Process for upgrading fcc product with additional reactor

Abstract

A process is disclosed for taking a cut from an FCC reactor product and reacting it in a separate reactor to upgrade the product quality Cracking or reformulating reactions in the separate reactor give reductions in olefins and reformulating hydrogen-transfer reactions convert undesirable olefins to isoparaffins and aromatics without reducing octane value Catalyst particles from the FCC reactor may be cycled to the separate reactor This process has also been found to substantially diminish concentrations of nitrogen and sulfur compounds fed to the separate reactor.

Description

[0001] This invention relates generally to processes for the fluidized catalytic cracking (FCC) of heavy hydrocarbon streams. More specifically, this invention relates generally to processes for upgrading catalytically cracked hydrocarbon feeds in a discrete reactor vessel.DESCRIPTION OF THE PRIOR ART[0002] The FCC process is carried out by contacting the starting material whether it be vacuum gas oil, reduced crude, or another source of relatively high boiling hydrocarbons with a catalyst made up of finely divided or particulate solid material. The catalyst is transported in a fluid-like manner by passing gas or vapor through it at sufficient velocity to produce a desired regime of fluid transport. Contact of the oil with the fluidized material catalyzes the cracking reaction. The cracking reaction deposits coke on the catalyst. Coke is comprised of hydrogen and carbon and can include other materials in trace quantities such as sulfur and metals that enter the process with the star...

AI Technical Summary

Problems solved by technology

Coke interferes with the catalytic activity of the catalyst by blocking active sites on the catalyst surface where the cracking reactions take place.

As a result, both cracked products mix in the reactor, to some extent, which could negate the incremental upgrade resulting from cracking the secondary hydrocarbon feed, particularly if it is a fraction of the cracked primary hydrocarbon feed.

Bicyclic aromatics are very difficult to crack and boil only at high temperatures.

The presence of high boiling point bicyclic aromatics can cause a gasoline pool to exceed maximum volatility standards.

Apparently, the benefit of cracking lower boiling fractions was not explored, presumably because the octane rating of the lower boiling fraction was sufficiently high or because it was predicted not to be effective.

It is also known to subject cracked product from a riser of an FCC unit to a subsequent oligomerization reaction in a separate reactor.

Reducing olefin concentration without also reducing value is difficult because higher olefin concentrations typically promote higher Research Octane Numbers (RON) and Motor Octane Numbers (MON), but the latter to a lesser extent.

Additionally, saturation requires the addition of hydrogen, which is expensive and in some regions, difficult to obtain.

Advantageously, the hydrogen transfer reactions are performed without the addition of hydrogen, which can be expensive and difficult to obtain

The low conversion operation yields high quantities of LCO, some gasoline and not much LPG.

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