Process for separating by absorption the pyrolysis gas from preparation of lower carbon olefins

摘要

The provided is a process for separating by absorption the pyrolysis gas from preparation of lower carbon olefins, wherein a primary absorbent and a secondary absorbent are introduced into the demethanizer to separate by absorption the feedstock of the demethanizer through countercurrent contact therewith at a moderate temperature and pressure, thereby to obtain a top fraction primarily comprising hydrogen and methane and a bottom fraction primarily comprising the absorbents and C2+ fraction, wherein the primary absorbent essentially is a mixed Cn or Cn+ fraction, the secondary absorbent essentially is a Cn′ alkane fraction or mixed Cn′ or Cn′+ fraction, and wherein n and n′ are independently 3, 4 or 5 with the proviso when the secondary absorbent is a mixed fraction, n′ is not 3.

主权项

1. A process for separating by absorption a pyrolysis gas from a preparation of lower carbon olefins, the process comprising introducing a primary absorbent and a secondary absorbent into a demethanizer and separating by absorption a feedstock of the demethanize through countercurrent contact at a moderate temperature and pressure, wherein the feedstock is introduced at the middle or the bottom of the demethanizer, the primary absorbent is introduced at the middle of the demethanizer only, or at the middle and at the bottom of the demethanizer simultaneously, the second absorbent is introduced at the top of the demethanizer, and wherein the primary absorbent and the secondary absorbent are introduced into the demethanizer at a total mass flowrate ratio of the primary absorbent to the secondary absorbent of 10-1.05, thereby obtain top fraction primarily comprising hydrogen and methane and a bottom fraction primarily comprising the primary and secondary absorbents and a C2+ fraction,
wherein: the primary absorbent essentially is a mixed Cn or Cn+ fraction; the secondary absorbent essentially is a Cn′ alkane fraction or mixed Cn′ or Cn′+fraction; and n and n′ are independently 3, 4 or 5, with the proviso that when the secondary absorbent is a mixed fraction, n′ is not 3.