Influence of supports for selective production of 2,5-dimethylfuran via bimetallic copper-cobalt catalyzed 5-hydroxymethylfurfural hydrogenolysis

The hydrogenolysis of carbon–oxygen bonds is an important model reaction in upgrading biomass‐derived furanic compounds to transportation fuels.One of these model reactions,namelyconversion of5‐hydroxymethylfurfural(HMF)to the gasoline additive2,5‐dimethylfuran(DMF),isespecially attractive.In this study,bimetallic Cu‐Co catalysts supported on CeO2,ZrO2,and Al2O3were used for the selective hydrogenolysis of HMF to DMF.The structures of the fresh and usedcatalysts were studied using X‐ray diffraction,the Brunauer‐Emmett‐Teller method,transmissionelectron microscopy,temperature‐programmed reduction by H2,temperature‐programmed desorptionof NH3,and CHNS analysis.The structures were correlated with the catalytic activities.TheCu‐Co/CeO2catalyst produced mainly2,5‐bis(hydroxymethyl)furan via reduction of C=O bonds onlarge Cu particles.The Cu‐Co/Al2O3catalyst gave the best selectivity for DMF,as a result of a combinationof highly dispersed Cu,mixed copper–cobalt oxides,and suitable weak acidic sites.Cu‐Co/ZrO2had low selectivity for DMF and produced a combination of variousover‐hydrogenolysis products,including2,5‐dimethyltetrahydrofuran and5,5‐oxybis(methylene)‐bis(2‐methylfuran),because of the presence of strong acidic sites.The reaction pathways and effectsof various operating parameters,namely temperature,H2pressure,and time,were studied to enableoptimization of the selective conversion of HMF to DMF over the Cu‐Co/Al2O3catalyst.

Production of biomass-derived monomers through catalytic conversion of furfural and hydroxymethylfurfural

The synthesis of biomass-derived monomers has received great attention in recent years,motivated by the depletion of fossil fuels and environmental issues.Moreover,the intrinsic functionality within the biomass or biomass-derived chemicals has great potential to produce new types of monomers containing multiple acid or alcohol groups,thereby leading to materials with novel properties.Given their versatile functional groups and easy production from cellulose/hemicellulose,furfural and hydroxymethylfurfural were regarded as very important biomass-derived platform chemicals through which multiple monomers can be produced via heterogeneous catalysis.In the current review,recent development in heterogeneous catalysis for the production of 6 bio-based monomers,furfuryl alcohol,2,5-bis(hydroxymethyl)furan,2,5-bis-(hydroxymethyl)tetrahydrofuran,1,5-pentanediol,1,6-hexanediol,and 2,5-furandicarboxylic acid,from furfural and hydroxymethylfurfural is reviewed and summarized.The major challenge is how to efficiently and selectively convert specific functional group(s)in furfural and hydroxymethylfurfural during the production of these monomers.Additionally,catalyst stability issues need to be addressed due to necessity of using hot water as reaction medium and high tendency of carbonaceous deposit formation on catalyst surface.The current review mainly focuses on efforts of catalytic site design and modification,including selection of metal/support,use of synergy between metal and support,tuning metal size,use of inverse catalysts,adding catalytic promoters,constructing bimetallic sites,etc.,to realize efficient,selective and stable production of bio-based monomers from furfural and hydroxymethylfurfural.

Oxidation of 2,5‐bis(hydroxymethyl)furan to 2,5‐furandicarboxylic acid catalyzed by carbon nanotube‐supported Pd catalysts

The selective oxidation of 2,5‐bis(hydroxymethyl)furan(BHMF)in this work was proven as a promising route to produce 2,5‐furandicarboxylic acid(FDCA),an emerging bio‐based building‐block with wide application.Under ambient pressure,the modified carbon nanotube‐supported Pd‐based catalysts demonstrate the maximum FDCA yield of 93.0%with a full conversion of BHMF after 60 min at 60°C,much superior to that of the traditional route using 5‐hydroxymethylfurfural(HMF)as substrates(only a yield of 35.7%).The participation of PdH_(x) active species with metallic Pd can be responsible for the encouraging performance.Meanwhile,a possible reaction pathway proceeding through 2,5‐diformylfuran(DFF)and 5‐formyl‐2‐furancarboxylic acid(FFCA)as process intermediates is suggested for BHMF route.The present work may provide new opportunities to synthesize other high value‐added oxygenates by using BHMF as an alternative feedstock.

Phosphorylated mesoporous carbon as effective catalyst for the selective fructose dehydration to HMF

Phosphorylated mesoporous carbons （PMCs） were investigated as catalysts in the dehydration of fructose to hydroxymethylfurfural （HMF）. The acidic PMCs show better selectivity to HMF compared to sulfonated carbon catalyst （SC） despite lower activity. The concentration of P-O groups on the PMC was correlated with the activity/selectivity of the catalysts; the higher the P-O concentration, the higher the activity. However, the higher the P-O content, the lower the selectivity to HME Indeed, a lower concentration of the P-O groups minimized the degradation of HMF to levulinic acid and the formation of by-products, such as humines. Stability tests showed that these systems deactivate due to the formation of humines and water insoluble by-products derived from the dehydration of fructose which blocked the catalytically active sites.