Pd/HZSM-5催化剂催化加氢丙酮合成甲基异丁基酮

以HZSM-5为载体,采用浸渍法制备系列Pd/HZSM-5催化剂,在高压连续流动固定床反应器中考察Pd/HZSM-5催化剂催化加氢丙酮一步法合成甲基异丁基酮性能,并对工艺条件进行优化。结果表明,当HZSM-5载体上Pd负载质量分数为0.5%时,在反应温度140 ℃、氢压1 MPa、空速0.48 h^-1和氢酮物质的量比为1条件下,Pd/HZSM-5催化剂催化活性较高,丙酮转化率为45.91%,甲基异丁基酮选择性为94.33%。采用XRD、H₂-TPD、SEM、EDS和TGA等对催化剂进行表征,结果表明,负载质量分数0.5%的Pd在HZSM-5分子筛表面分散均匀,且0.5%Pd/HZSM-5催化剂具有较高氢吸附能力,失活的主要原因为催化剂表面积炭,采用流化床反应器取代传统的固定床反应器可以很好的解决催化剂积炭问题。     

Acetone Transformation over PtCu/H[Al]ZSM5 Catalysts. Effect of Copper Content

A series of bifunctional bimetallic PtCu/H[Al]ZSM5-type catalysts was prepared and acetone transformation was carried out over them at 160°C, 1 atm, acetone/hydrogen molar ratio=3, and WHSV (weight of reactant injected per weight of catalyst per hour) ranging between 9.4 and 38 h^–1. According to the results, as copper atomic fraction (X(Cu)) increases in the bimetallic catalyst, propane formation rate decreases and methyl isobutyl ketone (MIBK) formation rate increases until X(Cu) equals 0.40. These results suggest that active metallic centers for the olefin double bond hydrogenation in the - unsaturated ketone, which leads to the MIBK formation, do not appear to be those hydrogenating the acetone carbonyl double bond to form propane. When X(Cu)>0.40, MIBK formation rate considerably decreases, meaning that practically all platinum metallic centers have been passivated for those copper atomic fractions over the PtCu/H[Al]ZSM5-type catalyst. Therefore, catalysts begin to act only by means of the acid function, and as a result a logical increase in the mesityl oxide (MO) concentration occurs, a substance that is formed by means of an acid catalysis.     

Pt/ZSM-35催化长链正构生物烷烃加氢裂化/异构化制航空煤油

以生物质油加氢脱氧得到的长链正构生物烷烃为原料,考察了H-MCM-49、H-ZSM-5、H-ZSM-22和 H-ZSM-35这4种不同分子筛催化剂的物化性质及其加氢裂化/异构化制生物航空煤油的性能。在此基础上,以H-ZSM-35分子筛为载体,制备并表征了一系列低负载量（0.1%、0.2%和0.3%）的Pt/ZSM-35双功能催化剂,以长链正构生物烷烃转化率、C₉~C₁₆产物选择性、生物航空煤油收率和异正比为指标,对其加氢裂化/异构化制生物航空煤油反应性能进行了评价,并对反应工艺条件进行优化。结果表明：H-ZSM-35的强酸中心强度高、酸量大,其结构中较小的孔口和较大的球型笼使其具有一定的容烃量和较好的择形性能,0.1%~0.3% Pt负载后, Pt/ZSM-35双功能催化剂表现出很好的加氢裂化/异构化活性和选择性。采用0.1% Pt/ZSM-35双功能催化剂在反应条件为320℃、1MPa、0.7h^-1、氢油比840∶1时,长链正构生物烷烃的转化率为84.3%,生物航空煤油收率达41.1%,产物异正比为1.34。81h长运转测试结果表明,该催化剂具有很好的稳定性。     

Conversion of methane and carbon dioxide into synthesis gas over alumina-supported nickel catalysts. Effect of Ni-Al2O3 interactions

A series of alumina-supported nickel catalysts were prepared by calcination of the catalyst precursors in air at different temperatures. The increase in the intensity of Ni-Al₂O₃ interactions with the calcination temperature was found to be unfavourable to the reduction of the catalyst, and thus caused a decrease in activity for the low temperature reaction between methane and carbon dioxide. However, the catalyst with strong Ni-Al₂O₃ interactions suppressed carbon deposition effectively, which can be attributed to the formation of spinel, NiAl₂O₄, after calcination. When the reaction was carried out at 1023 K, all the catalysts tended to exhibit the same activity. At the same time, only filamentous carbon with a hollow inner channel was observed and there were nickel particles on the tip of this filamentous carbon.     

Temperature and hydrogen pressure dependences in the ring opening of methylcyclobutane over Pt/SiO2 catalyst

The temperature and hydrogen pressure dependences in the ring-opening reactions of methylcyclobutane were studied over Pt/SiO₂ catalyst. The temperature dependence of the ring opening revealed that the reaction rate vs. temperature curves passed through a maximum. On the basis of this information two temperatures were selected for hydrogen pressure studies: 573 K, close to the lowest temperature at which any reaction took place at all, and 623 K, where the ring opening of methylcyclobutane exhibited the highest rate. The initial formation rate vs. hydrogen pressure dependence curves are of bimodal type at 573 K, but they increase monotonously at 623 K. Over the working catalyst, no significant changes were observed at 573 K, but the curve for pentane formation changed to a large extent at 623 K. At 573 K, the selectivity of ring opening was close to statistical, with little excess of isopentane (sterically less hindered direction) over both the clean and the working catalyst. This was also observed at 623 K, however, over the working catalyst as the hydrogen pressure increased the selectivity of the ring opening increased as well. Moreover, at the highest hydrogen pressures studied excellent selectivity for the formation of isopentane was observed. The mechanisms over the initial and the working catalysts are discussed on the basis of these experimental findings.     

Selective oxidation of methane to methanol and formaldehyde over V2O5/SiO2 catalysts. Role of NO in the gas phase

The role of nitric oxide incorporation into the reaction feed for the partial oxidation of methane to C₂-hydrocarbons and C₂-oxygenates is evaluated. The addition of NO increases the conversion of methane under all the experimental conditions studied and has a strong effect on the product distribution. At low NO concentration the catalysts yield mainly C₂H_n hydrocarbons, but at higher NO concentrations, carbon oxides dominate. Amongst the C₁-oxygenates produced, methanol is the major compound observed and its proportion increases with increasing NO concentration. The highest C₁-oxygenates yield was 7% at atmospheric pressure. This revised version was published online in July 2006 with corrections to the Cover Date.