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• An efficient and stable SO 4 2−/TiO 2 -SiO 2 catalyst was developed for MMA production. • The Brønsted and Lewis acid site densities and ratios in catalyst can be modulated. • The cooperative catalytic effects between Brønsted and Lewis acid sites were noticed. • The catalytic pathway on such catalyst was confirmed as L-H mechanism. Either the ethylene or isobutene-based route for industrial production of methyl methacrylate (MMA) contains the esterification step between methacrylic acid (MAA) and methanol, therefore it is necessary to develop highly active and stable catalyst. Herein, series of superacid catalysts of SO 4 2-/TiO 2 -SiO 2 were prepared for esterification of MAA with methanol to produce MMA. The Brønsted and Lewis acid site densities and their ratios in SO 4 2-/TiO 2 -SiO 2 could be modulated by controlling the impregnated (NH 4) 2 SO 4 concentration, which were identified by pyridine titration and FT-IR. And no changes in structural skeleton and crystal phase of the SO 4 2-/TiO 2 -SiO 2 during the acid properties regulation process were noticed with FT-IR and XRD. The cooperative catalytic effects between Brønsted and Lewis acid sites were observed through catalytic evaluation. The kinetic studies indicated the catalytic pathway followed L-H mechanism and the activation barrier of forward esterification (48 kJ/mol) was greater than that of reverse hydrolysis (40 kJ/mol) step. [ABSTRACT FROM AUTHOR]

• Series of basic ionic liquids with sterically hindered cations were synthesized. • An ionic liquid catalyzed process for 4-hydroxy-2-butanone synthesis was developed. • The steric hindrance effect on selectivity of product was found and demonstrated. • The catalytic pathways and reaction kinetic were revealed. 4-Hydroxy-2-butanone as important chemical intermediate in the field of both pharmaceutical and food industries is traditionally synthesized from formaldehyde and acetone via aldol reaction with relatively low selectivity due to the heavy side reactions. Herein, series of basic ionic liquids with different sterically hindered cations were prepared for this reaction process. The catalytic performance evaluation results revealed the selectivity of 4-hydroxy-2-butanone could be enhanced with the extension of alkyl chain length substituted in the cation of ionic liquid and increasing number of substituted alkyl group. And the tetraoctyl ammonium hydroxide ([N8,8,8,8]OH) was identified as the optimal ionic liquid catalyst with selectivity of 91.1% toward 4-hydroxy-2-butanone at 40 °C. The kinetic studies indicated the formation of 4-hydroxy-2-butanone was first-order dependent on both acetone and formaldehyde concentrations, with the lowest activation barrier of 49.8 kJ/mol among all steps. [ABSTRACT FROM AUTHOR]