US2292677A - Catalytic conversion of hydrocarbons - Google Patents

Description

Aug. 11,1942.

C. L. THOMAS CATALYTIC CONVERSION 0F HYDROCARBONS Filed May 17, 1939 ramadan. 11, 1942 4UNH-ED sr'ii'rlal-S.l PATIENT#.OFFICE mmf "if charles 1;. Thom, chime, m., am a Universal Oil Products Company. Chicago, Ill., a'

corporation of Delaware a Application May 1r, 1939, seran nu. 214,1sz

a claims (c1. 19o-m f This invention relates to the catalytic conversion of hydrocarbons produced by the distillation of heavy hydrocarbonaceous materials, and more particularly, distillates which are vaporizable without substantial decomposition.

More specifically, the invention concerns .the conversion of hydrocarbons by means of specially prepared catalysts into gasoline and desirable and because of the large amount of investigation has been developed to the point wherethe principles involved are fairly well understood. The y principles of catalytic conversion of hydrocarbons, and more specifically, the catalytic cracking of high-boiling hydrocarbon fractions from petroleum to produce gasoline and gas 'are not so well understood. Such explanations as have been set forth are largely empirical and a discussion of these reactions, is thereforebest confined ,to a factual basis,

In one specic embodiment the present invention comprises a method foryconverting hydrocarbon fractions into high yields of gasoline by contacting said fractions in vaporous form with a cracking catalyst at conditions adequate to effect catalytic cracking, separating the gasoline and gas, recirculating a portion of the unconverted oil to the catalytic cracking step, separating the gasoline into a low-boiling and a highboiling fraction, separating the gas into a plurality of fractions, subjecting a fraction comprising essentially butane-butene hydrocarbons* to polymerization, recovering the portion of the polymer Vcomprising essentially octenes, return-` ing a portion of polymer boiling above the octene fraction to the catalytic crackingsteprcombining the octene polymer with the aforementionedA lowboiling fraction of catalytlcally cracked 'gasoline and a portion of Vthe hydrogen-containing gas from the catalytic cracking step, contacting this mixture with a hydrogenatingcatalyst at hydrogenating conditions, recovering the normallyliq- I uid hydrogenated product, combining the residual gasesl from the aforementioned polymerization step with the gaseous fraction from rthe catalytic cracking step-which comprises essentially pro-` ,55, denitc shapes are calcined at `temperatures pane-'propylene hydrocarbons, .subjecting said mixture to polymerization, recovering the polymerized products, and blending controlled portions of the products of the various steps to form a gasoline of high octane numberand susceptibility to tetraethyi lead.

Many catalysts have been prODsd to assist `the conversion oi'A distillates into t gasoline and gas. Among these are certain types -which pro-v mote. as "the predominating reaction, the forma,- tion of gas rather thangasoline.l `Such catalysts include'A the reduced metal catalysts, ysuch as nickel and iron and their ores." These catalysts are. furthermore, subject to poisoningbysuliur compounds and tend to produce coke`like'"mate' rials which' deposit as a nlmaround the catalysts and renderthem inactive. Other typesof catalysts promote dehydrogenation reactions rathery than true cracking, and as, a conscqucnce'fthe character of the gases and theantiknock properties of the gasoline'produced are considerably diiierent than those whichlare used in the present invention.

Thepresent process conveniently utilizes more or less `refractory cracking catalysts which are produced by the chemical treatment of naturally occurring clays, and catalysts comprising SINE-v,A cially prepared synthetic masses, for example, f,

silica-alumina, silica-zirconia, silica-alumina-zirconia, and silica-alumnia-thoria and similarrefractory materials having a high degree of acf tivity. These latter synthetic catalysts may be prepared by various methods such as mixing and coprecipitation of the ,various components imder conditions 4whereby 'alkali metal ions are` excluded. In these catalysts the ratio of thel components mayl vary within wide limits "and the masses may'be considered to comprise intimate or possiblemolecular admixtures, all of the components indicating more or less low activity individually butin the aggregate displaying high activity.l The activity also is not an additive function ofthe individual component, it being relatively constant for a wide range of proportions whether in molecular. or fractions of molecular proportions. `It appears that no one component can befdetermined as the' one component for which the remaining components may be considered `as the promoter according to conven4 tional terminology. In the present invention n these catalysts Vare used in the form of sized par- Y ticles or other formed shapes such as pellets produced by compression or extrusion methods. Thepressed compositesafterdrying and forming into cracking step. is carried out may vary over the temperature range of approximately 800 F., to 1200 F. The amount of unconverted bottoms which are recycled will vary considerably and can be controlled according to the most eillcient operation. Y

The amount and end point ofV tliellw-boilings gasoline used in the hydrogenation step is determined by the properties desired in the finished gasoline. Normally, oleflnic hydrocarbons have relatively good antiknock properties but are not particularly susceptible to increase in octane number by the addition' of antiknock agents. On the other hand, the paraillnic hydrocarbons have excellent tetraethyl lead susceptibility compared to the oleilns. 'Ihe highly branched iso-paraillns have higher antiknock properties than do the normal or straight-chain parailins and also than the corresponding oleilns. It is further known that hydrogenation of the octenes produced by polymerizing the butene fraction of the gases from vcatalytic cracking results in a saturated hydrocarbon mixture having a high octanenumber (95-100) as well asexcellent blending value and lead susceptibility. n the other hand, the

polymer obtained by polymerizing propylene hasv good octane number and blending value, but

when hydrogenated the product loses desirablel antiknock properties. 'I'he blending value of the polymer as produced, on the other hand, is good and tends to improve thev octane number, of a blend in which it is incorporated to a greater ex tent than would be predicted from its actual octane number as determined without blending. 'I'he present process takes advantage of the char# acteristic properties of the various types of gaso- .line produced and at the same time permits recirculation of high-boiling materials and the recovery of many of the gaseous products with the result that not only are the overall motor fuel properties of the gasoline improved, but the actual yield obtainable therefrom is increased substantially.

The polymerization steps yof the .process are carried out catalytically usingcatalystsjsuch as the co-called solid phosphoric acid catalyst or sulfuric acid. The solid phosphoric `'acid catalyst is made by mixing a liquid phosphoric acid with kieselguhr or similar suitable siliceous material, forming into cylindrical or annular shapes, drying and calcining. 'I'he process is carried out at temperatures of approximately 2752-450 F., and pressures of.150-1000 pounds per square inch and up. Sulfuric acid polymerization may be carried out at temperatures within the range of 65`250 F., with acid concentrations of 60% and higher.

from the cracking process containing hydrogen may be used. v

The accompanying drawing illustrates ydiagrammatically one embodiment of my process. It should be understood that the process is not limited to the exact apparatus or conditions speciiied therein. ,The drawing has not been made to any scale and ncitherhasthere been any attempt to represent the various pieces of equipment which compose the apparatus in exact proportion of one another.

yReferring to the drawing, the oil enters the system through line l, valve 2, valve 3, pump l,

line l and valve i, passing into coil 1 which is disposed inI furnace 3. -By this means itis heatedto a desired cracking temperature and passes through line 9 and valve Il into Acatalytic converter Il wherein a substantial portion is converted'to gasoline and gas. The mixture passes through line I2 and valve I3 into fractionator Il where it is'divided into several portions. A portion of the unconverted oil boiling above the gasoline boiling range may be withdrawn through line i5 and valve I8, passed through line Il and valve I8 into line I where it mingles with the raw charging stock and passes with it into the catalytic conversion stage. A portion of heavy bot toms may be withdrawn throughv line l! and valve 20 to gas oil storage not shown. The mixed gasoline and gases pass through line 2| and valve 2'2 into stabilizer 23. A portion of high-boiling gasoline is withdrawn through line 2l and valve 25 to storage. A portion of the low-boiling gasoline is withdrawn through line 26 and valve21 or through line 21' andvalve 21" depending upon the end point desired in the side cut, into line 2l where it mingles with a desulfurizing reagent such as sodium hydroxide solution which may be pumped throughline 29, valve 30, pump 3|, valve 32`and line 33. The mixture of caustic and gasov line passes through mixer 3l, line 35 and valve 38 into desulfurizer 31. The spent caustic is withdrawn through line 38 and valve 33 to caustic regeneration which is not shown. The desulfurizing step as employed herein is only one example of a method which may be used for desulfurizing the low-boiling gasoline, Ii'so desired other desulfurizing solutions may be used instead of caustic soda such as ethanol amine, propanol amine, etc.: or solid desulfurizing materials may be used with suitable changes in apparatus. Such materials may comprise various metals, metal oxides or metal sulfides which have the property of combining with sulfur and sulfur compounds at-relatively low temperatures. If it is desired to carry out the desulfurization step at low temperatures suitable heat exchange equipment may be introduced into lline 2l. The desulfurized gasoline passes through lines I0 and Il The hydrogenation step may be carried out in`r the presence of catalysts such as nickel, copper, cobalt, chromium, iron, molybdenum sulfide,

molybdenum oxide, etc., at temperatures of 250- 450 F.,vand pressures 'of approximately- 15 to 1,000 pounds per square inch absolute depending and valve l2 to the hydrogenationv step which will be described later. A part of the gasoline may be withdrawn to storage through line Il! and valvel III.4 The process gases from stabilizer 23Vpass through line I3 and valve M through heat exchanger Il by meansjof pump Ii' and valve Il" into sulfur removal system by means of spray 4.1 where sulfur is removed by any well known method such as scrubbing with caustic,

, triethanol amine, and other well known desulfurizing methods. The desulfurizing medium enters the desulfuriser Il by meansof line Il.' valve 43 v and spray Il where it passes downward munteron the stocks, the catalyst and `the degree of hydrogenation desired. The hydrogen may 'besupplied from ,an external source or the gases current to the upwardly flowing gases. 'I'he spent solution is withdrawn through line Il and valve.

l2 to the regeneration system not shown. The

gasoline to be passed tothe hydrogenation step,

thus increasing the flexibility of the oper ltion.A

arator 55 may suitably consist of a separate debutanizer and depropanizer but is shown as one vessel in the interests of simplifying the drawing.

The C4 fraction is withdrawn from the separator 55 by means of line 58, valve 51, pump 58, valve 59, heat exchanger 80, line 8|, and valve 82 into the selective polymerization zone 83 and the products are discharged from the latter through line 84 and valve 85' to fractionator 88 where-the unconverted butane and butene are removed through line 81 and valve 88. Alternative to this al1 or a portion of the unconverted gases may be passed through line 81' and valve 88' to join with line and mingle therein with the C: fraction from separator 55. The polymer boiling above the gasoline boiling range may be withdrawn through line 89 and valve 10 and may be returned all or in part to the catalytic cracking step by means of line 1| and valve 12 which joins with line |1 and eventually with line I. Il so desired, a portion of the heavy polymer may be withdrawn through line 13 and valve 14 to storage. 'I'he Ca polymer is withdrawn from fractionator 88 through line 15 and valve 18 which Joins with line 4|. The Cs polymer and the low-boiling gasoline from line 4| ymingle in line 11 and are pumped by means of pump 18 through valve 19 into line 80 where they mingle with the uncondensable gases from separator 55 which leave the separator through line 8|, valve 82, pump 83 and valve 84. A portion of the hydrogen-containingV gases may be withdrawn through line,8| and valve 8| Under certain circumstances addi through line 8|' and valve 8|". The mixture passes through coil 85 which is disposed in furnace 88 where it is heated to the proper hydro.- genation temperature and then passes through line 81 and valve 88 into the hydrogenator 89 which contains a suitable hydrogenation catalyst. The hydrogenated mixture leaves the plant through line 90 and valve 9|, passing into stabilizer 92. The unused hydrogen as well as the low-boiling uncondensable gases are removed through line 93 and valve 94. The hydrogenated oil is removed through line 95 and valve 98 to storage. The C3 oleilns from separator 55 are removed through line 91, valve 98, pump 99 and valve |00, line |00' and valve |00", passing into polymerizer |0| where the oleilns are converted to the motor fuel boiling range. The reaction products pass through line |02, valve |03 into stabilizer |04. The substantially saturated gases are removed from the stabilizer by means of line and valve |08. The polymer is removed through line |01 and, valve |08 to storage. The finished products treated in the manner described which pass through lines 24, 13, 95 and |01 may be blended in whatever proportion is desired. Normally, the proportions are the same as those in which they are made. The end point of the material which may be withdrawn through line 13 is somewhat high, usually in the neighborhood of 425 F.. and as a consequence only a limited amount of this can be used in the final blend. It is for this reason that the major portion of it is returned to the catalytic cracking zone. Furthermore, a portion of the low-boiling desulfurized gasoline from line 40 may be withdrawn through line |09 and valve ||0 and blended with the nal product. This permits control not only of the end point but also the amount of light 'I'he method o! operation of the plant can be varied somewhat from the preferred method as described. For example, the combined C: and C4 olefins can be removed from the separator, polymerized, fractionated and hydrogenated if desired. In this case the C: and C4 hydrocarbons are withdrawn from'separator 55 throughV linel 58, valve 51, pump 58, line 59, heat exchanger, 60,

line8| and valve 82 into catalytic polymerizer 83. No product is withdrawn from separator 55 through line 91 or valve 98. In this case polymerizer |0| is not used. v

The following example is given to illustrate my process and should not be considered as limiting it to the exact conditions given therein.

A Mid-Continent gas oil of 35.9 A. P. I. gravity was catalytically cracked at a temperaturey .of 975 F. v 'I'he unconverted bottoms were recycled to the catalytic cracking step. -The gas and gasoline were removed from the fractionator and separated into (a) gases containing C4 and lighter hydrocarbons, (b) a 300 F. end point cracked gasoline, and (c) a higher boiling cracked naphtha fraction. The low-boiling cracked gasoline was treated with approximately 10% of 30 Be. caustic solution and passed as described in the foregoing specication to the hydrogenation'step.

'I'he gases were scrubbed continuously by means of triethanolamine 4solution whereby they were desulfurized, and separated into a low-boiling fraction containing hydrogen, methane, ethane and ethylene which was passed to the hydrogenation step, apropane-propylene fraction which was passed to a non-selective polymerization step, and a butane-butene fraction which was passed to a selective polymerization step where, by means o! a solid phosphoric acid catalyst, the olellns were largely converted to liquid polymers. The iso-octenes were recovered and combined with the 300 F., end point catalytically cracked gasoline and the hydrogen-containing gases and passed into the hydrogenation step with nickel catalyst operating at 15 pounds per square inch pressure and 400 F., the product recovered and later blended with the finished gasoline. The residual gases from the selective polymerization step contained an appreciable amount of unconverted normal butene and were combined with the propane-propylene fraction of the catalytically cracked gases and passed to a separate polymerization step. The polymer was recovered and blended with the finished gasoline. The highboiling polymers from the polymerization plants were recirculated to the catalytic cracking step.

The inal blend of gasoline consisted of a mixture o! catalytically cracked naphtha, the hydrogenated low-boiling fraction of cracked gasoline and iso-octane, and polymer gasoline. 'I'he resulting blend had an octane number of 84 which was increased by 3 cc. of tetraethyl lead solution to 93. 'I'he total yield of gasoline amounted to 87.5%. The operation involving only catalytic cracking and nonselective polymerization of the Ca and C4 olens resulted in a yield oi' approximately 82% of gasoline havingan octane number of 8l. The susceptibility of this gasoline to tetraethyl lead was less than that oi the gasoline from the present process having with 3 cc. of lead, an 88 octane number.

I claim as my invention:

1. A process which comprises contacting hydrocarbon distillate with a cracking catalyst at u' catalytic cracking conditions, separating the gas and gasoline. separating the gasoline into a lowboiling and a high-boiling fraction, separating the gaseous products into a plurality of fractions.

one of which comprises essentially hydrogen and uncondensable hydrocarbon gases, and another a fraction comprising essentially C; and C4 hydrocarbons, catalytically polymerizing the C: and C4 oleflns in said fraction. combining the polymers thereof boiling within the gasoline boiling range with the aforesaid low-boiling fraction of gasoline A from the catalytic cracking step'and the hydrogen-containing gas from the cracking step. contacting said mixture with a hydrogenation catalyst at hydrogenating conditions, recovering the hydrogenated product, and blending it with the high-boiling gasoline fraction from the catalyticl cracking step.

2. A conversion process which comprises cracking 'catalytically hydrocarbon oil to produce oieilnic gasoline, gaseous oleilns and hydrogen, fractionating the resultant products and separating therefrom a heavy gasoline fraction, a light gasoline fraction,y a butene-containing normally gaseous fraction an da hydrogen-containing gas,

subjecting said butene-containing fraction to polymerization to convert butenes to octenes, combining the latter with said light gasoline 'fraction and with at least a portion of said hydroenea, combining the mier with said, iight gasoline fraction and with at least a portion of said hydrogen-containing gas, subjecting the resultant mixture to hydrogenating conditions, and blending the saturated gasoline boiling hydrocarbons thus produced with said heavy gasoline fraction.

C HARLES L; THOMAS.

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