Control of γ-valerolactone selective opening on co-precipitated magnesium silicates

In response to the global imperative for sustainable resources, γ-valerolactone (GVL), derived from levulinic acid found in biomass and food waste, holds particular interest to yield bio-monomers for polymer synthesis. This study investigates the catalytic potential of magnesium silicates in gas-phase GVL ring-opening via transesterification reaction with methanol (methanolysis), producing methyl 2-pentenoate, methyl 3-pentenoate, methyl 4-pentenoate, and butene. The aim of the study is to selectively produce the 3 and 4 isomers due to their utility as nylon precursors. Through systematic adjustments of the catalyst synthesis conditions, including the nature and/or ratios of the precursors as well as the pH levels, the acid-base properties of co-precipitated magnesium silicates are modulated. The materials are prepared in micromixer equipment, and their structural and textural properties are characterized by X-ray diffraction (XRD) and N₂ physisorption, respectively. An in-depth exploration of the products and of the spent catalysts leads to identifying strongly adsorbed carboxylates as responsible for a non-negligible carbon balance gap. Moreover, the surface acid-base characteristics are determined by means of a model reaction of 2-methyl-3-butyn-2-ol (MBOH) conversion and correlated to the selectivity to methyl pentenoates and butene in the methanolysis of GVL. The findings underscore that the least acidic catalyst yields the highest selectivity to the desired products, while the most acidic catalyst favours the production of butene.