US3437584A - Method for converting heavy carbonaceous materials - Google Patents

Description

METHOD FOR CONVERTING HEAVY CARBONACEOUS MATERIALS Filed Aug. 9, 1967 SSG SDG ATTORNEYS United States U.S. Cl. 208-93 7 Claims ABSTRACT F THE DISCLOSURE Method for converting relatively heavy hydrocarbonaceous feedstocks, such as black oil, using a two-stage catalytic reaction zone. Facilities for separating selected fractions of feed and product are provided.

BACKGROUND OF THE INVENTION This invention relates to a catalytic hydrocarbon conversion process. It particularly relates to a method for separating selected fractions of feed and product for further processing within the inventive circuit. It specifically relates to a black oil conversion process.

It is known in the art that petroleum crude oil is the basic building block upon which a vast petroleum and chemical industry has been built. The hydrocarbonaceous materials contained in crude oil have been used in upgraded fashion for a wide variety of industrial consumer products, such as gasoline, fuel oil and chemicals. Basically, the economic incentive in refining crude oil is to upgrade the various products obtainable from crude oil to a maximum degree. It has long been known that the virgin products separated from crude oil, usually by distillation means, are only marginal in upgraded value. Consequently, synthetic means have been developed, such as catalytic cracking, catalytic reforming, catalytic hydrotreating, etc. in order to substantially increase the value of products obtained from crude oil.

Traditionally, the optimum economic incentive has been to convert petroleum gas oils via catalytic cracking means including hydrocracking into gasoline boiling range prod ucts suitable for use either as chemicals or as motor fuel for internal combustion engines. The effect of this emphasis of course, was to leave the relatively heavy hydrocarbonaceous materials as unattractive by-products from the petroleum refining operations. These relatively heavy materials were characteristically utilized in the fuel oil and asphaltic end products thereby returning to the refiner a minimum dollar value for processing.

One of the reasons these heavy hydrocarbonaceous materials have not been significantly utilized in upgraded products has been the lack of processing technology for increasing the value of products made from such materials and the significant contaminant level such as sulfur compounds, nitrogen compounds, metals such as vanadium and nickel which these materials universally contained in undesirable amounts.

More recently, the prior art has developed means for hydrocracking these black oil materials in order to obtain more valuable products, such as gasoline boiling range materials. In spite of the relatively heavy contaminant level of the black oils, processing techniques have been recently developed for cracking the materials to gasoline. However, for the most part, the prior art has only achieved partial success in that marginal conversions of black oils to gasoline have been achieved and/or such conversion has required extreme complexity of equipment. Therefore, it would be desirable to provide a method for improving the conversion process of relatively heavy hydrocarbonaceous materials to products of increased economic value.

3,437,584 Patented Apr. 8, 1969 Therefore, it is an object of the present invention to provide an improved method for the conversion of relatively heavy hydrocarbonaceous feedstocks.

It is another object of this invention to provide a method for converting black oils to more valuable products utilizing separation facilities for separating selected fractions of feed and product for further processing within the inventive circuit.

Accordingly, the present invention provides a method for the conversion of relatively heavy hydrocarbonaceous feedstocks which comprises the steps of: (a) separating said feedstocks into a lighter fraction and a heavier fraction; (b) introducing said 'heavier fraction into the lower end of a distillation column maintained under distillation conditions including sub-atmospheric pressure, said column comprising a vertically elongated column having an imperforate vertically disposed partition only in said lower end, at a locus at one side of said partition; (c) simultaneously introducing a hereinafter specified hydrocarbon feed stream into said lower end at a locus on the other side of said partition; (d) withdrawing from said column a bottoms product comprising residium at a locus connected to said side of partition specified in Step (c); (e) withdrawing from said column another bottoms fraction comprising heavy hydrocarbons at a locus connected to said side of partition specified in Step (b); (f) introducing said heavy hydrocarbons from Step (e) into a first conversion zone maintained under conversion conditions including the presence of hydrogen and a pressure greater than about 1000 p.s.i.g.; (g) separating the resulting first conversion zone eiiiuent into a first vapor fraction and a liquid fraction; (h) passing at least a portion of said liquid fraction into said column as the hydrocarbon feed stream specified in Step (c); (i) withdrawing from the upper end of said column at a locus devoid of partition a combined hydrocarbon distillate fraction containing hydrocarbons originally present in said heavier fraction of tep (a) and in said feed stream of Step (c); (j) introducing said lighter fraction, and said combined hydrocarbon distillate fraction into a second conversion zone maintained under conversion conditions including the presence of hydrogen; and, (k) recovering converted hydrocarbonaceous material from the eflluent of said second conversion zone.

It is to be noted from the embodiment of the invention presnted hereinabove that the present invention has two major critical features, to wit: a two-stage conversion zone, preferably catalytic, and a distillation column having a dividing partition located therein in such a manner that two distinct bottoms products may be obtained therefrom while simultaneously obtaining at least one combined distillate fraction therefrom. It is believed that these major critical features of the invention provide significant advances over the prior art schemes both in terms of efficiency in operation and in economy of construction and operation.

Suitable relatively heavy hydorcarbonaceous feedstocks for use in the practice of the present invention include the traditional black oils which generally may be characterized by having more than 10% by volume boiling above a temperature of about 1050a F. In addition, these black oils generally have an API gravity at 60 F. of less than 20.0 and the Conradson Carbon Residue usually exceeds 1% by weight. Illustrative of black oils, using conventional terminology, include atmospheric bottoms products, vacuum bottoms tower products, crude oil, residuum crude oils extracted from tar sands, synthetic crudes obtained from shale, and the like. The present invention is particularly advantageous in handling feedstocks conforming to the black oil definition; al-

though, it will be recognized from the discussion presented herein that lighter hydrocarbons, such as the light cycle oils obtained from catalytic cracking operations, may be simultaneously processed within the inventive circuit.

With reference to the distillation column containing the imperforate partition at the lower end thereof, this apparatus may be defined as comprising a vertically disposed elongated column; vertically spaced substantially horizontal perforated partitions dividing the column into a plurality of contacting zones for vapor and liquid; substantially vertical imperforate partition extending upwardly from the lower end of said column to a locus at least below the hereinafter specified uppermost withdrawal means, dividing the column into at least two vertical sections containing a plurality of contacting zones for vapor and liquid; means for introducing liquid into each vertical section; means for withdrawing liquid from each vertical section at a locus below said introduction means; and uppremost means for withdrawing vapor at a locus above the upper end of said imperforate partition, said uppermost means having common communication with each vertical section.

The separating conditions for the distillation column of the present invention are generally well known to those skilled in the art from general knowledge complemented by the teachings presented herein. The temperature and pressure of a conventional distillation column when processing, for example, crude oils, are not materially different in the practice of this invention than in the practice of the prior art schemes which have utilized two separate and distinct distillation columns handling single feeds or the same column in blocked-out separation. However, in the practice of this invention it is required that the distillation column lbe operated under sub-atmospheric pressure, i.e., from 5 to 700 mm. Hg absolute and at a feed temperature, for example, from 500 F. to 800 F. rwhen charging a relatively heavy hydrocarbonaceous feedstock previously defined hereinabove.

As will become more fully evident from the discussion presented during the description of the drawing presented herewith, the temperature at which each feed is introduced into the column at the proper feed locus may either be the same or may be different. Typically, in the practice of this invention the flash zone temperature in each defined vertical section is different. The distillation column may contain conventional trays or contacting means which are well known to those skilled in the art. These trays may be of the bubble-type design, perforated design, may be of the disk and donut design, or any other vapor-liquid contacting design. Those skilled in the art can desing the column from the teachings presented herein and from a general knowledge of distillation columns.

The defined vertical sections in the distillation column, which is a critical feature of the inventive method, are usually two in number; that is, a single vertical imperforate partition is placed in the column usually at the center thereof and extending upwardly above the flash zone of the distillation column, thereby defining two vertical sections so that each individual feedstock is fed respectively into different sides of the partition. However, it is within the concept of the present invention that the vertical partition lbe placed so that vertical sections numbering three or four may be applicable so that more than two different feedstocks may be fed into this single column.

This critical distillation column, of course, may be designed to produce any number (e.g. 1 to 3 or more) of distillate fractions. It is preferred in the practice of this invention when charging black oils for there to be only one combined distillate fraction obtained which is subsequently charged to the second conversion zone for further upgrading.

The separating conditions chosen for the respective conversion zones are generally those which will convert a substantial portion of the relatively heavy hydrocarbonaceous feedstock into lower molecular weight and desirable hydrocarbons. The first conversion zone conditions, for example, include a temperature between 600 F. and 900 F., a pressure from 1,000 p.s.i.g. to 10,000 p.s.i.g., a liquid hourly space velocity from 0.2 to 5.0, and a hydrogen-to-oil ratio from 500 to 20,000 standard cubic feet of hydrogen per ibarrel of oil (s.c.f./b.), based on fresh feed, sufficient to convert a substantial portion of the feed into the desired product. As previously mentioned, hydrogen is employed in both conversion zones and with respect to the first conversion zone, preferably, in an amount from l9,000 to 12,000 s.c.f./b. The hydrogen-containing gas stream fulfills a number of functions, to wit: it serves as a hydrogenating agent, a heat carrier, and particularly a means for stripping converted material from the catalytic composite, thereby creating still more catalytically active sites available for the incoming, unconverted hydrocarbon charge stock. Since hydrogen is consumed in both reaction zones, makeup hydrogen must be added to the system by any suitable means well known to those skilled in the art.

The catalytic composite disposed within the first reaction zone can be characterized as comprising a metallic component having hydrogenation activity, which component is composited with a refractory inorganic oxide carrier material of either synthetic or natural origin. The precise composition and method of manufacturing the carrier material is not considered essential to the present invention, although a siliceous carrier, such as 88.0% alumina and 12.0% silica, or 63.0% alumina and 37.0% silica, are generally preferred. Suitable metallic components having hydrogenation activity are those selected from the group consisting of the metals of Groups VI-B and VIII of the Periodic Table, as indicated in the Periodic Chart of the IElements, Fisher Scientific Company (1953). Thus, the catalytic composite may comprise one or more metallic components from the group of molybdenum, tungsten, chromium, iron, cobalt, nickel, platinum, palladium, iridium, osmium, rhodium, ruthenium, and mixtures thereof. The concentration of the catalytically active metallic component, or components, is primarily dependent upon the particular metal as well as the characteristics of the charge stock. For example, the metallic components of Group VI-B are preferably present in amounts within the range of about 1.0% to about 20.0% by weight, the iron-group metals in an amount within the range of about 0.2% to about 10.0% by weight, whereas the platinum-group metals are preferably present in an amount within the range of about 0.1% to about 5.0% =by weight, all of which are calculated as if the components existed within the finished catalytic composite as the elemental metal.

The refactory inorganic oxide carrier material may comprise alumina, silica, zirconia, magnesia, titania, boria, strontia, hafnia, etc., and mixtures of two or more including silica-alumina, silica-zirconia, silica-magnesia, silica-titania, alumina-zirconia, silica-alumina-boron phosphate, alumina-magnesia, alumina-titania, magnesia-zirconia, titania-zirconia, magnesia-titania, silica-aluminazirconia, silica-alumina-magnesia, silica-alumina-titania, silica-magnesia-zirconia, silica-alumina-biria, etc. It is preferred to utilize a carrier material containing at least a portion of silica, and preferably a composite of alumina and silica with alumina being in the greater proportion.

The catalyst disposed in the second conversion zone serves the dual function of further converting sulfurous and nitrogenous compounds and kconverting those hydrocarbons boiling above about 700 F. to 800 F. into the lower boiling or lower molecular weight hydrocarbons. A particularly suitable catalyst for the second conversion zone comprises relatively large quantities of the Group VI-B metals (i.e., 6% to 45% by weight molybdenum) and leser quantities of an iron group metal (i.e., 1% to 6% by weight of nickel).

Other conditions and operating techniques will be given in conjunction with the description referring to the atached drawing which is a schematic representation of apparatus for practicing one embodiment of the invention. In the drawing, such details as pumps, instrumentation, heat exchangers, conventional recovery equipment, valving, and other conventional hardware, have been omitted as being non-essential to an understanding of the techniques involved. Recovery of the desired products from the effluent of the final conversion zone is by conventional separation means, such as distillation, and have not been shown in the drawing, since to do so would not add to an understanding of the inventive technique involved.

DESCRIPTION OF THE DRAWING The description of the drawing will utilize a typical petroleum refinery situation which has available as feedstock light cycle oil, reduced crude oil, and vacuum tar material. Thus, referring to the drawing, reduced crude from an atmospheric distillation column enters the process via line and passes into atmospheric separation zone 11. A light, principally vaporous fraction is removed overhead via line 12 and a heavy fraction is removed via line 15. A light cycle oil is introduced into the process via line 13 and a vacuum tar material is introduced to the process via line 14.

The heavier fraction in line 15 is admixed with vacuum tar from line 14 and passed via line 16 into distillation column 17. Distillation column 17 contains approximately trays, vertical partition 18 is placed in the column so that there are two vertical sections, 19 and 20 respectively. Also, there may be four distillation trays below the feed inlet loci of sections 19 and 20; although, in a vacuum flash operation, satisfactory results can be achieved with no trays below the feed inlet loci. The remainder of the trays are above the inlet loci for the feed to the tower, more fully discussed hereinafter.

A vacuum gas oil material is removed via line 30 from the upper portion of vacuum column 17 at a locus which is devoid of partition. As defined herein, the term devoid of partition is intended to embody the concept that partition v18 ends at a point below the draw-olf locus for the combined distillate fraction as shown by space 21 such that it is, upon communication, between space 21 and vertical defined sections 19 and 20. In other words, there could be a partition located, if desired, in the upper end of the column and such would be included in the concept of the present invention as long at it was, upon communication, between the draw-off locus for the combined distillate fraction in question and the vertical sections defined by the partition or partitions placed at the lower end of the column.

Simultaneously, with the introduction of the heavy material from line 16 there is also introduced into the column from a source hereinafter specied a hydrocarbon feed stream via line 28 which enters the column at a locus on the other side of the partition from the locus for line 16. A residuum material is removed from vacuum colunm 17 via line 38 and is disposed of by means known to those skilled in the art such as to fuel and/or asphalt.

A heavy hydrocarbon fraction which has had distillable and lower molecular weight material removed from it is withdrawn from column 17 via line 22. It is to be noted that the material in line 22 was obtained primarily from the feedstock entering the column from line 16 while the material removed via line 38 was principally obtained from the material entering column 17 from line 28. The heavy hydrocarbons in line 22 are admixed with a hydrogen-containing gas from line 23 and passed via line 24 into a first conversion zone represented by reaction zone block 25.

The first conversion zone eiuent leaves block 25 via line 26 and passes into separation zone 27 wherein sufficient conditions are maintained to produce a light fraction which is principally vapor and is removed via line 29 and a liquid fraction which is removed via line 28. The materal in line 28 is now passed into vacuum ash zone 17, as previously mentioned. It is preferable in the practice of this invention that a portion of the liquid fraction in line 28 be returned via line 39 to the first conversion zone in admixture with the heavy hydrocarbons in line 22. The purpose of this recycle stream is to increase the conversion level of the heavier hydrocarbons into lower molecular weight and distillable hydrocarbons.

The vapor product in line 29 containing hydrogen gas and light hydrocarbons is admixed with the vacuum gas oil combined distillate fraction from line 30 and passed via line 31 into admixture with the light fraction from separation zone 11 in line 12 and light cycle oil from line 13 which have been combined in line 32. This total admixture of light hydrocarbons and hydrogen is now passed via line 33 into admixture with additional hydrogen, if any, from line 34 for passage via line 35 into second conversion zone contained in reaction zone block 25. It is to be noted that a preferred technique in the practice of this invention is for the hydro-gen required in the second conversion zone be obtained solely from the hydrogen separated in separation zone 27 which is the effluent from the first reaction zone. In other words, it is preferred that no hydrogen be added to the system via line 34. The effluent from the second conversion zone is withdrawn via line 36 and passed into conventional recovery facilities for the reco-very of converted hydrocarbonaceous material. As previously mentioned, since both conversion zones consume hydrogen, added hydrogen from an extraneous source may be added to the process via line 37.

The specific practice of the two-stage conversion zone depicted in reaction zone block 25 of the drawing is more fully developed in my co-pending application Ser. No. 597,935, filed Nov. 30, 1966, now Patent No. 2,364,134, the entire enclosure of which is incorporated herein by reference.

Example A commercial scale plant was designed in accordance with the flow shown in the attached drawing. The following table illustrates the invention as one practical embodiment thereof.

Drawing Barrels Tempera- Pressure,

line or per stream ture, p.s.i.g. Description zone no. day F. (mm. Hg)

,00o 1,500 Vacuum tar feed. 600 5 Separation zone.

366 AGO from reduced crude feed. 2, 634 Atm. bottoms from reduced crude feed. 4, 134 Feed to rst vacuum flash. 750 (40) First vacuum flash. 3, 240 Vacuum bottoms to first reaction zone. First reaction zone. Hot separation zone. Bottoms from hot sep. (excluding recycle). Second vacuum flash. Residuum from second vacuum flash.

Combined VGO from 19 and 20.

Second reaction zone.

PREFERRED EMBODIMENT A preferred embodiment of the present invention in- 7 cludes a method for the conversion of relatively heavy hydrocarbonaceous feedstock which comprises the steps of: (a) introducing a feedstock having an initial boiling point in excess of 650 F. into the lower end of a distillation column maintained under distillation conditions including a pressure from to 700 mm. Hg absolute, and a feed temperature from 500 F. to 800 F., said column comprising a vertically elongated column having an irnperforate vertically disposed partition only in said lower end, at a locus on one side of said partition; (b) simultaneously introducing a hereinafter specified hydrocarbon fraction into said column at the lower end thereof at a locus on the other side of said partition; (c) withdrawing a residuum product stream from the bottom of said column at a locus connected to said side of partition specied in Step (b); (d) withdrawing a bottoms fraction from the bottom of said column at a locus connected to said side of partition specified in Step (a); (e) introducing said bottoms fraction into a hydrocracking reaction zone maintained under conditions including a temperad ture from 700 F. to 900 F., a pressure from 1000 p.s.i.g. to 10,000 p.s.i.g., a liquid hourly space velocity from 0.2 to 5.0, and a hydrogen to oil ratio from 500 to 20,000 s.c.f./b. sufficient to convert a substantial portion of said bottoms fraction into lower molecular weight and distillable hydrocarbons; (f) separating the efiiuent from said hydrocracking reaction zone into a light fraction and a liquid hydrocarbon fraction containing said lower molecular weight and distillable hydrocarbons; (g) passing said hydrocarbon fraction into said column on said other side of the partition as specified in Step (b); (h) withdrawing from the upper end of said column, at a locus devoid of partition, a combined vacuum gas-oil stream; (i) introducing said vacuum gas-oil and said light fraction from Step (t) into a catalytic hydrodesulfurization reaction zone under conditions including the presence of hydrogen gas sufficient to convert sulfur compounds to hydrogen sulfide; and, (j) recovering lower molecular weight and distillable hydrocarbon conversion products in high concentration.

The invention claimed:

1. Method for the conversion of relatively heavy hydrocarbonaceous feedstock which comprises the steps of:

(a) separating said feedstock into a lighter fraction and a heavier fraction;

(b) introducing said heavier fraction into the lower end of a distillation column maintained under distillation conditions including sub-atmospheric pressure, said column comprising a vertically elongated column having an imperforate vertically disposed par'- tition only in said lower end, at a locus on one side of said partition;

(c) simultaneously introducing a hereinafter specified hydrocarbon feed stream into said lower end at a locus on the other side of said partition;

(d) withdrawing from said column a bottoms product, comprising residuum, at a locus connected to said side of partition specified in Step (c);

(e) withdrawing from said column another bottoms fraction, comprising heavy hydrocarbons, at a locus connected to said side of partition specified in Step (b);

(f) introducing said heavy hydrocarbons from Step (e) into a first conversion zone maintained under conversion conditions including the presence of hydrogen and a pressure greater than about 1000 psig.;

(g) separating the resulting first conversion zone effluent into a first vapor fraction and a liquid fraction;

(h) passing at least a portion of said liquid fraction into said column as the hydrocarbon feed stream specified in Step (c);

(i) withdrawing from the upper end of said column,

at a locus devoid of partition, a combined hydrocarbon distillate fraction containing hydrocarbons originally present in said heavier fraction of Step (a) and in said feed stream of Step (c);

(j) introducing said lighter fraction, said first vapor fraction, and said combined hydrocarbon distillate fraction into a second conversion zone maintained under conversion conditions including the presence of hydrogen; and

(k) recovering converted hydrocarbonaceous material from the efliuent of said second conversion zone.

2. Method according to claim 1 wherein a portion of said liquid fraction of Step (g) is returned to said first conversion zone of Step (f).

3. Method according to claim 1 wherein said lighter fraction has an end boiling point from about 650 F. to about 850 F., and said heavier fraction has an initial boiling point in excess of 650 F.

4. Method according to claim 3 wherein said combined distillate fraction has an end boiling point from about 650 F. to about 850 F.

5. Method for the conversion of relatively heavy hydrocarbonaceous feedstock which comprises the steps of:

(a) introducing a feedstock having an initial boiling point in excess of 650 F. into the lower end of a distillation column maintained under distillation conditions including a pressure from 5 to 700 mm. Hg absolute, and a feed temperature from 500 F. to 800 F., said column comprising a vertically elongated column having an imperforate vertically disposed partition only in said lower end, at a locus on one side of said partition;

(b) simultaneously introducing a hereinafter specified hydrocarbon fraction into said column at the lower end thereof at a locus on the other side of said partition;

(c) withdrawing a residuum product stream from the bottom of said column at a locus connected to said side of partition specified in Step (b);

(d) withdrawing a bottoms fraction from the bottom of said column at a locus connected to said side of partition specified in Step (a);

(e) introducing said bottoms fraction into a hydrocracking reaction zone maintained under conditions including a temperature from 700 F. to 900 F., a pressure from 1,000 p.s.i.g. to 10,000 p.s.i.g., a liquid hourly space velocity from 0.2 to 5.0, and a hydrogen to oil ratio from 500 to 20,000 s.c.f./b. sufficient to convert a substantial portion of said bottoms fraction into lower molecular weight and distillable hydrocarbons;

(f) separating the effluent from said hydrocracking reaction zone into a light fraction and a liquid hydrocarbon fraction containing said lower molecular weight and distillable hydrocarbons;

g) passing said hydrocarbon fraction into said column on said other side of the partition as specified in Step (b);

(h) withdrawing from the upper end of said column, at a locus devoid of partition, a combined vacuum gas-oil stream;

(i) introducing said vacuum gas-oil and said light fraction from Step (f) into a catalytic hydrodesulfurization reaction zone under conditions including the presence of hydrogen gas sufcient to convert sulfur compounds to hydrogen sulfide; and

(j) recovering lower molecular weight and distillable hydrocarbon conversion products in high concentration.

6. Method according to claim 5 wherein the hydrogen gas in thel desulfurization zone was obtained solely from the effluent of the hydrocracking zone.

7. Method according to claim 5 wherein a portion of 9 10 the liquid hydrocarbon fraction from Step (f) is recycled 3,314,879 4/ 1967 Lacy et al. 208-361 to the hydrocrackng reaction zone of Step (e). 3,371,029 2/1968 Welland 208-364 References Cited HERBERT LEVINE, Primary Examiner.

UNITED STATES PATENTS 5 U.s. C1. x.R.

3,110,663 11/ 1963 'Miller 208-364 208-92, 94, 80, 59, 97, 366, 364; 196-111

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