基质与分子筛的协同作用及重油分子裂化历程研究

STUDY ON SYNERGY OF ZEOLITE AND MATRIX AND PROCESS OF HEAVY OIL CRACKING

在固定床反应器上,以磷酸改性的含氧化铝高岭土材料为基质,以ReUSY为分子筛组分,通过基质与分子筛分层填装以及部分机械混合的方式,考察不同装填顺序及混合程度对产品分布的影响,研究了催化裂化催化剂基质与分子筛之间的相互作用以及重油分子裂化反应历程。试验结果表明:基质对于重油大分子存在预裂化作用,重油分子首先与基质接触时,其转化率以及总液体收率均高于先经过分子筛体系;分子筛与基质各自所具备的特点均无法有效促使重油分子转化,当二者相互混合、共同作用于重油裂化时,目的产物收率明显增多且氢的分配也更为合理,说明基质与分子筛表面活性位存在良好的协同关系;基质及分子筛表面发生的重油裂化反应以经典裂化机理为主,但存在质子裂化路径。

The synergy of zeolite and matrix and the VGO cracking routes were studied by a fixed- bed reactor in which ReUSY zeolite and phosphoric acid modified alumina kaolin as matrix were loaded in different layered or mixed packing ways. It is observed that contacting the matrix first for heavy oil results in a higher conversion compared with that of contacting zeolite first. However,neither the molecular sieve nor the matrix along can make the heavy oil convert effectively. This indicates the preliminary cracking functions of the matrix, resulting in synergistic effect of zeolite and matrix. With the mixing degree of zeolite and matrix increase, the conversion and the liquid product yield rises significantly, while the yields of dry gas and coke decrease slightly. The synergy effect of mixing zeolite and matrix was also discussed in view of the hydrogen distribution in dry gas and LPG products. The data obtained in this work well fit the classic cracking mechanism, but existing protolytic cracking path which contributes to a rise in dry gas yield.