微乳法制备纳米催化剂研究进展

微乳法作为制备纳米微粒的有效方法,具有操作简单、制备粒子尺寸均匀、颗粒大小及形状可控等优点,在纳米催化剂制备领域具有广阔的应用前景。综述了近年来采用微乳法制备纳米催化剂的研究状况,尤其是对利用微乳法制备金属纳米粒子、金属氧化物及负载型金属催化剂进行了综述。     

微乳法制备Fe-DMC催化剂用于CO_2与环氧丙烷聚合

采用微乳法制备了铁锌双金属氰化物(Fe-DMC)催化剂,改变破乳时间获得不同形态的Fe-DMC催化剂。破乳时间为4h时制备的Fe-DMC催化剂催化CO2与环氧丙烷(PO)共聚合,在80℃,4MPa条件下,所制共聚物中CO2固定率为44%,脂肪族PPCP的摩尔分数为99%,且共聚物数均分子量达9.20×104,相对分子质量分布仅为1.03,均优于用沉淀法制备的Fe-DMC催化剂催化CO2与PO共聚合。当破乳时间增加到9h,产物中出现大量的环状碳酸酯,数均分子量下降,且相对分子质量分布增大。     

Pd-Cu/γ-Al_2O_3双金属催化剂脱除水中硝酸盐

采用分步浸渍法和共浸渍法制备系列Pd负载质量分数为1%的Pd-Cu/γ-Al2O3双金属催化剂,以氢气为还原剂研究其对水中硝酸盐催化脱除的性能。结果表明,催化剂中Cu与Pd物质的量比以及Cu、Pd的浸渍顺序对催化剂性能有重要影响,硝酸根转化率随着Cu与Pd物质的量比的增大而增大;硝酸根转化活性以Cu与Pd物质的量比为5∶1、先浸渍Pd再浸渍Cu所得催化剂较优;从氨氮选择性方面看,以先浸渍Cu后浸渍Pd制备的催化剂选择性较低,在Cu与Pd物质的量比为1∶1、先浸渍Cu再浸渍Pd所得催化剂较优。     

微乳法制备脂肪醇胺化催化剂的研究

利用Ｗ／Ｏ型的微乳液,制成脂肪醇胺化的负载型催化剂。研究了制备方式、活性组分含量、微乳液的含水量（Ｗ）、灼烧温度对催化剂性能的影响。优化条件下制备的催化剂中金属含量２２．４％,在反应温度２１０℃、催化剂加入量１．５％的条件下,转化率大于９７％,选择性大于９６％。     

反相微乳法制备DMCC用于催化二氧化碳与环氧丙烷共聚

通过反相微乳法和共沉淀法合成了钴锌双金属氰化物催化剂。研究了制备方式及共聚反应条件对其催化性能及聚碳酸酯组成的影响。结果表明,反相微乳法制备的DMCC-1具有较低的结晶度且可以配合更多的有机配体,在80℃、4 MPa条件下,采用一步加料法催化CO2与环氧丙烷共聚,所制备的聚碳酸酯中碳酸酯单元量达43.5%,数均分子量达36 400,且聚合物分散指数仅为2.07。共聚结果表明,一步加料法有利于提高聚合物的数均分子量,而逐步加料法有利于降低聚合物的相对分子量分布。     

微乳法制备纳米催化剂的工艺和应用

本文阐述了微乳法制备纳米催化剂的基本原理,方法和应用。     

微乳法制备细分散渣油悬浮床加氢催化剂

采用微乳法,通过调整表面活性剂的组成,制备用于渣油悬浮床加氢的细分散催化剂。对制备的催化剂样品进行光学显微镜和等离子分析,结果表明,采用理想的乳化剂配方可以使催化剂均匀稳定分布在渣油原料中,无沉降现象发生。同时,以孤岛常压渣油为原料,在高压釜上考察细分散催化剂的反应性能。试验结果表明,在相同的反应条件下(435 ℃,10 MPa,1 h^－1),同时控制生焦量在允许范围,524 ℃以下液体收率可以提高5～7个百分点,从而进一步证实均匀分散的催化剂具有较高的活性和抑焦性能,具有很好的应用前景和使用价值。     

Pd-Fe双金属催化剂制备与应用研究进展

综述Pd-Fe双金属催化剂的制备工艺和应用研究进展,分析制备工艺、载体、金属质量比、反应条件对催化剂结构和性能的影响。浸渍法生产方法简单、生产能力高、成本低且活性组分利用率高,但存在活性组分分布不均的缺陷;沉淀法杂质含量低,活性组分结合紧密,但存在工艺过程冗长、活性组分分散均匀程度低的劣势;控制条件并添加表面分散剂时,液相还原法可制备粒径均匀、分散性好、比表面积大的催化剂。在传统的制备过程中引入超声、微波等强化手段,可以提高活性组分的分散度,缩短制备时间,降低生产成本。Pd-Fe双金属催化剂在脱氯、加氢和氧化上都表现出优异的催化性能,在反应体系中添加单宁酸等辅助试剂可提高催化性能。     

微乳技术制备纳米催化剂的研究进展

综述了微乳技术制备纳米催化剂的基本原理和影响因素以及在催化剂制备中的应用。该方法所采用装置简单、操作方便,制备的催化剂具有粒径小、粒径可调、分布均匀、催化反应活性高等优点。微乳体系的构成是多种多样的,讨论了各种因素对制备纳米催化剂的影响,指出了该技术存在的问题和发展趋势。     

微乳法制备纳米材料的研究进展

综述了微乳法制备纳米材料的基本原理和主要方法,阐述了微乳法制备纳米材料的一些影响因素,以及在纳米材料制备方面的研究现状,并对该领域的研究发展作了展望。     

负载型双金属催化剂催化间苯二甲腈加氢制备间苯二甲胺

采用浸渍法制备活性炭负载Ni、Ru、Rh单金属及Ni-Ru、Ru-Rh双金属催化剂,考察反应温度、反应压力和m(催化剂)∶m(间苯二甲腈)对间苯二甲腈加氢制备间苯二甲胺的影响。结果表明,Ni-Ru/C催化活性高于Ru/C和Ni/C,通过分步浸渍法制备的Ni-Ru/C催化活性优于一步浸渍法。以甲醇和甲苯为混合溶剂,在m(催化剂)∶m(间苯二甲腈)=1∶20、反应温度120℃、反应压力4.0 MPa和1 000 r·min-1条件下,无需加入碱性抑制剂,间苯二甲胺收率最高可达97.78%。     

The hydrogenation of triglycerides using supported alloy catalysts. II. Silica-supported Pd-Cu catalysts

Palladium-copper catalysts supported upon silica, containing 2–6% (w/w) total metal, have been prepared by (i) precipitation and (ii) impregnation methods. The catalysts were employed for the hydrogenation of soyabean oil at 1 bar H₂ pressure and at 160°C in a stirred batch reactor. Temperature-programmed reduction studies provided evidence of alloying of palladium and copper and metal surface area measurements exhibited evidence of a slight maximum in the metal surface area at around 90 at. % Pd content. In addition, it was observed that the presence of copper seemed to prevent sintering of palladium, giving a more stable or even enhancing metal surface area compared with palladium alone. Activity measurements showed that there was evidence of a maximum at around 80–90 at. % Pd content. However, selectivity measurements showed that the latter parameter was dominated by the presence of palladium and except at very high copper contents the superior selectivity of the latter for linolenate chain hydrogenation was hardly evident. It is thought that the palladium may cause the copper to be present largely as Cu°, which is not as effective as Cu¹ in catalysing selective hydrogenation of multiply unsaturated species.     

钌钯双金属催化剂催化L-氨基丙酸加氢特性

通过添加金属Pd对Ru/C催化剂进行改性,提高了L-氨基丙酸加氢制备L-氨基丙醇的收率和光学选择性。采用ICP-MS、XRD、TEM和XPS对所制备的催化剂进行了系统的表征,结果表明：RuPd物种在载体活性炭上分散均匀粒径较小,Pd原子的加入可显著改善Ru的电子特性,调变不同的RuPd原子比,可影响RuPd物种的存在状态,进而影响L-氨基丙醇的收率和光学选择性。在氨基丙酸浓度为0.9 mol·L^-1,磷酸浓度0.69 mol·L^-1,催化剂用量为反应物的20%,反应温度95℃,压力4.0 MPa的反应条件下,RuPd原子比为3∶1时催化剂表现出最好的催化性能,L-氨基丙醇的收率达到99.7%,产品的光学选择性同样达到了99.7%,同时催化剂能循环使用20次,催化性能基本保持不变。     

γ‐Alumina supported Cu‐Ni bimetallic catalysts: Characterization and selective hydrogenation of 1,3‐butadiene

Addition of a second metal often improves the selectivity of a supported catalyst for the hydrogenation of 1,3‐butadiene. Catalysts containing 15 wt% Ni and varying amounts of Cu were prepared and characterized by TPR, XRD and XPS. The Cu‐Ni interaction affects the reduction behavior of the catalysts. TPR result shows that the synergetic effect of copper and nickel modifies the capability of metal to combine with hydrogen in bulk phase. The Ni 2p spectra in XPS shows significant shifts toward lower binding energies with increasing copper loading. From XRD results it is represented that aggregation of nickel occurs more easily due to the copper addition. The adding of copper on Ni/Al₂O₃ makes the conversion rate decreased and increases the selectivity to 1‐butene.     

Pd-Cu负载型催化剂催化还原水中硝酸盐的研究进展

综述了Pd-Cu负载型催化剂催化还原水中硝酸盐的研究进展。总结了Pd-Cu负载型催化剂的催化特征及其催化活性。重点介绍了Pd-Cu/陶瓷膜催化剂催化还原水中硝酸盐的活性及其作用机理。提供了一种新的方法用来提高催化还原硝酸盐过程中的催化性能。     

A new type of selectivity by using bimetallic catalysts

The results demonstrate a very interesting change in selectivity for the bimolecular reaction between benzophenone and methanol in the presence of hydrogen to produce ether; 1-methoxy-1,1-diphenylmethane by using silica supported bimetallic Ni-Cu (7525) and Ni-Fe (7525) catalysts as compared to Ni/SiO₂. However, no suppression of C-O bond hydrogenolysis was observed for bimetallic as well as for TiO₂ supported catalysts.Deceased.     

Structure and promotion of bimetallic catalysts: Activity and selectivity

Activity and selectivity of carbon monoxide hydrogenation can be effectively controlled by using bimetallic catalysts. There are two effects which should be taken into consideration: (1) influencing the mode of CO chemisorption: dissociative vs associative, or (2) affecting the amount and type of surface hydrogen: weakly vs strongly bound to the surface.Associative CO chemisorption is controlled by two factors: either by the formation of an alloy phase as is for PtFe or PdFe where rehybridization of the Pd d-orbital results in a decreased back donation, or by an effect of a charged particles such as Fe³⁺ or RE ions which operates via a charge polarization. In highly dispersed state, e.g. inside a zeolite cage, similar effect is operative. In both cases oxygenates formation is a significant reaction pathway.The mode of hydrogen chemisorption also affects the selectivity of the reaction. When the activated form of hydrogen is in large proportion, all the processes which require hydrogen are suppressed, consequently olefin formation is the main route of reaction.The factors influencing both hydrogen and CO chemisorption will be considered. Here the paper will be focused on the effect of alloying, metal dispersion and shape selective environment.Prepared for presentation at American Institute of Chemical Engineering, 1990 Spring National Meeting, March 18–22, 1990, The Peabody, Orlando Fl-Fischer-Tropsch Synthesis V: Effect of Local Coordination Environment Around the Active Metal.