MCM-41担载的Pd催化剂加氢脱硫反应性能

HYDRODESULFURIZATION PERFORMANCE OF MCM-41 SUPPORTED Pd CATALYSTS

以含0.8%(质量分数)二苯并噻吩(DBT)的十氢萘溶液为模型化合物,考察了Si-MCM-41、Al-MCM-41和Si-MCM-41与HY机械混合物(MY)担载的Pd催化剂加氢脱硫(HDS)反应性能,并采用XRD、N2吸附和吡啶吸附红外光谱(Py-IR)方法对载体进行了表征。结果表明,Al-MCM-41表面酸中心以L酸为主,MY表面主要为B酸;而Si-MCM-41的酸性较弱。DBT在这些担载型Pd催化剂上主要通过预加氢反应路径脱硫,催化剂活性顺序为:Pd/Al-MCM-41>Pd/MY>Pd/Si-MCM-41。提高载体的酸性显著提高了催化剂的加氢脱硫活性,但对其直接脱硫活性影响不大。从DBT的HDS产物分布来看,Pd/Al-MCM-41具有较高的脱硫活性和异构化活性以及较低的加氢裂化活性;而Pd/MY表现出较高的加氢裂化活性,但脱硫活性相对较低,并且失活较快。二者在反应性能上的差异可能与Al-MCM-41和MY孔道结构和表面酸中心分布不同有关。具有良好介孔孔道结构和较高L酸与B酸比例的Al-MCM-41是一种优良的贵金属HDS催化剂载体。

The hydrodesulfurizations （HDS） of dibenzothiophene （DBT） catalyzed by Pd catalysts supported on Si-MCM-41, Al-MCM-41 and the mechanical mixture of Si-MCM-41 and HY （MY） were studied by using a model fuel containing 0.8%（mass fraction） DBT in decalin. The supports were characterized by means of XRD, N2 adsorption and pyridine infrared spectroscopy （Py-IR）. The results indicated that Al-MCM-41 possessed mainly Lewis acid sites and MY contained mainly Br6nsted acid sites, while Si-MCM-41 showed low acidity. The DBT HDS over these supported Pd catalysts predominately took the route of hydrogenation （HYD）, and their activities decreased in the order of Pd/Al-MCM-41〉Pd/MY〉Pd/Si-MCM-41. The HYD activity of the supported Pd catalysts was significantly improved by the increase of the acidity in the supports, but their direct desulfurization （DDS） activity was hardly affected. The HDS product distribution revealed that Pd/Al-MCM-41 exhibited high desulfurization and isomerization activities and low hydrocracking activity, whereas Pd/MY showed a high hydrocracking activity but a relatively low desulfurization activity and deactivated quickly. Difference in the HDS performances of Pd/Al-MCM-41 and Pd/MY can be attributed to the difference in the pore structures and acidic properties of Al-MCM-41 and MY. Al-MCM-41, which possessed an ordered mesoporous structure and a high ratio of Lewis acid sites to Br6nsted acid sites, is a promising support for noble metal HDS catalyst.