分散性催化剂作用下噻吩类化合物的临氢转化规律

以有机钼为前驱体制备了分散性纳米RDC-Mo催化剂，采用微型反应釜进行了噻吩类模型化合物噻吩、苯并噻吩和二苯并噻吩(DBT)热转化及RDC-Mo催化临氢热转化反应，对比了热转化及催化临氢过程噻吩类模型化合物热转化反应效果。采用X射线衍射(XRD)及高分辨率的透射电镜(HRTEM)对所制备的分散型催化剂进行了分析表征。采用模拟计算方法深入研究了分散型催化剂催化临氢热转化显著提高噻吩类化合物转化率以及不同结构噻吩类反应差异的内因。结果表明：制备的分散型催化剂RDC-Mo具有高度分散纳米尺寸特征，其晶粒尺寸为3.63 nm。相比于热转化，高分散纳米催化剂RDC-Mo作用的催化临氢过程显著强化了噻吩类化合物的转化，使其转化率大幅度提高。高分散度纳米催化剂显著强化了噻吩类化合物与催化剂活性中心、H₂的可接近性；H₂经纳米催化剂活化形成的氢自由基强化噻吩类化合物中与S相连的芳环碳定向加氢，促使C—S键断裂能垒大幅下降，在较低温发生断裂；该反应路径正是造成分散型催化剂临氢体系显著提高噻吩类化合物裂化转化率的内在原因。受定向加氢的概率、在活性中心MoS₂吸附难易以及定向加氢后C—S键键长变化3方面的影响，不同结构噻吩类化合物转化率由大到小顺序为苯并噻吩、噻吩、二苯并噻吩。

Study on thermal cracking reaction of thiophene model compounds in the presence of hydrogen and dispersed catalyst

Dispersed nano-catalyst RDC-Mo was prepared with organic molybdenum as the precursor. Thermal and catalytic hydro-thermal conversion of thiophene model compounds, i.e., thiophene, benzothiophene and dibenzothiophene (DBT), were studied with using a micro-autoclave, respectively. X-ray diffraction spectrum (XRD) and high-resolution transmission electron microscope (HRTEM) were used to characterize the prepared dispersed nano-catalyst. Simulation calculation was further applied to study the reasons why catalytic hydrogenation can significantly improve thiophene compounds conversion ratio, and the reaction differences of thiophenes with different molecular structures. Experimental results show that the dispersed catalyst RDC-Mo is nano-size and highly dispersed, and its crystal size is 3.63 nm. Compared with thermal cracking, catalytic hydrogenation process with highly dispersed nano-catalyst RDC-Mo can significantly improve thiophene compounds conversion ratio. In hydrogen catalytic system, highly dispersed nano-catalysts can greatly enhance the accessibility of thiophene compounds to the catalyst active centers and hydrogen. Hydrogen radicals formed by nano-catalyst activated hydrogen can directly make C—S bond hydrogenation occurred in the aromatic ring of thiophene compounds, and thus significantly reduce breaking energy and can make cracking reactions taking place at low temperatures. The above reaction mechanism is the reason why dispersed nano-catalyst can significantly improve conversion ratio of thiophene compounds. Based on steric probability of directional hydrogenation, difficulty of MoS2 adsorption in the active center and C—S bond length change after directional hydrogenation, under the same reaction conditions, conversion ratios of different structural thiophene compounds from high to low are benzothiophene， thiophene， dibenzothiophene.