The Application Of Catalyst And Accessory Ingredient In Catalytic Cracking

The process of transferring heavy oil to catalyst gas,gasoline and kerosene by black oil cracking reactions under catalyst and heat is one of the processes of petroleum refining by catalytic cracking as well as an indispensable method in heavy oil processing.The raw material adopted is heavy oil distillate obtained from crude oil distilling or other oil refining process.In the process of reaction,some nonvolatile material similar to carbon deposits on the surface of catalyst and condense to coke, which can decrease the activity of the catalyst.Therefore,it should be burnt by air to restore the activity of the catalyst and provide necessary heat for cracking reaction.The main ingredient of catalyst is Silicic acid,and its acidity active center functions in catalysis.Catalytic cracking is proceeding according to the mechanism of carbocation.Catalyst promotes reactions of cracking,isomerization and aromatization. Products from catalyst cracking have more economic value than those from thermal cracking:more C3,C4 and more isomer in the gas,more isohydrocarbon,little dialkene and more aromatic hydrocarbon in gasoline.Main reactions includes:1) decomposition which turns heavy hydrocarbon to light hydrocarbon;2)isomerization; 3)hydrogen transfer;4)aromatization;5)reactions of condensation and greencoke. Isomerization and aromatization turn linear hydrocarbon with low bracket to isohydrocarbon and aromatic hydrocarbon with high-octane rating.With the increase of catalyst consistency in the system,from 1%-2%in the past to 10%-30%at present, the boundary between accessory ingredient and catalyst is not clearly cut.In recent years,the fast developed economy in our country has increased the consumption of gasoline greatly,which has brought severe environmental pollution. Sulfur content must be reduced further according to fuel standard in our country.And in 2010,China will implement discharge standard equal to Europe-Ⅲ,and discharge of nitrogen dioxide and sulfur dioxide should be reduced,which leads to a higher and higher demand for catalyst and accessory ingredient—reducing sulfur content further, increasing octane number,and producing more propylene.This thesis aims to research and tail the application of neotype catalyst and accessory ingredient in several catalytic cracking systems,study the specific influence of different catalyst formula towards product quality and environment,and investigate the best catalyst formulas and their operating conditions.