Improvement on Pd-Pb/CaCO_3 catalyst for selective hydrogenation of acetylenic linkage in hydrocarbons

利用XRD和SEM研究了EDTA、草酸等助剂对沉淀CaCO3显微结构的影响,结果表明,CaCO3晶型及形貌随助剂不同而变化,甚至同一助剂不同添加量亦会导致其晶相的显著差异。XRD分析表明,在草酸存在下,沉积物为单一的方解石相,该晶型的CaCO3对Pd Pb/CaCO3催化剂呈现明显的模板效应。不同还原方法的尝试说明,水合肼是一种好的还原剂。TEM研究表明,在适宜条件下对催化剂老化处理,表面金属钯颗粒发生聚并,并且由此带来部分氢化选择性的较大提高。Influences of additives (PVA, oxalic acid, EDTA, ZnCl_2) on microstructure of precipitated calcium carbonate (CaCO_3) were investigated using SEM and XRD. The results indicated that crystal form and shape of CaCO_3 vary with both type and quantity of the additives. XRD results showed that the deposit crystallized in calcite in the presence of oxalic acid,which exhibited distinct template effect in Pd-Pb/CaCO_3 system. The test results of different reduction methods showed that hydrazine hydrate was a good reducing agent. TEM images showed that palladium particles on the catalyst surface agglomerated after appropriate aging treatment and thus improved partial hydrogenation selectivity of the catalyst

Methane Combustion over PdO Crystallite Manipulated by Support Template

通过对PdO活性组分在单斜与四方型氧化锆载体上的热化学性质和催化活性进行比较性的研究显示,单斜型ZrO2的表面原子能够满足与PdO的结构适应性匹配条件,它可以通过界面原子的取向附生作用对表面PdO物种聚集形态进行调控,从而促进PdO组分在单位载体表面上的分散.此外,升降温循环过程的DTG分析还表明,单斜载体模板在反复的氧化还原循环中逐渐将结晶型PdO加工成取向附生型PdO,不断改善PdO物种的氧迁移性质,促进了热还原钯物种在高温区的氧化再生.这两种载体效应有效地抑制了甲烷燃烧反应在高温区的活性振荡,增加了燃烧的稳定性与催化剂的反应耐受性.四方ZrO2晶相在载体内的掺杂将导致上述的载体效应受到明显抑制.A comparative investigation on the thermochemical and catalytic properties of palladium oxide crystallite supported on monoclinic or tetragonal-doped zirconia, demonstrated that by sharing the interfacial atoms with monoclinic zirconia, PdO crystallite aggregates at the aid of this epitaxy on the support template to acquire better dispersion. Moreover, tracking the heating-cooling cycles in air atmosphere, DTG analysis illustrated that the crystallized PdO gradually transforms into the epitaxial PdO species on the monoclinic zirconia and the improved mobility of oxygen in lattices promotes the oxidative regeneration of PdO at high temperature thereby. Combining the above two superiorities on aggregation forms of PdO, the template of monoclinic zirconia inhibits the high temperature deactivation of catalysts for methane combustion, mean- while, increases the stability of combustion reaction and the sustainability of catalysts. However, the doping of tetragonal zirconia into monoclinic support muffles those advantages prominently.国家基础研究重点发展规划(No.G1999022400);; 国家自然科学基金(No.20203014)资助项目

Methane combustion over PdO crystallite manipulated by support template

A comparative investigation on the thermochemical and catalytic properties of palladium oxide crystallite supported on monoclinic or tetragonal-doped zirconia, demonstrated that by sharing the interfacial atoms with monoclinic zirconia, PdO crystallite aggregates at the aid of this epitaxy on the support template to acquire better dispersion. Moreover, tracking the heating-cooling cycles in air atmosphere, DTG analysis illustrated that the crystallized PdO gradually transforms into the epitaxial PdO species on the monochnic zirconia and the improved mobility of oxygen in lattices promotes the oxidative regeneration of PdO at high temperature thereby. Combining the above two superiorities on aggregation forms of NO, the template of monoclinic zirconia inhibits the high temperature deactivation of catalysts for methane combustion, meanwhile, increases the stability of combustion reaction and the sustainability of catalysts. However, the doping of tetragonal zirconia into monoclinic support muffles those advantages prominently

Study on Pd-Pb/CaCO_3 Catalyst for Selective Hydrogenation of Acetylenic Link in Hydrocarbon

用正交试验研究了喹啉、催化剂、温度等因素对炔键选择加氢的影响,方差分析及显著性检验结果表明喹啉添加量与催化剂用量之间的配比对炔烃氢化反应的选择性有重大影响,并利用二元表和二元图得到了优化的反应条件.不同还原方法的尝试说明水合肼也是一种好的还原剂.两种浸渍方法的对比表明,用双浸渍法制备的钯催化剂选择加氢性能整体优于常规浸渍法制备的催化剂,当浸渍比为1 1时选择性最好,并对该现象进行了讨论.Influence of quinoline,catalyst,temperature and so on,on selective hydrogenation of acetylenic link was investigated with orthogonal test method.The results of analysis of variance and test of significance indicate that,mixing different doses of quinoline and catalyst do cause obvious difference in hydrogenation selectivity of alkynes.Then the optimal reaction condition is established by bipartite graph.The trial of different reductive methods explains that hydrazine hydrate is also a kind of good reducing agent.Comparison of the double impregnation method (DI) with the conventional impregnation method (CI) shows that the properties of the catalyst prepared by DI method are better than those prepared by CI method.Ensuing improvement of semihydrogenation selectivity was found and discussed