Metal-Free Synthesis of HMF from Glucose Using the Supercritical CO2–Subcritical H2O–Isopropanol System

Catalytic Transformation of Carbohydrates into Renewable Organic Chemicals by Revering the Principles of Green Chemistry

Adherence to the principles of green chemistry in a biorefinery setting ensures energy efficiency, reduces the consumption of materials, simplifies reactor design, and rationalizes the process parameters for synthesizing affordable organic chemicals of desired functional efficacy and ingrained sustainability. The green chemistry metrics facilitate assessing the relative merits and demerits of alternative synthetic pathways for the targeted product(s). This work elaborates on how green chemistry has emerged as a transformative framework and inspired innovations toward the catalytic conversion of biomass-derived carbohydrates into fuels, chemicals, and synthetic polymers. Specific discussions have been incorporated on the judicious selection of feedstock, reaction parameters, reagents (stoichiometric or catalytic), and other synthetic auxiliaries to obtain the targeted product(s) in desired selectivity and yield. The prospects of a carbohydrate-centric biorefinery have been emphasized and research avenues have been proposed to eliminate the remaining roadblocks. The analyses presented in this review will steer to developing superior synthetic strategies and processes for envisaging a sustainable bioeconomy centered on biomass-derived carbohydrates.

Sulfonic acid functionalized β zeolite as efficient bifunctional solid acid catalysts for the synthesis of 5-hydroxymethylfurfural from cellulose

Introduction of the sulfonic acid group into H-β zeolite to prepare β-SO₃H bifunctional catalysts for the efficient synthesis of 5-hydroxymethylfurfural (HMF) from cellulose. Catalysts characterization, such as XRD, ICP-OES, SEM (Mapping), FTIR, XPS, N₂ adsorption-desorption isotherm, NH₃-TPD, Py-FTIR demonstrate the sulfonic acid group was successfully grafted onto the β zeolite. A superior HMF yield (59.4 %) and cellulose conversion (89.4 %) was obtained in the H₂O(NaCl)/THF biphasic system under 200 °C for 3 h with β-SO₃H(3) zeolite as catalyst. More valuable, β-SO₃H(3) zeolite converts other sugars and obtains ideal HMF yield, including fructose (95.5 %), glucose (86.5 %), sucrose (76.8 %), maltose (71.5 %), cellobiose (67.0 %), starch (68.1 %), glucan (64.4 %) and also converts plant material (25.1 % for moso bamboo and 18.7 % for wheat straw) with great HMF yield. β-SO₃H(3) zeolite catalyst keeps an appreciable recyclability after 5 cycles. Moreover, in the presence of β-SO₃H(3) zeolite catalyst, the by-products during the production of HMF from cellulose were detected, and the possible conversion pathway of cellulose to HMF was proposed. The β-SO₃H bifunctional catalyst has excellent potential for the biorefinery of high value platform compound from carbohydrates.

Fructose Transformation into 5-Hydroxymethylfurfural over Natural Transcarpathian Zeolites

Based on Transcarpathian zeolite the catalysts in calcium-lanthanum-ammonium form were synthesized and modified by steaming and dealumination with ethylenediaminetetraacetic acid. The samples were characterized by using nitrogen adsorption/desorption, XRD, XRF, and FTIR-spectroscopy. The yield of 5 hydroxymethylfurfural over modified samples at 433 K was found to be 50 and 83% at a practically full conversion of fructose.