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a b s t r a c t a r t i c l e i n f o Available online xxxx Keywords: CO 2 absorption MEA Amines Global demand Alternative solvents Alternative technologiesRecent research on CO 2 capture is focusing on the optimization of CO 2 absorption using amines (mainly monoethanolamine-MEA) in order to minimize the energy consumption of this very energy-intensive process and improve the absorption efficiency. Process optimization is always required and this research is worth and necessary. However, the main concern arises when thinking of the overall process: solvent production, solvent use and regeneration, and environmental effects related to its use/emissions. The production of MEA from ammonia involves important CO 2 emissions during the Haber-Bosch process. The regeneration of the solvent after the absorption is also an indirect source of CO 2 related to the use of fuels (i.e., combustion processes for energy supply). Thus, the evaluation of the overall balance of CO 2 emitted and captured is essential to determine the efficiency of the process. In addition, other environmental impacts associated to the toxicity and environmental fate of the solvent have to be considered. The use of MEA and other amines in CO 2 capture is a point of concern and a global application does not seem to be the best strategy. This review aims at giving an overview of the main implications of using MEA as absorption solvent for CO 2 capture together with the last advances in research to improve the conventional absorption process. Furthermore, alternatives of using other solvents and/or using other technology and their advantages and weak points will be briefly provided. An approach oriented to produce CO 2 -based products with economic value that can be reintegrated in a closed carbon loop, reducing the use of fresh materials and decreasing the production cost, should be the final objective of current research on CO 2 capture.

The ever increasing industrial production of commodity and specialty chemicals inexorably depletes the finite primary fossil resources available on Earth. The forecast of population growth over the next 3 decades is a very strong incentive for the identification of alternative primary resources other than petro-based ones. In contrast with fossil resources, renewable biomass is a virtually inexhaustible reservoir of chemical building blocks. Shifting the current industrial paradigm from almost exclusively petro-based resources to alternative bio-based raw materials requires more than vibrant political messages; it requires a profound revision of the concepts and technologies on which industrial chemical processes rely. Only a small fraction of molecules extracted from biomass bears significant chemical and commercial potentials to be considered as ubiquitous chemical platforms upon which a new, bio-based industry can thrive. Owing to its inherent assets in terms of unique process experience, scalability, and reduced environmental footprint, flow chemistry arguably has a major role to play in this context. This review covers a selection of C2 to C6 bio-based chemical platforms with existing commercial markets including polyols (ethylene glycol, 1,2-propanediol, 1,3-propanediol, glycerol, 1,4-butanediol, xylitol, and sorbitol), furanoids (furfural and 5-hydroxymethyl­furfural) and carboxylic acids (lactic acid, succinic acid, fumaric acid, malic acid, itaconic acid, and levulinic acid). The aim of this review is to illustrate the various aspects of upgrading bio-based platform molecules toward commodity or specialty chemicals using new process concepts that fall under the umbrella of continuous flow technology and that could change the future perspectives of biorefineries.

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Carbon dioxide (CO2) emissions have to be controlled and reduced in order to avoid environmental risks. Membrane processes in combination with the use of ionic liquids are recently under research and development in order to demonstrate a zero solvent emission process for CO2 capture. In this work, the application of a cross-flow membrane contactor is studied for CO2 absorption when the ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate is used as solvent. A mathematical model considering a parallel flow configuration is applied for a cross-flow system in order to describe the mass transfer rate. At a macroscopic level, K overall a is calculated considering different mixing models corresponding to plug flow and continuous stirred models and a first order mass transfer rate. A microscopic model based on laminar flow has been applied, obtaining a membrane mass transfer coefficient of k m = 3.78 × 10−6 m·s−1, which is about five times higher than that obtained in the macroscopic model. The interfacial area, a, allows the comparison of efficiencies between cross-flow and parallel membrane contactor systems in terms of the product (K overall a).

This work allows the gathering of information during the process design to assist in the choice of the solvent and technology to use.