Research On The Process Of Producing More Propylene By Catalytic Cracking Of Paraffin-based Crude Oil In A Descending Be

Propylene is a very important chemical raw material.Propylene is usually obtained from naphtha steam cracking,propane dehydrogenation,methanol to olefins and catalytic cracking.The catalytic cracking process has been widely used due to its mild operating conditions,self-sufficiency of heat,strong adaptability of raw materials,and high selectivity of propylene in the products.Because of the back-mixing phenomenon of oil and gas and catalyst in the anti-gravity field movement in the traditional riser reactor of catalytic cracking,it will cause long reaction residence time,high dry gas and coke yield,while the descending bed reactor has the advantage of short gas-solid contact time and less gas-solid axial back-mixing in reactor and large-dosage-to-oil ratio operation.This article explored the potential of using a down-bed reactor to catalyze the cracking of paraffin-based crude oil to produce more propylene.The heavy component of condensate(paraffin-based crude oil)has high hydrogen content and saturated content,and is theoretically a good raw material for catalytic cracking to produce low-carbon olefins.Using suitable catalysts and process conditions on the micro-reverse heavy oil evaluation device,the yield of propylene,the heavy component of condensate oil,could reach 16.32%.Using the same catalyst and process conditions as the micro-reverse heavy oil evaluation device,the propylene yield of cracking condensate heavy component on the riser reactor was20.98%,Huizhou third-line wax oil(intermediate base crude oil)on the riser reactor was 20.98% and14.83% respectively,which proved the superiority of paraffin-based crude oil as a feedstock for catalytic cracking of propylene.Using a descending bed reactor to catalytically crack the heavy components of condensate under the conditions of catalyst-to-oil ratio of 25,residence time of 0.72 s,Reactor top temperature 540 ℃,and reaction temperature of 560°C,the yield of propylene is 21.26%,the yield of dry gas is 6.21%,The yield of the liquefied gas is54.43% and that of the coke is 2.51%.Compared with the riser reactor,the dry gas yield decreased by 3.33%,the liquefied gas yield increased by 2.76%,the propylene yield increased by 1.04%,and the coke yield increased by 1.23%.The research results show that the use of the descending bed reactor for catalytic cracking of paraffinic crude oil can increase the production of propylene and greatly reduce the dry gas yield compared with the riser reactor.The coke yield can make up for the shortcomings of paraffin-based crude oil catalytic cracking that cannot meet the thermal balance.It also shows that the down-bed reactor has certain advantages and development potential in the process of producing more propylene.