US2381256A - Process for treating hydrocarbon fractions - Google Patents

Description

Aug. 7, 1945.

J. R. cALLAwAY PROCESS FOR TREATING HYDROCARBON FRACTIONS Filed Oct. 6, 1942 new All

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JOHN R,CA| l.AwAY

INVENTOR BY frfbwm;

HIS ATTORN Y uniba 8E uzbmow.

Patented Aug. 7, 1945 OFFICE I,

PROCESS FOR TBEATING HYDROCARBON FRACTIONS John Richard Callaway, -Teaneck N. J., assignor to The Texas Company, New York, N. Y., a corporation of Delaware Application ,October 6, 1942, Serial No. 160,945

My application relates to the improvement of alkylation gasolines, and especially toa catalytic process for improving the quality of alkylates obtained by the alkylation of paraflinic hydrocarbons with olenic hydrocarbons..

Numerous processes have been developed for4 the production of gasoline range hydrocarbons from normally gaseous hydrocarbons, by eieoting alkylation of the parainicrcomponents, and especially the isoparailns, by means of olenic components. These processes include thermalalkylation and various liquid phase alkylation processes involving the use of catalysts, such as sulfuric acid, hydrouoric acid, aluminum chloride, and the like. Generally, all of these processes produce alkylates which are superior to be present in the alkylates, but the application of my process to most alkylates would not be eco- E ed. Such improvements include the reduction straight run gasolines in anti-knock properties.

However, in view of the continuing demand for higher and higher octane number gasolines', it is desirable to improve the quality'of the alkylates of the unsaturated hydrocarbon content of low quality alkylates, the decomposition of esters formed from inorganic acid alkylation catalysts, and other improvements in alkylate quality presumably due to molecular rearrangement of the saturated hydrocarbons. The mechanism of the process with respect to improvement of the saturated hydrocarbons is not understood, but may be partially due to direct isomerization, and partially a lresult of depolymerization of olen polymers inthe alkylate and catalytic vapor phase v alkylation of isoparaflns in the alkylate by means produced by any of the present alkylation procedures. This is especially true if the alkylatin process is carried out under conditions `favorable to maximum throughput, rather than under op'- timum conditions for the highest quality aleven more, below the octane number which could be obtained under optimum reaction conditions.

A An object of the present invention is to provide a process for the treatint of hydrocarbon fractions obtained by the alkylation of paraiiinic hydrocarbons with olenic hydrocarbons to improve the' motor fuel characteristics of such fractions.

Another objectV of the present invention is to provide a catalytic process for the treatment of alkylates to eiect an improvement in their antiknock characteristics.

A further object of this-invention is to provide an ,alkvlation process in which decreased alkylate quality, resulting from inferior charge stocks,

' catalyst,`s subjected to contact with an adsorp- A tion type' catalyst at elevated temperatures, preferably not greatly below the cracking temperature range. 'I'his treatment willdecompose mercaptans and other sulfur compounds whichmay kylate. 'In such cases, the octane number of the lalkylate produced may be from 1 to 3 points, or

at which substantial cracking occurs.

of the depolymerized olefins thus produced. In any event, it is to be understood. that my invenf tion is not to be limited to any particular theory with respect to its operation.

The catalysts which may be employed in my process comprise any of the adsorption type catalysts which are employed in other types of hydrocarbon treating operations, such as the clay catalysts used in decolorizing, desulfurizing, and cracking operations. These catalysts, which are commonly referred to as clay type catalysts or adsorption type catalysts," include the diatov'm'aceous earths (commonly known as fullers earth, kieselguhr, etc.) and the aluminum silicate clays, such as bauxites, bentonites, and the like. Among these catalyststhe most effective comprise the` acid treated bentonites, and especially. those from selected natural deposits which are particularly suited for the production of highly activated products by acid treating. The material sold under the trade name Super- Filtro is an example ofthe latter type of catalyst. Satisfactory results may be obtained in my process with any of these catalysts, but I prefer to use'a highly activated catalyst, such as Super- Filtrol, in any case where the improvement of product quality is sulcient to warrant the differ-J ential in catalyst cost.

The treatment of the present process is effected at temperatures suicientlyhigh to elect substantial isomerization,*and below a temperature Temperatures within the range 650-8501 F. will usually be satisfactory, and I generally prefer to employ a temperature of D-75,0?" F. The contact time or space velocity is not'critical, except at the higher temperature ranges. where excessive contact time may cause undue cracking. Space velocities of 0.1 Yto 1.0 volume of liquid alkylate per apparent volume of catalyst, will generally be satisfactory at temperatures of 70D-750 F. The space velocity may be varied, roughly in proportion to the temperature, when operating outside this range. Under these conditions, a catalyst A life of from 1000 to 5000 barrels of .alkylate per kylation process, or to a specific fraction of the alkylate such as an aviation gasoline fraction, or to a blend of alkylate and other motor fuel hydrocarbons. Since most alkylation processes involve the use of a large excess of parailnic hydrocarbon reactant, it will usually be desirable to remove the bulk of the unreacted gaseous hydrocarbons, for vrecycling to the alkylation process, prior to subjecting the alkylate to the present catalytic treatment.` In some cases, and especially when low quality alkylates are obtained, having substantial amounts of unsaturated hydrocarbons present, it-is desirable to include a small proportion of normally gaseous isoparaflln in the charge tothe catalytic treatment, in order to favor vapor phase alkylation, and effect reaction of the oleflnsolefln polymers, or depolymerized polymers. For this purpose, the separation of gaseous hydrocarbons for recycle -to the alkylationireaction is intentionally made incomplete, Further fractionation of the alkylate, prior to catalytic treatment, may be effected if desired, but it is usually more economical to eiect this fractionation subsequent to the catalytic treatment. 1n the latter case, a single fractionation may serve to separate any high boiling materials formed in the catalytic process, and also to separate the alkylate into desired fractions. The temperature of the vapors leaving the catalytic treatment is more than sufiicient to effect this final fractionation, and cooling to the proper fractionator feed temperature may b e suitably. effected by heat exchange with the alkylate passing to the heater for the catalytic treatment.

The catalyst treatment of lthe present Yinvention is applicable to alkylation reaction products obtained from any of the known alkylation processes, such as thermal alkylation, and catalytic alkylations employing aluminum halide catalysts or inorganic` acid catalysts; such as sulfuric acid or hydroiluoric acid. Alkylates obtained from the alkylation of either normal or i'soparailins may be treated by the present process, and such alkylates, may be obtained by the use of monomeric oleflns, the lower olefin polymers, or olen addition products such as alcohols or acidv sulfates, as the alkylating agents.

However, my prpcess is especially suitable for of the present invention is illustrated in the accompanying drawing. Referring to the flow diagram shown in the drawing, it may be seen that the alkylation of isobutane with butylenes, and the separation of the reaction mixture, are effected in a conventional manner. 'I'he separated oil phase, after caustic washing to remove residual sulfuric acid, is then subjected to distillation in a debutanizing column in accordance with the customary procedure. In the present process, substantially complete or only partial debutanization is effected, depending on whether or not isobutane is desired in the product to undergo the following catalytic treatment. The partially or completely debutanized alkylate then flows to the heater, which may be any conventional type such as a. direct fired tube still. Here, thev alkylate is vaporired and heated to a temperature of, say, 750 F. The hot vapors then flow to the top of the catalyst tower, entering at a temperature of about '740 F.

The catalyst tower may contain a single bed of catalyst, as shown, or a plurality of separate beds supported by perforated trays, 'or the like. The amount of catalyst charged is, of course, de-

pendent upon .the throughput of alkylate and the desired space velocity. For average alkylates being treated at the present illustrative temperature, the amount of catalyst may suitably be in the range Z50-2500 cu. ft. per 1000l bbl. of alkylate throughput per day.

, The treated allg/late, leaving the catalyst tower at a temperature of about720 F., may be cooled in a conventional heat exchanger to a temperature of about 480 F.,V thereby preheating the alkylatecharge for the heater to' about 300 F. The vapors leaving the heat exchanger then flow tothe product fractionator where the desired fractions of the alkylate may be separated. Any high boiling materials formed in the catalytic treatment may be removed as fractionator botltoms, and any unreacted gaseous hydrocarbons Example I Isobutane is alkylated with mixed refinery butylenes in a conventional manner, as shown in the flow diagram discussed above, using sulfuric acid of 98% initial and 88% sperrt concentration in a 1/1 volume ratio of acid to hydrocarbon. The reaction is effected in a Stratco Mixer reaction vessel at F., with' a contact time of 20 min., an external isobutane to olen ratio ofv about 6/1, and sufdcient emulsion recirculation in the reaction vessel to produce an internal isobutane to olefin ratio of approximately 1000/1. Using isobutane of purity for feed and recycle, the isobutanecontent of the reactor hydrocarbon mixture is about 67% under these conditions, the production of the unit is about 900 trated with specific'v references to this type of alkylation. K

One midilcation of a sulfuric acid alkylation process including' the lcatalytic treating process bbl. per day of total alkylate, with the depentanized aviation fraction having a CFRM octane number of 93.5.

The capacity of the unit is increased Ito 1800 bbl. per day by decreasing the external isobutane to olefin ratio to about 3.6/1 and the contact stability on assigne time to about 15 minutes for the same over-all liquid circulation. These conditions are further from the optimum than the former conditions,` and rtfh'e CFRM octane number of the aviation fraction obtained is only 91.5.

In order to increase the octane number ol! the trol" type acid treated bentonite in a single bed 10 ft. in diameter andapproximately 15 ft. deep. The space velocity thus obtainedis approximately 0.5 volume of liquid alkylate per apparent volume of catalyst per hour.

The CFRM octane number of .the depentanized and caustic Washed aviation fraction of the treated high productionalkylate may be as high as 93.5, or even higher. Inaddition 'to the improvement in anti-knock characteristics, the

catalytically treated alkylate is superior to iintreated alkylate in thesubstantial elimination of constituents such ,as alkyl sulfates, other 4sulfur compounds, and polymerizable compounds, all of which are undesirable in high quality aviation gasoline even when present only in traces.

Example II Isobutane is alkylated withy a mixture of 92 mol per cent propylene and8 mol per cent isobutylene using 98% sulfuric acid in an acid to hydrocarbon volume ratio of 1/1. The reaction is effected continuously in an agitated reaction vessel at a temperature of about '10 F., with' a contact time of 25 minutes.- With a. parafn Ito oleiln mol ratio in the charge ofv about 5/1, the yield of debutanized alkylate amounts to about 190%, based on the 4weight of the olefin charged. v -The CFRM octane number of the alkylate thus obtained is about 88.5.

The propylene alkylate obtained asdescrbed above is vaporized and passed through ful ers earth' at a temperature of about '700 F. and a space velocity of about 0.8 volume of liquid alkylate per apparent volume ofl fullers earth per hour. The treated alkylate is fractionated, and a 300 F. end point aviation fraction/"is taken off, and'iscausticwashed before exposure Ito air. The CFRM octane number of this treated alkylate maybe as high as 90.0, or even higher. In addition to the improvement in octane number, the treated alkylate'is improved fby the substantially completeelimination of propyl sulfate and gum-forming constituents, and in its superior storage in th'e presence of tetra/ethyl lead.

It shmua be understood, of course, that the above examples are merely illustrative and are not to be construed as limiting the scope of my invention. The procedure of theseexamples may be modified in numerous respects, such as the substitution of-diierent charge stocks, alkylation catalysts, or alkylating conditions, and the sub'- stitution of other adsorption type treating. cata- V-lectedgdlstillalte fractions. or by leaving a part or all ofthe unreacted isoparaflln in the alkylate high production alkylate to approximate that of until after the catalytic treatment. In general, it mayv be said that the use of any equivalents or modiilcations-of procedure which would naturally occur to those skilled in the art is included inthe scope of my invention. Only such' limitations should be imposed on the scope of my invention as are indicatedin Ithe'appended claims.

I claim:

1. In the manufacture of aviation gasoline the process that comprises charging normally gase ous olefins and isoparans to an alkylating zone wherein thefoleflns and isoparains are .contacted with sulfuric acid under alkylating conditions to produce normally `liquid hydrocarbons in the gasoline boiling range with a limited time of reaction insumcient to support conversion to an alkylate product of maximum anti-knock value, maintaining vthe proportion of isoparaflins to olens charged to the alkylating zone below that Anecessary to produce an alkylate product of maximum anti-,knock value and contacting resultantv gasoline alkylate with an adsorptive clay catalyst at a temperature of about G-850 F. with hydrocarbons of increased anti-knock value but insufcientto effect cracking to thereby increase the anti-knock value of the alkylate and produce a final gasoline product adapted for aviation gasoline. k

2. In the manufacture of aviation gasoline the process thatv comprises charging normally gaseous olens and isoparafllns to an alkylating zone wherein the olens and'isoparaiilns are contacted with sulfuric acid under alkylating conditions to produce normally liquid hydrocarbons in the gasoline boiling range with a limited time of reaction insuficient to support conversion to an alkylate product of maximum anti-knock value, maintaining theproportion of isoparamns to olens charged to the alkylating zone below that necessary to produce an alkylate product of maximum anti-knock value and contactingresultant gasoline alkylate with an adsorptive clay catalyst at a temperature of '70D-750 F. and a space velocity of 0.1-1.0 to effect molecular rearrangement of saturated hydrocarbons into hydrocarbons of increased anti-knock value to thereby increase the anti-knock value of the alkylate product without the cracking thereof and produce a nal gasoline product adapted for aviation gasoline.;

3. In the manufacture of aviation gasoline the process that comprises. charging-normally gasef ous oleflns and isoparailns to an alkylating zone wherein the oleiins and isoparafllns are contacted with sulfuric acid underl alkylating conditions to produce normally liquid hydrocarbons in the gasoline boiling rangewith a hunted time of reactioninsumcient to support conversion to an alkylate product of maximum anti-knock value,- maintaining the proportion of isoparafllns to oleilns charged to the alkylating zone below that necessary to produce an alkylate product of -maximum anti-knock value, debutanizing the alkylateproduct and contacting the debutanized alkylate with an adsorptive clay catalyst at a temperature of'about G50-850 F. with a time of contact adequate to eifect molecular rearrangement of 4saturated hydrocarbons into hydrocarbons of increased anti-knock lvalue but insumcient to eiTect cracking to thereby increase the anti-knock value of the alkylate and produce a 4. In the manufacture of aviation gasoline the process that comprises charging normally gaseous clefins and isoparains to an alkylating zone wherein the oleins` and yisoparamns are contacted with sulfuric acid under alkylating conditions to produce normally liquid hydrocarbons in the gasoline boiling rangqrwith a limited time of reaction insuftlcient to support conversion to an alkylate product of maximum anti-knock value, maintaining the proportion of isoparamns to oletins charged to the alkylating zone below that necessary to produce an alkylate product of maximum anti-knock value and contacting resultant gasoline alkylate with fullers earth at a temperature

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