US3871992A

US3871992A - Visbreaking a heavy hydrocarbon feedstock in a regenerable molten medium

Info

Publication number: US3871992A
Application number: US345540A
Authority: US
Inventors: Lawrence F King; Noel J Gaspar; Israel S Pasternak
Original assignee: Individual
Current assignee: Individual
Priority date: 1973-03-28
Filing date: 1973-03-28
Publication date: 1975-03-18
Anticipated expiration: 1992-03-18
Also published as: CA1021282A

Abstract

Heavy hydrocarbon feedstocks, such as atmospheric and vacuum residua, heavy crude oils and the like, are converted to predominantly liquid hydrocarbon products by contacting said feedstocks with a regenerable alkali metal carbonate molten medium containing a glass-forming oxide, such as boron oxide at a temperature in the range of from above about the melting point of said molten medium to about 1,200* F. Preferably, the regenerable molten medium comprises an oxide of boron in combination with a mixture of sodium and lithium carbonate or a mixture of sodium carbonate, potassium carbonate and lithium carbonate. The carbonaceous materials (coke) which are formed in the molten medium during the above-described conversion process are gasified by contacting said carbonaceous materials with a gaseous stream containing oxygen, steam, or carbon dioxide at temperatures of from above about the melting point of said medium to about 2,000*F. in order to gasify said carbonaceous materials and thereby regenerate the molten medium. The conversion of a heavy hydrocarbon feedstock by the above-described process reduces the viscosity of the feedstock and thereby produces increased proportions of predominantly liquid hydrocarbon products of the motor fuel range and fuel oils.

Description

Unite States Patent [191 King et a1.

[11] 3,871,992 [451 Mar. 18, 1975 VISBREAKING A HEAVY HYDROCARBON F EEDSTOCK IN A REGENERABLE MOLTEN MEDIUM [76] Inventors: Lawrence F. King, R.R. No. l,

Moorestown, Ontario; Noel J.

Gaspar, 562 Cathcart Blvd., Sarnia, Ontario; Israel S. Pasternak, 579 Highbury Park, Sarnia, Ontario, all of Canada 22 Filed: Mar. 28, 1973 211 App]. No.: 345,540

[52] US. Cl 208/125, 208/230, 208/235 [51] Int. Cl Cl0g 9/34 [58] Field of Search 208/125, 128, 130, 107, 208/230, 235

[56] References Cited UNITED STATES PATENTS 3,387,941 6/1968 Murphy et al. 208/230 3,440,164 4/1969 Aldridge 208/218 3,480,689 11/1969 Bohrer 260/683 R 3,553,279 1/1971 Bawa 260/683 R 3,745,109 7/1973 Heredy et al. 208/107 FOREIGN PATENTS OR APPLICATIONS 386,669 1/1933 Great Britain 260/683 R Primary ExaminerHerbert Levine Attorney, Agent, or Firm-Jerome E. Luecke; John W. Ditsler [57] ABSTRACT Heavy hydrocarbon feedstocks, such as atmospherirand vacuum residua, heavy crude oils and the like, are converted to predominantly liquid hydrocarbon products by contacting said feedstocks with a regenerable alkali metal carbonate molten medium containing a glass-forming oxide, such as boron oxide at a temperature in the range of from above about the melting point of said molten medium to about 1,200F. Preferably, the regenerable molten medium comprises an oxide of boron in combination with a mixture of sodium and lithium carbonate or a mixture of sodium carbonate, potassium carbonate and lithium carbonate. The carbonaceous materials (coke) which are formed in the molten medium during the abovedescribed conversion process are gasified by contacting said carbonaceous materials with a gaseous stream containing oxygen, steam, or carbon dioxide at temperatures of from above about the melting point of said medium-to about 2,000F. in order to gasify said carbonaceous materials and thereby regenerate the molten medium. The conversion of a heavy hydrocarbon feedstock by the above-described process reduces the viscosity of the feedstock and thereby produces increased proportions of predominantly liquid hydrocarbon products of the motor fuel range and fuel oils.

11 Claims, 1 Drawing Figure VISBREAKING A HEAVY HYDROCARBON FEEDSTOCK IN A REGENERABLE MOLTEN MEDIUM FIELD OF THE INVENTION This invention relates to the conversion of heavy hydrocarbon feedstocks to produce increased proportions of motor fuel range hydrocarbons and fuel oils. More particularly, this invention relates to converting a heavy hydrocarbon feedstock to liquid hydrocarbon products by contacting said feedstock with an alkali metal carbonate molten medium. Still more particularly, this invention relates to the conversion of a heavy hydrocarbon feedstock such as atmospheric and vacuum residua, crude oils and the like, in a regenerable molten medium containing boron oxide and an alkali metal carbonate to produce predominantly liquid hydrocarbon products such as a gas oil and carbonaceous materials. At least a portion of the carbonaceous materials formed during the cracking process are gasified by contacting said carbonaceous materials in the molten medium with air at elevated temperatures in order to regenerate the melt.

DESCRIPTION OF THE PRIOR ART Heavy hydrocarbon materials such as atmospheric or vacuum residua, crude oil and the like, are typically subjected to a viscosity-reducing or visbreaking treatment at high temperatures and elevated pressures to convert, by a mild thermal cracking, the feedstock to about 5 to percent gas oil, about 5 to 15 volume percent gasoline, and about 75 to 85 percent heavy fuel oil. The specific temperatures, pressures, and feed rates employed in the visbreaking process depend upon the type of the visbreaker feed. The gas oil formed by such a process represents a feedstock suitable for the production of additional amounts of high quality gasoline by catalytic cracking or, after suitable finishing, such as sulfur and/ornitrogen removal, an acceptable distillate fuel.

The conversion of heavy hydrocarbon feedstocks, such as residua, is relatively difficult in view of their tendency to form coke when subjected to moderately high temperatures. This coke-forming tendency has also limited the industrial application of molten heat transfer media in order to effect the hydrocarbon conversion of such feedstocks. The difficulty primarily encountered in employing molten media systems for such conversion processes was the fact that the carbonaceous particles, i.e., coke, produced during the conversion operation were not suspended in the melt, but formed a separate phase which contaminated the liquid and gaseous products. With melts that partially suspended the coke, such as alkali metal halide eutectics, i.e., lithium-potassium chloride, the buildup of such carbonaceous materials in or above the molten medium necessitated additional steps to physically remove the carbonaceous particles from the melt.

It has been suggested that hydrocarbon feedstocks can be cracked in molten alkali metal carbonate, alkali metal hydroxide, or a mixture thereof, to form various hydrocarbon products and the molten medium thereafter regenerated by contacting the same with oxygen or steam (see U.S. Pat. Nos. 3,553,279; 3,252,774; German Pat. No. DT-OS 2,l49,29l; U.S. Pat. Nos. 3,505,018; 3,252,773; 3,438,727; 3,647,358; 3,438,728; Oil and Gas Journal, Sept. 27, 1971; U.S.

Pat. Nos. 3,438,733; 3,438,734; 3,516,796; 3,551,108 and 3,647,358. Further, in Czechoslovakian Pat. No. 109,952 it is disclosed that various compositions can be employed in the thermal cracking of hydrocarbons. While alkali metal carbonate based meltstend to absorb or disperse the coke formed in the conversion operation, the extent of coke dispersion is relatively low. This limited coke dispersion in the molten medium may cause process difficulties in a commercial environment.

SUMMARY OF THE INVENTION It has now been discovered that heavy hydrocarbon feedstocks, particularly sulfur contaminated feedstocks are converted to predominantly liquid hydrocarbon products by contacting said feedstocks with an alkali metal carbonate molten medium that contains minor quantities of a specific glass-forming oxide coke dispersion aid at a temperature in the range of from above about the melting point of said medium to about I,200F. for a period of time sufficient to form said liquid products. Thereafter, the carbonaceous materials formed and suspended in the molten medium during the conversion operation are contacted with a gasifying reagent such as a gaseous stream containing elemental or combined oxygen, e.g., air, carbon dioxide, steam, and mixtures thereof, at a temperature in the range from about the melting point of said medium to about 2,000F. for a period of time in order to regenerate the molten medium.

BRIEF DESCRIPTION OF THE DRAWING The FIGURE is a flow plan of an integrated cracking- /gasification process unit for cracking hydrocarboon feedstocks to predominantly liquid products.

The regenerable molten medium of the instant invention comprises a glass-forming oxide (or oxide precursor), by which is meant an oxide of silicon, boron, phosphorus, molybdenum, tungsten, vanadium, and mixtures. thereof. An oxide of boron is the most preferred glass-forming material.

The glass-forming oxides are employed in combination with an alkali metal (Group IA) carbonate, that is, a carbonate of lithium, potassium, sodium, rubidium, cesium or mixtures thereof. The molten medium may additionally contain other Group IA or IIA constituents such as the oxides, hydroxides, sulfides, sulfates or sulfites or sodium, lithium, potassium, cesium, rubidium, magnesium, calcium, strontium and barium. Alkali metal sulfides, sulfites and sulfates are formed in situ during the course of the conversion and/or subsequent gasification reactions by the reaction of sulfur contaminants of the feedstock with the alkali metal constituents of the melt. Alkali metal oxides are also generated in situ by reaction of carbon with alkali metal carbonates. Alkali metal hydroxides may be formed if water is present in the conversion of gasification zones. The concentration of the glass-forming oxide in the total molten medium is maintained between about 0.1 to 25 wt. percent preferably 1 to 20 wt. percent, most preferably 1 to 12 wt. percent, calculated as the oxide thereof, e.g., B203, V205, M003, W03, siogand P205, and based on total molten medium. It should be recognized that the glass-forming oxide element, e.g., boron, may exist in various valence states at various points in the process. Accordingly, the expression oxide of boron, etc., is intended to encompass any oxide of the applicable element.

The advantage of converting a heavy, metals (Nl,V,Fe) nitrogen, coke precursor and sulfur contaiminated hydrocarbon feedstock in the above mentioned molten medium, in addition to providing the heat transfer medium for the conversion of the heavy hydrocarbon feedstock to the predominantly liquid hydrocarbon products, lies in the ability of said medium to: (a) suspend the carbonaceous materials formed in situ during the conversion operation uniformly throughout the melt, (b) abstract the above-mentioned contaminants from the hydrocarbon materials being treated, and (c) thereafter, upon contact with a gasifying reagent at elevated temperatures to promote the rapid gasification of said carbonaceous materials. Accordingly, the instant invention attains a higher conversion of the heavy hydrocarbon feedstocks to predominantly liquid hydrocarbons than that which is obtainable with more conventional methods such as visbreaking. This is due to the fact that the conversions that are obtained by conventional thermal pyrolysis techniques such as visbreaking are normally quite low in view of the fact that such conversion processes must be carried out at low temperatures. Attempts to conduct such processes at higher temperatures in order to obtain higher conversions are limited by the formation of carbonaceous materials such as coke with accompanying operability problems. Accordingly, the molten medium of the instant invention allows one to conduct such conversion processes at higher temperatures, thereby obtaining higher conversions to the predominantly liquid products in view of the fact that the carbonaceous materials formed during said conversion process may be gasified by contacting said carbonaceous materials with a gasifying reagent, as hereinafter defined.

In addition to promoting the gasification rate of the carbonaceous materials formed during the conversion process, the molten medium of the instant invention offers the additional advantages of significantly lowering the emission of pollutants into the atmosphere by absorbing or reacting with at leat a portion of thesulfur and/or sulfur compounds produced during the actual cracking or conversion operation and/or during the combustion of carbonaceous material during the gasification phase of the process. The liquid hydrocarbon products formed with the conversion process of the instant invention contain a significantly reduced amount of heavy metals, nitrogen compounds and coke precursors compared to that originally contained in the heavy hydrocarbon feed. Furthermore, the molten medium of the instant invention possesses good thermal conductivity to allow efficient heat transfer.

As stated above, the molten medium may contain other components such as ash constituents, metallic and nonmetallic oxides, sulfides, sulfites, sulfates and various other salts in varying amounts so long as the medium is molten at the hydrocarbon conversion conditions of the instant invention, i.e., less than about 1,200F., and preferably from about 600 to less than about l,200F., and more preferably from about 700 to about l,lOOF. and provided that a sufficient amount of glass-forming oxide is employed to disperse byproduct carbonaceous materials (coke). One skilled in the art will readily determine the applicable components as well as the stoichiometry of the glass-forming oxides to said components which will be required in order to form the regenerable molten medium as described above. Further, various filler materials, catalysts or promoters may be added to the melt.

It is to be understood that although the molten medium of the instant invention is described throughout the specification in terms of an alkali metal carbonate and the glass-forming oxides, it is clearly within the scope of this invention to employ and define the molten medium of this invention with respect to the compounds, i.e., the salt formed when a glass-forming oxid is heated to the molten state in combination with the alkali metal carbonate or other alkali metal compound. For example, a molten medium consisting of an alkali metal carbonate (m CO and boron oxide as the glassforming oxide can also be expressed in the molten state as a borate, on the basis of the following reaction:

B203 M2CO3 M20.B203 CO Accordingly, is within the purview of the instant invention to employ as the molten medium of this invention an alkali metal carbonate and a glass-forming oxide, as defined above, in combination with an alkali metal or an alkali metal salt of the glass-forming oxide employed, e.g., alkali metal borate. It is to be noted that any of the melts of this invention may be, prepared by fusing any combination of raw materials, which upon heating will form a glass-forming oxide either alone or in combination with an alkali metal reagent.

Individual regenerable molten media that are most preferred are those obtained when boron oxide is employed as the glass-forming oxide. The most preferred melt system of the instant invention comprises boron oxide in combination with a carbonate of lithium, sodium and mixtures thereof. The most preferred alkali metal carbonate reagent is a mixture of a major amount of sodium carbonate and a minor amount of lithium carbonate or a mixture of lithium carbonate, sodium carbonate and potassium carbonate.

In a process of this invention a wide variety of feedstocks may be converted to produce predominantly liquid hydrocarbon products. Generally, the hydrocarbon feedstocks of the instant invention are heavy hydrocarbon feedstocks that contain 2 to 6 wt. percent sulfur such as crude oils, heavy residua, atmospheric and vacuum residua, crude bottoms, pitch, asphalt, other vheavy hydrocarbon pitch-forming residua, coal, coal tar or distillate, natural tars including mixtures thereof. Preferably, at least a portion of the heavy hydrocarbon feedstocks boils above about 650F. at atmospheric pressure. Most preferably, the hydrocarbon feedstocks that can be employed in the practice of the instant invention are crude oils, aromatic tars, atmospheric or vacuum residua containing materials boiling above about 650F. at atmospheric pressure.

While not essential to the reaction, an inert diluent can be employed in order to regulate the hydrocarbon partial pressure in the molten media conversion zone. The inert diluent should normally be employed in a molar ratio from about 1 to about moles of diluent per mole of hydrocarbon feedstock, and more preferably from about 1 to about 10 moles of diluent per mole of hydrocarbon feed. Illustrative, nonlimiting examples of the diluents that may be employed in the practice of the instant invention include helium, carbon dioxide, nitrogen, steam, methane, and the like.

As mentioned above, the conversion process of the instant invention results in the formation of predominantly liquid (at atmospheric pressure) hydrocarbon products. The conversion of the above-described heavy hydrocarbon feedstocks results in upgrading said feedstocks, by which is meant that a higher precentage, i.e., above 60, and more preferably above 80 weight percent of the material boiling above a temperature of 975F. (at atmospheric pressure) is converted to lower boiling liquid hydrocarbon products and coke. Such an unexpectedly high conversion to liquid hydrocarbon products by the practice of the instant invention is to be contrasted with the more conventional mild pyrolysis techniques for converting heavy hydrocarbon feedstocks such as visbreaking and hydrovisbreaking which normally result in below about 50 weight percent conversions of materials boiling above about 975F. Normally, the amount of materials having four carbon atoms and lighter (C,) formed in accordance with the practice of the instant invention is usually below wt. percent of the total feedstock and the amount of gas oil (boiling between about 430 to 650 F. at atmospheric pressure) formed by the process of this invention is normally in the range of from about 10 to 30 wt. percent of the total feedstock.

Depending upon the temperature and the specific type of hydrocarbon feedstock, the weight ratio of molten medium to hydrocarbon in the reaction zone varies in the range of from 0.1 to l to about 100 to 1. and preferably from 5 to l to to l. The reaction may be conducted at pressures ranging from subatmospheric to about 200 atmospheres, preferably from about 1 to about 30 atmospheres. The reaction time is expressed in the amount of time the feedstock is in contact with the melt, i.e.. residence time is in the range of from about 0.001 to about 6 hours, and more preferably from about 0.1 to about 3 hours,

After the hydrocarbon feedstock has been converted in the molten medium at the desired temperature and pressure, the hydrocarbon effluent from the reaction zone is cooled to condense and separate liquid produets from the gaseous products containing light olefins. The significant advantage of the instant invention is that the carbonaceous materials (coke) which are formed during the conversion process become suspended in the molten medium and can subsequently be gasified by contacting the melt with a gasifying reagent such as a gaseous stream containing free or combined oxygen. i.e., air, steam, carbon dioxide and mixtures thereof, at elevated temperatures in order to rapidly regenerate the stable molten medium. The carbonaceous materials that are formed during the thermal cracking reaction may be generally described as solid particlelike materials having a high carbon content such as those materials normally formed during high temperature pyrolysis of organic compounds.

The term gasification as used herein describes the contacting of the carbonaceous materials in the molten media with a reagent containing elemental or chemically combined oxygen such as air, steam, carbon dioxide, and mixtures thereof. The gasification reaction is carried out at temperatures in the range of from above about the melting point of the molten medium up to about 2,000F. or higher and at a pressure in the range of from subatmospheric to about 100 atmospheres. More preferably, the temperature at which the gasification reaction is carried out is in the range of from about 1,000 to about 1,800F. and at a pressure in the range of from about 1 to about 30 atmospheres.

Normally, the amount of oxygen which must be present in the gaseous stream containing free or combined oxygen in order to effectuate the gasification of the carbonaceous materials is in the range of from about 1 to about 100 weight percent oxygen, and more preferably from about 10 to about 25 weight percent oxygen. Normally, the gaseous stream containing oxygen is passed through the melt at a rate of from less than about 0.01 w./w./hr. to about 100 w./w./hr. More preferably, th rate at which the gaseous stream is passed through the melt system of the instant invention is in the range of from about 0.01 w./w./hr. to about 10 w./w./hr. Preferably air is employed as the gaseous stream containing oxygen in order' to effect a rapid regeneration of the molten medium.

Steam or carbon dioxide, either alone or in admixture with oxygen may also be employed to gasify the cabonaceous materials present in the molten medium of the instant invention. However, as is appreciated in the art, the different gasification reagents mentioned above will each gasify the carbonaceous material at different rates. Generally, the presence of free elemental oxygen in the melt will result in higher gasification rates than with other reagents such as steam or CO v Thus, when steam or C0,, is employed as the gasification reagent, more severe conditions, e.g., higher temperatures and longer residence time, will be required in order to achieve gasification rates equivalent to or higher than when, for example, air or oxygen is employed as the gasification reagent.

The specific gasification rate of the carbonaceous materials in individual regenerable molten media, as

defined by the amount of carbonaceous material which is gasified per hour per cubic foot of melt, is dependent upon the temperature at which the gasification process is carried out, as well as the resident time ofthe oxygen containing gas or steam in the melt, the concentration of carbonaceous material in the melt. and feed rate of oxygen containing gas into the media. As a general rule, the carbon gasification rate increases as the temperature of the melt, concentrations of carbonaceous materials and feed rate or the oxygen-containing gas increase. Preferably, the concentration of carbonaceous materials in the molten medium is maintained in the range of from about 0.1 to about 20 weight percent, preferably 1.0 to 5.0 wt. percent and most preferably from about 1.0 to 3.0 wt. percent, in order to effect a rapid gasification thereof. Accordingly, it can be seen that it is advantageous to carry out the gasification reaction process at temperatures above about 1,000F.,

' and more preferably in the range of from l,000 to 1,800F. and at an oxygen gas feed rate of 0.01 to 10 w./w./hr. in the presence of from about 1.0 to about 10 weight percent carbonaceous materials in order to effectuate a rapid gasification of the carbonaceous materials present in the melt. Such a rapid gasification will necessarily result in a rapid regeneration of the melt.

Referring now to the FIGURE, a heavy hydrocarbon residuum fraction, preferably having an initial boiling point (at atmospheric pressure) above about 650F., is introduced to cracking zone 2 via feed line 1. Within the cracking zone is maintained a molten bed 3 containing a oxide of boron and an alkali metal carbonate wardly through melt 3 by introducing the feedstock at a point below the upper level of the molten media. Means should be provided to secure intimate contacting of the feed with the melt. The temperature of the molten medium 3 is maintained below about 1,200F.

After the hydrocarbon feedstock has been at least partially reduced to lighter products through contact with the hot molten medium 3, the resulting cracked products pass overhead from cracking zone 2 via line 4 The cracked products may be cooled by indirect heat exchange or through contact with a quench medium introduced via line 5. If desired, the cracked products may be passed directly to a fractionation facility via line 6.

In the cracking operation a portion of the hydrocarbon feedstock is converted to coke materials. The instant melt compositions suspend the coke by-product within the melt. The coke materials are removed from the melt by a gasification step involving contacting the coke containing melt with an oxidizing gas. In the process of the present invention, the molten medium that contains suspended carbonaceous material is withdrawn rom cracking zone 2 by way of line 7 and introduced to gasification zone 8. Preferably, a vapor lift is used to circulate the melt between the cracking zone and the gasification zone. Within gasification zone 8, the coke-containing molten medium 9 is contacted with a reagent introduced into the gasification zone 8 via line 10. Preferably the reagent is elemental oxygen (or a gas stream containing elemental oxygen), steam or carbon dioxide. During contact with the gasifying reagent, the temperature within the gasification zone may be brought to about 2,000F.

During gasification, all or preferably a portion of the coke or carbonaceous material contained in the melt is combusted and the gasification products carried overhead via line 11. The chemical composition of the overhead gaseous effluent is dependent on the type of gasifying reagent employed. When oxygen or an oxygencontaining gas is employed, only a minor proportion of the total gaseous effluent is made up of sulfurbearing materials. This result is believed to be achieved because the sulfur oxides formed during gasification react with a portion of the alkali metal carbonate constituents ofthe melt to form metal sulfites or sulfates. Upon recycle ofthe gasified melt tothe cracking zone via line 12, the inorganic sulfurbearing materials are believed to be reduced to the corresponding sulfides due to the renewed presence of carbonaceous material in the melt. When steam is used as the gasifying reagent at moderate temperatures, the sulfur impurites contained in the melt within the gasification zone 8 are not converted to sulfur oxides and are not absorbed or reacted with the melt constituents but, rather, are converted to hydrogen sulfide which passes overhead via line 11.

During continued use the initial charge of melt material will become contaminated with larger and larger amounts of sulfur and ash-forming impurities. It is preferred that the total sulfur concentration in the molten medium be maintained below about 5.0 wt. percent, preferably between about 0.25 to 2.0 wt. percent, based on total molten medium. Accordingly, to maintain the melt at the desired sulfur level and/or to diminish ash concentrations, a portion of the contaminated melt must be withdrawn from the system and replaced with fresh melt or, alternatively, reconditioned and returned to the system. One technique for reconditioning the contaminated melt is depicted in the FIGURE. Specifically, a minor quantity of contaminated melt material is withdrawn from line 7 and passed to a sulfur recovery zone 14 wherein it is contacted with carbon dioxide and steam that are introducd via Inc 15. Typically, the melt 16 contained within zone 14 is treated with the carbon dioxide/steam reagents at temperatures in the range of from about 800 to l,800F. Provided that the bulk of the sulfur contaminants present in the melt are in the form of sulfides, contacting with the steam/carbon dioxide mixture will convert the sulfide ion to hydrogen sulfide which is removed from the treating zone via line 17. If the bulk of the sulfur sent to zone 14 is not in a metal sulfide form, it is necessary, for maximum sulfur removal, to reduce the sulfur present in the melt to a sulfide form in a reducing zone located prior to zone 14.

After treatment in zone 14, the molten media having reduced sulfur content is withdrawn via line 18 and returned to the system via line 19. A portion of the treated effluent in line 19 may be withdrawn from the system via line 20 for treatment for the removal of ash constituents. The resulting melt may be returned to the system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Example A series of tests were conducted to demonstrate the efficacy of alkali carbonate melts containing boron oxide. The initial alkaline reagent portion of the boroncontaining melt was composed of about 43 mole percent lithium carbonate, 3] mole percent sodium carbonate, and 26 mole percent potassium carbonate. Sufficient boron oxide was added to the melt to bring the molar ratio of alkali carbonates to boron oxide to 4:] (15 wt. percent B 0 on total melt). The carbonates/- boron oxide mixture was heated in a graphite-lined reactor to a temperature ranging from 1,500 to l,600F. over a period of from 1 2 hours until a homogeneous melt was secured. Thereafter the melt (melting point of about 800F. was solidified by cooling, and 2,000 grams of melt particles were introduced into agraphitelined reactor that was equipped with an anchor-type stirrer and means for introducing feedstock and means for withdrawing liquid and gaseous product materials.

In each test run, 600 grams of feedstock comprising a heavy Arabian (Safaniya) vacuum residual material having an initial boiling point of about 980F. and an inert diluent was continuously introduced into the reaction zone which was maintained at a temperature indicated in Table l and atmospheric pressure over a forty minute period The feed material exhibited and API gravity of 4.6, a Conradson carbon residue number (CCR) of 21 wt. percent and contained about 0.5 wt. percent nitrogen, 4.8 wt. percent sulfur and 300 ppm metals. The feed material was introduced into the bottom of the reactor through the feed inlet and was brought into intimate contact with the stirred melt. Liquid and gaseous products were continuously bled from the top of the reactor and the liquid products condensed and fractionated in vacuum for subsequent analysis. The residence time of the product materials within the reaction zone varied from an average of about 20 minutes for coke materials to several seconds for lighter products.

The results of the experiments are set fort in Table l.

Table I Run A B C Reaction Conditions Temperature, "F. 1000 l l l 100 Diluent Steam Helium Steam Coke Dispersion Good Good Good Product Yield, wt.

Conversion to 980F 50-80 50-80 50-80 Li uid" 73 72 75 Co e 2O l6 15 Gas, C,/C 7 l2 l0 Product Quaiit Total Liguld Distillate API Gravity 23-28 23-28 23-28 S, wt. 3.54 3.5-4' 3.5-4 CCR, wt. 5 l2 5l2 v5--l2 Metals, ppm 20 20 20 Gas Composition, wt.

CO 1 7 l C, 5 l2 7 CO 54 23 37 C 2 8 5 C 7 8 5 H 5 3 l C l2 l7 8 C 9 9 6 C 7 l6 3O Does not include i 371 C material carried over with gas, Based on dry gasv What is claimed:

1. A process for cracking a heavy hydrocarbon feedstock comprising a component selected from the group consisting of crude oils and residua containing from about 2 to 6 wt. percent sulfur to lighter hydrocarbon materials which comprises contacting said heavy hydrocarbon feedstock with a regenerable alkali metal carbonate molten medium containing from 0.1 to 25 wt. percent, calculated as oxide and based on total molten medium, ofa glass-forming oxide selected from the group consisting of oxides of boron, phosphorus, vanadium, silicon, tungsten and molybdenum, at a temperature in the range of from about the melting point of the molten medium to less than 1,200F. to form predominantly liquid hydrocarbon products and carbonaceous materials, said carbonaceous materials being suspended uniformly in the molten medium, and thereafter gasifying at least a portion of said carbonaceous materials formed during said conversion process by contacting said molten medium containing said carbonaceous materials with oxygen, carbon dioxide, steam or mixtures thereof at a temperature in the range of from about the melting point of said molten medium to about 2,000F.

2. The process of claim 1 wherein the temperature of the molten medium during contact with heavy hydrocarbon feedstock is maintained in the range of from about 700 to about 1,100F.

3. The process of claim 1 wherein at least a portion of said heavy hydrocarbon feedstock boils above about 650F. at atmospheric pressure.

4. The process of claim 1 wherein said glass-forming oxide is an oxide of boron.

5. The process of claim 1 wherein said alkali metai carbonate is a mixture of sodium carbonate and lithium carbonate or a mixture of sodium carbonate, lithium carbonate and potassium carbonate.

6. The process of claim 1 wherein said molten medium contains from about 1 20 wt. percent, calculated as oxide and based on total molten medium, of an oxide or boron.

7. The process of claim 6 wherein said carbonaceous materials are contacted with a gas stream containing from about 10 to about 25 wt. percent oxygen.

8. The process of claim 7 wherein said gas stream is air.

9. The process of claim 6 wherein said carbonaceous materials are contacted with'steam.

10. A process for cracking a heavy hydrocarbon feedstock comprising a component selected from the group consisting of crude oils and residua containing 2 to 6 wt. percent sulfur and at least a portion of which boils above about 650F. at atmospheric pressure to lighter hydrocarbon materials which comprises contacting said feedstock with a regenerable alkali metal carbonate molten medium comprising a mixture of lithium and sodium carbonates containing from 1 to 20 wt. percent, calculated as oxide and based on the total molten medium, of an oxide of boron at a temperature in the range of from about the melting point of the molten medium to less than l,200F. to form predominantly liquid hydrocarbon products and carbonaceous materials, at least a portion of said carbonaceous materials formed in said conversion being dispersed uniformly in said molten medium in amounts varying from about 1.0 to 5.0 wt. percent based on total molten medium, and thereafter gasifying at least a portion of said carbonaceous materials in said molten medium by contacting the same with an oxygen-containing gas at a temperature in the range of from about the melting point of said molten medium to about 2,000F.

11. The process of claim 1 'wherein said molten me dium is regenerated at a temperature in the range of from about l,00OF. to about 1,800F.

Claims

1. A PROCESS FOR CRACKING A HEAVY HYDROCARBON FEEDSTOCK COMPRISING A COMPONENT SELECTED FROM THE GROUP CONSISTING OF CRUDE OILS AND RESIDUA CONTAINING FROM ABOUT 2 TO 6 WT. PERCENT SULFUR TO LIGHTER HYDROCARBON MATERIALS WHICH COMPRISES CONTACTING SAID HEAVY HYDROCARBON FEEDSTOCK WITH A REGENERABLE ALKALI METAL CARBONATE MOLTEN MEDIUM CONTAINING FROM 0.1 TO 25 WT. PERCENT, CALCULATED AS OXIDE AND BASED ON TOTAL MOLTEN MEDIUM, OF A GLASS-FORMING OXIDE SELECTED FROM THE GROUP CONSISTING OF OXIDES OF BORON, PHOSPHOROUS, VANADIUM, SILICON, TUGSTEN AND MOLYBDENUM, AT A TEMPERATURE IN THE RANGE OF FROM ABOUT THE MELTING POINT OF THE MOLTEN MEDIUM TO LESS THAN 1,200*F. TO FORM PREDOMINANTLY LIQUID HYDROCARBON PRODUCTS AND CARBONACEOUS MATERIALS, SAID CARBONACEOUS MATERIALS BEING SUSPENDED UNIFORMLY IN THE MOLTEN MEDIUM, AND THEREAFTER GASIFYING AT LEAST A PORTION OF SAID CARBONACEOUS MATERIALS FORMED DURING SAID CONVERSION PROCESS BY CONTACTING SAID MOLTEN MEDIUM CONTAINING SAID CARBONACEOUS MATERIALS WITH OXYGEN, CARBON DIOXIDE, STEAM OR MIXTURES THEREOF AT A TEMPERATURE IN THE RANGE OF FROM ABOUT THE MELTING POINT OF SAID MOLTEN MEDIUM TO ABOUT 2,000*F.

2. The process of claim 1 wherein the temperature of the molten medium during contact with heavy hydrocarbon feedstock is maintained in the range of from about 700* to about 1,100*F.

3. The process of claim 1 wherein at least a portion of said heavy hydrocarbon feedstock boils above about 650*F. at atmospheric pressure.

5. The process of claim 1 wherein said alkali metal carbonate is a mixture of sodium carbonate and lithium carbonate or a mixture of sodium carbonate, lithium carbonate and potassium carbonate.

6. The process of claim 1 wherein said molten medium contains from about 1 - 20 wt. percent, calculated as oxide and based on total molten medium, of an oxide or boron.

8. The process of claim 7 wherein said gas stream is air.

9. The process of claim 6 wherein said carbonaceous materials are contacted with steam.

10. A process for cracking a heavy hydrocarbon feedstock comprising a component selected from the group consisting of crude oils and residua containing 2 to 6 wt. percent sulfur and at least a portion of which boils above about 650*F. at atmospheric pressure to lighter hydrocarbon materials which comprises contacting said feedstock with a regenerable alkali metal carbonate molten medium comprising a mixture of lithium and sodium carbonates containing from 1 to 20 wt. percent, calculated as oxide and based on the total molten medium, of an oxide of boron at a temperature in the range of from about the melting point of the molten medium to less than 1,200*F. to form predominantly liquid hydrocarbon products and carbonaceous materials, at least a portion of said carbonaceous materials formed in said conversion being dispersed uniformly in said molten medium in amounts varying from about 1.0 to 5.0 wt. percent based on total molten medium, and thereafter gasifying at least a portion of said carbonaceous materials in said molten medium by contacting the same with an oxygen-containing gas at a temperature in the range of from about the melting point of said molten medium to about 2,000*F.

11. The process of claim 1 wherein said molten medium is regenerated at a temperature in the range of from about 1,000*F. to about 1,800*F.