Mineral oils: processes and products – Chemical conversion of hydrocarbons – With preliminary treatment of feed
Reexamination Certificate
1999-01-08
2001-03-13
Myers, Helane (Department: 1764)
Mineral oils: processes and products
Chemical conversion of hydrocarbons
With preliminary treatment of feed
C208S057000, C208S059000
Reexamination Certificate
active
06200462
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of hydroprocessing. In particular, the present invention relates to hydroprocessing to obtain high conversions, product selectivity and selective hydrotreating of specific boiling range products.
BACKGROUND OF THE INVENTION
Much of refinery processing involves reaction of refinery streams in a hydrogen atmosphere. In order to maximize conversion efficiencies and to maintain catalyst life, excess hydrogen is generally used in the catalytic conversion processes, with the unreacted hydrogen being recovered, purified and repressurized for use as a recycle stream. Such recycle processes are costly, both in energy and in equipment. Some progress has been made in developing methods for using a single hydrogen loop in a two-stage reaction process.
U.S. Pat. No. 5,114,562 teaches a multi-reactor zone process for the production of low aromatics, low sulfur jet fuel or diesel fuel. The two reaction zones, one for desulfurization and one for hydrogenation, operate in a series flow arrangement with a common hydrogen supply system. This process uses strippers to remove H
2
S from cooled hydrogen rich gases recovered from effluent streams, to permit use of the stripped hydrogen stream in both the desulfurization reaction zone and the hydrogenation reaction zone.
U.S. Pat. No. 5,403,469 teaches a parallel hydrotreating and hydrocracking process. Effluent from the two processes are combined in the same separation vessel and separated into a vapor comprising hydrogen and a hydrocarbon-containing liquid. The hydrogen is shown to be supplied as part of the feedstreams to both the hydrocracker and the hydrotreater.
U.S. Pat. No. 3,172,836 teaches a general process for processing a hydrocarbon feed in a catalyst bed, passing a liquid fraction from a first catalyst bed, together with hydrogen, through a second catalyst bed, separating the effluent from the second catalyst bed into a liquid portion and a vapor portion. The vapor portion is combined with the hydrocarbon feed in the first catalyst bed.
U.S. Pat. No. 4,197,184 discloses a conventional multiple-stage process for hydrorefining and hydrocracking a heavy hydrocarbonaceous charge stock. In the process, hydrocracked effluent is admixed with hydrorefined effluent and the combination separated into a hydrogen rich vaporous stream and normally liquid material. The cooled vapor stream is then used as a source of hydrogen and as a quench fluid for both the hydrorefining reaction zone and the hydrocracking reaction zone.
EP 787,787 discloses a hydroprocess in parallel reactors, with hydrogen flowing in series between the reactors. Effluent from a first reaction zone is separated into a first hydrogen rich gaseous stream and a first hydroprocessed product stream. The first hydrogen rich gaseous stream is shown as being used as quench for a second reaction zone. The first hydrogen rich gaseous stream is also combined with a second hydrocarbon feedstock and fed to the second reaction zone, at a lower hydrogen partial pressure than is the first reaction zone. Effluent from the second reaction zone is separated, the second hydrogen rich gaseous stream being recycled to the first reaction zone, both as a quench stream and as a reactant in combination with a first hydrocarbon feedstock.
SUMMARY OF THE INVENTION
An objective therefore of the present invention is to reduce the number of processing units in an integrated hydroconversion process. Another objective of the present invention is to reduce the heating and repressurization requirements of an integrated hydroconversion process. Another objective of the present invention is to supply the hydrogen requirements of an integrated hydroconversion process with reduced hydrogen distribution complexity and processing duplication. The present invention serves to accomplish these objectives in a single reaction loop at lower cost than with multiple loops, while maintaining the advantages of a multiple loop system, including higher reaction rates or with catalysts tailored for pretreated feeds.
The present invention includes a process for reverse gas flow to obtain high conversion, selective hydrotreating and product selectivity in a hydroprocessing reactor system. Accordingly, the present invention provides a method of processing a hydrocarbon feed comprising:
passing a hydrocarbon feed to a hydrotreating zone, contacting at hydrotreating conditions the hydrocarbon feed with a hydrogen feed stream in the presence of a hydrotreating catalyst, and recovering a hydrotreating zone effluent therefrom;
separating the hydrotreating zone effluent and recovering at least a liquid fraction and a hydrogen rich gaseous stream;
passing the liquid fraction and a portion of the hydrogen rich gaseous stream to a hydrocracking zone, contacting the liquid fraction and the portion of the hydrogen rich gaseous stream at hydrocracking conditions with a hydrocracking catalyst and recovering therefrom a hydrocracking zone effluent;
passing the hydrocracking zone effluent to a vapor recovery zone and recovering from the vapor recovery zone at least a vapor stream; and
passing the vapor stream without substantial cooling to the hydrotreating zone for combining with the hydrogen feed stream.
The process of the invention is directed generally to an integrated hydroconversion process having at least two reaction zones in separate reactor vessels. Raw feed is introduced to a first reactor with hydrogen at conditions preselected for hydrotreating the feed. At least one liquid product from the first reactor is reacted in the presence of hydrogen in a second reaction zone at conditions preselected for hydrocracking the feed. Unreacted hydrogen recovered from the second reaction zone is relatively free of contaminants such as hydrogen sulfide and ammonia. In the practice of the present invention, the unreacted hydrogen from the second reaction zone is recovered at substantially the pressure and the temperature of the second reaction zone, and passed directly, without substantial cooling, as a portion of the hydrogen feed to the first reaction zone. Unreacted hydrogen recovered from the first reaction zone is purified to remove contaminants such as hydrogen sulfide and ammonia. During purification, the unreacted hydrogen from the first reaction zone is cooled. A portion of the cooled hydrogen stream is used as quench, to cool the reactants within the first reaction zone and the second reaction zone.
Among other factors, the present invention is based on the discovery that using the hydrogen from the second reaction zone, without substantial cooling and at the pressure of the second reaction zone, as hydrogen feed to the first reaction zone, produces substantial savings in both heating and in repressurization. The present invention provides reaction zones in series configuration with respect to hydrogen flow, such that the unused hydrogen from a second reaction zone employed for converting a relatively clean feed is used as a source of hydrogen for the initial processing in a first reaction zone. Such a single reaction loop lowers costs as compared to the use of conventional multiple reaction loops while maintaining the advantages of higher reaction rates, using catalysts tailored for converting pretreated feeds within a multiple reaction loop system. The series configuration reduces gas circulation, which reduces both investment and operating costs. The capital cost is lower due to smaller equipment and piping. Operating costs are lower due to less compressor power to recirculate gas. The series configuration provides that (a) the top bed catalysts are not contaminated with feed impurities, (b) the reaction rate in the top beds is not inhibited by substantial quantities of hydrotreating byproducts, e.g., NH
3
and H
2
S, and (c) hydrogen partial pressures are maximized for the high conversion processes. The present invention is thus based on the discovery of an integrated hydroconversion process which may be operated at much lower cost, both in terms of operating cost and of co
Cash Dennis R.
Yoon Hyung-Jae A.
Chevron U.S.A. Inc.
Klaassen Alan W.
Myers Helane
Prater Penny L.
Tuck David M.
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