【作者】 申群兵；

【导师】 朱子彬；

【作者基本信息】 华东理工大学 ， 化学工艺， 2010， 博士

【摘要】 采用催化加氢脱烷基技术将重芳烃转化生成苯、甲苯、二甲苯(合称BTX)等基本石油化工产品,是提高重芳烃利用率的重要途径。本文对负载金属氧化物和贵金属的分子筛催化剂上C9+重芳烃加氢脱烷基制备BTX反应进行了研究。首先对C9+重芳烃加氢脱烷基反应体系进行了热力学分析,然后对用于该反应体系催化剂的分子筛载体HZSM-5和氧化物载体γ-Al2O3进行了比较,在此基础上借助XRD、H2-TPR、N2吸附、NH3-TPD以及吡啶吸附红外光谱等表征手段,系统研究了分子筛载体、活性组分、活性组分负载量、活性组分复合以及浸渍顺序等对催化剂物性结构和催化性能的影响,筛选出催化性能优良的NiO/HMCM-56催化剂。此外,以偏三甲苯为模型反应物,对NiO/HMCM-56上加氢脱烷基反应机理进行了探索性研究。热力学分析结果表明,C9+重芳烃加氢脱烷基反应体系中加氢脱烷基反应最易发生,为不可逆反应,其平衡常数远大于异构化反应、烷基转移反应和歧化反应。对于C9+重芳烃加氢脱烷基反应,负载于HZSM-5分子筛载体上的金属氧化物催化剂的催化性能优于负载于y-Al2O3载体上的催化剂。不同分子筛为载体的NiO和MoO3催化剂的催化性能表明,HMCM-56是适用于C9+重芳烃加氢脱烷基反应的优良载体。对于NiO催化剂,NiO与分子筛载体间的相互作用适中时催化剂具有相对较高的BTX选择性；对于MoO3催化剂,分子筛孔道内与B酸位相互作用的Mo物种的存在极大地降低了反应的BTX选择性。B酸的存在、L酸酸强度的增强、酸量的增加以及比表面积的增大均有助于提高加氢脱烷基反应的C9+芳烃转化率。对活性组分的研究结果表明,负载不同金属氧化物的HMCM-56催化剂中,NiO/HMCM-56催化性能最为优异；NiO负载量对NiO/HMCM-56催化性能的影响规律与NiO的加氢功能、催化剂酸性以及NiO在HMCM-56表面的分散状态有关；适宜的NiO负载量为3wt%-6wt%,对于6wt%NiO/HMCM-56催化剂,C9+芳烃转化率可达72.75mol%,BTX选择性为78.51mol%,BTX收率可达57.1lmol%；对于含有贵金属的二元复合活性组分催化剂Re-NiO/HMCM-56,活性组分Re与NiO的复合对催化剂物性结构和催化性能具有显著的影响,而两者浸渍顺序对其影响较小。NiO/HMCM-56催化剂上以偏三甲苯为模型反应物的加氢脱烷基反应机理研究结果表明,主反应加氢脱烷基反应由L酸中心催化,按照自由基反应机理进行；歧化反应由B酸中心催化,按照双分子碳正离子反应机理进行；异构化反应由B酸中心催化,按照单分子和双分子碳正离子反应机理进行；加氢裂解反应则经过芳烃在金属中心上苯环加氢生成环烷烃以及环烷烃在B酸和L酸中心上开环裂解生成低碳烷烃两步反应而完成。更多还原

【Abstract】 Catalytic hydrodealkylation of heavy aromatics to produce benzene (B), toluene (T) and xylenes (X) which are the three basic aromatic starting reactants is an important approach to improve the utilization of heavy aromatics. In this thesis, hydrodealkylation of C9+ heavy aromatics to produce BTX over zeolite-supported metal oxide and noble metal catalysts was studied. Firstly, the thermodynamics analysis for the hydrodealkylation system of C9+heavy aromatics was accomplished. Then the comparation in catalytic performance between HZSM-5-supported metal oxide catalysts andγ-Al2O3-supported metal oxide catalysts applied to this reaction system was carried out. Based on the preferred support type, the effect of zeolite support, active component, loading of active component, recombination of active components and impregnation sequence on physical and structural properties and catalytic performance of the employed hydrodealkylation catalysts was systematically investigated by means of XRD, H2-TPR, N2 adsorption and desorption, NH3-TPD and FTIR spectrum of adsorbed pyridine. And the NiO/HMCM-56 catalyst was developed and selected with its excellent catalytic performance. Moreover,1,2,4-trimethylbenzene was employed as the model reactant and the reaction mechanism of hydrodealkylation of 1,2,4-trimethylbenzene over the NiO/HMCM-56 catalyst was further studied.The thermodynamics analysis indicates that the main reactions of hydrodealkylation are irreversible reactions and most liable to occur with their equilibrium constants far greater than those of isomerization, transalkylation and disproportionation among the hydrodealkylation system of C9+heavy aromatics.For the hydrodealkylation process of C9+heavy aromatics feedstock employed in this thesis, the catalytic performance of metal oxide catalysts with HZSM-5 zeolite as support is superior to that withγ-Al2O3 as support.The catalytic performance of zeolite-supported nickel oxide and molybdenum oxide catalysts indicates that the HMCM-56 zeolite is an excellent support used to hydrodealkylation of C9+heavy aromatics. For zeolite-supported nickel oxide catalysts, the samples with the moderate interaction between NiO and zeolite exhibit the relatively high selectivity. And for zeolite-supported molybdenum oxide catalysts, the presence of the molybdenum species located in the channels of zeolite and associated with Br(?)nsted acid site causes the remarkable reduction of selectivity of BTX. The presence of Br(?)nsted acid sites, the growth of the strength of Lewis acid sites, the increase of acid amount and the accretion of specific surface area can all enhance the conversion of C9+aromatics in hydrodealkylation of heavy aromatics.The experimental results about investigation of active components indicate that among the HMCM-56-supported catalysts with different metal oxides as active components in this thesis, the NiO/HMCM-56 catalyst shows the greatest overall catalytic performance. The effect of NiO loading on the catalytic activity of NiO/HMCM-56 is related to the dehydrogenation-hydrogenation function of NiO, the acidity of catalysts and the dispersion state of NiO on the surface of HMCM-56. And the suitable NiO loading is 3wt%-6wt%. For the 6wt% NiO/HMCM-56 catalyst, the conversion of C9+aromatics is 72.75mol%, the selectivity of BTX is 78.51mol% and the yield of BTX is 57.11mol%. For the binary composite catalyst of Re-NiO/HMCM-56 containing noble metal Re, the recombination of Re and NiO active components has a great effect on physical and structural properties and catalytic performance of Re-NiO/HMCM-56, whereas the impregnation sequence of Re and NiO has little effect.The reaction mechanism of hydrodealkylation of 1,2,4-trimethylbenzene over the NiO/HMCM-56 catalyst shows that the main reaction of hydrodealkylation is catalyzed by Lewis acid sites and accomplished through a radical mechanism. Disproportionation is catalyzed by Br(?)nsted acid sites and accomplished through a bimolecular carbenium ion chain mechanism while isomerization is catalyzed by Br(?)nsted acid sites and accomplished through monomolecular and bimolecular carbenium ion chain mechanisms. And catalytic hydrocracking requires the hydrogenation of the aromatic ring over metal sites in a first step to produce naphthenes, which rapidly undergo cracking on the Bronsted acid sites and Lewis acid sites to produce light paraffins.更多还原