PROCESS FOR CATALYTIC CONVERSION OF LOW VALUE HYDROCARBON STREAMS TO LIGHT OLEFINS

摘要

A process for catalytic conversion of low value hydrocarbon streams to light olefins in comparatively higher yields is disclosed. Propylene is obtained in amounts higher than 20 wt. % and ethylene higher than 6 wt. %. The process is carried out in a preheated cracking reactor having a single riser and circulating an FCC catalyst. The riser is divided into three temperature zones in which different hydrocarbon feeds are introduced. An oxygenate feed is introduced in the operative top zone in the riser. Heat for the endothermic cracking is obtained by the exothermic reaction of converting the oxygenate feed into gas and/or from a regenerator in which the spent FCC catalyst is burnt.

主权项

1. A process for obtaining light olefins with comparatively higher yields comprising the following steps:
i. providing a pre-heated cracking reactor having a riser maintained at a pressure in the range of 0.5 to 3 bar, charged with a solid acidic FCC catalyst, said riser being provided with at least three temperature zones; a first zone operative at the bottom of the riser having a temperature varying between 650° C. to 750° C., a second intermediate zone having a temperature varying between 580° C. to 650° C. operative above the first zone and a third zone operative at the top of the riser having a temperature in the range of from 500° C. to 620° C.; ii. feeding, at a weight hourly space velocity of 0.2 h-1 to 50 h-1, a first hydrocarbon feed having C4 hydrocarbons and other paraffinic streams to the first zone, feeding at a weight hourly space velocity of 5 h-1 to 100 h-1, a second hydrocarbon feed having olefinic naphtha stream to the second zone and feeding, at a weight hourly space velocity of 40 h-1 to 200 h-1, a third hydrocarbon feed comprising heavy hydrocarbons to the third zone; and iii. cracking the first, second and third hydrocarbon feeds sequentially, with the help of heat generated by at least one of two heat generating reactions selected from the group consisting of (a) introducing an oxygenate feed to the third zone and converting the oxygenate feed to a gaseous state and (b) burning coke formed in the spent FCC catalyst in a regenerator at a temperature of 650 to 750° C. in the presence of oxygen to generate hot gases and feeding the hot gases from the regenerator to the riser, thereby obtaining light olefins with comparatively higher yield.