China 
Africa 
Explore chapters and articles related to this topic
Materials and Synthesis of pH-Responsive Membranes
Published in Randeep Singh, Piyal Mondal, Mihir Kumar Purkait, pH-Responsive Membranes, 2021
Randeep Singh, Piyal Mondal, Mihir Kumar Purkait
The unique properties of supercritical fluids make them desirable for many processes. Supercritical carbon dioxide is the most useful because of its properties, such as it being economical, nontoxic, and nonflammable. Also, its critical parameters are reasonable, with a critical temperature of 31.1°C and a critical pressure of 7.38 MPa. Recently, the major use of critical carbon dioxide is as a solvent in the fields of polymer processing and chemistry. It is used to develop various polymers, fine particles, fibers, polymer fractionation, and foam materials. Supercritical carbon dioxide has the ability to dissolve smaller organic compounds and swell many others. Therefore, supercritical carbon dioxide is useful for the impregnation of different additives in polymers. The properties, such as high diffusivity, low viscosity, negligible surface tension, and tunable solvent strength, help in the uniform distribution of the monomers along with initiators in a very short period of time. Also, it is easy to remove carbon dioxide from the final product because it will be in the gaseous state at ambient conditions of pressure and temperature. Thus, it is very effective and beneficial to use supercritical carbon dioxide for the modification of membranes.
Supercritical Fluids Extraction and Reaction
Published in Carlos Ariel Cardona Alzate, Mariana Ortiz Sanchez, Yury Pisarenko, Reactive Separation for Process Intensification and Sustainability, 2019
Carlos Ariel Cardona Alzate, Mariana Ortiz Sanchez, Yury Pisarenko
Due to its advantages, supercritical carbon dioxide (SCO2) has been used in extraction operations to concentrate different fractions of value-added compounds such as phytosterols [7], Sage [8], antioxidants [9], oil from spent coffee [10], and oil from grapeseed [11]. Additionally, SCO2 has also been used for simultaneous extraction–reaction processes to produce biodiesel from different raw materials [3,12]. At industrial scale, SCO2 has been used for coffee decaffeination, tea decaffeination, and extraction of fatty acids, spices, flavors, and fragrances [13]. Other applications include polymerization, polymer fractionation, particle formation for pharmaceutical and military use, textile dying, and machine cleaning [13].
Production technologies, current role, and future prospects of biofuels feedstocks: A state-of-the-art review
Published in Critical Reviews in Environmental Science and Technology, 2020
Arianna Callegari, Silvia Bolognesi, Daniele Cecconet, Andrea G. Capodaglio
Pretreatments are necessary for the conversion of lignocellulosic materials into ethanol prior to enzymatic hydrolysis and fermentation; they consists of biomass milling to achieve small and homogeneous particles, polymer fractionation, separation of solid components, and end-products recovery. De-toxification and fermentation of pretreatment- released pentoses can also occur. Pretreatment can be biological, physical, chemical or combination thereof, where temperatures and reaction times are process variables, and heat a major cost factor of the process. Pretreatment with dilute acid and intermediate temperatures is generally considered the most cost-effective and acts by loosening the cell wall matrix through degradation of hemicelluloses. A stream of high value products (furfural, hydroxyl-methyl furfural (HMF), phenols, aldehydes, and aliphatic compounds) is obtained from the acid pretreatment, due to the necessary removal of these compounds before the further biochemical processes (Yang & Wyman, 2008). Compared to other pretreatments, steam explosion allows potentially lower capital costs, lower environmental impact, greater energy efficiency, safer process conditions and total sugar recovery (Matsakas et al., 2018). The combination of acid catalysis and steam explosion process was found to reduce temperature and retention time, decreasing the formation of undesired products formation and achieving complete hemicellulose hydrolysis (Vasudevan & Fu, 2010).