US2471228A - Production of hydrocarbons - Google Patents

Description

May 24, 1949. E. v. MATHY PRODUCTION loF HYDRocARoNs Filed Sept. 3, 1946 mnooma i930] d a V 1| D u o W u o N @n ov vw x Ow W w No vm mm m V @o Nm w H S565 vv @m a I1 zmoomo Il... mm om vm N mv |v M0555. M Qxozo mw. .|20m o /ll om wm Patented May 24, 1949 AUmTiezD STATES PATENT `ol=i-lc|sz- PRODUCTlON OF HYDROCARBONS Eugene V; Mathy, Bartlesville, kla., assigner to Phillips Petroleum Company, a corporation of f Delaware Application September 3, 1946, Serial No. 694,543

3 Claims. l.

This invention relates to the production of hydrocarbons. In a specific embodiment the invention relates to the carrying out of endothermic catalytic cracking of hydrocarbons. One aspect relates to the exothermic synthesis of hydrocarbons by catalytic reaction of hydrogen and carbon monoxide.

The cracking of hydrocarbon oils to form lower boiling hydrocarbons has long been known. Such processes have been eifected in the absence of catalysts, and while this is still an important commercial method, it has been replaced and augmented to a considerable extent by catalytic processes. By proper choice of catalyst and correlationof reaction conditions with the type of charging stock, high yields and the production of various desired types of products are realized. The most common process in use at the present time is the cracking of gas oils and reduced crudes to form gasoline. Substantial amounts of normally gaseous hydrocarbons are also formed concomitantly.

A different approach to the formation of gasoline and other hydrocarbons is now becoming of considerable importance. 'I'his is a synthesis -reaction in which carbon monoxide and hydrogen combine in the presence of suitable catalysts to form aliphatic hydrocarbons. The nature and Vproportions of the various possible hydrocarbon products are dependent upon choice of catalyst, ratio of hydrogen to carbon monoxide, temperature, pressure and flow rates. The synthesis reaction just described is of a highly exothermic nature; for example, about 114,500 calories of heat are given up when 9 mols of H2 combine with 4 moles of CO toform 04H10.

On the other hand, the cracking of hydrocarbons is an endothermic reaction. Because of this, if the cracking is accomplished in a large reaction chamber, the temperature decreases in direction of ow of reactants. is too great, the reaction rate falls to undesirably low levels. Many complicated methods have been suggested for preventing or minimizing the e'ects of temperature drop in catalytic cracking processes. Heat carriers have been employed in the form of gases, liquids, and solids. Various If this decrease specialized arrangements of catalyst in contact l Each of these and other expedients have been less than fully satisfactory for one reason or another.

Somewhat similar but converse methods have been employed in an effort to controlv the temperature of the exothermic Hz-CO reaction. For example, inert gases, liquids or solids are sometimes used to absorb and carry away heat of reaction. Catalyst has been disposed in small tubes surrounded by heat exchange media. The reaction has also been carried out in the presence of a boiling liquid. These methods, too, have left much to be desired.

It is an object of this invention to produce hydrocarbons. Another object of the invention it to eect the cracking of hydrocarbons in the presence of cracking catalysts. A further object is to minimize temperature drop in catalytic cracking of gas oil or other hydrocarbon materials to form lower boiling hydrocarbons. Yet another object is to react carbon monoxide with hydrogen to form useful aliphatic hydrocarbons. A still further object is to effect the last named synthesis concomitantly with the cracking heretofore mentioned. Yet another object is to utilize exothermic heat of thev synthesis reaction while avoiding temperature rise. A still further object is to crack hydrocarbons at a substantially constant temperature. Yet another object is to reduce carbon formation on a cracking catalyst. Further objects and advantages of the invention will be apparent, to one skilled in the art, from the accompanying disclosure and discussion.

In one embodiment of my invention a hydrocarbon material to be cracked, for instance a gas oil, is passed through an elongated catalyst chamber at cracking conditions of temperature, pressure and flow rate. Within the chamber is disposed a body of cracking catalyst, which has been impregnated with a catalyst active in promoting the synthesis of hydrocarbons by interreaction of hydrogen with carbon monoxide. mixture of hydrogen and. carbon monoxide is introduced into the catalyst chamber at a plurality of points along the length thereof. Careful control of the ratio of hydrogen to carbon monoxide, the ratio of the resulting mixture to the hydrocarbon material undergoing cracking, and the spacing of the points, makes possible the carrying out of the two reactions, i. e., cracking on the one ,hand and synthesis on the other hand, simultaneously and at a substantially constant temperature throughout the length of the reaction zone.

As' explained hereinabove, the cracking reacthesis reaction serves to supply the heat required for the cracking reaction and thus avoid the normal temperature drop in the cracking zone. An important resultant advantage lies in the fact that it is possible to preheat the oil passed to the cracking chamber to a lower temperature than would otherwise be necessary., The lower temperature of the preheating coil minimizes coke formation therein and undesired thermal crackinr which normally occurs in the preheater.

It has heretofore been proposed to mix particles of an aromatization catalyst and a catalyst promoting the reaction of hydrogen with carbon monoxide together in a single reaction chamber and to carry out an aromatization reaction in the presence of carbon monoxide which is mixed with the reactants entering the chamber. In such a process, however, a large excess of hydrogen must be used and hydrogen isproduced in large quantities by the aromatization reaction. Accordingly, a very high ratio of hydrogen to carbon monoxide exists in the reaction zone. This large excess of hydrogen encourages the formation of low molecular weight products in the synthesis reaction and also results in saturated rather than unsaturated products of the synthesis reaction. In contrast. the process of the present invention gives no net production of hydrogen, nor is a large excess of hydrogen continually passed through the reaction zone. Instead, hydrogen is introduced only in admixture with carbon monoxide, `and in limited and controlled amounts. Accordingly, the products produced by the reaction of hydrogen with carbon monoxide are unsaturated in character and thus correspond to the products of the concomitant cracking reaction which are also unsaturated.

In the low pressure catalytic cracking of gas oils, a comparatively unsaturated gasoline is formed with an ASTM clear octane rating usually in the range of from '75 to 80. The products of the H-CO synthensis reaction in the presence of suitable catalysts have about the same degree of unsaturation, with an octane rating ordinarily in the range of about 65 to 75. This synthesis gasoline, however, ordinarily also contains some oxygenated compounds. In the practice of my invention, after the formation of the products of the synthesis reaction the oxygenated compounds are destroyed by contact with the cracking catalyst and the octane number of the synthesis gasoline is raised somewhat. Accordingly,'the gasolines formed by both the synthesis and the cracking reactions as carried out simultaneously are very similar, and may be handled in similar ways, so that their produc-A tion in one step is particularly advantageous.

By depositing the synthesis catalyst directly on the cracking catalyst I obtain an extremely As a cracking catalyst I prefer to use bauxite. Alternatively, a synthetic or naturally occurring composite of silica and alumina may fbe used, although wholly equivalent results will not necessarily thereby be obtained. A suitable catalyst of this group is silica gel in admixture with a minor percentage of alumina, preferably prepared by adsorption of hydrous alumina by the4 silica gel from a solution of an aluminum salt,

f Natural clays, preferably acid-treated,

such as is disclosed in U. S. Patent 2,142,324. A synthetic silica alumina cracking catalyst may also be prepared by co'precipitation of the silica and alumina or by admixture of precipitated silica and precipitated alumina in the wet state. are sometimes suitable, for instance, Olmstead, Attapuigus, Floridin earth, montmorillonite, Filtrol, diatomaceous earth, fullers earth or the like. Such clays are preferably leached for a limited period of time with acid such as dilute sulfuric. Other effective cracking catalysts, such as magnesium chromite, boron silicate, etc., may be employed. The catalyst is preferably employed in the form of lumps or pills.' which ordinarily range in size from four to four-' teen mesh and are arranged in one or more beds within an elongated reactor.,l The invention* may also be practiced by employing a powdered catalyst suspended in reactants and passed through an elongated conversion zone.

The cracking catalyst is impregnated by any suitable method with a material catalytic toward the synthesis reaction between hydrogen and carbon monoxide. I prefer to employ nickel oxide, although oxides of thorium, iron, cobalt,

and other metal oxides, as well as other well known promoters specific for this reaction may likewise be used. Perhaps the most satisfactory method of impregnation is to impregnate the .m prepared cracking catalyst with a solution of a eicient heat transfer, and it is also foundthat carbon deposition on the cracking catalyst is substantially minimized. This may be explained by the theory that the synthesis catalyst is active in adsorbing hydrogen whereas the ordinary cracking catalyst is not. Thus, the synthesis catalyst impregnated on the cracking catalyst eiects an intimate contact of hydrogen with the cracking catalystv whereby a given amount of hydrogen in the reaction zone has an extremely high efliciency in minimizing carbon formation on the cracking catalyst. ARegardless of any theory, however, this effect is an important and substantial advantage of my invention.

salt of a metal whose oxide it is desired to employ as a synthesis catalyst. Resulting material is then heated under conditions forming the metal oxide. Various other methods are well known to the art and need not be described in detail. The synthesis catalyst should comprise a minor proportion of the total catalyst mass, preferably in the range of l to 20 per cent by weight.

One specic embodiment of the invention is illustrated in the accompanying diagrammatic drawing which shows one arrangement of apparatus elements and flow of materials therethrough suitable for practicing the process. It will be understood that the drawing is somewhat idealized, and that various auxiliary items of equipment, such as pumps, control valves, temperature, pressure and flow. controllers, recorders, and the like are not shown for the sakeof simplicity. Inasmuch'as such items are well' known to the art they need not be described in further detail.

In the drawing, a hydrocarbon material to be cracked, such as a gas oil or reduced crude, is

introduced by line I0 into heating coil i2 which is disposed within furnace I4. At a later point in the heating coil i2, steam may be introduced from line I6 if desired. The preheated cracking charge desired throughout the catalyst bed because of the subsequent introduction and reaction of synthesis gas. The hydrocarbon oil is cracked by the cracking catalyst, and hot eilluents exit v ia line` 22 for passage into a separation system indicated 5 diagrammatically by a fractionator 24.

Carbon monoxide is withdrawn from storage unit 25, and hydrogen is withdrawn from storage unit 28, via lines 30 and 32 respectively. Carbon monoxide and hydrogen are withdrawn from their respective lines in controlled proportions for in' troduction into catalyst chamber 20 through one or more inlets at a point or points subsequent to the point of entry of the heavy oil to be cracked.. In the drawing these inlet points are represented by lines 34, 36, 38 and 40, which preferably terminate within the catalyst chamber 20 in horizontal perforated tubes or spreaders (not. shown). These linesreceive carbon monoxide from line 3l) by means of valved lines 42, 44, 46, and 48 respectively, and receive hydrogen from line 32 by means of valved lines 50, 52, 54, and 56 respectively. Preferably the ratio of hydrogen to carbon monoxide is about 3 to 1, which is slightly in excess of the stoichiometric 2 to 1- ratio employed in the conventional synthesisreaction, The hydrogen and CO react in the presence of the synthesis catalyst which is impregnated on the cracking catalyst, to give hydrocarbons, largely those which are normally liquid unsaturated hydrocarbons. The thus-produced materials add to and complement the products of'l the cracking reaction, and are recovered 'from the catalyst chamber via line 22 along with other eiuents of the catalytic reactor 20. Separation unit 24 in practice will comprise a plurality of fractionators, flash chambers. ab sorbers, strippers, and the like. One skilled in the art will readily understand the construction, and operation of such apparatus. Liquid products of the cracking and synthesis reaction are Y withdrawn from unit 24 through line 58 for further separation and treatment, not shown in the drawing. This treatment ordinarily comprises a fractionation to separate gasoline hydrocarbons from higher boiling materials. The higher boiling materials are partly or wholly recycled tothe catalyst chamber for further cracking. Materials lower boiling than gasoline are removed through line 60, and may be discarded or passed to further treatment through line 62, A portion or all of this material, which contains some hydrogen, may

be passed through line 64 to hydrogen storage 28 for reuse in the process. Ordinarily it is neces-1 sary and desirable to separate hydrogen from the other components inasmuch as the quantity of` hydrogen remaining ai ser passage through the catalyst chambers is relatively small and it is found in admixture with considerable quantities of hydrocarbon gases. The hydrogen and hydrocarbon gases are preferably separated from each other by absorption or other methods,-with the hydrogen being reused and the hydrocarbon gases being utilized in any desired manner. Some methane may also be formed in the catalyst chamber and this should be removed, at least in` part, from the hydrogen stream. Makeup hydrogen is introduced to the process through line' 66, and makeup CO is introduced to the process through line 68. An important advantage of thef process described is that large amounts of hydrogen are not recycled, thus avoiding the necessity of employing expensive compressors to a: great extent,

The amount of hydrogen used in the catalyst 75 the cracking run:

chamber is preferably at least twice the amount of carbon monoxide used, but should not exceed three or four times the lamount of carbon monoxide. The total hydrogen and carbon monoxide employed will normallyrange from 0.005 to 0.05 part by weight per unit weight of hydrocarbon feed to thek inlet of the catalyst chamber when employing a conventional cylindrical chamber. The proportions of hydrogen and carbon monoxide on the one hand and gas oil or other cracking charge onthe other hand will vary considerably depending upon the presence or absence of diluents in the process,- the construction of the catalyst chamber, the particular catalyst used, the operating conditions of temperature and pressure, the auxiliary heat exchange, if any which is Steam or other employed, and other factors. diluents may be introduced in admixture with the hydrogen and carbon monoxide, as well-as in admixture with the cracking charge.

Reaction temperatures will generally be at least 850 F., on up to 1100 or 1200 F., depending upon the particular material being cracked and the catalyst employed. The flow rate of hydrocarbons to be cracked will range from 0.3 to y 10 liquid volumes per volume of catalyst per hour. The reaction is lpreferably executed under moderate superatmospheric pressures which may advantageously range from 50 to 1500 pounds per square inch gauge or more. `After aperiod of conversion, the catalyst is regenerated by oxidation of carbonaceous deposits therefrom. Preferably this is accomplished by means of a mixture of air and steam at temperatures not in excess of about 1400 F. Other oxidizing gases may be used in known manner, Ordinarily the regeneration period will be substantially equal to the conversion period, and may range from one-half to twelve hours.

-As one example of the practice of my invention the following data are offered. It will be understood. of course, that the invention in its broad scopev is not to be unnecessarily limited thereby.

A vertical cylindrical catalyst chamber fllled with a bauxite catalyst of 8-14 mesh in the total quantity of 58,000 pounds was employed. A Midcontinent gas oilhaving an ASTM boiling range of 40G-'730 F. and an `API gravity of 36.5 was charged at the rate of 190 barrels per hour at a space velocity of one volume of liquid per volume of catalyst per hour, together with 11,800 pounds of steam per hour. A pressure of p. s. i; g. was

employed. The conversion and regeneration portions of the cycle were each four hours long.

The following temperatures were observed in Degrees Fahrenheit Preheater coil outlet 1,040 Catalyst chamber inlet 1,016 Top of catalyst bed 993 Catalyst chamber outlet 929 Yields on the cracking run are as follows:

Dry gas weight per cent 10.5 C4 hydrocarbons weight per cent A 8.0 Debutanized gasoline ..-volume per cent 33.5 Recycle volunie per cent 50 ASTM octane clear '.--volume percent-- 76.5 Conversion volume per cent 50 Carbon weight per cent 1.9

contiguous horizontal beds divided by spreaders which are used to distribute a Hz-CO mixture at intermediate inlet points. Pressure and charge rates for gas oil and steam are held the same as those in the run with the untreated bauxite catalyst, Ibut the preheater coil outlet temperature is lowered to 1010 F., which gives a catalyst chamber inlet temperature of 990 F. and a top catalyst bed temperature of 965 F. A carbon monoxide-hydrogen mixture comprising 38,180 cubic feet of hydrogen per hour and 12,670 cubic feet of carbon monoxide per hour is introduced in three equal portions at three points in the catalyst chamber by means of spreaders.

This method of operation gives an average temperaturg of 960 F. in each section of the catalyst bed, there -being about a F. temperature differential across each bed section (this diiierential could be decreased by employing more injection points, butit is not necessary to do so for satisfactory operation). This vis approximately the sameaverage catalyst temperature as in the run with the untreated catalyst. Yields are not greatly changed from those obtained in the cracking run in the absence of synthesis gas. Gasoline yield is increased by one per cent and gas by 0.5%, with no substantial difference in the character of the products. lThe carbon deposition is decreased to 1.8 weight per cent, which decreases the regenerative air requirements.

I claim:

1. The process which comprises passing a mixture of gas oil and steam through an elongated catalyst zone in contact with a bauxite cracking catalyst impregnated with about ilve weight per cent of nickel oxide synthesis catalyst at a temperature of about 950 to 1000" F., and a ow rate of one liquid volume gas oil per volume of catalyst per hour, passing a mixture of hydrogen with carbon monoxide in approximately a 3:1 volume ratio of hydrogen to carbon monoxide into said catalyst zone at a plurality of points along the length thereof in total quantities of about 50,000 cubic feet of said mixture per hour to form hydrocarbons substantially entirely heavier than methane. and recovering as unsaturated products from effluents .of said catalyst zone cracked hydrocarbons and synthesized hydrocarbons including gasoline in admixture.

2. The method of preparing gasoline boiling hydrocarbons of an unsaturated nature which comprises passing a hydrocarbon oil higher boiling than gasoline through an elongated catalyst zone at cracking conditions of temperature, pressure and flow rate such as to form unsaturated hydrocarbons in the gasoline boiling range by cracking reaction, in contact with a cracking catalyst impregnated withk a synthesis catalyst which promotes formation oi' hydrocarbons from hydrogen and carbon monoxide, introducing hydrogen and carbon monoxide in less than a 4:1 volume ratio of hydrogen to carbon monoxide into said catalyst zone at a plurality of points spaced along the direction of ilow in total quantities suiilcient to form substantial amounts of unsaturated gasoline boiling range hydrocarbons by synthesis reaction while insumcient to furnish hydrogen for reaction with said unsaturated products and thereby to substantially minimize normal temperature drop along the length of the reaction zone by liberation of exothermic heat of reaction from said synthesis, and concomitantly recovering said gasoline of an unsaturated nature from said cracking and said synthesis reactions.

3. In a process for the endothermic catalytic cracking of hydrocarbon oils to form lower boiling unsaturated hydrocarbons wherein the hydrocarbon oil to .be cracked is passed through a catalyst zone under cracking conditions of temperature, pressure and ilow rate. the improve. ment which comprises employing in said catalyst zone a cracking catalyst which has -been impregnated with a catalyst active for the synthesis of hydrocarbons from hydrogen and carbon monoxide, introducing a mixture of hydrogen and carbon monoxide in less than a 4:1 volume ratio of hydrogen to carbon monoxide into said catalyst zone at at least one point subsequent to the point of entry of the hydrocarbon oil to be cracked in quantities suftlcient to react independently of and concomitantly with said cracking to effect forma tion of unsaturated hydrocarbons substantially entirely heavier than methane',.by synthesis reaction between said hydrogen'and carbon monoxide while insufllcient to furnish hydrogen for reaction with said unsaturated products and thereby to supply heat of reaction to the catalyst zone. and recovering total effluents from said catalyst zone containing products of the cracking reaction and products of the synthesis reaction.

` EUGENE V. MATHY.

REFERENCES CITED The following references are of record in thc ille of this patent:

UNITED STATES PATENTS Sensei et al Jan. 14, 194'

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