Because of the scarcity of fossil resources, high crude oil prices, and the environmental benefit of using renewable feedstock, fermentation technologies applied to the production of chemicals have arisen as a feasible alternative to traditional processes. One of the most promising commodities in the chemical industry is succinic acid, which currently has a market of over $0.4 billion per year and the potential to increase up to $1.3 billion per year. Petrochemical derived succinic acid has a lower production price ($1.05 to 1.29 US/Kg) compared with that derived by fermentation ($1.66 to 2.2 US/Kg, sold at $5-9 US/Kg). Therefore, efforts must be done to decrease processing costs in bio-based succinic acid production. Owing to the majority of processing costs in fermentation are accounted for the separation and purification of the desired product (50 - 80% of the final cost), many attempts to improve and reduce separation steps have been made, but to date there is not a successful technology scaled up to industrial production. Despite the fact that several separation processes have been proposed to overcome this problem (precipitation, ion exchange resins, membranes, reactive extraction, and liquid-liquid extraction), none addresses the main limiting barriers of large energy and material requirements as well as waste generation. One of the most promising alternatives is the direct conversion of succinic acid to esters using hybrid reactors, mainly reactive distillation. This process has shown remarkable advantages in similar applications (i.e. acetates production, ethyl lactate, fatty acids, etc.) by reducing processing costs, and could provide esters as intermediate products for the synthesis of other chemicals from succinic acid. Although this is a well understood technology, research focused on the performance of the operation for succinic acid compounds must be conducted, in order to create the tools required for design and scale up to large scale production.In this work a recovery process of succinic acid through esterification with ethanol is studied. Although it is particularly applied for succinic acid, this approach could be used for other acids and alcohols. In the first part an experimental study on phase equilibria of esterification mixtures and reaction kinetics is presented. In a second stage, succinic salts are recovered by precipitation and esterification using synthetic and actual culture broth mixtures. Recovery of succinic species higher than 90% was obtained. In a next stage, experiments on esterification using a pilot plant reactive distillation column proved that high conversion of succinic acid (> 98%) and high selectivity to diethyl succinate (>98%) can be obtained. Simulations of reactive distillation unit using Aspen plus® process design software (Version 7.1, AspenTech) were validated using pilot scale experiments. Good agreement of the model was observed. Finally, using the model previously developed, a complete conceptual design of a process for the recovery of succinic acid from a fermentation broth was developed in Aspen Plus® including a preliminary economic study. Results indicated that the process is feasible under different conditions. Economic analysis indicates that the process is a feasible alternative to compete with current technologies for succinic acid recovery.
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