A 3D MIL-101@rGO composite as catalyst for efficient conversion of straw cellulose into valuable organic acid

Efficient conversion of straw cellulose to chemicals or fuels is an attracting topic today for the utiliza-tion of biomass to substitute for fossil resources.The development of catalysts is of vital importance.In this work,a composite catalyst metal-organic frameworks(MOFs)immobilized on three-dimensional reduced graphene oxide(3D-rGO)were synthesized by in situ growth of the MIL-101(Cr)within the 3D-rGO matrix.The supporting of 3D-rGO guaranteed the dispersion and acid site density of MIL-101(Cr).The MIL-101(Cr)@3D-rGO nanocomposite possesses excellent catalytic activity,stability,recyclability and is an idea catalyst for the efficient degradation of straw cellulose into formic acid(FA),acetic acid(AA)and oxalic acid(OA).A maximum FA conversion rates of 95.36%was obtained by using MIL-101(Cr)@3D-rGO(1:1)as catalyst and hydrothermal reaction at mild conditions of 200°C for 1h in alkaline aqueous medium.The MIL-101(Cr)@3D-rGO nanocomposite can be reused with high catalytic activity without any collapse of structure or leaching of chromium.

Extraction,separation and refining of microcrystalline cellulose from wheat straw using various pretreatments

This study focused on the manufacture of microcrystalline cellulose(MCC)from wheat straw using environmentally-friendly solvents.Raw cellulose was separated from wheat straw after thermal decomposition of lignin followed by dissolution of lignin using a recyclable ethanol/acetic acid/water solvent system.Then,pure cellulose was produced using a four-step refining process,including chelating,O_(3),H_(2)O_(2),and xylanase treatments.Finally,MCC was obtained through hydrolysis,drying,and mechanical treatments.The effects of acetic acid,O_(3),H_(2)O_(2),NaOH,pretreatment time,and temperature on the properties of wheat straw cellulose(including Kappa number,yield,α-cellulose content,crystallinity,KMnO4 value,degree of polymerization(DP),and brightness)were investigated.The results showed that the addition of acetic acid enhanced lignin removal and hemicellulose degradation,improving the purity of the raw cellulose.The optimized acetic acid dosage in the wheat straw thermal decomposition step was 2%(w/w).The optimized O_(3)dosage was 1.2%(w/w).The optimized conditions for H_(2)O_(2)treatment were found to be 3%(w/w)H_(2)O_(2)and 1.8%(w/w)NaOH at 70°C for 120 min.The KMnO4 value was 2.0,brightness was 84.1%ISO,the viscosity was 934 mL/g,and the DP was 626 for refined cellulose.Xylanase effectively improved theα-cellulose content of wheat straw cellulose.With an optimized xylanase dosage of 1.5 IU/g,theα-cellulose content was 94.7%,the brightness was 85.6%ISO,and the DP was 615 for wheat straw cellulose.