Solid Sorbents For CO2 Capture Research Articles

A thermodynamic approach to energy requirements for CO2 capture and a comparison between the minimum energy for liquid and solid sorbent processes

There has been an increased interest in the use of solid sorbents for CO2 capture from flue gases to reduce emissions from fossil energy. This work uses a simple Carnot engine-like model to compare the energy requirements for a CO2 capture process using a solid adsorbent in a circulating fluidized bed with its minimal thermodynamic needs and with the performance of a conventional liquid solvent process. The energy requirements for CO2 capture using thermal swing separation sorption are dominated by the standard Gibbs free energy of separation from the sorbent (Δg0,sep), the sensible heat needed to reach the desorption temperature, and loading optimization to avoid thermodynamic pinching effects. The Δg0,sep is an invariant of the system, so only its value at reference conditions is required and it is independent of the desorption temperature or the heat of evaporation of a liquid solvent. A baseline is established using the Δg0,sep as well as the equivalent work for a well-established amine process. In all cases the energy requirements are found to be well above the minimum thermodynamic values and those of conventional liquid absorption. Higher-capacity solid sorbents and challenging improvements on heat recovery will be needed to close the gap.

How Can (or Why Should) Process Engineering Aid the Screening and Discovery of Solid Sorbents for CO2 Capture?

ConspectusAdsorption using solid sorbents is emerging as a serious contender to amine-based liquid absorption for postcombustion CO2 capture. In the last 20+ years, significant efforts have been invested in developing adsorption processes for CO2 capture. In particular, significant efforts have been invested in developing new adsorbents for this application. These efforts have led to the generation of hundreds of thousands of (hypothetical and real) adsorbents, e.g., zeolites and metal-organic frameworks (MOFs). Identifying the right adsorbent for CO2 capture remains a challenging task. Most studies are focused on identifying adsorbents based on certain adsorption metrics. Recent studies have demonstrated that the performance of an adsorbent is intimately linked to the process in which it is deployed. Any meaningful screening should thus consider the complexity of the process. However, simulation and optimization of adsorption processes are computationally intensive, as they constitute the simultaneous propagation of heat and mass transfer fronts; the process is cyclic, and there are no straightforward design tools, thereby making large-scale process-informed screening of sorbents prohibitive.This Account discusses four papers that develop computational methods to incorporate process-based evaluation for both bottom-up (chemistry to engineering) screening problems and top-down (engineering to chemistry) inverse problems. We discuss the development of the machine-assisted adsorption process learning and emulation (MAPLE) framework, a surrogate model based on deep artificial neural networks (ANNs) that can predict process-level performance by considering both process and material inputs. The framework, which has been experimentally validated, allows for reliable, process-informed screening of large adsorbent databases. We then discuss how process engineering tools can be used beyond adsorbent screening, i.e., to estimate the practically achievable performance and cost limits of pressure vacuum swing adsorption (PVSA) processes should the ideal bespoke adsorbent be made. These studies show what conditions stand-alone PVSA processes are attractive and when they should not be considered. Finally, recent developments in physics-informed neural networks (PINNS) enable the rapid solution of complex partial differential equations, providing tools to potentially identify optimal cycle configurations. Ultimately, we provide areas where further developments are required and emphasize the need for strong collaborations between chemists and chemical engineers to move rapidly from discovery to field trials, as we do not have much time to fulfill commitments to net-zero targets.

Evaluating solid sorbents for CO2 capture: linking material properties and process efficiency via adsorption performance

Expanding populations and growing economies result in higher energy needs. Meeting this increasing demand, while lowering carbon emissions, calls for a broad energy mix and commercial deployment of solutions like carbon capture and carbon removal technologies. The scale-up of these solutions is partially hindered by the lack of materials-related information, particularly in the case of solid adsorption-based carbon capture technologies. Furthermore, experimental measurement parameters used and how data is presented lack uniformity, which makes material comparisons extremely difficult. This review examines the current state of solid sorbent characterization for carbon capture, exploring physical and chemical properties, performance parameters, and process indicators. Adsorbent performance parameters demonstrate to be the crucial link between intrinsic material properties and the overall adsorption process effectiveness and therefore are the focus of this work. This paper outlines the relevant techniques used to measure Key Performance Indicators (KPIs) related to adsorption performance such as CO2 adsorption capacity, selectivity, kinetics, ease of regeneration, stability, adsorbent cost, and environmental impact. Additionally, this study highlights the relevant experimental conditions for diluted versus concentrated CO2 streams. Lastly, efforts in harmonizing experimental data sets are considered, and an outlook on solid sorbent characterization for carbon capture processes is presented. Overall, the aim of this work is to provide the reader a critical understanding of KPIs from atomic to process scale, highlighting the importance of experimental data throughout.

Effect of Arginine-Based Deep Eutectic Solvents on Supported Porous Sorbent for CO2 Capture Analysis

Carbon dioxide (CO2) as one of the heat-trapping gases, has caused global warming. Being a greener and more economical material, amino acid-based deep eutectic solvents (AADES) have attracted interest in CO2 capture applications. In this paper, the effect of L-arginine (Arg) in binary AADES of arginine-ethylene glycol (Arg-EG) and ternary AADES of choline chloride-ethylene glycol-arginine (ChCl-EG-Arg) on adsorption of CO2 was studied. The solubility, basicity, and physicochemical characteristics were compared with the binary DES (ChCl-EG) before and after being impregnated into a silica gel (SG) via the wet impregnation method. The AADES/SG adsorbents were evaluated for CO2 sorption performance using an automated gas sorption analyzer at 100% CO2 loading and thermogravimetric analysis (TGA) at flue gas conditions (15% CO2/85% N2). Findings show the basicity and the nitrogen content (N%) of AADES/SG were increased as Arg was added and DES/AADES functional group peaks (amino, hydroxyl, alkyl groups) were observed after the impregnation. The CO2 sorption of 16.0 mg/g at 25 °C and 1 atm was achieved by 30% Arg-EG(1:8)/SG followed by 30% ChCl-EG-Arg (1:2:0.1)/SG (14.8 mg/g) and 30% ChCl-EG/SG(1:2) (14.5 mg/g) using an Autosorb iQ2 instruments with 100% CO2 loading. The CO2 uptake was increased almost linearly with increasing pressure and decreased with increasing temperature. The Arg-EG(1:8)/SG shows the highest selectivity toward CO2 than other sorbents with 8.10 mg/g adsorption for 1 h at 15% CO2 loading at 25 °C with higher thermal stability and surface area. Considering environmental, technological, and economic viewpoints, the Arg-EG(1:8)/SG can be explored more as a potential solid sorbent for CO2 capture.

In-situ Fe/Ti doped amine-grafted silica aerogel from fly ash for efficient CO2 capture: Facile synthesis and super adsorption performance

Developing a cost-effective and high-efficiency solid sorbent for CO2 capture is current research focus. In this work, Fe/Ti doped in-situ amine-modified silica aerogel (AMSA) was synthesized from fly ash by grafting with 3-(Aminopropyl) triethoxysilane (APTES) via a simple ambient pressure drying process, and verified as an efficient sorbents for CO2 capture. The effects of experimental parameters such as acid leaching factors, gelling temperature and aging time, APTES concentration on the structure characteristics and CO2 adsorption properties of as-prepared AMSAs were investigated in detail. Results demonstrated that the AMSAs exhibited a high CO2 adsorption ability of 4.95 mmol∙g−1 at 70 °C, and maintained 94.3 % of their maximum capacity after 10 adsorption–desorption cycles, indicative of long cycle stability of the sorbent. Moreover, the adsorption equilibrium Langmuir isotherm model was established while the kinetic adsorption behavior was well simulated by the double exponential model. This facile and environmental-friendly synthesis method may provide a novel reference for enhanced CO2 capture sorbents from solid waste.

Sunlight-controlled CO2 separation resulting from a biomass-based CO2 absorber

Renewable solid sorbents for CO2 capture and storage have shown great potentials for the sake of gaseous separation, tail gas treatment, environmental regulation and climate governance. However, current existed preparation and reusability of solid sorbents are generally subject to high energy consumption and complicated procedure. Herein, a light-controlled CO2 separation system with high working temperature resulting from natural sawdust combined with polyethyleneimine is fabricated, which involves low energy input and few operating sequences. This system shows a direct and ratiometric response to sunlight illumination by which CO2 can be reversibly adsorbed and released. This light-controlled CO2 separation process is prospective to become an attractive alternative to traditional alkaline CO2 collection method in terms of its convenience and low cost. As a practical demonstration, CO2 mixed with N2 is successfully separated through this light-controlled carbon capture and storage (CCS) system, which offers great promise for CO2 capture and enrichment with applicability across a wide range of scales.

Li4SiO4 pellets templated by rice husk for cyclic CO2 capture: Insight into the modification mechanism

Li4SiO4 stands out among various solid sorbents for CO2 capture. The commonly used mechanical granulation process for Li4SiO4 sorbents causes the destruction of the microstructures. Therefore, with the characteristics of huge production and low cost, an agricultural waste (rice husk) was employed as a pore former to improve the structures of Li4SiO4 pellets and, thus, enhance the cyclic CO2 sorption performance. The rice husk templating greatly enhanced the CO2 sorption capacity of Li4SiO4 pellets. Especially, 20 wt% rice husk-templated Li4SiO4 exhibited the capacity of 0.21 g/g, which was nearly twice that of the unmodified sorbent. The quick release of the combustion gases from burning rice husk could create porosity for the sorbents. In addition, the alkaline compositions in rice husk promoted the CO2 sorption due to the decreased CO2 diffusion resistance by the formation of molten phases. Moreover, the ashes of rice husk after high-temperature combustion were found to block the pores of the sorbents, leading to the capacity reduction. The comprehensive function of rice husk templating for Li4SiO4 pellets was the tradeoff between the positive effects of pore creation and alkaline doping and the negative effects of pore blockage by the ashes.

Strong Foam-like Composites from Highly Mesoporous Wood and Metal-Organic Frameworks for Efficient CO2 Capture.

Mechanical stability and multicycle durability are essential for emerging solid sorbents to maintain an efficient CO2 adsorption capacity and reduce cost. In this work, a strong foam-like composite is developed as a CO2 sorbent by the in situ growth of thermally stable and microporous metal-organic frameworks (MOFs) in a mesoporous cellulose template derived from balsa wood, which is delignified by using sodium chlorite and further functionalized by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation. The surface carboxyl groups in the TEMPO-oxidized wood template (TO-wood) facilitate the coordination of the cellulose network with multivalent metal ions and thus enable the nucleation and in situ growth of MOFs including copper benzene-1,3,5-tricarboxylate [Cu3(BTC)2], zinc 2-methylimidazolate, and aluminum benzene-1,3,5-tricarboxylate. The TO-wood/Cu3(BTC)2 composite shows a high specific surface area of 471 m2 g–1 and a high CO2 adsorption capacity of 1.46 mmol g–1 at 25 °C and atmospheric pressure. It also demonstrates high durability during the temperature swing cyclic CO2 adsorption/desorption test. In addition, the TO-wood/Cu3(BTC)2 composite is lightweight but exceptionally strong with a specific elastic modulus of 3034 kN m kg–1 and a specific yield strength of 68 kN m kg–1 under the compression test. The strong and durable TO-wood/MOF composites can potentially be used as a solid sorbent for CO2 capture, and their application can possibly be extended to environmental remediation, gas separation and purification, insulation, and catalysis.

Degradation Behavior of Purified Components of Tetraethylenepentamine Impregnated Solid Sorbents for Co2 Capture

Amine functionalized materials have been widely investigated as promising candidates for CO2 capture. Tetraethylenepentamine (TEPA) is the commercial amine that has been commonly impregnated into porous supports for post-combustion CO2 capture. Commercial technical-grade TEPA is a mixture of four main ethyleneamine compounds with close boiling points including linear, branched, and two cyclic TEPA products. This study investigated the stability of the four main components of TEPA under accelerated oxidizing conditions. The CO2 adsorption performances of the sorbents containing TEPA components decreased after the exposure to O2. Among the isolated components in commercial TEPA, 1,4,7,10,13-pentaazatridecane displayed the most sensitivity to O2, which were supported by infrared spectroscopic, gas chromatography, and NMR analysis.

Single Step Synthesis and Characterization of Activated Carbon from Date Seeds for CO2 Capture

In the efforts to combat the increase in the excess emissions of anthropogenic CO2, CCS technologies such as solid sorbents for CO2 capture have been explored. Activated carbon is considered one of the most promising adsorbents due to its many advantages, such as its good thermal stability and excellent adsorption capacity. Activated carbon prepared from date seeds agricultural biomass have already been developed and are used in many industrial applications. However, there is not much research that explored their potential for CO2 capture applications. This study reports the preparation of chemically activated Activated carbon (AC) using KOH. Different impregnation ratios and activation temperatures were studied to find the best preparation combination for high CO2 capture capacity. At the optimized impregnation ratio of 2.5:1 and activation temperature of 600 °C, the produced AC had the highest adsorption capacity of 2.18 mmol/g and BET surface area of 1033.09 m2/g.

Simulation of elevated temperature combined water gas shift and solid sorbent CO2 capture for pre-combustion applications using computational fluid dynamics

Water gas shift reaction combined with CO2 adsorption is a novel promising technology for pre-combustion CO2 capture in IGCC applications. By combining the two processes in an IGCC, reduction in plant capital cost (by eliminating the separate shift reactors) and in heat rate (by reducing their steam injection rates) may be realized. CFD modeling was employed to predict the CO2 adsorption, desorption and shift reaction rates, CO2 loading, CO2 breakthrough curve and temperature distribution within the reactor. The model was validated against experimental data. It was shown that significant increase in temperature occurs near the bottom region of the combined catalyst and sorbent mixed zone because majority of the reaction occurs over a small region where the feed syngas contacts the WGS catalyst. Injection of liquid water between beds is investigated for temperature control. CFD simulation model of the combined WGS and CO2 capture would be useful in reactor design, developing thermal management strategies to avoid the high temperature zones, and developing IGCC overall plant design as well as in assessing the plant thermo-economics.

Enhanced kinetics for CO2 sorption in amine-functionalized mesoporous silica nanosphere with inverted cone-shaped pore structure

Amine-functionalized mesoporous silica is one of the most promising solid sorbents for CO2 capture. The pore structure of sorbents plays a crucial role in enhancing sorption and desorption kinetics. In this work, mesoporous silica nanosphere (MSN) with inverted cone-shaped pore structure was synthesized and examined as the support for polyethyleneimine (PEI). The unique pore structure of MSN support for PEI resulted in significantly faster sorption and desorption rates and higher sorption capacity within short sorption time when compared to the benchmark support SBA-15 with the same amount of PEI loading. With 65 wt% PEI loading, 65PEI/MSN sorbent showed about 50% higher working capacity, together with 27% faster rate of CO2 sorption and 71% faster rate of CO2 desorption, compared to that with 65PEI/SBA-15 in sorption/desorption cycles. PEI/MSN sorbents have great potential for practical applications in CO2 capture.

Investigation of the carbon dioxide adsorption behavior and the heterogeneous catalytic efficiency of a novel Ni-MOF with nitrogen-rich channels.

MOFs have attracted remarkable attention as solid sorbents in CO2 capture processes for their low-energy post-combustion. In this paper, a new Ni-based MOF, Ni4(TATB)1.5(EtO)3.5(NEt3)4, was synthesized and characterized using various physicochemical techniques. The efficiency of the as-prepared Ni-MOF as a solid sorbent for CO2 capture was investigated, and acceptable adsorption was exhibited. Furthermore, this Ni-MMOF was used as a catalyst in toluene selective oxidation, for eliminating a volatile organic compound, with tert-butyl hydroperoxide as an oxidant in the absence of organic solvents. The obtained results indicated that Ni-MOF has good catalytic activity and could be reused three times without considerable loss of its catalytic activity. This study highlights the great potential of developing MOFs to achieve green chemistry goals with the removal of hazardous liquid and gas compounds such as toluene and CO2.

Continuous CO2 Capture Performance of K2CO3/Al2O3 Sorbents in a Novel Integrated Bubbling-Transport Fluidized Reactor

Using solid sorbents for CO2 capture is a promising technology. The temperature swing adsorption feature of such a process requires both sufficient gas-sorbent contact time and an adjustable sorben...

Carbon dioxide capture using waste tire based adsorbent

In this study, a waste tire derived activated carbon (AC) was assessed as a solid sorbent for CO2 capture. The objectives of this study is to determine the effectiveness of AC from waste rubber tire via chemically activation with potassium hydroxide (KOH) as a low cost solid adsorbent on the adsorption of CO2 from the mixture of N2 and CO2 at different adsorption temperature, adsorption flow rate and impregnation ratio. The reactor temperatures were 30°C, 40 °C and 50°C and the flow rate was 50 cm3/min, with an impregnation ratio of 1 and 1.5. The breakthrough time was found to decrease with increasing of impregnation ratio of KOH and decreasing of adsorption temperature and flow rate. The AC with 1.5 KOH impregnation ratio has shown the best CO2 adsorption capacity among the adsorbents studied and the adsorption capacity is 238.7mg/g of adsorbent at 30°C.

Novel short-cut estimation method for the optimum total energy demand of solid sorbents in an adsorption-based CO2 capture process

In solid-sorbent CO2 capture, CO2 desorption is ordinarily carried out at high temperatures with or without a vacuum. The strategy and specific conditions for CO2 desorption are determined from an economic point of view and depend entirely on the characteristics of the adsorbent. In this study, we propose a semi-graphical short-cut method that enables easy estimation of the minimum energy demand for capturing unit amount of CO2 together with associated optimum process operating conditions. Our method uses only the most basic properties of the adsorbent such as the adsorption equilibrium and kinetic information and heat capacity. The proposed short-cut method was numerically investigated and evaluated for a set of seven adsorbents: three physical adsorbents and four chemical adsorbents. Compared with the results of the conventional rigorous model, highly accurate predictions were obtained from the proposed short-cut method. The short-cut method enables the rapid and accurate screening of sorbents, which will ultimately accelerate the development of economically deployable CO2 capture processes based on solid sorbents.

Highly efficient and durable metal-organic framework material derived Ca-based solid sorbents for CO2 capture

Calcium looping is a promising technology for CO2 capture, although traditional calcium-based sorbents undergo a rapid loss of capacity after repeated cycles. Improving the toughness of sorbents can be accomplished with the use of stabilizer compounds, but at the cost of sorption performance. Minimizing the stabilizer content whilst maintaining high thermal stability is an effective pathway to solve this bottleneck. Here, a facile MOF-templated synthesis route is for the first time reported to yield highly efficient Al2O3-stabilized, Ca-based sorbents. Cyclic performance experiments and detailed characterization techniques are employed to identify the effects of synthesis factors on the structure-performance relationship of the synthesized CO2 sorbents. Calcium aluminum solid solution and its homogeneous mixture with CaO at the nanoscale provide for high thermal stability. The different CO2 uptake behavior for the synthesized sorbents primarily results from the influence of synthesis factors on the crystallization rates and coordination modes between metal ion and organic ligands. The stabilizer content (i.e. Al2O3) can be as low as 4.44 wt% and yet maintain a favorable thermal stability. Compared to that of the limestone-derived CO2 sorbents, the best MOF-derived sorbent can achieve about 500% times the CO2 sorption capacity after 30 repeated CO2 uptakes and sorbent regenerations.

Enhancement Mechanism of the CO2 Adsorption–Desorption Efficiency of Silica-Supported Tetraethylenepentamine by Chemical Modification of Amino Groups

Tetraethylenepentamine (TEPA) and its derivatives were used to functionalize mesocellular silica foam (MSU-F) supports by wet impregnation for utilization as solid sorbents for CO2 capture. TEPA de...

Pilot Scale Demonstration of Solid Sorbent CO2 Capture Technology at a Biomass Power Station

Solid sorbent CO2 capture is widely discussed as a cost-efficient alternative to existing post-combustion CO2 capture processes. TU Wien and Shell have been working on the development of a continuous solid sorbent CO2 capture process since 2011. In 2015, both partners joined the collaborative research project ViennaGreenCO2 that is based in Vienna, Austria and that has the overall objective to demonstrate and study the solid sorbent CO2 capture process at pilot scale. This work introduces the ViennaGreenCO2 project and discusses the work that has been attributed to process upscaling in the first years of the project. Finally, the design of the ViennaGreenCO2 pilot plant is presented and discussed in this work.

Simulation of elevated temperature solid sorbent CO2 capture for pre-combustion applications using computational fluid dynamics

CO2 adsorption is one of the warm gas cleanup technologies under development for integrated gasification combined cycle (IGCC) applications. Computational Fluid Dynamics (CFD) can be a practical and powerful tool for reactor design for and optimization of the CO2 adsorption process. In this present work, CFD simulation was developed in commercially available ANSYS Fluent software and validated for solid sorbent CO2 capture to investigate pressure swing adsorption (PSA) for CO2 separation from syngas with all the auxiliary operating steps. The adsorption equilibrium and kinetics were incorporated into ANSYS by user defined functions (UDFs) for source terms in Navier–Stokes equations. The CFD model well predicted the CO2 breakthrough curve and temperature change. It was shown that in demo reactor operation, at the end of adsorption step, only half of the sorbent was loaded with CO2, while most of the loaded CO2 was released during the desorption step. Further optimization of sorbent packing and cycle operation can be done with assistance of this CFD model to maximize bed loading, and used to design the commercial size reactors.