Browsing by Author "Lorenzo-Ibarreta, Leire"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item Isosorbide bis(methyl carbonate) synthesis from isosorbide and dimethyl carbonate: the key role of dual basic–nucleophilic catalysts: The key role of dual basic-nucleophilic catalysts(2020-05-18) Ochoa-Gómez, José R.; Lorenzo-Ibarreta, Leire; Diñeiro-García, Cristina; Gómez-Jiménez-Aberasturi, Olga; Tecnalia Research & Innovation; BIOECONOMÍA Y CO2; VALORIZACIÓN DE RESIDUOSIsosorbide bis(methyl carbonate) (IBMC) is a scarcely studied green chemical with potential applications in the manufacturing of non-isocyanate polyurethanes and bisphenol A-free polycarbonates. Its synthesis by transesterification of isosorbide with dimethyl carbonate (DMC) is very negatively influenced by the presence of small amounts of acidic impurities in isosorbide when heterogeneous inorganic carbonates such as potassium and cesium carbonates are used as catalysts. In this paper it is shown that the problem can be solved by using homogeneous catalysts consisting of nitrogenated bases and superbases having a suitable dual nucleophilic–basic character and able to form a highly reactive acyl intermediate with the electrophilic reactant DMC. Cycloaliphatic secondary and tertiary amines, guanidines and amidines covering a nucleophilicity parameter (N) range between 13.58 and 20.58 in either acetonitrile or dichloromethane, and a pKa range in acetonitrile between 15.68 and 26.02 have been tested in batchwise mode. Highly active catalysts leading to hydroxyl conversions of 84–93% require a minimum N of 16 and a pKa ranging from 18.0 to 26.0. Within this pKa range, N must increase by about 0.5–0.6 units per each unit the pKa falls to keep the catalytic activity, indicating that nucleophilicity has approximately twice as much influence as basicity on the catalytic activity. One guanidine (TBD), one amidine (DBN) and three cycloaliphatic secondary amines (N-methylpyrrolidine, quinuclidine and DABCO) have been found to be excellent catalysts at 5 mol% vs. ISO. The side reaction leading to oligomer formation is not avoided, with oligomers, mainly the dimer, affording 6 wt% of the crude product independently of hydroxyl-conversion and catalyst type.Item Synthesis of glycerol carbonate from glycerol and dimethyl carbonate by transesterification: Catalyst screening and reaction optimization(2009-09-25) Ochoa-Gómez, José R.; Gómez-Jiménez-Aberasturi, Olga; Maestro-Madurga, Belén; Pesquera-Rodríguez, Amaia; Ramírez-López, Camilo; Lorenzo-Ibarreta, Leire; Torrecilla-Soria, Jesús; Villarán-Velasco, María C.; BIOECONOMÍA Y CO2; Centros PRE-FUSION TECNALIA - (FORMER); SG; Alimentación SostenibleThe synthesis of glycerol carbonate from glycerol and dimethyl carbonate by transesterification is reported. Firstly, a catalyst screening has been performed by studying the influence of different basic and acid homogeneous and heterogeneous catalysts on reaction results. Catalytic activity is extremely low for acidic catalysts indicating that reaction rate is very slow. On the contrary, high conversions and yields are obtained for basic catalysts. Catalytic activity increases with catalyst basic strength. The best heterogeneous catalyst is CaO. Calcination of CaO increases dramatically its activity due to calcium hydroxide removal from its surface. A reaction optimization study has been carried out with CaO as catalyst by using a factorial design of experiments leading to operation conditions for achieving a 100% conversion and a >95% yield at 1.5 h reaction time: 95 °C, catalyst/glycerol molar ratio = 0.06 and dimethyl carbonate/glycerol molar ratio = 3.5. Carbonate glycerol can be easily isolated by filtering the catalyst out and evaporating the filtrate at vacuum. Leaching of catalyst in reaction medium was lower than 0.34%. Catalyst recycling leads to a quick decrease in both conversions and yields probably due to a combination of catalyst deactivation by CaO exposure to air between catalytic runs, and a decrease in the catalyst surface area available for reaction due to particle agglomeration.