Hoang Dang Lanh

Leibniz Institute for Catalysis

The hydrothermal crystallization of SAPO-5 molecular sieves with Si mole ratios in the range of 0.05 to 0.13 was performed by either conventional or microwave heating to compare the influence of these two techniques on the isomorphous substitution of phosphorus by silicon atoms in the aluminophosphate framework. An extensive characterization of the...

Ni/HZSM-5 catalysts for the hydrodeoxygenation of bio-oil were modified with Cu and Co. A first test series with phenol as a model revealed that the presence of Ni is essential for high activity. However, modification with Cu deteriorated the catalytic performance significantly whereas an admixture of Co increased the activity and selectivity towar...

This work deals with the synthesis of perovskite-like catalyst precursors (LaNi1-xCuxO3 with x = 0, 0.2, 0.5, 0.8, 1). These precursors were used to catalyse the dry reforming of methane (DRM) reaction carried out at 973 K, CH4/CO2 = 1 and a GHSV = 18,000 ml/g/h. The precursors were transformed during the course of the reaction to give Ni-Cu/La2O3...

The substitution of harmful phosgene or chloride-containing catalysts in the synthesis of dimethyl carbonate (DMC) and its use as “green solvent” or polycarbonate building block direct its manufacture towards environmental benign syntheses. Thus, copper was introduced into silicoaluminophosphate structure SAPO-37 (belonging to the same FAU structur...

In this study, ternary perovskite type oxides LaNixCu1-xO3 (x = 0, 0.2, 0.5, 0.8, 1) were synthesized using NaOH and diethylenetriaminepentaacetic acid (H5DTPA). The catalysts resulting from perovskite precursors exhibit catalytic activities for CO2 reforming of CH4 at 700 °C that increase with a higher Ni content. Characterization methods showed t...

Reducibility of Cu supported on AlâOâ, zeolite Y and silicoaluminophosphate SAPO-5 has been investigated in dependence on the Cu content using a method combining conventional temperature programmed reduction (TPR) by hydrogen with reoxidation in NâO followed by a second the so-called surface-TPR (s-TPR). The method enables discrimination and a quan...

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Chromia–lanthana–zirconia catalysts prepared by wet impregnation and microwave plasma enhanced chemical vapour deposition methods have been characterized by temperature-programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS). The impregnation procedure requires large amounts of solvent and calcination at high temperatures producing Cr...

Alumina and zirconia supported Pt and Pt–Sn catalysts have been tested in the dehydrocyclization (DHC) of n-octane at 823K to alkylaromatics as desired products using pure hydrogen (H2) and water vapour containing hydrogen (WVH2) atmospheres. The materials were characterized by nitrogen adsorption, NH3-TPD, TPR, XRD, XPS, TEM and EDX. The character...

Lanthana–zirconia supported chromium oxide and magnesium chromium mixed oxide catalysts were studied in the dehydrocyclization of n-octane and characterized by temperature-programmed desorption of NH3, temperature-programmed reduction, XPS and DRIFTS. The Mg-free catalyst shows the highest activity, but suffers from rapid deactivation due to coke f...

CrOx/La2O3 mixed oxides, prepared by impregnating La2O3 with appropriate aqueous solutions of (NH4)(2)CrO4 and calcining at 600 degreesC for 4 h, have been investigated by means of XRD, TPR, XPS, DRIFTS, and Raman spectroscopy (RS). The formation of the compounds La2CrO6, La(OH)CrO4 and LaCrO4 under these conditions was evidenced. Strong peaks at 8...

The redox behaviour of chromium oxide in CrOx/La2O3, CrOx/La2O3/ZrO2 and CrOx/ZrO2 mixed oxide systems has been investigated by temperature-programmed reduction (TPR), photoelectron spectroscopy (XPS) and Raman spectroscopy (RS). The formation of La-Cr compounds such as La2CrO6, LaCrO4 was shown to occur by calcination of CrOx/La2O3 and CrOx/La2O3/...

In situ tracer experiments with n-octane aromatization on Cr2O3/La2O3/ZrO2 catalysts allowed conclusions on the deactivation mechanism. Coke as the main source of deactivation acts by poisoning active sites rather than by lowering mass transport rates.

This chapter discusses the acidic properties of EMT- and FAU-type zeolites and their intergrowths with similar aluminium (Al) content, which contain the same structural subunits but differ in stacking. These properties have been studied by different physico-chemical methods. Small fine-structure differences have been found that might be the origin...

Nanocrystalline particles of high temperature pretreated titania, zirconia or hafnium oxide, embedded in a carbon matrix, have been found to catalyze the aromatization of n-octane into ethylbenzene (EB) and o-xylene (OX) with high selectivity. The carbon matrix itself is catalytically not active, but seems to co-operate with the transition metal ox...

Chromia supported on zirconia is an interesting catalyst system for a wide range of catalytic reactions, with dehydrogenation of lower olefines or dehydrocyclization of C6+ paraffines being examples of reactions of industrial relevance [1-3]. The activity of supported chromia catalysts in these reactions is influenced by the oxidation state of chro...

Infrared spectroscopy of the adsorbed probe molecules CO, NO, and NH3, photoelectron spectroscopy, temperature-programmed desorption of NH3, X-ray diffraction, and BET surface analysis have been used to study surface and bulk characteristics of lanthana-modified CrOx/ZrO2 catalysts. La2O3 addition to CrOx/ZrO2 strongly modifies the structure of sup...

Temperature-programmed reduction (TPR) has been applied to study the reduction behavior of chromium oxide supported on pure zirconia and on lanthana-containing zirconia. The results revealed influences of support nature and chromium loading on the state of the supported chromium oxide. With catalysts containing lanthana and only low amounts of chro...

A new aromatization catalyst, composed of nanocrystalline transition metal oxide particles, e.g., zirconia, titania, hafnium oxide, embedded in a matrix of amorphous carbon was developed. Bulk and surface properties of the new materials was studied by spectroscopic methods. Aromatization increased the octane number of gasoline range hydrocarbons. T...

Supported chromium oxide catalysts containing 0.5 and 4.0 wt% Cr, respectively, on a 7 wt% La2O3/ZrO2 carrier were studied by in situ EPR equipped with on-line GC during the catalyst pretreatment in flowing H2 and the aromatization of n-octane in the range 293<T<823 K. Active catalysts contain almost exclusively Cr3+ in the form of Cr2O3 clusters a...

High surface area materials composed of microcrystalline zirconia and amorphous carbon have been prepared by a sol–gel method, followed by a high temperature treatment of the resulting xerogel in inert gas. These composites have been characterized and tested in the dehydrocyclization of n-hexane and of n-octane at 550°C. They turned out to be highl...

CrOx/La2O3/ZrO2 can convert n-octane, as a representative C6+ paraffin, almost exclusively into ethylbenzene and o-xylene. This system was studied in n-octane conversion in terms of several aspects such as the nature of catalyst deactivation. CrOx/La2O3/ZrO2 was selective for n-C6+ paraffin aromatization. The catalyst system is non-acid and, thus,...

The interaction of hydrogen with ZrO2 at high temperatures (673–873 K) has been studied by using in situ FTIR spectroscopy. OH species are formed with O—H stretching frequencies at 3650 cm–1 on the surface of monoclinic and at 3730 cm–1 on the surface of tetragonal zirconia. The role of these hydroxy groups in the mechanism of hydrogen uptake and d...

A Pt/ZrO2 catalyst has been investigated by temperature-programmed reduction and temperature-programmed desorption of hydrogen. Hydrogen spills over from Pt onto the ZrO2 surface at about 550°C. One part of spillover hydrogen is consumed by a partial reduction of zirconia. The other part is adsorbed on the surface and is desorbed at about 650°C. Th...

The acid properties of an HZSM-20 Zeolite have been characterized, in comparison to an Hy Zeolite, by IR spectroscopy, temperature-programmed desorption (TPD) of ammonia, time-resolved temperature-programmed FTIR of ammonia desorption and by microcalorimetry. Also, catalytic properties were tested for n-hexane conversion. These studies show that fo...

Nickel containing H-ZSM-5 catalysts were prepared by impregnation with nickel nitrate at pH 1.8 and 4.8. The catalysts were characterized by infrared spectroscopy of adsorbed carbon monoxide and ammonia, by temperature-programmed reduction as well as by chemisorption of hydrogen and oxygen. The conversion of n-hexane served as a catalytic test reac...

ZrO2 and Pt/ZrO2 catalysts have been investigated by TPR, hydrogen chemisorption, TPDH and in the conversion ofn-hexane. At high temperature, ZrO2 takes up hydrogen. High temperature hydrogen treatment is a precondition of the catalytic activity in then-hexane conversion. Possibly, catalytically active acid sites are formed by this hydrogen treatme...

H-ZSM-5 · Al2O3 catalysts were prepared by mixing and calcining H-ZSM-5 and AlO(OH). Catalytic, TPD and IR studies indicate the following influences of Al2O3 on the zeolite. The activities in the conversion of n-hexane and mesitylene are enhanced, the selectivity for the isomerization of mesitylene is increased, the Brönsted acidity is decreased, t...

Various gallosilicates having an MFI structure, [H-(Ga)ZSM-5], with controlled content of nonframework and framework gallium were hydrothermally synthesized from gels of the following composition: 15 Na2O· x Ga2O3·100 SiO2·13 TPABr·4400 H2O. Varying the synthesis times revealed that at nearly unchanged total Si/Ga ratio the catalytic activity in th...

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The crystallization of Ga-ZSM-5 zeolites and the incorporation of gallium into the framework were investigated by means of TG-DTA measurements. Special attention was paid to the decomposition of the embedded template, which was followed by the observation of coke formed in particular on the external surface of the crystals. A semiquantitative relat...

Alumina-supported Ni catalysts, containing Sb, Pb, or Cu as a second metal (termed here the “bimetal”), were studied in the conversion of cyclohexane. Activity and selectivity strongly depend on the reaction conditions as well as on the composition and the pretreatment of the catalysts. Each of the three second metals caused very similar positive e...

Pt−Ni/γ-Al2O3 catalysts have been prepared and studied in n-hexane dehydrocyclization. The selectivity for benzene and toluene, a chain lengthening product formation was improved by Ni and correlated with its content.

Ni/γ-Al2O3 catalysts containing 5-30 wt.% Ni have been prepared and calcined at various temp. (400-600 °C, 4 h, air).

Verschiedene Ni/γ-Al2O3-Katalysatoren wurden hergestellt, indem der Ni-Gehalt und die Temperatur der thermischen Vorbehandlung verändert wurden. Mit diesen Proben wurden Messungen zur temperaturprogrammierten Reduktion und zur Umwandlung von Cyclohexan durchgeführt. Beim Calcinieren entstehen zwei Formen des NiO, bulk-NiO und schwerreduzierbares, „...

Bimetallic catalysts Pt-M/AlâOâ and Ni-M/AlâOâ (M = Sn, Sb, Bi, Pb) are discussed. It is shown that the influence of the second metal on the activity and selectivity of the catalyst depends on the nature of the metal-metal and metal-carrier interactions. Depending on the experimental conditions, the bimetallic effect is positive or negative with re...

The addition of Sb to Pt/A1203 inhibits the conversion of cyclohexane under non-destructive conditions at about 300°. But under destructive conditions at temperatures of 450 to 500° bimetallic catalysts, containing 1 - 2 atoms Sb per atom Pt,are more stable and form more benzene than the monometallic Pt/A1203 catalyst. More-over the addition of Sb...

The conversion of n-hexane was studied on a Pt-Sn/Al2O3 catalyst, a PtSn alloy and on the corresponding Pt catalysts. The results indicate the same catalytic effect of tin in supported and unsupported catalysts. It is concluded that the role of tin is connected with alloy formation.

Ni/..gamma..-AlâOâ catalysts have a very strong dehydrogenation function; however, they also show strong hydrogenolysis activity. The addition of inactive metal such as Cu or Sn inhibits the hydrogenolysis activity, but improves the hydrogenation selectivity of Ni/..gamma..-AlâOâ. In several cases, reforming properties of modified catalysts have al...