Jiayu Xin

Superbase/cellulose: an environmentally benign catalyst for chemical fixation of carbon dioxide into cyclic carbonates

An environmentally benign catalytic system consisting of 1,8-diazabicyclo[5.4.0]-undec-7-ene (DBU) and cellulose was developed for CO2 chemical fixation with epoxides under metal-free and halide-free conditions. Due to the dual roles played by DBU and cellulose on the activations of CO2 and epoxide, the reaction could be performed with high activity and selectivity. A possible catalytic cycle for the hydrogen bond assisted ring-opening of epoxide and the activation of CO2 induced by DBU was proposed. The process herein represents a simple, ecologically safe and efficient route for CO2 chemical fixation into high value chemicals.

Formation of C–C bonds for the production of bio-alkanes under mild conditions

It is of crucial importance to form C–C bonds between biomass-derived compounds for the production of bio-alkanes from biomass. In this study, it was found that C–C bonds can be formed between angelica lactones, key intermediates derived from biomass, through free radical reactions under mild conditions without using a noble catalyst or solvent, which gave elongated carbon chains of di/trimers with 10 or 15 carbons, with complete conversion and 100% selectivity. The di/trimers produced serve as a novel feedstock for the carbon backbones of bio-alkanes. Hydrogenation of the di/trimers produced C6–C13 hydrocarbons suitable for use as transportation fuels.

Conversion of lignin model compounds under mild conditions in pseudo-homogeneous systems

To produce basic chemicals from lignin, depolymerization and removal of oxygen from lignin through C–O cleavage and hydrodeoxygenation (HDO) are crucial steps. In this study, a novel, pseudo-homogeneous catalyst system, consisting of uniformly stabilized noble metal nanoparticles (NPs) in ionic liquids is developed for the selective reductive cleavage of C–O and HDO. Phenol and guaiacol as lignin monomer model compounds are investigated to gain an insight into the possible HDO pathway, meanwhile, dimeric model compounds such as diphenyl ether and benzyl phenyl ether are studied for the cleavage of C–O bonds between aromatic units. Four types of NPs including Pd, Pt, Rh and Ru were synthesized in situ and well distributed in ILs without aggregation. These catalytic systems displayed almost 100% conversion for various monomeric and dimeric lignin model compounds at 130 °C and were recycled several times without loss of activity. The catalytic selectivity of metals for HDO/C–O cleavage normally decreases in the order of Pt > Rh ∼ Ru ≫ Pd, which is similar to the order of NP size, Pd ≫ Pt > Rh ∼ Ru. With a mean diameter of 5.6 nm, Pt NPs in [Bmim]PF6 are identified as the best catalytic system for the transformation of lignin monomeric and dimeric model compounds with an almost 100% conversion and maximum 97% selectivity.

Conversion of biomass derived valerolactone into high octane number gasoline with an ionic liquid

Conversion of biomass into gasoline of high octane number is challenging. In this study, conversion of biomass-derived γ-valerolactone into gasoline was achieved by decarboxylation of valerolactone to produce butenes and alkylation of the produced butenes with butane using [CF3CH2OH2][CF3CH2OBF3] as an efficient catalyst. The obtained gasoline was rich in trimethylpentane with a high research octane number of 95.4.

A Simple and Mild Approach for the Synthesis of p-Xylene from Bio-Based 2,5-Dimethyfuran by Using Metal Triflates

The production of aromatic platform chemicals from biomass-derived feedstocks is of considerable importance in biomass conversion. However, the development of effective routes with simple steps and under mild conditions is still challenging. In this work, we report an original route for the direct synthesis of p-xylene from 2,5-dimethylfuran and acrylic acid catalyzed by scandium(III) triflate (Sc(OTf)3 ) in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Emim]NTf2 ) under mild conditions. An overall 63 % selectivity towards p-xylene and 78 % selectivity towards aromatics were obtained at 90 % conversion of 2,5-dimethylfuran by enhancing the dehydration and introducing an extra one-pot decarboxylation step. Furthermore, various dienes and dienophiles were employed as reactants to extend the substrate scope. The aromatic compounds were obtained in moderate yields, which proved the potential of the method to be a generic approach for the conversion of bio-based furanics into renewable aromatics.

Fe–Zr–O catalyzed base-free aerobic oxidation of 5-HMF to 2,5-FDCA as a bio-based polyester monomer

An environment-friendly and economical route for 5-hydroxymethylfurfural (HMF) aerobic oxidation to 2,5-furandicarboxylic acid (FDCA) in an ionic liquid (IL)-promoted base-free reaction system was reported using Fe–Zr–O as a catalyst. A series of FexZr1−xO2 catalysts were synthesized by a hydrothermal method and the catalytic performance was investigated. Among these catalysts, Fe0.6Zr0.4O2 exhibited excellent catalytic activity in the HMF oxidation. A 60.6% FDCA yield and 99.9% HMF conversion could be obtained after 24 h under 2 MPa O2 pressure and base-free conditions. The good performance could be attributed to the large amount of acidic and basic sites on the surface of the catalyst and its high reducibility and oxygen mobility. In addition, the formation of humins and the reaction pathways in the ILs were also investigated, which revealed parallel reactions between FDCA and humin formation. A plausible reaction mechanism was proposed based on the results of a series of designed experiments. Finally, the catalyst was used five times without obvious loss of activity. To the best of our knowledge, this is the best result for a non-noble metal catalyzed base-free oxidation of HMF to FDCA using molecular oxygen as an oxidant.

Preparation of 1,4-cyclohexanedimethanol by selective hydrogenation of a waste PET monomer bis(2-hydroxyethylene terephthalate)

A new approach is developed for the preparation of 1,4-cyclohexanedimethanol (CHDM) by hydrogenation of bis(2-hydroxyethylene terephthalate) (BHET) obtained from waste poly(ethylene terephthalate) (PET). The influences of various reaction parameters including temperature, pressure and time, on the hydrogenation reaction were studied, and the 100% conversion of BHET and 78% yield of CHDM were achieved with Pd/C and Cu-based catalysts. X-ray diffraction, low temperature N2 adsorption–desorption and H2 temperature-programmed reduction were used to characterize the Cu-based catalysts, demonstrating that the Cu+/Cu0 species are the active sites. This study not only provides a new route for the production of CHDM, but also an approach for the efficient utilization of waste PET.

Base-free preparation of low molecular weight chitin from crab shell

Low molecular weight (LMW) chitin exhibits antimicrobial activity, and its preparation generally employs high molecular weight chitin as raw material. Here we use raw crab shell as material to isolate LMW-chitin. The raw crab shell was treated with hydrochloric acid under different conditions, and the demineralization and deproteinization of acid to the raw and demineralized crab shell were examined. Under conditions of 3-5 wt% acid, 110 °C, and 180-600 min, the obtained LMW-chitin owns 92% purity and 53-80 kDa molecular weight. The method provides feasible one-step base-free strategy to directly obtain LMW-chitin from raw crab shell, and could be potentially extended to other chitin sources.

Ionic liquids and supercritical carbon dioxide: green and alternative reaction media for chemical processes

Abstract Ionic liquids (ILs) and supercritical CO2 (scCO2) are two promising types of reaction media for green chemical processes due to their unique properties. They can be integrated into chemical reactions as catalysts and solvents to develop green and environment-friendly processes. This review presents current research trends aiming to solve the major chemical engineering issues in light of a fundamental understanding of these media. Applications of these media in the petrochemical industry, biochemical engineering, and fine chemical production are reviewed, suggesting the challenges and directions of utilizing them for green processes prospectively. These recent explorations and successful examples of applications demonstrate that ILs and scCO2 offer huge potential for novel and green chemical engineering processes.

One-step preparation of an antibacterial chitin/Zn composite from shrimp shells using urea-Zn(OAc)2·2H2O aqueous solution

A one-step method is proposed to prepare a chitin/Zn composite from shrimp shells using urea-Zn(OAc)2·2H2O aqueous solution as a decalcification, deproteinization, and Zn-introduction solvent. The chitin/Zn composite, which contained 34.7 wt% zinc, 1.2 wt% calcium carbonate and 1.6 wt% protein, was obtained under optimal conditions and exhibited an antibacterial effect.