Synthesis of linear phenyldodecanes by the alkylation of benzene with 1-dodecene over non-zeolitic catalysts

Abstract

Linear alkylbenzenes (LAB) are typically manufactured by the alkylation of benzene and α-olefin, employing HF or AlCl₃ as catalyst. LAB are the precursors of linear alkylbenzene sulphonates (LABS) used in a variety of industries. Various acid catalysts are being explored by different researchers, and zeolites are claimed to be effective. The isomer distribution depends strongly on the type and nature of the catalyst and reaction conditions. The liquid-phase alkylation of benzene with 1-dodecene was examined by using several non-zeolites based on clays, pillared clays, and clay-supported heteropolyacids such as dodecatungstophosphoric acid (DTP), dodecatungstosilicic acid (DTS), and dodecamolybdophosphoric acid (DMP). The activities and selectivities of K-10 clay, 20% w/w heteropolyacids (DTP, DMP, and DTS) supported on K-10, Filtrol-24, Al pillared clay, 20% w/w DTP/silica,10% AlCl3/10% FeCl3/K-10, DTP, Cr-exchanged K-10, sulphated zirconia, Zr-exchanged K-10, and 20% DTP/activated carbon were evaluated. It was found that 20% w/w DTP/K-10 clay offered the best conversion with favourable product distribution. A molar ratio of 10:1 benzene/1-dodecene favoured the formation of linear dodecylbenzenes (LAB). However, with decreasing benzene concentration, the formation of didodecylbenzenes increased. The best parameters for the alkylation were established. A mechanistic and kinetic model was developed and validated against experimental data. Benzene alkylation was also accomplished with 1-octene, 1-decene, and 1-tetradecene under otherwise similar sets of conditions. It was found that the rate of benzene alkylation decreased with an increase in the chain length of α-olefin.