Alkylation of Xylenes with Isopropyl Alcohol over Acidic Clay Supported Catalysts: Efficacy of 20% w/w Cs_2.5H_0.5PW₁₂O₄₀/K-10 Clay

Abstract

The alkylation of xylenes with propylene or isopropyl alcohol (IPA) over solid acid catalysts results in the formation of isopropyl xylenes (dimethyl cumenes). However, the use of propylene as an alkylating agent at very high temperatures leads to coke formation, which results in deactivation of the catalyst. The present work covers evaluation of acidic clay-supported catalysts and sulfated zirconia. A variety of solid acid catalysts such as K-10 clay, sulfated zirconia, Filtrol-24, 20% w/w dodecatungstophosphoric acid (H 3 PW 12 O 40 , DTP) supported on K-10 clay, and 20% w/w cesium-substituted dodecatungstophosphoric acid (Cs 2.5 H 0.5 PW 12 O 40 , Cs-DTP) supported on K-10 clay under much milder conditions. The best catalyst to achieve maximum conversion and selectivity was determined to be 20% w/w Cs-DTP/K-10 clay. The reactions were conducted in the liquid phase at relatively low reaction temperatures (160-190 °C). The reaction was performed without using any solvent, and the process subscribes to the principles of green chemistry. The catalytic activity has the following order: 20% w/w Cs-DTP/K-10 clay (most active) > 20% w/w DTP/K-10 clay > Filtrol-24 > sulfated zirconia > K-10 clay (least active). The desired product could be efficiently obtained, with selectivities up to 95% at an isopropanol conversion of 98% after 2 h over 20% w/w Cs-DTP/K-10 clay. This process can be a replacement for the existing processes that are based on zeolites, where high temperature and pressure are required. A systematic investigation of the effects of various operating parameters was accomplished and a mathematical model is developed to describe the reaction pathway and validated against experimental results. An overall second-order kinetic equation was used to fit the data, under the assumption that all the species are weakly adsorbed on the catalytic sites.

Iron-substituted cubic silsesquioxane pillared clays: Synthesis, characterization and acid catalytic activity

“…Acid activation of clays is performed to enhance their catalytic activity [68]; after the treatment with surfactants in order to modify the clay's surface area the conversion of isopropanol is 5.29% at 120°C [69]. After acid activation the conversion percentage can instead reach 50% at 180°C, as reported by Yavad et al [70]. As shown by Trombetta et al [71], in the case of acid pillared clays the conversion percentage can reach 49.4% -a value that is lower than what we report for our catalysts.…”

Catalysts, Supported

“…The strong Br€ onsted and Lewis acid sites catalyze the dehydration of isopropanol to propene and diisopropyl ether. The use of partially Cs-substituted heteropolyacids relates to an increased hydrothermal stability (41). The alkylation of phenols, cresols, or xylenols with olefins, alcohols, and halogenated hydrocarbons are commercially important reactions.…”

Highly efficient synthesis of cumene via benzene isopropylation over nano-sized beta zeolite in a submerged ceramic membrane reactor

“…To develop a novel and green catalyst, numerous efforts have been made in the last decades, and the beta zeolite catalyst attracts great attention because of its unique structure, thermal stability, acidity and shape-selective property [3][4][5][6]. With regard to the alkylating agent, the use of propylene for producing cumene results in coke formation and catalyst deactivation [7][8][9]. Alternatively, the isopropanol-based method with low coke formation is cost-effective and easy to operate [9].…”

“…With regard to the alkylating agent, the use of propylene for producing cumene results in coke formation and catalyst deactivation [7][8][9]. Alternatively, the isopropanol-based method with low coke formation is cost-effective and easy to operate [9]. Recently, the isopropylation of benzene over beta zeolite using isopropanol as an alkylating agent is becoming preferable to producing cumene [5].…”