US3793192A - Catalytic cracking process - Google Patents

Catalytic cracking process Download PDF

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Publication number
US3793192A
US3793192A US00244249A US3793192DA US3793192A US 3793192 A US3793192 A US 3793192A US 00244249 A US00244249 A US 00244249A US 3793192D A US3793192D A US 3793192DA US 3793192 A US3793192 A US 3793192A
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Prior art keywords
fraction
reforming
catalyst
reformate
cracking
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US00244249A
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English (en)
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E Gladrow
C Kimberlin
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ExxonMobil Technology and Engineering Co
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Exxon Research and Engineering Co
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    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G63/00—Treatment of naphtha by at least one reforming process and at least one other conversion process
    • C10G63/02—Treatment of naphtha by at least one reforming process and at least one other conversion process plural serial stages only
    • C10G63/04—Treatment of naphtha by at least one reforming process and at least one other conversion process plural serial stages only including at least one cracking step
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G61/00—Treatment of naphtha by at least one reforming process and at least one process of refining in the absence of hydrogen
    • C10G61/02—Treatment of naphtha by at least one reforming process and at least one process of refining in the absence of hydrogen plural serial stages only
    • C10G61/04—Treatment of naphtha by at least one reforming process and at least one process of refining in the absence of hydrogen plural serial stages only the refining step being an extraction
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G OR C10K; LIQUIFIED PETROLEUM GAS; USE OF ADDITIVES TO FUELS OR FIRES; FIRE-LIGHTERS
    • C10L1/00—Liquid carbonaceous fuels
    • C10L1/04—Liquid carbonaceous fuels essentially based on blends of hydrocarbons
    • C10L1/06—Liquid carbonaceous fuels essentially based on blends of hydrocarbons for spark ignition

Definitions

  • This invention relates to an improved catalytic cracking process. More particularly, this invention relates to a catalytic cracking process in combination with naphtha reforming to provide a high yield of high clear octane gasoline.
  • octane number of catalytically cracked naphtha is dependent upon a number of variables, for example, feedstock quality and composition, conversion level or cracking severity, catalyst type and composition and cracking temperature.
  • catalytic cracking operations can be controlled to obtain the maximum C /43OF. naphtha yield. Beyond this point further increases in cracking severity or conversion do not result in further increases in naphtha yield.
  • several key compositional effects occur which make the naphtha particularly amenable to the production of high clear octane mogas.
  • the aromatic content of the naphtha increases with severity which improves naphtha octane.
  • the naphthenic content of the naphtha is not reduced at high severity.
  • the naphthenic content can be easily reformed to high clear octane aromatics at low reformer severities.
  • the olefin content of the naphtha is greatly reduced at high severities. This is advantageous since olefins are potential atmospheric pollutants.
  • low olefin content permits reforming without prior hydrotreating, providing a sulfur tolerant reforming catalyst is employed.
  • the final gasoline so obtained is low in olefins with a high content of aromatics and isoparaffins and exhibits low potential for polluting air when burned.
  • FIG. 1 is a graphical representation of the variation in RON clear octane number versus boiling point for a catalytically cracked naphtha;
  • FIG. 2 is a schematic flow diagram illustrating one embodiment of the present invention.
  • the light and heavy fractions of a catnaphtha i.e., the C /l80F. and the 270/430F. fractions which constitute about 30-40 volume percent and 25-30 volume percent, respectively, of the total naphtha are of high octane; whereas, in sharp contrast, the intermediate portion (l80/270F) is of very low octane.
  • the light fraction is largely isopentane and C olefins and the heavy fraction are largely aromatics, all being of fairly high octane.
  • the intermediate portion has been found to contain major amounts of naphthenes, a low octane material, per se, but one which can be readily reformed to aromatics.
  • an intermediate fraction can be easily reformed even at very mild conditions to obtain a high octane product. It has also been found that the intermediate fraction must be separated from the light fraction of the total cat-naphtha prior to reforming since reforming of the light fraction will produce C s and gas, thereby lowering C liquid yield.
  • this low octane fraction can be upgraded by reforming said fraction and subsequently reblending the reformate with the other high octane fractions from the catcracker to produce high quality gasoline.
  • the feedstock which is preferably a low sulfur-containing feedstock such as, for example, a virgin gas oil feed, typically material boiling between 600-1,050F.
  • FVT is preheated to somewhat below cracking temperatures in heater 2 and is then transferred to riser cracker 4 via line 3 and then to the dense bed of caalyst 6 contained within the fluid catalytic cracker shown generally as 8.
  • the preferred catalysts for use in the catalytic cracking unit are of the crystalline aluminosilicate zeolite types.
  • the chemical formula of the anhydrous crystalline zeolites employed in the present invention expressed in terms of moles may be represented as:
  • zeolites include synthetic crystalline aluminosilicates, naturally occurring crystalline aluminosilicates and treated clays in which a substantial portion of the clay has been converted to crystalline zeolite. Synthetic materials include faujasites and mordenites.
  • Natural materials are erionite, analcite, faujasite, phillipsite, clinoptilolite, chabazite, gmelinite, mordenite and mixtures thereof containing or treated .to contain 5-95. percent crystalline alumino-silicate having an ordered structure. All or a portion of the cations of the zeolites such as sodium cations can be replaced with hydrogen ions, ammonium ions or metal cations such as rare earths, manganese, cobalt, zinc and other metals of Group I to VIII of the Periodic Table.
  • the catalyst can be one of the matrix types, i.e.,-one in which the zeolite crystals are coated with or encapsulated in a silica-alumina gel, silica gel, clay or mixtures thereof.
  • Matrix catalysts contain 5-60 percent, preferably 5 to percent crystalline zeolite.
  • the catalyst is generally particulate in nature.
  • the catalyst particles can be in the form of powder, granules, spray dried microspheres, or the like and may be of a size within the range of from about 5 to about 250 microns.
  • the catalyst particles should be sufficiently uniform in particle size to permit easy handling and avoid any tendency to classify in the circulating catalyst system.
  • Hot, regenerated catalyst is admixed with the feed in the riser cracker 4 wherein it completes preheating of the charged feedstock which was partially preheated in heater 2.
  • the oil is flash vaporized and forms a suspended fluidized catalyst-hydrocarbon mixtures which is forced through the riser cracker 4 into the dense bed of catalyst 6 maintained within the reactor.
  • the catalyst settles to a finite level and forms a fluidized bed, the depth of which regulates the time of reaction and can be variedto provide the desired degree of cracking.
  • This bed is maintained in a fluid, turbulent condition by the entering feed vapors which continuously pass upwardly, thereby effecting contact of oil with catalyst and producing a substantially unforrn temperature in the range of about 700-l,200F. and preferably 800l,000F. with increasing temperature favoring cracking or conversion of feed to lower boiling products.
  • the liquid hourly space velocity ranges between about 0.5-20 V/l-Ir./V, and preferably ranges from 1-8 V/Hr./V.
  • the catalyst- :oil ratio ranges between about 2:1 and 20:1 and can vary depending upon the type of process employed, e.
  • the approximate pressure can range from subatmosphereic to several atmospheres. Preferably, the pressure ranges from about 5-100 psig, and more preferably 5-20 psig. Increasing the pressure generally reduces the octane quality of the gasoline product and increases the production of coke at a given conversion level.
  • the spent catalyst laden with coke is continuously and automatically withdrawn through the stripping zone 10 at the bottom of the reactor where the absorbed and entrained feed vapors are stripped from the catalyst by countercurrent contact with a stripping gas admitted to the stripping zone through line 12.
  • the stripped catalyst is passed via line 13 into regenerator 15. En route, the catalyst is picked up by a stream of air charged through line 14 and is carried into the regenerator wherein the carbon is burned off the catalyst at temperatures of about 1,100F. or higher.
  • the entrained catalyst is removed via cyclone l6 and flue gas exits via stack 18.
  • the hot regenerated catalyst leaves the bottom of the regenerator taking with it much of the heat of combustion and is recycled via line 20 to the catalytic cracking unit.
  • the cracked products together with the stripping gas pass through cyclone 22 which collects entrained catalyst and returns it to the dense bed.
  • cyclone 22 Upon leaving cyclone 22, vapors pass from the reactor to fractionator 24 via line 23 which separates the catalytically cracked naphtha into three streams: a light fraction boiling in the C l F. range, an intermediate fraction locking in the l80270F. range and a heavy fraction boiling in the 270430F. range.
  • the light fraction and the heavy fraction are sent directly to blending tank 26; whereas, the intermediate fraction can be fed directly to a reforming unit through line 28 wherein it is mixed with recycle gas and partially preheated by indirect heat exchange with the product stream in heat exchanger 30.
  • Final preheat is obtained in the preheat furnace 32.
  • reactor inlet temperatures may be as low as 825F.
  • the maximum reactor inlet temperature is set by rapid catalyst deactivation. This is generally in the range of about 1,000F.
  • tempera tures in the reforming reactors range between 825F. and 975F.
  • reforming temperatures range between 925F. to 975F.
  • the reactants generally pass through at least one and generally several reforming reactors 34, 36 and 38 at space velocities ranging between about 1 to 5 W/l-lr./W, at pressures between about IUD-1,000 psig, preferably 200-800 psig, and at hydrogen rates between about 4,000l2,000 SCF/B.
  • the reforming reaction is largely an endothermic reaction. This heat of reaction is in the order of 200 to 350 BTU/1b., depending on the type of feed. Since the individual fixed bed reactors operate adiabatically, the high endothermicity of the reforming reactions, particularly in the lead reactors, results in a large temperature drop. As temperature falls, the reforming reaction rate decreases. Thus, to maintain a relatively high rate of reaction and keep catalyst requirements at a minimum, intermediate reheat furnaces 40 and 42 are required between each of the reactors.
  • the reactants After passage through the reactors, the reactants are cooled by heat exchange with the feed stream in heat exchanger 30. Final cooling is obtained in condenser 44.
  • the gas-liquid stream then passes into a high pressure separator 46 from which unstabilized reformate is withdrawn through line 48 and the major portion of the gas is removed via line 50, dried in dryer 52 and then recycled.
  • the excess gas, called make or tail gas then flows to an absorber (not shown) for recovery of C and heavier hydrocarbons.
  • the reformate passes via line 48 to blending tank 26 wherein it is blended with both the light fraction and the heavy fraction from fractionator 24 to form a high octane gasoline product.
  • a swing reactor 54 is manifolded to the reforming system to replace the reactor which is to be regenerated.
  • a reactor is to be regenerated, it is taken off stream and replaced by the swing reactor 54.
  • the reactor to be regenerated is first purged with recycle gas and then with flue gas from an inert gas generator. After purging, flue gas is circulated through the regeneration equipment and air is added. Flame front temperatures are limited to about 1,000F. After the carbon burns, oxygen content of the flue gas is generally increased to about 6 percent and the catalyst is dried, chlorine treated and purged before it is replaced on stream.
  • Conventional reforming catalysts can be employed, for example, deposits of activated alumina with minor proportions of platinum, palladium, rhodium, molybdenum oxide, vanadium oxide or chromium oxide can be employed.
  • the catalysts comprise activated alumina containing minor proportions of halogen such as chlorine, fluorine and the like and minor proportions, for example, from about 0.05 percent to about 1 percent, of platinum.
  • Platinum supported on steam ac-- tivated silica or silica-alumina can also be employed.
  • catalysts which are sulfur-tolerant and can be employed to advantage comprise mixtures of Group VI and iron group metals, e.g., cobalt molybdate supported on activated alumina, bauxite or other clays.
  • Such catalysts generally contain from about 2 percent to about 8 precent by weight C00, and between from about 4 percent to about 20% M00 Additionally, sulfided platinum or molybdenum can be employed.
  • gasoline having research clear octane values of 95 and higher can be readily achieved.
  • the naphthene content of a l/270F. mid-boiling naphtha cut obtained by cracking a South Louisiana gas oil over an equilibrium zeolite catalyst (comprising a mixture of a zeolite in a matrix of silica-alumina plus clay) to an 80 volume percent 430F. conversion is about 30%.
  • the octane improvement in this cut obtained by reforming at low severity to convert naphthenes to aromatics in accordance with the present invention is about 7 RON numbers, or an increase from 88 to RON. Aromatic content thereby increased from approximately 20 percent to about 50 percent by volume.
  • the reformer instead of passing the entire catalytically cracked low octane, or l80/270F. fraction, to the reformer, it can be extracted to remove the aromatics which can be directly blended with the light and heavy fractions. In this manner, only the raffinate is sent to reforming. The reformate is then blended with the light and heavy fractions and the aromatic extract.
  • catalyst employed in the reforming zone comprises activated alumina with from about 0. 05% to about 1% of plati- 66111553 from about 0.05 percent to about 1 percent of a halogen.
  • catalyst employed in the reforming zone comprises a mixture of Group VI and iron group metals supported on activated alumina.

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  • Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)
US00244249A 1972-04-14 1972-04-14 Catalytic cracking process Expired - Lifetime US3793192A (en)

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3883418A (en) * 1973-01-02 1975-05-13 Phillips Petroleum Co Lead free motor fuel production
US5021143A (en) * 1988-08-02 1991-06-04 Institut Francais Du Petrole Process of fractionation and extraction of hydrocarbons allowing obtaining a cut of increased octane index and a kerosene of improved smoke point
US5409595A (en) * 1993-08-16 1995-04-25 Mobil Oil Corporation Heavy naphtha conversion
US20070251861A1 (en) * 2006-04-26 2007-11-01 Fina Technology, Inc. Petrochemical processes
EP1650287A4 (fr) * 2003-07-04 2009-12-16 Beijing Grand Golden Bright En Procede de recombinaison d'hydrocarbures catalytiques
US20240301302A1 (en) * 2020-12-28 2024-09-12 Sabic Global Technologies B.V. Production of btx aromatics and light gas olefins from crude oil and plastic pyrolysis oil

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2740751A (en) * 1952-02-23 1956-04-03 Universal Oil Prod Co Reforming of both straight run and cracked gasolines to provide high octane fuels
US2968605A (en) * 1958-07-28 1961-01-17 American Oil Co Preparation of high octane number motor fuel blending stocks
US2970101A (en) * 1958-05-07 1961-01-31 American Oil Co Preparation of high octane number motor fuel blending stocks
US2981674A (en) * 1955-10-24 1961-04-25 Shell Oil Co Production of gasoline by thermal cracking, catalytic cracking and reforming
US2990363A (en) * 1959-02-03 1961-06-27 Socony Mobil Oil Co Inc Method of reducing variation in antiknock characteristics of fractions of full boiling range naphtha

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2740751A (en) * 1952-02-23 1956-04-03 Universal Oil Prod Co Reforming of both straight run and cracked gasolines to provide high octane fuels
US2981674A (en) * 1955-10-24 1961-04-25 Shell Oil Co Production of gasoline by thermal cracking, catalytic cracking and reforming
US2970101A (en) * 1958-05-07 1961-01-31 American Oil Co Preparation of high octane number motor fuel blending stocks
US2968605A (en) * 1958-07-28 1961-01-17 American Oil Co Preparation of high octane number motor fuel blending stocks
US2990363A (en) * 1959-02-03 1961-06-27 Socony Mobil Oil Co Inc Method of reducing variation in antiknock characteristics of fractions of full boiling range naphtha

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3883418A (en) * 1973-01-02 1975-05-13 Phillips Petroleum Co Lead free motor fuel production
US5021143A (en) * 1988-08-02 1991-06-04 Institut Francais Du Petrole Process of fractionation and extraction of hydrocarbons allowing obtaining a cut of increased octane index and a kerosene of improved smoke point
US5409595A (en) * 1993-08-16 1995-04-25 Mobil Oil Corporation Heavy naphtha conversion
EP1650287A4 (fr) * 2003-07-04 2009-12-16 Beijing Grand Golden Bright En Procede de recombinaison d'hydrocarbures catalytiques
US20070251861A1 (en) * 2006-04-26 2007-11-01 Fina Technology, Inc. Petrochemical processes
US20240301302A1 (en) * 2020-12-28 2024-09-12 Sabic Global Technologies B.V. Production of btx aromatics and light gas olefins from crude oil and plastic pyrolysis oil

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