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| United States Patent |
3,619,411 |
|
Wald
|
November 9, 1971
|
PROCESS OF CONVERTING HIGH-BOILING HYDROCARBON TO LOWER-BOILING FLUID
PRODUCTS
Abstract
Very high-boiling hydrocarbon, such as petroleum residue, is converted to
low-boiling liquid products by passing it through a continuous phase of a
catalyst system selected from antimony trichloride, tribromide or
triiodide; bismuth trichloride or tribromide; or arsenic triiodide;
maintained at a temperature between 200.degree. and 550.degree. C. and
under hydrogen partial pressure of at least 250 p.s.i. whereby the
catalyst system performs the functions of acting as a hydrogenation
catalyst, acting as a cracking catalyst, and providing a medium for
maintaining the reactants in suitable relation to one another to promote
reactions and obtain beneficial product distribution.
| Inventors: |
Wald; Milton M. (Walnut Creek, CA) |
| Assignee: |
Shell Oil Company
(New York,
NY)
|
| Appl. No.:
|
04/841,842 |
| Filed:
|
July 15, 1969 |
| Current U.S. Class: |
208/108 ; 208/251H; 208/254H; 502/224 |
| Current International Class: |
C10G 1/00 (20060101); C10G 1/08 (20060101); B01j 011/78 (); C10g 013/08 (); C10g 023/16 () |
| Field of Search: |
208/108,112,113,125 252/441
|
References Cited [Referenced By]
U.S. Patent Documents
Primary Examiner: Gantz; Delbert E.
Assistant Examiner: Schmitkons; G. E.
Claims
What is claimed is:
1. A process for producing lower boiling liquid products from higher boiling hydrocarbons which comprises contacting the higher boiling hydrocarbons with a continuous phase
catalyst of metal halide selected from antimony trichloride, antimony tribromide, antimony triiodide bismuth trichloride, bismuth tribomide and arsenic triiodide, said continuous phase maintained at a temperature of from about 200.degree. to about
550.degree. C. and under a hydrogen partial pressure of at least 250 p.s.i., and recovering the lower boiling normally liquid products therefrom.
2. The process of claim 1 wherein the continuous phase is maintained between 275.degree. and 400.degree. C.
3. The process of claim 1 wherein the hydrogen partial pressure is at least 800 p.s.i.
4. The process of claim 1 wherein unreactive solids are removed from said meal trihalide.
5. The process of claim 1 wherein said catalyst is subjected to regeneration reactions which convert ammonia-metal-halogen compounds to metal trihalide.
6. The process of claim 1 wherein the metal trihalide is antimony tribromide.
7. The process of claim 1 wherein the metal trihalide is antimony triiodide.
8. The process of claim 1 wherein said higher boiling hydrocarbon comprises a liquid hydrocarbon fraction boiling above 300.degree. C.
9. The process of claim 1 wherein said higher boiling hydrocarbons comprises petroleum residue.
10. The process of claim 1 wherein said higher boiling hydrocarbons comprises liquid products recovered from coal processing.
Description
BACKGROUND OF THE INVENTION
Very high boiling hydrocarbon fractions are difficult to process into lower boiling fractions that are more useful. The higher boiling fractions characteristically boil above 300.degree. C. and typically are petroleum residues; liquid products
recovered from tar sands, shale, or coal processing; high-boiling fractions resulting from cracking processes, and others. These fractions are difficult to process for one or more of the following reasons.
Typical high-boiling hydrocarbon fractions are hydrogen deficient and must be processed to add large quantities of hydrogen to the molecules, and particularly to fragments resulting from cracking processes. Strong hydrogenation activity, which
requires the presence of active hydrogenation catalyst, is required to prevent unsaturated fragments from condensing to form coke.
High boiling fractions also are characteristically rich in materials that poison catalysts. Petroleum residues contain organically bound sulfur, oxygen and nitrogen which are known to have an adverse effect on commonly used catalysts such as
hydrogenation-active catalytic metals supported on refractory oxides such as silica-alumina. Petroleum residue fractions are also rich in metal contaminants, particularly vanadium and nickel, and in processing such fractions vanadium and nickel
compounds deposit on the catalyst surfaces. Such deposits cause a decline in the activity of the catalyst. Additionally, traditional catalysts have deposits of coke deposited on catalytic surfaces at a very rapid rate when processing high boiling
fractions, and the resultant lost activity can be restored only by burning the deposits from the catalyst surfaces. The high temperatures of regeneration diminish the catalyst activity and cause the catalyst to deteriorate physically due to thermal
shock, so that large volumes of catalyst must be replaced.
These difficulties, among others, have restricted the use of very high boiling hydrocarbon fractions for conversion to lower boiling, more useful products.
THE INVENTION
The invention deals with a process for converting very high-boiling hydrocarbon to lower-boiling liquid hydrocarbon products, which process avoids or greatly mitigates the above-enumerated problems. The process of this invention employs a
particular catalyst in a triple role which causes extremely high conversion of high boiling hydrocarbon to useful liquid products that are lower boiling, at reasonable operating conditions, and avoids the problems usually associated with such
conversions.
These catalysts have extremely high catalytic activity and therefore give high conversion at moderate temperatures and pressures. Under the reaction conditions usable with the catalyst systems of this invention, it is possible to obtain a very
favorable product selectivity. Much less than the usual amount of propane and lighter hydrocarbons are formed, thereby greatly saving on the amount of the costly hydrogen gas required for the conversion. Because of the high and selective cracking
activity of the catalyst, a much larger part of the liquid product than usual boils within the range normally used for gasoline, and therefore less further processing is required. Moreover, the gasoline-range portion of the liquid product contains a
high percentage of desirable isoparaffin hydrocarbons, which are high octane components, and of cycloparaffin hydrocarbons which are excellent feeds for catalytic reforming. The catalysts are insensitive to the amounts of water, hydrogen sulfide and
heavy metals formed, which often are catalyst poisons, and their effectiveness is not diminished by the presence of normal amounts of solids such as coke.
The process of the present invention involves the use of a continuous liquid phase catalyst system which is selected from antimony trichloride, tribromide or triiodide; bismuth trichloride or tribromide; or arsenic triiodide as a catalyst to
promote hydrogenation, as a catalyst to promote cracking, and as a liquid medium in which the desirable conversion reactions take place readily. The conversion is effected in the continuous liquid catalyst phase at temperatures between 200.degree. and
550.degree. C., preferably between 275.degree. and 400.degree. C., where the reaction is effected at a reasonable rate without producing too many normally gaseous products, and in a temperature range where hydrogenation reactions are more favored.
The reaction is also effected at hydrogen partial pressures of at least 250 p.s.i., preferably at least 800 p.s.i., to provide sufficient driving force for hydrogenation. While higher partial pressures of hydrogen have no adverse effect on the
conversion, extremely high pressures are to be avoided because of the engineering difficulties and high costs involved in attaining and maintaining them. It is a significant advantage of this invention that results near optimum are obtained at pressures
below 2000 p.s.i.g.
In the process of this invention hydrogen is preferably introduced beneath the surface of the continuous catalyst phase so that it is absorbed in the catalyst and available to hydrogenate hydrocarbons in the system prior to or simultaneously with
cracking reactions that are effected. The hydrogen may be from any source and need not be pure. For example, hydrogen resulting from a reforming process that contains light hydrocarbon, hydrogen sulfide or water may be employed. The hydrogen
preferably is introduced either mingled with the charge or at least beneath the surface of the continuous catalyst phase in the form of finely dispersed bubbles, and unreacted hydrogen is preferably separated from other vapor products of the conversion
and returned to the reaction vessel. The manner of introducing hydrogen may be used to stir the system, and additional stirring may be provided if required.
The conditions maintained in the reaction zone of the process of this invention are such that nickel, vanadium or other heavy metal contaminants are converted to inorganic compounds, i.e. oxides or sulfides. In this form, and particularly when
immersed in a continuous liquid body of catalyst, they exert substantially no influence on the reactions taking place. They deposit as a separate solid phase and may be removed continuously or periodically as described hereinafter.
It was unexpected that the continuous phase metal halide catalysts of this invention were not poisoned by water and hydrogen sulfide formed by hydrogenating heterocyclic molecules found in the charge. These materials appear to pass through the
catalyst system and appear in the product without significant effect on the catalyst. Water and hydrogen sulfide particularly are usually very destructive of Friedel-Crafts-type catalysts by forming inactive reaction products. Very heavy hydrocarbon
fractions are known to contain large amounts of sulfur and oxygen, and severe catalyst poisoning problems in employing a Friedel-Crafts-type catalyst should be anticipated. However, the metal halide catalysts of this invention, as distinct from many
other Friedel-Crafts catalysts, are not adversely affected by sulfur or oxygen compounds or their reaction products.
However, the metal halide catalysts are affected by nitrogen compounds or by ammonia which is the hydrogenation product of the nitrogen in heterocyclic molecules. It appears that ammonia-metal-halogen complexes form which are stable compounds
and the reactions forming them are not reversible at conditions within the reactor. However, since the continuous phase of catalyst is very large compared with the nitrogen content of the charge, the complexes that form do not make the process
uneconomical. In a continuous process in accordance with this invention, ammonia-metal-halogen reaction products may either be removed, and makeup catalyst added as required, or the catalyst may be subjected to regeneration. With regard to the latter
process, regeneration may be effected on a slip steam of catalyst so that an equilibrium inventory of complex is maintained in the total catalyst body, and desirably a slip-stream of catalyst will be circulated from the main body to a separate
regenerating zone where coke and heavy metal compounds are removed as well.
As stated above, the metal halide catalysts are surprisingly active and durable as catalysts for converting very high boiling fractions to produce lower boiling liquid products. The reactions promoted are cracking, as evidenced by the low
boiling range of the product compared with the high boiling character of the charge, and hydrogenation, as evidenced by hydrogen takeup during processing and the saturated nature of the product, as well as by the low production of heavy products.
The following examples are presented to illustrate various aspects of the present invention and are provided to be illustrative rather than limiting on the scope of the invention.
EXAMPLE 1
A petroleum residue fraction known as flasher pitch was converted to lower boiling hydrocarbons boiling largely in the gasoline boiling range. The flasher pitch is a brittle, black solid that can be liquified enough to barely be poured at
100.degree. C. The particular pitch employed contained 1.42 percent w nitrogen, 1.13 percent w oxygen and 0.96 percent w sulfur and significant quantities of vanadium and nickel.
In two experiments the indicated amount of pitch was placed in an autoclave with the indicated amount of catalyst and processed for 60 minutes at 350.degree. C. under 1800 p.s.i. of hydrogen partial pressure. The products resulting from these
conversions are the following:
Charge __________________________________________________________________________ SbCl.sub.3, g. 150 100 Pitch, g. 50 20 Products, g./100 g. of Pitch __________________________________________________________________________ C.sub.1 +C.sub.2
0.5 0.6 Propane 1.1 3.2 Butanes 3.7 11.9 Pentanes 3.5 8.8 Hexanes 3.7 9.9 C.sub.7 +C.sub.8 hydrocarbons 8.6 15.0 Hydrocarbon boiling above C.sub.8 and below 250.degree. C. 23.3 21.4 Hydrogen Consumed grams/100 g. of Pitch 5.0 6.7
The data show that at the relatively mild conditions employed a significant quantity of low value flasher pitch was converted to valuable gasoline range liquid products. In subsequent runs it was indicated that no catalyst deactivation was
experienced until large quantities of coke and ammonia-metal-halogen complex were in the continuous phase catalyst. The water and hydrogen sulfide produced had no significant effect on the catalyst.
EXAMPLE 2
Another group of autoclave experiments employed antimony tribromide as a continuous phase catalyst for converting the flasher pitch described in example 1. In this group different temperatures were employed as well as different amounts of charge
as indicated. The products from these processes are set forth below.
Charge __________________________________________________________________________ SbBr.sub.3, g. 150 150 Pitch, g. 20 30 Time, minutes 60 60 Temperature, .degree.C. 300 350 Pressure, p.s.i. 1800 1550 Products, g./100 g. Pitch
__________________________________________________________________________ C.sub.1 +C.sub.2 0.2 1.4 Propane 0.6 2.3 Butanes 2.0 8.1 Pentanes 1.8 7.1 Hexanes 2.9 8.7 C.sub.7 +C.sub.8 hydrocarbons 5.9 14.5 Hydrocarbon boiling above C.sub.8 and below
250.degree. C. 20.3 18.1 Hydrogen, g./100 g. Pitch 1.5 4.5
EXAMPLE 3
In example 3 the process of this invention is employed to convert high boiling hydrocarbons other than flasher pitch. In all cases the conversions took place in an autoclave for 60 minutes in the presence of 150 grams of antimony tribromide and
under a hydrogen partial pressure of 1800 p.s.i. The products reported in column A are from a charge of extra heavy gas oil, while the products reported in column B are from a fraction boiling in the gas oil range obtained from distilling the product
from a catalytic cracking process. Both charges boiled substantially higher than gasoline.
Products, g./100 g. of charge A B C.sub.1 +C.sub.2 0.6 0.4 Propane 1.1 0.8 Butanes 5.1 3.4 Pentanes 5.2 4.3 Hexanes 7.0 6.4 C.sub.7 +C.sub.8 hydrocarbons 12.1 12.2 Hydrocarbon boiling above C.sub.8 and below 250.degree. C. 14.0 18.0
similar runs employing antimony triiodide, bismuth trichloride, bismuth tribromide and arsenic triiodide yield similar but not identical results. All catalysts have slight differences between cracking and hydrogenating activity, as well as
different absolute activity levels for each. Accordingly, although the desired effect may be obtained for any charge with any catalyst, it is evident that different catalysts will produce different products, and different operating conditions with any
catalyst will produce different products.
In general, the more active catalysts may function at lower temperatures to selectively produce material boiling in the gasoline boiling range, while the less active catalysts may be prepared to produce higher boiling material such as turbine
fuel or charge for catalytic crackers.
As stated above, it is desirable to maintain the catalyst body in the reactor at some operable equilibrium level of contamination with regard both to the ammonia-metal-halogen complex and with regard to solids such as metal sulfide and coke. One
method for maintaining the equilibrium catalyst activity is to remove a slip-stream from the body of molten catalyst in the reactor and subject it to a separation process for separating metal trihalides from noncatalytic materials, to regenerate metal
trihalides from the complex, and to discard coke, heavy metals and other nonuseful solids. Although any number of regeneration schemes may be employed, one useful scheme is as follows.
A slip-stream of liquid phase from the catalyst bed is removed and subjected to extraction with hot toluene or other available aromatic solvents. Toluene is a highly selective solvent for the metal trihalides used as catalysts, and for liquid
hydrocarbons. This extraction produces an extract stream containing toluene, hydrocarbon, and metal trihalide from which the toluene may easily be removed by flashing, and metal trihalide and hydrocarbon may be returned to the reaction vessel, and a
raffinate stream that will consist largely of ammonia-metal-halogen complex, coke, and nickel and vanadium compounds. The raffinate stream may be subjected to high temperature treatment which will cause the complex to decompose to ammonium halide and
meal trihalide, so that regenerated metal trihalide may be returned to the reaction zone while solid phase coke and heavy metal compounds may be discarded.
The regeneration and cleaning process suggested above is exemplary only and others may be employed with equal success. Of course, the rate at which such regeneration and cleaning is effected will be determined to a large extent by such factors
as the nitrogen content of the charge, and the rate at which coke is produced in the conversion process. With a continuous phase catalyst, however, the regeneration process can function with a great deal of latitude in that exceptionally large
quantities of catalyst will be present in active condition even under circumstances where a great deal of catalyst contamination exists.
To better describe the present invention, the accompanying drawing is provided. The drawing illustrates
schematically a flow diagram representing one process embodying this invention and, being highly schematic, it does not illustrate heaters, valves, instrumentation and other conventional equipment that would normally be employed in such a process.
In the drawing the high-boiling hydrocarbon charge is introduced through line 1 and is mixed with liquid hydrocarbon recycled from the process as hereinafter described through line 2 and the mixed stream is pumped through pump 3 into line 5
wherein it is mixed with hydrogen supplied through line 6. Line 6 contains recycled hydrogen to which makeup hydrogen is added through line 7. In pump 3 the pressure of the charge is raised to reaction pressures, preferably about 1800 p.s.i., and it
passes into the lower portion of reactor 8.
In reactor 8 a large pool of catalyst, preferably antimony tribromide, is maintained in sufficient quantity to be a continuous phase during the reaction process. The charge, introduced beneath the body of liquid antimony tribromide, passes
upwardly through it, preferably distributed as fine droplets. A separate stream of hydrogen gas may also be introduced beneath the catalyst liquid level through line 9 to aid in maintaining the contents of reactor 8 well mixed.
Within reactor 8 which is maintained at 350.degree. C., the cracking and hydrogenation reaction occur within the liquid catalyst medium and a product of lower-boiling normally liquid hydrocarbons, which are in vapor phase at reaction conditions,
discharges from reactor 8 through line 10. The material in line 10 is cooled and flashed in phase separator 11 to remove a recycle hydrogen stream and the resultant liquid product from the process passes through line 12 into fractionation column 13. In
fractionation column 3, light products are passed overhead through line 15 while the heavier materials are returned through the beforementioned line 2 as part of the charge to the process.
In order to maintain the catalyst at an equilibrium level of activity and cleanliness, a slip stream is removed through line 18 and it passes into extraction zone 20. In extraction zone 20 the liquid catalyst is countercurrently contacted with
solvent entering the lower portion of extraction zone 20 through line 21 and as a result of the countercurrent contact an extract stream consisting of solvent, antimony bromide, and hydrocarbon passes through line 22 into flashing zone 23 which is
maintained at lower pressure. In flashing zone 23 solvent is separated from the extract stream and passes overhead through line 21 through which it is returned to the lower portion of extractor 20. The remainder of the extract stream is passed from the
bottom of flashing zone 23 through line 25 and returned to the main body of catalyst. The material in line 25 consists almost entirely of the antimony tribromide and hydrocarbon that was removed in the slip stream passing through line 18.
The raffinate phase from extractor 20 consists of coke, heavy metal compounds, and ammonia-antimony-bromide complex formed in the reaction zone 8. This material is introduced into regenerator 27 where it is subjected to high enough temperature
to decompose the complex to form antimony bromide and ammonium bromide. If necessary, hydrogen bromide or bromine is also added to regenerator 27 so that the regeneration may be better effected. The regenerated antimony bromide is returned to reactor 8
through line 28, either directly or by being added to the stream in line 18, while the residual material including coke and heavy metal compounds is removed through line 30 and subjected to appropriate further treatment.
The process of the present invention may be varied in the manner of its performance without departing from the scope or spirit of the invention. For example, the process may be effected in two or more stages, with mixture of catalytic metal
halides, with various cleaning and regenerating schemes and in conjunction with other processes.
* * * * *
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