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 comprising the following steps:
i. providing a pre-heated cracking reactor comprising 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 in the range of 650° C. to 750° C.,a second intermediate zone having a temperature in the range of 580° C. to 650° C. operative at a point above the first zone anda third zone operative at the top of the riser, above the second zone, having a temperature in the range of 500° C. to 620° C.; ii. feeding a first hydrocarbon feed comprising C4 hydrocarbons and a paraffinic stream to the first zone at a weight hourly space velocity of 0.2 h−1 to 50 h−1, feeding a second hydrocarbon feed comprising olefinic naphtha to the second intermediate zone at a weight hourly space velocity of 5 h−1 to 100 h−1, feeding a third hydrocarbon feed comprising heavy hydrocarbons to the third zone at a weight hourly space velocity of 40 h−1 to 200 h−1; iii. cracking the first, second and third hydrocarbon feeds sequentially along the riser, thereby producing light olefins; wherein additional heat is provided to the riser by:
introducing an oxygenate feed comprising methanol to the third zone and converting the oxygenate feed to olefins; andoptionally burning coke formed in a 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 to the first zone.