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Conversion of Biomass
Published in Jean-Luc Wertz, Philippe Mengal, Serge Perez, Biomass in the Bioeconomy, 2023
Jean-Luc Wertz, Philippe Mengal, Serge Perez
Biomethane has been the main focus in literature as the final product of anaerobic digestion.80 Nevertheless, short-chain carboxylic acids deriving from the intermediate acidogenic phase like acetic, propionic, butyric, and caproic acids, otherwise called volatile fatty acids (VFA) or carboxylates, are also of high industrial interest. Acidogenesis (or acidogenic fermentation) has been mostly studied in view of increasing biogas (e.g., two-stage anaerobic digestion systems) or biohydrogen (i.e., dark fermentation) yields. However, it can be envisaged as a stand-alone process with a product of higher added value.
Soil-Release Finishes
Published in Menachem Lewin, Stephen B. Sello, Handbook of Fiber Science and Technology: Chemical Processing of Fibers and Fabrics, 2018
Anionic soil-release polymers are more effective in alkaline than in acid solutions. This is related to conversion of the carboxylic acid group, a relatively weak hydrophile, to the carboxylate ion, a strong hydrophile. The negatively charged polymer improves detergency and reduces wet soiling of negatively charged soil particles in the wash solution. However, anionic polymers can increase retention of positively charged carbon soil [43].
Process Design Considerations for Large–Scale Chromatography of Biomolecules
Published in Kenneth E. Avis, Vincent L. Wu, Biotechnology and Biopharmaceutical Manufacturing, Processing, and Preservation, 2020
Richard Wisniewski, Egisto Boschetti, Alois Jungbauer
Sulfates are, in most cases, attached to polysaccharide sorbents and are typically used at pH below 7. Sulfonates are attached to both saccharidic polymer material and synthetic polymers. Carboxylates are obtained by alkaline reaction of chloroacetic acid on hydroxyl-containing polymers; they are widely used as cation exchangers in a more restricted range of pH than sulfonated media. Quaternary amino groups are well-known structures for strong cationic media; their high pK value allows their use in a wide pH range with, in a number of cases, the provision of higher selectivity in separating anionic proteins than media with tertiary amino groups. Diethyl-aminoethyl (DEAE) groups, very popular in protein separations, are complex structures resulting from the reaction between diethyl-aminoethyl chloride and a nonionic sorbent containing hydroxyl groups under alkaline conditions. Such chemical conditions induce secondary reactions on the monomer itself, generating oligo-DEAE chains. These complex structures with different pKs are characterized easily by titration curves; however, they do not modify the ion-exchange mechanism with proteins. In contrast to gel filtration media (see below), the matrix does not have a strictly defined pore size. Here the pores are generally large enough to avoid any possible molecular sieving effect during separation. Commercially available ion exchangers have various mechanical and chemical resistances and are based on natural, synthetic, and mineral composite materials. The type of group immobilized to the matrix determines the type and strength of the ion exchanger. There are a variety of groups that have been selected for use as ion exchangers (Table 3.6).
Study of a cross-linked hydrogel of Karaya gum and Starch as a controlled drug delivery system
Published in Journal of Biomaterials Science, Polymer Edition, 2019
Sapna Sethi, Balbir Singh Kaith, Mandeep Kaur, Neeraj Sharma, Sadhika Khullar
The extent of water absorption of hydrogel also depends upon pH as variation in pH of the swelling medium often causes a change in free volume available for water penetration [28] because the protonation and deprotonation of carboxylic acid groups present on hydrogel network is controlled by pH of the swelling medium. At low pH, carboxylic acid groups remain protonated and there are no interionic repulsions which results in contraction of the hydrogel network thus the SR decreases. At high pH, the carboxyl groups get ionized in aqueous medium to form carboxylate ions. The negative charge on carboxylate ions increases electrostatic repulsions among polymer chains and create more space to accommodate extra water molecules. Along with this, the ionization of hydroxyl groups of polysaccharides also contributes to improved swelling capacity of the hydrogel. So increase in pH of the swelling medium lead to the significant increase in SR.
Carbon capture and utilization technologies: a literature review and recent advances
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2019
Francisco M. Baena-Moreno, Mónica Rodríguez-Galán, Fernando Vega, Bernabé Alonso-Fariñas, Luis F. Vilches Arenas, Benito Navarrete
As can be seen in Table 3, except for K2CO3, none of the catalysts result in the formation of 4-hydroxybenzoic acid (p-HBA). An increase in salicylic acid formation was observed up to a yield of 68% with the use of 30 mmol of K2CO3, although an optimum amount of K2CO3 of 10 mmol was suggested, since the greatest increase in HBA formation occurs at this amount (Iijima and Yamaguchi 2008b). Although the traditional method previously explained has been widely used, some of the pioneering studies in the synthesis of carboxylic acids are taking place in the field of electrochemistry. One of the advantages of the organic compounds reduction in presence of CO2 is the efficient fixation of CO2 to organic molecules, forming C-C bonds under soft conditions. CO2 electroreduction could be presented as a worthy alternative to these processes that involve intensive use of energy as well as the replacement of toxic reducing agents by electrons. It has been shown that the resulting carboxylic acid is obtained with high efficiency by using reactive metals such as magnesium or aluminum galvanic or sacrificial anode, which also has its drawbacks, which will be discussed later (Matthessen et al. 2014; Senboku and Katayama 2017). Some authors studied the electrolysis by divergent pairs of diacid precursors and diol, from the cathodic carboxylation and the simultaneous anodic acetoxylation of conjugated dienes (Matthessen et al. 2015, 2014; Senboku et al. 2015; Tateno et al. 2015). In their studies, an innovative methodology is defined that allows a conversion of CO2 using a durable and inert anode. This process results in the formation of dicarboxylate salts and diacetate esters, from cathodic carboxylation and anodic acetoxylation, respectively. Trifluoroacetate (TFA) and tetraethylammonium (TEA) were used both as supporting electrolytes and as reagents for acetoxylation, forming their corresponding salts in the solution. The electrolysis of other diene substrates was also carried out under the same conditions as in the previous case. It should be mentioned that in the case of 1,3-butadiene, the CO2 pressure was 10 bar. It can be observed that by carrying out the electrolysis of 1,3-cyclohexadiene with nickel cathode and graphite anode, in a solution of CH3CN with TEA and TFA, under a pressure of 1 bar of CO2, a carboxylation yield of 35% and an acetoxylation yield of 49% were obtained (Matthessen et al. 2015).