Reactive Distillation of Glycolic Acid Using Heterogeneous Catalysts: Experimental Studies and Process Simulation

Abstract

The glycerol oxidation reaction was developed leading to selective catalysts and optimum conditions for the production of carboxylic acids such as glycolic acid. However, carboxylic acids are produced in highly diluted mixtures, challenging the recovery and purification, and resulting in high production costs, polymerization, and thermal degradation of some of the products. The protection of the acid function by esterification reaction is one of the most promising alternatives through reactive distillation (RD); this technique allows simultaneously the recovery of carboxylic acids and the elimination of most part of the water. The reactive distillation, experimental and simulation, of glycolic acid was performed, based on kinetic and thermodynamic models developed. For the thermodynamic model, binary parameters of the missing couples were determined experimentally, and the non-random two-liquid (NRTL) model was selected as the most suitable to represent the binary behavior. The kinetic study of the esterification in the presence of homogeneous and heterogeneous catalysis concluded that the heterogeneous reaction can be accurately described either by a pseudo-homogeneous model or the Langmuir–Hinshelwood (L-H) adsorption model. Reactive distillation was conducted in a distillation column filled with random packing sulfonated ion-exchange resin, Nafion NR50®, or with extruded TiO2-Wox. The conversion rate of glycolic acid in reactive distillation increases from 14% without catalyst to 30% and 36% using Nafion NR50® and TiO2-Wox, respectively. As opposed to the batch reactor study, the conversion rate of glycolic acid was better with TiO2-Wox than with sulfonated ion-exchange resin. The better performance was related to an increase in the hydrodynamics inside the column. Tests using water in the feed confirm the hypothesis by increasing the conversion rate because of the decrease in the mass transfer resistance by reducing the average diffusion coefficient. The simulation of the reactive distillation column with ProSim® Plus showed that the yield of the ester increased operating at a low feed rate with reactive stripping. In the presence of water in the feed, nonreactive stages are required, including an enrichment region to separate water vapor.

Revisiting Electrocatalytic CO2 Reduction in Nonaqueous Media: Promoting CO2 Recycling in Organic Molecules by Controlling H2 Evolution

“…Even though the eCO 2 RR using an organic electrolyte is more selective than an aqueous electrolyte, a mixture of different carboxylic acids is usually obtained. Several recovery and purification technologies can be found to purify these products, such as nanofiltration, [79,80] reverse osmosis, [80] distillation, [81,82] and liquid-liquid extraction. [42,83,84] While the purification technologies are usually studied for aqueous solutions, they can also be applied in nonaqueous solutions, making minor changes and/or combining two or more processes.…”

Parametric Optimization of a Reactive Distillation Column for the Ethyl Tert-Butyl Ether Production

“…For some feedstocks, the innovative combined unit outperforms the classic approach in six out of nine environmental impact categories. Reactive distillation syntheses are actively studied not only experimentally, but also by means of validated simulations based on kinetic and thermodynamics models developed for various processes [10]. A detailed review of more than 100 industrially important processes with RD is presented in [5].…”

Studies of the Dependency between Salt Content and the Adsorption of Glycolic Acid on Carriers in Aqueous Solutions

“…In the mentioned methods, the deep recovery and efficient enrichment of glycolic acid from aqueous solutions play a crucial role, which is significantly demanding in industrial conditions due to the high affinity of glycolic acid to water and the potential to polymerize in concentrated and heated solutions. Methods and different combinations applied to separating glycolic acid from solutions include membrane separation and crystallization [20], vacuum distillation, or reactive distillation [21] of glycolate esters [22,23] or reactive liquid-liquid extraction [13], [24]. It is worth it to mention that adsorption methods involving natural-based adsorbents such as grape leaf residues [25,26], bagasse fly ash, and natural clays [27,28] or in addition, aluminum oxide [29] and synthetic adsorption resins [30].…”