Please cite this article as: Lachos-Perez D., Brown A.B., Mudhoo A., Martinez J., Timko M.T., Rostagno M.A., Forster-Carneiro T. Subcritical and supercritical water extraction, hydrolysis, gasification and carbonization of biomass: a critical review. Biofuel Research Journal 14 (2017) HIGHLIGHTSØAdvances of research trends in development of subcritical and supercritical water processes technologies are reviewed.Essential aspects of sub-and supercritical water applied to extraction, hydrolysis, carbonization and gasification processes are discussed. ØEquipment design, process parameters, and types of biomass used for sub-and supercritical water process are presented. ØBioactive compounds, reducing sugars, hydrogen, biodiesel, and hydrothermal char are the final products of sub-and supercritical water processes. This review summarizes the recent essential aspects of subcritical and supercritical water technology applied to the extraction, hydrolysis, carbonization, and gasification processes. These are clean and fast technologies which do not need pretreatment, require less reaction time, generate less corrosion and residues, do not use toxic solvents, and reduce the synthesis of degradation byproducts. The equipment design, process parameters, and types of biomass used for subcritical and supercritical water process are presented. The benefits of catalysis to improve process efficiency are addressed. Bioactive compounds, reducing sugars, hydrogen, biodiesel, and hydrothermal char are the final products of subcritical and supercritical water processes. The present review also revisits advances of the research trends in the development of subcritical and supercritical water process technologies. GRAPHICAL ABSTRACT ARTICLE INFO ABSTRACT
Biomass soot samples were generated at fast pyrolysis conditions in a DTF at 1250°C.• The reactivity of soot was determined in 40 vol.% CO 2 gasification by TGA.• The most reactive was cellulose soot with the largest separation distance.• The least reactive CH 3 OH extracted lignin soot had the smallest separation distance.• The particle size and radical concentration of soot influenced the reactivity less.
We present a new technology for removing free and dissolved hydrocarbons from oilfield produced water. Organoclay completely removes free hydrocarbons from wastewaters and also removes dissolved hydrocarbons including benzene, toluene, ethylbenzene, and xylene (BTEX). When used in conjunction with a polishing stage of granular activated carbon, organoclay removes free and dissolved hydrocarbons to levels well below current water quality standards. Organoclay is produced by combining sodium montmorillonite clay with a cationic quaternary amine salt, which replaces adsorbed sodium by ion exchange. Resulting clay surfaces become organophilic. Hydrocarbons are removed from water by adsorption. The quaternary amines create organic "pillars" between the clay platelets that increase the interlamellar distance and facilitate the formation of a hydrocarbon partition. Introduction Oil-water separation technology seems to be unable to keep pace with water quality limits due to either operating or economic performance. Scholtes1 reported that the 1995 EPA Region VI "Final NPDES General Permit for Produced Waters. . . " was based on "general acceptance of the inability of coastal operators to comply with Louisiana state effluent limitations of 15 mg/L total oil and grease content in produced waters. " In addition, beneficial usage or surface discharge of produced water remains limited because current treatment methods have been unable to remove hydrocarbons with sufficient reliability and economy to commercialize desalination technologies such as reverse osmosis or electrodialysis.2,3 Adsorption offers one means of cleaning produced water and meeting environmental compliance goals at nominal cost. Granular activated carbon (GAC) has been a de facto standard for removing soluble hydrocarbons from wastewater by adsorption. It is widely used to remove a wide range of soluble hydrocarbons including benzene, toluene, ethylbenzene, and xylene (BTEX) and has been studied in the oilfield for removing BTEX from water produced with natural gas and with aquifer gas storage.4 Organoclay possesses several advantages over GAC for removing free hydrocarbons:It offers much higher adsorption and can adsorb up to 60–70% hydrocarbon by weight.It is most efficient in removing insoluble and dispersed hydrocarbons that contribute to Total Petroleum Hydrocarbon (TPH) and Oil & Grease measurements.It tolerates concentration spikes that result from separator or treater upsets and accidental oil carry-over from storage tanks.Adsorbed hydrocarbons do not desorb. Spent media would likely be classified in the United States as a non-hazardous waste. When organoclay is used in combination with GAC, adsorption provides high removal efficiency and excellent reliability in treating hydrocarbon-contaminated wastewaters.
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