环己烷气固相催化氧化制取顺酐及醋酸的固体催化剂研究

【作者】 张海洲；

【导师】 蔡炳新；

【作者基本信息】 湖南大学 ， 物理化学， 2003， 硕士

【摘要】 本文主要通过沉淀法、共沉淀法和浸渍法制备了不同的催化剂前驱体，采用不同的活化方法，得到了不同类型的固体催化剂。以气态环己烷催化氧化制顺丁烯二酸酐和醋酸为目标反应，对各种催化剂进行了性能考察。催化反应在常压微型固定床反应器中进行，氧源来自氮、氧混合气，气态环己烷由氮气带入反应器。实验发现，在不同的催化剂上，虽然环己烷都主要转化为顺丁烯二酸酐和醋酸，但是环己烷的转化率和产物顺酐及醋酸的选择性的大小均有很大的差异。 实验表明不同晶相的VPO催化剂中以结晶度较高的（VO）₂P₂O₇相催化剂表现出很高的选择性；主体晶相同为（VO）₂P₂O₇的催化剂，因催化剂前驱体的制备方法及活化条件不同，催化性能相差悬殊；添加铈锆复合氧化物能有效地改善（VO）₂P₂O₇催化剂的催化性能；采用浸渍法添加适量的钼组份能有效地改善（VO）₂P₂O₇催化剂的催化性能，而采用共沉淀法添加钼组份却显著地降低了（VO）₂P₂O₇催化剂的催化性能；不同的载体和磷钒比都对催化剂的催化性能产生了显然不同的影响。 通过改变反应温度、空速、原料气中的氧含量和环己烷浓度等条件，对不同催化剂的催化性能进行了评价，结果表明：不同类型的催化剂，为了达到各自的最佳催化性能，必需满足各自不同的最适反应条件。 根据不同反应条件下的实验结果，结合XRD谱、IR谱和钒平均价态数，对导致不同结果的原因进行了探讨，我们认为良好的环己烷选择性部分氧化制取顺酐及醋酸的固体催化剂，需拥有适宜的V^Ⅴ／V^Ⅳ比、V^Ⅳ以结晶良好的（VO）₂P₂O₇形态存在，以便有效地稳定钒的价态，从而构成有效的V^Ⅳ-V^Ⅴ-V^Ⅳ循环。最后拟定了催化反应进行的可能性机理，并对其作出了初步解释。更多还原

【Abstract】 Various solid catalysts are obtained by calcination of precursors prepared by precipitation, coprecipitation and impregnation method in this paper. The catalytic properties are studied to aim at acquiring maleic anhydride and acetic acid from cyclohexane. The catalytic reactions are processing in the bed-secured micro-reactor under normal pressure. The oxygen reagent comes from the mixture of oxygen and nitrogen while gas-cyclohexane is put into reactor by nitrogen. The experiment indicated that cyclohexane mainly transformed into maleic anhydride and acetic acid on various but there exist a great deal of difference in the conversion of cyclohexane and selectivity of the products.The experiment manifested the (VO)2P2O7 catalyst with high crystallization occupied higher selectivity in various VPO catalysts. The catalysts whose main crystalline phase are (VO)2P2O7 exhibit different catalytic properties because of different precursors and activated ambience. The doping with an appropriate amount of Ce-Zr composite oxide can significantly improve the catalytic performance of (VO)2P2O7 catalyst. The appropriate amount of incorporated molybdenum by impregnation can improve the catalytic performance of (VO)2P2O7 catalyst ,whereas when the promoter is added by coprecipitation ,the selectivity to products is lower than in the unpromoted catalyst. The catalysts, which hold different carrier and ratio of V/P performance very differently.The evaluation of catalysts under various temperatures, space velocity and the concentration of oxygen and cyclohexane indicated that the appropriate condition must be fulfilled in order to meet the optimization of catalytic properties.The reasons why various catalysts performance differently are discussed in view of the result of evaluation experiment, XRD, FT-1R and the average value of vanadium It is regarded that the good catalysts on which cyclohexane transformed into maleic anhydride and acetic acid must possess optimum ratio of vV/VIV while VIV existed in the phase of (VO)2P2O7 as more as possible, in order to form the effective circulation of VIV-VV-VIV. The possible mechanism of catalytic reaction is advanced and the initial explanation is given in the last更多还原