Jianglin Cao

High-yield reduction of carbon dioxide into formic acid by zero-valent metal/metal oxide redox cycles

A strategy for reduction of CO2 is described that produces formic acid from CO2 (ca. 80% formic acid yield) via the oxidation of a zero-valent metal under hydrothermal conditions. The oxidized metal can be regenerated using glycerin, which produces lactic acid. Hydrogen production is demonstrated through metal oxidation in the presence of CO2 with zero-valent Fe, Mn, Zn, and Al metals under hydrothermal conditions, where it is found that a maximum hydrogen formation yield of ca. 99.4% was achieved. The metals, once oxidized, could be readily reduced (ca. 100% for Fe) to their zero-valent state by contact with glycerin. The results demonstrate that a carbon cycle can be driven by the oxidation and reduction of commonly available metals.

Oxidation of unsaturated carboxylic acids under hydrothermal conditions

Hydrothermal oxidation pathways of high molecular weight unsaturated carboxylic acids were investigated for the potential use of chemoselectivity to improve the efficiency of the desired products from biomasses directly containing or easily producing unsaturated carboxylic acids. Hock cleavage, which frequently occur at general chemical, was observed in the absence of any acid catalyst and may be a potential major oxidation cleavage mechanism, which leads to the cleavage at both the carbon-carbon double bond and the single bond near a double bond. The addition of a peroxyl radical to the double bond may be also a potential major oxidation mechanism, which leads to the oxidation cleavage mainly at the carbon-carbon double bond. Cleavage at the carbon-carbon bond near the double bond by the addition of a peroxyl radical to the double bond may also occur. However, oxidation at either alpha-, beta-, or gamma-carbon to the -COOH group hardly occurred. These results may help to selectively produce desired products from biomasses, such as lignin and oils.

Production of lactic acid from C6-polyols by alkaline hydrothermal reactions

Production of lactic acid from C6-polyols (Mannitol) under alkaline hydrothermal conditions was investigated. Experiments were performed to examine the difference in the production of lactic acid between C6-polyols and C3-polyols (glycerine), as well as C6-aldoses (glucose). Results showed that the yield of lactic acid from C6-polyols was lower than that from both glycerine and glucose. It indicated that long chain polyols might follow a different reaction pathway from that of glycerine. Further investigation is needed to clarify the reaction mechanism and improve the relatively low lactic acid acid yield from C6-polyols.

Hydrothermal Conversion of Glycerin into Lactic Acid by a Continuous-Flow Reactor

Abstract Using a self-established laboratory scale continuous-flow reactor, the experimental research on continuous hydrothermal conversion of glycerin into lactic acid was made, to lay a foundation for quantity production of lactic acid from glycerin. The optimal operation condition for producing lactic acid in the continuous-flow reactor, and a ~60% lactic acid yield was achieved. Bad mixing of the reactants as well as a large surface area of the inner wall of the reactor tube decreased significantly the lactic acid yields, especially with a long residence time under a high concentration of alkali. The continuous-flow reactor was modified by substituting the 1/8’’ tube with a 1/4’’ tube and equipping a mixing device, and was tested to perform as well as the one with a 1/8’’ tube. The research results would help design and establish a more high-efficient continuous-flow reactor for hydrothermal conversion of glycerin into lactic acid.

Catalytic hydrothermal conversion of dissolved carbon dioxide into methane

This paper aims to convert NaHCO3 (dissolved carbon dioxide in NaOH solution) into methane via hydrothermal catalytic reaction. The effects of various experimental parameters on the conversion efficiency of NaHCO3, e.g., amount of reactant (Zn) and catalyst (Ni), temperature, reaction time etc, were investigated. The results showed that a maximal 43.6% yield of methane was obtained at the optimal conditions: Zn 0.1 mol, Ni 0.06 mol, temperature of 300° C, reaction time of 120 min, filling rate of 35% and NaHCO3 0.01 mol. In the absence of Ni catalyst, CO2 was mostly converted into formic acid (formic acid yield of 87%) and the corresponding methane yield was zero, while in the presence of Ni, the yield of methane increased to 43.6% and the yield of formic acid was only 3%. Based on these results, it was supposed that Ni played a catalytic role in hydrothermal conversion of CO2 into methane and formic acid was the intermediate product during the formation of methane from CO2 in the hydrothermal processes.

Hydrothermal Conversion of Carbohydrates into Lactic Acid with Alkaline Catalysts

In this paper, alkaline hydrothermal experiments of glucose, fructose and xylose, the model compounds of carbohydrate biomass, were conducted in a batch reactor in the temperature range of 250 to 350 oC to examine the production of lactic acid. Result showed that the formation of lactic acid in a hydrothermal reaction of glucose, fructose and xylose could be promoted notably by using NaOH, KOH and Ca(OH)2 as alkaline catalysts.The yield of lactic acid from glucose, fructose and xylose followed the sequence of fructose > glucose > xylose with NaOH as alkaline catalyst. For fructose, high lactic acid yields of 43.5 % with NaOH and 46 % with KOH on the carbon base were obtained at the temperature of 300 oC.

Production of Formic Acid and Acetic Acid by Hydrothermal Oxidation of Alkali Lignin

The production of formic acid and acetic acid by hydrothermal oxidation of alkali lignin, a kind of biomasses, was investigated using a batch reactor with H2O2 oxidant. Experiments were performed over a wide range of conditions with temperature varying from 260 to 320° C, oxygen supply varying from 60% to 120%, and reaction time varying from 30 to 150 s. The highest yield of formic acid was 4.9% at 280° C for 120 s with the additive ratio of H2O2 100%. The highest value of acetic acid was 12.3% at 300° C for 120 s with the additive ratio of H2O2 100%. Based on the intermediate products identified by GC/MS and HPLC, reaction pathways of alkali lignin are discussed. It was found that maleic acid and fumaric acid were two primary unsaturated intermediate products. The production of formic acid and acetic acid were come from the oxidative decomposition of intermediate products in the oxidation process. Increasing the formation of saturated dicarboxylic acids and glutaconic acid would enhance the acetic acid y...

Rapid Conversion of Biomass and Carbon Dioxide into Fuel and Chemicals by Hydrothermal Reactions

The presentation gives an overview of some recent advances in our research on hydrothermal conversion of biomasses, mainly including cellulose and lignocellulosic biomass, and carbon dioxide into chemicals, such as acetic acid, lactic acid and formic acid.

Transfer Hydrogenation Reaction Of Ketones And Formic Acid Under Hydrothermal Conditions Without A Catalyst

The hydrothermal experiments with ketones and formic acid showed that the hydrogen transfer reduction of ketones can be conducted with formic acid as a hydride donor in the presence of NaOH at 300° C. The yield of alcohols was considerably higher at a much lower ratio of hydrogen source to ketones than the traditional Meerwein‐Ponndorf‐Verley reduction, reaching 60% for isopropanol from acetone and 70% for lactic acid from pyruvic acid. Water molecules as a catalyst may directly participate in the transition state by making a hydrogen‐bond ring network with the substrate molecules.

Production of Lactic Acid from Polyols and Aldoses by Hydrothermal Reactions

In this paper, lactic acid production from C6-polyols is investigated to compare with that from C6-aldoses under hydrothermal conditions. Experiments of C5-polyols and C5-aldoses were also performed. Results showed that the yield of lactic acid from C6-polyols was lower than from both C6-aldoses and glycerine. Reactions of C5-polyols revealed the same results. It is indicated that, being different from both aldoses and glycerine, long chain polyols might follow a different reaction pathway. Further investigation is needed to clarify the reaction mechanism.