分离石脑油馏分组成优化乙烯原料

SEPARATING GROUP COMPOSITIONS IN NAPHTHA TO IMPROVE OLEFIN YIELDS OF STEAM CRACKING PROCESS

为了改进乙烯原料,提高乙烯收率,分别选取正构烷烃、异构烷烃、环烷烃和芳烃为裂解原料,考察模型化合物的蒸汽裂解产物分布,并分别采用分子筛吸附分离和溶剂萃取两种工艺,提出了可以适应三种目的烯烃产品不同比例需求的裂解制乙烯原料分子生产路线。在典型的裂解工艺条件下石脑油中的正构烷烃对裂解产物中乙烯的贡献最大,异构烷烃是产生丙烯的主要来源,而环烷烃主要生成丁二烯,芳烃很难裂解生成烯烃。通过吸附分离工艺富集石脑油中的正构烷烃,富含正构烷烃的脱附油蒸汽裂解制乙烯收率与不富集石脑油原料相比可提高13%。通过溶剂萃取将芳烃和环烷烃从石脑油中萃出,萃余油蒸汽裂解制乙烯和丙烯收率与未萃取石脑油原料相比分别提高3.0%和1.5%。分子筛吸附分离和溶剂萃取工艺相结合可以显著提高裂解烯烃收率。

In order to improve the steam cracking feeds and increase the ethylene yield, several model compounds including normal paraffins, iso-paraffins, cyclanes and aromatics were selected as the feeds of steam cracking process and the olefin yields were investigated. In the typical reaction conditions, the normal paraffins in the naphtha contribute most to the ethylene in the products; the iso-paraffins are the main sources of propylene; cyclanes mainly produce the butadiene; and aromatics can hardly produce olefins. According to this, the adsorption and solvent extraction processes were adopted to properly separate the group compositions in naphtha to optimize the cracking feeds. The n-paraffins in naphtha were gathered through adsorption process using 5A molecular sieves. The ethylene yield improved by 13 percent using the desorption oil rich in n-paraffins as the cracking feed. The aromatics and the cyclanes were extracted from the naphtha. Compared with naphtha, the ethylene and propylene yields of the extraction raffinate oil were 3.0% and 1.5% higher, respectively. Combining the adsorption and extraction processes, the olefin yield of steam cracking process can he dramatically improved.