US3328292A - Method for catalytic conversion of hydrocarbons - Google Patents

Description

June 27, 1967 J. P. SHAMBAUGH 3,328,292

METHOD FOR CATALYTIC CONVERSION OF HYDROCARBONS Filed May 11, 1964 CHARGE 15 STOCK FILTER FRESH CATALYST Fl/EL A6 REQll/RED 56 l I l I I I 1 I I 1 ALTERNATE a 2 46 OES/REO 7'0 STORAGE United States Patent 3,328,292 METHOD FOR CATALYTIC CONVERSION (1F HYDROCARBONS James P. Shambaugh, Huntington, N.Y., assignor to Mobil 0i] Corporation, a corporation of New York Filed May 11, 1964, Ser. No. 366,477 9 Claims. (Cl. 208-120) This invention relates to improvements in the catalytic treatment of hydrocarbons and more particularly to a catalytic process and equipment for treatment of hydrocarbons in the presence of superactive catalysts.

Since the commercial development of catalytic cracking over 25 years ago, substantially all cracking operations in the industry have been of the type wherein petroleum oils boiling in the range above 400 F. have been fed in liquid form or in vapor form or mixed liquid-vapor form into catalyst-containing reactors at conditions to achieve rather high temperatures, generally in excess of 800 F. in order to crack the oils and secure petroleum oil fractions boiling in the motor fuel oil range. In those cases wherein liquid or mixed liquid-vapor feed is fed to the reactor, there appears to occur rapid vaporization of the liquid portion of the feed at the catalyst surface or before reaching the same so that in effect the feed at the moment of cracking is substantially all in vapor form. Though the development of catalytic cracking of the nature just described has been so successful as to warrant the building of gigantic installations during the past 25 years at a cost running into hundreds of millions of dollars, there yet exist a number of problems and disadvantages associated with the process even today which are still to be overcome. Thus, though the conversions obtained under the rather severe cracking conditions employed today are considered fairly satisfactory, the product selectivity and product distribution obtained at such conversions still leaves room for improvement. Conversion may be expressed as the quantity of charge to the catalytic cracking process minus the amount of recycle divided by the amount of charge. The recycle is defined as everything in the effluent boiling above gasoline. In pointing out that conversion is considered fairly satisfactory in the processes used today at conventional cracking conditions while product selectivity and product distribution are also fairly satisfactory, it would be desirable to decrease the relative quantity of coke produced during cracking and also to decrease the amount of dry gas made.

Though the above facts have suggested the desirability of conducting catalytic cracking under less severe cracking conditions, i.e., under conditions of pressure and temperature such that cracking is affected at lower temperatures, either entirely or predominantly in the liquid phase, efforts along these lines have not been satisfactory for a number of reasons. Liquid phase cracking at lower temperatures has resulted in uneconomically low reaction rates and conversions. Moreover, though the formation of gas during cracking has been reduced, there has not been a corresponding reduction in coke make. In fact, the necessity for prolongation of the period of catalyst contact, because of lower reaction rates, has sometimes resulted in even higher coke make than occurs by cracking of vapor or mixed liquid-vapor under more severe conditions.

The present invention relates to a process and apparatus which overcomes the disadvantages of the prior art in conducting catalytic cracking at lower temperatures than conventional, in a predominantly liquid phase, with a suitable catalyst. According to the present invention catalytic cracking occurs in contact with a superactive catalyst in the bottom section of a fractionating column under liquid phase cracking conditions. The catalyst ice may be continuously drawn off, regenerated and returned to the column, and the products formed in the reaction pass upwardly into the top section of the fractionator for fractionating into the desired number of product fractions, thus eliminating need for separate fractionation and in detail hereafter, is charged into the bottom section 12 of the fractionator. An inlet conduit 18 conducts the charge stock into the bottom section 12. As necessary to supply heat to the reaction catalyst slurry may be withdrawn from the bottom section 12 through outlet line 20, by a slurry pump 22, to a heater 24 and thence is returned to the bottom section 12 through line 26.

Another stream of catalyst slurry is drawn off through line 28 and is fed to a continuous filter 30 or other means of liquid-solid separation. The liquid product is removed from the separator through line 32 and may be removed to storage through line 34 or when desired to minimize the quantity of bottoms product, repumped into the bottom section 12 by pump 36 and line 26. The catalyst fromthe separator 30 in the form of filter cake, for example, may then be regenerated as for example in the heater 24; or in any other convenient form of regenerator, supplying all or a portion of the heat necessary for reaction, with supplemental fuel 35 fired into the heater 24 or the regenerator as necessary.

The catalyst may be discarded, or, after regeneration, the catalyst is reslurried at by the clarified oil from pump 36 or by fresh charge stock from line 42. The -re' slurried catalyst is returned to the bottom section 12 through line 26 after merging with the recirculated catalyst slurry from the heater 24.

The regenerated catalyst passing from the filter 30 through the heater 24 may be conveyed by a traveling grate shown schematically at 44.

The charge stock may be any hydrocarbon stream which is to be converted to a more valuable (usually lighter) product. It is contacted with the superactive catalyst 16 in the reaction zone in a predominantly liquid state. This is accomplished by operating under conditions that maintain the uncracked charge material in a liquid phase. Such conditions include temperatures in the range of 500-900 F., pressure in the range of 10 to 1000 p.s.i.a, space velocities in the range of 10-1000 equivalent weights of oil per weight of catalyst per hour (w./hr./w.), and 0.01 to 10 equivalent weights of catalyst per weight of oil (C/O).

The pressure in the reaction section of the fractionator will be controlled by conventional overhead pressure con-- trols, whereas the space velocity (w./hr./w.), catalyst to oil ratio (C/O), and recycle ratio will be controlled by the rate at which the catalyst-oil slurry is withdrawn from the tower bottom through line 20.

' When only low conversion is desired, the clarified oil from the filter 30 may be rejected as a bottom product through line 34.

Other means of regeneration other than combustion such as in the heater 24 may be utilized, such as removal of the heavy hydrocarbons by a solvent or other methods.

The top section 14 of the tower is provided with con-- ventional fractionating plates with a plurality of side streams drawn otf at 52, 54 and 56. The side stream 52 and 54 are conducted to normal stripping, cooling and product blending or further processing. The stream 56 containing gas and gasoline is subjected to the normal recovery and separation steps with the refiux being returned via line 58.

The catalysts useful in the present invention are as indicated in co-pending patent application Ser. No. 208,512 filed July 9, 1962, new superactive catalysts which have a relative activity of as high as 10,000 times that of presently used catalysts in the cracking of hydrocarbons. Although technology is not now available for achieving full use of these catalysts, it has been found that these materials exhibit product selectivity which is extremely attractice, since the ratio of gasoline yield to coke make in gas oil cracking has been found to be markedly greater than that of conventional catalysts.

Crystalline aluminosilicates are materials of ordered internal structure in which atoms of alkali metal, alkaline earth metal or metals in replacement thereof, silicon, aluminum and oxygen are arranged in a definite and consistent crystalline or ordered pattern. Such structure contains a large number of small cavities, interconnected by a number of still smaller channels. These cavities and channels are precisely uniform in size. The interstitial dimensions of openings in the crystal lattice limit the size and shape of the molecules that can enter the interior of the aluminosiilcate and it is such characteristic of many crystalline zeolites that has led to their designation as molecular sieves.

Zeolites having the above characteristics include both natural and synthetic materials, for example, chabazite, gmelinite, mesolite, ptiliolite, mordenite, natrolite, nepheline, sodalite, scapolite, lazurite, leucrite, and cancrinite. Synthetic zeolites may be of the A type, X faujasite type, Y faupasite type, T type or other well known form of molecular sieve, including ZK zeolites such as those described in copending application Ser. No. 134,841 filed Aug. 30, 1961. Preparation of various examples of such zeolites is known, having been described in the literature, for example .A type zeolite in U.S. 2,882,243 X faujasite type zeolite in U.S. 2,882,244; other types of materials in Belgium Patent No. 577,642 and in U.S. 2,950,952. As initially prepared, the metal of the aluminosilicate is an alkali metal and usually sodium. Such alkali metal is subject to base-exchange with a wide variety of other metal ions. The molecular sieve materials so obtained are unusually porous, the pores having highly uniform molecular dimensions, generally between about 3 and possibly about 15 Angstrom units in diameter. Each crystal of molecular sieve material contains literally billions of tiny cavities or cages interconnected by channels of unvarying diameter. The size, valence and amount of the metal ions in the crystal can control the effective diameter of the interconnecting channels.

At the present time, there are commercially available materials of the A series and of the X faujasite series. A synthetic zeolite known as Molecular Sieve 4A is a crystalline sodium aluminosilicate having channels of about 4 Angstroms in diameter. In the hydrated form, this material is chemically characterized by the formula:

The synthetic zeolite known as Molecular Sieve 5A is a crystalline aluminosilicate salt having channels about 5 Angstroms in diameter and in which substantially all of the 12 ions of sodium in the immediately above formula are replaced by calcium, it being understood that calcium replaces sodium in the ratio of one calcium for two sodium ions. A crystalline sodium aluminosilicate having pores approximately Angstroms in diameter is also available commercially under the name of Molecular Sieve 13X. The letter X is used to distinguish the interatomic structure of this zeolite from that of the A crystals mentioned above. As prepared, the 13X material contains water and has the unit cell formula:

sal 2)ss( 2)1os]- 2 The 13X crystal is structurally identical with faujasite,

a naturally occurring zeolite. The synthetic zeolite known as Molecular Sieve 10X is a crystalline aluminosilicate salt having channels about 10 Angstroms in diameter and in which a substantial proportion of the sodium ions of the 13X material have been replaced by calcium.

Molecular sieves of the X faujasite series are characterized by the formula:

where M is Na+, Ca++ or other metal ion-s introduced by The structure consists of a complex assembly of 192 tetrahedra in a large cubic unit cell 24.95 A. on an edge. Both the so-called X and the so-called Y type crystalline aluminosilicates are faujasites and have essentially identical crystal structures. They differ from each other only in that type Y aluminosilicate has a higher SiO A1 0 ratio than the X type aluminosilicate.

The alkali metal generally contained in the naturally occurring or synthetically prepared zeolites prescribed above may be replaced by other metal ions. Replacement is suitably accomplished by contacting the initially formed crystalline aluminosilicate with a solution of an ionizable compound of the metal ion which is to be zeolitically introduced into the molecular sieve structure for a sufficient time to bring about the extent of desired introduction of such ion. After such treatment, the ion exchanged product is water washed, dried and calcined. The extent to which exchange takes place can be controlled.

Naturally occurring or synthetic crystalline aluminosilicates may be treated to provide the superactive alumino-silicates employed in this invention by several means, such as base exchange to replace the sodium with rare earth metal compounds, by base exchange with ammonium compounds followed by heating to drive off NH ions, having an H or acid form of aluminosilicates.

by treatment with mineral acid solutions to arrive at a hydrogen or acid form, and by other means. These treatments may be followed by activity adjusting treatments, such as steaming, calcining, dilution in a matrix and other means. Explanation of the methods of preparing such catalysts is made in co-pending application Ser. No. 208,- 512 filed July 9, 1962, now abandoned.

It should be noted that the catalysts used in this invention may be a composite of the superactive aluminosilicate and a relatively inert matrix material, or it may consist only of the superactive catalyst. If the catalyst consists of a composite, it may be produced in the form of pellets, beads, or particles such as may be produced by spray drying. The matrix material may be any hydrous oxide gel, clay or the like. The matrix material used should have a high porosity in order that the reactants may obtain access to the active component in the catalyst composite. A high porosity matrix of the hydrous oxide type may be used in these composite catalysts, such as silica-alumina complexes, silica-magnesia, silica gel, high porosity clay, alumina, and the like.

The pellets or beads of the composite catalysts may be prepared by dispersing the aluminosilicate in an inorganic oxide sol according to the method described in U.S. Patent No. 2,900,399 and converted to a gelled bead according to the method described in U.S. Patent No. 2,384,946.

The crystalline aluminosilicate material must have a pore size or intracrystalline aperture or channel size sufficiently great to admit desired reactants. 5 A. is approximately the minimum pore size so acceptable.

The composite may contain from 5-95 percent of the matrix material.

Utilizing the conditions in the reaction of:

Pressure p.s.i.a 10-1000 Temperature F 500-900 Space velocity (w./h./W.) 10-1000 C/O 0.01-10 Recycle ratio 0-10 a product distribution can be obtained as follows, expressed in percent weight of charge stock:

Gas 1-15 C 3-25 Gasoline 2075 Side streams -40 Bottoms 035 Coke %5 Although the present invention has been described in conjunction with preferred embodiments, it is to be understood that modification and variations may be resorted to, without departing from the spirit and scope thereof, as those skilled in the art will readily understand. Such variations and modifications are considered to be within the purview and scope of the appended claims.

What is claimed is:

1. A method for efiecting liquid phase conversion of hydrocarbons which comprises forming a liquid phase slurry of fresh hydrocarbon feed and finely divided high activity catalyst particles, introducing said slurry to a hydrocarbon conversion zone maintained under temperature and pressure conditions sufficient to convert a portion of said hydrocarbons to vaporous conversion products, passing vaporous hydrocarbon conversion products overhead to a fractionation zone, removing a first portion of slurry from the conversion zone, separating said first portion into a liquid hydrocarbon phase and a catalyst particle phase, regenerating by combustion said catalyst particles phase, reslurrying regenerated catalyst particles with at least said liquid hydrocarbon phase and recycling reslurried material to said conversion zone.

2. The method of claim 1 wherein the amount of hydrocarbon-catalyst slurry Withdrawn from the reaction zone is controlled to yield a space velocity (W./h./w.) of -1000 and a catalyst to oil ratio of 0.0140.

3. The method of claim 1 wherein a second stream of hydrocarbon-catalyst slurry is withdrawn from the reaction zone and passed into heat absorption relation with the catalyst undergoing combustion regeneration before being returned to the reaction zone.

4. The method of claim 1 wherein the hydrocarbon used for reslurrying the regenerated catalyst is a portion of the hydrocanbon feed stock.

5. The method of claim 1 wherein the finely divided high activity catalyst particles comprise a superactive crystalliue aluminosilicate of ordered internal structure.

6. Apparatus for conversion of hydrocarbons comprising in combination, a vessel having a lower reactor section containing finely divided solid catalyst slurried in liquid hydrocarbon, and an upper fractionating section in open communication therewith containing a plurality of spaced apart fractionating plates, a first inlet conduit to said reactor section for introducing liquid feed stock, a first Withdrawal conduit from said reactor section for withdrawing hydrocarbon-catalyst slurry, a separating means connected to said first withdrawal conduit for separating said slurry into a hydrocarbon stream and solid particle material catalyst streams, a solid catalyst particle regenerating chamber, means for conveying said catalyst particle stream from said separating means to said catalyst regenerating chamber, means for conveying regenerated catalyst to a catalyst-hydrocarbon slurry forming means, conduit means communicating between said reslurrying means and said reactor section, a second conduit means for conveying a slurry stream from said rector section through said regenerating chamber in indirect heat absorption relation with said catalyst undergoing regeneration in said regenerating chamber, and conduit means leading from said regenerating chamber back to said reactor section.

7. Apparatus in accordance with claim 6 wherein a conduit means connects the hydrocarbon exit from said separating means to said reslurrying means.

8. Apparatus in accordance with claim 6 wherein a conduit means connects the feed stock inlet to said reactor zone with said reslurrying means.

9. Apparatus in accordance with claim 6 wherein said conduit means from said regenerating chamber for the recycled slurry stream merges with the conduit from said reslurrying means.

References Cited UNITED STATES PATENTS 2,319,710 5/1943 Stratford et a1. 208-153 2,723,949 11/1955 McCausland 208-176 2,763,600 9/1956 Adams et al 208160 3,113,844 12/1963 Hemminger 208 3,198,729 8/1965 Payne 208 DELBERT E. GANTZ, Primary Examiner.

A. RIMENS, Assistant Examiner.

Claims (1)

1. A METHOD FOR EFFECTING LIQUID PHASE CONVERSION OF HYDROCARBONS WHICH COMPRISES FORMING A LIQUID PHASE SLURRY OF FRESH HYDROCARBON FEED AND FINELY DIVIDED HIGH ACTIVITY CATALYST PARTICLES, INTRODUCING SAID SLURRY TO A HYDROCARBON CONVERSION ZONE MAINTAINED UNDER TEMPERATURE AND PRESSURE CONDITIONS SUFFICIENT TO CONVERT A PORTION OF SAID HYDROCARBONS TO VAPOROUS CONVERSION PRODUCTS, PASSING VAPOROUS HYDROCARBON CONVERSION PRODUCTS OVERHEAD TO A FRACTIONATION ZONE, REMOVING A FIRST PORTION OF SLURRY FROM THE CONVERSION ZONE, SEPARATING SAID FIRST PORTION INTO A LIQUID HYDROCARBON PHASE AND A CATALYST PARTICLE PHAE, REGENERATING BY COMBUSTION SAID CATALYST PARTICLES PHASE, RESLURRYING REGENERATED CATALYST PARTICLES WITH AT LEAST SAID LIQUID HYDROCARBON PHASE AND RECYCLING RESLURRIED MATERIAL TO SAID CONVERSION ZONE.

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