乙烷在纳米氧化镍上温和氧化脱氢制乙烯

用溶胶-凝胶法制备的纳米氧化镍具有较好的乙烷氧化脱氢低温反应活性.380℃下焙烧的NiO粒子大小在8 nm左右,与大尺寸氧化镍相比,获得相同收率时反应温度大约下降125℃.并通过BET,TPR,TPD,XPS等手段对不同焙烧温度的氧化镍催化剂进行表征,研究其粒子大小与对氧的活化能力及反应活性的关联.     

纳米NiO催化乙烷低温氧化脱氢制乙烯

 用溶胶-凝胶法制备了纳米氧化镍。TEM结果表明，在380℃下焙烧的氧化镍粒子大小在10 nm以下。与大尺寸氧化镍相比，纳米氧化镍对乙烷氧化脱氢反应的催化性能有较大的改善，在获得相当收率时反应温度大约下降125℃。关于热点问题，可以通过催化剂与石英沙混合得到解决。     

Investigation on High Efficient Catalysts for the Oxidative Dehydrogenation of Ethane

Since the pioneer work of Thorsteinson fot me ox(?) ethane, a series of V-Mo based catalysts mainly for the oxidative dehydrogenation of ethane have been patented. On the surfaces of these catalysts, a C_2H_4 selectivity of 70％ was achieved, but the space velocity was only about 340 h~(-1). Lunsford, et al. reported a C_2H_6 conversion of 75％ and a C_2H_4 selectivity of 76％ over the     

负载型氧化镍催化剂上的乙烷氧化脱氢TiO2对Al2O3载体的改性作用

自从丁烷取代苯制顺厅烯二酸酐工业化以来,低碳烷烃的选择氧化越来越受到重视.     

乙烷氧化脱氢制乙烯反应中制备方法及助剂对镍基催化剂性能的影响

采用不同方法制备了镍基催化剂,并考察了乙烷氧化脱氢制乙烯(ODE)的反应活性,结果表明,在3种不同制备方法的催化剂上,ODE反应的活性及产物选择性存在明显差异,浸渍法制备的催化剂性能最佳.在相同的条件下,以共浸渍法引入CeO2助剂后,N iO/-γA l2O3催化剂上的低温选择氧化活性显著提高,而目的产物C2H4的选择性变化不大.XRD,还原TG和XPS对催化剂进行表征的结果显示:反应的活性物相可能是易于还原的高度分散于催化剂表面的微晶N iO和表面尖晶石N iA l2O4物相;高分散的微晶N iO,类似于纯N iO,有利于ODE反应低温选择氧化生成目的产物C2H4,而易还原的表面尖晶石N iA l2O4物相的存在则可能是在高温下获得高选择氧化活性和选择性的主要原因之一.     

Surface Acidity／Basicity and Catalytic Reactivity of CeO2／γ—A12O3 Catalysts for the Oxidative Dehydrogenation of Ethane with Carbon Dioxide to Ethylene

Dehydrogenation of ethane to ethylene in CO2 was investigated over CeO2/γ-Al2O3 catalysts at 700℃ in a conventional flow reactor operating at atmospheric pressure. XRD, BET and microcalorimetric adsorption techniques were used to characterize the structure and surface acidity/basicity of the CeO2/γ-Al2O3 catalysts. The results show that the surface acidity decreased while the surface basicity increased after the addition of CeO2 to γ-Al2O3. Accordingly, the activity of the hydrogenation reaction of CO2 increased, which might be responsible for the enhanced conversion in the dehydrogenation of ethane to ethylene. The highest ethane conversion obtained was about 15% for the 25?O2/γ-Al2O3. The selectivity to ethylene was high for all the CeO2, γ-Al2O3 and CeO2/γ-Al2O3 catalysts.     

Heterogeneously Catalysed Oxidative Dehydrogenation of Menthol in a Fixed-Bed Reactor in the Gas Phase

For the first time, the oxidative dehydrogenation of (−)-menthol to (−)-menthone and (+)-isomenthone in a marketable quality was carried out in a continuous gas phase reactor as a sustainable process using molecular oxygen as green oxidant and solid catalysts which do not contaminate the product mixture and which are easily to remove. The diastereomeric purity remained largely unchanged. Three types of catalysts were found to be very active and selective in the formation of menthone and isomenthone: AgSr/SiO₂, CuO distributed on a basic support and RuMnCe/CeO₂, where Ru, Mn and Ce exist in an oxidized state. The best overall yield of menthon/isomenthone obtained with an Ag-based catalyst was 58 % at 64 % selectivity, with a Cu-based catalyst 41 % at 51 % selectivity and with a Ru-based catalyst 68 % at 73 % selectivity. Reaction conditions were widely optimized.     

Surface Acidity/Basicity and Catalytic Reactivity of CeO2/γ-Al2O3 Catalysts for the Oxidative Dehydrogenation of Ethane with Carbon Dioxide to Ethylene

Dehydrogenation of ethane to ethylene in CO2 was investigated over CeO2/γ-Al2O3 catalysts at 700 ℃ in a conventional flow reactor operating at atmospheric pressure. XRD, BET and microcalorimetric adsorption techniques were used to characterize the structure and surface acidity/basicity of the CeO2/γ-Al2O3 catalysts. The results show that the surface acidity decreased while the surface basicity increased after the addition of CeO2 to γ-Al2O3. Accordingly, the activity of the hydrogenation reaction of CO2 increased, which might be responsible for the enhanced conversion in the dehydrogenation of ethane to ethylene. The highest ethane conversion obtained was about 15% for the 25%CeO2/γ-Al2O3. The selectivity to ethylene was high for all the CeO2, γ-Al2O3 and CeO2/γ-Al2O3 catalysts.     

激光促进Pb和Bi磷酸盐表面上异丁烷氧化脱氢反应

采用沉淀法制备了Pb₃(PO₄)₂和BiPO₄固体材料,用XRD,IR,TPD和LSSR等手段对Pb₃(PO₄)₂和BiPO₄的晶体结构、表面构造、化学吸附性能和激光促进异丁烷氧化脱氢反应性能进行了研究.结果表明,固体材料表面由Lewis碱位P＝O和P-O-M(Pb或Bi)键中的O^2-及Lewis酸位Pb²⁺或Bi³⁺构成;异丁烷分子中两个甲基中的H分别吸附在两个相邻的Lewis碱位P＝O上,形成双位分子吸附态;在常压和200℃条件下,用一定频率的激光激发固体表面P＝O键,发生异丁烷氧化脱氢反应,产物异丁烯的选择性大于95%,在激光促进表面反应体系中,激光能量的利用率主要取决于固体材料的振动结构和对反应物分子的吸附能力,反应产物的选择性主要决定于反应物分子在固体表面上的吸附态.     

Dehydrogenation of Propane to Propylene in the Presence of CO2 over Steaming‐treated HZSM‐5 Supported ZnO

Dehydrogenation of propane to propylene over zinc oxide catalysts supported on steaming‐treated HZSM‐5 in the presence of CO₂ has been investigated. The highest catalytic performance can be achieved on the 5%ZnO/HZSM‐5(650) catalyst with the HZSM‐5 support steaming at 650°C, which allows the maximum propylene yields of 29.7% and 20.3% at the initial and steady states, respectively, in the catalytic dehydrogenation of propane at 600°C. The superior catalytic performance of this catalyst can be attributed to high dispersion of ZnO and appropriate Br?nsted acidity of the HZSM‐5(650) support. The catalytic stability is enhanced by the addition of CO₂ to the feed gas due to the suppression of coke formation.     

Highly Efficient Direct Aerobic Oxidative Esterification of Cinnamyl Alcohol with Alkyl Alcohols Catalysed by Gold Nanoparticles Incarcerated in a Nanoporous Polymer Matrix: A Tool for Investigating the Role of the Polymer Host

The selective aerobic oxidation of cinnamyl alcohol to cinnamaldehyde, as well as direct oxidative esterification of this alcohol with primary and secondary aliphatic alcohols, were achieved with high chemoselectivity by using gold nanoparticles supported in a nanoporous semicrystalline multi‐block copolymer matrix, which consisted of syndiotactic polystyrene‐co‐cis‐1,4‐polybutadiene. The cascade reaction that leads to the alkyl cinnamates occurs through two oxidation steps: the selective oxidation of cinnamyl alcohol to cinnamaldehyde, followed by oxidation of the hemiacetal that results from the base‐catalysed reaction of cinnamaldehyde with an aliphatic alcohol. The rate constants for the two steps were evaluated in the temperature range 10–45 °C. The cinnamyl alcohol oxidation is faster than the oxidative esterification of cinnamaldehyde with methanol, ethanol, 2‐propanol, 1‐butanol, 1‐hexanol or 1‐octanol. The rate constants of the latter reaction are pseudo‐zero order with respect to the aliphatic alcohol and decrease as the bulkiness of the alcohol is increased. The activation energy (E_a) for the two oxidation steps was calculated for esterification of cinnamyl alcohol with 1‐butanol (E_a=57.8±11.5 and 62.7±16.7 kJ mol^?1 for the first and second step, respectively). The oxidative esterification of cinnamyl alcohol with 2‐phenylethanol follows pseudo‐first‐order kinetics with respect to 2‐phenylethanol and is faster than observed for other alcohols because of fast diffusion of the aromatic alcohol in the crystalline phase of the support. The kinetic investigation allowed us to assess the role of the polymer support in the determination of both high activity and selectivity in the title reaction.