US2862870A - Process for upgrading residua - Google Patents

Description

958 A. 4VOORHIES, JR 2,

PROCESS FOR UPGRADING RESIDUA United States Patent PROCESS FOR UPGRADING RESIDUA Alexis Voorhies, Jr., Baton Rouge, La., assignor to 'Esso Research and Engineering Company, a corporation of Delaware Application November 23, 1953, Serial No. 393,617

3 Claims. (Cl. 208-56) The present invention relates to an improved process for converting residua such as the heavy residuum resulting from refining of petroleum and analogous material. The feed stock may be a petroleum residuum of high boiling range or it may be a total crude of the same general characteristics. Coal tar, shale oil and the like or the heavy ends thereof may be used as the feed.

In the prior art numerous proposals have been made for converting heavy residual oils to more volatile and more valuable products. As a rule, these heavy feed stocks have been converted by coking, that is, by subjecting them to high temperature treatment for a suificient period of time to crack part of the feed to lighter products and to degrade a portion to coke with the accompanying production of gas. The gas and coke so produced are normally of less value than the motor fuel and gas oil products. It is therefore preferred to produce as much motor fuel and gas oil as possible with a minimum conversion to gas and coke. An object of the present invention is to accomplish such conversion.

It has also been proposed recently to convert heavy residual oils of the type mentioned above by the use of a hydrogen donor diluent. The feed and the diluent are subjected to mild thermal treatment which results in cracking the feed to obtain a good distribution of products. This process has been called for brevity the hydrogen donor diluent cracking process or more briefly the HDDC process. The present invention involves a specific improvement in the HDDC process.

According to the present invention a suitable feed stock such as heavy petroleum residuum is combined with a hydrogen donor diluent, to be described, and the mixture is preheated to a suitable temperature, usually between about 750 and 1000 F. A preferred temperature is between about 800 and 900 F. The mixture is passed into a reactor where the ingredients remain for a time and at a temperature suitable for accomplishing the hydrogen donor diluent cracking. This cracking results in the production of substantial proportions of gasoline, of light gas oil boiling between about 430 and 700 F., of heavy gas oil boiling between about 700 and 1050 F., and a bottoms fraction boiling above about 1050 F. The motor fuel and light gas oil products are taken to storage or to further processing such as hydroforming or catalytic cracking. A portion of the 700 to 1050 F heavy gas oil fraction also may be taken to a catalytic cracking operation. Part of the same fraction is treated according to the present invention, to convert it substantially to armatic products for a purpose to be described. The remainder of the 700 to 1050 F. fraction is passed through a hydrogenator.

The portion of the heavy gas oil which is treated to convert it to a substantial degree to aromatics is contacted with a suitable catalyst for this purpose. A highly satisfactory process for aromatizing involves an operation in the nature of hydrocracking wherein a suitable catalyst is used and hydrogen gas is evolved. Such hydrocracking processes preferably use a chromia alumina catalyst and are operated at a pressure of 50 to 500 p. s. i. g. and at a temperature between about 900 to 1050 F. with a feed rate of 0.6 to 0.9 w./-hr./w. for a fixed or fluid bed process. A suitable catalyst consists of 95% of alumina and 5% of chromia.

Typical data from an aromatizing process are listed below in Table I.

Table I East Texas Wide Out West Texas Operating Conditions Light Gas Paraflinic Wide Cut Oil Gas Oil Gas Oil Reactor Temperature, "F 975 975 975 Reactor Pressure p. s. i. g 100 Feed Rate, W./ W 0.72 0.72 0.72 Hydrogen Rate, 0. F./B 3, 000-5, 000 3, 000-5, 000 3, 0005, 000 400 F.+Gas Oil, V01. Percent on e 31 34 Gravity, API 14. 4 15. 4 15. 3 Aniline Point, F 34 52 54 Feed Stock Inspections:

Gravity, API 33. 7 30. 3 29. 2 Aniline Point, "F 172 192 165 The products from the aromatizing, or more specifically hydrocracking, process described contain considerable proportions of condensed ring aromatics which are excellent hydrogen donor materials when partially hydrogenated. The decrease in the aniline point indicates tungsten sulfide.

the increase in aromatics. The aromatization product contains 65 to percent of aromatic hydrocarbons of which about one-half are of the desired bicyclic or higher condensed ring type. The products from the aromatizer are fractionated into the same cuts, temperature-wise, as the products mentioned above. Thus products boiling in the gasoline range may be added to the gasoline product from the first reactor and the light gas oil may be added to the primary light gas oil.

The 700 to 1050 F. aromatized product is passed to a hydrogenator along with a portion of the original heavy gas oil (700 to 1050 F. cut) mentioned above. These combined materials are hydrogenated partially but .not completely by treatment with 200 to 2000 s. c. f. of hydrogen per barrel of feed to the hydrogenator. The precise method of hydrogenating forms no part of the present invention but a suitable process involves the use of a standard hydrogenating catalyst, preferably of the sulfur insensitive type, e. g. molybdenum sulfide, or nickel- Hydrogenation is carried out at moderate temperatures (600-800" F.) and at suitable pressure such as 200 to 1000 pounds per square inch.

It will be understood that the purpose of the aromatizing step is to provide continuously a make-up stream of the most desirable type of aromatics. Such a make-up stream is necessary because the hydrogen donor reaction is not completely selective and the distillation of products in the primary fractionator is not completely selective. Otherwise the desired condensed ring products would circulate indefinitely Within the system, picking up hydrogen in the hydrogenator and releasing it in the HDDC reactor. However, a small proportion of the total recycle through the hydrogenator is sufiicient to keep the system in balance. Thus 5 to 10% of the heavy gas oil fraction, 700 to 1050 F., may be passed through the aromatizer and the 700 to 1050 F. fraction of the aromatized product, which may amount to only about half the feed to the aror'natizer, is combined with the bulk of the heavy gas oil for hydrogenating and recycling to the HDDC reactor.

In a typical example, l0,000B./D. of residuum feed are mixed with 20,000 B./D. of a recycle stream, and after suitable preheating the mixture is contacted in the reactor at 800-900 F. and at a pressure that may be varied from substantially atmospheric to 500 p. s. i. g., and

higher. The recycle stream contains the hydrogen donor as will be described subsequently. The converted products pass from the reactor to a still where conventional separation is made to (give gas, gasoline, a 430-700 F. cut, a 7001050 F. cut, and .a 1050 F.+ bottoms. The 700-l050 F. cut is split into two streams. The larger stream consisting of 14,500 B./D. is sent to a low pressure hydrogenation step before recycling to the reactor. The smaller stream of 700-l050 F. material comprising 1000 B./ D. is sent to the aromatizer for the purpose of producing a 7001050 F. cut consisting to a large extent of polycyclic, condensed ring aromatics. The product from the aromatizer goes to a small still where the products are separated into gas, gasoline, a 430-700" F. cut, a 700-1050 F. material, and 1050 F.+ bottoms. The small amount of 1050 F.+ bottoms is mixed with the 500 B./D. of 1050 F.+ material from the primary still and is included in the 20,000 B./'D. of recycle material which enters the process. The highly aromatic 700-1050 F. cut consisting of 500 B./D. is blended with the 14,500 B./D. of primary 7501050 F. cut previously mentioned, and this combined feed of 15,000 B./D. goes to the hydrogenation step.

The invention will be more clearly understood by reference to the attached drawings which illustrate diagrammatically two preferred embodiments thereof. Figure 1 shows schematically a system incorporating the features mentioned above and Figure 2 shows an alternative and somewhat simplified system.

Referring first to Figure 1 the feed, a suitable petroleum residuum for example, enters through line 11 and passes through a suitable heater, for example, a coil 13 where its temperature is raised to between 750 and 1000 F. A preferred temperature is between 800 and 900 F. A recycle stock described below is preheated simultaneously and the combined products are passed through line 15 into the HDDC reactor vessel 17. In this vessel the reaction is allowed to continue for a suitable period of time which may range from A to 4 hours or more. The products from reactor 17 pass through line 19 to a fractionator or a distillation unit 21. Here the C and lighter gases are taken overhead through line 23. A motor fuel fraction from C to about 430 F. passes out through line 25. The 430 to 700 F. light gas oil passes off through line 27 and the 700' to 1050 F. heavy gas oil through line 29. A bottoms fraction passes through line 31 to return lines 57 and 33 which recycle it to the heater 13.

The heavy gas oil fraction is divided approximately into two or more parts depending upon the product distribution desired. Thus a portion may be taken through line 35 as a product for direct use or for feed stock to a catalytic cracker. A minor portion, for example 5 to is led through line 29 to an aromatizing zone 39. A major fraction is carried through line 41 to pass through the hydrogenator and recycle with the feed as will be described.

The fraction passed to the aromatizer is treated with a suitable aromatizing catalyst at a temperature between 900 and 1050 F. under pressure which may be between 50 and 500 p. s. i. g. The products from the aromatizer are taken to a fractionator 43 through line 45. Here a gas fraction which may include hydrogen is carried overhead through line 47 to combine with the gas in line 23. When this gas is rich in hydrogen, as it is in some cases, the hydrogen may be returned to the hydrogenator described below. The products from fractionator 43 which boil in the motor fuel range are taken off through line 49 and the light gas oil through line 51 to combine respectively with the products in lines 25 and 27.

The 700 to 1050 F. fraction from the fractionator 43 is passed through a line 53 to the hydrogenator 55. A bottoms fraction from fractionator 43 is taken through line 57 to recycle with the bottoms from fractionator 21 to line 33.

The aromatized heavy gas oil fraction is combined with the heavy gas oil from line 41 and by line 53 is transferred to the hydrogenating unit 55. This contains a suitable hydrogenating catalyst such as molybdenum sulfide or other suitable catalyst of known type. Hydrogen gas, or a mixture rich in hydrogen, is supplied through line 61 to the hydrogenator, spent gas being taken off overhead in line 63 through a suitable valve 65. It may be and frequently is desirable -to recycle the spent gas from line 63 to the hydrogen feed line 61 to conserve hydrogen.

The hydrogenator 55 is operated under such conditions as to partially but not fully hydrogenate the condensed ring aromatic constituents entering through line 53. As noted above these constituents are considerably enriched by passing part of the hydrogenator feed through the aromatizing operation at 39.

The hydrogenated material is taken from hydrogenator 55 through line 67 to combine with the refluxing bottoms from the fractionators. These combined materials are added to the feed and passed through the heater 13 to the HDDC reactor where the cycle is repeated. With an average petroleum residuum feed stock and with the various streams divided in the proportions suggested above, the process of this invention may yield about 5% by volume of gasoline, 20% of 400 to 700 F. light gas oil and 70% of 700 to 1050 F. heavy gas oil per pass. The overall efficiency will vary with the division of the 700 to 1050 F. stream from line 29. These yields are merely illustrative and will vary to some extent with the quality of the original feed stock. In general conversion of approximately may be expected. By recycling, the bottoms may be treated to extinction. Gas yields are relatively low.

Referring now to Figure 2 the same general process is shown except that the effluent from the aromatizer is recycled to the primary fractionator. This eliminates the need for a secondary fractionator 43 as shown in Figure 1.

Briefly, feed enters through line 71 to heater 73 and HHDC reactor 75. The reaction products are taken to fractionator 77 through line 79. The gas, gasoline, light gas oil, and heavy gas oil are taken off respectively through lines 81, 83, 85, and 93. Bottoms from fractionator 77 are recycled through line 89 to return line 91.

A portion of the 700 to 1050 F. heavy gas oil passes directly through line 93 to the aromatizer 95 from which the total products are recycled through line 97 to the fractionator 77. The remainder of the 700 to 1050 F. gas oil is taken to the hydrogenator 99 through line 101 except that a portion may be withdrawn as product through line 103 if desired. If will be understood that in all these lines, and in the lines of Figure 1 suitable valves will be provided as needed.

The heavy gas oil taken to the hydrogenator 99 through line 101 includes an aromatized portion recycled through the fractionator. This material, together with gas oil which has not been aromatized, is partially hydrogenated, hydrogen being supplied through a line 105 and spent gas removed through a line 107 as in Figure 1.

The partially hydrogenated feed is recycled through line 109 to combine with the fractionator bottoms in line 91 and both are taken through the heater with the fresh feed to the HDDC reactor.

It will be understood that various modifications may be made in the arrangement and use of the systems described in detail above without departing from the spirit of the invention.

What is claimed is:

1. The process of upgrading heavy oil to produce lower boiling products which comprises combining with one volume of feed one to four volumes of a partially hydrogenated recycle stock obtained as described hereinafter, heating the combined feed and recycle stock to a temperature within the range of 750 to 1000 F., passthe heated mixture into a reaction zone and reacting for a suflicient time to transfer hydrogen from the recycle stock to the feed and to crack the mixture, fractionating the products of the reactor to obtain a motor fuel fraction, a light gas oil fraction and a heavy gas oil fraction, aromatizing part of said last mentioned fraction, partially hydrogenating the aromatized and unaromatized portions of said heavy gas oil fraction and recycling the partially hydrogenated fraction to the feed.

2. Process according to claim 1 wherein the feed and recycle stock are preheated to a temperature between 800 and 900 F.

3. The process of converting heavy residual oil to products of motor fuel and gas oil boiling range which comprises: combining with one volume of feed one to four volumes of a partially hydrogenated recycle stock obtained as described hereinafter, heating the combined feed and recycle stock to a temperature between about 750 to 1000 F., and reacting this mixture for a period of about M4 to 4 hours to transfer hydrogen and cause hydrogen donor diluent cracking of the feed, fractionating the cracked products to separate therefrom a heavy gas oil fraction boiling within the range of about 700 to 1050 F., aromatizing about 5 to 10% of said heavy gas oil and fractionating the aromatized product, segregating a first fraction of the aromatized product boiling above about 1050 F. and recycling it to the said reaction zone, segregating a second fraction of the aromatized product boiling in the range of about 750 'to 1050" F. and combining said second fraction with at least a part of the non-aromatized heavy gas oil, partially hydrogenating said combined heavy gas oils, and recycling them to the reaction zone.

References Cited in the file of this patent UNITED STATES PATENTS 2,249,337 Visser July 15, 1941 2,290,033 Burk et al July 14, 1942 2,426,929 Greensfelder Sept. 2, 1947 OTHER REFERENCES Sachanen: Chemical Constituents of Petroleum (1945), page 223, Reinhold Publishing Corp.

Claims (1)

1. THE PROCESS OF UPGRADNG HEAVY OIL TO PRODUCE LOWER BOILING PRODUCTS WHICH COMPRISE COMBINING WITH ONE VOLUME OF FEED ONE TO FOUR VOLUMES OF A PARTIALLY HYDROGENATED RECYCLE STOCK OBTAINED AS DESCRIBED HEREINAFTER, HEATING THE COMBINED FEED AND RECYCLE STOCK TO A TEMPERATURE WITHIN THE RANGE OF 750* TO 100*F., PASSTHE HEATED MIXTURE INTO A REACTION ZONE AND REACTING FOR A SUFFICIENT TIME TO TRANSFER HYDROGEN FROM THE RECYCLE STOCK TO FEED AND TO CRACK THE MISTURE, FRACTIONING THE PRODUCTS OF THE REACTOR TO OBTAIN A MOTOR FUEL FRACTION, A LIGHT GAS OIL FRACTION AND A HEAVY GAS OIL FRACTION, AROMATIZING PART OF SAID LAST MENTIONED FRACTION, PARTIALLY HYDROGENATING THE AROMATIZED AND UNAROMATIZED

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