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排序方式: 共有1474条查询结果,搜索用时 15 毫秒
21.
Boron-based metal-free catalysts for oxidative dehydrogenation of propane (ODHP) have drawn great attention in both academia and industry due to their impressive activity and olefin selectivity. Herein, the SiO2 and B2O3 sequentially coated honeycomb cordierite catalyst is designed by a two-step wash-coat method with different B2O3 loadings (0.1%–10%) and calcination temperatures (600, 700, 800 °C). SiO2 obtained by TEOS hydrolysis acts as a media layer to bridge the cordierite substrate and boron oxide via abundant SiOH groups. The well-developed straight channels of honeycomb cordierite make it possible to carry out the reactor under high gas hourly space velocity (GHSV) and the thin wash-coated B2O3 layer can effectively facilitate the pore diffusion on the catalyst. The prepared B2O3/SiO2@HC monolithic catalyst exhibits good catalytic performance at low boron oxide loading and achieves excellent propylene selectivity (86.0%), olefin selectivity (97.6%, propylene and ethylene) and negligible CO2 (0.1%) at 16.9% propane conversion under high GHSV of 345,600 ml·(g B2O3)−1·h−1, leading to a high propylene space time yield of 15.7 g C3H6·(g B2O3)−1·h−1 by suppressing the overoxidation. The obtained results strongly indicate that the boron-based monolithic catalyst can be properly fabricated to warrant the high activity and high throughput with its high gas/surface ratio and straight channels. 相似文献
22.
Alumina supported vanadia catalysts (V/Al) for selective oxidehydrogenation of ethylbenzene with CO2 were prepared by impregnation method. During preparation the effect of promoters and calcined temperature was investigated,
it was found these two items had a strong influence on the activity of V/Al catalysts. Dehydrogenation reaction with CO2 was happened in the fixed-bed reactor at 450 °C. Results showed that 15.2% ethylbenzene conversion and 99.2% styrene selectivity
were acquired when V2K/Al catalyst was used. 相似文献
23.
An oxygen permeable mixed ion and electron conducting membrane (OPMIECM) was used as an oxygen transfer medium as well as a catalyst for the oxidative dehydrogenation of ethane to produce ethylene. O2- species transported through the membrane reacted with ethane to produce ethylene before it recombined to gaseous O2, so that the deep oxidation of the products was greatly suppressed. As a result, 80% selectivity of ethylene at 84% ethane conversion was achieved, whereas 53.7% ethylene selectivity was obtained using a conventional fixed-bed reactor under the same reaction conditions with the same catalyst at 800 °C. A 100 h continuous operation of this process was carried out and the result indicates the feasibility for practical applications. 相似文献
24.
T. Giornelli A. Lfberg L. Guillou S. Paul V. Le Courtois E. Bordes-Richard 《Catalysis Today》2007,128(3-4):201-207
Catalytic wall (structured) reactors and structured supports are suitable to study the catalytic properties of nanosized materials. The coating of metallic (aluminum and stainless steel) plates by thin layers of active phase is presented in two cases, VOx/TiO2 and Co/SiO2, catalysts used in the oxidative dehydrogenation (ODH) of propane and in Fischer–Tropsch synthesis (FTS) of clean fuels, respectively. The preparation of coated plates and their characterisation by various methods of physicochemical analysis are described. Both chemical and physical methods were used for coating. VOx/TiO2 layers were obtained by grafting of Ti (on Al or stainless-steel plates) and V (on TiO2) alkoxides and use of sol–gel media or suspension. A silica primer was deposited (on stainless-steel plate) by plasma-assisted chemical vapour deposition (PACVD) onto which Co oxide and silica were coprecipitated from sol–gel. The catalytic experiments in the respective reactions were carried out in special plate reactors and compared with those of catalytic powders. The study shows that the coating of a metallic substrate by a catalyst is not straightforward and requires specific studies dealing with both chemistry (chemical affinity between substrate and catalytic layers) and catalytic engineering (catalytic performance in taylor-made reactors). 相似文献
25.
The oxidative dehydrogenation of ethane was studied over Pt–Sn impregnated monoliths at 1 bar, 600–900 °C and with different
contents of oxygen, hydrogen and steam in the feed gas. As expected a decrease in oxygen in the feed led to a decrease in
the conversion of ethane due to lower temperatures in the reactor. Adding steam to the feed showed no effect on the ethane
conversion or the ethene selectivity. When the hydrogen/ethane ratio in the feed was varied from 0 to 0.5 at 700 and 850 °C,
it resulted in a significant increase in the selectivity to ethene while the ethane conversion remained relatively unchanged.
At 700 °C the selectivity increased from about 50% to 93% (carbon basis) with only a small decrease in the conversion of ethane.
The results clearly show that both Pt and Sn have a catalytic effect. Pt caused the ethane conversion to rise and addition
of Sn resulted in much better ethene selectivity. However, even though Sn alone showed some catalytic effect at lower temperatures,
it cannot explain the great difference between the Pt and Pt–Sn catalysts. A reasonable assumption is therefore that there
exist interactions between Pt and Sn that gives the Pt–Sn catalysts excellent properties for oxidative dehydrogenation of
ethane, in particular upon addition of hydrogen. 相似文献
26.
Co–BaCO3 catalysts exhibited high catalytic performance for oxidative dehydrogenation of ethane (ODE) using CO2 as oxidant. The maximal formation rate of C2H4 was 0.264 mmol · min−1 · (g · cat.)−1 (48.0% C2H6 conversion, 92.2% C2H4 selectivity, 44.3% C2H4 yield) on 7 wt% Co–BaCO3 catalyst at 650 °C and 6000 ml. (g · cat.)−1. h−1. Co–BaCO3 catalysts were comparatively characterized by XRF, N2 isotherm adsorption-desorption, XRD, H2-TPR and LRs. It was found that Co4+–O species were active sites on these catalysts in ODE with CO2. The redox cycle of Co–O species played an important role on the catalytic performance of Co–BaCO3 catalysts. On the other hand, the co-operation of BaCO3 and BaCoO3 was considered to be one of possible reasons for the high catalytic activity of these catalysts. 相似文献
27.
Catalytic performances of various metal molybdates were tested in the oxidative dehydrogenation of propane to propene with molecular oxygen under an atmospheric pressure. Most of the molybdates tested promoted the selective oxidative conversion of propane to propene and among them cobalt and magnesium molybdates were found highest in the activity and selectivity. It was also found that their catalytic activities were highly sensitive to the catalyst composition, and it turned out that Co0.95MoO
x
and Mg0.95MoO
x
catalysts which have slightly excess molybdenum showed the highest activity in the oxidative dehydrogenation of propane. Under the optimized reaction conditions, higher reaction temperatures and lower partial pressures of oxygen, these catalysts gave 60% selectivity to propene at 20% conversion of propane. Since the molybdates having the surface enriched with molybdenum oxide tended to show high activity for the propane oxidation, surface molybdenum oxide clusters supported on metal molybdate matrix seem to be the active sites for the selective oxidative dehydrogenation of propane. 相似文献
28.
A. A. Castro 《Catalysis Letters》1993,22(1-2):123-133
Selective dehydrogenation of high molecular weight linear paraffins is an important process step for the production of biodegradable detergents. Pt, PtSn, PtGe and PtPb supported on -A12O3 doped with alkaline metals were characterized and tested in then-decane dehydrogenation reaction. When alkaline metals are added to Pt/Al2O3 a promoting effect on the selectivity to olefins in then-decane dehydrogenation is observed. Regarding PtSn/Al2O3 -doped catalysts their performance depends on the alkaline metal used as dopant, the Sn content and the preparation method. Moreover these bimetallic catalysts show a better olefin yield and a lower selectivity to gases and aromatics than the monometallic platinum catalysts. PtGe and PtPb based catalysts have an analogous behavior to the PtSn one but its selectivity to olefins is lower. 相似文献
29.
邻苯基苯酚的合成研究 总被引:4,自引:0,他引:4
以环己酮为原料,经过缩合得到环己酮二聚体,通过浸渍法制备γ—Al2O3负载Pt—K2SO4作为环己酮二聚体脱氢制备邻苯基苯酚的催化剂,通过讨论脱氢过程的各种影响因素以确定脱氢催化剂的组成和最佳反应条件,从而得到较高选择性和寿命的催化剂,进一步得到收率高,纯度好的产品。 相似文献
30.
K. Wakui K. Satoh G. Sawada K. Shiozawa K. Matano K. Suzuki T. Hayakawa Y. Yoshimura K. Murata F. Mizukami 《Catalysis Letters》2002,81(1-2):83-88
Dehydrogenative cracking reaction of n-butane was studied using HZSM-5 catalyst modified with various metal oxides. Alkaline earth (magnesium), transition metal (cobalt) and rare earth (lanthanum) elements are used for the modification. The selectivity of the products was studied at low conversion (20%). Methane, ethane, ethylene, propylene, butenes and butadiene were the main products. With the use of the cobalt- or magnesium-containing HZSM-5, dehydrogenative cracking was observed and the selectivity of ethylene was much larger than that of ethane. On the other hand, the selectivity of ethylene and ethane were almost the same in the reaction using the lanthanum-containing HZSM-5. It is considered that the cobalt- and magnesium-loaded sites on HZSM-5 played an important role in the dehydrogenative cracking. 相似文献