镁磷物质的量比对NiW/MgAPO-5催化剂选择性催化四氢萘加氢裂化制BTEX性能的影响

Effect of Mg/P mol ratio on the catalytic performance of NiW/MgAPO-5 in the hydrocracking of tetralin to BTEX

以水热法合成的一系列镁磷物质的量比不同的MgAPO-5分子筛为载体,采用等体积共浸渍的方法制备NiW/MgAPO-5催化剂。采用X射线衍射(XRD)、N_2物理吸附、扫描电子显微镜(SEM)、氨气程序升温脱附(NH_3-TPD)、吡啶吸附红外光谱(Py-FTIR)和氢气程序升温还原(H_2-TPR)对载体和负载型催化剂进行了表征。以四氢萘为模型化合物,在小型固定床上考察了不同镁磷物质的量比的催化剂加氢裂化制BTEX性能。结果表明,Mg/P(mol ratio)对MgAPO-5载体的晶相、镁含量、形貌和酸性质产生显著的影响,并且Mg^(2+)引入到了分子筛骨架。催化性能评价结果表明,NiW负载量相同时,四氢萘的转化率由载体MgAPO-5的酸强度决定,而BTEX的选择性在载体酸性和催化剂加氢组分相匹配处达到最优。当Mg/P(mol ratio)为0.05时,四氢萘的转化率最高,而BTEX的选择性则在Mg/P(mol ratio)为0.03时达到最大。

A series of MgAPO-5 molecular sieves with a wide range of Mg/P mol ratios in the gel was synthesized by a hydrothermal process. Using MgAPO-5 as acidic supports,the bifunctional NiW/MgAPO-5catalysts were prepared by impregnation method,and applied to the hydrocracking of tetralin to produce BTEX.The synthesized MgAPO-5 molecular sieves and NiW/MgAPO-5 samples were characterized by XRD,N2 adsorption,SEM,NH3-TPD,Py-FTIR and H2-TPR. The results exhibit that the Mg/P mol ratio has a great influence on the unit cell parameters,morphology,the Mg content and the acidity of MgAPO-5 samples,and the ion of Mg2＋is incorporated into the framew ork. In the hydrocracking of tetralin,with the same amount of NiW,the activity of NiW/MgAPO-5 is primarily controlled by the acidic strength of MgAPO-5. The selectivity of BTEX was determined by the combined effect of the acidity of MgAPO-5 and the（ de） hydrogenation function of NiW. The highest conversion is achieved with the Mg/P mol ratio of 0. 05,and the best BTEX selectivity is obtained with the Mg/P mol ratio of 0.03.