新型分子筛上石脑油催化裂解多产低碳烯烃研究

CATALYTIC CRACKING OF NAPHTHA OVER NOVEL ZEOLITES FOR MAXIMIZING LIGHT OLEFINS YIELD

在固定床微反装置上对4种不同结构的分子筛HZSM-5,HIM-5,HEU-1,HAl-ITQ-13的石脑油催化裂解(NCC)反应性能进行对比评价。采用XRD、SEM、N 2吸附-脱附及Py-IR等方法表征各分子筛的孔道结构和酸性质。结果表明:与HZSM-5相比,石脑油在HIM-5,HEU-1,HAl-ITQ-13作用下催化裂解反应的转化率均有所提高;孔径较小、酸量较低的HAl-ITQ-13和HEU-1具有较高的催化活性,其作用下的低碳烯烃(乙烯+丙烯+丁烯)收率分别比HZSM-5提高13.3百分点和8.6百分点;而在HIM-5作用下的低碳烯烃收率则比HZSM-5降低3.5百分点。同时,考察了NCC反应条件下丙烯的反应性能,发现丙烯在NCC反应条件下具有非常高的反应活性,可通过催化反应转化为乙烯、丙烷、丁烯等产物。抑制氢转移反应有利于提高低碳烯烃的收率,开发NCC新型催化材料时,应综合考虑分子筛的酸性质和孔道结构对低碳烯烃二次反应的抑制作用。

Catalytic cracking of naphtha(NCC)was carried out in a fixed bed micro-activity test unit.A series of zeolites with different pore structures was investigated,namely HZSM-5,HIM-5,HEU-1 and HAl-ITQ-13.The structural and acidic properties of these zeolites were characterized by XRD,SEM,N 2 adsorption-desorption and Py-IR.The results showed that HAl-ITQ-13,HEU-1 and HIM-5 increased the naphtha conversion compared to HZSM-5.The light olefins(ethylene+propylene+butylene)yield of HAl-ITQ-13 and HEU-1 increased 13.3 and 8.6 percentage points respectively,compared with HZSM-5.High catalytic activities of HAl-ITQ-13 and HEU-1 were ascribed to smaller pore size and lower concentration of acid sites.HIM-5 can not stimulate the production of light olefins with the light olefins yield lower than HZSM-5 by 3.5 percentage points.Additionally,the reactivity of propylene under NCC reaction conditions was investigated.It was found that propylene was an active product under NCC reaction conditions.The main products of propylene catalytic transformation included ethylene,propane,butylene.The suppression of hydrogen transfer reactions was critical for maximizing light olefins yield.When developing NCC new materials,the structural and acidic properties of zeolites should be considered thoroughly due to their great effects on the secondary reactions.