Catalytic cracking method and catalytic cracking device for producing propylene

Abstract

The invention discloses a catalytic cracking method and a catalytic cracking device for producing propylene. The catalytic cracking method comprises the following steps that one or more heavy raw materials and a first catalytic cracking catalyst comprising a main active component of Y-type zeolite undergo a contact reaction in a first riser reactor; one or more light hydrocarbons and a second catalytic cracking catalyst comprising a main active component of shape-selective zeolite having aperture sizes less than 0.7nm undergo a contact reaction in a second riser reactor; and reacted oil gas and the catalysts are introduced into a fluidized bed reactor connected to the second riser reactor in series and then undergo a reaction. A stripper of the catalytic cracking device is divided into two independent stripping zones by a separator plate, wherein one of the two independent stripping zones and a combined reactor composed of one riser and a fluidized bed form one reaction and stripping route; and the other one of the two independent stripping zones and the other riser form the other one reaction and stripping route. The catalytic cracking method has high propylene and butene yields. The catalytic cracking device has a simple structure and can respectively realize a reaction and regeneration in a device by two catalysts.

Description

technical field [0001] The invention relates to a catalytic cracking method and device for producing propylene. Background technique [0002] Catalytic cracking of heavy oil is an important method for preparing small molecular olefins such as ethylene, propylene and butene. The method for producing light olefins by catalytic cracking of heavy oil used in industry is, for example, the catalytic cracking technology (DCC, USP4980053 and USP5670037) and the most Catalytic pyrolysis technology for mass production of ethylene (CPP, USP6210562), these two methods use a single riser reactor or a single riser reactor combined with a dense-phase fluidized bed reactor structure with a special catalyst at a higher temperature For the reaction, the catalyst used is a single catalyst system composed of active components such as medium-pore zeolite (such as ZSM-5) and / or large-pore zeolite (such as Y zeolite) with MFI structure. High yield of small molecule olefins. However, due to the l...

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Problems solved by technology

However, due to the large difference in the catalytic activity centers required to enhance the conversion of heavy oil and the improvement of small molecule olefins, it is sometimes difficult to react in a single riser reactor or a single riser reactor combined with a dense-phase fluidized bed in terms of the catalyst formulation. In the reactor, the requirements of heavy oil conversion reaction and high-yield small molecular olefins reaction are taken into account at the same time

Some catalytic cracking units increase the yield of prolific small molecule olefins by adding additives containing ZSM-5 zeolite, but the increase in the yield of small molecule olefins is small, and there are insurmountable defects: if the additive containing ZSM-5 zeolite If too few additives are used, it is difficult to meet the requirements of high-yield small molecule olefins; and if more additives containing ZSM-5 zeolite are added, the main agent will be diluted and the overall effect of the entire catalyst system will be reduced. At the same time, there are still additives and main catalyst performance mutual matching problem

However, the above-mentioned regenerator structure also only solves the regeneration problem of a single catalyst system

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