壳聚糖表面修饰的SiO_2负载Ni-B非晶态合金的制备及催化性能

以壳聚糖(CS)对SiO_2进行表面修饰,采用浸渍还原法制备了负载型Ni-B非晶态合金催化剂(Ni-B/CS/ SiO_2),并采用XRD、FTIR、电感耦合等离子体发射光谱(ICP)、BET、XPS、TEM、SAED等表征方法研究了催化剂的非晶性质、原子组成、尺寸分布及粒径大小等.考察了催化剂对糠醇加氢制四氢糠醇反应的催化性能,并与没有壳聚糖修饰的Ni-B/SiO_2催化剂及Raney Ni催化剂进行了对比.结果表明,加入壳聚糖制得的Ni-B/CS/SiO_2催化剂的活性组分Ni-B团簇粒径更小,表面活性组分浓度更高,催化活性更高.

负载型非晶态Ni-B/SiO_2合金对芥酸加氢催化性能研究

研究了负载型非晶态Ni B/SiO2 合金催化剂对芥酸加氢制备山嵛酸的催化性能。结果表明 ,Ni B/SiO2 对芥酸加氢具有很高的活性 ,且稳定性较高 ,其催化性能优于非负载Ni B非晶态合金和RaneyNi催化剂。

Ni-B/SiO_2非晶态催化剂对卤代芳香硝基化合物的催化加氢性能

对Ni-B/SiO2 非晶态催化剂在卤代芳香硝基化合物加氢制卤芳胺反应中的催化活性和选择性进行了研究。研究表明 ,该催化剂不仅具有很高的催化活性 ,且反应中卤芳胺脱卤率低 ,反应选择性高 ,寿命长 ,优于RaneyNi催化剂。晶化导致催化剂失活。载体能提高催化剂的分散度 ,使催化剂的活性比表面积增大。将催化剂保存在乙醇溶液中可保持其活性不变。通过催化剂的表征结果 ,讨论了Ni-B/SiO2非晶态催化剂及RaneyNi催化剂的催化活性与其机构的关系。

负载型非晶态Ni-B/SiO_2合金催化剂对油脂加氢催化剂性能的研究

研究了负载型非晶态Ni B/SiO2合金催化剂对菜籽油、大豆油的加氢性能,并与超细非晶态Ni B合金及Raney Ni催化剂的加氢性能进行了比较.结果表明,负载型非晶态Ni B/SiO2合金催化剂对菜籽油、大豆油的加氢具有很高的活性,其催化加氢性能和寿命均优于超细非晶态Ni B合金及Raney Ni催化剂.负载型非晶态Ni B/SiO2合金催化剂可作为绿色环保型催化剂应用于油脂的催化加氢.

L-酒石酸修饰的Ni-B/SiO2非晶态催化剂对苯乙酮的不对称催化加氢性能研究

L-酒石酸修饰的Ni-B/SiO2非晶态催化剂用于苯乙酮不对称催化加氢,结果表明:随着催化剂修饰pH的上升,α-苯乙醇(PE)的产率和光学选择性均有所增加;随着催化剂修饰温度的升高,α-苯乙醇的光学选择性增加,但产率有所下降;反应温度的升高,溶剂极性的增大,均会使α-苯乙醇的光学选择性降低.

超细SiO_2负载非晶态Ni-B合金植物油加氢催化剂的研究

以水玻璃为原料,通过离子交换制得载体SiO2,以NiCl2.6H2O为活性组分前体,KBH4为还原剂,采用液相化学还原法制备了Ni-B/SiO2非晶态合金催化剂;用大豆油催化加氢制备硬化油脂来考察催化剂的催化活性.研究了制备过程中镍含量、还原剂KBH4用量及载体制备方法对催化剂加氢活性的影响.结果表明:镍含量在2 0%(W/W),n(KBH4)∶n(Ni2+)=1.5∶1.0;加乙醇置换凝胶中的水分、低温温烘干制载体SiO2的条件下制备的催化剂活性最高.

大豆油加氢催化剂非晶态合金Ni-B/SiO_2的研究

采用化学还原法 ,制备了用于大豆油加氢的负载型非晶态合金Ni-B/SiO2 催化剂 ,研究了催化剂制备过程中镍含量的调变及还原剂KBH4用量对催化剂活性的影响。发现了催化剂活性最好的制备条件 ,即镍含量为 12 % ,最佳比例KBH4∶Ni2 + =2 5∶1。同时采用XRD和IR对催化剂及加氢产品进行了表征。

The effect of ethanol on the performance of CrO_x/SiO_2 catalysts during propane dehydrogenation

The effects of ethanol vapor pretreatment on the performance of CrOx/SiO2 catalysts during the dehydrogenation of propane to propylene were studied with and without the presence of CO2.The catalyst pretreated with ethanol vapor exhibited better catalytic activity than the pristine CrOx/SiO2,generating 41.4% propane conversion and 84.8% propylene selectivity.The various catalyst samples prepared were characterized by X-ray diffraction,transmission electron microscopy,temperature-programmed reduction,X-ray photoelectron spectroscopy and reflectance UV-Vis spectroscopy.The data show that coordinative Cr^3＋ species represent the active sites during the dehydrogenation of propane and that these species serve as precursors for the generation of Cr^3＋.Cr^3＋ is reduced during the reaction,leading to a decrease in catalytic activity.Following ethanol vapor pretreatment,the reduced CrOx in the catalyst is readily re-oxidized to Cr^6＋ by CO2.The pretreated catalyst thus exhibits high activity during the propane dehydrogenation reaction by maintaining the active Cr^3＋ states.

Synthesis of Methyl Glycolate by Hydrogenation of Dimethyl Oxalate over Cu-Ag/SiO_2 Catalyst

Methyl glycolate is a good solvent and can be used as feedstock for the synthesis of some important organic chemicals. Catalytic hydrogenation of dimethyl oxalate （DMO） over copper-silver catalyst supported on silica was studied. The Cu-Ag/SiO2 catalyst supported on silica sol was prepared by homogeneous deposition-precipitation of the mixture of aqueous euprammonia complex and silica sol. The proper active temperature of Cu-Ag/SiO2 catalyst for hydrogenation of DMO was 523-623 K. The most preferable reaction conditions for methyl glycolate （MG） were optimized： temperature at 468-478 K, 40-60 mesh catalyst diameter, H2/DMO ratio 40, and 1.0 h^-1 of LHSV.

In_2O_3-modified Cu/SiO_2 as an active and stable catalyst for the hydrogenation of methyl acetate to ethanol

A series of indium oxide‐modified Cu/SiO2catalysts were synthesized and used to produce ethanol via methyl acetate hydrogenation.In‐Cu/SiO2catalyst containing1.0wt%In2O3exhibited the best catalytic activity and stability.The physicochemical properties of the synthesized catalysts were investigated using several characterization methods and the results showed that introducing suitable indium to Cu/SiO2increased the copper dispersion,diminished the copper crystallite size,and enriched the surface Cu+concentration.Furthermore,the Cu/SiO2catalyst gradually deactivated during the stability test,which was mainly attributed to copper sintering and the valence change in surface copper species.In contrast,indium addition can inhibit the thermal transmigration and accumulation of copper nanoparticles to stabilize the catalyst.?2018,Dalian Institute of Chemical Physics,Chinese Academy of Sciences.Published by Elsevier B.V.All rights reserved.

The nature of the deactivation of hydrothermally stable Ni/SiO2–Al2O3 catalyst in long-time aqueous phase hydrogenation of crude 1,4-butanediol

The deactivation of Ni/SiO2-Al2 O3 catalyst in hydrogenation of crude 1,4-butanediol was investigated.During the operation time of 2140 h,the catalyst showed slow activity decay.Characterization results,for four spent catalysts used at different time,indicated that the main reason of the catalyst deactivation was the deposition of carbonaceous species that covered the active Ni and blocked mesopores of the catalyst.The TPO and SEM measurements revealed that the carbonaceous species included both oligomeric and polymeric species with high C/H ratio and showed sheet.Such carbonaceous species might be eliminated through either direct H2 reduction or the combined oxidation-reduction methodologies.

Effect of ZrO_2 Crystalline Phase on the Performance of Ni-B/ZrO_2 Catalyst for the CO Selective Methanation

Amorphous Ni-B/ZrO2 catalysts were prepared by coprecipitation-chemical reduction with KBH4 aqueous solution,and various crystalline phase ZrO2(amorphous-ZrO2,tetragonal-ZrO2 and monoclinic-ZrO2) supported Ni-B catalysts were obtained by thermal treatment in 5%H2-N2 stream at different temperature.The effect of ZrO2 polymorphs and the treatment temperature on the catalytic performance for the CO selective methanation were investigated,and the catalysts were characterized by N2 physisorption,Powder X-ray diffraction(XRD), Temperature-Programmed Desorption(CO-TPD and H2-TPD),and Differential Scanning Calorimeter(DSC).The treatment temperature affected strongly the crystalline structure of ZrO2,and the CO methanation activity and selectivity of the Ni-B/ZrO2 catalysts were significantly influenced by the crystalline phase of ZrO2.Of the three forms of ZrO2 polymorphs(amorphou-ZrO2,tetragonal-ZrO2 and monoclinic-ZrO2),the amorphous-ZrO2 supported nickle catalyst showed highest CO methanation activity,attributing in large part to the largest specific surface area and the optimum CO/H2 absorption intensity of the Ni-B/amorphous-ZrO2 catalyst.

Partial oxidation of methane over SiO2 supported Ni and NiCe catalysts

Nickel and nickel-ceria catalysts supported on high surface area silica, with 6 wt% Ni and 20 wt% CeO2 were prepared by microwave assisted(co) precipitation method. The catalysts were investigated by XRD,TPR and XPS analyses and they were tested in partial oxidation of methane(CPO). The catalytic reaction was carried out at atmospheric pressure in a temperature range of 400–800℃ with a feed gas mixture containing methane and oxygen in a molecular ratio CH4/O2=2. The Ni catalyst exhibited 60% methane conversion with 60% selectivity to CO already at 500℃. On the contrary, the Ni–Ce catalyst was inert to CPO up to 700℃. Moreover, the former catalyst reproduced its activity at the descending temperatures maintaining a good stability at 600℃, over a reaction time of 80 h, whereas the latter one completely deactivated. Test of CH4 temperature programmed surface reaction(CH4-TPSR) revealed a higher methane activation temperature(> 100℃) for the Ni–Ce catalyst as compared to the Ni one. Noticeable improvement of the ceria containing catalyst occurred when the reaction test started at a temperature higher than the methane decomposition temperature. In this case, the sample achieved the same catalytic behavior of the Ni catalyst. As confirmed by XPS analyses, the distinct electronic state of the supported nickel was responsible for the differences in catalytic behavior.

Ni-B/SiO_2催化剂上硝基苯选择加氢制备苯胺

以KBH4为还原剂,用浸渍-还原法制备了Ni-B/SiO2催化剂,并用于硝基苯催化加氢制苯胺的反应,讨论了制备条件(Ni、B用量及焙烧温度)及反应条件(压力、温度)对硝基苯的转化率及苯胺选择性的影响。结果表明,Ni-B/SiO2催化剂具有很高的催化活性。适当增加Ni和B的用量,可以提高催化剂对硝基苯的转化率和转化频率及苯胺的选择性。催化剂前驱体的焙烧温度在453K时,硝基苯的转化率可达到98·5%,对苯胺选择性为97·0%。过高的焙烧温度不利于催化剂活性的提高。适当提高加氢反应压力以及温度,可以提高催化剂的加氢活性及对苯胺的选择性。

Photocatalytic Synthesis of Hydrocarbon Oxygenates from C_2H_6 and CO_2 over Pd-MoO_3/SiO_2 Catalyst

Pd-MoO3/SiO2 catalyst has been prepared using the method of incipient wetness impregnation. The photo absorbing behaviors and chemisorbing properties of the catalyst have been characterized by UV-vis spectra and TPD-MS experiments. The results indicated that metal Pd loaded on MoOa/SiO2 has a significant effect on the photo absorbing performance of MoOa/SiO2, and an obvious blue shift of the absorption edge is produced. Under UV irradiation, the chemisorption state of CO2 undergoes decomposing process to form CO at 481 K, and a two-site adsorption state of ethane can be formed at around 496 K. Photo-oxidation of ethane using carbon dioxide can mainly produce propanal, ethanol and acetaldehyde in the temperature range of 353-423 K. The presence of metal Pd improves the catalytic activity remarkably.

Characterization and catalytic performance of CeO_2-Co/SiO_2 catalyst for Fischer-Tropsch synthesis using nitrogen-diluted synthesis gas over a laboratory scale fixed-bed reactor

The surface species of CO hydrogenation on CeO2-Co/SiO2 catalyst were investigated using the techniques of temperature programmed reaction and transient response method. The results indicated that the formation of H2O and CO2 was the competitive reaction for the surface oxygen species, CH4 was produced via the hydrogenation of carbon species step by step, and C2 products were formed by the polymerization of surface-active carbon species （-CH2-）. Hydrogen assisted the dissociation of CO. The hydrogenation of surface carbon species was the rate-limiting step in the hydrogenation of CO over CeO2-Co/SiO2 catalyst. The investigation of total pressure, gas hourly space velocity （GHSV）, and product distribution using nitrogen-rich synthesis gas as feedstock over a laboratory scale fixed-bed reactor indicated that total pressure and GHSV had a significant effect on the catalytic performance of CeO2-Co/SiO2 catalyst. The removal of heat and control of the reaction temperature were extremely critical steps, which required lower GHSV and appropriate CO conversion to avoid the deactivation of the catalyst. The feedstock of nitrogen-rich synthesis gas was favorable to increase the conversion of CO, but there was a shift of product distribution toward the light hydrocarbon. The nitrogen-rich synthesis gas was feasible for F-T synthesis for the utilization of remote natural gas.

Effect of CO_2 on the structural variation of Na_2WO_4/Mn/SiO_2 catalyst for oxidative coupling of methane to ethylene

In this work,the influence of CO2 on the structural variation and catalytic performance of Na2WO4/Mn/Si O2 for oxidative coupling of methane to ethylene was investigated. The catalyst was prepared by impregnation method and characterized by XRD,Raman and XPS techniques. Appropriate amount of CO2 in the reactant gases enhanced the formation of surface tetrahedral Na2WO4 species and promoted the migration of O in MOx,Na,W from the catalyst bulk to surface,which were favorable for oxidative coupling of methane. When the molar ratio of CH4/O2/CO2 was 3/1/2,enriched surface tetrahedral Na2WO4 species and high surface concentration of O in MOx,Na,W were detected,and then high CH4 conversion of 33.1% and high C2H4 selectivity of 56.2% were obtained. With further increase of CO2 in the reagent gases,the content of active surface tetrahedral Na2WO4 species and surface concentration of O in MOx,Na,W decreased,while that of inactive species（Mn WO4 and Mn2O3） increased dramatically,leading to low CH4 conversion and low C2H4 selectivity. It could be speculated that Na2WO4 crystal was transformed into Mn WO4 crystal with excessive CO2 added under the reaction conditions. Pretreatment of Na2WO4/Mn/Si O2 catalyst by moderate amount of CO2 before OCM also promoted the formation of Na2WO4 species.

Effects of operating parameters on oxidative coupling of methane over Na-W-Mn/SiO_2 catalyst at elevated pressures

The effects of operating parameters on oxidative coupling of methane （OCM） over Na-W-Mn/SiO2 catalyst have been studied at elevated pressures of 0.2, 0.3 and 0.4 MPa under low gaseous hourly space velocity （GHSV） and low temperature conditions. Experimental results show that when the operating pressure is increased, C2＋ yield slightly decreases, while the maximum ratio of ethylene to ethane remains unchanged. Moreover, it has been found empirically that increase of pressure does not affect the catalyst behavior permanently, the catalyst recovers its original low pressure performance without hysteresis behavior by reducing the pressure. Under the investigated conditions, when oxygen is completely consumed, the increase of GHSV leads to improvement in C2 selectivity, while C3＋ and COx selectivities decrease slightly. The C2＋ selectivity increases by increase of nitrogen diluent in the feed, but the C3＋ hydrocarbons selectivities decrease with increase of nitrogen since it is possible that further dilution at high pressure may reduce the probability of collision between CH3 and C2＋ hydrocarbons. During the stability test at high pressure, the catalyst performance remains unchanged throughout the 20 h running. The fresh and used catalysts were characterized using XRD, SEM and N2 adsorption-desorption methods. It was found that the phase transformation of the support from α-cristobalite to tridymite and quartz does not have obvious effect on catalyst performance at high pressure.

Ni-B/TiO_2 Amorphous Catalyst Used in Heavy Arenes of Petrochemicals Hydrogenation

A supported Ni-B/TiO2 amorphous catalyst was prepared by impregnation and reduction. It was characterized by XRD, SAED, DSC, XPS, etc.. The catalytic activity of catalyst was measured through the hydrogenation of heavy arenes in petrochemicals for the first time.

Active Fischer-Tropsch synthesis Fe-Cu-K/SiO_2 catalysts prepared by autocombustion method without a reduction step

The purpose of this study was to prepare iron-based catalysts supported on silica by autocombustion method for directly using for Fischer-Tropsch synthesis（FTS） without a reduction step. The effect of different citric acid（CA）：iron nitrate（N） molar ratios and acid types on the FTS performance of catalysts were investigated. The CA：N molar ratios had an important influence on the formation of iron active phases and FTS activity. The iron carbide（FexC）, which is known to be one of the iron active phases, was demonstrated by the X-ray diffraction and X-ray photoelectron spectroscopy. Increasing the CA：N molar ratios up to 0.1 increased CO conversion of catalyst to 86.5%, which was then decreased markedly at higher CA：N molar ratios. An excess of CA resulted in carbon residues covering the catalyst surface and declined FTS activity. The optimal catalyst（CA：N molar ratio = 0.1） achieved the highest CO conversion when compared with other autocombustion catalysts as well as reference catalyst prepared by impregnation method, followed by a reduction step. The autocombustion method had the advantage to synthesize more efficient catalysts without a reduction step. More interestingly, iron-based FTS catalysts need induction duration at the initial stage of FTS reaction even after reduction, because metallic iron species need time to be transformed to FexC. But here, even if without reduction, FexC was formed directly by autocombustion and induction period was eliminated during FTS reaction.