Catalytic cracking

Purpose

Cracking deepens oil refining: high-octane gasoline, light gas oil and raw materials for petrochemicals are obtained from vacuum gas oil and other heavy residues. It is this process that determines the depth of processing in modern factories.

Chemistry

The reaction proceeds according to the carbocation mechanism: hydrocarbon molecules at the acid sites of the catalyst are split, isomerized and redistribute hydrogen. Coke and dry gas are formed as a by-product.

Catalyst and regeneration

Type Y zeolites are used in a matrix with ZSM-5 additives to increase the yield of propylene. The catalyst quickly cokes and continuously circulates between the reactor and the regenerator, where the coke is burned off with air. The heat of combustion of coke covers the energy costs of the process.

Products

• catalytic cracked gasoline with an octane number of 90–93;
• propane-butane fraction - raw material for gas fractionation and petrochemicals;
• light gas oil is a component of diesel fuel after hydrotreating;
• heavy gas oil and decant oil;
• dry gas and coke.