Effect of chromium content on the properties of a microspherical alumina-chromium catalyst for isobutane dehydrogenation prepared with the use of a centrifugal thermal activation product of gibbsite

The states of chromium in both promoted and unpromoted alumina-chromium catalysts with various chromium contents prepared with the use of a centrifugal thermal activation product of gibbsite were studied in detail. The presence of five chromium species was found in the catalysts of this type: two Cr⁶⁺ and three Cr³⁺ species. The concentration of each particular chromium species depends on the total chromium content of the catalyst. Based on the experimental data, we hypothesized that highly disperse Cr³⁺ particles, the formation of which was completed at a chromium content of ∼7–9 wt %, are responsible for the catalytic activity of alumina-chromium samples in the reaction of isobutane dehydrogenation.     

Effect of calcination conditions on the properties of a catalyst for ethylbenzene dehydrogenation

Summary The effects of calcination conditions on the properties of the catalyst for dehydrogenation of ethylbenzene were studied by using TG, DTA, and XRD. The formation temperature of polyferrite was higher than 600°C. The strength of the catalyst changed during calcination. Higher temperature enhanced the strength and improved the activity of catalyst. The calcination model has great influences on the catalyst performance. Multi-stage calcination improved the catalyst activity.     

Isomerization of anthracene and tetracene on an alumina-chromium oxide catalyst

Conclusions On contact with an alumina-chromium oxide catalyst, anthracene and tetracene in benzene solution undergo isomerization into phenanthrene and chrysene, respectively.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1453–1454, August, 1966.     

Mathematical simulation of propane dehydrogenation involving oxygen on an alumina-chromium catalyst promoted with Co,Ni, Bi,and K oxides

The rate laws of propane dehydrogenation involving oxygen on an alumina-chromium catalyst promoted with Co, Ni, Bi, and K oxides were studied. The reaction was carried out in a flow reactor in the temperature range of 560–640°C at residence times of 0.5–2.5 s. A kinetic model of the process according to a probable reaction scheme was proposed. The rate constants and activation energies of individual reactions that participate in the process were found. A mathematical model of the process was developed with consideration for material and heat balances and hydrodynamic conditions. The concentration and temperature fields and pressure along the height of the catalyst bed were calculated. The dependences of the target product yield and process selectivity on the residence time were plotted.     

添加锡组分对Pt/ZSM-5催化剂丙烷脱氢反应性能的影响

丙烷脱氢制丙烯是优化利用炼厂气和油田伴生气资源的一条重要途径,这方面的研究已日益引起研究者的关注[1～5].对γ-Al2O3为载体的负载型铂催化剂丙烷脱氢催化性能已进行了深入的研究.通过引入特定的助剂,可以提高负载型铂催化剂低碳烷烃脱氢选择性和稳定性[6,7].与Ce、Zn、V、La、Cr、Fe、Zr、Mn等助剂比较,Sn助剂更有利于提高催化剂丙烷脱氢的反应稳定性[8].     

Physicochemical and catalytic properties of alumoiridium systems modified by indium in the dehydrogenation of normal higher paraffins

A study has been made of monometallic and In promoted alumoiridium catalysts for the dehydrogenation of the normal higher paraffins. It has been established that the introduction of In increases the catalytic activity and selectivity with respect to higher olefins. According to IR spectra of adsorbed CO it has been shown that introduction of In modifies the Ir surface possibly due to the formation of mixed clusters. In this process there is a decrease in the number of surface Ir atoms capable of adsorbing H₂ at 300 K but a significant increase in the number of centers for high-temperature dissociative adsorption of H₂ on the carrier. Analogous effects were observed earlier for alumoplatinum catalysts modified by In.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2222–2227, October, 1991.     

Effect of the paste molding pressure on the mechanical strength of an iron oxide catalyst in the dehydrogenation of methylbutenes

The effect of the paste molding pressure on the physicomechanical and texture characteristics of catalysts was studied. An indirect criterion is suggested to evaluate the molding pressure in industrial extruders, whose optimal value ensures good physicomechanical properties of the catalysts and kinetic control over the catalyzed reaction. The results obtained were verified in paste molding on various industrial extruders, and this enabled the optimal choice of the molding equipment.     

Effect of reaction products on dehydrogenation rate of isoamylenes on a membrane catalyst

Conclusions The dehydrogenation of isoamylenes on a membrane catalyst composed of a Pd catalyst with 5.9% Ni under nongradient conditions is inhibited by isoprene, while the reaction rate passes through a maximum when the partial pressure of hydrogen in the starting mixture is increased.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2602–2603, November, 1976.     

Effect of the catalyst structure on the catalytic activity in dehydrogenation of 2-methyl butane

Calorimetry, thermogravimetry, X-ray diffraction analysis, and low-temperature adsorption of nitrogen were used to study the structure of bimetallic Pt—Sn catalysts on zinc–alumina spinel supports. The effect of the porous structure of the catalyst samples synthesized on their catalytic activity in dehydrogenation of 2–methyl butane was analyzed.     

Effect of TMB/P123 ratios on physicochemical properties of mesocellular foam carbon (MCF-C) as catalyst for ethanol dehydrogenation

The preparation of mesocellular foam carbon catalysts with different ratios of 1,3,5-trimethyl benzene (TMB)/P123 is represented for investigation in catalytic activity via ethanol dehydrogenation to acetaldehyde. The TMB was used as a swelling agent and P123 acted as template-structuring. The physicochemical properties of synthesized catalysts were determined using Brunauer-Emmett-Teller (BET) surface area analysis, transmission electron microscopy (TEM), scanning electron microscopy (SEM)–energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), ammonia temperature-programmed desorption (NH₃-TPD), and carbon dioxide temperature-programmed desorption (CO₂-TPD). The evidence suggested that various ratios of TMB/P123 can differently control the mesostructure including the pore size, specific surface area, and pore volume. Particularly, MCF-C 3.5 catalyst (TMB/P123 of 3.5) enhanced the catalytic via ethanol dehydrogenation. Interestingly, effectively controllable pore structure of catalysts is beneficial for the desorption of selective product such as acetaldehyde leading to remarkably increased yield of acetaldehyde. Furthermore, the MCF-C 3.5 evidently exhibited outstanding stability at temperature of 400 °C for 12 h. Thus, it can be reasonably selected the ratio of TMB/P123 as 3.5, which is dominantly facilitated either high diffusion of reactant or high stability without losing of the traditional structure compared with other ratios of TMB/P123.     

Effect of cerium addition on catalytic performance of PtSnNa/ZSM-5 catalyst for propane dehydrogenation

The effect of cerium addition on the catalytic performance of propane dehydrogenation over PtSnNa/ZSM-5 catalyst has been investigated by reaction tests and some physicochemical characterization such as XRD,BET,TEM,XPS,NH 3-TPD,H 2 chemisorption,TPR and TPO techniques.It has been found that with suitable amount of cerium addition,the platinum dispersion increased,while the carbon deposition tended to be eliminated easily.In these cases,the presence of cerium could not only realize the better distribution of metallic particles on the support,but also strengthen the interactions between Sn species and the support.Additionally,XPS spectra confirmed that more amounts of tin could exist in oxidized form,which was advantageous to the reaction.In our experiments,PtSnNaCe(1.1 wt%)/ZSM-5 catalyst exhibited the best catalytic performance.After running the reaction for 750 h,propane conversion was maintained higher than 30% with the corresponding selectivity to propylene of about 97%.     

Catalytic properties,surface composition,and acidity of Ga-ZSM-5 catalysts for aromatization of lower paraffins

A study has been made of the catalytic and acidic properties together with the surface composition of the zeolite HZSM-5 modified by gallium by hydrothermal treatment with a sodium gallate solution and also by impregnation with gallium nitrate solution. It has been established that the first method of introducing gallium produces a more selective catalyst for aromatization of n-butane. It has been shown that under the conditions of the catalytic reaction several types of active centers incorporating Ga are formed: Ga₂O₃ on the zeolite surface, gallium ions inside the zeolite canals, and gallium atoms at the surface of and in the lattice that are bonded to OH groups.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2726–2732, December, 1991.     

Mechanism and kinetics of the hydrogenation of CO with the formation of paraffins and olefins on an iron catalyst

A kinetic model is proposed for the hydrogenation of CO on a Fe/Al₂O₃ catalyst, based on a mechanism of parallel formation of paraffins and olefins. The model satisfactorily describes the experimental data on the dependence of the total rate of conversion of CO to hydrocarbons and the selectivity with respect to paraffins on the composition of the reaction mixture. It was shown that in the case of olefins the successive steps of their hydrogenation, which make a substantial contribution to the distribution of reaction products, must be taken into consideration.L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Nauki Prospekt, Kiev 252039, Ukraine. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 32, No. 2, pp. 118–123, March–April, 1996. Original article submitted May 22, 1995.