Esters production via carboxylates from anaerobic paper mill wastewater treatment

Abstract

This paper describes a new option for integrated recovery and esterification of carboxylates produced by anaerobic digestion at a pH above the pK. The carboxylates (acetate, propionate, butyrate, valerate and lactate) are recovered using a strong anion exchange resin in the bicarbonate form, and the resin is regenerated using a CO-expanded alcohol technique, which allows for low chemicals consumption and direct esterification. Paper mill wastewater was used to study the effect of pH and the presence of other inorganic anions and cations on the adsorption and desorption with CO-expanded methanol. Calcium, which is present in paper mill wastewater, can cause precipitation problems, especially at high pH. Esters yields ranged from 1.08±0.04mol methyl acetate/mol of acetate to 0.57±0.02mol methyl valerate/mol of valerate.

Applications of Dimethyl Carbonate for the Chemical Upgrading of Biosourced Platform Chemicals

“…Then, at 100−120°C, sorbed succinate undergoes an Omethylation reaction mediated by DMC and catalyzed by quaternary ammonium groups (Q+) of the resin. This exemplifies a low-temperature alkylation pathway, unusual for DMC, which according to further study of the same group is affected by the nature and hydrophobicity of ammonium cations 50. In the presence of water, the resulting methoxycar-bonate anions exchanged on to resin, decompose thereby restoring the original bicarbonate-based resin and releasing methanol.…”

Recovery Techniques Enabling Circular Chemistry from Wastewater

“…However, the regeneration of the resin and recovering the carboxylates in their acid form is not straightforward, requiring an extra agent (e.g., H 2 SO 4 ) to protonate them, which results in a stoichiometric amount of salt production [56]. To circumvent this drawback, Cabrera-Rodríguez et al [56,58] have applied CO 2 -expanded methanol, which generated HCO 3…”

“…By means of this method, Cabrera-Rodríguez et al [56] could reach a desorption yield of 0.79 mol acetic acid per mol acetate entering the desorption process at 10 bar CO 2 and ambient temperature using a mimicked fermentation broth. Furthermore, the esterification yield in the combined desorption-esterification is reported to be 1.03 mol methyl acetate per mol acetate at 5 bar CO 2 and 60 • C. Later on, the feasibility of this integrated recovery and esterification of the carboxylate process using real wastewater was also investigated [58]. The recycled paper industry wastewater has been applied to anaerobically produce carboxylates, followed by recovering the carboxylates by an AEX resin and desorption-esterification by CO 2 -expanded methanol (see Figure 5).…”

Increasing Profits in Food Waste Biorefinery—A Techno-Economic Analysis

“…Caproic acid solubility, 10.8 g/L in water [68] is low when compared to the miscibility of acetic and butyric acid [70]. Carboxilic acids esterification has been also reported to be improve separation, and reducing costs [71]. Electro-dialysis has been explored in order to increase carboxylic acid yield in dark fermentation [72][73][74], and for the separation of lactic acid from the culture broth [75].…”