US2982800A - Means for producing branched hydrocarbons - Google Patents

Description

May 2, 1961 L. SPENADEL ETI'AL MEANS FOR PRODUCING BRANCHED HYDROCARBONS Filed Feb. 5, 1959 '3 3 CATA YST CATALYST L TREATiNG 23 ZONE '2 lo RECOVERY ,20 ZONE 4 TREATED CATALYST HYDROGEN 25 HALIDE l6 CONVERSION ZONE HYDROCARBON FEEDSTREAM Luyvrence Spenudel Relnhold O. Steiner Inventors R h- 3L Agent United States Patent MEANS FOR PRODUCING BRANCHED HYDROCARBONS Lawrence Spenadel and Reinhold 0. Steiner, Elizabeth,

N.J., assignors to Esso Research and Engineering Company, a corporation of Delaware Filed Feb; 5, 1959, Ser. No. 791,378

6 Claims. (Cl. 260-683.53)

lines of the present have a higher octane than the,

premium fuel of only a few short years ago. Among the ways advanced for securing requisite high octane constituents have been conversion processes designed to convert parafiin hydrocarbon, e.g. normal C to C fractions, into isopar-affinic and branched chain molecules. It is well known that isoparafiins have substantially better octane characteristics than their normal parafiin counterparts. Additionally the art recognizes that aromatics, such as benzene and toluene, also exhibit good octane qualities.

Among the processes heretofore advanced for the conversion of paraflins into more desirable isoparaffins is paraflin alkylation, sometimes termed paraflin disproportionation. Basically, this process involves contacting a'parafiin hydrocarbon, preferably of from 6 to 18 carbon atoms, with an excess of isobutane and/ or isopentane in the presence of a Friedel-Crafts catalyst, e.g. aluminum bromide. Among the products of reaction will be a substantial portion of isoparafl'in molecules having a number of carbon atoms intermediate to that of the normal parafiin and isobutane and/or isopentane feed. For example, reaction of normal heptane with isobutane will give good yields of isopentane and isohexane.

Normally, one of the most readily available feed materials for paraflin alkylation is a naphtha hydrocarbon fraction obtained by primary crude distillation or the paraflins left after removal of the aromatics from catalytically reformed or cracked naphtha. However, in addition to containing parafiins suitable for reaction, naphthas also contain substantial quantities, e.g. 1.0 to 40% of aromatics. The aromatics are mostly benzene, toluene, and xylenes. In addition to naphthas, other feeds such as kerosenes and higher boiling hydrocarbons, also contain aromatics.

Heretofore, it had been found to be necessary to reduce the aromatic concentration in the feedstream to about no more than 0.1 wt. percent. It was found that higher concentrations of aromatics tended to destroy the catalytic activity of the prior art catalysts, and to give poor product yields, as well as forming sludge and polymers. Thus, conventional paraflin alkylation systems could not be operated to give desirable yields of branched chain products in the presence of substantial quantities of aromatics.

Consequently, it was previously necessary to subject parafiin alkylation feed to an aromatic removal step, generally a liquid extraction operation. This aromatic removal step greatly adds to the operating and investment 2,982,800 Patented May 2, 1961 ice costs of the overall system and thus adversely affects the incentive for employing parafiin alkylation to up grade normal parafiins. I

Thus, there exists in the art a demand for a paraffin alkylation system capable of giving good yields of desired products in the presence of substantial quantities, e.g. 1 wt. percent or greater, based on normal paraffin feed of aromatics. The present invention serves to satisfy this need.

In accordance with the present invention, it has been found that by treating a particular catalyst in a specific manner prior to contacting it with the paralfin feed stream, large quantities of aromatics are readily tolerated in the reaction zone.

More specifically, a catalyst comprising aluminum chloride on an aluminum oxide, preferably gamma aluminum oxide, support is first treated with a hydrogen halide gas, e.g. hydrogen chloride, in the absence of substantial quantities of paraffin feed materials. The catalyst treated in this manner is thereafter contacted with hydrocarbon reactants, i.e. a paraffin stream having a substantial aromatics concentration, parafiins thereby being converted into isoparafiins. Not onlymay paraffins be converted to isopar-afins in the presence of aromatics, but the product stream will be a particularly good high octane material since aromatics as well as isoparaflins exhibit good octane products.

The initial treatment of the catalyst may be carried out at a Wide range of temperatures. Room temperature gives satisfactory results and may be preferred for simplicity of operation. Hydrocarbon conversion is preferably effected at a temperature in the range of to 300 F.

The use of aluminum chloride rather than aluminum bromide on aluminum oxide support is desirable since aluminum chloride, a weaker acid, forms a weaker complex with the aromatics present in the feed. This complex is then more readily dissociable into components active for promoting the desired paraflin reactions.

It is to be clearly understood that the present invention is distinguished from the prior art practice of adding a hydrogen halide to the hydrocarbon feed stream in the reaction zone. It is only by the separate hydrogen halide treatment of the catalyst in the absence of feed materials that exceedingly good yields may be ultimately obtained in the presence of aromatics. Further, no claim is herein made that a catalyst of aluminum chloride on an aluminum oxide support, per se, is novel but rather such a catalyst treated in accordance with the present invention was not heretofore known in the art.

The various aspects and modifications of the present invention will be made more clearly apparent by reference to the following description, drawing and specific embodiment.

The drawing depicts one of the possible methods of carrying out the present invention, the method being characterized by distinct vessels for catalyst treating and hydrocarbon reaction.

Turning to the drawing, shown therein is a system comprising catalyst treating zone 10, hydrocarbon conversion zone .11 and product recovery zone 12.

In catalyst treating zone 10, a catalyst of 40 wt. percent aluminum chloride on an aluminum oxide support is activated. The catalyst may be fresh, spent, or par-- tially spent catalyst withdrawn from a conversion vessel, as well as mixtures thereof. As noted previously, zone 10 may operate at a wide range of temperatures," e.g. 0 to 300 F. In the embodiment illustrated it is maintained at 70 F.

Catalyst is introduced in zone 10 through line 13. 1 It is maintained therein in the form of a moving or stationary fixed bed, fluidized bed, or the like. Depending vessel simply as a regeneration zone.

upon catalyst demands, the activation zone is operated continuously or in batch fashion.

Hydrogen halide gas, e.g. hydrogen chloride, is fed passed to hydrocarbon conversion zone 1111. Conversion zone 11 may be a fixed or moving solids bed, a fluidized bed or in general any of the conventional types of paraffin alkylation zones. It is maintained at a temperature of 200 F. A pressure of 100 p.s.i. to 1000 p.s.i. is generally employed.

Anaphtha stream having a boiling range of 340 to 360 F. is fed to the reaction zone through line 17, although any feed boiling between 160. F. and 700 F. is suitable. It has an aromatics concentration of 15 wt. percent based on C feed, and contains anormal paraffin such as normal heptane. A relatively lower molecular weight isoparafiin, i.e. isobutane, is fed by line 18 and the total charge introduced into the reaction zone 11 by inlet 19. Generally, an excess of isobutane is employed, e.g. 1.1 to 10 mols per mol of normal heptane in the feed.

In the reaction zone, paraifm disproportionation takes place in the presence of large quantities of aromatics. In the present embodiment, liquid phase conditions are utilized, although vapor phase may also be employed by a suitable control of pressure and temperature. The products consist of isopentane and isohexane as well as unreacted isobutane, normal heptane and aromatics.

The product eflluent rich in isoparafiiins is withdrawn by line 20 and passed to product recovery zone 12.

Zone 12 may be a distillation vessel or the like. Unseacted isobutane, feed and dissolved aluminum chloride may be recovered through lines 21 and 25, respectively, and recycled by means not shown. The amount of dissolved AlCl is small, usually less than 0.1 wt. percent. Various product fractions are recovered through outlets 22 and 23. For example, a product may be withdrawn through line 23, and lighter product fraction through line 22.

Catalyst is periodically or continuously withdrawn from the reaction zone through line 24. It may simply be recycled to zone for further activation, discarded, or first contacted with aluminum chloride prior to passing to treating zone 10.

Various modifications may be made to the system described above. Thus, for example, catalyst treating and hydrocarbon conversion may be alternately carried out in the same vessel, e.g. halting the feed and using the Further, several vessels can be operated together. By periodically changing the circulation of the oil feed, each vessel may be successively operated as a catalyst activating zone into which hydrogen halide is passed to rejuvenate the catalyst.

In its broadest aspects, the present invention is applicable to isomerization reactions as well as paraffin alkylation systems. Isomerization reactions convert paraflin feed material into isomeric molecules of sub stantially the same carbon number as the feed, and are well known in the art per se. Appreciable quantities of aromatics heretofore were similarly not compatible with the securing of desired yields and thus the present invention will greatly reduce or eliminate the costs of remove ing aromatics from the feed oil stream to an isomeriza= tion zone.

The following table presents a compilation of data applicable to the systems heretofore described.

, Table 1 Bread Preferred Range Range WIt. Percent A1013 in A1 03 Supported Oata- 10 to 200 50 to 100. st. Quintlty of Hydrogen Halide Employed to 0.1t020 0.5 to 1.0.

Treat Catalyst in Activation Zone, Vol./ Vol. of Oat/Hr. Reaction'Temperature, F 50 to 350. 200 to 300. Wt. Percent of Aromatics in Feed to Reaction 0 to 70 1 to 20.

Zone based on Normal Paraffin Feed.

To illustrate the unique nature of the present invention, the results of several experiments will now be discussed. As indicated below in Table 2, a paraifin alkylation feedstrearn containing a high concentration of aromatics, i.e. 37 wt. percent based on normal parafiin feed, was converted at the same residence time and temperature levels but with differently treated catalysts. The total C and C wt. percent of the 0 product is employed as the index of the yield of desired products since they are the main high octane components in the products. C +C is nearly the exclusive product, the rest of the product stream being mainly unreacted C and isobutane. c

In Runs 3 and 4, no hydrogen halide gas was contacted with the catalyst. In Runs'z and 2a, hydrogen chloride was introduced into the reaction zone along with the paraflin feedstock as is conventional practice. Run 1 illustrates the practice of the present invention wherein the catalyst of AlCl on gamma-alumina was first treated with about 10 v./v./hr. of hydrogen chloride at a temperature of 70 F. in the absence of feed hydrocarbons. The treated catalyst was then used for converting the parafiin feedstock.

Table 2 Total O5+Gfl Wt. percent on 05+ Product (benzene not included)---" 45.3 25.4 15.7 18.2 7.0

EOl gas passed over 'y-AlzOa before catalyst employed in reaction Z011 Comparison of Runs 3 and 4 indicates that aluminum halide catalysts which have never been contacted with hydrogen halide give poor yields in the presence of a substantial quantity of aromatics. Moreover, it is noted that AlCl performs better than AlBr in the presence of arcmatics.

Simply maintaining hydrogen halide in the reaction during paraffins conversion offers slight improvement in yields (Runs 2 and 2a and still results in relatively low yields when aromatics are present.

In contrast with Runs 2, 2a, 3 and 4, application of the present invention resultsin greatly improved yields (approximately 250% greater than A101 catalyst alone) and makes reactions in the presence of large quantities of aromatics feasible.

Summarily, by operating in accordance with the present invention, paraifins can now be successfully converted to good yields of isoparafiins without necessitating aromatics removal from the parafiin feedstock. Both operational and investment costs of the overall conversion system are thereby greatly reduced.

Having described the present invention, that which is sought to be protected is succinctly set forth in the appended claims.

What is claimed is:

1. An improved method for carrying out paraflin a1-= kylation which comprises the steps of, contacting a catalyst comprising aluminum chloride on an aluminumoxide support with a hydrogen halide gas in the absence of substantial quantities of paraffin feedstock, thereafter contacting the thus treated catalyst with a feed stream comprising normal parafiins, a lower molecular Weight isoparaflin and a substantial proportion of aromatics at a reaction temperature so as to convert said normal paraffins into isoparaflins having a number of carbon atoms intermediate to that of said normal paraflins and said lower molecular weight isoparafiin.

2. The process of claim 1 wherein the reaction temperature is in the range of 200 to 300 F. and said aluminum oxide support is gamma aluminum oxide.

3. The process of claim 1 wherein said hydrogen halide gas is hydrogen chloride and said feed stream contains at least 10 Wt. percent aromatics based on normal paraifin feed.

4. A paraflin alkylation process for converting paraffins into isoparafiins in the presence of substantial quantities of aromatics which comprises treating a catalyst comprising aluminum chloride on a gamma aluminum oxide support with hydrogen chloride in the absence of substantial portions of paraflin feedstock, thereafter contacting said thus treated catalyst at a reaction temperature in a reaction zone with a feed containing paraffins, a relatively low molecular weight isoparaflin and at least 1.0 wt. percent aromatics based on normal parafiin feed so as to convert said parafiins to isoparafiins having a number of car-.

6 bon atoms intermediate to that of said paraflins and said low molecular weight isoparaffin.

5. The process of claim 4 wherein said reaction temperature falls within the range of 200 to 300 F.

6. An improved paraflin alkylation system which comprises treating an aluminum chloride catalyst supported on a gamma aluminum oxide support with hydrogen chloride in the absence of substantial quantities of parafiin feed material, thereafter contacting in a reaction zone at a temperature of 200 to 300 F. the thus treated catalyst with a feed stream comprising normal parafiins, a lower molecular weight isoparafiin and at least 1.0 wt. percent aromatics based on normal paraflins, branched paraffins having a number of carbon atoms inter-mediate to that of said normal paraflins and said lower molecular weight isoparaffin thereby being, produced in the presence of the large quantities of aromatics.

References. Cited in the file of this patent UNITED STATES PATENTS 2,208,362 Engel July 16, 1940 2,298,383 Ipatiefi et a1. Oct. 13, 1942 2,349,458 Owen et a1. May 23, 1944 2,351,577 Thomas June 13, 1944 2,405,516 Pines Aug. 6, 1946 2,406,869 Upham Sept. 3, 1946 2,733,219 Bloch Jan. 31, 1956 FOREIGN PATENTS 598,952 Great Britain Mar. 2, 1948

Claims (1)

1. AN IMPROVED METHOD FOR CARRYING OUT PARAFFIN ALKYLATION WHICH COMPRISES THE STEPS OF, CONTACTING A CATALYST COMPRISING ALUMINUM CHLORIDE ON AN ALUMINUM OXIDE SUPPORT WITH A HYDROGEN HALIDE GAS IN THE ABSENCE OF SUBSTANTIAL QUANTITIES OF PARAFFIN FEEDSTOCK, THEREAFTER CONTACTING THE THUS TREATED CATALYST WITH A FEED STREAM COMPRISING NORMAL PARAFFINS, A LOWER MOLECULAR WEIGHT ISOPARAFFIN AND A SUBSTANTIAL PROPORTION OF AROMATICS AT A REACTION TEMPERATURE SO AS TO CONVERT SAID NORMAL PARAFFINS INTO ISOPARAFFINS HAVING A NUMBER OF CARBON ATOMS INTERMEDIATE TO THAT OF SAID NORMAL PARAFFINS AND SAID LOWER MOLECULAR WEIGHT ISOPARAFFIN.

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