US3494970A - Preparation of aryl-substituted normal paraffin hydrocarbons - Google Patents

Description

United States Patent 3,494,970 PREPARATION OF ARYL-SUBSTITUTED NORMAL PARAFFIN HYDROCARBONS Joe M. Pharis, Downers Grove, 11]., assignor to Universal Oil Products Company, Des Plaines, 11]., a corporation of Delaware Filed July 26, 1968, Ser. No. 747,948 Int. Cl. C07c 3/54, 5/20 US. Cl. 260-671 12 Claims ABSTRACT OF THE DISCLOSURE An aryl-substituted normal paraffin hydrocarbon is prepared from a first charge stock, containing a normal paraffin hydrocarbon having about 6 to about 20 carbon atoms and a dehydrogenation catalyst-deactivating cyclic contaminant, and from a second charge stock, containing an alkylatable aromatic hydrocarbon, by the steps of: (a) contacting the first charge stock, the second charge stock, and a stream containing unreacted normal paraffin hydrocarbon and a normal mono-olefin having the same number of carbon atoms as the normal paraffin hydrocarbon with a liquid alkylation catalyst at conditions suflicient to produce a substantially cyclic contaminant-free effiuent stream containing an aryl-substituted normal paraffin hydrocarbon, and unreacted alkylatable aromatic hydrocarbon, and an unreacted normal paraffin hydrocarbon; (b) fractionating the efiluent stream from step (a) to produce a first fraction containing unreacted parafiin hydrocarbon, a second fraction containing unreacted alkylatable aromatic hydrocarbon, and a third fraction containing the aryl-substituted normal paraffin hydrocarbon; (c) contacting said first fraction and hydrogen with a dehydrogenation catalyst at conditions sufiicient to produce an eflluent stream containing unreacted normal paraflin, a normal mono-olefin having the same number of carbon atoms as the normal paraffin hydrocarbon, hydrogen and a minor amount of hydrocarbons boiling below the normal parafiin hydrocarbon; (d) separating hydrogen and the hydrocarbons boiling below the normal parafiin hydrocarbon from the effluent stream from step (c) to obtain the stream containing unreacted normal parafiin and the normal monoolefin; (e) passing the stream formed in step (d) to step (a); and (f) recovering the third fraction as the product. Key feature of the resulting process involves charging the normal paraffin-containing charge stock to the alkylation step instead of directly to the dehydrogenation step, thereby facilitating control of the dehydrogenation catalyst deactivation produced by the cyclic contaminant contained in this charge stock and improving the selectivity and stability of the dehydrogenation step.

The subject of the present invention is an improved process for the preparation of an aryl-substituted normal paraffin hydrocarbon using a hydrocarbon feed stream containing the corresponding normal paraffin and a catalyst-deactivating cyclic contaminant. More specifically, the present invention comprises a method of improving the performance of a combination process which operates on an input stream containing long chain normal paraflin and a minor amount of a dehydrogenation catalyst-deactivating 3,494,970 Patented Feb. 10, 1970 cyclic contaminant, and a second input stream containing an alkylatable aromatic hydrocarbon. In this combination process the essential steps are: dehydrogenation of the first input stream to produce long chain normal monoolefins corresponding to the normal paraifin without producing any undesired side products, and alkylation of the second input stream with the resulting product stream from the dehydrogenation step to produce the desired aryl-substituted normal paraffin hydrocarbon. The problem addressed by the present invention involves the minimization of the adverse effect of the cyclic contaminant contained in the first input stream on the dehydrogenation catalyst utilized in the dehydrogenation step.

One of the major problems prevalent in centers of population throughout the world is the disposal of sewage containing detergent in small quantities. Such disposal problems are especially vexacious in the case of those detergents having an arylalkane structure as the nuclear portion of the detergent molecule. These detergents produce stable foams in hard or soft water in such large quantities that the foam clogs sewage treatment facilities and often appears in sufficient concentration in such facilities to destroy the bacteria necessary for sufiicient biological action for proper sewage treatment. One of the principal offenders of this type of detergent is the alkylaryl sulfonates, which, unlike the fatty acid soaps, do not precipitate when mixed with hard water containing calcium or magnesium ions. And since these compounds are only partly biodegradable, the detergent persists in solution and is carried through the sewage treatment plant in substantially unchanged form. Having a tendency to foam, especially when mixed with aerating devices and stirrers, large quantities of this detergent are discharged from sewage digestion plants into rivers and streams where the continuing presence of the detergent is evidenced by foam on the surface of these streams. Other offenders of this type of detergent are the polyoxyalkylated alkyl phenols and the alkylphenylpolyoxyalkylated amines. These synthetic detergents also interfere with the anaerobic process of degradation of other materials, such as grease, and thus compound further the pollution cause by sewage plant eflluents containing such detergents.

It has been established that the biodegradability of the ultimate detergent product is determined by the arylalkyl compound that is used in the preparation of the detergent. And more particularly, it has been determined that these detergents are more readily degradable by sewage bacteria if the long chain alkyl substitutent on the aromatic nucleus is of a simple, straight-chain configuration. In fact, the preferred intermediate from the biodegradability stand-point is an aryl-substituted normal paraffin hydrocarbon. Consequently, there has been established a substantial requirement for this type of hydrocarbon. In view of the fact that this type of hydrocarbon is customarily prepared by an alkylation operation, it is commonly referred to in the art as a species of detergent alkylate or linear detergent alkylate; for example, a linear alkylbenzene.

The linear detergent alkylate can be converted into a wide variety of detergents as is well-known to those skilled in the art. For example, the detergent alkylate may be sulfonated and thereafter neutralized with a suitable alkaline base, such as sodium hydroxide to form an alkylaryl sulfonate (anionic) type of detergent which is most widely used for household, commercial and industrial purposes. The detergent alkylate can also be converted to a non-ionic type of detergent by nitrating the alkylate to form a nuclearly mono-nitrated intermediate which on reduction yields the corresponding alkylarylamine. The amino radical is thereafter reacted with an alkylene oxide of an alkylene epichlorohydrin to form an alkylaryl-polyoxyalkylated amine (containing from 4 to about 30 oxyalkylene units) which is a highly effective detergent. Another large class of detergents are the oxyalkylated phenol derivatives in which an alkylphenol base is prepared by alkylation of a phenol. Still other products having an alkylaryl base are widely known in the arts, although alkylaryl sulfonates constitute the largest single class of surfactant products which are typically synthetized from this detergent alkylate.

Responsive to the demand for this linear detergent alkylate, the art has come up with a number of ways to use normal parafiins as a source for the straight chain alkyl substituent on the aryl nucleus. A preferred route to the detergent alkylate involves the steps of: selective catalytic dehydrogenation of the normal parafiins to the corresponding normal mono-olefin having the same number of carbon atoms, followed by alkylation of an alkylatable aromatic with the resultant normal mono-olefin using an acid-acting catalyst to yield an aryl-substituted normal parafiin hydrocarbon. The dehydrogenation step typically operates on normal paraffin hydrocarbons having about 6 to about 20 carbon atoms to produce a normal monoolefin having the same number of carbon atoms. The alkylation step typically has a dual function: the first being the separation of the product olefin from the unreacted normal parafiins, and the second being the preparation of the desired arylalkyl hydrocarbon. In this combination process, a dehydrogenation catalyst is preferably employed which has a high selectivity for the production of a normal mono-olefin with the complementary capability to suppress undesired side reactions such as skeletal isomerization, secondary dehydrogenation, cyclization, dehydrocyclization, polymerization, cracking, etc. In view of the fact that equilibrium considerations necessarily limit conversion levels in the dehydrogenation step, the economics of the resulting process require that the unreacted normal parafiins be recovered from the mixture of reactants and products withdrawn from the alkylation step and recycled to the dehydrogenation step. The preferred procedure for separating the unreacted normal parafiins from the effluent from the alkylation step is fractionation; accordingly, any refractory material or cataylst-deactivating contaminants that boil within the range of the unreacted normal parafiins and that are present in the alkylation step efiluent, can accumulate in the normal parafiin recycle stream and cause rapid dehydrogenation catalyst deactivation.

The problem addressed by the present invention stems from the commercial necessity of charging to this combination process a normal paraffin-containing feed stream that contains minor amounts of dehydrogenation catalystdeactivating contaminants. Typically, this situation is encountered where the feed stream to the combination process is derived from a hydrocarbon distillate, containing both normal and non-normal hydrocarbons in the desired boiling range, by a selective extraction Process using a bed of molecular sieves of the proper pore size. In this type of separation operation there is a trade-off between extract product purity and yield which normally is resolved by allowing a minor amount of non-normal components to be included in the extract stream from the system. It has been determined that the non-normal portion of the substantially pure normal paraffin-containing stream from this type of separation process can contain cyclic compounds such as alkylnaphthenes, alkylaromatics, bi-cyclic naphthenes, alkylindanes, polycyclic aromatics, etc., which have the capability to deactivate the dehydrogenation catalyst used in the dehydrogenation step of this preferred process. Regardless of how these contaminants get into the feed stream for the dehydrogenation step, it is clear that their presence can rapidly jeopardize the stability and product quality of the preferred process for making detergent alkylate because the dehydrogenation catalyst-deactivation produced thereby is ordinarily compensated for by raising the severity in the dehydrogenation step, leading to a decrease in selectivity for the desired normal mono-olefin and accelerated deactivation of the catalyst. This last effect is caused by side products synthesized in the dehydrogenation step, some of which are more refractory that normal paraffins (e.g. isoparafiins) and others of which are potential catalyst deactivators (e.g. alkylaromatics), coupled with the multiplying effect of the recycle parafiin stream when these materials collect therein.

Hence the problem is to pretreat the normal paraffincontaining feed stream to remove these cyclic contaminants without generating any substantial quantities of nonnormal hydrocarbons, and I have now found a convenient and simple method for accomplishing this objective. In essence, my method involves charging the fresh normal paraffin-containing feed stream to the alkylation step of the combination process instead of directly to the dehydrogenation step. More particularly, I have found that by charging the hydrocarbon feed stream to the alkylation step the cyclic contaminants contained therein are selectively soluble in the liquid alkylation catalyst, which is preferably hydrogen fluoride, used in the alkylation step such that the cyclic contaminants contained in this feed stream are removed from the hydrocarbon phase and transferred to th ecatalyst phase, thereby cleaning-up the normal paraffin-containing feed stream. In view of the inert character of the normal paraffin hydrocarbons contained in this feed stream, this procedure has essentially no adverse effect on the performance of the alkylation step, and essentially allows the alkylation step of the combination process to simultaneously perform a feed-stream-cleanup function. The principal benefit derived from the present invention is the relative ease and simplicity by which it can clean-up this feed stream, as contrasted with the cumbersome alternative procedure involving an entirely separate acidtreating step performed on this feed stream; that is, the present invention eliminates the necessity of a separate treating step designed to remove cyclic contaminants.

It is, accordingly, one object of the present invention to provide an improvement in the performance of a combination process for the synthesis of an aryl-substituted normal paratfin hydrocarbon from a normal paraflin hydrocarbon and an alkylatable aromatic hydrocarbon wherein the stream containing the normal paraffin hydrocarbon also contains a dehydrogenation catalyst-deactivating cyclic contaminant. A second object is to improve the quality of the linear detergent alkylate produced by such a combination process. A third object relates to a combination process invloving a dehydrogenation step and an alkylation step wherein a non-acid, alumina-supported, platinum metal-containing catalyst is used to dehydrogenate a hydrocarbon feed stream containing parafiln hydrocarbons and a catalyst deactivating cyclic contaminant and wherein unreacted normal paraffins are recovered and recycled to extinction, the object being to improve the selectivity and stability of the dehydrogenation step. Another object relates to a combination process, involving a dehydrogenation step and an alkylation step, using a contaminated normal paraffin feed stream, the object being to provide a simple and convenient means for contaminants from this feed stream prior to its passage to the dehydrogenation step.

In one embodiment, the present invention comprises a process for the preparation of an aryl-substituted normal paraffin hydrocarbon using a first charge stock, con

raining a normal parafiin hydrocarbon having about 6 to about 20 carbon atoms and a dehydrogenation catalystdeactivating cyclic contaminant, and a second charge stock, containing an alkylatable aromatic hydrocarbon where the boiling point range of the first charge stock is substantially different from the boiling point range of the second charge stock. The process comprises the steps of: (a) contacting the first charge stock, the second charge stock, and a subsequently produced stream containing unreacted normal paraffin and a normal mono-olefin having the same number of carbon atoms as the normal paraffin, with a liquid alkylation catalyst at conditions sufiicient to produce a substantially cyclic contaminant-free efiluent stream containing an aryl-substituted normal paraffin hydrocarbon, unreacted alkylatable aromatic hydrocarbon, and nnreacted normal paraffin hydrocarbon; (b) fractionating the effluent stream from step (a) to produce a first fraction containing unreacted normal paraffin hydrocarbon, a second fraction containing unreacted alkylatable aromatic hydrocarbon, and a third fraction containing the aryl-substituted normal paraffin hydrocarbon; (c) contacting the first fraction and hydrogen with a dehydrogenation catalyst at conditions sufiicient to produce an effluent stream containing unreacted normal parafiin, a normal mono-olefin corresponding in carbon number to the normal parafi'in, hydrogen and a minor amount of hydrocarbons boiling below said normal parafiin hydrocarbon; (d) separating hydrogen and hydrocarbons boiling below the normal paraffin hydrocarbon from the effluent stream from step (c) to obtain the stream containing unreacted normal parafiin and the normal monoolefin; (e) passing this last stream to step (a); and f) recovering the third fraction as product.

In another embodiment, the present invention includes the process as outlined above wherein the first charge stock contains a mixture of C to C normal parafiin hydrocarbons, wherein the alkylatable aromatic hydrocarbon is benzene, and wherein the product therefrom comprises phenyl-substituted C to C normal paraffin hydrocarbons.

A third embodiment is the process described in the first embodiment wherein the cyclic contaminant present in the first charge stock is an alkyl aromatic hydrocarbon, an alkyl 'indane, a polycyclic aromatic hydrocarbon or a mixture of any these.

A fourth embodiment relates to the process outlined in the first embodiment wherein the dehydrogenation catalyst contains alumina, about 0.01 to about 1.5 wt. percent lithium, about 0.05 to about 5.0 wt. percent platinum, and arsenic in an amount of about 0.1 to about 08 atoms of arsenic per atom of platinum.

Another embodiment consists of the process described in the first embodiment wherein the liquid alkylation catalyst is hydrogen fluoride or sulfuric acid.

Other embodiments and objects of the present invention encompass further details about: the normal paraffins and alkylatable aromatics that can be charged thereto, the type of catalysts that can be used in the dehydrogenation step and alkylatio-n step associated therewith, the process conditions used in each step thereof, the mechanics of the conversion, separation, and product recovery steps employed therein, etc. These embodiments and objects are disclosed in the following detailed discussion of each of these facets of the present invention.

Before proceeding to a detailed discussion of the elements of the present invention, it is necessary to define certain terms and phrases used herein. The phrase arylsubstituted normal paraffin hydrocarbon denotes a secondary aryl-substituted alkane having two straight-chain alkyl group on the resulting t-ri-substituted carbon atom attached to the aryl nucleus; for example:

where R and R are normal alkyl groups. The phrase normal or straight-chain hydrocarbon refers to a hydrocarbon having all carbon atoms linked in a continuous chain. The phrase liquid hourly space velocity (LHSV) is to be construed to refer to the equivalent to the conversion zone per hour divided by the volume liquid volume of the reference fluid charged to the conversion zone per hour divided by the volume of the zone containing catalyst.

The first charge stock to the process of the present invention containers normal paraffin hydrocarbons having at least 6 carbon atoms and especially 9 to about 20 carbon atoms. Representative members of this class are: hexane, heptane, nonane, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, heptadecane, octadecane, nonadecane, eicosane, and mixtures thereof. Hydrocarbon streams containing normal parafiins having 10 to 15 carbon atoms are particularly advantageous since these produce mono-olefins which can be utlized to make detergents having superior biodegradability and detergency. For example, a mixture containing a four or five homologue spread such as a C to C mixture, a C to C or a C to C mixture, are excellent charge stocks. Moreover, it is preferred that the amount of non-normal hydrocarbons present in this hydrocarbon stream be kept at low levels. Thus, it is preferred that this stream contain greater than wt. percent of normal parafiin hydrocarbon, with best results achieved at purities in the range of 96 to 98 wt. percent or more. In accordance with the present invention all of the charge stocks which are used in the present process contain a catalystdeactivating cyclic contaminant which, as discussed hereinbefore, is typically a mixture of cyclic compounds with alkyl aromatics, alkyl indanes, bi-cyclic naphthenes, and polycyclic aromatics being especially detrimental. Depending upon the source of the hydrocarbon stream these contaminants may be present in concentrations up to about 5 wt. percent. However, the typical concentration is substantially less than 1 wt. percent-about 0.1 wt. percent to about 0.8 wt. percent being representative of the situation encountered when the source of the charge stock is a preferred separation procedure employing molecular sieves.

In a preferred embodiment, the first charge stock is obtained by subjecting a hydrocarbon distillate boiling in the C to C range and containing normal paraffin hydrocarbons, naphthenes, aromatics, and isoparafiins, to a separation operation employing one or more beds of molecular sieves having a pore size of about 5 Angstrom units. These sieves have the wellknown capability to remove normal paraffin hydrocarbons from such a hydrocarbon distillate thereby producing a raflinate stream having a high concentration of the non-normal components originally present in the distillate stream. The normal paraffin hydrocarbons are thereafter recovered from the sieves, typically by displacement with a lower molecular weight normal paraffin hydrocarbon, to produce an extract stream containing normal parafiins and a minor amount of the displacing fluid. The extract stream is then typically subjected to a suitable fractionation operation designed to separate the displacing fluid therefrom and, in some cases, to adjust the boiling point range of the normal parafiin-containing stream. A preferred separation system for continuously producing this normal parafiincontaining hydrocarbon stream is described in the teachings of U.S. Patent No. 3,310,486 and reference may be had thereto for additional details.

Regardless of the exact mechanics of the separation operation used to produce the first charge stock, it is evident that a trade-off will exist between the quality of the extract stream, measured in weight percent normal paraffin hydrocarbon content, and the yield of the stream. Inevitably, in commercial practice, this trade-off is solved by allowing a minor amount of non-normal components to appear in the extract stream feeding to the process of concern here. For example, a preferred procedure for producing this charge stock involves charging a kerosene fraction boiling within the range of about 300 F. to about 500 F. to the separation system as described in U.S. Patent No. 3,310,486 and recovering therefrom a hydrocarbon stream containing a mixture of normal parafiins in the C to C range. Typically, this last procedure can be performed so that the hydrocarbon stream recovered therefrom contains 95 to 99 Wt. percent normal paraffin hydrocarbons with the remainder being isoparaflins and cyclic contaminants.

The second charge stock for the combination process of the present invention is a hydrocarbon stream containing an alkylatable aromatic hydrocarbon. In general, any suitable alkylatable aromatic hydrocarbon may be used in the process as long as it is separable from the normal paraffin hydrocarbons contained in the first charge stock by fractional distillation. That is, the boiling point range of the normal paraffin-containing charge stock must be substantially different from the boiling point range of the alkylatable aromatic-containing charge stock. It is preferred to utilize an alkylatable aromatic hydrocarbon containing no more than two alkyl substituents, especially when the product from the combination process is to be utilized for the production of detergents by subsequent sulfonation. Preferably, neither of the alkyl substituents on the aromatic nucleus are of greater chain length than the ethyl radical, and, more desirably, are methyl radicals. Thus, benzene, toluene, xylene, methyl ethyl benzene and diethyl benzene comprise preferred alkylatable aromatic b hydrocarbon. Moreover, it is particularly preferred to utilize benzene and/ or toluene for the production of detergents having the highest degree of acceptable performance. When aryl-substituted normal paraflin hydrocarbons are desired for purposes other than detergent production, it is also within the scope of the present invention to utilize other alkylatable aromatics as well as polycyclic aromatic hydrocarbons in the second charge stock. Thus, any alkylatable aromatic hydrocarbon containing a nuclearly substitutable hydrogen atom may be charged to the alkylation step including such compounds as 1,2,3-trirnethyl benzene, naphthalene, alkyl derivatives of naphthalene, etc.

Suitable catalysts for use in the dehydrogenation step of the present invention generally comprise one or more metallic components selected from Groups VI and VIII of the Periodic Table and compounds thereof. Such catalysts are generally composited with a carrier material which consists of one or more refractory inorganic oxides selected from the group of alumina, silica, zirconia, magnesia, and the like refractory oxides. It is particularly important that the catalyst employed in the dehydrogenation zone does not promote isomerization of the normal paraflins or of the resultant olefinic product. Accordingly, theh catalyst utilized is preferably made non-acidic by compositing it with one or more alkali metals, or alkaline earth metals, or compounds thereof. Furthermore, the conversion to the desired mono-olefin is enhanced when the noble metals of Group VIH are employed, with platinum being particularly preferred; in fact a preferred catalyst comprises a platinum group component and an alkali component combined with an alumina carrier material.

Insofar as degree of conversion and avoidance of side reactions is concerned, a particularly preferred catalyst for the dehydrogenation step comprises a combination of: an alumina component; a platinum group component; an alkali or alkaline earth metal component or compounds thereof; and a component selected from the group consisting of arsenic, bismuth, antimony, sulfur, selenium, tellurium, and compounds thereof.

The alumina component of this preferred catalyst generally has an apparent bulk density less than about 0.50 gm./cc. with a lower limit of about 0.15 gm./cc. Th surface area characteristics are such that the average pore diameter is about to about 300 Angstroms; the pore volume is about 0.10 to about 1.0 ml./ gm. and the urface area is about 100 to about 700 m. gm. It may be manufactured by any suitable method including the wellknown alumina sphere manufacturing procedure detailed in U.S. Patent No. 2,620,314. The preferred alumina is gamma-alumina.

The alkali component is selected from both alkali metals-cesium, rubidium, potassium, sodium and lithium and the alkaline earth metalscalcium, magnesium, and strontium, with lithium being preferred. It is present in an amount, based on the elemental metal, less than about 5% by weight of the total composite with a value in the range of 0.01% to about 1.5% generally being most preferred. In addition, the alkali component may be added to the alumina in any suitable manner, especially in an aqueous impregnation solution thereof, and thus suitable compounds are the chlorides, sulfates, nitrates, acetates, carbonates, etc., such as lithium nitrate. It may be added either before or after the other components are added, or during alumina formationfor example, to the alumina hydrosol before the alumina carrier material is formed.

The platinum group component is generally selected from the group of palladium, iridium, ruthenium, rhodium, osmium, and platinum-with platinum giving best results. It is used in a concentration, calculated as an el mental metal, of about 0.05% to about 5.0% by weight of the catalytic composite. This component may be composited in any suitable manner with impregnation by a water soluble compound, such as chloroplatinic acid, being especially preferred.

The fourth component is selected from the group consisting of arsenic, antimony, bismuth, sulfur, selenium, tellurium, and compounds thereof. Arsenic is particularly preferred. This component is typically used in an amount of about 0.01% to about 1.0% by Weight of the final composite. This component is preferably present in an atomic ratio to the Group VIH metallic component of from about 0.1 to about 0.8. Intermediate concentrations are preferably employed such that the atomic ratio is about 0.2 to about 0.5. This component can be composited in any suitable mannera particularly preferred way being via a water soluble impregnation solution such as arsenic pentoxide, etc.

After impregnation of each of the components, the catalyst is typically subjected to conventional drying and calcination treatments. In addition, the final catalyst may in some cases, be beneficially prereduced and sulfided. Additional details as to preferred dehydrogenation catalysts for use in the present invention are given in the teachings of U.S. Patents Nos. 3,291,755 and 3,310,599.

It is an essential feature of the present invention that the alkylation catalyst used has the capability to remove cyclic contaminants from the first charge stock. Suitable liquid alkylation catalysts are, accordingly, sulfuric acid of about concentration or higher and substantially anhydrous hydrogen fluoride generally not containing more than about 10% Water. In view of the high selective solubility of cyclic hydrocarbons especially aromatics in hydrogen fluoride, hydrogen fluoride is preferred.

Having characterized the catalysts used in the dehydrogenation step and the alkylation step of the present invention and the charge stocks used therein, reference is now had to the attached drawing for the detailed explanation of the flow schemes, process conditions, and operating parameters employed in the present invention. The attached drawing is merely intended as a general representation of the flow scheme employed in the present invention with no intent to give details about heaters, condensors, pumps, compressors, valves, process control equipment, etc., except where a knowledge of these devices is essential to an understanding of the present invention or would not be self-evident to one skilled in the art. In view of the fact that the present invention involves a combination process, no attempt is made in this drawing to represent details about the specifics of each of the process steps except where detailed information is essential for a proper understanding of the invention. In addition, in order to provide a working example of a preferred mode of the present invention, the attached drawing is discussed with reference to particularly preferred charge stocks and catalysts, the scope of these elements having been delineated above.

Referring now to the drawing, a first charge stock enters the process through line 1. This stream contains 0.3 wt. percent n-C 26.6 wt. percent n-C 31.3 wt. percent n-C 25.0 wt. percent n-C 13.2 wt. percent n-C and 0.4 wt. percent n-C In addition, this charge stock contains a minor amount of non-normal hydrocarbons comprising mono-olefins, mono-cyclic paraflins, diolefins, dicyclic paraflins, and alkyl aromatics, all of which boil Within the boiling point range of the first charge stock, and of which are about 1 wt. percent, based on weight of the first charge stock, are catalyst-deactivating cyclic contaminants. At the junction of line 18 with line 1, the first charge stock is commingled with a stream containrange and normal mono-olefins in the C -C range. The source of this stream flowing through line 18 will be hereinafter explained. This stream contains about 8 to about 12 wt. percent normal mono-olefins, and more typically about 10 wt. percent. In addition, the volumetric ratio of the stream from the line 18 to the volume of stream introduced by line 1 is typically about :1 to about 15: 1, depending somewhat on the amount of conversion to mono-olefin obtained in the dehydrogenation step as will be indicated below. That is, the amount of fresh normal paraffin-containing charge stock introduced by line 1 is ordinarily selected to be sufficient to compensate for the normal paraflins converted in the dehydrogenation step. In the particular case under discussion, the volumetric ratio of the stream in line 18 to the stream in line 1 is about :1. The resulting mixture of the streams from line 1 and line 18 flows through line 1 into alkylation system 2.

A second charge stock is also introduced into alkylation system 2 via line 9. As hereinbefore indicated, this second charges stock comprises an alkylatable aromatic hydrocarbon which for the case under discussion is a stream containing substantially pure benzene. At the junction of line 8 with line 9, a recycle stream containing unreacted benzene is commingled with the fresh feed stream and the resulting mixture is charged to alkylation system 2. The amount of the second charge stock introduced via line 9 is ordinarily chosen to compensate for the amount reacted in system 2.

Alkylation system 2 can comprise any suitable detergent alkylation process known to the art which uses a liquid alkylation catalyst of the type previously characterized. As already indicated, the preferred alkylation catalyst is a solution of hydrogen fluoride and for this catalyst the alkylation system preferably comprises: means for mixing the hydrogen fluoride stream with the hydrocarbon streams and attaining intimate contact therebetween, seprating means to remove the hydrocarbon phase from the HF phase after the desired reaction is complete, and means for stripping hydrogen fluoride from the hydrocarbon phase, and means for continuously regenerating the hydrogen fluoride stream. A preferred flow scheme for alkylation system 2, therefore, involves the steps of: admixing the benzene stream from line 9 with the stream entering the system via line 1 and therafter contacting the resultant hydrocarbon mixture with a continuously recirculated hydrogen fluoride stream. It is understood that these hydrocarbon streams may be simultaneously contacted with the hydrogen fluoride stream, or in admixture with each other, or the benzene stream may be contacted with the hydrogen fluoride stream followed by the addition of the hydrocarbon stream from line 1. The hydrogen fluoride stream is preferably substantially anhydrous hydrogen fluoride which in the course of use is typically degraded to a steady state acidity of about 93%.

ing unreacted normal paraffin hydrocarbons in the C -C L Conditions used in the contacting step are: a mole ratio of benzene to total olefin in the influent of about 10:1, a volume ratio of hydrogen fluoride to the total hydrocarbon influent of about 2: 1, a pressure sufficient to maintain the reactants and catalyst in the liquid phase, a temperature of about F. to about F. and a contact time of about 5 to about 80 minutes, with a contact time of about 20 minutes being preferred in the case under discussion. It is, of course, understood that the particular process conditions utilized in alkylation system 2 vary with the particular charge stocks and catalysts utilized to effect the alkylation and the technique for selecting the exact values of the process conditions as a function of these variables are well-known to those skilled in the art. In addition, suitable provision is made within the alkylation contacting step to remove excess heat generated by the reaction therein.

Following the contacting step, a stream containing the resulting mixture of hydrocarbons and hydrogen fluoride is passed to a separating means wherein a hydrocarbon phase separates from a hydrogen fluoride phase. The hydrogen fluoride phase is typically recycled to the contacting step, and the hydrocarbon phase is passed to a stripping column wherein hydrogen fluoride is taken over-head and an effluent stream containing phenyl-substituted C C hydrocarbons, unreacted benzene, and unreacted C C paraffin hydrocarbons is recovered as bottoms. This last stream is shown in the attached drawing as the output stream from alkylation system 2 leaving the system via line 3. Within alkylation system 2 the hydrogen fluoride stream that is recycled to the contacting step is typically continuously regenerated by withdrawing a side stream therefrom and passing this side stream to an acid regenerator means wherein hydrogen fluoride is purified by fractionation with a heavy tar-like material being recovered as disposed of. This tar-like material or acid sludge results from the hydrocarbonaceous material that collects in the hydrogen fluoride stream during the course of the alkylation reaction because of the high solubility of heavy organic material in hydrogen fluoride, coupled with the tendency of the hydrogen fluoride to react or complex with highly reactive species in the hydrocarbon influent such as diolefins, alkyl aromatics, naphthenic hydrocarbons, alkyl indanes, polycyclic aromatics, and other highly reactive hydrocarbons. Accordingly, the present invention utilizes the capability of the hydrogen fluoride stream to selectively extract cyclic materials from the hydrocarbon charge to the alkylation step to cleanup the first charge stock containing cyclic contaminants. Therefore, it is an essential feature of the present inven tion that the cyclic contaminant originally present in the first charge stock entering the process through line 1 is substantially removed by contact with the hydrogen fluoride catalyst so that the eflluent stream withdrawn from alkylation system 2 via line 3 is substantially free of the cyclic contaminant. For additional details as to the preferred flow scheme utilized within alkylation system 2 reference may be had to U.S. Patent No. 3,349,650 which describes a flow scheme for isoparaflin alkylation which gives excellent results when utilized with appropriate modifications, in the process of the present invention.

Following the alkylation step, the effluent stream therefore is passed via line 3 into fractionation system 4. The function of fractionation system 4 is to separate the hydrocarbon stream charged thereto a benzene-rich fraction, a C C normal paraflin-rich fraction, a phenyl-substituted C -C normal paraffin-rich fraction and, if desired, a heavy alkylation fraction. Preferably, the fractionation system comprises three conventional fractionation columns: the first producing a benzene-rich over-head which is recycled to alkylation system 2 via line 8; the second column operating on the bottoms from the first column (typically after suitable treatment for alkyl fluoride removal such as by treating the bottoms from the first column with an alumina material) and taking unreacted C C normal paraffins over-head which are passed to dehydrogenation zone 10 via line and the third column operating on the bottoms from the second column to produce phenyl-substittued C -C alkanes which are taken over-head and recovered via line 6 with a minor amount of heavy alkylate recovered as bottoms from this third column via line 7.

The unreacted normal paraffin hydrocarbon stream flowing through line 5 is commingled with a hydrogen stream at the junction of line 5 with line 13 in an amount of about 9 moles of hydrogen per mole of hydrocarbon. The resulting mixture is heated (by means not shown) to the desired conversion temperature and passed to dehydrogenation zone 10. Zone 10 contains a fixed bed of inch spherical catalyst particles prepared according to the method given in US. Patent No. 3,291,755 and containing, on an elemental basis, 0.76 wt. percent platinum, 0.041 wt. percent arsenic, 0.55 wt. percent lithium, combined with a gamma-alumina carrier material. Furthermore, the catalyst has an ABD of about 0.46 gm./cc., a surface area of about 145 m. gm. and a pore volume of about 0.40 rnl./gm. Dehydrogenation zone 10 is operated at an outlet pressure of about 30 p.s.i.g., a liquid hourly space velocity of about 32 hr. and a conversion temperature which is continuously selected from the range of about 850 F. to about 950 F. in order to maintain a conversion level of about 10 wt. percent based on disappearance of normal parafiins from the hydrocarbon stream charged thereto.

An eflluent stream is then withdrawn from dehydrogenation zone 10 via line 11 and passed to separating zone 12 wherein a hydrogen-rich gaseous phase separates from a hydrocarbon phase containing unreacted normal paraffin hydrocarbons, normal mono-olefins in the C -C range, and a minor amount of material boiling below C The hydrogen-rich gaseous phase is withdrawn from zone 12 via line 13 and recycled (through compressive means not shown) to dehydrogenation zone 10. In addition, a minor amount of this hydrogen-rich gaseous phase is vented from the system via line 14 in order to maintain pressure control within dehydrogenation zone 10. The hydrocarbon-rich liquid phase from separating zone 12 is withdrawn via line 15 and passed to stripping zone 16.

Stripping zone 16 is typically a conventional fractionation column and is designed to take C hydrocarbons overhead (recovered by means of line 17) and produce a bottom stream containing unreacted normal parafiin hydrocarbons in the C to C range and normal monoolefins in the C -C range. The bottoms stream from stripping zone 16 is passed by means of line 18 to alkylation system 2 as was hereinbefore explained.

Operation of the process in the manner indicated above with the C -C normal paraffin charge is continued for a period of time corresponding to a dehydrogenation catalyst life of about 100 barrels of hydrocarbon charge to the dehydrogenation zone per pound of catalyst contained therein (BPP). Analysis of the results of the run indicate that the dehydrogenation catalyst utilized in zone 10 is deactivating at an average rate of about 0.25 F./ BPP. In addition, the quality and yield of the phenylsubstituted C C normal parafilns recovered via line 6 demonstrates that non-normal paraffins are not being synthesized in any significant amount in the process: that is, the selectivity of the dehydrogenation catalyst for normal mono-olefins in the C C range is maintained at a high level which is substantially greater than 90 percent by weight of the products of the dehydrogenation reaction.

In sharp contrast with the results achieved by the process of the present invention, the performance of a similar process operated with the first charge stock being charged directly to dehydrogenation zone 10 instead of alkylation zone 2, is markedly inferior. In this latter case, which is the process of the prior art, it is estimated that deactivation rate of the dehydrogenation catalyst would be about 1.0 to 2.5 F./BPP or more. Furthermore, the selectivity of the dehydrogenation catalyst would be degraded with attendant build-up of non-normal hydrocarbons in the normal paraffin-containing recycle stream which would be charged to dehydrogenation zone 10.

I claim as my invention:

1. A process for the preparation of an aryl-substituted normal parafiin hydrocarbon using a first charge stock containing a normal parafiin hydrocarbon having about 6 to about 20 carbon atoms and a dehydrogenation catalyst-deactivating cyclic contaminant, and a second charge stock containing an alkylatable aromatic hydrocarbon, the boiling point range of said first charge stock being substantially different from the boiling point range of said second charge stock, said process comprising the steps of:

(a) contacting the first charge stock, the second charge stock, and a hereinafter-obtained stream containing unreacted normal paraflin hydrocarbon and a normal mono-olefin having the same number of carbon atoms as said normal paraffin hydrocarbon, with a liquid alkylation catalyst at conditions sufficient to produce a substantially cyclic contaminant-free efiluent stream containing an aryl-substituted normal parafiin hydrocarbon, unreacted alkylatable aromatic hydro carbon, and unreacted normal parafiin hydrocarbon;

(b) fractionating the effluent stream from step (a) to produce a first fraction containing unreacted normal parafiin hydrocarbon, a second fraction containing unreacted alkylatable aromatic hydrocarbon, and a third fraction containing the aryl-substituted normal parafiin hydrocarbon;

(c) contacting said first fraction and hydrogen with a dehydrogenation catalyst at conditions sufficient to produce an effluent stream containing unreacted normal paraflin hydrocarbon, a normal mono-olefin having the same number of carbon atoms as said normal paraffin hydrocarbon, hydrogen and a minor amount of hydrocarbons boiling below said normal paraffin hydrocarbon;

(d) separating hydrogen and hydrocarbons boiling below said normal paraffin hydrocarbon from the efiluent stream from step (c) to obtain said stream containing unreacted normal parafiin hydrocarbons and the normal mono-olefin;

(e) passing said stream formed in step (d) to step (a);

and,

(f) recovering said third fraction as product.

2. The process of claim 1 wherein said first charge stock contains a mixture of C to C normal paraffin hydrocarbons.

3. The process of claim 1 wherein said alkylatable aromatic hydrocarbon is benzene.

4. The process of claim 1 wherein said cyclic contaminant is an alkyl aromatic hydrorcarbon.

5. The process of claim 1 wherein said cyclic contaminant is an alkyl indane.

6. The process of claim 1 wherein said cyclic contaminant is a polycyclic aromatic hydrocarbon.

7. The process of claim 1 wherein said dehydrogenation cataylst comprises a platinum group component and an alkali component combined with an alumina carrier material.

8. The process of claim 7 wherein a component selected from the group consisting of arsenic, antimony, bismuth, sulfur, selenium, tellurium, and compounds thereof, is combined with said dehydrogenation catalyst.

9. The process of claim 1 wherein said dehydrogenation catalyst is a composite containing alumina, about 0.01 to about 1.5 wt. percent lithium, about 0.05 to about 5.0 wt. percent platinum, and arsenic in an amount of about 0.1 to about 0.8 atoms of arsenic per atom of platinum.

10. The process of claim 1 wherein said second fraction is recycled to step (a).

11. The process of claim 1 wherein said liquid alkylation catalyst comprises hydrogen fluoride.

12. The process of claim 1 wherein said liquid alkylation catalyst comprises sulfuric acid.

14 References Cited UNITED STATES PATENTS 3,413,373 11/1968 Bloch 26067l 3,426,092 2/1969 Carson et a1 260671 DELBERT E. GANTZ, Primary Examiner CURTIS R. DAVIS, Assistant Examiner US. Cl. X.R.