FCC process for the maximization of medium distillates

Abstract

A FCC process for the maximization of medium distillates from feedstocks of different sources, by the contact of the feedstock which circulates in a riser reactor together with a fine particulate catalyst from a regenerator (6), under FCC conditions of maximum LCO, at temperatures between about 480° C. and about 520° C., in the absence of added hydrogen, and with injection of coolant or quench to a riser ascendant R, and where the process consists of the injection of a coolant proportion between about 200 and about 50 kg / m3 of feedstock, preferably between about 100 and about 50 kg / m3 of feedstock, in a zone (3) of the riser ascendant R in a position located between about 25% and about 50% of the height of said riser R above the feedstock inlet mouths (2), the injection in this position resulting in the increase of the catalyst circulation and the temperature increase in the starting segment of the riser, yielding the production of medium distillates with low aromatic compounds content and bottoms conversion lower than when the coolant injection is employed in the base of the riser R as it is handled in the prior art processes.

Description

CROSS REFERENCE TO RELATED APPLICATION [0001] This application is based upon, claims the benefit of, priority of, and incorporates by reference, the contents of Brazilian Patent Application No. PI 0504854-0 filed Oct. 31, 2005. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] This invention concerns a FCC (fluid catalytic cracking) process of low severity that maximizes medium distillates. More specifically, it relates to FCC processes for heavy or blended feedstocks that results in the maximization of medium distillates containing. low levels of aromatic compounds while, at the same time, maintaining the bottoms generation (cut at about 340° C.+). [0004] 2. Description of the Prior Art and Background of the Invention [0005] Fluid catalytic cracking (FCC) is carried out within a tubular reactor zone, or riser reactor, by the contact between hydrocarbons and a catalyst composed of fine particulate material. Most of the feedstocks submitted to the FCC process are re...

AI Technical Summary

Benefits of technology

[0018] In broad terms, the present invention relates to a FCC process to obtain medium distillates through the maximization of LCO with low aromatic compounds content and the minimization of the bottoms conversion. This beneficial combination is achieved by ensuring a high starting temperature in the first meters of the riser reactor where the primary reactions occur and using a coolant forward in such a way that the lower half of the riser reactor operates conventionally, while the upper half operates at low severity. Therefore, the invention provides a FCC process to obtain medium distillates where the process conditions lead to the production of LCO with low content of aromatic compounds while at the same time minimizing the bottoms conversion. The invention also provides a FCC process to obtain medium distillates where the coolant is injected from an inlet point located above ¼ of the riser reactor height. The invention still provides a FCC process to obtain medium distillates where the coolant injection, through an inlet point located above ¼ of the riser reactor height, has, as a consequence, the inhibition of secondary reactions and the creation of an additional energy claim applied to increase the catalyst circulation, in such a way that the fast cooling of the reaction mixture environment, just after the starting reactions, inhibits the secondary reactions, avoiding the formation of aromatic compounds.

Problems solved by technology

Notwithstanding, using lower catalyst circulation rates, in order to drop the temperature difference between regenerator and reactor, results in reduced catalyst-to-oil ratio (CTO) as well as reduced conversion.

As the catalyst circulation itself affects the coke yield, one can establish that the catalytic cracking process runs in a thermal balance regime, being undesirable operations at much too high regeneration temperatures.

When somehow one wants to blend LCO to a pool of diesel oil, it is challenging to change the FCC operation parameters in order to maximize the LCO streams.

However, the high aromatic compounds concentration in LCO brings about increased density and worse detonation quality for diesel engines (low cetane number).

The high aromatic compounds content also make difficult the improvement of LCO properties through a hydrotreating process.

he problem is that such operations also lead to increased FCC residual fraction (cut at 340° C.+), as often as not directed to fuel oil of low market value.

On one hand, it is harmful whether the target is lowering the aromatic compounds in the LCO fraction.

The recycle of such a fraction is not adequate to meet the objective of the invention, seeing that this heavy naphtha is blended in the diesel fraction and its recycle would increase the content of aromatic compounds, lowering its quality.

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