Direct Conversion of Cellulose into Ethyl Lactate in Supercritical Ethanol–Water Solutions

Abstract

Biomass-derived ethyl lactate is a green solvent with a growing market as the replacement for petroleum-derived toxic organic solvents. Here we report, for the first time, the production of ethyl lactate directly from cellulose with the mesoporous Zr-SBA-15 silicate catalyst in a supercritical mixture of ethanol and water. The relatively strong Lewis and weak Brønsted acid sites on the catalyst, as well as the surface hydrophobicity, were beneficial to the reaction and led to synergy during consecutive reactions, such as depolymerization, retro-aldol condensation, and esterification. Under the optimum reaction conditions, ∼33 % yield of ethyl lactate was produced from cellulose with the Zr-SBA-15 catalyst at 260 °C in supercritical 95:5 (w/w) ethanol/water.

Catalytic Upgrading of Biomass‐Derived Sugars with Acidic Nanoporous Materials: Structural Role in Carbon‐Chain Length Variation

“…In addition, the relatively strong Lewis acidity, combined with weak Brønsted acidity of a single catalyst, was also crucial for the direct conversion of cellulose into LA/AL in one pot . The weak Brønsted acid sites could promote the hydrolysis of cellulose and dehydration of important intermediates (trioses) for LA/AL formation, while inhibiting the formation of furanic compounds derived from fructose/glucose dehydration, wherein the hydrolysis of cellulose was assumed to be the rate‐determining step during the whole conversion process . As high as 33 % yield of EL was obtained from cellulose in ethanol/water (95/5 v/v) with Zr‐SBA‐15 at 260 °C within 6 h .…”

“…The weak Brønsted acid sites could promote the hydrolysis of cellulose and dehydration of important intermediates (trioses) for LA/AL formation, while inhibiting the formation of furanic compounds derived from fructose/glucose dehydration, wherein the hydrolysis of cellulose was assumed to be the rate‐determining step during the whole conversion process . As high as 33 % yield of EL was obtained from cellulose in ethanol/water (95/5 v/v) with Zr‐SBA‐15 at 260 °C within 6 h . The high EL yield attained resulted from the synergistic effect of the relatively strong Lewis and weak Brønsted acidity of Zr‐SBA‐15, and the presence of water, together with the surface hydrophobicity of Zr‐SBA‐15, facilitated cleavage of the β‐1,4‐glycosidic bond of cellulose.…”

Catalytic Transfer Hydrogenation of Furfural for the Production of Ethyl Levulinate: Interplay of Lewis and Brønsted Acidities

“…Zr-SBA-15 was synthesized according to the procedure described in reference [27] and had been well implemented in our previous articles. [28,29] Briefly, 2 g of Pluronic P123 was added to 75 ml of 1.6 M HCl solution. The mixture was stirred at 40°C for 3 hours until all P123 was dissolved.…”

Chemocatalytic Production of Lactates from Biomass-Derived Sugars

“…In addition, 31.2% ML yield could be also obtained from real biomass sugar cane bagasse at 190°C within 6 h. However, lower yields of ML were achieved from glucose (15.7%) and sucrose (14.7%), may be derived from the strong acidity of SnCl 2 ·2H 2 O-ZnCl 2 which would transform many monosaccharides and disaccharides into dark tars. On the other hand, Zr-SBA-15 heterogeneous catalysts developed by Lin group, could not only exhibit good yields of ML form monosaccharides and disaccharides ( Table 3, Entry 8) [113], but also perform well from cellulose directly in 95% methanol solvent [113] and in 95% ethanol [122], respectively. e addition of a little amount of water (5 wt%) along with the weak Brønsted acids of Zr-SBA-15, was believed to facilitate the hydrolysis of cellulose.…”