Hydrothermal electrolysis reactions of glycerol were investigated under various operating conditions to determine the effects of applied DC current, electrolysis time, and alkali concentration on the decomposition mechanism of glycerol. In addition, intermediate products were identified, possible reaction schemes for both hydrothermal electrolysis and hydrothermal degradation of glycerol based on experimental data were clarified, and detailed product analysis was conducted using high performance liquid chromatography (HPLC), gas chromatography with a flame ionization detector (GC-FID), and gas chromatography with a thermal conductivity detector (GC-TCD). For the present study, a continuous flow reactor equipped with titanium electrodes (as cathode and anode), an electric furnace, a heater, a pump, a heat exchanger, a back pressure regulator, and DC supply was used. The main gaseous product was hydrogen, whereas glycolaldehyde, lactic acid, and formic acid were the main liquid products. Results indicate that greater than 92% of the glycerol could be decomposed under optimum conditions by hydrothermal electrolysis using the continuous flow reactor.

Recently, there has been a rising interest for the disposal of biorelated components that cannot be treated easily by biological processes. Because of the development of biodiesel production, the production of by-products such as crude glycerol has increased dramatically. Presently, in many biodiesel plants with low capacity, the aqueous phase containing produced/left glycerol, which is an important molecule in the context of renewable biomass resources to provide hydrogen energy and chemical intermediates, methanol and salts as by-products, is discharged as wastewater. In this manner, both environmental pollution and economical losses are created. Therefore, we developed a new hydrothermal electrolysis system, by which these organics can be converted into value added chemicals, under high-temperature and high-pressure aqueous conditions. In this study, hydrothermal electrolysis reactions of glycerol with an alkali were investigated systematically to determine the intermediate products and current efficiency. We next studied the effects of electricity loading on the molecular transformation of glycerol through the comparison of the product distribution obtained by hydrothermal electrolysis with that by hydrothermal degradation under alkaline conditions. As a gaseous product, hydrogen gas was generated, whereas lactic acid was produced as the main liquid product. The yield of lactic acid increased to 34.7% at 280°C with 50 mM NaOH after 90 min reaction time.

Hydrothermal conversion of waste hazelnut shell in hot compressed water, green and environmentally friendly medium, was investigated under different operating conditions to clarify the effects of reaction temperature, reaction time, acid concentration and acid kind (H 2 SO 4 and H 3 PO 4 ) on the production of value-added chemicals with high temperature/high pressure autoclave. In literature, to our best knowledge, there is no study about the production of levulinic acid, as a high value chemical, from waste hazelnut shell in hot-compressed water without using any mineral and heterogeneous catalyst. Hydrothermal reactions were conducted at 150-280°C for reaction times of 15 to 120 min with various H 2 SO 4 and H 3 PO 4 concentrations varying from 0 to 125 mM. The detailed liquid product species were identified with High Performance Liquid Chromatography (HPLC) and gaseous products were analyzed by Gas Chromatography with a Thermal Conductivity Detector (GC-TCD). The main identified liquid compounds were levulinic acid, acetic acid and furfural while carbon dioxide and carbon monoxide were the major gaseous products. Increasing the reaction temperature (280°C) and reaction time (120 min) resulted in a significant increment on the conversion (65.40%) as well as levulinic acid yield (13.05%). The production of levulinic acid was enhanced with H 2 SO 4 addition; whereas treatments with H 3 PO 4 improved the furfural production.

In this paper, a novel hybrid process for the treatment of microcrystalline cellulose (MCC) under hot-compressed water was investigated by applying constant direct current on the reaction medium. Constant current range from 1A to 2A was applied through a cylindrical anode made of titanium to the reactor wall. Reactions were conducted using a specially designed batch reactor (450 mL) made of SUS 316 stainless steel for 30-120 min of reaction time at temperature range of 170-230°C. As a proton donor H 2 SO 4 was used at concentrations of 1-50 mM. Main hydrolysis products of MCC degradation in HCW were detected as glucose, fructose, levulinic acid, 5-HMF, and furfural. For the quantification of these products, High Performance Liquid Chromatography (HPLC) and Gas Chromatography with Mass Spectroscopy (GC-MS) were used. A fractional factorial design with 2-level of four factors; reaction time, temperature, H 2 SO 4 concentration and applied current with 3 center points were built and responses were statistically analyzed. Response surface methodology was used for process optimization and it was found that introduction of 1A current at 200°C to the reaction medium increased Total Organic Carbon (TOC) and cellulose conversions to 62 and 81 %, respectively. Moreover, application of current diminished the necessary reaction temperature and time to obtain high TOC and cellulose conversion values and hence decreased the energy required for cellulose hydrolysis to value added chemicals. Applied current had diverse effect on levulinic acid concentration (29.9 %) in the liquid product (230°C, 120 min., 2 A, 50 mM H 2 SO 4 ).

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"In this study, pristine cellulose was functionalized by the phosphorylation reaction to make it suitable for lithium separation. After characterization studies of the synthesized adsorbent with SEM, EDX, FTIR, TGA and XPS, the effects of various parameters on the lithium uptake capacity of the adsorbent were examined. The analysis of equilibrium data by several adsorption models showed that maximum adsorption capacity of the adsorbent was found to be 9.60 mg/g at 25 °C by the Langmuir model. As initial concentration and contact time increased, adsorption capacity also increased, however, mild temperature (25-35 °C) and pH (5-6) were better for the adsorption of lithium. 80% of lithium adsorption within three minutes proved the fast kinetic nature of the adsorbent. A 99.5% desorption efficiency of lithium was achieved with 0.5 M H2SO4, among HCl and NaCl with different molarities. Phosphorylated cellulose was shown to be a favorable adsorbent for the recovery of lithium from aqueous solutions."

Electrolysis reactions of lactic acid were studied using a 500 mL continuous flow reactor made of SUS 316 stainless steel. In this system, a titanium wall acted as a cathode and a titanium plate-layered type electrode was used as an anode in a subcritical reaction medium. The reactor wall (stainless steel) and the cathode (titanium) were separated from each other by a cylindrical ceramic wall. This hydrothermal electrolysis process provides an environmentally friendly route that does not use any organic solvents or catalysts to produce value-added chemicals from wastewater treatment. Reactions were conducted with a 30 min residence time at a pressure of 10 MPa at 280 °C via application of various direct currents ranging from 0.5 to 2 A. In addition, to improve our understanding of the reaction mechanism, we investigated the effects of initial lactic acid and electrolyte (NaOH) concentrations on the degradation of lactic acid and the product yields using continuous flow hydrothermal electrolysis. Acrylic acid, acetic acid, and acetaldehyde were detected as the main reaction products using high-performance liquid chromatography. Increasing the applied current increased the conversion of lactic acid and product yields. With a current of 2 A, an electrolysis time of 30 min, and the addition of 50 mM NaOH, a 55% conversion was achieved. The acetaldehyde yield increased almost linearly with current, and at 2 A, 24.73% of the acetaldehyde was produced compared to a 2.25% yield of acetic acid under the same conditions. For acrylic acid, at higher currents (1.5 and 2.0 A), the rate of generation of acrylic acid decreased (values of 0.82, 0.65, and 0.49% at 1.0, 1.5, and 2.0 A, respectively). Increasing the pH of the feed solution resulted in a drastic decrease in the yields of acrylic acid and acetaldehyde.

In this study, electrochemical degradation of microcrystalline cellulose (MCC) under hot-compressed water was investigated via application of constant voltage on reaction medium. Constant voltage ranges from 2.5 to 8.0 V was applied between anode (Titanium) and cathode (reactor wall). As an electrolyte and proton source 5-25 mM of H 2 SO 4 was used. Reactions were carried out in a specially designed batch reactor (450 mL) made of T316 for 240 min at temperature of 200°C.MCC decomposition products such as glucose, fructose, furfural, 5-HMF and levulinic acid were detected and quantified by High Performance Liquid Chromatography (HPLC). In the absence of electrolyte, applied voltage (2.5 and 4.0 V) decreased the total organic carbon (TOC) yield, in contrast at 8.0 V, TOC yield increased to 13%. Application of 8.0 V in hydrothermal conditions alter MCC decomposition pathway selectively to furfural (15%). Addition of electrolyte (5 mM, H 2 SO 4 ) and application of 2.5 V potential increased TOC (54%) and changed the decomposition pathway in favor of 5-HMF (30%) and levulinic acid (21%). The structural changes in solid residues of electrochemically reacted MCC was analyzed by Fourier Transform Infrared Spectroscopy (FTIR) and found that MCC particles functionalized by carboxylic acid and sulfonated groups by the application of constant voltage to reaction medium. In the presence of electrolyte, under certain voltage (2.5 V), functionalization of solid particles became more obvious in FTIR spectrum results. Therefore, change in the selectivity values of degradation products were conducted with the functionalization of MCC particles due to applied voltage under sub-critical conditions.