共查询到18条相似文献,搜索用时 156 毫秒
1.
采用硅烷偶联剂KH792对陶瓷膜表面进行改性,再利用浸渍还原法制备了钯/陶瓷膜催化剂,并以对硝基苯酚催化加氢为模型反应研究其催化性能,主要考察了制备参数对钯/陶瓷膜催化剂催化性能的影响。结果表明:硅烷偶联剂的改性条件、钯盐溶液浸渍条件以及水合肼还原条件均显著影响钯/陶瓷膜催化剂的催化性能。合适的的制备条件为硅烷偶联剂KH792浓度0.2 g/L,改性时间8 h;钯浸渍溶液浓度0.040 mol/L,浸渍温度30℃,浸渍时间18 h;水合肼还原温度0℃,还原30 min。在该条件下制备的钯/陶瓷膜催化剂在对硝基苯酚催化加氢反应中具有较好的催化性能,其加氢速率达到17.2 mol/(h·m2)。 相似文献
2.
将钯纳米颗粒负载于陶瓷膜表面制备钯/陶瓷膜催化剂,并用于对硝基苯酚催化加氢反应中,考察了陶瓷膜孔径,硅烷偶联剂KH550溶剂及其浓度和改性时间,钯盐浸渍浓度、温度及时间以及还原温度对膜催化剂催化性能的影响.结果表明,采用孔径为200 nm 的氧化铝陶瓷膜,在6g/L的硅烷偶联剂KH550溶液中浸渍48 h,然后在40℃的浓度为0.030 mol/L乙酸钯溶液中浸渍20 h,最后采用水合肼在0℃还原30 min,得到的钯/陶瓷膜催化剂在对硝基苯酚催化加氢反应中显示了较好的催化性能,其加氢速率达15.5 mol/(h·m2). 相似文献
3.
研究了TiO2负载Pd-Fe催化间硝基三氟甲苯的常压加氢反应,考察了反应温度和催化剂质量浓度对加氢反应的影响,建立了加氢反应的动力学方程。结果表明:在间硝基三氟甲苯初始浓度0.125 mol/L,催化剂质量浓度0.32 g/L,氢气压力0.1 MPa,,323.2 K和2.5 h条件下,间硝基三氟甲苯转化率达到99.2%。通过拟合实验数据,加氢反应对间硝基三氟甲苯浓度表现为1级,对催化剂质量浓度表现为0.464级,反应活化能为22 728.0 J/mol。由动力学方程回算得到的间硝基三氟甲苯浓度与实验值能较好地吻合。 相似文献
4.
以Pd/C作为催化剂,对对硝基苯酚催化加氢制备对氨基苯酚进行了研究,考察了溶剂的种类、催化剂Pd的含量、反应温度、反应压力、反应时间等因素对反应的影响。结果表明,反应的最适宜条件为:对硝基苯酚40 g,无水乙醇240 mL,反应压力为0.55 MPa,反应温度为95℃,3%Pd/C催化剂1.5 g,反应时间5 h,对氨基苯酚产率在87%左右,质量分数大于99%。 相似文献
5.
6.
7.
8.
9.
10.
11.
12.
Pd/Al2O3催化剂的制备及其在对氨基苯酚合成中的应用 总被引:1,自引:0,他引:1
用等体积浸渍法制备了Pd/Al2O3催化剂。采用ICP、XRD、HRTEM和XPS等对催化剂的组成和形貌进行表征。结果表明,Pd粒子均匀分布在Al2O3的表面,粒径约为5 nm。在对硝基苯酚催化加氢制备对氨基苯酚的反应中,对催化剂的催化性能进行了考察。Pd/Al2O3催化剂的催化活性随着Pd负载量的增大而增大;其与市售的骨架镍、纳米镍以及2%Pd/C相比,显现了优异的催化活性;Pd/Al2O3具有高的催化选择性;Pd/Al2O3的催化活性稳定性明显优于骨架镍;随着使用次数的增加,Pd/Al2O3的催化活性有所降低,这可能是因为Pd粒子的团聚。 相似文献
13.
在用于对硝基苯酚加氢制备对氨基苯酚的反应-膜分离耦合系统中,催化剂在反应时以悬浮态形式应用,然后用无机陶瓷膜分离回收,催化加氢速率及膜过滤速率是决定该系统运行效率的关键.研究通过综合考察镍粉体催化剂的反应活性与膜分离性能来选择合适的催化剂.实验结果表明,在研究体系中,化学还原法制备的纳米镍粉活性优于物理气相沉积法制备的纳米镍粉和微米镍粉,主要因为化学还原法制备的纳米镍粉具有较大的活性比表面积.膜分离几种镍粉时,活性较高的纳米镍通量较低,而活性较低的微米镍通量较高.通过将具有高活性的纳米镍粉与具有高通量的微米镍粉以适当比例混合使用,不仅可以获得较高的催化活性,同时可以改善膜通量,对反应-膜分离耦合系统的工业化应用具有参考价值. 相似文献
14.
The catalytic hydrogenation ofp-nitrophenol to p-aminophenol was investigated over Ni/TiO2 catalysts prepared by a liquid-phase chemical reduction method. The catalysts were characterized by inductively coupled plasma (ICP), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS) and temperature-programmed reduction (TPR). Results show that the titania structure has favorable influence on physio-chemical and catalytic properties of Ni/TiO2 catalysts. Compared to commercial Raney nickel, the catalytic activity of Ni/TiO2 catalyst is much superior, irrespective of the titania structure. The catalytic activity of anatase titania supported nickel catalyst Ni/TiO2(A) is higher than that of rutile titania supported nickel catalyst Ni/TiO2(R), possibly because the reduction of nickel oxide to metallic nickel for Ni/TiO2(A) is easier than that for Ni/TiO2(R) at similar reaction conditions. 相似文献
15.
Three‐Phase Nitrobenzene Hydrogenation over Supported Glass Fiber Catalysts: Reaction Kinetics Study
The catalytic properties of Pd and Pt supported on woven glass fibers (GF) were investigated in the three‐phase hydrogenation of nitrobenzene (NB). Over all catalysts, a 100 % yield of aniline was attained. The catalytic activity for the best catalysts was two times higher than the activity of commercial Pt/C catalyst traditionally used for liquid–phase hydrogenation. The intrinsic reaction kinetics were studied and a reaction scheme is suggested. The direct formation of aniline from NB was observed over Pd/GF with traces of intermediates. Four intermediate products were detected during aniline formation over Pt/GF: nitrosobenzene, phenylhydroxylamine, azoxybenzene, and azobenzene. The Eley‐Rideal kinetic model fits the experimental data well. The parameters of the model were determined as a function of initial NB concentration and hydrogen pressure. Pt and Pd supported on GF in woven fabrics are suggested as suitable materials for reactors with a structured catalytic bed in multi‐phase reactor performance. 相似文献
16.
《Journal of Catalysis》1999,181(1):49-56
The kinetics of acetylene hydrogenation catalyzed by a clean palladium foil at high pressures are measured and yield an activation energy of 9.6±0.1 kcal/mol when using hydrogen. The rate exhibits a deuterium isotope effect such that the reaction activation energy is 9.0±0.2 kcal/mol for reaction with deuterium. The hydrogen pressure reaction order is 1.04±0.02 at 300 K with an acetylene pressure of 100 Torr and the acetylene order is −0.66 at 300 K and with a hydrogen pressure of 100 Torr. These reaction kinetics closely mimic those of supported model catalysts. In addition, it is found that the rate of benzene formation is accelerated by the addition of hydrogen to the reaction mixture. This is rationalized by proposing that hydrogen enhances the coverage of acetylene under catalytic conditions. This notion can be used to successfully calculate the hydrogen pressure dependence for acetylene hydrogenation as a function of temperature, a value which varies between ∼1.05 and 1.3 as the temperature changes from 300 to 380 K. Possible origins for this effect are discussed. 相似文献
17.
The kinetics of the liquid‐phase catalytic hydrogenation of p‐chlorobenzophenone have been investigated over a 5 % Pd/C catalyst. The effects of hydrogen partial pressure (800–2200 kPa), catalyst loading (0.4–1.6 gm dm–3), p‐chlorobenzophenone concentration (0.37–1.5 mol dm–3), and temperature (303–313 K) were studied. A stirring speed > 20 rps has no effect on the initial rate of reaction. Effects of various catalysts (Pd/C, Pd/BaSO4, Pd/CaCO3, Pt/C, Raney nickel) and solvents (2‐propanol, methanol, dimethylformamide, toluene, xylene, hexane) on the hydrogenation of p‐chlorobenzophenone were also investigated. The reaction was found to be first order with respect to hydrogen partial pressure and catalyst loading, and zero order with respect to p‐chlorobenzophenone concentration. Several Langmuir‐Hinshelwood type models were considered and the experimental data fitted to a model involving reaction between adsorbed p‐chlorobenzophenone and hydrogen in the liquid phase. 相似文献
18.
Palladiumsupported on a high-temperature-withstanding polymer, phenophthalein poly(ether sulfone) (PES-C), exhibits very high catalytic activity both in the carbonylation of allyl bromide and in the hydrogenation of 1-octene at 40°C and atmospheric pressure. The initial activities are up to 345 mol CO/mol Pd min and 493 mol H2/mol Pd min, respectively. The polymer-supported palladium catalysts prepared by refluxing the mixture of PdCl2 and PES-C immersed in benzene/ethanol (1/3, v/v) prior to the preparation of the catalyst show higher catalytic activity than those obtained by refluxing the mixture of PdCl2 and PES-C in benzene/ethanol. The Pd-containing PES-C membranes made from the polymer-supported palladium catalysts are endowed with a very specific permeability of H2 and the corresponding Pd-containing membrane catalysts can also exhibit considerable catalytic activity for the hydrogenation of 1-octene. © 1996 John Wiley & Sons, Inc. 相似文献