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The deployment of transformational nonaqueous CO2-capture solvent systems is encumbered by high viscosities even at intermediate uptakes. Using single-molecule CO2 binding organic liquids as a prototypical example, we present key molecular features that control bulk viscosity. Fast CO2-uptake kinetics arise from close proximity of the alcohol and amine sites involved in CO2 binding in a concerted fashion, resulting in a Zwitterion containing both an alkyl-carbonate and a protonated amine. The population of internal hydrogen bonds between the two functional groups determines the solution viscosity. Unlike the ion pair interactions in ionic liquids, these observations are novel and specific to a hydrogen-bonding network that can be controlled by chemically tuning single molecule CO2 capture solvents. We present a molecular design strategy to reduce viscosity by shifting the proton transfer equilibrium toward a neutral acid/amine species, as opposed to the ubiquitously accepted zwitterionic state. The molecular design concepts proposed here are readily extensible to other CO2 capture technologies.

The kinetics of the absorption of CO2 into two nonaqueous CO2-binding organic liquid (CO2 BOL) solvents were measured at T=35, 45, and 55 °C with a wetted-wall column. Selected CO2 loadings were run with a so-called "first-generation" CO2 BOL, comprising an independent base and alcohol, and a "second-generation" CO2 BOL, in which the base and alcohol were conjoined. Liquid-film mass-transfer coefficient (k'g ) values for both solvents were measured to be comparable to values for monoethanolamine and piperazine aqueous solvents under a comparable driving force, in spite of far higher solution viscosities. An inverse temperature dependence of the k'g value was also observed, which suggests that the physical solubility of CO2 in organic liquids may be making CO2 mass transfer faster than expected. Aspen Plus software was used to model the kinetic data and compare the CO2 absorption behavior of nonaqueous solvents with that of aqueous solvent platforms. This work continues our development of the CO2 BOL solvents. Previous work established the thermodynamic properties related to CO2 capture. The present paper quantitatively studies the kinetics of CO2 capture and develops a rate-based model.

A comprehensive evaluation of a recently developed water-lean amine-based solvent, namely N-(2-ethoxyethyl)-3-morpholinopropan-1-amine (2-EEMPA), has been performed to analyze its post-combustion CO2 capture performance. This evaluation comprises (1) fundamental characterization of...

SUMMARYIn order to meet U.S. biofuel objectives over the coming decade the conversion of a broad range of biomass feedstocks, using diverse processing options, will be required. Further, the production of both gasoline and diesel biofuels will employ biomass conversion methods that produce wide boiling range intermediate oils requiring treatment similar to conventional refining processes (i.e. fluid catalytic cracking, hydrocracking, and hydrotreating). As such, it is widely recognized that leveraging existing U.S. petroleum refining infrastructure is key to reducing overall capital demands. This study examines how existing U.S. refining location, capacities and conversion capabilities match in geography and processing capabilities with the needs projected from anticipated biofuels production.At a national level, there appears to be adequate conversion and hydrotreating facilities in existing refineries to process anticipated bio-derived oils into transportation fuels. However, numerous concerns are apparent, including: a potential shortfall in both overall hydrotreating capacity and hydrogen production capacity in refineries to manage the conversion of certain biomass derived intermediates having high oxygen content; a regional concentration of anticipated biofuel resources, placing added stress in particular refining regions (e.g. the Gulf Coast); uncertainties surrounding the impact of biomass derived intermediates on the refiner's ability to meet product performance and product quantity demands, and the need for better and more comprehensive chemical composition information; the need for considerably more data and experience on the behavior of projected biofuels intermediates in refining processes (e.g. impacts on process performance and reliability); and  the need to examine the optimum capital investment locations for additional processing equipment. For example, whether it is better to produce finished biofuels at the new production sites, or whether existing refining facilities should be expanded to better handle a more 'raw' bio-oil intermediate.Responding to these concerns may be best accomplished by creating a strong collaboration between the refining industry and the national programs that are working in the field of biomass research. The intent is to identify priorities and opportunities for filling critical knowledge and experience gaps and directing investments in a manner that best supports biofuels objectives.

This manuscript provides a detailed analysis of a continuous-flow, bench-scale study of the CO2-binding organic liquid (CO2BOL) solvent platform with and without its polarity-swing-assisted regeneration (PSAR). This study encompassed four months of continuous-flow testing of a candidate CO2BOL with a thermal regeneration and PSAR regeneration using a decane antisolvent. In both regeneration schemes, steady-state capture of >90% CO2 was achieved using simulated flue gas at reasonable liquid/gas (L/G) ratios. Aspen Plus modeling was performed to assess process performance, compared to previous equilibrium performance projections. This paper also includes net power projections, and comparisons to DOE’s Case 10 amine baseline, and comments on the viability of the CO2BOL solvent class for post-combustion CO2 capture.

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Metal-organic frameworks (MOFs) have proved to be very attractive for applications including gas storage, separation, sensing and catalysis. In particular, CO(2) separation from flue gas in post-combustion processes is one of the main focuses of research among the scientific community. One of the major issues that are preventing the successful commercialization of these novel materials is their high affinity towards water that not only compromises gas sorption capacity but also the chemical stability. In this paper, we demonstrate a novel post-synthesis modification approach to modify MOFs towards increasing hydrophobic behaviour and chemical stability against moisture without compromising CO(2) sorption capacity. Our approach consists of incorporating hydrophobic moieties on the external surface of the MOFs via physical adsorption. The rationale behind this concept is to increase the surface hydrophobicity in the porous materials without the need of introducing bulky functionalities inside the pore which compromises the sorption capacity toward other gases. We herein report preliminary results on routinely studied MOF materials [MIL-101(Cr) and NiDOBDC] demonstrating that the polymer-modified MOFs retain CO(2) sorption capacity while reducing the water adsorption up to three times, with respect to the un-modified materials, via an equilibrium effect. Furthermore, the water stability of the polymer-functionalized MOFs is significantly higher than the water stability of the bare material. Molecular dynamic simulations demonstrated that this equilibrium effect implies a fundamental and permanent change in the water sorption capacity of MOFs. This approach can also be employed to render moisture stability and selectivity to MOFs that find applications in gas separations, catalysis and sensing where water plays a critical role in compromising MOF performance and recyclability.