From hybrid solvents to water-lean solvents – A critical and historical review

From sugars to aliphatic amines: as sweet as it sounds? Production and applications of bio-based aliphatic amines

Aliphatic amines encompass a diverse group of amines that include alkylamines, alkyl polyamines, alkanolamines and aliphatic heterocyclic amines. Their structural diversity and distinctive characteristics position them as indispensable components across multiple industrial domains, ranging from chemistry and technology to agriculture and medicine. Currently, the industrial production of aliphatic amines is facing pressing sustainability, health and safety issues which all arise due to the strong dependency on fossil feedstock. Interestingly, these issues can be fundamentally resolved by shifting toward biomass as the feedstock. In this regard, cellulose and hemicellulose, the carbohydrate fraction of lignocellulose, emerge as promising feedstock for the production of aliphatic amines as they are available in abundance, safe to use and their aliphatic backbone is susceptible to chemical transformations. Consequently, the academic interest in bio-based aliphatic amines via the catalytic reductive amination of (hemi)cellulose-derived substrates has systematically increased over the past years. From an industrial perspective, however, the production of bio-based aliphatic amines will only be the middle part of a larger, ideally circular, value chain. This value chain additionally includes, as the first part, the refinery of the biomass feedstock to suitable substrates and, as the final part, the implementation of these aliphatic amines in various applications. Each part of the bio-based aliphatic amine value chain will be covered in this Review. Applying a holistic perspective enables one to acknowledge the requirements and limitations of each part and to efficiently spot and potentially bridge knowledge gaps between the different parts.

Influence of carbon derivatives on carbon capture investments in coal-based power sector, a China perspective

Coal-based power sector needs deep carbon emission reduction in the upcoming 20 years to fulfill China's carbon peaking and carbon neutrality pledge. Due to the low and fluctuating carbon price in the emission trading system, decarbonization projects are risky and face massive potential losses. To promote decarbonization investment, a lot of policies of subsidy have been set forth. However, market instruments, which could be efficient and motivating for market entities, should have received more attention. In this article, the influence of carbon derivatives on decarbonization investment and financing is analyzed for different technology progresses and price trajectories. Results show that carbon futures and options have de-risking ability, lowering expected variation and financial cost, and consequently, making decarbonization project feasible. For advanced technology and optimistic outlook, investment can be feasible with 42-66% debt share when options are available. For the base case and neutral price outlook, derivatives can pull subsidy down by around 1%.

Impact of Solvent on the Thermal Stability of Amines

Water-lean solvents have been proposed as a possible alternative to aqueous amine systems in postcombustion carbon capture. There is however little data available on how amine degradation is affected by different solvents. This study presents new insights on the effect of solvent on thermal degradation of alkanolamines from laboratory-scale degradation experiments. Replacing the water in aqueous monoethanolamine (MEA) solutions with organic diluents resulted in varying thermal degradation rates. Overall, all tested organic diluents (triethylene glycol, diethylene glycol, mono ethylene glycol, tetrahydrofurfuryl alcohol, N-formyl morpholine/water, and N-methyl-2-pyrrolidone) resulted in higher thermal degradation rates for loaded MEA. None of the proposed parameters, such as acid–base behavior, polarity, or relative permittivities, stood out as single contributing factors for the variation in degradation rates. The typical degradation compounds observed for an aqueous MEA solvent were also observed for MEA in various concentrations and with various organic diluents.

Chemoinformatics-Driven Design of New Physical Solvents for Selective CO2 Absorption

The removal of CO₂ from gases is an important industrial process in the transition to a low-carbon economy. The use of selective physical (co-)solvents is especially perspective in cases when the amount of CO₂ is large as it enables one to lower the energy requirements for solvent regeneration. However, only a few physical solvents have found industrial application and the design of new ones can pave the way to more efficient gas treatment techniques. Experimental screening of gas solubility is a labor-intensive process, and solubility modeling is a viable strategy to reduce the number of solvents subject to experimental measurements. In this paper, a chemoinformatics-based modeling workflow was applied to build a predictive model for the solubility of CO₂ and four other industrially important gases (CO, CH₄, H₂, and N₂). A dataset containing solubilities of gases in 280 solvents was collected from literature sources and supplemented with the new data for six solvents measured in the present study. A modeling workflow based on the usage of several state-of-the-art machine learning algorithms was applied to establish quantitative structure-solubility relationships. The best models were used to perform virtual screening of the industrially produced chemicals. It enabled the identification of compounds with high predicted CO₂ solubility and selectivity toward other gases. The prediction for one of the compounds, 4-methylmorpholine, was confirmed experimentally.

New Solvents for CO2 and H2S Removal from Gaseous Streams

Acid gas removal from gaseous streams such as flue gas, natural gas and biogas is mainly performed by chemical absorption with amines, but the process is highly energy intensive and can generate emissions of harmful compounds to the atmosphere. Considering the emerging interest in carbon capture, mainly associated with increasing environmental concerns, there is much current effort to develop innovative solvents able to lower the energy and environmental impact of the acid gas removal processes. To be competitive, the new blends must show a CO2 uptake capacity comparable to the one of the traditional MEA benchmark solution. In this work, a review of the state of the art of attractive solvents alternative to the traditional MEA amine blend for acid gas removal is presented. These novel solvents are classified into three main classes: biphasic blends—involving the formation of two liquid phases, water-lean solvents and green solvents. For each solvent, the peculiar features, the level of technological development and the main expected pros and cons are discussed. At the end, a summary on the most promising perspectives and on the major limitations is provided.