Lisha Yang

High yield production of levulinic acid by catalytic partial oxidation of cellulose in aqueous media

A high yield of levulinic acid was produced by directly converting cellulose over a ZrO2 catalyst by a one-pot catalytic aqueous phase partial oxidation (APPO) process. Compared to conventional acid hydrolysis, APPO is a highly selective and environmentally benign process with merits of easy recovery and re-use of heterogeneous catalysts.

Highly efficient hydrogen storage system based on ammonium bicarbonate/formate redox equilibrium over palladium nanocatalysts.

A highly efficient, reversible hydrogen storage-evolution process has been developed based on the ammonium bicarbonate/formate redox equilibrium over the same carbon-supported palladium nanocatalyst. This heterogeneously catalyzed hydrogen storage system is comparable to the counterpart homogeneous systems and has shown fast reaction kinetics of both the hydrogenation of ammonium bicarbonate and the dehydrogenation of ammonium formate under mild operating conditions. By adjusting temperature and pressure, the extent of hydrogen storage and evolution can be well controlled in the same catalytic system. Moreover, the hydrogen storage system based on aqueous-phase ammonium formate is advantageous owing to its high volumetric energy density.

Direct Conversion of Cellulose into Ethyl Lactate in Supercritical Ethanol–Water Solutions

Biomass-derived ethyl lactate is a green solvent with a growing market as the replacement for petroleum-derived toxic organic solvents. Here we report, for the first time, the production of ethyl lactate directly from cellulose with the mesoporous Zr-SBA-15 silicate catalyst in a supercritical mixture of ethanol and water. The relatively strong Lewis and weak Brønsted acid sites on the catalyst, as well as the surface hydrophobicity, were beneficial to the reaction and led to synergy during consecutive reactions, such as depolymerization, retro-aldol condensation, and esterification. Under the optimum reaction conditions, ∼33 % yield of ethyl lactate was produced from cellulose with the Zr-SBA-15 catalyst at 260 °C in supercritical 95:5 (w/w) ethanol/water.

Low-temperature oxidation of guaiacol to maleic acid over TS-1 catalyst in alkaline aqueous H2O2 solutions

Abstract To mitigate the negative environmental impact of greenhouse gas (GHG) emission originated from the use of fossil fuels, the chemical world is switching to utilize renewable biomass resources. Co-producing value-added chemicals is important for an integrated biorefinery to improve economics of biofuels. Lignin derived compounds, e.g. guaiacol, are common by-products of fast pyrolysis of lignocellulosic biomass. In this paper, the feasibility of low-temperature selective oxidation of guaiacol to value-added dicarboxylic acids, e.g. maleic acid, was investigated using titanium silicalite/hydrogen peroxide (TS-1/H2O2) reaction system. Under the reaction conditions (80 °C and the initial pH = 13.3), the molar yields of maleic acid from guaiacol were approximately 20%–30%. The effects of catalyst amount, initial pH values, reaction time, and temperature on the yields of maleic acid were investigated. A possible reaction mechanism of TS-1 catalyzed aromatic ring opening was proposed.

Catalytic Conversion of Lignocellulosic Biomass to Value-Added Organic Acids in Aqueous Media

The transition from today’s fossil-based economy to a sustainable economy based on renewable biomass is driven by the concern of climate change and anticipation of dwindling fossil resources. Although biofuels are the central theme of the transition, biomass resources cannot completely replace petroleum. It is projected that biofuels can only supply up to 30 % of today’s transportation fuel market even if all available domestic biomass resources are used for the production of liquid fuels. Therefore, transformation of biomass into high-value-added chemicals is advantageous to secure optimal use of the abundant, but limited, biomass resources from the economical and ecological perspective. Industry is increasingly considering bio-based chemical production as an attractive area for investment. The potential for chemical and polymer production from biomass is substantial. The US Department of Energy recently issued a report which listed 12 chemical building blocks considered as potential building blocks for the future. Organic acids (e.g., succinic, lactic, levulinic acid, etc.) are among the widely spread “platform-molecules,” which may be further converted into possibly derivable high-value-added chemicals. The transition from a fossil chemical industry to a renewable chemical industry will likewise depend on our ability to focus research and development efforts on the most promising alternatives. In this chapter, we review the emerging technologies on catalytic conversion of biomass to value-added organic acids in aqueous media.

Coupling Glucose Dehydrogenation with CO2 Hydrogenation by Hydrogen Transfer in Aqueous Media at Room Temperature

Conversion of CO2 into value-added chemicals and fuels provides a direct solution to reduce excessive CO2 in the atmosphere. Herein, a novel catalytic reaction system is presented by coupling the dehydrogenation of glucose with the hydrogenation of a CO2 -derived salt, ammonium carbonate, in an ethanol-water mixture. For the first time, the hydrogenation of CO2 to formate by glucose has been achieved under ambient conditions. Under the optimal reaction conditions, the highest yield of formate reached approximately 46 %. We find that the apparent pH value in the ethanol-water mixture plays a central role in determining the performance of the hydrogen-transfer reaction. Based on the 13 C NMR and ESI-MS results, a possible pathway of the coupled glucose dehydrogenation and CO2 hydrogenation reactions was proposed.

Catalytic Oxidation Pathways for the Production of Carboxylic Acids from Biomass

The transition from a fossil chemical industry to a renewable chemical industry depends on breakthroughs in the research and development on the most promising alternatives. Biomass is such a class of renewable raw carbon materials for the production of fuels and chemicals, with growing interest among researchers aiming to achieve global sustainability. Catalytic oxidation of biomass can lead to multiple products, and the challenge is to direct the reaction pathways to the desired products. Organic acids are among the listed “platform molecules,” which have the potential to be further converted into high-value-added chemicals. In this chapter, various pathways are reviewed for catalytic oxidation of a variety of biomass to produce value-added organic acids.