Co-Pd双金属催化剂载体对甲烷-合成气两步梯阶转化催化性能的影响

采用浸渍法制备了不同载体负载的Co-Pd双金属催化剂,在自制的连续式步阶反应器上将CH4与合成气反应转化成C2+含氧化合物。研究表明,载体对催化剂催化性能有较大影响。Al2O3作载体时,两步梯阶转化催化剂活性和C2+含氧化合物的选择性最高,达70.9%;Al2O3载体更有利于活性金属Pd和Co的分散和还原,有利于得到催化反应所需的表面酸强度和酸量,从而提高了其催化性能。     

制备方法对Co-Pd/TiO2催化剂催化CH4-CO2梯阶转化的影响

以钴、钯为活性金属, 分别采用浸渍法和溶胶-凝胶法制备了Co-Pd/TiO₂催化剂, 考察了不同制备方法制备的Co-Pd/TiO₂催化剂对CH₄-CO₂梯阶转化直接合成C₂含氧化合物的影响。利用XRD、XPS和N₂-吸附-脱附对催化剂进行了表征。结果表明:两种方法制备的催化剂反应前与反应后表面织构都存在较大变化, 且催化剂中均存在CoTiO₃物种, 这是活性金属Co与载体TiO₂之间发生强相互作用, CO²⁺替代TiO₂晶格中的Ti⁴⁺的结果;CoO和金属Pd可能是该反应的活性中心;反应前与反应后溶胶-凝胶法制备的催化剂的表面Co含量均低于浸渍法制备的催化剂, 而表面Pd含量则均高于浸渍法制备的催化剂, 且溶胶-凝胶法制备的催化剂各种产物的生成速率均高于浸渍法制备的催化剂, 因此, 与浸渍法制备的催化剂相比, 溶胶-凝胶法制备的催化剂具有更好的催化活性。     

酸改性CoPd/TiO2催化CH4-CO2直接合成C2含氧化合物

采用酸处理方法对CoPd/TiO₂催化剂进行改性,并将酸改性催化剂用于温和条件下CH₄-CO₂梯阶转化直接合成C₂含氧化合物（乙酸和乙醇）的反应。在150～300℃考察了浸酸方式和不同种类酸处理对催化剂活性和选择性的影响。采用X射线衍射（XRD）、X射线光电子能谱（XPS）、NH₃程序升温脱附（NH₃-TPD）和N₂吸附对催化剂进行了表征。结果表明,酸改性明显提高了CoPd/TiO₂上C₂含氧化合物的生成速率和选择性。浸酸方式对催化剂性能和结构有显著影响,先用酸浸渍载体然后再浸渍活性金属所得催化剂具有更高的活性。在H₃PO₄、HNO₃和HCl中,H₃PO₄浸渍的催化剂活性最佳,在150℃时C₂含氧化合物（乙酸和乙醇）的生成速率为3365 μg/(g·h),选择性达到91%。     

合成气制C2含氧化合物Rh基催化剂中的载体效应

负载型Rh基催化剂是实现由煤或生物质经合成气制乙醇等C2含氧化合物过程的最高效催化剂之一,其中载体的选择至关重要。本文综述了硅胶、Al2O3、TiO2、多孔炭材料、分子筛和复合氧化物等载体负载的Rh基催化剂性能及其研究进展,阐明了载体中的杂质、孔道结构、酸碱性、表面基团性质和可还原性等性质如何影响催化剂活性组分的物化性质乃至催化性能。结果表明,载体与活性组分(助剂)间的相互作用机制和程度是理解载体效应的关键。因此,应设计和制备出具有适宜孔结构、表面活性和可还原性适中、略偏碱性的催化剂载体,同时细致优化催化剂制备和活化过程,以达到适宜的金属-载体相互作用,确保产生更多的催化活性位,从而最大限度地提高Rh的催化效率,推动该过程的工业化进程。     

活性金属负载量及配比对CuFe双金属催化剂催化合成混合醇的影响

采用液相还原法制备了CuFe双金属催化剂，考察了活性金属负载量及Cu、Fe摩尔比对催化剂反应活性和C₂₊混合醇选择性的影响，分析了活性金属负载量、Cu/Fe摩尔比、催化剂结构及反应性能间的构-效关系，优化了催化剂的制备配方。结果表明，活性组分负载量的增大有助于提高催化剂的反应活性，但过量的金属负载量会导致活性组分发生团聚，影响总醇及C₂₊混合醇的选择性；Cu/Fe摩尔比的增大抑制了催化剂的反应活性，但有助于增强CO吸附能力及Cu、Fe间的协同效应，提高产物中醇类及C₂₊醇的选择性。综合考虑CO转化率、总醇及C₂₊醇选择性，液相还原法制备CuFe双金属催化剂较适宜的活性组分总负载量为30%、铜铁摩尔比为3.0。     

成型TiO_2负载型纳米碳纤维催化材料的制备与表征

采用成型TiO2为载体,以甲烷为碳源,镍铜双金属催化剂,改变反应温度以及碳氢比(CH4/H2摩尔比),生长纳米碳纤维(CNF),制备出结构化复合纳米碳纤维催化材料-生长在成型TiO2上的纳米碳纤维材料(CNF/TiO2).扫描电镜(SEM)和物理吸附仪(BET)表征结果表明,CNF粗细均匀、直径～70 nm,而且与其他传统催化剂载体(活性炭)相比几乎没有微孔.并以CNF/TiO2为载体,采用浸渍法负载金属钯,制备出结构化纳米碳纤维负载型钯催化剂(Pd/CNF/TiO2),以苯乙烯加氢为模型反应进行活性评价,结果表明,其催化活性明显优于成型活性炭负载型Pd催化荆.结构化纳米碳纤维具有比表面适中,且不含微孔,是一种优良的催化剂载体,可望用于受内扩散制约的气液固三相催化反应.     

双金属Ni-Co/HZSM-5催化剂上甲烷二氧化碳重整反应

采用等体积浸渍法制备一系列双金属Ni-Co/HZSM-5催化剂,考察反应温度和Ni与Co质量比对甲烷二氧化碳催化重整性能的影响。采用BET和H2-TPR表征催化剂的孔结构和还原性能,结果表明,负载的活性组分均匀分散在HZSM-5载体孔道内。Ni与Co之间存在协同作用,促进了Ni-Co/HZSM-5催化剂的还原性能。单金属Co催化剂几乎对甲烷没有转化活性,双金属Ni-Co催化剂催化活性明显提高,Ni与Co质量比6∶4时,催化剂甲烷二氧化碳重整反应的催化活性和稳定性优于单金属Ni催化剂。     

钒和钼添加量对乙酸合成催化剂性能的影响

采用等体积浸渍法制备了含金属助剂钒(V)和钼(Mo)的Co-Pd/TiO2催化剂,在固定床反应器装置上考察了该催化剂催化CH4和CO2反应合成乙酸的性能,用XRD,TPD和TPR等技术表征了催化剂.结果表明,V和Mo的加入量能影响载体的结晶度,促进活性金属的还原,调节催化剂表面酸性,提高活性金属在载体表面的分散度,从而影响催化剂的催化活性.     

Co-Cu/ZrO_2-La_2O_3催化剂用于合成气制低碳醇的研究

采用柠檬酸络合-多次浸渍法制备了一系列Zr O2负载La Co0.7Cu0.3O3钙钛矿结构的催化剂。利用X射线衍射(XRD)、透射电镜(TEM)、程序升温还原(TPR)等技术对催化剂进行表征,并采用加压微型固定床反应器对其合成气转化制低碳醇的催化性能进行评价。结果表明,催化剂前驱体经还原后形成了氧化镧修饰的氧化锆载体负载Co Cu合金颗粒(Co-Cu/Zr O2-La2O3),Co Cu合金颗粒与氧化镧修饰的氧化锆载体之间的共同作用使催化剂显示了优良的醇选择性,特别是C2+醇的选择性。     

钴改性的镍催化甲烷二氧化碳重整反应研究

以CeO_2作为载体,合成了含有更多金属活性位点的钴镍双金属催化剂,并用于催化甲烷二氧化碳重整反应的研究。为了深入探讨双金属催化剂中钴和镍之间的作用机制,通过改变两种活性金属钴和镍的加入顺序,分别合成了Co-Ni/CeO_2、Ni-Co/CeO_2和Ni Co/CeO_2催化剂。与单金属催化剂对比,研究了Co的加入对镍基催化剂的影响,并确认了双金属催化剂中Co与Ni存在的状态和加入顺序对催化剂催化性能的影响。     

载体制备方法对Ni/TiO2催化剂顺酐液相加氢性能的影响

为了制备高活性和高选择性催化剂,实现顺酐下游加氢衍生物的定向合成,分别采用水热法、沉淀法和溶胶-凝胶法制备TiO2载体,并以浸渍法制备Ni质量分数为10%的Ni/TiO₂催化剂。采用N₂低温物理吸附、XRD、H₂-TPR及H₂-TPD等方法对催化剂进行表征,并评价催化剂的顺酐液相加氢性能。结果表明,以溶胶-凝胶法制备TiO₂为载体的催化剂具有最高的CC及CO加氢活性,在反应温度240 ℃和氢压5 MPa条件下,顺酐转化率为100%,γ-丁内酯选择性为52.2%,是相同反应条件下水热法TiO₂负载Ni催化剂的3.3倍和沉淀法TiO₂负载Ni催化剂的6.2倍。产生这一现象的原因与溶胶-凝胶法制备的TiO₂以锐钛矿和金红石混合晶相存在有关。     

Au-Ru/TiO2催化硝基苯和苯甲醛一锅法合成N-苄基苯胺

采用沉积-沉淀法制备出一系列Au-Ru/TiO2双金属催化剂,用于硝基苯与苯甲醛一锅法加氢反应合成N-苄基苯胺。考察了Ru负载量对Au-Ru/TiO2加氢性能的影响,并采用X射线衍射和扫描电镜等方法对催化剂进行表征。结果表明,Au和Ru产生协同作用共同促进加氢作用。负载Ru质量分数为1.5%的催化剂具有最好的加氢活性和N-苄基苯胺选择性。优化的N-苄基苯胺合成工艺条件为：催化剂用量占硝基苯质量的15%,溶剂为甲苯,氢压1.1 MPa,反应温度80 ℃。此条件下,硝基苯转化率100%,N-苄基苯胺选择性88.2%     

载体对Cu-Co催化剂催化CO_2加氢合成乙酸反应的影响

采用等体积浸渍法制备了以TiO2、Al2O3、SiO2为载体的Cu-Co基双金属催化剂,在固定床反应器上,考察了其催化CO2加氢合成乙酸的性能,并用X射线衍射、NH3-TPD、H2-TPR等对催化剂进行了表征。结果表明,以TiO2为载体的Cu-Co基催化剂有最好的催化活性和选择性,乙酸生成速率可达16.41 mg/(gcat.h),选择性为81.3%。研究认为,催化剂表面适量的中强酸性、金属良好的分散性以及CuCo2O4的生成是影响催化性能的关键因素。     

Effects of Supports and Promoter Ag on Pd Catalysts for Selective Hydrogenation of Acetylene

SiO2, a-Al2O3, g-Al2O3, ZrO2 and CeO2 were used as supports and Ag as promoter to study their effects on Pd catalysts for selective hydrogenation of acetylene. The catalysts were prepared by impregnated synthesis and characterized by XRD, BET and TEM. The catalytic reaction was carried out in a fixed-bed reactor. Overall, the low specific surface area supports were better to increase the ethylene selectivity at high conversion rate of acetylene. Among the four Pd catalysts on low specific surface area supports, the catalyst on low specific surface area SiO2 (LSA-SiO2) retained a high ethylene selectivity even at complete conversion, while the other catalysts showed significant decrease in the selectivity at complete conversion. The performance of Pd/LSA-SiO2 was important to decrease the loss of ethylene in selective hydrogenation of trace acetylene in ethylene. Addition of Ag to Pd/LSA-SiO2 significantly decreased the formation of ethane, C4 alkenes and green oil, and improved the ethylene selectivity to 90% when Pd:Ag=1:1 and 1:3(w). When the ratio of Pd to Ag was above 1, the activity of Pd-Ag bimetallic catalyst was similar to that of Pd monometallic catalyst, and the selectivity of ethylene increased with increasing of amount of Ag. When the ratio of Pd to Ag was below 1, the activity of bimetallic catalyst decreased with increasing of amount of Ag, while the selectivity of ethylene was kept unchanged. The optimum temperature was 200~230℃ for 0.02%(w)Pd-0.02%(w)Ag/LSA-SiO2 to give a high ethylene selectivity and low formation of green oil.     

载体对Au-Pd催化剂甲醇部分氧化制氢性能的影响

用PVP保护乙醇还原法制备了一系列Au-Pd/MOx(M=Zn、Ce、Fe、Ti、Cr和Al)双金属催化剂,考察了不同载体对Au-Pd催化剂甲醇部分氧化制氢性能的影响,用XRD、TG、TPD、TPR和TPH等对催化剂进行了表征。结果表明,载体对催化剂性能有较大影响,与钛、铬和铝氧化物载体相比,448K时偏碱性的锌、铈和铁氧化物载体负载的Au-Pd催化剂的甲醇转化率均在80.0%以上,催化剂积碳量降低。其中以Au-Pd/ZnO催化剂的效果最好,523K时甲醇转化率和氢气选择性分别为99.0%和45.6%,反应20h后积碳量仅为0.0232g/gcat.。     

Influences of preparation methods of ZrO2 support and treatment conditions of Cu/ZrO2 catalysts on synthesis of methanol via CO hydrogenation

ZrO₂ supports were prepared by different methods (conventional precipitation method, shortened as “CP”, and alcogel/thermal treated with nitrogen method, shortened as “AN”), and Cu/ZrO₂ catalysts were prepared by impregnation method. The supports and catalysts were characterized by BET, XRD, TEM and TPR. The effects of the preparation methods of ZrO₂ supports and the treatment conditions (calcination and reduction temperatures) of the catalyst precursors on the texture structures of the supports and catalysts as well as on the catalytic performances of Cu/ZrO₂ in CO hydrogenation were investigated. The results showed that the support ZrO₂-AN had larger BET specific surface area, cumulative pore volume and average pore size than the support ZrO₂-CP. Cu/ZrO₂-AN catalysts showed higher CO hydrogenation activity and selectivity of oxygenates (C₁–C₄ alcohols and dimethyl ether) than Cu/ZrO₂-CP catalysts. Calcination and reduction temperatures of supports and catalyst precursors affected the catalytic performance of Cu/ZrO₂. The conversion of CO and the STY of oxygenates were 12.7% and 229 g/kg h, respectively, over Cu/ZrO₂-AN-550 at the conditions of 300 °C, 6 MPa.     

Catalytic activity of ethylene oxidation over Au,Ag and Au–Ag catalysts: Support effect

Au, Ag and Au–Ag catalysts on different supports of alumina, titania and ceria were studied for their catalytic activity of ethylene oxidation reactions. An addition of an appropriate amount of Au on Ag/Al₂O₃ catalyst was found to enhance the catalytic activity of the ethylene epoxidation reaction because Au acts as a diluting agent on the Ag surface creating new single silver sites which favor molecular oxygen adsorption. The Ag catalysts on both titania and ceria supports exhibited very poor catalytic activity toward the epoxidation reaction of ethylene, so pure Au catalysts on these two supports were investigated. The Au/TiO₂ catalysts provided the highest selectivity of ethylene oxide with relatively low ethylene conversion whereas, the Au/CeO₂ catalysts was shown to favor the total oxidation reaction over the epoxidation reaction at very low temperatures. In comparisons among the studied catalysts, the bimetallic Au–Ag/Al₂O₃ catalyst is the best candidate for the ethylene epoxidation. The catalytic activity of the gold catalysts was found to depend on the support material and catalyst preparation method which govern the Au particle size and the interaction between the Au particles and the support.