the instrument needs proper calibration. But then, only for spent catalyst have this problem. All the fresh catalysts showed a standard result in which the weight decreases. So I don't think it's the instrument's fault.
Can quartz wool or glass wool increases in weight when temperature increases?
I suspect probably a tiny bit of quartz/glass wool was mixed with the catalyst.
The conditions that I used were 30˚C to 800˚C with a heating rate of 10˚C /min and used air as the carrier gas.
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Glass wool or any other mineral wool cannot gain weight when calcined in air. However, there is a component in your catalyst - nickel, which oxidizes in air and adds weight.
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I am trying to make hard pellets of a NiO powder for Van Der Pauw conductivity measurements. Although I have a small steel iron pellet press (1.5cm diameter) and I go as high as 15,000.00 PSI, the pellets disintegrate as soon as I apply even a small pressure on them. I can't use a binder because it would change electronic conductivity, and I tried adding drops of ethanol or heating to 75 degrees °C but no luck. Any advice? 
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you have to use binder solution and make dow out of it,,then extrude it in a extruder. Further, it must be dried and calcined.
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C1s peak at 284.8 corresponding to Adventitious Carbon is a reference for the X-ray photoelectron spectroscopy (XPS. However, when using carbon-based support, say Vulcan carbon (rich in graphitic carbon), r-GO and GO for deposition of active catalyst.
The C1s peak in these cases will be dominated by sp2 carbons, not by Adventitious Carbon.
How to calibrate the XPS data in that case?
How to account for the charging problem?
Thanks in advance
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As Jurgen states, the vulcan carbon should have enough conductivity. If using a monochromatic XPS system then analyse without the charge neutraliser on and ensure the carbon is in contact with the spectrometer (e.g. pressed in to a metallic well on the sample bar), then you shouldn't have an issue. The sp2 carbon will be ~ 284.5 eV depending on how well your spectrometer is calibrated.
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Dear Colleagues,
I’m pleased to inform you that open access journal /Catalysts/ (ISSN 2073-4344, Impact Factor: 3.444) is planning to publish a Special Issue on the topic of "Trends in Catalytic Advanced Oxidation Processes". The submission deadline is 31 July 2020.
Detailed information regarding this issue, please follow the link below to the Special Issue website at:
This Special Issue is dedicated to novel achievements in the field of catalytic advanced oxidation processes. The contributions should be related to the listed topics:
· Catalytic processes in water and wastewater treatment
· Developments in Fenton-like AOPs
· Activation of Persulfates for AOPs
· Formation of sulfate radicals
· Catalytic cavitation-based AOPs (hydrodynamic cavitation and acoustic cavitation)
· Sonocatalysts
· Catalytic ozonation
· Photocatalysts—including visible light and UV applications
· Catalytic wet air oxidation (CWAO)
· Catalytic–electrochemical AOPs
· Carbon catalysts for AOPs
· Nanocatalysts
· Risk of by-product formation during water and wastewater treatment
· Developments in process control of catalytic AOPs (analytical methods, chromatographic, and spectroscopic techniques)
· Methods of catalysts characterization
· Post-process assessment of effluents toxicity
· Application of nanobubbles in AOPs
· Economic analysis of catalytic AOPs application and catalysts life cycle assessment (LCO)
· Industrial catalytic wastewater treatment
· Modelling and optimization of catalytic processes
· Green chemistry aspects in catalytic water and wastewater treatment
Detailed information regarding this issue, please follow the link below to the Special Issue website at:
Sincerely hope this invitation will receive your favorable consideration.
Best regards,
Guest Editor
Prof. Grzegorz Boczkaj, PhD. Sc. Eng. Assoc. Prof.
Department of Process Engineering and Chemical Technology, Faculty of
Chemistry, Gdansk University of Technology, 80-233 Gdansk, Poland
Caroline Zhan
Assistant Editor
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Dear Prof.
Looking forward to hear if any special issue under your editorship.
Thanks
Siddhartha
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I wonder which one is more important in means of catalyst design: Number of active sites or TOF value. TOF value already considers number of active sites but the challenging part seems to determine the active sites. Computational methods calculate TOF value without considering number of active sites and experimental methods have different approaches to estimate TOF value, in most of the papers I can not even see the estimation of number of active sites but an ambigious TOF value. If we talk about the catalyst activity TOF value is the measure but if we talk about the catalyst design, shouldn't it be the real textural properties and consequently the number of active sites?
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Dear Ebru Erunal you are asking an interesting question. Here's what we do when calculating TOFs for heterogeneous catalysts:
1. We start from its definition:
TOF = rate of reaction/concentration of active sites [=] [(mol reactant/s)/(mol active sites)] = [1/s]. Therefore, as it name implies, TOF is a frequency whose units are Hertz.
2. We consider that the rate of reaction that must be used to calculate TOF must be the intrinsic rate of reaction of the catalytic sites. Therefore, the following conditions must be fulfilled: (i) no transport limitations (mass and temperature gradients) must be present, (ii) as the reaction rate is a function of the advancement of the reaction, the intrinsic rate of the active sites must be as far from full conversion or equilibrium conditions as possible. For this, the rate should be extrapolated to zero conversion and free of the inhibition effects that products may have on the catalytic process. In a fixed-bed reactor, this means that the reactor should be operated in a differential mode; i.e. the conversion should be as close to 0 as experimentally feasible. Also, tests feeding products must also be done. In a batch reactor, this means that the initial rate of reaction is the most suitable for the calculation. For calculating the latter, samples must be taken as close to zero time as possible.
3. Measuring the concentration of active sites may be the most difficult part since one must answer the question: what is the active site for the reaction that you are investigating. Typically, you have the following possibilities: (i) for catalysts based on metallic nanoparticles (supported or not) where the latter are responsible for activating the most stable reactant (e.g. in methane oxidation, methane is hardest to activate than the oxidation agent -O2 or H2O, etc-), the number of moles exposed at the surface of the catalyst is well accepted as a metric for estimating the number of active sites. As you may know, this can be measured by chemisorption of some adequate probe; e.g. H2, CO, etc. (ii) for catalysts based on (supported or unsupported) oxides, sulfides or nitrides, the active site is also normally associated to an exposed metallic center or to a given structural site. Therefore, certain assumptions are always before defining a metric for the concentration of active sites. As an example, MoS2 catalysts have sites located in different parts of its geometrical structure and the specific role of these different sites depends on several factors associated with the type of molecule that is reacting, the reaction conditions, the possible interconversion of sites, among others. (iii) for bimetallic catalysts, e.g. Pd-Pt, one would need to define the specific role of each metal in the reaction. It may be the case that both metals are active in the reaction or that only one of them is. Therefore, as in the case of (ii) certain assumptions about the nature of the active sites -and reaction mechanism- must be made. (iv) For bifunctional catalysts; i.e. those where the support also contributes active sites, one should take into account the same as in (i).
Well, the points above are our rough guide for calculating TOFs. We have got help from literature such as the few ones cited below:
1. Foggler's Elements of Chemical Reaction Engineering
2. Chorkendorff and Niemantsverdriet's Concepts of Modern Catalysis and Kinetics
3. Froment and De Wilde's Chemical Reactor Analysis and Design
4. Harris et al. Consequences of product inhibition in the quantification of kinetic parameters, Journal of Catalysis 389 (2020) 468–475
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Could the presence of ligand on a catalyst surface reduced the reactivity of its surface? If yes/no, please explain why?
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this depends on which type of ligand used
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The NH3-TPD of commercial silica (S.A= 223m2/g) has been run on a Micromeritics 2900 AutoChem II Chemisorption Analyser to determine total acidity. However, there was no peak observed post-run.
The experimental conditions are as follows:
The material was initially pre-treated by heating to 400 ºC under a stream of argon (30 mL/min) at a rate of 20 °C/min for 30 min and then cooled down to 90 ºC under the same stream of argon. A 5 % NH3 in helium gas mixture was then passed through the system and allowed to adsorb onto the surface of the catalyst for 30 minutes. Helium gas (30 mL/min) was then passed through, while the temperature was ramped from 100 °C to 700 °C at a rate of 10 °C/min. The amount of ammonia desorbed was monitored using a TCD.
Why are no peaks observed? is there a possibility the surface hydroxyl groups (if any?) are too weak to interact with NH3 ?
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Thanks for the valuable input Martin A Thomas !
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Typically xylene isomerization catalysts convert ethylbenzene (EB) to benzene. But for example, IFP's Oparsi plus catalyst convert EB to xylenes isomers.
It is a big help if anybody tells me what promoter can do this reaction.
I know hydrogenation metals like Pd can convert EB to naphthenes and acid sites of zeolite support are suitable for the conversion of naphthenes to xylene. But I think conventional catalysts have noble metals like Pd and they convert EB to benzene.
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The present invention relates to a method for converting a feed mixture comprising an aromatic C8 mixture of xylenes and ethylbenzene in which the para-xylene content of the xylene portion of the feed is less than equilibrium to produce a product mixture of reduced ethylbenzene content and a greater amount of para-xylene, which method comprises contacting the feed mixture at conversion conditions with a first catalyst having activity for the conversion of ethylbenzene, and with a second catalyst having activity for the isomerization of a xylene.
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I have a catalyst with Cu as the active metal supported on zeolitic and non-zeolitic supports (several different samples). Initial XRD studies and literature studies have indicated the co-existence of both Cu+ and Cu2+ species on my catalytic surface. I need the Cu+/Cu2+ ratio inorder understand my catalytic reaction results. I don't have XPS at my lab so I am striking it off from my options. Please do let me know if there are other methodologies.
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You can also use XANES or ELNES to determine the valence from line ratios.
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The binding energies for my copper based catalyst are strangely low. I do not understand why this is the case. I have looked through different manuscripts but have not found values similar to this. Attached are the deconvoluted peaks for Cu and O1s to better explain the results i obtained. Calibration was done using C1s at 284.8eV
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A low binding energy due to a charging effect would be somewhat odd because charging usually leads to increased binding energies. An initially negatively charged reservoir area should vanish for a long enough exposure time.
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I ran a CO-TPR experiment on an gamma-alumina supported iron catalysts. I'm getting two invert peaks, a small peak at the beginning and a large peak at the end of the temperature range. Iron oxide is normally reduced at around 300C, 480C, and 600C, while I'm just getting the second peak around 480C. I used 10%CO/90%Ar blend as the analysis gas. Sample was degassed under flow of He at 500C, then cooled down to ambient prior to the experiment. Does anyone have any idea why the invert peak is showing up? I have attached the TPR graph and also the experiment log.
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For consumption, you will observe the positive peak and for desorption of surface species, you may observe the dipping or inverted peaks in TPR
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I am looking to test the methanol oxidation reaction of catalysts I have prepared. I wish to do this using materials I currently have. I have a glassy carbon electrode for the RDE set up, but do not want to ruin it by depositing my catalyst and nafion on it.
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I have a question about how to recover catalyst that we are going to deposit on GC electrode for ORR/OER? I want to recover that catalyst to do XPS analysis.
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I had done zirconia XPS, from that data I want to calculate % Zr & % O.
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Thank you Jiaqi Luo
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I have passivated my catalyst to prevent oxidation; now before promotter addition, I would like to know the temperature to re-reduce the catalyst. That can be presicted by TPR. For the latter, the maximum temperature to reach depends on the thermal stability of the catalyst, hence TGA is beleived to satisfy this aim. I would to know more information that can be derived from such results or if once come accross a similar project.
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Besides the thermal stability, you can calculate the activated energy, the mass ratio between the combustible and incombustible fractions, and integral procedural decomposition temperature (IPDT).
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Hey guys, can you help me solve one question about ZSM-5 deactivation?
The HZSM-5 catalyst was used for DME synthesis reaction with Cu/Zn/Al catalyst. After reaction, the used HZSM-5 catalyst was characterized for TGA and NH3-TPD. The TGA showed 2-3% coking on the used HZSM-5, however, NH3-TPD showed its acidity is close to the fresh HZSM-5. I don't understand.
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I did not understand what you mean with pretreatment. I call as pretreatment the 2 initial steps of NH3-TPD; (1) surface cleaning and (2) NH3 sorption at given temperature. The carbon decomposing will affect the results during the desorption step which is performed by increasing temperature, because the strong acidity of zeolites may catalyze the carbon decomposition even when oxygen is not present; the TCD detector will not distinguish between CO, CO2, NH3, or other hydrocarbons. Note that you need to use high temperatures to completely desorb NH3 from zeolites. However, if you use an MS detector instead of a TCD detector, this problem can be solved. In this paper (open access) I described how I used both HR-TG and NH3-TPD, but I did not have the carbon problem during my NH3-TPD measurements:
The TPO will give you similar results than that of TG, both will burn the deposited carbon. Particularly, I find the HR-TGA better due to resolution. You can distinguish better the events and can play with kinetic studies as well ( - and references therein).
The deactivation may not occur only at the surface. Carbon is deposited by polymerization followed by carbonization. The polymerization if facilitated if precursors do not diffuse out of the pores quickly, which is quite common for zeolites. That's one of the reasons many researches work on the development of mesoporous zeolites to increase catalyst stability. Being said that, you need to identify the nature of the deactivation. If that is by carbon deposition, you need to characterize if carbon is being deposited into the micropores or external surface. If it is externally deposited, you reaction is likely occurring only at the external surface rather than internal (diffusional constrain); considering your catalyst results.
Better than any other techniques mentioned above, I would recommend low-temperature nitrogen sorption of fresh and spent catalysts. By looking at the micropore volume, you will know if carbon is being deposited internally. The same apply if you are depositing metals in the zeolite. Ideally, you can built your whole discussion by connecting all these techniques.
Best Regards,
Alexandre Gonçalves
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Hi,
I am working on making an air cleaner, now I need to make a "smoke generator" for my demo device, to show its working principles.
it needs to be stable and generate almost uniform and continues smoke.
my question is that What is the simplest and cheapest method to make a stable smoke generator for this purpose?
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Use fragnant plant material mixed with oil to generate smoke by heating/ electric heating in a small chamber. This material is used in temples during prayer!
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I have a PM from @Mahsa Akhgar as follows:
Hi dr alan
I am writing my paper and i face many questions. I hope you could help me. I have synthesized sapo34 catalyst with surfactan but my data has not a specific trend that i cnfused. One of my question is that bet surface area is in relationship with crytal size obtained from scherrer eq. or with particle size obtained from fesem analysis?
Excuseme can i have your phone number or email to ask my questions?
Thanks a lot
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@ Mahsa Akhgar Obviously the answers on Research Gate should benefit all users and allow many experts to comments. Hence I am posting your question on the open forum.
You ask: ' One of my question is that bet surface area is in relationship with crytal size obtained from scherrer eq. or with particle size obtained from fesem analysis?'
My response is why would you expect these to be the same or even have correspondence except in general terms? These techniques measure totally different properties of the particle or material. BET explores all the surface including pores to obtain a specific surface area. Scherrer equation deals with line broadening of XRD peaks and is related to crystalite size. The eqation has meany limitations (strain and instrumental broadening is not considered; the equation is not applicable much above 10 nm). Microscopy and SEM is a vital and essential technique. Particle size is measured with SEM (but is a 2D representation of a 3D particles). Particle size distribution is not - separation of primary, aggregated, agglomerate particles; need for 10000 truly random particles to be measured to get the mean to 1% standard error etc).
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Individually, one of them is more active than the other.
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This is a very general answer for your general question. Synergism is not a common phenomenon but an exception. The synergism might take place if two systems have common intermediates. There is no synergism if the systems don't overlap.
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Hello everybody
I measured BET surface area and Electrochemically active surface area (EASA) of synthesized MnO2 nanomaterial. EASA was obtained by using Cyclic voltammetry at different scan rates (considering slope (Cdl) by plotting current (mA) vs. scan rates (mV/s)). the slope was obtained to be 0.0487 mF. Here, the carbon clothes (1 cm2) was used as a substrate for MnO2 nanomaterial, and considered Cs = 0.02 mF/cm2. EASA calculated from Cdl/Cs. The mass loading of the MnO2 on carbon cloth was about 0.00036 g/cm2.
1- First question is that "considering Cs=0.02 mF/cm2 as specific capacitance of an atomically smooth carbon meterials" is correct?
2- Second question is that : The BET surface area of MnO2 was obtained to be 17.5 m2/g. But EASA was obtained to be 0.0487 mF (slope), 2.435 cm2 (from Cdl/Cs), and 0.68 m2/g. Why there is high difference between obtained BET surface area (17.5 m2/g) and EASA (0.68 m2/g). Is there somethings wrong with the EASA result or it is correct?
I will be thankful if you could help me regarding two above questions.
Thank you
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Your measurements are what one would expect. BET will probe the entire surface area available to N2 gas (at - 196C) - ~ 14 Angstroms2 and this includes the meso- and macropores. Your active surface area will be much smaller than this.
Always believe what a calibrated/verified instrument delivers.
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Anyone having experience of NH3-TPD analysis with activated carbon?
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Dear Riikka
Please go through Shah et al. 2015 (Mater Sci Engg B). I do hope you can get some help.
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I put this question, because some researchers believe with no real grounds that this phenomenon is connected with the nonexistent surface heterogeneity of the thermally-stabilized catalyst of NH3 synthesis.
Our answer to this question is simple and unambiguous. Oxygen contaminates Fe catalyst because its heat of chemisorption at Fe is very high (about 670 kJ/mol O2, D. Brennan et al, Proc. Roy. Soc., A256, 1960, 81-105; see also https://www.researchgate.net/publication/235342853_Molar_heats_of_chemisorption_of_gases_at_metals_Review_of_experimental_results_and_technical_problems), while the heat of N2 chemisorption is about 125 kJ/mol only and because the temperature coefficient of chemisorption of two-atomic gases at metals is rather small (R.J. Madix, J. Benziger, Ann. Rev. Phys. Chem., 29 (1978) 285-306; see also https://www.researchgate.net/publication/235799473_Oscillation_theory_of_heterogeneous_catalysis_and_its_use_for_identification_of_the_reaction_scheme_and_kinetics_Catalytic_liquid-phase_benzene-ring_hydrogenation_as_an_example), while the temperature coefficient of the H2 interaction with Fe(Oads) is rather high.
It is shown that the applicability of logarithmic isotherm to some adsorption and catalytic data is explainable by the “pantophagy” of logarithmic functions over some fields of parametric variations; as for linear segments in the galvanometric charging curves obtained in some electrochemical works, there are no independent proofs that they result just from H2 chemisorption and it is not proved that the processes attributed to these segments are the equilibrium ones (https://www.researchgate.net/publication/235342837_Surface_homogeneity_vs_heterogeneity_problem_for_thermally_stabilized_crystalline_bodies_and_the_nature_of_heterogeneous_catalysis, p. 10;
Thus, the return to the opinion on a surface heterogeneity of thermally stabilized catalysts in their catalytic activity has no scientific grounds and sends us back to the erroneous views of the half-century' prescription.
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Read my answer to Miroslaw Crzesik and Peter Broadhurst . My question is not about contamination of the Fe catalysts by O2 but about the problem on the "surface homogeneity vs. heterogeneity" of thermally stabilized catalyzing crystals or poly-crystals by their chemisorption and catalytic activity. You can file your claims not to me but to A. Avetisov, the author of the paper “Mechanism of Oxygen Poisoning of Ammonia Synthesis Catalyst” by the address
https://www.researchgate.net/publication/226288571_Mechanism_of_Oxygen_Poisoning_of_Ammonia_Synthesis_Catalyst and of other papers of this author on the theme of iron contamination in NH3 process by O2, where he consider catalyst surface as the heterogeneous one. As for the phenomenon of contamination of this catalyst by oxygen as such, I agree with you that it has no important practical significance at present time.
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Can it be explained by any theory?
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Ti has +4 ox.state and here chloro ligand is -1 therefore 4 ligands donate l.p. of electrons to empty vacant S and 3 p-orbitals make sp3 hybr. and geometry wil be tetrahedral.
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I'm looking for thermal conductivity value (W/m.K) of H-ZSM-5 zeolite catalyst.
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Hello Ghasem:
You can see this intereasting paper related with your question:
Materials Chemistry and Physics
Volume 75, Issues 1–3, 28 April 2002, Pages 178-180📷
Thermal properties of zeolites: effective thermal conductivity of dehydrated powdered zeolite 4A
Author links open overlay panelVladimir V.MurashovMary AnneWhiteShow morehttps://doi.org/10.1016/S0254-0584(02)00051-2
Regards
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I want to know how CA is explained or interpreted in terms of stability of a catalyst material. Can it be used for pointing out anti poisoning ability of a nanocatalyst like Pd ( for eg: while testing for EOR or MOR )
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The current density decreasing means that the process obeys to the Cottrell equation.
A stable current density suggests that a stationary state is reached and the process is controlled by diffusion.
The probably factors that influence the current-time transient are: electrolyte concentration, pH value, conductivity of the catalyst, temperature.
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Assume we have to deposit gold nanoparticles prepared using thiols as capping ligand and I wish to deposit it onto the SiO2. To use them for catalysis I need to remove the ligand, which will eventually result in agglomeration of gold nanoparticles. What are the strategies to avoid this?
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Why put the ligand on if you have to remove it? Simply start with chloroauric acid, absorb on the support, and then reduce with an appropriate reducing agent e.g. hydrazine hydrate, H2, citrate etc...
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In fuel cell papers, because they wanted to reduce the precursors of metals to deposit them on their intended support they used reducing agents. However, here I want to exactly fabricate PbO2 on the carbon black powders. Do you think that I should add reducing agent or not. I feel that it is better not to add it. However, I'm not sure whether ethylene glycol (my solvent) can change the PbO2 structure (I mean like oxidizing pbo2 to pb3o4 or some thing like that). Would you please give me your recommendations.
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Ethylene glycol is a well known polyol (it has the ability to dissolve some salts, at certain temperature, and reduce the resulting metallic ions to there zero oxidation state at another temperature).
Thus, in your case, there is no benefit for using ethylene glycol. however, the use of oxidation reagents like hydrogen peroxide and the hypochlorides is very necessary to get PbO2.
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I'm planning to establish a setup for probing with acetonitrile (reactor and spectroscopy). Is there any concern about the molecule staying in the system indefinitely, as in the case of pyridine? The whole setup will be done using stainless steel tube.
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Hi Lars,
It's a flow reactor setup (fixed bed), so acetonitrile will be bubbled into the reactor (bubbler/saturator is chilled to manipulate the partial pressure). So it's a continuous system, I need also to see the stability of the ACN at that temperature, I wouldn't want ACN to decompose into HCN for both safety and the system's integrity.
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Be careful with low range of 2theta. Remember that the accuracy (error) of 2theta - is strongly depends on the angle. Thus, observation of a shift at angles > 50-60 2theta is more accurate and right. Just compare, if any shift is found in parallel to low angle-distortion. Please, see the attachment.
Mrs. Luma M. Ahmed,
A "red shift" is a non-relevant term in XRD - it is about the spectroscopy.
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Imagine that there are multiple parallel and series first-order reactions. Which reaction is used to represent the reaction rate in the Thiele modulus equation for a sphere, sqrt(k*a^2/D) on pg 46 of the link? The slowest reaction?
E.g.
1) A->B
2) B->C
3) A->D
4) D->C
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Introducing the Thiele moduli primarily simplifies the form of mass and energy balance equations.
There are no general rules for simplifications of balance equations. One need to consider the rate of reaction / reactions, their reversibility or not and the transport resistances. It is best to use the reaction overall rate / rates when passing from the catalyst grain to the reactor level.
Regards,
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Acid site and metal site can affect together in the reaction condition. So, it can reduce the catalytic activity since the metal nanoparticle sites cannot survive in the presence of acidic situation. 
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I recommend to you, after the preparation of the catalyst to submit it to stability tests. In order to transform the unstable species or tear the active species, and after the stability tests you can prove the catalytic properties in the interest reactions.
In addition, you can determinate the catalytic species who survive to the stability tests.
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I have tested a zsm-5 based catalyst in EB dehdrogenation reaction, and then performed FT-IR analysis for spent catalyst. A peak has been appeared which apparently belongs two both the catalyst and also coke (they cover one another).
How should I interpret this phenomenon?
If you have a source for this situation, would you please introduce?
Thank you in advance
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Dear Richard,
Thank you so very much for the offer you gave. I will ask my supervisor to get a permission.
Appreciate it sincerely
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After a solid-liquid heterogeneous catalytic reaction, the catalyst is covered with carbonaceous deposits. I want to analyze the spent catalyst by Raman and maybe also by DRIFTS in order to determine the nature of the coke/deposits. Ideally, if the nature of the deposits allows it, I'd also like to run a TGA in order to determine the (average) amount. But before that, I have a separation problem. How can I remove the remainder of the liquid (organic, b.p. ~240°C) while altering the catalyst and the coke as little as possible? I think it's necessary to remove as much of the liquid as possible, as otherwise it is likely to oxidize and form a gum layer on top of the catalyst. I'll greatly appreciate any suggestions.
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we have used a soxhlet extraction technique to achieve this in the past. Effectively washing the solvent out using a miscible low boiling solvent.
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The durability test was done by using the following condition: 
 air saturated 0.1M HClO4 , 500mV/s , 1-1.5V V RHE.
Catalyst Preparation:
1mL ethanol, 0.01 catalyst, Nafion ionomer(5wt%) 2 μL.
before durability test, I did cv and ORR. After ORR, I did ADT test.
But, during durability test, I didn't found any significant change.
I made also Pt/PCNF, but there is no change as we see in the paper.
Besides, during CV, at lower scan rate such as 20mV/s Pt-H ads/Pt-H-desorp peak were lower than the peak for pt-oxide formation. But at higher scan rate such as 50mV /s , the peak was okay.
Is anyone have that experience? or do you have any suggestion for that?
Thanks in advance
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That looks like you approximated the newer protocol DOE AST, but most of those are performed in a full cell. By keeping the system flooded, you're protecting your catalyst layer to an extent. Also, with a low wt% PFSA (5% vs. 30%) + absence of a membrane, you're substantially reducing exposure to superacids from the membrane/ionomer, which definitely plays a role in Pt corrosion, and likely in support corrosion as well.
That said, you referenced a paper that did see degradation - was it in an identical system and scan rates? Either way, it would be an interesting comparison to perform the old AST, 400 h 1.2 V hold. The new ASTs were made with full cells in mind, so it may well be that the translation to RDE analysis simply failed to translate similarly.
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Generally to know the porosity of the material we use BET characterization. Here im working with catalyst and i want to know the estimation of number of active site of the catalyst. Please help to know this issue. 
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It depends on what is your catalyst and your metal. I would recommend gas chemisorption, since it can measure directly the amount of active sites.
If you do a search in Google, you will find a lot of information. Including lots of scientific articles on this topic. Give it a try!
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Please answer the question as your earliest will helps to improve my concepts.
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Dear Sunil,
Its a very broad question asked in a very narrow sentence. Well, I believe first you need to look for the mechanism of the overall catalytic cycle of whatever reaction you want to work on. The catalysts will not only account for reaction specificity but also determine substrate specificity. I mean, the catalyst might be catalyzing the reaction by binding to a particular compound in its particular form/geometry. And if, this is the case then binding site and catalytic site would be same for that reaction and substrate and reaction specificity differences could be eliminated from the picture.
Also, it might happen that the catalytic site in the reaction is not exactly same as the binding site for the compound. In that case, binding site becomes substrate specific because it is only dependent on the geometry/position of substrate molecule in situ during the catalytic cycle. On other hand, catalyst is catalyzing the overall reaction so it is not dependent on the substrate's position.
May be you can go through the attached PDF file. It is a helpful guide for catalysis. 
Thanks
Sachin
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how we can select catalyst, actually i want to replace acetamide by another catalyst in my acid chloride synthesis reaction.
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For the acyl chloride synthesis make sure you: use
- use fresh SOCl2 (this is a hygroscopic substance that hydrolyzes);
- distil the unreacted SOCl2.
For the amine:
- use freshly distil reagent (without brown impurities);
- keep in brown recipients in the dark and low temperature.
Run the reaction in clean and dry glassware and use a trap for the HCl. 
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I have prepared a solid base catalyst from a natural product for the preparation of bio-diesel at different temp. The catalyst is consist of lots of metals and their carbonates, oxides, sulphates, etc. I have characterised it very well. All the characters are interesting at different temp. I like to share one out of them-
The particle size (PZ) usually decreases with increase in temp. But in case of my catalyst, the PZ decrease up 590 deg. preparation temp.  and increase up to 900 deg. and then again decrease up to 1050 deg. preparation temp.
Is this for the melting point of different metals? Are they fused and as a result increase in PZ? Please share....
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You did not let your compaund catalyst to fully answer your question.
Up to 500 0C carbonates and sulfates decompose.
CaCО3 = CaO+CO2                             2CaSO4 =2CaO + 2SO2+ O2
Oxides are formed, The catalyst particle size decreases. Up to 900 0 C, the sintering oxides. Increasing the size of the nanoparticles. The catalyst has a powder with a blank space. After 5010 0С some metals melt and fill the void. The particle size decreases.
Best regards.
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I found in some articles, concerning the hydrogenolysis of aromatic alcohols using Raney catalysts, that the amount of catalyst used for the reaction is quite high. In some examples are reported substrate to catalyst ratio in the order to 2:5 by weight for Raney nickel and 2:4 by weight for Raney cobalt. Is it because the low activity of the catalyst?
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Dear Alberto,
In the case of H-transfer reactions or even in some hydrogenations with molecular hydrogen as H-source, this is usually because of the low activity of the catalyst. Nonetheless, it is important to keep in mind that in the definition of catalyst, the concept amount is not present. Although this might sound a bit non-sense, one of the largest industrial catalytic process, the catalytic cracking (FCC) utilizes a huge amount of catalyst which needs to be continuously regenerated every 7s. According to the IUPAC gold book, the term 'catalyst' is defined  as:
A substance that increases the rate of a reaction without modifying the overall standard Gibbs energy change in the reaction; the process is called catalysis. The catalyst is both a reactant and product of the reaction. The words catalyst and catalysis should not be used when the added substance reduces the rate of reaction (see inhibitor ). Catalysis can be classified as homogeneous catalysis, in which only one phase is involved, and heterogeneous catalysis, in which the reaction occurs at or near an interface between phases. Catalysis brought about by one of the products of a reaction is called autocatalysis. Catalysis brought about by a group on a reactant molecule itself is called intramolecular catalysis. The term catalysis is also often used when the substance is consumed in the reaction (for example: base-catalysed hydrolysis of esters). Strictly, such a substance should be called an activator.
I hope that this answer helps you in your research.
With best wishes,
Roberto
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Note that, I have calcined my catalyst at 800 oC based on TGA result which became stable, with no weight loss after 800 oC.
The reaction temperature is 900 oC
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Yes it is better to calcine the catalyst material at higher temperature than the catalytic reaction temperature as catalytic activity would be affected for following reasons.
1) Sintering reduces the surface area of catalyst.
2) Phase change/Phase segregation can result at higher temperature.
3) Reduction in amount of lattice/surface oxygen can occur with increase in temperature.
4) Increase in availability of lower oxidation states of metals at surface can occur due to decrease in lattice oxygen.
So for stable and durable catalyst it is important i feel.
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Hi, I'm doing a little research for my classes about the catalyst for ethanol steam reform for hydrogen production. So far I found these catalysts:
 Cu/Ni/γ-Al2O3
Co/Al2O3
Co/SiO2
Rh/γ-Al2O3
and Cu and Ni in 
ZrO2 ZrO2/Al2O3 and ZrO2/Y2O3
Do you know any other catalyst? Do you suggest an article about it? Thanks =)
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I was reading this article that could be helpful :
Regards
Zin Eddine
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Hi Dear 
I have Xrd file of different phases of MnO2 and the figure shows some peaks which some of them are for α- or β- or γ-, and δ. But I can not distinguish them because some peaks are so close together and I dont know the exact place of peaks for mentioned phases. Please Guide me to find them. 
I will be grateful  for your help. 
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Dear Nazanin,
    Sorry for the delayed response. Yes the peaks show the alpha and gamma phases in the top most sample. In my opinion this behavior shows the transition state of alpha phase to gamma phase. if you have any query don't hesitate to contact me.
Regards
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Hello Dears
Is there relation between performance and properties of zeolites for different catalysis process?
For example for catalytic converter, zeolite should investigate in terms of TPD test.
Are properties of zeolites general or for each process different?
With regards
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dear Amanj.
it's pretty obvious  that there is a relation between performance and properties of zeolite but it doesn't mean in all  processes have the same performance. in the chemical process, its function strongly dependent on the conditions (temperature, pressure and etc). for example in the pyrolysis process which is carried out at Higher temperature, zeolite as a catalyst drives the reaction towards Aromatization Reactions but  in moderate temperature can act as surface catalysts for the ketonization reaction.
it would be better if you explained a little about the process that you are considered. but, as far as I know, the characterizations is not limited to just TPD. in addition to the acidity of catalyst, it is important that you investigate the dispersion of active phase over the zeolite through H2 chemisorption or TEM and also if you modify the zeolite, you can check the changes that happen during modification. for instance, investigation of changes in surface area, metal dispersion and also particle size.
finally, It is my pleasure if I can help you.
Good luck
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Dear All
I prepared N doped TiO2 and I found there are two additional peaks showing in XPS analysis at 716 and 836 eV. Please, may you help me to know what are they belonging to?
Thanks in advance
Regards,
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Dear Amal EIsonbaty,
Coincidentally, I am working on the XPS analysis of TiO2 with oxygen vacancies. Please refer to my result enclosed. I hope it may be useful to you.
Regards
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Hi,
I am using MoS2 catalyst for hydrogen evolution reaction. Attached is the Nyquist plot of the MoS2 catalyst.
The measurement conditions are:
1)       open circuit potential
2)       frequencies: 100 kHz to 10 Hz
3)       amplitude 10 mV
The obtained Nyquist plots are deviated from semicircles.
What information could I get from the plots? How could I interpret them?
or
How could I improve my measurement?
Many thanks!
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To get a semicircle Nyquist plots for  HER, you should choose the onset potential instead of OCP and lower frequency should be 10-100 mHz instead of 10 Hz.
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I'm trying to simulate a research paper in ASPEN, so i need to multiply the rate equation with a constant which converts the units from  [(molecules) /(site)(second)] to  [(molecules)/(grams of catalyst)(second)].
please suggest a Book where i can understand determining Turn Over Frequency for a catalyst.
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There is no such conversion.  There is an example in the attached file (PP 2-3) to  do another conversion.
In any case what you need is how much "sites/gm of catalyst". The frequency factor "A" of your rate equation must be multiplied by the factor "sites/gm of catalyst.  You have to use this new frequency factor in your simulation
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The concentrations of Na2CO3 in the materials are in the range of 10-20 wt.%. Using TEM seems to be straightforward but I wonder if it is an appropriate approach since the atomic number of Al (27) and Na (23) is close to one another. The similarity in atomic number supposes to decrease the contrast and makes it difficult to distinguish between Na and Al. I could not use Scherrer equation since all the XRD peaks corresponding to Na2CO3 disappeared in the supported material.
If not, what technique would give me this information? 
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Hi 
There are different techniques where you can measure the particle size, the most common are TEM, EDX
Have a very good day
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Pyridine FTIR used to analyse the Bronsted and Lewis acidic sites over a solid catalyst. Pyridine vapour adsorbed on acidic catalysts while FTIR spectra is recorded to show the location of Bronsted (1550 cm-1) and Lewis (1450 cm-1). Why a spectra at 1490 attribute to both B and L sites. How pyridine behave here on the surface of catalyst?
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Dear Muhammad,
If the nitrogen in pyridine bonded with metal on the surface of the catalyst, so this is a Lewis acidic sites, however, if it bonded with the hydrogen in OH group, this is Bronsted site (as seen in the photo attached)
In case the surface group of the catalyst has M-O-H group so it will form both lewis and Bronsted acidic sites  
please find the attached paper that discussed this
hope this helping 
Thanks
Ahmed
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In addition to the pyridine FT-IR method are there any other methods that can be applied to measure the Nature of different acid sites such as the Bronsted and Lewis acid sites of a catalyst?
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Dear Vijaykumar Marakatti
You are very welcome
Have a very good day
Ahmed
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Right now we are trying to determine acidity of HzSM5 by pyridine adsorption. We have a temperature reaction cell from Harrick. We pelletize our sample in KBr. After under vacuum at 300 C for 2 hours, pellet is cooled to 50 C. This followed by sending pyridin with N2 flow over the pellet for 30 min. Then we check for pyridine adsorption by taking FTIR spectrum. Then we heat to 100 C and keep under high vacuum for 1 hour. Then spectra is taken. Upto now we couldn't see any peek of pyridine adsorbed on zeolite. Any ideas about what to do?
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Dear Colleague Yilmaz,
1- The total number of acidic sites (sites. m-2) over each catalyst can be measured using the temperature programmed desorption of pyridine (TPD-pyridine) as the probe molecule. The details have been described in previous publication (attached).
The acidity populations over the surface of catalysts, under investigation, were measured thermogravimetrically using the adsorption of pyridine as probe molecule. Small portions (50mg) of each sample were pre-heated at 250°C for 2 h in air before the exposure to the probe molecule. 15-20 mg of pyridine–covered samples were subjected to TG analysis on heating up to 600°C (at 20°C/min heating rate) in dry N2 (flow rate = 40 ml/min). The mass loss due to desorption of pyridine from the acidic sites, was determined as a function of total surface acidity as sites.g-1cat.
2- To detect the Bronsted acidic sites, you can use 2,6-dimethylpyridine as a probe of the strength of Brønsted acid sites.
Finally if substracted the number of acidic sites from step 2 (Lewis +Bronsted) from step 1 (Bronsted only, you can get the number of lewis acidic sites
However, FTIR- Pyridine is only used to distinguish between the Lewis and Brønsted
Hope this helping
Have a very good day
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Is there a difference between crystallite size and particle size? If and which one affects catalysis? does TEM give crystallite size or particle size?
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Dear colleague Lebohang,
Crystallite Size is Different than Particle Size. A particle may be made up of several different crystallites or just one crystallite so in this case (particle size = crystallite size)
Crystallite size often matches grain size, but there are exceptions
Crystallites are coherent diffraction domains in X-ray diffraction.
Particles are chunks/pieces (usually very small, below 1 mm) of solid matter, ensembles of atoms. Particles can be as small as two atoms (the nitrogen particle for example, N2)
Grains are volumes, inside crystalline materials, with a specific orientation.
Particles can be polycrystalline, single crystal or amorphous. A 100 nanometer particle of gold, for instance, can be made of:
a single gold crystal,
many grains with a grain size <100 nm,or of amorphous gold.
Grains are often crystalline. Crystallites for the sake of simplicity are frequently, although erroneously, identified with grains.
Crystalline size sometime was written as sub-grain size,and a particle consists of lots of grains or sometimes one crystal.And their size as the figure attached
Hope this helping
Thanks
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Hello dears
I want to evaluate porosity for filter diesel particulate and monolith and my sample is as honeycomb (usage as substrate for environmental catalyst) but power.
Can anyone help me to find possible procedure?
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Dear amanj
You can  use ASTM D4284 to determine both the size and volume of pores. Moreover adsorption based methods like BET can help you.
Please note that image based method isn't proper for your sample because of limitation in measurement of inter-connected porosities
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I have synthesized a catalyst and I am applying it in catalysing biomass pyrolysis reaction to obtain bio-oil. The catalyst shows best performance when it is used at a concentration of 7% giving the maximum amount of bio-oil. We do not see any further increase in the amount of bio-oil even after increasing the catalyst concentration beyond 7%. Why is it so?
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Many homogeneous catalysts decompose by pathways that involve multiple catalytic centers coming together. Whether it is formation of a stable off-cycle dimer, disproportionation, comproportionation, or aggregation/precipitation, these reactions will be 2nd order or higher in catalyst, while the desired reaction is usually 1st order in catalyst. Therefore, there is a catalyst concentration above which the reaction will suffer.
Another possibility is that there is a byproduct of catalyst activation that can interfere with the reaction. I once ran a reaction using a Pd2dba3 precatalyst where the displaced dba caused problems if I used too much...
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catalysis
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I also have to ask the question about "substrate"?  However, in very general terms, the later, heavier metals, such as Ru, Os, Rh, Ir, Pd and Pt have much more electron density and so the types of binding that require back-bonding such as CO, CH2=CH2 etc will bind better to those metals.  In addition, H2 binds by breaking into 2H on surfaces and electron density also helps those reactions.
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My research is about one of hydrotreating process, and my focus is how to Hydrodearomatization napthalene on gasoil fraction (naptha).
The catalyst was NiMo with Al2O3 as a promoter. But, I use the phosphorus acid (H3PO4) as addictive (but it was called impregnation). The problem is, I cant find what was the real effect and how the structure NiMo-P.
Please help me to solve this problem and I cant find paper/journal who explain this. 
I hope everyone can help me :(, thank you.
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Impregnation is basically a method used for infusion of a solid in a support material to obtain a micro/nanoconfined state. So most probably, the H3PO4 which is coming in contact with the NiMo through capillary action, activating the NiMo surface or depositing as NiMoP. I think XPS and 31P SSNMR can help you understanding how the H3PO4 behaves in presence of NiMO. 
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Why when I increase the doping metal the TPD-NH3 show increasing in acidity then show me decrease at high consecration of the metal?
I am using Ce doped with activated carbon when I increas the  consecration of Ce the acidity was increase then Show me decrease is there any explanation for this phenomena 
thanks
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By the way, I have noticed that you used activated carbon (AC) as support. You'd better check the acidity of AC first.
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we have prepared solid lewis catalyst by the immobilization of various Lewis acids on the solid support. we have carried out the reaction under solvent-free conditions and also reused the catalyst for five consecutive runs. how can we determine the effect of ph on the stability and activity of the catalyst. further we have checked its thermal stability by carrying out the TGA analysis of fresh and reused catalyst. How can we determine the effect of temperature on the stability and activity of the catalyst
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For  checking the effect of temperature on the stability of the catalyst, I think TGA  of the catalyst should be done which will check the catalyst stability at different temperatures and for checking its activity at different temperature, you should carry out the reaction with a given amount of catalyst at different temperatures and will see whether the increase in temperature increases the reaction rate (e.g check the time taken for a reaction it increases, decreases or remains same) or not.
For checking the effect of pH on the activity of the catalyst, carry out your reaction with a given amount of catalyst under acidic conditions, I think it will increase your catalyst's activity and if you use basic conditions it will decrease your catalysts activity. As far as stability of the catalyst is concerned, I think using a basic medium will affect the stability of the catalyst because your catalyst which is acidic will interact with basic medium and using a acidic medium will not affect your catalyst's stability.
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I need to compare the performance of Fe-based catalyst with Pt-C as the baseline for ORR. I am using the LSV at 1600 rpm for comparison. The problem is I am not sure how to interpret the data. The onset potential of the Pt-C is 88 mV more positive but the limiting current density is 14% smaller with the same mass loading. I want to know which one represents the number of active sites limiting current density or the onset potential? can I make any comments about the intrinsic catalytic performance based on the LSV performance if the mass loading is the same or both electrodes? I should make this note that the catalyst is just Fe3O4 with carbon black!
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To your basic question
1. Diffusion limited current is scaling with the geometric surface if the loading is high enough. See Levich equation
2. The onset potential is changing with real surface area and therefore with the loading. Tafel Volmer equation.
Comparing different catalysts can however be tricky.What do you really want to compare?
The observed activity is a function of real surface area and specific activity. So when you compare different catalysts you want to compare the specific activity. This quantity might be hard to obtain if you cannot measure the real surface. so instead the mass activity might be a good substitute. To get a proper value you have to measure the activity for a wide range of cat. loadings as you can only claim to have the correct value if the activity is linearly changing with loading. But, keep in mind that different catalysts might have different surface area relative their mass so, comparing mass activity is like comparing apples and oranges.
Why you get a lower diffusion limit current can be because you either have a not fully covered surface or the film is so thick you see membrane effects. Thus, vary the loading to see if this was the issue.
Further, you might have a saturation problem. Thus, ALWAYS measure at different rotation rates and extracting the Levich B factor using a Levich-Koutechy plot. The B factor should be independent of the sample.
Good luck.
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hi I like to study the leaching from my catalyst, I like to run ICP but the problem my catalyst is Heterogeneous catalyst and its insoluble. is there any method to prepare the sample
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Dear G. Abdulkreem Ghassan ALSULTAN
First of all, I am not a doctor. I am just a technician working as chemical analyst ;-)
Secondly, I presume that you would like to measure the amount of certain elements that are washed out from your catalyst during some process you are performing. Am I right?
If yes, then as an extractor, I would use substance that is going though this catalyst during this process to check what is leached from the catalyst. Just make sure that this substance is of high purity to measure what is leached not is in the substance prior to leaching. In this case, I think, crushing and grinding is not necessary as you will simulate the process.
If you want to measure the content of elements in the catalyst. Then you will have to dissolve the catalyst in strong acid(s) (preferably HNO3, HCl or Aqua Regia. In this case you will probably get much higher contents of elements than in previous case.
The method of extraction of elements from catalyst depends on what exactly you want to measure. For example, if you want to measure the most mobile elements, try to run distilled water through the catalyst and see if this has increased the content in water. If you want to check the elemental composition, try digestion with strong acids.
I do not know the details of the process so the above are just my guessing. Hope this help a little.
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how can know the type of active sites of the catalysts as well as the reduction degree ,,if dont have TPD and TPR?? 
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If your catalyst is acidic, then determination of the concentration of Lewis and Brönsted acid sites in the synthesized catalysts was performed by Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy of adsorbed pyridine. 
for the reduction of the catalyst by using TPR
if you want more detail in this paper
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I am doing temperature programmed experiments on sofc electrodes sending a mixture of H2/Ar .I thought that the change in dilution of hydrogen affects the amount of this gas contained in the control volume which includes the catalyst. Therefore, if i send hydrogen with higher dilution, there will be more H2 in my control volume and the peaks will be difficult to highlight. Anyway, the partial pressure of hydrogen also affects the rate of reaction and i want it to be high in order to have an higher intensity peak. Which is an optimal value of hydrogen dilution for my purpose? Does it depend also from the gas residence time? In literature the most used values are from 5 to 10 % of H2/inert. Is there any explaination?
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I apologize for the quality of the Google translator :).
TPR peak represents hydrogen consumption kinetics depending on the temperature rise speed, values of the sample, size of particles , the flow rate and concentration H2.
With an increase in dilution, the greater the value of relative change in concentrations of the same absolute consumption. Thus increasing the sensitivity of the analysis. Increasing the difference in the values of the heat transfer coefficients between the carrier gas and hydrogen also results in an increase of
sensitivity, and therefore typically use H2 / Ar. However, the hydrogen concentration can not be too small, otherwise it may not be enough to restore. That is why the use of 5-10% H2
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Glutathione is an amino acid, hence it exits as a zwitterion. My doubt is whether it acts as acid catalyst or basic catalyst. Please eleborate. 
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Hi there,
Glutathion is actually a tripeptide and according to the state of its thiol group, it may act either as a base or as an acid. 
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I prepared ZnO via thermal decomposition of zinc acetate dihydrate. I evaluated its performance for dye degradation under UV light. It exhibited 42% dye degradation in slurry system. After keeping it in the Lab (temperature of around 30 deg.) for about 2 yrs, it showed 15% performance enhancement under identical experimental conditions. In fact, I unintentionally did this and therefore have no expectation for the result. I speculated that its properties are altered and some characterizations are thus required for elucidation. But, why does its performance change ?    
*I assume the dye properties are unchanged 
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There may be several factors that contribute to the enhanced activity. First of all the ZnO may have altogether different vacancy states when it was synthesized and kept for years. It could easily come across the atmospheric oxygen, moisture and other gases to have some chemistry which can modify the properties easily. Did you check the XPS of the sample just after synthesis and after keeping it for 2  years? That may provide some fruitful information.
The bottom line is that you do not have the same structure anymore, although, you didn't do any chemistry but the nature did some chemistry with your sample. 
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I would plan to make a Doctor Thesis and focused with Heterogeneous catalyst characterization. There are ATR - IR Spectroscopy and XAS should be offered to support the research.
Could anyone help to briefly describe based on experiences, what could we work with the help ATR - IR and XAS for characterizing Heterogeneous Catalyst.
Many thanks for help
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ATR can easily be used  to spectroscopically characterize different types of sample systems. This includes heterogeneous catalysts, electrode-interfaces but also bulk solution phase systems. There is in fact a vast literature on this topic available. Possibly important for you is that different tricks can be empolyed to make ATR advantageous for surface-sensitive spectroscopy, the most prominent thereof is the surface-enhancement effect employing metal-coated surfaces. 
Depending on the particular scientific question that you have, and the system that you want to investigate, you may find some important examples for applications in the following overview articles:
Chem. Soc. Rev., 2010, 39, 4571–4584 (http://pubs.rsc.org/en/content/articlepdf/2010/cs/b919544k)
Chem. Rev. 2012, 112, 2920–2986 (http://pubs.acs.org/doi/pdf/10.1021/cr2002068)
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This is a very complex question, but I really want to know, Is it hard or anything else?
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 Structure changes in relation to catalytic activity is very important  topic and can be examined using some in situ XPS experiments or XRD . Also you can do these analysis befor and after the catalysis to investigate any changes
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This question is initiated by a recently published paper about “recent advances in microcalorimetric studies”. I don’t name the paper title, because I don’t want to compromise its authors and because this is not a unique paper that could initiate such a question. The available literature includes, on frequent occasions, results of microcalorimetric measurements of chemisorption and more complicated gas-surface processes at metal/oxide systems and at other combined systems at different temperatures. Therewith, the gross calorimetric effects are sometimes described with no quantitative differentiation between chemisorption and absorption and processes proceeding at different surface phases or different temperatures. Such measurements are hardly-reproducible and hardly-interpretable. Of course, it is difficult to perform microcalorimetric measurements of any definite process in a complicated gas/solid system. But are calorimetric measurements useful if they are not associated with a specified physicochemical process?  
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Hi Victor,
Interesting question - not sure if I can answer it, but perhaps contribute. Using calorimetry you will get energy signals for both absorption and chemisorption, as you correctly suggest. To quantitatively distinguish which is which, you will need to use a complimentary technique such as surface Raman or FTIR, this will show the formation of chemical bonds or lack thereof, and also show if the bonds are strong enough to be chemical.
If the data is published without additional analyses, interpretation of it can be general at best without specific assignment. It might be possible to distinguish between the absorption and chemisorption by comparing it to known energy signals of similar processes since a stronger signal is expected for chemical reaction.
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hi
I want to study the coke formation on my catalyst for creaking reaction. my problem is my catalyst is Carbon base catalyst any suggested method to determine it?
Kind regards,
Alsultan Abdulkareem
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There are two possible ways to measure these carbon content.  TG-MS: You will firstly measure your fresh catalyst, and then on the basis of this, you can analyze the used catalyst. Comparing these results, you could calculate the content of coke deposition. Other method is a calculating method by GC with a internal standard according to carbon balance.
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Catalyst characterization Recyclability  Reusability Catalyst leaching    How is it possible to calculate catalyst leaching? is it enough to use gravimetric method?
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The method used normally in the leaching tests is related to the nature of the catalyst you are using. if you are using supported metal catalysts and you want to measure the amount of the metal leached during you reaction, you can separate your catalyst at the end of your reaction and conduct an ICP-OES analysis either for the filtrated catalyst or for the reaction solution after the separation of your catalyst. Please notice that if the leached metal in the reaction solution was in nano particle form you might not be able to determine its content in the reaction mixture using direct injection in ICP-OES. In this case you have to dissolve your metal inside the reaction mixture prior to the ICP-OES analysis. In the end you can find some answers for a slimier question in the following link:
hope it is useful.
Regards
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I have prepared an oxide of different structures (e.g. nanocubes, nanobelt, rods, etc.) using different preparation techniques. I want to modify the surface of these materials with silanes. The rate of uptake differs with each structure. Could this variation be due to the different type of surface hydroxyls on the surface of the different structure? if not, what could be the reason?
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The answer to your question is; sure it does.  There is no need to say the production method itself will definitely alter the surface chemistry. Even you have amorphous products/particles with no crystallinity, you have to fix the after production procedure to be sure about the surface chemistry.
Addition to the former comments of our esteemed colleagues:
There are some good articles which clearly points that even different crystal planes has different chemical reactivity. Addition to that synthesis method and plus handling (purification, cleaning and etc.) after the production of the particles can change the surface chemistry.
Best  Regards.
Kerem
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hi
I saw some papers they use N2 to prepare the activated carbon and the other thy use the N2 then they switched it to CO2 but they did not explain about it. 
I want to know the mechanism of CO2 during activation ?
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During heating processes, N2 and CO2 are used for two different things:
  • N2 (or any other inert gas, such as Ar or He) is used to convert the carbonaceous raw material into another more stable and heat resistant compound that consists mainly of carbon (C). Oxygen and hydrogen are largely eliminated, thus leaving a carbonaceous framework with low surface area. This process is named PYROLYSIS.
  • CO2, in contrast, reacts with the carbon (is not inert) at around 800 ºC according to C+CO2 --> 2CO. As you can see, you remove some carbon from the solid, and convert it to CO that goes away in the gas. This process of 'gasification' develops porosity by removing carbon atoms. This is one of the methods to produce active carbon. It is active because it can adsorb a lot due to its great surface area (say, from 100 to 2000 m2/g). This process is named ACTIVATION. You can also do it with other oxidizing agents such as H2O or O2 too.
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 Thermal conductivity of the catalyst necessary for calculating heat transfer effect in oxidative dehydrogenation of alkane to alkene reaction.
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The relationships derived at previous answers allow us to predict the thermal conductivity of some substance of molar formula AxBy after that of its components (A, B). The obtained ‘mixture rule’ averages the contributions of each component for the cube of the thermal conductivity, weighted by the product of their molar volumes by their respective stoichiometric coefficient (x, y), that is to say, weighted by their partial molar volumes if the substance could be considered as ideal solution (possibly solid). Generalization for substances composed from more than two components (e.g. AxByCz) is obvious. Such a mixture rule may perform reasonably for a compact material, but may perform significantly worst for a porous material. I have addressed the subject of predicting the thermal conductivity of a porous material ─ although specifically considering a foam ─ while answering to another question at this forum:  https://www.researchgate.net/post/Is_the_formula_for_thermal_conductivity_of_metal_foam_correct2 
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Do you know mechanism of Rosendmund Reduction Acid halide to aldehyde? How do Pd, BaSO4 , Quinoline function in this reaction?
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