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

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。

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

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-5 catalysts 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 framework.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.