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Showing papers on "Dehydrogenation published in 1995"


Journal ArticleDOI
TL;DR: In this article, a review summarizes published data on catalytic performances of different vanadium-containing oxides, including unsupported and supported V2O5, vanadates, solid solutions and mixed phases, in the oxidative dehydrogenation of C2-C5 alkanes.
Abstract: This review summarizes published data on catalytic performances of different vanadium-containing oxides, including unsupported and supported V2O5, vanadates, solid solutions and mixed phases, in the oxidative dehydrogenation of C2–C5 alkanes. The analysis of the structure-activity relationships shows that various species characterized by a different reactivity exist on the surface of these catalysts. There are some indications that tetrahedral vanadium species are the most favourable for alkane oxidehydrogenation. Its intrinsic activity seems to be largely dependent on the structure of the nearest surrounding and, therefore, can be modified by changing the nature and number of the neighbouring ions. Although the reaction mechanism is generally accepted to be through the redox cycle between V5+ and V4+, opposite relationships between catalyst activity/selectivity and reducibility have been established, even for the same catalytic systems. No clear interpretation regarding the mode of alkane activation can be derived from a survey of the literature. This and some other aspects of the reaction mechanism need further studies at a molecular level.

599 citations


Journal ArticleDOI
TL;DR: The main aspects of ethane and propane oxydehydrogenation are discussed in this article, where the performance of various catalysts described in the literature has been compared and compared.

418 citations


Journal ArticleDOI
TL;DR: In this article, a short review compares different technologies for the synthesis of styrene which are currently studied as alternatives to the industrial dehydrogenation of ethylbenzene: de-deprivation of the polyethylene, followed by oxidation of hydrogen, catalytic and stoichiometric oxidative de-decoupling, and dehydrogenization in membrane reactors.
Abstract: This short review compares different technologies for the synthesis of styrene which are currently studied as alternatives to the industrial dehydrogenation of ethylbenzene: dehydrogenation of ethyl-benzene followed by oxidation of hydrogen, catalytic and stoichiometric oxidative dehydrogenation of ethylbenzene, and dehydrogenation in membrane reactors. The advantages and drawbacks of each technology are illustrated and discussed, and the catalytic systems employed are described.

309 citations


Journal ArticleDOI
TL;DR: In this paper, a kinetic model for the monomolecular conversion of light n-alkanes (propane to n-hexane) over H-ZSM-5 was investigated between 723 and 823 K.

277 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of Mo loading, calcination temperature, reaction temperature and space velocity on the catalytic performance of methane dehydrogenation and aromatization without using oxidants over Mo/HZSM-5 has been studied.
Abstract: The effect of Mo loading, calcination temperature, reaction temperature and space velocity on the catalytic performance of methane dehydrogenation and aromatization without using oxidants over Mo/HZSM-5 has been studied. The XRD and BET measurements show that Mo species are highly dispersed in the channels of the HZSM-5 zeolite, resulting from the interaction between the Mo species and the zeolite, which also leads to a decrease in its crystallinity. The Bronsted acidity, the channel structure and the state and location of Mo species in the zeolite seem to be crucial factors for its catalytic performance. It was found that 2% Mo/HZSM-5 calcined at 773 K showed the best aromatization activity among the tested catalysts, the methane conversion being 9% at 1013 K with the selectivity to aromatics higher than 90%. The experimental results obtained from the variation of space velocity gave evidence that ethylene is an initial product. On the basis of these results a possible mechanism for methane dehydrogenation and aromatization has been proposed in which both the heterolytic splitting of methane in a solid acid environment and a molybdenum carbene-like complex as an intermediate are of significance.

253 citations


Journal ArticleDOI
TL;DR: In this article, the dehydrogenation of methane on MoO3 supported on various oxides has been investigated under non-oxidizing conditions in a fixed bed, continuous flow reactor.
Abstract: The dehydrogenation of methane on MoO3 supported on various oxides has been investigated under non-oxidizing conditions in a fixed bed, continuous flow reactor. Detailed measurements were performed with MoC3/SiO2. The reaction of methane was observed above 923 K after a significant time lag, when a partial reduction of Mo6+ occurred, the reduced phase being characterized by X-ray photoelectron spectroscopy (XPS). The initial gaseous products are CO2, H2O, H2 and CO. But this stage is followed by the dehydrogenation of methane and coupling of hydrocarbon fragments to various hydrocarbons. A possible pathway of the formation of benzene, the main product of reaction with selectivities ranging from 26 to 56%, is suggested.

229 citations


Journal ArticleDOI
M. Besson1, F. Lahmer1, P. Gallezot1, Patrick Fuertes1, Guy Fleche1 
TL;DR: In this article, it was shown that bismuth atoms are selectively and homogeneously deposited on the palladium particles by a surface redox reaction on Pd/C catalysts containing 1-to 2-nm Pd particles.

225 citations


Journal ArticleDOI
TL;DR: In this paper, the authors studied the catalytic activity of supported vanadium catalysts for n-butane oxidation and showed that the reducibility of catalysts, determined from the onset temperature of H 2 -consumption, decreases in the order V/Al 2 O 3 ) > V/MgO (first peak)> V/Sepiolite > V /Mg O (second peak) ≍ V/hydrotalcite.

164 citations


Journal ArticleDOI
TL;DR: An attempt to use carbon dioxide as a diluent and oxidant in the dehydrogenation of ethylbenzene to styrene was carried out over an activated carbon-supported iron catalyst (Fe 17 wt-% ) at 773-973 K, CO2/ethylbenzenes= 50-70 mol/mol and W/F= 30-120 g h/mol as mentioned in this paper.
Abstract: An attempt to use carbon dioxide as a diluent and oxidant in the dehydrogenation of ethylbenzene to styrene was carried out over an activated carbon-supported iron catalyst ( Fe 17 wt-% ) at 773–973 K, CO2/ethylbenzene= 50-70 mol/mol and W/F= 30–120 g h/mol An addition of 20–30 mol-% lithium nitrate to iron resulted in a significant increase in the catalytic activity The highest yield of styrene (40–45%) with more than 90% selectivity was obtained at a ratio of lithium to iron of 01–02 (mol/mol) In addition to styrene, carbon monoxide and water were formed as products This indicated that the reaction proceeds via an oxidative dehydrogenation mechanism Added lithium nitrate was converted into lithium ferrite during the treatment of an iron-lithium co-loaded activated carbon catalyst under carbon dioxide at 973 K Lithium ferrite thus formed would be an active center of the reaction

161 citations


Journal ArticleDOI
Eiichi Kikuchi1
TL;DR: In this article, the metal/ceramic composite membrane is incorporated in the catalytic reactor, as demonstrated in concrete examples of steam and CO2 reforming of methane and dehydrogenation of isobutane.

134 citations


Journal ArticleDOI
TL;DR: In this paper, the same authors showed that the alkaline promoters decrease the acidity and increase the basicity of the catalysts, and hence facilitate desorption of propene from the catalyst surface, preventing it from further oxidation to carbon oxides.
Abstract: Oxidative dehydrogenation of propane has been studied on V2O5/TiO2 and MoO3/TiO2 catalysts, consisting of 1 and 5 monolayers of the deposited oxides, promoted with Li, K and Rb cations. The catalysts were characterized by X-ray photoelectron spectroscopy (XPS) and by isopropanol decomposition, a probe for acid-base properties. For both types of catalysts, irrespective of the vanadium or molybdenum content, the total activity in oxidative dehydrogenation of propane decreased for the promoted catalysts in the sequence: non-promoted ≥ Li > K > Rb-promoted catalyst. The propene yields and selectivities at equal conversion increased in the same order. The same sequence was also observed for the increase in the rate of acetone formation and the decrease in the rate of propene formation in the isopropanol decomposition on the promoted catalysts. It is proposed that the alkaline promoters decrease the acidity and increase the basicity of the catalysts, and hence facilitate desorption of propene from the catalyst surface, preventing it from further oxidation to carbon oxides. The XPS data suggest that the alkaline promoters increase the dispersion of the vanadia or molybdena phase in the high vanadium or molybdenum content catalysts.

Journal ArticleDOI
TL;DR: In this article, isolated tetrahedral V5+ species in the framework of AFI structure are proposed to be the active and selective sites for the oxydehydrogenation of propane.

Journal ArticleDOI
TL;DR: The thermal decomposition of methanol on a clean Pd[lcub]111[rcub] surface has been investigated using X-ray photoelectron spectrometer (XPS), secondary ion mass spectrometry (SIMS) and thermal desorption spectrometric (TDS).

Journal ArticleDOI
TL;DR: In this article, the authors studied the performance of isobutane conversion over silica-supported Pt, Pt/Sn/SiO2 and Pt/N/K catalysts at temperatures from 673 to 773 K. The authors showed that the addition of tin and potassium to the catalysts leads to the formation of smaller ensembles of surface platinum atoms, and the hydrogenolysis, isomerization and coking reactions are thereby suppressed.

Journal ArticleDOI
TL;DR: In this paper, methanol, ethanol, and 2-propanol were adsorbed at room temperature on anatase and rutile powders and temperature-programmed desorption spectra were obtained in a high-vacuum microbalance system.

Journal ArticleDOI
TL;DR: Sulfated zirconia catalyzes the isomerization of n-butane even at 25{degrees}C, and the addition of Fe and Mn promoters increases its activity by three orders of magnitude as mentioned in this paper.


Journal ArticleDOI
TL;DR: In this article, the authors showed that the addition of chloride ions to a Li + -MgO catalyst at a ratio of Cl/Li ≥ 0.9 significantly improves the yields of ethylene that can be achieved during the oxidative dehydrogenation (OXD) of ethane.

Journal ArticleDOI
TL;DR: The ability of the atomic uranium cation U+ to activate a variety of saturated and unsaturated hydrocarbon molecules is investigated in this article, where the mechanism of this metal-mediated cyclotrimerization is enlightened by kinetic measurements, collision-induced dissociation experiments and ion-molecule reactions of the intermediate species.

Journal ArticleDOI
TL;DR: In this article, a temperature programmed reaction/desorption (TPD) study of decomposition pathways of methanol, ethanol, 1-propanol and 2-Propanol was conducted on the clean Pd(110) surface under ultra-high vacuum conditions.
Abstract: A temperature programmed reaction/desorption (TPD) study of decomposition pathways of methanol, ethanol, 1-propanol and 2-propanol was conducted on the clean Pd(110) surface under ultra-high vacuum conditions. No alcohol underwent C-O scission. Alcohols appear to react on this clean surface via the same dehydrogenation and decarbonylation steps observed on the Pd(111) surface. In contrast to previous reports noting substantial differences in methanol chemistry on the Pt(110) and (111) surfaces, the reactions of methanol and ethanol were found to be the same on the Pd(110) and (111) surfaces, giving rise to H2 plus CO from methanol, and H2, CO, and CH4 from ethanol. The C3 alcohols, 1- and 2-propanol, did produce somewhat different products on the Pd(110) and (111) surfaces, but these differences can be accounted for by differences in the chemistry of intermediate reaction products, rather than different reaction pathways of the parent alcohols.

31 Dec 1995
TL;DR: In this article, Huang and Kang reported the rate data shown in Scheme 1 for this reaction catalyzed by Pt/Al{sub 2}O{sub 3}. Isomerization of c-DeHN was treated as irreversible, and it was assumed that dehydrogenation of DeHN could be neglected.
Abstract: Per-hydrogenation of naphthalene produces both cis-decalin (c-DeHN) and trans-decalin (t-DcHN). Huang and Kang reported the rate data shown in Scheme 1 for this reaction catalyzed by Pt/Al{sub 2}O{sub 3}. Isomerization of c-DeHN was treated as irreversible, and it was assumed that dehydrogenation of DeHN could be neglected. We have found it possible to achieve high selectivity for one DeHN isomer by appropriate catalyst selection. For example, PYHY gives 100% naphthalene conversion to decalins with 80% selectivity for c-DeHN. There numerous potential industrial applications for c-DeHN; such as, the production of sebacic acid which can be used in the manufacture of Nylon 6, 10 and softeners. Conversely, catalysts that promote the thermodynamically favored c-DeHN to t-DeHN isomerization can be made to give nearly 96% t-DeHN. This reaction can be used in fuel upgrading applications, to increase the thermal stability of the fuel.

Journal ArticleDOI
TL;DR: In this paper, a mesoporous alumina membrane and a microporous zeolite membrane were used for the dehydrogenation of isobutane in a membrane reactor.

Patent
17 May 1995
TL;DR: In this article, a net catalytic oxidative dehydrogenation of alkanes to produce alkenes is described, which involves simultaneous equilibrium de-hydrogenation and combustion of the hydrogen formed.
Abstract: A process for the net catalytic oxidative dehydrogenation of alkanes to produce alkenes is provided. The process involves simultaneous equilibrium dehydrogenation of alkanes to alkenes and combustion of the hydrogen formed to drive the equilibrium dehydrogenation reaction further to the product alkenes. In the present reaction, the alkane feed is dehydrogenated over an equilibrium dehydrogenation catalyst in a first reactor (110) and the effluent, along with oxygen is then passed into the second reactor (120) containing a metal oxide catalyst which serves to selectively catalyze the combustion of hydrogen. The equilibrium dehydrogenation catalyst may comprise platinum and the selective metal oxide combustion catalyst may contain bismuth, antimony, indium, or molybdenum, or a mixture thereof.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the influence of reaction temperature on the selectivities of the products in 2-propanol and ethanol dehydration and showed a good correlation between the results of dehydration conversion and acid properties, gas-chromatographically measured through the irreversible adsorption of pyridine (473 and 573 K) and 2,6-dimethylpyridine(573 K).

Journal ArticleDOI
TL;DR: In this paper, a detailed kinetic model for a propane aromatization reaction over HZSM-5 and GaHZ SM-5 was developed, and it was shown that the contribution of both routes in propane conversion is at least 1,000 times lower than the rate of diene formation steps.
Abstract: A detailed kinetic model for a propane aromatization reaction over HZSM-5 and GaHZSM-5 is developed Kinetic modeling results show that propane transformation over HZSM-5 occurs via protolytic cracking and hydrogen transfer routes The contributions of both routes in propane conversion are established Rate constants of propane transformation steps are found to be at least 1,000 times lower than the rate constants of diene formation steps, which, in turn, are the slowest among the acid-catalyzed olefin aromatization steps Gallium introduced into ZSM-5 catalyst is active in dehydrogenation of propane into propene, of olefins into dienes, and of naphthenes into aromatics At the same time, gallium species catalyze propane transformation into methane and ethene hydrogenation into ethane Both latter reactions appear to be the main reasons for the limit to aromatics selectivity over GaHZSM-5 catalysts

Journal ArticleDOI
TL;DR: Pt-Sn/ZnAl2O4 catalysts with a Sn/Pt atomic ratio ranging from zero to 6.72 were characterized by hydrogen chemisorption, temperature-programmed reduction and tested in isobutane dehydrogenation.
Abstract: Pt-Sn/ZnAl2O4 catalysts prepared by two-step impregnation (first tin), with a Sn/Pt atomic ratio ranging from zero to 6.72, were characterized by hydrogen chemisorption, temperature-programmed reduction and tested in isobutane dehydrogenation. Metal dispersion correlates linearly with reaction rate; both parameters reach a maximum when the Sn/Pt atomic ratio is about one. The activity of the sites capable of hydrogen chemisorption, as expressed in turnover frequency number, TOF, decrease as the tin concentration is increased. From theoretical ab-inito calculations, it is proposed that tin reduces the platinum-hydrogen charge transfer responsible for hydrogen dissociation through an orbital overlapping.

Journal ArticleDOI
TL;DR: In this article, the authors showed that the supported manganese oxide catalysts are active, selective, and stable in conversion of the CH[sub 4] + CO[sub 2] mixture into synthesis gas and in oxidative dehydrogenation of C[sub 7] hydrocarbons and the lower alcohols.
Abstract: The great interest displayed lately in heterogeneous catalytic reactions of carbon dioxide is caused by two reasons: (1) the necessity to fight the greenhouse effect and (2) the exhaust of carbon raw material sources. Reactions of oxidative transformation of organic compounds of different classes (alkanes, alkenes, and alcohols) with a nontraditional oxidant, carbon dioxide, were studied on oxide catalysts Fe-O, Cr-O, Mn-O and on multicomponent systems based on manganese oxide. The supported manganese oxide catalysts are active, selective, and stable in conversion of the CH[sub 4] + CO[sub 2] mixture into synthesis gas and in oxidative dehydrogenation of C[sub 2] [minus] C[sub 7] hydrocarbons and the lower alcohols. Unlike metal catalysts manganese oxide based catalysts do not form a carbon layer during the reaction.

Journal ArticleDOI
TL;DR: In this article, the catalytic dehydrogenation of propane has been studied over Pt and Pt-Sn catalysts supported on γ-A12O3 and SiO2.

Journal ArticleDOI
TL;DR: In this paper, microcrystalline titanium(IV) oxide (TiO2) powders having high surface area and high crystallinity were synthesized by high-temperature hydrolysis of titanium (IV) alkoxide in organic media and then used for photocatalytic dehydrogenation of 2-propanol in aqueous solution.
Abstract: Microcrystalline titanium(IV) oxide (TiO2) powders having high surface area and high crystallinity were synthesized by high-temperature hydrolysis of titanium(IV) alkoxide in organic media. They were platinized and then used for photocatalytic dehydrogenation of 2-propanol in aqueous solution. The TiO2 catalysts exhibited much higher production rates of hydrogen and acetone than representative active TiO2 catalysts (P-25).

Journal ArticleDOI
TL;DR: An experimental and simulation study has been carried out for the dehydrogenation of ethane to ethylene in a catalytic membrane reactor, with and without reaction on the permeate side.