Conversion of Biomass to Bio-Oil in Sub- and Supercritical Water

Cascade utilization of lignocellulosic biomass to high-value products

“…26 Considering the importance of biomass utilization for various high-value products and the rapid research process in this area, review articles have been reported based on biomass pretreatment and utilization, for example, the review articles for biomass pretreatment concerning (1) oxidative pretreatment processes; 24 (2) emerging technologies of ultrasound, microwave, gamma ray, electron beam, high hydrostatic pressure and high pressure homogenization; 27 (3) hydrodynamic cavitation (HC) process; 23 (4) chemical, mechanical, thermal, and biological pretreatment; 25 (5) plasma pretreatment; 2 (6) hydrothermal biomass processing; 3 (7) subcritical and supercritical water (SCW) hydrolysis; 28 (8) supercritical water (SC-H 2 O) technology; 29,30 (9) IL pretreatment. 31 The review articles on biomass utilization are mainly based on (1) ultrasound-assisted biological conversion of biomass and waste materials to biofuels; 32 (2) lignin conversion to highvalue polymeric materials; 33 (3) bio-based bioplastics; 34 (4) lignin conversion to low-molecular-weight aromatics; 35 (5) conversion of cellulose into key platform chemicals; 36 (6) converting biomass to biofuels, 37,38 renewable chemicals, 37,39 and fermentable sugars 40 in SCW; (7) hydrogen production from biomass and biomass gasification in SC-H 2 O; 41,42 (8) ultrasound enhanced ethanol production from Parthenium hysterophorus. 43 The articles or reports on biomass cascade utilization are mainly focused on (1) strategies for a more efficient cascade utilization of biomass; 44 (2) barriers to cascading biomass use and policy responses; 45 (3) definitions, policies Scheme 1 Cascade utilization of lignocellulosic biomass.…”

“…78 The CO 2 can be removed in the depressurized process to avoid further environment and corrosion problems. 81,82 Water under sub-and supercritical or supercritical conditions behaves totally different from that under ambient conditions, and it was evidenced as a good medium for lignocellulosic biomass based on the following advantages: 37,38,40,83 (1) wet biomass can be directly used as feedstock, (2) free water can be removed in the liquid state without vaporization, (3) rapid reaction speed (i.e., several seconds) can be achieved, and (4) low dielectric constant and high ion products (i.e., H + and OH − ) behave as non-polar solvents that can dissolve and degrade a variety of lignocellulosic biomass resources even without any additives. SCW can be used either as a pretreatment for the selective fractionation of cellulose, hemicellulose and lignin or as a reaction medium to directly hydrolyze the lignocellulosic biomass into sugars.…”

A critical review of separation technologies in lignocellulosic biomass conversion to liquid transportation fuels production processes

“…Post-treatment of the obtained bio-crude oil (bio-oil phase and aqueous phase) by separation of the phases and by removal of unwanted compounds can improve its physical and chemical properties. This can be accomplished using strategies such as separation via solvent division/extraction, and/or upgrading via hydrodeoxygenation and catalytic cracking (Quitain et al, 2015;Ramirez et al, 2015).…”

Effect of Calcium Formate on Hydrodeoxygenation of Biomass Model Compounds

“…The physical properties such as density, dielectric constant, and ionic product of water decrease as the temperature approaches critical point. 10 Therefore, these properties can be tuned by changing the temperature and pressure making water to behave as a nonpolar solvent suitable for selective extraction and reaction processes involving biomass samples. 11 According to a study, 12 high reaction rates and high yields of gaseous products can be obtained in supercritical water.…”

“…Biomass is liquefied in sub- and supercritical water because of water’s unique properties. The physical properties such as density, dielectric constant, and ionic product of water decrease as the temperature approaches critical point . Therefore, these properties can be tuned by changing the temperature and pressure making water to behave as a nonpolar solvent suitable for selective extraction and reaction processes involving biomass samples .…”