混合金属氧化物固载杂多酸的制备及催化性能

杂多酸是一类含氧桥的多核无机高分子化合物,由于其独特的笼型结构而具有许多优异的性能,尤其是作为一种新型的多功能催化剂越来越受到人们的关注。因此,近年来人们一直致力于研究新型固载杂多酸催化剂。本文介绍了钛钨混合金属氧化物固载杂多酸催化剂HPA／TiO2-WO3的制备,及催化合成甲酸环己酯的方法,此法具有反应时间短、催化剂价廉易得、工艺简单、酯产率较高等优点。     

HRP-12催化剂上苯与直链烯烃的烷基化反应 Ⅰ. 本征反应动力学研究

直链烷基苯是生产阴离子表面活性剂直链烷基苯磺酸盐的重要原料。2000年以美国环球油品公司(UOP)的脱氢法工艺生产的直链烷基苯占世界直链烷基苯产量的88％。脱氢法以液体氢氟酸为催化剂由正构烯烃与苯进行烷基化反应生产直链烷基苯。由于液体氢氟酸催化剂具有较强的腐蚀     

Dehydrogenation of n-butane over vanadia catalysts supported on silica gel

VOx/SiO2 catalysts prepared by impregnation method were used for catalytic dehydrogenation of n-butane to butenes and characterized by X-ray diffraction,FT-IR,UV-vis,Raman,and BET measurements.The effects of VOx loading and the reaction temperature on the VOx/SiO2 catalysts and their catalytic performances for the dehydrogenation of n-butane were studied.When the VOx loading was 12% g/gcat and reaction temperature was between 590 ℃ and 600 ℃,n-butane conversion and butenes yields reached the highest value under H2 flux of 10 ml/min and n-butane flux of 10 ml/min.Product distribution,such as the ratio of 2-butene to 1-butene and the ratio of cis-2-butene to trans-2-butene,was mainly influenced by the reaction temperature.     

聚苯胺炭复合载体制备的钯催化剂对甲酸的电催化氧化

制备了导电高分子聚苯胺与活性炭的复合载体(PAnC),用PAnC作为载体制备的钯催化剂性能优于单独活性炭作为载体制备的催化剂。此外掺杂十二烷基磺酸钠制备的聚苯胺碳载体(PAnC-S)具有比PAnC更低的电荷传递电阻,10~25 nm的介孔数量明显增加,比表面积增大到94.9 m²/g。PAnC-S与PAnC粒径均匀,粒径均在30 nm左右。以PAnC-S和 PAnC为载体制备的钯催化剂比活性炭作载体制备的钯催化剂具有更大的电化学比表面积,分别为84.7和62.6 m²/g。对甲酸的氧化具有更高的电化学活性和稳定性。     

HRP-12催化剂上苯与直链烯烃的烷基化反应 Ⅱ. 失活动力学研究

采用连续操作的釜式反应器，利用悬浮态的负载杂多酸催化剂HRP-12上的烷基化反应的实验数据进行参数估值，确定了失活反应速率常数、失活反应活化能、活性保留函数的失活反应级数和烯烃摩尔浓度的失活反应级数，建立了苯与直链烯烃烷基化反应的失活动力学模型。模型表明：该失活反应对于活性保留函数是一级失活反应，对于烯烃摩尔浓度是二级失活反应。统计检验表明：所得失活动力学方程在显著性水平α=0.005下有较高的实验数据拟合精度和模型可信度。     

一种具有Keggin结构的固体杂多酸的合成及其晶体结构

以钨酸钠、氯化钴、醋酸钴及1,3-丙二胺为原料,利用水热合成法制备了一种具有Keggin结构的杂多酸H6[CoW12O40].2.5H2O;利用单晶X射线衍射分析了产物的晶体结构.结果表明,产物中的过渡金属Co2+离子作为中心原子与4个氧原子形成CoO4四面体;CoO4四面体被4个W3O13金属簇包围,与每个W3O13金属簇之间通过共顶点连接而形成[CoW12O40]6-阴离子;六个氢离子作为抗衡阳离子,最终形成固体杂多酸分子.     

Dehydrogenation of isobutane in the presence of carbon dioxide over supported vanadium oxide catalysts

Summary The dehydrogenation of isobutane to isobutene in the presence of carbon dioxide was carried out over supported vanadium oxide catalysts. The influence of the support on the catalytic performance was investigated. The isobutane conversion and isobutene selectivity in the presence of carbon dioxide were compared with the results obtained during the dehydrogenation reaction in the presence of helium (inert gas). The catalysts were characterized by temperature-programmed techniques (TPR, TPD-NH₃, TPD-CO₂).     

Selective hydrogenation of crotonaldehyde over raney cobalt catalysts modified with heteropolyacid salts

RCo-based catalysts were modified with Keggin type heteropolyacid salts, including alkali, alkaline earth and transition metal salts. The selective hydrogenation of crotonaldehyde was investigated over these catalysts. The selectivities to crotyl alcohol can be improved on all modified catalysts. Among them, the catalyst modified with copper salts of 12-molybdophosphates shows the best performance in improving the selectivity. This revised version was published online in June 2006 with corrections to the Cover Date.     

Dehydrogenation of methanol on low Cu and Re—Cu catalysts supported on sibunite

The activity and selectivity of mono- and bimetallic catalysts containing copper and rhenium on sibunite were studied in the decomposition of methanol to methyl formate (MF), water, H₂, CO, and CO₂at 200—400 °C. Methane is also formed on rhenium-containing catalysts at 300—400 °C. The dehydrogenating activity and selectivity to form MF are higher on the copper-sibunite catalysts than on the rhenium-sibunite samples. The introduction of 0.25% Re into the 4% copper-containing catalyst enhances its total activity and stability.     

Dehydrogenation of 2-propanol with suspended noble metal catalysts: activity enhancement by the addition of sodium hydoxide

Catalytic dehydrogenation of 2-propanol was carried out in the presence of suspended Rh/C, Ru/C, Pd/C, Pt/C or Pt/Al₂O₃ under boiling and refluxing conditions. Adding NaOH to the 2-propanol enhanced the H₂ evolution rate by a factor of 1.06-52.9, depending on the catalyst. The activity enhancements observed with KOH, Mg(OH)₂, Ca(OH)₂ and NaHCO₃ were lower than those with NaOH. This revised version was published online in August 2006 with corrections to the Cover Date.     

Cu-Ni双金属催化剂催化脂肪伯醇脱氢制备醛

脂肪伯醇催化转化制备相应的醛是具有挑战性的课题,目前多采用负载的单金属铜基催化剂.本文报道了双金属催化剂Cu-Ni/γ-Al2O3催化3,3-二甲基-1-丁醇脱氢制备相应的醛,在相同反应条件下,Cu-Ni/γ-Al2O3比单金属催化剂Cu/γ-Al2O表现出更高的催化活性,能将一系列脂肪伯醇高选择性转化为相应的醛.     

钒掺杂TiO2/AC负载催化剂的制备及光催化活性

以TiO2为主要成分的光催化剂的研究已日益受到人们的广泛关注[1-6]。但TiO2粉末的回收和流失问题难以解决,固定化TiO2负载催化剂的研制是解决这一问题的有效手段[2-6]。从实际应用的观点看,TiO2的光催化剂活性还有待进一步提高。研究发现,大多数过渡金属离子和少数非金属离子的     

纳米聚苯胺及聚苯胺/金复合材料的制备与表征

以氯金酸(HAuCl4)为氧化剂,在两种不同无机酸(HCl和H2SO4)的掺杂下,通过调节反应体系中混合溶剂的醇水比例,用一步氧化苯胺聚合法成功制备了不同形貌的纳米聚苯胺及聚苯胺/金复合材料.通过扫描电子显微镜(SEM)、紫外可见吸收光谱(UV-Vis)和红外光谱(FT-IR)对产物的形貌和结构进行了表征.在此基础上,进一步讨论了聚苯胺/金复合材料可能的形成机理.     

Transesterification of ketoesters with alcohols using polyaniline salts as catalysts

Polyaniline salts have been used as catalysts for the transesterification of ketoesters with alcohols in a process being reported for the first time. The catalytic use of polyaniline salts is feasible because of their easy preparation, recovery and reusability. Copyright © 2004 John Wiley & Sons, Ltd.     

Surface acidity of supported vanadia catalysts

The surface acidity of SiO₂, γ-Al₂O₃ and TiO₂ supported vanadia catalysts has been studied by the microcalorimetry and infrared spectroscopy using ammonia as the probe molecule. The acidity in terms of nature, number and strength was correlated with surface structures of vanadia species in the catalysts, characterized by X-ray diffraction and UV-Vis spectroscopy. It was found that the dispersion and surface structure of vanadia species depend on the nature of supports and loading and affect strongly the surface acidity. On SiO₂, vanadium species is usually in the form of polycrystalline V₂O₅ even for the catalyst with low loading (3%) and these V₂O₅ crystallites exhibit similar amount of Brönsted and Lewis acid sites. The 25%V₂O₅/SiO₂ catalyst possesses substantial amount of V₂O₅ crystallites on the surface with the initial heat of 105 kJ mol^-1 and coverage of about 600 mmol g^-1 for ammonia adsorption. Vanadia can be well dispersed on g-Al₂O₃and TiO₂ to form isolated tetrahedral species and polymeric two-dimensional network. Addition of vanadia on γ-Al₂O₃ results in the change of acidity from that associated with g-Al₂O₃ (mainly Lewis sites) to that associated with vanadia (mainly Brönsted sites) and leads to the decreased acid strength. The 3%V₂O₅/TiO₂ catalyst may have the vanadia structure of incomplete polymeric two-dimensional network that possesses the Ti-O-V-OH groups at edges showing strong Brönsted acidity with the initial heat of about 140 kJ mol^-1 for ammonia adsorption. On the other hand, the 10%V₂O₅/TiO₂ catalyst may have well defined polymeric two-dimensional vanadia network, possessing V-O-V-OH groups that exhibit rather weak Brönsted acidity with the heat of 90 kJ mol^-1 for NH₃ adsorption. V₂O₅ crystallites are formed on the 25%V₂O₅/TiO₂ catalyst, which exhibit the acid properties similar to those for 25%V₂O₅ on SiO₂ and γ-Al₂O₃.     

杂多酸催化剂在烷基化反应中的研究进展

介绍了杂多酸的结构性能,着重综述了近年来负载型杂多酸催化剂在烷基化反应中的应用和研究进展,并提出了几点展望.     

Dehydrogenation of cycloalkanes over noble metal catalysts supported on active carbon

Dehydrogenation of decalin to naphthalene through tetralin and that of dicyclohexyl to biphenyl through phenylcyclohexane with Pt/C and Pd/C was investigated mainly under the liquid film state, in which the catalyst was just wet but not suspended and covered with a thin film of liquid substrate. To improve the catalytic activities, the effects of the addition of tellurium into Pd/C were investigated to reveal that the combination of tellurium, palladium and conjugated systems produced during the dehydrogenation of cycloalkames was important to the improvement of the activities.     

The properties of supported rhenium catalysts in the dehydrogenation of cyclohexane

The 2 % Re/sibunite catalyst is more active than 2 % Re/-Al₂O₃ and 2 % Re/-Al₂O₃ catalysts in the dehydrogenation of cyclohexane into benzene (T = 350 °C,w = 0.5 h–1). The substitution of NH₄ReO₄ by HReO₄ in the preparation of the catalyst enhances its activity by a factor of 1.3. Treatment with HNO₃ or oxalic acid increases the selectivity by a factor of 1.2 and 1.35, respectively, the overall conversion of cyclohexane being 32–40 %.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 2119–2121, August, 1996.     

环己醇脱氢催化反应本征动力学研究

采用管式连续流动固定床积分反应器,对环己醇在Cu－Co/MgO催化剂上的脱氢反应本征动力学进行了研究,求出幂式速率模型各项参数,得到反应的表观活化能为44.28kJ/mol.将上述实验数据与由似平衡浓度法导出的速控步骤的数学模型相关联,求出各有关参数和物种的吸附烙.结果表明,以环己醇吸附和表面反应为速控步骤的模型可较好地进行关联.对上述模型进行了方差和残差分析,误差在宏观动力学研究允许范围内,实验无系统误差.方差分析表明,表面反应为速控步骤的模型对描述反应具有相对最小误差.     

Methodical aspects in the surface analysis of supported molybdena catalysts

Supported molybdena catalysts, with TiO₂, CeO₂ and Al₂O₃ supports, were studied by XPS and ISS. It was found that reliable results are obtained only when samples are calcined and transferred into the ultrahigh vacuum system without further contact with the ambient atmosphere (‘in situ calcination’). This applies also to catalysts that were previously calcined but had been stored in the ambient atmosphere. Supported Mo oxide becomes reduced under x‐ray irradiation during extended XPS data acquisition. A slight decrease of the Mo/support cation intensity ratio as a consequence of this reduction was detected by ISS in MoO₃/TiO₂ and MoO₃/CeO₂, therefore ISS analysis should be performed on freshly calcined samples without prior extended exposure to x‐rays. Because ISS spectra change rapidly due to sputtering, a correct analysis of the surface properties of the supported Mo catalyst requires extrapolation of the trend to the start of the experiment. It was established by this methodology that the surface of a 7% MoO₃/TiO₂ catalyst (5.3 Mo nm^?2) is completely covered by a monolayer of Mo oxide species, and no Ti cation is exposed. In a submonolayer MoO₃/CeO₂ catalyst the exposed support could be detected, as expected, whereas in an MoO₃/Al₂O₃ catalyst with an Mo oxide loading equal to the monolayer coverage a slight exposure of the Al support cation also was noted probably because of the high curvature of the smaller Al₂O₃ particles. Copyright © 2004 John Wiley & Sons, Ltd.