Catalytic Oxidative Dehydrogenation and O_2-Free Dehydrogenation of Isobutane on Some Molybdates

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二氧化碳氧化丙烷制丙烯催化反应的研究铬镁铝复合氧化物催化剂的制备、表面微量吸附量热及催化性能

以共沉淀法合成的铬镁铝类水滑石为前体,制备了一系列不同原子比的铬镁铝复合氧化物,研究了其对二氧化碳氧化丙烷制丙烯反应的催化性能.采用微量吸附量热技术,以CO2和NH3为探针分子定量地表征了样品表面酸碱中心的强度和数量,并与其催化性能进行了关联.结果表明,Cr:Mg:Al原子比为1:1:1的催化剂具有较大的比表面积(94.5m2/g),样品中Mg(Al1.5Cr05)O4物相的含量最多.样品表面存在数量较多强度较强的酸性中心和数量最少强度较弱的碱性中心,对NH3吸附,它的吸附热为145 kJ/mol,吸附覆盖度为3.55μmol/m2;对CO2吸附,它的吸附热为115kJ/mol,吸附覆盖度为0.063μmol/m2.该样品的催化活性最高,在温度为650℃,CO2/C3H8摩尔比为3.6,GHSV(C3H8)为3000 h-1时,C3H8的转化率为22.8%,C3H6的选择性为83.5%,收率为19.1%.     

Pt-Sn/MgAl2O4催化剂的TPR和H2-TPD研究

Pt Sn/MgAl 2O 4 catalysts prepared by co impregnation with nominal 0 35% platinum and varying content of tin (0～2 5%) were characterized by temperature programmed reduction (TPR) and temperature programmed desorption of hydrogen (H 2 TPD). TPR results showed that platinum catalyzed the reduction of tin. However, the average oxidation state of tin after reduction depended upon the concentration of tin on the catalysts. H 2 TPD data indicated that tin addition inhibited the inactivated adsorption of hydrogen but promoted the activated adsorption, implying that tin modified both the ensembles of platinum and metal support interface, thus increasing hydrogen mobility and promoting hydrogen spillover.     

Effect of the nature of zeolite and modifying additives on the activity of zeolite-containing catalysts inn-butane isomerization

Isomerization ofn-butane on various types of zeolites (ZVM, ZVK, mordenite, and Y) modified with transition metals and cationic and anionic additives was investigated. Under the conditions studied, H-forms of zeolites are inactive. Pt-containing systems based on the H-form of ZVM (HZVM) are the most efficient catalysts forn-butane isomerization, and the yield of isobutane reaches 20–26 wt.% at a selectivity of 40–45%. Modification of this catalyst with Ga and Fe compounds or with an aqueous solution of HCl increases the selectivity with respect to isobutane up to 70–90%. Introduction of Zn²⁺ cations or F⁻ and SO₄ ²⁻ anions into the Pt-containing HZVM system decreases the selectivity and yield of isobutane due to the formation of very strong acidic centers on which disproportionation and hydrocracking ofn-butane mainly occur. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1281–1285, July, 1999.