Ruiyan Sun

Synthesis of ethylene glycol and terephthalic acid from biomass for producing PET

There have been considerable efforts to produce renewable polymers from biomass. Poly(ethylene terephthalate) (PET) is one of the most versatile bulk materials used in our daily lives. Recent advances in the new catalytic process for conversion of biomass have allowed us to design more technically effective and cheaper methods for the synthesis of green PET monomers. This review analyses recent advances in the synthesis of PET monomers from biomass. Different routes for ethylene glycol (EG) and purified terephthalic acid (PTA) synthesis are systematically summarized. The advantages and drawbacks of each route are discussed in terms of feedstock, reaction pathway, catalyst, economic evaluation and technology status, trying to provide some state-of-the-art information on green PET monomer synthesis. Finally, an outlook is presented to highlight the challenges, opportunities and on-going trends, which may serve as guidelines for designing novel synthetic routes to green polymers from fundamental science to practical use.

Synthesis of 1,6-hexanediol from HMF over double-layered catalysts of Pd/SiO2 + Ir–ReOx/SiO2 in a fixed-bed reactor

1,6-Hexanediol (1,6-HDO) was effectively prepared from 5-hydroxymethylfurfural (HMF) over double-layered catalysts of Pd/SiO2 + Ir–ReOx/SiO2 in a fixed-bed reactor. Under optimal reaction conditions (373 K, 7.0 MPa H2, in solvent mixtures of 40% water and 60% tetrahydrofuran (THF)), 57.8% yield of 1,6-HDO was obtained. The double-layered catalysts loaded in double-layered beds showed much superior performance compared to that of a single catalyst of Pd–Ir–ReOx/SiO2, even when the same amount of active components were used in the catalysts. The reaction solvent significantly affected product distributions, giving a volcano-shape plot for the 1,6-HDO yield as a function of the ratio of water to THF. Bronsted acidic sites were generated on the catalyst in the presence of water which played determining roles in 1,6-HDO formation. A high pressure of H2 contributed to 1,6-HDO formation by depressing the over-hydrogenolysis of reaction intermediates and products to form hexane and hexanol. The reaction route was proposed for HMF conversion to 1,6-HDO on the basis of conditional experiments.

Catalytic conversion of cellulosic biomass to ethylene glycol: effects of inorganic impurities in biomass.

The effects of typical inorganic impurities on the catalytic conversion of cellulose to ethylene glycol (EG) were investigated, and the mechanism of catalyst deactivation by certain impurities were clarified. It was found that most impurities did not affect the EG yield, but some non-neutral impurities or Ca and Fe ions greatly decreased the EG yield. Conditional experiments and catalyst characterization showed that some impurities changed the pH of the reaction solution and affected the cellulose hydrolysis rate; Ca and Fe cations reacted with tungstate ions and suppressed the retro-aldol condensation. To obtain a high EG yield, the pH of the reaction solution and the concentration of tungstate ions should be respectively adjusted to 5.0-6.0 and higher than 187ppm. For raw biomass conversion, negative effects were eliminated by suitable pretreatments, and high EG yields comparable to those from pure cellulose were obtained.

Production of renewable 1,3-pentadiene from xylitol via formic acid-mediated deoxydehydration and palladium-catalyzed deoxygenation reactions

A two-step synthetic approach for the production of renewable 1,3-pentadiene was reported: xylitol deoxydehydration (DODH) by formic acid to 2,4-pentadien-1-ol, 1-formate (2E), followed by deoxygenation to 1,3-pentadiene over Pd/C. The overall carbon yield of 1,3-pentadiene reached 51.8% under the optimized conditions.