Zhibao Huo

Highly efficient and autocatalytic H 2 O dissociation for CO 2 reduction into formic acid with zinc

Artificial photosynthesis, specifically H2O dissociation for CO2 reduction with solar energy, is regarded as one of the most promising methods for sustainable energy and utilisation of environmental resources. However, a highly efficient conversion still remains extremely challenging. The hydrogenation of CO2 is regarded as the most commercially feasible method, but this method requires either exotic catalysts or high-purity hydrogen and hydrogen storage, which are regarded as an energy-intensive process. Here we report a highly efficient method of H2O dissociation for reducing CO2 into chemicals with Zn powder that produces formic acid with a high yield of approximately 80%, and this reaction is revealed for the first time as an autocatalytic process in which an active intermediate, ZnH− complex, serves as the active hydrogen. The proposed process can assist in developing a new concept for improving artificial photosynthetic efficiency by coupling geochemistry, specifically the metal-based reduction of H2O and CO2, with solar-driven thermochemistry for reducing metal oxide into metal.

Production of 2,5-hexanedione and 3-methyl-2-cyclopenten-1-one from 5-hydroxymethylfurfural

A novel approach for the production of 2,5-hexanedione (HDN) and 3-methyl-2-cyclopenten-1-one (3-MCO) from 5-hydroxymethylfurfural (HMF) by water splitting with Zn is reported for the first time. The use of high temperature water (HTW) conditions is the key for the efficient conversion of HMF to HDN and 3-MCO. Parameters regarding the Zn amount, temperature and reaction time are optimized and HDN and 3-MCO are produced in 27.3% and 30.5% yields, respectively. The roles of HTW and ZnO obtained by oxidation of Zn in water for the conversion of HMF, together with intermediate structures, are discussed to understand the mechanism of the reaction.

A nanoporous nickel catalyst for selective hydrogenation of carbonates into formic acid in water

An efficient unsupported nanoporous nickel (NiNPore) material for the hydrogenation of carbonates to formic acid (FA) in water was investigated for the first time. NiNPore is an environmentally benign catalyst and it exhibited remarkable catalytic activity in the reduction of a wide range of carbonates to afford formic acid in excellent yields with high selectivity, and maximum values of 86.6% from NaHCO3 and even up to 92.1% from KHCO3 were obtained. The hydrogen pressure and pKa of the carbonates had a significant influence on the formation of FA. The catalyst was easily recovered and could be recycled at least five times without leaching and loss of activity. The present study demonstrated a potential application for the synthesis of FA from CO2 or carbonate compounds.

Selective hydrogenation of levulinate esters to 1,4-pentanediol using a ternary skeletal CuAlZn catalyst

A non-noble ternary skeletal CuAlZn catalyst was designed for direct hydrogenation of ethyl levulinate (EL) to 1,4-pentanediol (1,4-PDO). 98% yield of 1,4-PDO, which is the highest yield achieved by heterogeneous catalysts so far, was obtained over CuAlZn-3.5 h. Zn in the skeletal alloy was found as a vital promoter for adjusting the selectivity of 1,4-PDO production.

Improved two-step hydrothermal process for acetic acid production from carbohydrate biomass

An improved two-step process for converting carbohydrate biomass to acetic acid under hydrothermal conditions is proposed. The first step consists of the production of lactic acid from carbohydrate biomass, and the second step consists of conversion of the lactic acid obtained in the first step to acetic acid using CuO as an oxidant. The results indicated that CuO as an oxidant in the second step can significantly improve the production of high-purity acetic acid from lactic acid, and the maximum yield of acetic acid was 61%, with a purity of 90%. The yield of acetic acid obtained using the improved two-step hydrothermal process from carbohydrate biomass, such as glucose, cellulose and starch, was greater than that obtained using traditional two-step process with H2O2 or O2. In addition, a proposed pathway for the production of acetic acid from lactic acid in the second step with CuO was also discussed. The present study provides a useful two-step process for the production of acetic acid from carbohydrate biomass.

A novel Pd/C-catalyzed conversion of glucose to 1,2-propanediol by water splitting with Zn

A novel Pd/C-catalysed conversion of glucose to 1,2-propanediol by water splitting with Zn was proposed. The yield of 1,2-akanediols reached 48%, mainly including 1,2-propanediol (33.3%), the reported highest yield from glucose. Water, as a solvent, provides an in situ and active hydrogen source. The formed ZnO acts as a catalyst with Pd/C.

Chemoselective synthesis of propionic acid from biomass and lactic acid over a cobalt catalyst in aqueous media

A new non-fermentative process for the transformation of biomass carbohydrates and lactic acid (LA) into propionic acid (PA) was first reported over a cobalt catalyst in water. The Co catalyst exhibited high catalytic activity for the formation of PA with Zn as a reductant. Various parameters, such as catalyst loading, Zn weight, water volume, temperature and reaction time, were investigated to improve the yield of PA, and the maximum value of 58.8% was achieved in the presence of 4 mmol Co and 10 mmol Zn in 7.5 mL H2O at 250 °C for 2 h. The recyclability of the Co catalyst showed that Co could be effectively repeated four times without the loss of activity. Moreover, the result showed that in situ-formed ZnO by oxidation of Zn in water could efficiently enhance the catalytic activity of the Co catalyst in the conversion of LA. Besides, direct conversion of carbohydrate biomass, such as glucose, cellulose and starch, or a similar compound such as glycolic acid also afforded the desired products. The present study provides great significance for practical application on the production of PA from LA and biomass carbohydrates.

Efficient conversion of biomass-derived furfuryl alcohol to levulinate esters over commercial α-Fe2O3

An efficient process for the production of levulinate esters from biomass-derived furfuryl alcohol in liquid alcohol over commercial α-Fe2O3 was firstly investigated. Among the catalysts we tested, α-Fe2O3, a cheap, commercially available and environmentally benign catalyst, exhibited a remarkable catalytic performance for the transformation and gives levulinate esters in good yield compared to the previous studies. The corresponding esters such as methyl levulinate, ethyl levulinate and butyl levulinate were obtained in high yields under optimized reaction conditions. Several influence factors for the formation of levulinate esters were also discussed. A plausible reaction mechanism for the formation of levulinate ester from furfuryl alcohol was proposed. From the viewpoint of practice and economy, the present study provides a potential application for the efficient synthesis of fine chemicals from biomass-derived compounds over cheap, commercially available and environmentally benign catalysts.

Catalytic Hydrothermal Conversion of Biomass-Derived Carbohydrates to High Value-Added Chemicals

The reduction of the dependence on petroleum oil and the development of renewable sources to replace fossil fuels have been a hot topic recently in the field of energy. One of the strategies for the replacement of petroleum oil in the production of fuels is to develop efficient renewable fuels and chemicals from biomass. Efficient conversion of biomass-derived carbohydrates into high value-added chemicals such as alcohols has drawn the attention of many chemists due to their industrial importance. This chapter focuses on our recent research relating to the synthesis of alcohols from biomass-derived esters and their interesting mechanism aspects. New developments including the synthesis of ethylene glycol and 1, 2-propanediol are discussed.