Mesoporous methyl-functionalized Sn-silicates generated by the aerosol process for the sustainable production of ethyl lactate

The aerosol-assisted sol–gel process was used to synthesize in a straightforward one-pot procedure a series of methyl-functionalized tin silicates with different degrees of methylation. The successful incorporation of isolated Sn as single site within the silica framework was confirmed via 119Sn solid-state NMR measurements, while 29Si and 13C solid-state magic-angle-spinning NMR experiments revealed a degree of methylation close to the theoretical value, hence proving the efficacy of the adopted cosynthetic approach. These materials were tested as catalysts in the synthesis of ethyl lactate from dihydroxyacetone and ethanol. The methylated solids display enhanced performances in terms of both activity and selectivity compared to the nonmethylated analogues, highlighting a strong beneficial role of surface hydrophobicity. Under proper conditions a total conversion and a selectivity higher than 95% were achieved. Moreover, the efficient separation and reuse of the heterogeneous catalyst as well as the possibility of an easily recover of the reaction solvent result in a very low waste production protocol with an exceptionally low E-factor

Synthesis of highly accessible gallosilicates via impregnation procedure:enhanced catalytic performances in the conversion of glycerol into solketal

Two mesoporous gallosilicates with extra‐small particle size were synthesized via wet impregnation starting from lactate or citrate‐type Ga(III) precursors. The structural and textural properties of the materials were extensively characterized by different techniques. Both materials consist of nanosized particles and display a remarkably high surface area and a pore size distribution typical of mesoporous MCM‐41‐like materials. The two solids were tested as catalysts in acetalization of glycerol with acetone to produce solketal (2,2‐dimethyl‐1,3‐dioxolane‐4‐methanol). Both catalysts displayed excellent performances and achieved higher turnover numbers compared to other Ga‐silicates reported in literature. The outstanding activity of these catalysts is attributed to the combination of acidity, large specific surface area as well as to the full accessibility of the active sites as consequence of the impregnation procedure. The best catalysts are truly heterogeneous with absence of Ga leaching and reusable in successive catalytic cycles after thermal treatment without significant deterioration of the catalytic performance

High-Yield Synthesis of Ethyl Lactate with Mesoporous Tin Silicate Catalysts Prepared by an Aerosol-Assisted Sol-Gel Process

An aerosol-assisted sol–gel method is used to prepare mesoporous tin silicate catalysts that exhibit a record activity in the synthesis of ethyl lactate from dihydroxyacetone and ethanol. The method is based on the formation of an aerosol from a solution of precursors and surfactant. During the fast drying of the droplets, the surfactant self-assembles and the Sn-silica matrix is formed by polycondensation reactions. After calcination, the resulting material is composed of a true tin-silicon mixed oxide in the form of spherical microparticles with calibrated mesopores of 5–6 nm. Sn species are incorporated in the silica network, mainly in the form of single sites. This makes these catalysts highly active for the targeted reaction, as shown by record turnover numbers. The catalyst is recyclable and truly heterogeneous as it can be reused for several cycles and it does not leach

Surface-functionalized mesoporous gallosilicate catalysts for the efficient and sustainable upgrading of glycerol to solketal

Two series of functionalized mesoporous Ga silicates were prepared in a straightforward and sustainable one-pot procedure using different alkyl silanes. The efficacy of the adopted co-synthetic approach based on aerosol processing has been proved by 29Si solid-state NMR experiments revealing a degree of functionalization close to the theoretical value. The successful incorporation of gallium as single sites within the silica framework was confirmed via71Ga solid-state magic-angle-spinning NMR measurements. These materials were tested as catalysts for the synthesis of solketal from glycerol at low temperature and under solventless conditions. A systematic study evidenced the importance of a careful tuning of surface polarity, achievable with surface functionalization as well as with different thermal treatments. The solids functionalized with a low degree of methyl groups (5%) displayed enhanced performances compared to the non-functionalized analogues, highlighting the highly beneficial role of surface hydrophobicity as well as the importance of the careful tuning of the hydrophilic/hydrophobic balance. The best functionalized catalysts proved to be easily reusable for multiple catalytic runs. With such a high-performance catalyst in hand, we propose a process which shows a favorable E-factor, indicating that the production of solketal can be envisaged in a sustainable way