Mineral oils: processes and products – Chemical conversion of hydrocarbons – With subsequent treatment of products
Reexamination Certificate
1999-10-21
2001-09-25
Myers, Helane E. (Department: 1764)
Mineral oils: processes and products
Chemical conversion of hydrocarbons
With subsequent treatment of products
C208S103000
Reexamination Certificate
active
06294080
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a hydrocarbon conversion process referred to in the art as hydrocracking. Hydrocracking is used in petroleum refineries to reduce the average molecular weight of heavy or middle fractions of crude oil. The invention more directly relates to an integrated hydrocracking and hydrotreating process which has a specific reactor effluent separation arrangement.
BACKGROUND OF THE INVENTION
Large quantities of petroleum derived hydrocarbons are converted into higher value hydrocarbon fractions used as motor fuel by a refining process referred to as hydrocracking. The high economic value of petroleum fuels has led to extensive development of both hydrocracking catalysts and the process technology. In a hydrocracking process the heavy feed is contacted with a fixed bed of a solid catalyst in the presence of hydrogen at conditions of high temperature and pressure which result in a substantial portion of the molecules of the feed stream being broken down into molecules of smaller size and greater volatility.
The raw feed contains significant amounts of organic sulfur and nitrogen. The sulfur and nitrogen must be removed to meet modern fuel specifications. Removal or reduction of the sulfur and nitrogen is also beneficial to the operation of a hydrocracking reactor. The sulfur and nitrogen is removed by a process referred to as hydrotreating. Due to the similarity of the process conditions employed in hydrotreating and hydrocracking the two processes are often integrated into a single overall process unit having separate sequential reactors dedicated to the two reactions and a common product recovery section.
RELATED ART
Hydrocracking processes are used commercially in a large number of petroleum refineries. They are used to process a variety of feeds ranging from naphtha to very heavy crude oil residual fractions. In general, the hydrocracking process splits the molecules of the feed into smaller (lighter) molecules having higher average volatility and economic value. At the same time a hydrocracking process normally improves the quality of the material being processed by increasing the hydrogen to carbon ratio of the materials, and by removing sulfur and nitrogen.
A general review and classification of the different hydrocracking process flow schemes is provided in the book entitled, “
Hydrocracking Science and Technology
”, authored by Julius Scherzer and A. J. Gruia, published in 1996 by Marcel Dekker, Inc. Specific reference may be made to the chapter beginning at page 174 which describes single stage, once-through and two-stage hydrocracking process flow schemes and basic product recovery flows employing vapor-liquid separation zones. This reference also shows that it is known that the feed stream can be passed first into a hydrotreating zone to remove organic nitrogen and sulfur before the feed stream enters the hydrocracking zone.
U.S. Pat. No. 3,260,663 issued to T.U. Inwood et al. shows a multistage hydrocracking process in which the feed is first charged to a hydrotreater
8
. The effluent of the hydrotreater flows into a separator
14
having trays
24
in the lower portion of the vessel to aid separation.
U.S. Pat. No. 3,540,999 and 3,544,448 issued to W. L. Jacobs illustrate the use of a hot and a cold high pressure separation zone in series as part of the product recovery section of a hydrocracking process.
U.S. Pat. No. 3,328,290 issued to R. J. Hengstebeck illustrates a hydrocracking process flow in which the feed stream and the effluent of a hydrocracking reactor are passed into a hydrotreating zone. The effluent of the hydrotreating zone is passed into the product recovery zone, with a recycle stream from the product fractionator recycled to the hydrocracking reactor.
SUMMARY OF THE INVENTION
The invention is a combined sequential hydrotreating/low conversion hydrocracking flow scheme characterized by the method employed to separate the effluent of hydroprocessing reactor and the overall process flow. For instance, the entire hydrocracking zone effluent is passed into the hydrotreating zone. The separation method includes recovering distillate products from part of the effluent of the hydrotreating zone. The invention is further distinguished by the passage into the hydrocracking zone of only parts of two specific fractions recovered from the effluent of the hydrotreating zone in a unique separation sequence employing two high pressure separation zones.
A broad embodiment of the invention may be characterized as a method for recovering a product of a hydrocarbon conversion process which employs two reactors, which method comprises separating the effluent stream of a first reactor containing hydrotreating catalyst maintained at hydrotreating conditions in an augmented first high pressure separator and thereby producing a light process stream comprising hydrogen and normally vaporous hydrocarbons, an intermediate process stream, rich in hydrocarbons boiling between 300 and 700° F., and a heavy process stream rich in hydrocarbons having boiling points above 700° F.; passing the light process stream, at least a first portion of the intermediate process stream and at least a first portion of the heavy process stream into a second high pressure separator operated at a pressure within about 100 psi of the first high pressure separator; separating the chemical compounds entering the second high pressure separator into a vapor phase stream which is passed into a second reactor and a liquid phase stream which is passed into a product recovery zone, and recovering a distillate product stream from the product recovery zone.
REFERENCES:
patent: 3260663 (1966-07-01), Inwood et al.
patent: 3328290 (1967-06-01), Hengstebeck
patent: 3540999 (1970-11-01), Jacobs
patent: 3544448 (1970-12-01), Jacobs
patent: 4283272 (1981-08-01), Garwood et al.
Scherzer, J. et al. Hydrocracking ProcessesHydrocracking Science and Technology(Marcel Dekker, Inc., 1986) pp. 174-183 ISBN 0-8247-9760-4 TP690.4.S34.
Anderle Christopher J.
Thakkar Vasant P.
Myers Helane E.
Spears, Jr. John F.
Tolomei John G.
UOP LLC
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