Titanium Phosphate Grafted on Mesoporous SBA-15 Silica as a Solid Acid Catalyst for the Synthesis of 5-Hydroxymethylfurfural from Glucose

Abstract

The grafting of titania on SBA-15 followed by its phosphation was presented to prepare a mesoporous Lewis−Brønsted bifunctional solid acid catalyst for the tandem conversion of glucose via fructose to 5-hydroxymethylfurfural (HMF). Titania was dispersed on SBA-15 as an amorphous surface layer containing abundant coordinatively unsaturated tetrahedral Ti ions, which was reactive and readily transformed upon phosphation into a new titanium phosphate phase with the chemical formula identified as Ti 2 O 3 (H 2 PO 4 ) 2 •2H 2 O. The ordered mesoporous structure was well maintained after three modification cycles, affording a desirable surface area of over 300 m 2 /g. The SBA-15supported titanium phosphate layer affords higher overall acidity and Brønsted to Lewis acid ratio, compared with the conventional post-phosphated bulk anatase titania. The tetrahedral Ti ions and the adjacent protonated phosphate groups on the titanium phosphate layer could form Lewis−Brønsted acid pairs at molecular level proximity, which largely enhanced the selective tandem catalysis for glucose conversion via fructose to HMF. An optimized HMF yield of 71% was achieved at 160 °C in a water−methyltetrahydrofuran biphasic system over the SBA-15-supported titanium phosphate catalyst. The catalyst exhibited good hydrothermal stability with a rather limited silicon and phosphate leaching, and no distinct pore collapse or performance loss over three sequential reaction runs.

Insights into the reaction network and kinetics of xylose conversion over combined Lewis/Brønsted acid catalysts in a flow microreactor

“…After heating-up, the density of the aqueous phase decreased so that its volumetric flow rate at the reaction temperature T (Q aq ) differs from its initial value at ca. 20 °C (Q aq,0 ), and is corrected as (17) where α mono, aq (ranging from 1.06 to 1.14 within 120-180 °C) is the ratio of the densities of the aqueous phase at 20 ᵒC and T, and can be estimated as a function of T (in ᵒC) 29 (18) 0.007 mono, aq 0.921 0.062…”

“…14 Heterogeneous catalysis is usually preferred due to the ease of catalyst separation and reuse, and solid acid catalysts have received significant attentions for the synthesis of furanics from C5/C6 sugars. [14][15][16][17][18] However, issues still need to be addressed such as the poor hydrothermal stability of solid acid catalysts, long reaction time (> 1 h), and the need for frequent regeneration due to the humin deposition. 14,15 Consequently, a green and efficient homogeneous catalytic system and process are still attractive for (scaled-up) furfural production.…”

Promoted Production of Lactic Acid from Glucose by Calcium Hydroxide in the Presence of Hydrogen

“…As one of the main substances in the hydrolysis products of cellulosic biomass, glucose has a wide application in biological fermentation, food, chemicals and pharmaceutical industry. In addition, glucose is also used to create some valuable chemicals such as fructose, 5‐hydroxymethylfurfural and lactic acid, wherein lactic acid is one of the three recognized organic acids in the world and can be served as an important platform compound [1–7] . It is worth mentioning that lactic acid is mainly employed to produce polylactic acid, which is a typical biodegradable material and can effectively alleviate the global white waste problem arising from the refractory plastics [8–10] .…”

Theoretical Insight into the Mediation Mechanism of Water on Favorable Isomerization over Epimerization of Glucose on the Nb2O5 Catalyst

“…Recently, research efforts have been focused on the development of catalysts for the selective isomerization/epimerization of glucose, including both basic and Lewis acidic catalysts . In particular, water-tolerant Lewis acidic catalysts have attracted great attention, e.g., Sn-, , Zr-, Ti-, Cr-, Mo-, and Nb-containing catalysts . Pioneeringly, Sn-Beta zeolite facilitates the glucose-to-mannose epimerization in methanol solution, whereas it favors the glucose-to-fructose isomerization in aqueous solution .…”