Method of production of light olefins in catalytic cracking units with energy deficiency

Abstract

The present invention relates to a method of production of light olefins, with the objective of maximizing the production of propylene and in particular ethylene by the use of a special catalyst containing high-silica zeolite, whose composition also includes a dehydrogenating metal, so as to generate light olefins and appreciable deposition of coke on the catalyst. Gains in selectivity for light olefins are observed, and at the same time the energy deficiency of catalytic cracking in petrochemical operations with light hydrocarbons is minimized, avoiding problems due to the need to burn heating oil in the catalyst regenerating section to make up for the energy deficit of the converter.

Description

FIELD OF THE INVENTION[0001]The present invention relates to the field of processes for the production of light olefins, more particularly ethylene and propylene, in circulating fluidized-bed reactors by means of catalytic conversion with solid acids, being applicable to a feed comprising light hydrocarbons. The method described in the present invention teaches the use of a special catalyst for producing light olefins and depositing an appreciable amount of coke on the catalyst. Besides increasing the selectivity for light olefins and maximizing the production of propylene and, in particular, ethylene, at the same time use of the method minimizes the energy deficiency of catalytic cracking in petrochemical operations with light hydrocarbons.BACKGROUND OF THE INVENTION[0002]In the fluidized-bed catalytic cracking process, the cracking reactions of hydrocarbons take place by contact of a feed with a catalyst in conditions of dynamic flow, in a tubular reactor in ascending flow, also k...

AI Technical Summary

Benefits of technology

[0012]In the present invention, light olefins are produced, such as ethylene and propylene, and moreover an appreciable amount of coke is deposited on the catalyst. Gains are observed in selectivity for light olefins, and at the same time the energy deficiency of catalytic cracking in petrochemical operations with light hydrocarbons is minimized, avoiding the problems caused by the burning of heating oil in the regenerating section of the catalyst to make up for the energy deficiency of the converter.

Problems solved by technology

The cracking reactions for production of light olefins are highly endothermic, drastically increasing the thermal demand in the reactor, which makes it difficult to meet the energy demand.

The problem of meeting the thermal demand is aggravated if the streams used as feed are formed by light hydrocarbons, such as diesel or naphtha, which usually deposit smaller amounts of coke on the catalyst compared with the heavier feeds such as vacuum gas oils or atmospheric residues.

Nevertheless, besides the increase in the heat of reaction, the thermal demand is not met for three main reasons:1) the actual feed used is not a good precursor for formation of coke, having low Ramsbottom carbon residue,2) light hydrocarbons are more refractory to cracking, requiring higher reaction temperatures;3) conventional zeolites ZSM-5 do not produce much deposition of coke on the catalyst and the amount that must be used in the catalytic system is very large.

The regenerator bed must be heated to temperatures around 700° C. Temperatures lower than 680° C. make it difficult to burn the heating oil in the regenerating bed and cause uncontrolled circulation of catalyst in the direction of the cracking reactor.

The burning of oil in the regenerating bed promotes the development of various problems in operation of the regenerator.

For example, the heating oil to be used must be selected carefully, as heating oils with very low distillation point can cause afterburning, i.e., combustion outside of the bed.

Another problem that may arise is wear of the atomizers for introducing the heating oil into the regenerator.

There may also be premature deactivation of the catalyst, owing to the generation of points of high temperature in the combustion bed.

However, none of these relates to solution of the problem of energy deficiency of the converter, since they use heavy hydrocarbons, generally atmospheric residues or heavy vacuum gas oils of paraffinic origin, as process feed.