Catalyst Synthesis - Science topic

Ghada Aljaber Thank you for your question. This is relatively simple to answer with a grasp of chemistry but does need some care with the calculations.

So, you want to end with 3wt% Co in NiFe₂O₄ – that is, 0.03 g Co plus 0.97 g NiFe₂O₄ for a gram of final material. OK, so how do we get there? Consider NiFe₂O₄ as an equal ‘mix’ of NiO plus Fe₂O₃. Let’s consider getting to a gram of the doped material as then if we want to make more then we simply have to multiply the amounts of the starting [precursors by the appropriate factor.

The MW of the precursors and the decomposition route are key:

• Fe(NO₃)₃.9H₂O MW 403.999 g/mol gives rise to Fe₂O₃ (MW 159.6882 g/mol) on decomposition. We note that we’d need 2 moles of the nonahydrate to give rise to 1 mole of the oxide

• Ni(NO₃)₂.6H₂O MW 290.79 g/mol gives rise to NiO (MW 74.6928 g/mol) on decomposition

• Co(NO₃)₂·6H₂O MW 291.03 g/mol gives rise to CoO (MW 74.93 g/mol) on decomposition. You’re specifying Co (atomic mass 58.93) not CoO

• NiFe₂O₄ MW 234.381 g/mol. In 1 g of this material, we’d have 159.6882/234.381 g of Fe₂O₃ and 74.6928/234.381 g of NiO. For 0.97 g of NiFe₂O₄ we’d need 0.97*(159.6882/234.381) g of Fe₂O₃ and 0.97*(74.6928/234.381) g of NiO

Let’s start with the dopant (Co) first. To get 0.03 g of cobalt would require 0.03*(74.93/58.93) g of CoO which would be produced from a multiplier of (291.03/74.93) g of the hexanitrate. Thus, we’d need 0.03*(74.93/58.93)*(291.03/74.93) g of the precursor hexanitrate to lead to 0.03 g of Co

Now, the iron nonahydrate. (2 X 403.999) of this gives rise to 159.6882 g of Fe₂O₃, so we need (2 X 403.999)/159.6882 g of the nonahydrate to give rise to 1 g Fe₂O₃. We actually require 0.97*(159.6882/234.381) g of Fe2O3 equivalent in the final product. So our starting nonahydrate would be 0.97*(159.6882/234.381)*[(2*403.999)/159.6882] g of this precursor

By a similar argument, for the NiO equivalent, then to get 0.97*(74.6928/234.381) g of NiO requires a multiplier of (290.79/74.6928) of the hexahydrate. That is (290.79/74.6928)*0.97*(74.6928/234.381) of the nickel nitrate hexahydrate for a gram of the final NiFe₂O₄.

You need to check my math and that I haven’t made a typo (or several typos) and also that I have the molecular masses of the compounds correct. I’ll leave you to multiply out the final values and check that they’ll make 1 g of final material. For larger amounts you can multiply by the appropriate factor, as I said earlier.

The production of core-shell nanomaterials presents several technological challenges, some of which include:

My experience with core-shell nanomaterials has primarily been in the area of nanocatalysis, where core-shell nanoparticles are used as catalysts in a variety of chemical reactions. In my experience, controlling the size, shape, and composition of the core and shell is critical for achieving high catalytic activity and selectivity. Additionally, ensuring the stability and durability of the nanoparticles is important for maintaining their performance over multiple catalytic cycles.

In terms of economic viability, finding ways to scale up the production of core-shell nanoparticles while maintaining their quality and performance is a major challenge. This often requires the development of new synthesis methods that are cost-effective and scalable, without compromising on the precision and control needed to produce high-quality core-shell nanomaterials.

Overall, the production of core-shell nanomaterials presents several technological challenges, ranging from controlling the morphology and achieving synthesis precision, to ensuring stability and durability and addressing economic viability. Overcoming these challenges will be critical for the widespread adoption and application of core-shell nanomaterials in various fields, including catalysis, energy storage, and biomedicine.

Yuxi Xu I really appreciate you clearing up the confusion.

You will be able to control the temperature precisely, if a heating coil connected to a Variac (Dimmerstat) is wound around the reaction flask. By varying the voltage the temperature can be maintained at 300C similar to an oil bath.

I would like to suggest you two publications. I hope you will find date for your research.

Also check please the following useful link: https://link.springer.com/content/pdf/10.1007%2F978-1-4684-2796-7_17.pdf

It may be helpful

Dear Ayoub Najem many thanks for sharing this very interesting technical question with the RG community. Flavonoids normally have several –OH groups at different positions, so that a variety of fluorinated derivatives are possible. There are some literature references available in which the authors describe the use of elemental fluorine (diluted with nitrogen) as fluorinating agent. However, most organic chemistry laboratories are not properly equipped for woorking with elemental fluorine.

An alternative synthetic route involves the synthesis of fluorinated flavonoids starting from fluorinated benzene derivatives. For more information, please have a look at the following potentially useful articles:

and

The first article is freely available as public full text from the internet (please see the attached pdf file). The second article has not been posted as public full text on RG. However, one of the authors has an RG pprofile (https://www.researchgate.net/profile/Suh-Cho-2). Thus you can easily contact him directly via RG and request the full text.

I also came across a Master thesis which could provide useful information about this topic:

(also attached)

Good luck with your research and best wishes, Frank Edelmann

P.S. Please also share this question with the "flavonoid guru" Yasser Fakri Mustafa

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

Also check..

Dear Steve

following the prior comments. There is not definite answer to such a question - a fundamental question. Essential will be the objective of your work.

Do you want "just" find a catalyst that works well?

Do you want to understand how the reaction you are studying functions on a specific catalyst or group of catalysts?

Which feature of the catalyst are you interested in: atomic structure, micro-structure, etc.?

Knowing the answer to these questions may guide you to the methods you need for your work.

With respect to the two general approaches that you were raising: Theory vs. Experiments. I would like to handwavy point out some general issues.

Both approaches can be enormously time-consuming so there is no clear advantage of one over the other.

For theory, you got the essential issue, that you have to hypothesize some sort of structure beforehand. In your case, you could say: "I want to look at Ni-X(111) alloy (X = metal) surfaces." Then you may be able to predict which of the alloys has some advantage over the other. However, your synthesized catalyst will not be a pure Ni-X(111) surface, it will be a plethora of structures (metals, metal-oxide interfaces, nanostructures ...). So whatever you are predicting has the risk to be irrelevant for the catalysis. Same goes for the reaction mechanism, that you have to hypothesize beforehand. Yet, theory is extremely informative if it is used correctly, but this is not easy.

If you go down the experimental route, you face the same problem from another direction. Obviously your catalytic activity measurements will tell you which of the catalysts you are test is e.g. performing the best. However, your catalyst will be so complex and dynamic under reaction conditions that is hard to decipher what is the cause of the enhanced activity.

So there is no clear answer to this. However, in my opinion, essential to whatever you do is to read the literature in great detail. Look into work which was done decades ago as well as into the recent literature. This is by far the most time efficient way to understand what works and what not and what the scientific community is not understanding.

Maybe this helps, at least it helped me a lot.

Cheers, Arik

Dear Jundao Wu I assume that the carbon disulfide formed during the reaction will stay gaseous under the given reaction conditions. It will then be identified together with the other gases present in the mixture. Did you check the Supplementary Material provided with the article? It contains some useful details about the gas chromatography configuration. For your information please find attached a pdf file. Good luck with your experiments and best wishes!

Based on my experience, when Cu is introduced by the wet impregnation, the solvent elimination using filtration is not sufficient for some supports. However, the rotary evaporator might be used instead. I have also observed the change in color, however, it did not affect the properties of the calcined catalyst.

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.

Dear Chinnaraja Eswaran I checked that link but It doesn't related to my question.

Dear Sina Safavi thank you for initiating this interesting RG discussion. Although we are inorganic chemists, I'm not an expert in this field. However, I agree with Yurii V Geletii in that there is no such thing as a true catalyst. In this context I suggest that you have a look at the following relevant article which has been published Open Access. It is stated there that future catalysts should be "low-cost and earth-abundant":

(see attached pdf file)

Dear Latif Ullah thank you for your very interesting technical question. Although I'm an inorganic chemist, I would not call myself a proven expert in this field of research. However, I found the following potentially useful reference which might help answering your question:

This paper is freely available as public full text on RG. It is a review article and should provide you with a good initial overview of the field. Moreover, it contains a list of 226 references to original research articles in the field.

Hello Mr.Grice

Some good leaving groups like tosylate ,tms ,.. are good.(base on reported works)

But halids are relatively inert in some reactions .

Use of I as leaving group in allylic position is a Conventional method but problem is cost.

Nucleophilc replacement of NO3/X since Hughes & Ingold is Well known but other cations participation or catalysis is unkown...

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.

Dear Anas Abdullah

As Professor Frank T. Edelmann has mentioned, The CAS number is 123-31-9

All the best

Dear Noor Aljammal

De diffusivity of the reactive specie depends of the solvent (nussel Difusivity) and the catalyst contribute with the effective diffusivity according the porosity and tortuosity.

Please read my article: La-, Mn-and Fe-Doped Zirconia Washcoats Deposited on Monolithic Reactors via Sol-Gel Method: Characterization and Evaluation of their Mass Transfer Phenomena and Kinetics in Trichloroethylene Combustion 2017International Journal of Chemical Reactor Engineering

15(5),20170027, where I calculated both types of diffusivities.

The heat transfer is analogous.

Hi,

Sabatier reaction is a catalytic method for conversion of CO2 to CH4 by the definition. A very wide catalytic system is available to operate this transformation. A review of the materials and their performances has been presented together with some industrial applications in the following link.

However, if you mean catalyst-free conversion of CO2 to methane gas, as far as I know, there is no feasible method for that and if there is any, it would probably need very high temperatures.

@Jay Soni

After your reaction completion u have to centrifuged ur reaction mixture at 15000 rpm for 5 min and remove organic compounds. and wash GO by 5 times with certain solvent and take out all ur reaction mixture. Finally drie GO at 100 degree temp. for certain hr. it is ready for further use.

Yes, Halima, but the question was how po prepare Ultrastable zeolite Y. For the increase the stability of Y-zeolite to the level "Ultrastable" its structure must be quite strongly dealuminated, by wery low acid concentration it can be prepared only H-form of Y-zeolite with very small dealumination, and, as you mentioned, it is necessary to calcine it very carefully to keep the crystallinity. Ultrastable Y-zeolite must by prepared by hydrothermal treatment at the temperatures above 500 °C - at this condition a hydrolysis of framework aluminumum occurs creating extra-framework Al-species (EFAL), and Al-vacancies in framework are partially replaced by Si-atoms. Then, EFAL species could be partially extracted by mineral acid - its concentration can be even higher, because after hydrothermal dealumination in e.g. deep-bed conditions at 550-750 °C the dealuminated structure of USY is strong enough to be stable against acid treatment. There are also another methods how to dealuminate the structure of Y-zeolite - slow extraction by H4EDTA-acid, but the hydrothermal steaming is the most used method for the prepartation of Ultrastable Y-zeolite. Method you propose is suitable for H-form of Y-zeolite preparation, but without higher stability.

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.

Thank you, I have tried washing the carbon powder with water, acetone and ethanol followed by vacuum oven drying hoping these will screen out the impurities but they still exist.

In my experience, it is difficult to absolutely remove ionic CTAB by hot EtOH. Because of good solubility of CTAB in water, I think hot water could be chosen. For removal of P-123 and F-127, my senior have ever used refluxing EthOH in Soxhlet extractor.

Miroslaw,

I think of fouling as a blockages that cause maldistribution. A burn will sometimes remove a blockage (e.g. if it is coke blocking a pore) but sometimes it will not and dumping and reloading catalyst is often necessary, especially if he blockage is caused by scale/metals instead of hydocarbons.

Coking/carbon disposition is the most common way for commercial Hydrotreating, Catalytic Cracking and Hydrocracking catalyst to lose actiity. Historically these catalyst were :regenerated" with a burn but recently the trend has been to dump catalyst and send it to an offsite regeneration facitity for screnning and coke burning. Arsenic and lead are posons that will permanently deactivate most catalyst and cause them to be unregenerable via burn.

I think of an inhibitor as a material that competes with reactant for catalyst sites inhibition is reversable. If the inhibitor is removed from the feed the rate of the desired reaction will increase. An inhibitor may also increase the rate of coking. If the calayst site is coked up it will usually require a burn(with air or O2) to remove the coke. that has closed up catalysyt pores and/or blocked active sites

.

Poisoning and coking are forms of catalyst deactivation that usually require a stoppage either for regeneration or catalyst replacement.You seem to disagree with the comment it can sometimesbe removed during a regeneration (usually a burn with air or O2). I agree it is not really a "poison" if you can remove it with air/ burn.

All catalyst can be "regenerated" if you take extreme enough measures.

For my purposes - in the refining indusrty- catalyst is not regenerable if activity can not be recovered with a simple burn or other relatively minor procedures like a wash with a solvent.

However even then the active metals can be reclamed and used to make new catalyst.

You can make measurements of FTIR using adsorption of pyridine.

Parry, E.P.

An infrared study of pyridine adsorbed on acidic solids. Characterization of surface acidity

(1963) Journal of Catalysis, 2 (5), pp. 371-379

Electrochemical preparation of PbO2 is well-known , you can use it to get a thick plate that can be crushed into the desired particle size

You might try a different solvent system for your chromatography.  Based on how little EtOAc composition you have, I would suggest a hexane / DCM system.  I've used this solvent system for very nonpolar separations with good success.  Try testing different compositions by TLC first to see if this will work.  You should easily be able to visualize the dba impurity by a DNP stain.  Hope this helps.

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.

Hi Hai Hoang Truong

The product selectivity of CO₂ photoreductions generally depends on the type of metal co-catalyst you put on the surface of your photocatalyst (most photocatalysts generally have poor activities for CO₂ photoreduction in the absence of a co-catalyst).

As a rule of thumb, for CO₂ photoreduction in aqueous media, Ag and Au co-catalysts will yield CO, and Cu, Pt and Ni co-catalysts will yield CH₄. This selectivity pattern results from the very weak adsorption energies of CO on Ag and Au, meaning CO desorbs before it can be hydrogenated to CH₄. The band edges of the photocatalyst and the reaction conditions also influence the product distribution of CO₂ photoreduction.

I suggest that you consult the primary literature around the particular photocatalyst system(s) your are working on, and use that information as a framework for predicting the products of your photoreductions.

Best regards

Geoff

Activated carbon is a versatile adsorbent, hence, it can be used for decolorization purpose. Generally, preparation of AC is inexpensive, therefore it is one of the most used adsorbent for removal of different pollutants. However, the choice of your activation source may play a major role in terms of cost effectiveness. Here, is a simple procedure for obtaining activated carbon. First dry the husk, put it in a close contained n carbonized in an muffel furnace at 800 degree Celsius for 2-3 hours (you may vary the temperature of your choice from 400-1000 as per your requirement), ground the carbon into a fine powder (you can use planetary ball mill to obtain fine uniform particle size). After, which you can activate the carbon either with oxidizing or reducing agent. For instance, if you are using Nitric acid as your activating agent, then added the fine carbon powder (10-15 g) in a beaker, and add 0.01 M Nitric acid solution into the beaker slowly until the carbon is fully submerged and stirred it for 2 hours. Filter, wash with DW to remove excess of acid and dry the product, keep it in an air container for further analysis.  

There is no acidic aluminum oxide. Aluminum oxide has amphoteric properties. It reacts with both acids and bases. Selective monoestherification of dicarboxylic acids should be done in an alkaline medium. Then the alumina will exhibit acidic properties.

yes you can do the kinetric study of zeolites , by changing the conditions of molar ratio of Si/Al; the concentration of template , the concentration of sodium, the sources of the  reagents , the temperature , the duration , ect )  , this kinetic will be followed by XDR analysis  each time ( you have to estimate the timing , may  be  each two hours , or each day ect 

Dear Pratheek,

Example –1Turnover Frequency in Fischer–Tropsch Synthesis

CO   +  3H = 2 CH 4 +     H 2 O

The Fischer–Tropsch synthesis was studied using a commercial 0.5 wt % Ru on  -Al 2 O 3 . The catalyst dispersion percentage of atoms exposed, determined fromhydrogen chemisorption, was found to be 49%.At a pressure of 988 kPa and a tem-perature of 475 K, a turnover frequency, , of 0.044 s  l  was reported for methane.What is the rate of formation of methane, , in mol/s  g of catalyst (metal plus sup-port)?

See this file

Hi Hussein Al-Wadhaf,

You can determine the number of active site of deposited metals by H₂-pulse chemisorption measurements, and their strength by further H₂-TPD analysis; both analysis can be performed in sequence. Although H₂ is the most applied probe, it can be replaced by other probe molecules such as CO and NO. The choice of which probe to use depends on the adsorption mechanism, I know that the use of H₂ to determine active sites on nobel metals like Ru and Os works well. However I believe that CO is a better probe molecule for Pd. I did a quick check and it seems that H₂ embrittle Pd. I have included here links that might help in your studies.

Best Regards,

Alexandre.

About this question i found this article

The decrease in rigidity while maintaining the performance (or higher performance) may have been due to variations in the pore structure, in particular the increase in the porosity of the adsorbent particle and increase in specific surface.

Regards,

There are different reactive sides in the two reactions

the it is difficult to precise the reactions products

But I think that they can produce 1,2,3-triazoe and thiazolone respectively 

 The pH of the reaction mixture should be maintained at a value of 10 or 11 to stabilize the zeolite precursors formed and avoid going to polymerization

One of the advantages of Zeolites is the turnability of the pore structure. As Afol mentioned, the first step is to de-aluminate to increase the silica/alumina ratio. That will also enhance the acidity, porosity as well as surface area. You can check my article on zeolite modification "Synthesis and application of hierarchical mesoporous HZSM-5 for biodiesel production from shea butter"; de-alumination of kaolin "Synthesis of hierarchical nanoporous HY zeolites from activated kaolin, a central composite design optimization study", "Synthesis and characterization of hierarchical nanoporous HY zeolites from acid‐activated kaolin", "Kaolinite properties and advances for solid acid and basic catalyst synthesis" and "Synthesis and characterization of sulfated hierarchical nanoporous Faujasite zeolite for efficient transesterification of shea butter". The article titled "Insight into catalyst deactivation mechanism and suppression techniques in thermocatalytic deoxygenation of bio-oil over zeolites". Kaolin is a mineral clay with almost the same components as raw zeolites. 

Thank you Tariq Aqeel

A simple hydrothermal process for fabrication of hematite (α-Fe2O3) nanostructures with narrow size distribution was developed by using PVP as surfactant and NaAc as precipitation agent. 

The present study is to synthesize iron oxide nanoparticles on different polysaccharide templates calcined at controlled temperature

Best regards.

Thank you Dr. Mirgorod. I think this clears my question of complete degradation of methyl orange in presence of borohydride and gold at first and then the reduction in degradation efficiency.

It looks like thin graphite flakes. XRD and/or Raman will tell you more about the nature of the carbon.

Alain

 I highly recommend you to read this technical report (MANUAL OF METHODS AND PROCEDURES FOR CATALYST CHARACTERIZATION) by  J. HABER et a., 1995

1 ppm means 1 mg in 1000 mL.

For 500 ppm add 500 mg (0.5 gm) of Rh5 in 1000 mL.

This would be a standard question for someone starting in chemistry (and thus there is no reference as it's 'obvious' to someone skilled in the art), so obviously you are not a chemist, but your information is incomplete to answer it  You do not state the form of the precursor 'cerium nitrate'.  You finish with CeO₂ (cerium in the +4 oxidation state).  The most common nitrate of cerium is the hexahydrate [Ce(NO₃)₃.6H₂O] and this is Ce in the +3 oxidation state - other nitrates are, of course, known - hydrated and unhydrated and Ce in various oxidation states.  However, this can be taken as a pertinent example.  The molecular mass of the Ce (+3) nitrate hexahydrate is 434.22. The molecular mass of CeO₂ is 172.115.  So 434.22 g of the hexahydrate will lead to 172.115 g of CeO₂ (100% yield). So if you start with 1 mg of the nitrate you'll end up with 172.115/434.22 mg of the oxide. This is around 0.4 mg (0.396 is more pedantic).  So the chemistry of your starting material is crucial.  You ask 'how much?'  I think in terms of nanoparticles then the question should be 'how many?'  You would need then to calculate how many NP's of say 50 nm would be produced from (say) 0.4 mg of the oxide.  This should be an easy question for you to answer with a knowledge of the density of the CeO₂ and some assumption about the finished shape of particle.

thanks a lot for your attentions 

H₂O₂ has acidic character. So it should be more stable in acidic medium.

For such a small size centrifugal separation might be more appropriate. If you can get a clear liquid layer by filtering or centrifugation the method can be used. Centrifuge to excess has risk of removing adsorbed pure component from catalyst.

Nano filtration can go as low as 150 molecular weight.  Ultra filtration can go to about 3000 molecular weight. Microfiltration is limited at about 50,000 molecular weight.

If the pure component is a much smaller molecule than the effective catalyst size, then filtration is preferred and only a small amount of clear liquid is needed.

If catalyst and pure component are about the same size but different densities, mild centrifugation might be possible.

Dear Tatiana Zanette,

It would be necessary depending on which method you do use to the silver reduction. If you will use a chemical method I strongly recommend protect the solution from the light. This is due tath the light reduce the Ag⁺ ions. I'm not an expert on your field but it is repported the use of ambiental light to reduce silver ion and coat nanoparticles (i.e. doi:10.1021/la035330m). Then you could use the light to reduce the silver ions. I would expect different reaction rates and mechanism of nanoparticles coating or formation if you will use a chemical and thermal reduction or if you will use ambient or even monochromatic light.

So it is an important factor to take in account on any synthesis. When in our lab we use silver salts to synthesis we always protect the reactives (silver salts) and reaction solution from the light. I hope this information would be useful. Regards.

Juan

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.

thank you very much Dr Coker. This explanation remarkably help to me. Thank you again. 

thank you very much

Dear Saeed Golmohamadi, 

I suggest to read the following papers.In case you need the full papers  you can request.

Best regards.

Hi

I think firstly, you need to prepare a good surface area, large pore volume and highly acidic alumina support. Please find the attached paper that discuss the preparation of different phases of alumina

Best regards

Hi

I think the attached paper is a good one to differentiate between different phases of alumina

Thaks

Dear Venkata Chandra Sekhar Palla, 

Si/Al ratio and SiO2/Al2O3 ratio are the same for zeolites, or no?

I though that Si/Al is a short name of SiO2/Al2O3.

Hi

you can use DRIFTS-Pyridine to distinguish between different acidic sites as Bronsted or Lewis and TPD-CO2 for basic sites

Have a very good day

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 2^nd order or higher in catalyst, while the desired reaction is usually 1^st 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...

you have to subject your oil with high FFA to acid esterification prior base transesterification  to avoid soap formation

It depends too much on the system, as sometimes the crystallization occurs on cooling down a solution (cooling down makes the solution become supersaturated), but in solvothermal synthesis anything can happen and I've seen with my eyes crystals growing during heating. 

If your phosphate gets dissolved at 180°C it makes sense to cool down slowly, because new nucleation has to occur and you want only few nuclei, and to grow them slowly.

But if they keep it for 1 week I suppose it stays as a suspension therefore you're trying to improve the crystals you already have, growing them bigger at the expenses of the small ones and/or more ordered.... in this case the cooling rate matters less I think.

Just for fun put 2 autoclaves in the oven, program for slow cooling, but take 1 out after the heating time...

DISCLAIMER: I have no experience with what you're trying to do, I just found the question interesting and sharing my thoughts. I might as well be wrong.

I am not 100% sure about your question. But I can provide some information. As I understand, CO pulse titration can only do "surface" Pt, not bulk Pt. If you'd like to know total (bulk) numbers of Pt, ICP and AAS would work. If you just want to estimate this value, you can calculate your Pt dispersion first, then use a curve ( G. Ertl, H., Handbook of Heterogeneous Catalysis, pp740-741) to roughly obtain your total Pt numbers.

By the way, I have noticed that you used activated carbon (AC) as support. You'd better check the acidity of AC first.

 Dear Rafik,

Thank you for your answer. In the presence of activated carbon, NVP would hydrolyze into pyrrolidone and acetaldehyde and so the purity decreases ultimately. I think the ppm impurities are amine type!

I would appreciate if anyone could help me. Thank you.

You can use both wet and dry impregnation and use of carbonate and nitrate salts are better than chloride salts.

Hi - I guess you are learning to work with nickel- the answer of course is that it's quite easy. If you need any advice for coordination chemistry; the tricks the professions use then just ask, best wishes, Ian.

 Thanks very much for the assistance.

If a significant amount of dopants are introduced into the oxide during synthesis, it will create doping state, even doping band in the gap, which usually reduced the band gap of oxide. 

Yes you can, if the acidity and the surface area are the same, as I think both of them should be mesoporous . It also depend on the reaction 

if you want more information about the phases of alumina, you can find it in this article

http://www.sciencedirect.com/science/article/pii/S0926337312003918 

Efficient catalysts can be prepared by impregnation of alumina with Ca and Znsalts and further calcination, if low percentages of calcium and zinc are used. See for example

Particuology Volume 8, Issue 3, June 2010, Pages 225–230

The following steps is to estimate the weight of metal in compound:

1- Calculate moles of Co(NO₃)₂.6H₂O= Wt. of Co(NO₃)₂.6H₂O/Mwt. of Co(NO₃)₂.6H₂O.

2- 1 mole of Cobalt(II) Nitrate Hexahydrate = 1 mole of Cobalt.

3- Number of moles in step one = number of moles of Co metal

4- weight of Co metal = step 3 * Mwt. of Co.

Now, you should follow the same steps with your support to estimate the weight of its metal.

After that, Wt.% = [step 4 / (Step 4 + Wt. of support metal)] * 100

Hopefully, my answer will be useful.

Cheers