Sustainable conversion of wet biomass, algae, and food waste to fuels in hot compressed water: Multi-Scale analysis

Hydrolysis behavior of tofu waste in hot compressed water

Hot compressed water (HCW), with its unique properties, is regarded as a promising solvent for industrial applications. A number of methods to measure the solubility of hydrophobic organic compounds (HOCs) in HCW have been reported. However, these methods were conducted in large‐scale stainless‐steel reactors, and few included an in situ study regarding the dissolution mechanism of HOCs in HCW during the solubility determination process. In this study, a fused silica capillary reactor in combination with Raman spectroscopy was applied to investigate phase changes, determine the solubility, and study the dissolution mechanism of 1,2‐dichlorobenzene in HCW. The total dissolution process of 1,2‐dichlorobenzene in HCW was observed under a microscope, and the images were recorded continuously using a digital camera. Raman spectroscopy was used to confirm the homogeneity of the 1,2‐dichlorobenzene solution during dissolution. The solubility of 1,2‐dichlorobenzene increased from 35.9 to 85.7 mg g−1 in water with increasing temperature from 256.7 to 294.1 °C. Furthermore, the dissolution mechanism of 1,2‐dichlorobenzene in HCW is proposed based on the Raman spectra of 1,2‐dichlorobenzene and water during the dissolution process in the fused silica capillary reactor. The breakage of the fully hydrogen‐bonded (tetrahedral) configuration and the consequent change in the static dielectric constant of water are deemed to be compelling reasons for the high solubility of 1,2‐dichlorobenzene in HCW. Our experimental method exhibits great potential for determining the solubility of HOCs in HCW and for investigating their dissolution behavior and dissolution mechanism at elevated pressure and temperature conditions. Copyright © 2017 John Wiley & Sons, Ltd.

New insights on monosaccharides’ isomerization, dehydration and fragmentation in hot-compressed water

Conversion in hot compressed water (e.g., 600 °C and 300 bar) is considered to be a promising technique to treat very wet biomass or waste streams. In this paper, a new experimental method is described that can be used to screen the operating window in a safe, cheap, and quick manner (one measurement takes about 5 min). Small sealed quartz capillaries (i.d. = 1 mm) filled with biomass or model compounds in water are heated rapidly in a fluidized bed to the desired reaction temperature. The reaction pressure can be controlled accurately by the initial amount of solution in the capillary. After a certain contact time, the capillaries are lifted out of the fluidized bed, rapidly quenched, and destroyed to collect the produced gases for GC analysis. Results of measurements for formic acid and glucose solutions have shown that the technique is reliable enough for screening purposes including trend detection. For conversions above 30%, three identical measurements are sufficient to produce reasonably accurate a...

Oil palm fronds, the lignocellulose waste material produced from palm oil plantation, was subjected to the pretreatment in hot compressed water for sugar production. In this study, the influence of fast hot compressed water (15 minutes holding time) was investigated at temperature 170, 190 and 210 °C in a batch autoclave. After hot compressed water process, the products were separated into solid residue and liquid fraction by filtration. The chemical composition and color change of the oil palm frond residues after pretreatment were evaluated by Fourier Transform infrared (FTIR) spectroscopy and CIELAB parameters. The solid residue was further submitted to hydrolysis for fermentable sugar production using a commercial enzyme. The relative changes in the intensity of FTIR spectra bands indicate that hot compressed water deconstructed the structure of palm oil frond by removing hemicellulose. The fast hot compressed water of oil palm frond resulted in color changes to the darkness because of the lignin modification. Enzymatic hydrolysis yield that 50.5% (b/v) fermentable sugar can be produced after 48 h saccharification process on pretreated at 190 °C for 15 minutes, suggesting that the hot compressed water pretreatment of oil palm frond can be considered as inexpensive, simple and environmentally friendly pretreatment methods.

Part I Characters of High Temperature Water and Hydrothermal Reactions.- Water under High Temperature and Pressure Conditions and Its Applications to Develop Green Technologies for Biomass Conversion.- Part II Hydrothermal Conversion of Biomass into Chemicals.- Hydrothermal Conversion of Cellulose into Organic Acids with a CuO Oxidant.- Hydrothermal Conversion of Lignin and Its Model Compounds into Formic Acid and Acetic Acid.- Production of Lactic Acid from Sugars by Homogeneous and Heterogeneous Catalysts.- Catalytic Conversion of Lignocellulosic Biomass to Value-Added Organic Acids in Aqueous Media.- Catalytic Hydrothermal Conversion of Biomass-Derived Carbohydrates to High Value-Added Chemicals.- Part III Hydrothermal Conversion of Biomass into Fuels.- Effective Utilization of Moso-Bamboo (Phyllostachys Heterocycla) with Hot Compressed Water.- Hydrothermal Liquefaction of Biomass in Hot-Compressed Water, Alcohols and Alcohol-Water Co-Solvents for Bio-Crude Production.- Hydrothermal Liquefaction of Biomass.- Hydrothermal Gasification of Biomass for Hydrogen Production.- Part IV Hydrothermal Conversion of Biomass into Other Useful Products.- Review of Biomass Conversion in High Pressure High Temperature Water (HHW) including Recent Experimental Results (Isomerization and Carbonizaiton).- Hydrothermal Carbonization of Lignocellulosic Biomass.- Part V Hydrothermal Conversion of Biomass Waste into Fuels.- Organic Waste Gasification in Near- and Super-Critical Water.- Hydrothermal Treatment of Municipal Solid Waste for Producing Solid Fuel.- Sewage Sludge Treatment by Hydrothermal Process for Producing Solid Fuel.

Improved pretreatment of yellow poplar biomass using hot compressed water and enzymatically-generated peracetic acid

Decomposition of 1,1,1-trichloroethane in hot compressed water in anti-corrosive fused silica capillary reactor and Raman spectroscopic measurement of CO2 product

Wood was treated in hot compressed water at 200–350°C without a catalyst to produce charcoal. The charcoal carbonized at various temperatures under hot compressed water was mainly analyzed by FT-IR in order to investigate the changes in the chemical structures during the carbonization process. The FT-IR spectra showed that the carbonization of wood was promoted by the increasing reaction temperature. The intensity of the peaks due to the -OH and -CH of wood became weak with the increasing reaction temperature. The dehydrogenation and deoxygenation in wood were observed during the treatment with the hot compressed water. The studies clarified that the carbonization of wood was promoted at low temperature using the hot compressed water.

Hot compressed water (HCW), also known as subcritical water (SCW), refers to high-temperature compressed water in a special physical and chemical state. It is an emerging technology for natural product extraction. The volatile organic compounds (VOCs) generated from the Maillard reaction between l-ascorbic acid (ASA) and l-cysteine (Cys) have attracted significant interest in the flavor and fragrance industry. This study aimed to explore the formation mechanism of VOCs from ASA and Cys and examine the effects of reaction parameters such as temperature, time, and pH in HCW. The identified VOCs were predominantly thiophene derivatives, polysulfides, and pyrazine derivatives in HCW. The findings indicated that thiophene derivatives were formed under various pH conditions, with polysulfide formation favored under acidic conditions and pyrazine derivative formation preferred under weak alkaline conditions, specifically at pH 8.0. The Maillard reaction between ASA and Cys mainly produced thiophene derivatives, polysulfides, and pyrazine derivatives in HCW. The generation mechanism was significantly dependent on the surrounding pH conditions. © 2024 Society of Chemical Industry.

Thermodynamic analysis of in-situ hydrogen from hot compressed water for heavy oil upgrading

Over the past years, superheated, close‐to‐critical and supercritical water (hot compressed water) have met with an increasing interest as reaction medium. In this work, a method for determining the residence time distribution of reactors with hot compressed water has been developed. In experiments performed in a testing plant residence time distribution was measured directly downstream of the reactor at high pressure and high temperature and by using a view cell together with an UV‐active tracer substance.

Hydrolysis experiment of woody biomass in hot compressed water (HCW) was conducted in a batch-type reactor and the characteristics of solid residue after the HCW hydrolysis treatment were measured to understand the hydrolysis mechanism of woody biomass. Woody slurry of Douglas fir was used in this HCW experiment. Reaction temperature was controlled from 423 to 523 K, and the reaction time was set at 1 min. After separation of solid residues from the hydrolysis liquid material, the solid residue characteristics, such as proximate and ultimate analysis, particle size distribution, particle shape, surface area, pore size distribution, chemical composition, and equilibrium moisture content ratio, were measured and then the decomposition mechanism of woody biomass in HCW was discussed. It was found that the solid residue characteristics yielded in HCW changed drastically depending on the reaction temperature. For example, cellulose crystallinity decreased with increasing reaction temperature, and the physical characteristics of solid residue, such as particle shape, particle diameter, and pore size distribution, also changed dramatically depending on the reaction temperature. The physical or chemical characteristic change in HCW was strongly related to the decomposition of components of woody biomass at that reaction temperature. Dehydration of woody components was one of the most important factors to understand physical characteristics during HCW treatment.

Rice straw was treated using hot compressed water with or without phosphoric acid for enzymatic saccharification. The yields of xylose and glucose obtained from the treatment of the rice straw using hot compressed water without phosphoric acid were low. However, when 0.7% phosphoric acid solution was added to hot compressed water, the yield of xylose increased remarkably, and the highest yield (71%) was obtained at 160°C. Furthermore, the yield of glucose from the treated rice straw by enzymatic saccharification using an enzyme cocktail with a cellulase loading of 2 FPU/g- rice straw was 86%. It clarified that the hot compressed water treatment with phosphoric acid was effective in lowering the enzyme loading compared with the original hot compressed water treatment.

Effects of Kraft lignin on hydrolysis/dehydration of sugars, cellulosic and lignocellulosic biomass under hot compressed water