Highly active tin(iv) phosphate phase transfer catalysts for the production of lactic acid from triose sugars

Abstract

Lactic acid (LA) is an important intermediate in the fine chemical industry because it is utilized as a building block for the production of biodegradable plastics. In this study, a series of tin phosphate phase transfer catalysts modified with several surfactants have been prepared by a facile one-pot synthesis method and tested for the direct conversion of trioses to LA under hydrothermal conditions. Poly(ethylene glycol) (PEG) was identified as the most promising surfactant, and the product distribution closely depended on the reaction temperature, catalyst loading and substrate concentration. Complete DHA conversion and a good yield of up to 96.1% of LA were obtained at 140°C after 4 h of reaction time. Pyridine FTIR demonstrated the presence of Brønsted and Lewis acid sites, which play crucial roles in the dehydration of DHA to pyruvaldehyde (PA) and the following isomerization of generated PA to LA. Furthermore, the isomerization of PA to LA was found to be the rate-determining step. A possible reaction mechanism was proposed: 1) the coordination between PEG and the metal ions caused a greater separation of the tin ions from the phosphate anions, making them more potent Lewis acid sites, and 2) the PEG behaved as a phase transfer catalyst during the reaction. This study paves the way for the further design of improved solid acid catalysts for aqueous phase production of LA from carbohydrates.Catal. Sci. Technol. This journal is † Electronic supplementary information (ESI) available: Catalytic conversion of GLA to LA by SnP with various surfactants, the results of DHA after a prolonged reaction time of 6 h and the postulated roles of SnP-PEG2000. See

Simple and green route for preparation of tin phosphate catalysts by solid-state grinding for dehydration of glucose to 5-hydroxymethylfurfural (HMF)

“…† The total acidity of the catalyst decreased with increasing the calcination temperature, as similarly reported by another study using tin phosphate catalyst. 41 Similar observation (a higher calcination temperature led to a decrease in the intensity of the Brønsted and Lewis acid sites) was obtained from the pyridine FT-IR measurements to be presented in the subsequent section.…”

The Role of Brønsted and Water‐Tolerant Lewis Acid Sites in the Cascade Aqueous‐Phase Reaction of Triose to Lactic Acid

“…There are only a few studies in the literature that used water as solvent to produce lactic acid, and they focused on the performance of zeolites (Y, USY, ZSM‐5, Beta and Mordenite), substituted zeolites (Zr‐, Ti‐ and Sn‐Beta, and Sn‐MCM‐22), tin phosphates and carbon−silica composites . These authors concluded that the Lewis acid sites can catalyze the formation of lactic acid from trioses and that the catalyst activity was associated with the strength of such sites; the stronger the Lewis acid sites the more active the catalyst …”

Niobium phosphotungstates: excellent solid acid catalysts for the dehydration of fructose to 5-hydroxymethylfurfural under mild conditions

“…With the rapid growth of the world economy, the high dependence on fossil fuels has caused serious environmental problems and requires groundbreaking improvements in clean technology that will take advantage of renewable energy sources. 1,2 Biomass represents an abundant and renewable carbon resource that can be transformed into liquid fuels and value-added chemicals. The catalytic conversion of biomass has been the subject of intense research efforts in recent years.…”