Synthesis of cyclic carbonate from allyl glycidyl ether and carbon dioxide using ionic liquid-functionalized amorphous silica Hye-Lim Shim, Seshachalam Udayakumar, Jeong-In Yu, Il Kim, Dae-Won Park * Division of Chemical Engineering, Pusan National University, Jangeon-dong, Kumjeong-gu, Busan 609-735, South Korea 1. Introduction Carbon dioxide is recognized to be a naturally abundant, cheap, recyclable, and non-toxic source of carbon that can sometimes replace toxic chemicals such as phosgene, isocyanates, and carbon monoxide [1–4]. Under these circumstances, chemical fixation of CO 2 becomes more important from both an ecological and an economic point of view. Among them, the application of carbon dioxide as a monomer for the synthesis of various polymers has received much attention in recent years. The reactions of carbon dioxide with oxiranes leading to five-membered cyclic carbonates are well-known examples. These cyclic carbonates can be widely used for various purposes, such as aprotic polar solvents, electrolytes for batteries and sources for reactive polymer synthesis [5]. The five-membered ring cyclic carbonates (1,3-dioxolan-2- ones) are generally incapable of ring opening polymerization due to their thermodynamic stability, but do undergo polymerization with partial loss of CO 2 to yield macromolecules with both ether and carbonate linkages. Due to such uses, a number of syntheses of cyclic carbonates and polycarbonates have been described over the last 30 years [1,6–12]. Many catalytic systems [13–15] were developed for the insertion of carbon dioxide into oxiranes, such as alkali metal salts [16], alkali metal salts combined with crown ethers or quaternary ammonium salts [17], organoantimony halides [18], MgO [19] or Mg–Al mixed oxides [20], ionic liquids [21], porphyrin [22], transition-metal complexes [23], phthalocyanine [24], poly- oxometalate [25], supercritical carbon dioxide [26], amorphous silica immobilized ionic liquid/ZnCl 2 [27], amine-functionalized mesoporous Ti(Al)-SBA-15 [28], and as-made MCM-41 [29]. However, the processing of homogeneous system limits their application to the catalyst, these catalysts are mainly suffering for separation, reusability and less cost effective process, hence moving to heterogeneous conditions can overcome those pro- blems, but negative sides of these catalysts are low catalytic activity and/or selectivity, low stability, and requiring high pressure. Therefore, the development of a highly efficient solid catalyst system for the chemical fixation of carbon dioxide under mild conditions remains a challenge. The use of ionic liquids as environmentally benign media for catalytic processes or chemical extraction has become widely recognized and accepted [30]. Ionic liquids have negligible vapor pressure, excellent thermal stability and special characteristics in comparison with conventional organic and inorganic solvents. Many reactions catalyzed with ionic liquids and showing high performance have been reported [31,32]. In particular, ionic liquids based on imidazolium cations and chloroaluminate anions, such as 1-butyl-3-methylimidazolium aluminium chloride ([BMIm]Cl/ AlCl 3 ), have attracted growing interest [33,34]. In our previous work [35], the immobilization of ionic liquids onto MCM-41 showed excellent activities for carbon dioxide insertion reactions, however, the use of expensive pore-directing agents and large amounts of organic solvents to remove the Catalysis Today 148 (2009) 350–354 ARTICLE INFO Article history: Available online 21 July 2009 Keywords: Allyl glycidyl ether Carbon dioxide Cyclic carbonate Amorphous silica ABSTRACT Ionic liquid functionalized mesoporous silica (IFMS) was prepared from the coupling of 1- (triethoxysilylpropyl)-3-n-alkylimidazolium halides with tetraethyl orthosilicate (TEOS) through template-free condensation under strong acidic conditions. The immobilized ionic liquid (IM-IL) catalysts showed 0.61–0.93 mmol of ionic liquid on SiO 2 and surface area in the range of 189–647 m 2 /g with pore sizes from 3.2 to 4.2 nm. Elemental analysis and SEM image showed that the immobilized ionic liquid groups were well incorporated on the support. The silica-supported ionic liquids were proved to be an effective heterogeneous catalyst for the solventless synthesis of cyclic carbonate from allyl glycidyl ether (AGE) and carbon dioxide. Im-IL of longer alkyl chain length and more nucleophilic nature showed higher conversion of AGE. High temperature, high carbon dioxide pressure, and the presence of ZnBr 2 co- catalyst were favorable for the conversion of AGE. Im-IL can be reused for the reaction up to three consecutive runs without any considerable loss of its catalytic activity. ß 2009 Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +82 51 510 2399; fax: +82 51 512 8563. E-mail address: dwpark@pusan.ac.kr (D.-W. Park). Contents lists available at ScienceDirect Catalysis Today journal homepage: www.elsevier.com/locate/cattod 0920-5861/$ – see front matter ß 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.cattod.2009.06.011