Alkylation of Benzene with Dodecene-1 Catalyzed by Supported Silicotungstic Acid Raynor T. Sebulsky’ and Alfred M. Henke Gulf Research & Development Co., P. 0. Drawer 2038, Pittsburgh, Pa. 15230 A bench-scale study evaluated supported silicotungstic acid as a catalyst for the alkylation of benzene with dodecene-1. Silica gel was found superior to alumina and silicaalumina as the support. Sulfonated alkylate made using this catalyst i s equivalent to other linear alkylbenzene sulfonates in detergency and biodegradability. Data were obtained on the effects of process variables on the alkylation reaction. Control of selectivity depends largely on the ratio of benzene to dodecene-1 in the feed; selectivities of 90 to 94% to phenyldodecane are readily achievable. A model based on secondorder kinetics can be used to predict the effects of temperature, mole ratio, catalyst composition, and space time on conversion and selectivity.
A l k y l a t i o n of benzene with linear cI2 olefins is ofparticular interest because the resulting alkylate is used as raw material for a biodegradable or “soft” detergent, linear alkylbenzenesulfonate (LAS). A variety of acidic catalysts has been employed for this reaction, either in the laboratory or in commercial operations. Olson (1960) used aluminum chloride, hydrogen fluoride, and sulfuric acid in studying how the catalyst affected the distribution of phenyldodecane isomers. Where the reaction has been carried out on a commercial scale, processes based on aluminum chloride (Hatch, 1964) or hydrogen fluoride (Canadian Chemical Processing, 1963) have been chosen. An alkylation process that employs a fixed bed of a stable, nonsludging, solid catalyst has advantages. Cumene, for example, is widely manufactured from benzene and propylene in a fixed-bed process that employs phosphoric acid on kieselguhr as catalyst. Unfortunately, phosphoric acid is known to be too low in activity for preparing detergent alkylates from benzene and propylene tetramer (Hervert and Bloch, 1952), and our laboratory Confirmed that it has similarly low activity for alkylating benzene with the linear dodecene-1. Verstappen and Waterman (1935) found that for a very similar carbonium ion reaction, the polymerization of propylene to low molecular weight oligomers, silicotungstic acid (12-tungstosilicic acid) was a far more active catalyst than phosphoric acid on kieselguhr. This high activity of silicotungstic acid for olefin polymerization made it an interesting catalyst candidate for alkylating an aromatic ring with an olefin. Furthermore, the physical properties of silicotungstic acid are nicely suited for preparing a supported catalyst for hydrocarbon reactions. I t is a crystalline solid, very soluble in water, but insoluble in nonpolar compounds like benzene. The high water solubility makes impregnation of supports easy; while hydrocarbon insolubility prevents loss of active material from the catalyst in use. In their studies, Verstappen and Waterman found that I
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To whom correspondence should be addressed Ind. Eng. Chem. Process Des. Develop., Vol. 10, No. 2, 1971
selection of support was very important. Bauxite and low surface area aluminas gave them the best results; silica gel resulted in poor activity. Vol’pova and Ogloblina (1963) confirmed that the choice of supporting material for silicotungstic acid was critical in another study of propylene polymerization. I n this case, the use of a silicaalumina support resulted in the most active catalyst; intermediate activities were obtained with various natural clays; while poor activity was obtained with an alumina support. The present bench-scale study evaluated supported silicotungstic acid as a catalyst for alkylating benzene with dodecene-1. Tests were conducted with a series of supports to select one suitable for this reaction. The phenyldodecane product was evaluated as raw material for a biodegradable detergent. Data were also obtained on the effects of process variables on the alkylation reaction. These data were correlated in terms of a kinetic model of the process. Experimental
Chemicals. Baker Analyzed reagent-grade benzene was used without further purification. The properties of the Gulf dodecene-1 employed are shown in Table I. This was a sample from pilot-plant operation which was similar to the present commercial a-olefin product but contained slightly more Cloand CI4a-olefins. Catalysts. Sylvania silicotungstic acid was used to prepare the catalysts. Supports were impregnated with aqueous solutions of the acid using the incipient wetness technique. After impregnation the catalysts were dried a t 250”F and calcined overnight a t 600”F . Catalyst compositions are reported here as weight percent of anhydrous acid, H4SiW12040.Verstappen’s data indicate that this is the stable composition upon drying between 350” and 750°F. The supports used included two aluminas (Hawshaw A1 1706 and A1 1906), a silica-alumina (Socony Sorbead W ) , and a silica gel (Davison Grade 70). Procedure. Figure 1 is a schematic flow diagram of the experimental equipment. Benzene and dodecene-1 were first blended in the desired ratio, then pumped by a Lapp
Table I. Physical Properties and Analysis of Dodecene-1 Used for Alkylation of Benzene with Dodecene Color, D 156 FIA, D 1319 Saturates: % by vol Olefins: % by vol Saturates, GLC: Crc by wt Density a t 20n C, D 941 Refractive index at 20" C Peroxide number Water, ppm Carbon number distnbution: nc by wt Cl" C 12 C14 Infrared analysis: mol 5: tram R C H = C H R CLS RCH=CHR RCH=CH, R,C=CH, RzC=CHR
1
31 1.7 98.3 2.6 0.7585 1.42984
