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Table of Content
28 November 2018, Volume 26 Issue 11
    Special issue of Carbon Capture, Utilisation and Storage
    Critical review of strategies for CO2 delivery to large-scale microalgae cultures
    Qi Zheng, Xiaoyin Xu, Gregory J. O. Martin, Sandra E. Kentish
    2018, 26(11):  2219-2228.  doi:10.1016/j.cjche.2018.07.013
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    Microalgae have great, yet relatively untapped potential as a highly productive crop for the production of animal and aquaculture feed, biofuels, and nutraceutical products. Compared to conventional terrestrial crops they have a very fast growth rate and can be produced on non-arable land. During microalgae cultivation, carbon dioxide (CO2) is supplied as the carbon source for photosynthesising microalgae. There are a number of potential CO2 supplies including air, flue gas and purified CO2. In addition, several strategies have been applied to the delivery of CO2 to microalgae production systems, including directly bubbling CO2-rich gas, microbubbles, porous membrane spargers and non-porous membrane contactors. This article provides a comparative analysis of the different CO2 supply and delivery strategies and how they relate to each other.
    Carbon dioxide capture by solvent absorption using amino acids: A review
    Guoping Hu, Kathryn H. Smith, Yue Wu, Kathryn A. Mumford, Sandra E. Kentish, Geoffrey W. Stevens
    2018, 26(11):  2229-2237.  doi:10.1016/j.cjche.2018.08.003
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    The emission of large amounts of carbon dioxide is of major concern with regard to increasing the risk of climate change. Carbon capture, utilisation and storage (CCUS) has been proposed as an important pathway for slowing the rate of these emissions. Solvent absorption of CO2 using amino acid solvents has drawn much attention over the last few years due to advantages including their ionic nature, low evaporation rate, low toxicity, high absorption rate and high biodegradation potential, compared to traditional amine solvents. In this review, recent progress on the absorption kinetics of amino acids is summarised, and the engineering potential of using amino acids as carbon capture solvents is discussed. The reaction orders between amino acids and carbon dioxide are typically between 1 and 2. Glycine exhibits a reaction order of 1, whilst, by comparison, lysine, proline and sarcosine have the largest reaction constants with carbon dioxide which is much larger than that of the benchmark solvent monoethanolamine (MEA). Ionic strength, pH and cations such as sodium and potassium have been shown to be important factors influencing the reactivity of amino acids. Corrosivity and reactivity with impurities such as SOx and NOx are not considered to be significant problems for amino acids solvents. The precipitation of CO2 loaded amino acid salts is thought to be a good pathway for increasing CO2 loading capacity and cutting desorption energy costs if well-controlled. It is recommended that more detailed research on amino acid degradation and overall process energy costs is conducted. Overall, amino acid solvents are recognised as promising potential solvents for carbon dioxide capture.
    Recent advances in polymeric membranes for CO2 capture
    Yang Han, W. S. Winston Ho
    2018, 26(11):  2238-2254.  doi:10.1016/j.cjche.2018.07.010
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    Membrane and membrane process have been considered as one of the most promising technologies for mitigating CO2 emissions from the use of fossil fuels. In this paper, recent advances in polymeric membranes for CO2 capture are reviewed in terms of material design and membrane formation. The selected polymeric materials are grouped based on their gas transport mechanisms, i.e., solution-diffusion and facilitated transport. The discussion of solution-diffusion membranes encompasses the recent efforts to shift the upper bound barrier, including the enhanced CO2 solubility in several rubbery polymers and novel methods to construct shape-persisting macromolecules with unprecedented sieving ability. The carrier-bearing facilitated transport membranes are categorized based on the specific CO2-carrier chemistry. Finally, opportunities and challenges in practical applications are also discussed, including post-combustion carbon capture (CO2/N2), hydrogen purification (CO2/H2), and natural gas sweetening (CO2/CH4).
    Recent developments in aqueous ammonia-based post-combustion CO2 capture technologies
    Hai Yu
    2018, 26(11):  2255-2265.  doi:10.1016/j.cjche.2018.05.024
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    Aqueous ammonia (NH3) is a promising alternative solvent for the capture of industrial CO2 emissions, given its high chemical stability and CO2 removal capacity, and low material costs and regeneration energy. NH3 also has potential for capturing multiple flue gas components, including NOx, SOx and CO2, and producing value-added chemicals. However, its high volatility and low reactivity towards CO2 limit its economic viability. Considerable efforts have been made to advance aqueous NH3-based post-combustion capture technologies in the last few years:in particular, General Electric's chilled NH3 process, CSIRO's mild-temperature aqueous NH3 process and SRI International's mixed-salts (NH3 and potassium carbonate) technology. Here, we review these research activities and other developments in the field, and outline future research needed to further improve aqueous NH3-based CO2 capture technologies.
    Recent advances on the reduction of CO2 to important C2+ oxygenated chemicals and fuels
    Jiachen Li, Liguo Wang, Yan Cao, Chanjuan Zhang, Peng He, Huiquan Li
    2018, 26(11):  2266-2279.  doi:10.1016/j.cjche.2018.07.008
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    The chemical utilization of CO2 is a crucial step for the recycling of carbon resource. In recent years, the study on the conversion of CO2 into a wide variety of C2+ important chemicals and fuels has received considerable attention as an emerging technology. Since CO2 is thermodynamically stable and kinetically inert, the effective activation of CO2 molecule for the selective transformation to target products still remains a challenge. The welldesigned CO2 reduction route and efficient catalyst system has imposed the feasibility of CO2 conversion into C2+ chemicals and fuels. In this paper, we have reviewed the recent advances on chemical conversion of CO2 into C2+ chemicals and fuels with wide practical applications, including important alcohols, acetic acid, dimethyl ether, olefins and gasoline. In particular, the synthetic routes for C-C coupling and carbon chain growth, multifunctional catalyst design and reaction mechanisms are exclusively emphasized.
    Recent advances on the membrane processes for CO2 separation
    Jiayou Xu, Hongyu Wu, Zhi Wang, Zhihua Qiao, Song Zhao, Jixiao Wang
    2018, 26(11):  2280-2291.  doi:10.1016/j.cjche.2018.08.020
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    Membrane separation technology has popularized rapidly and attracts much interest in gas industry as a promising sort of newly chemical separation unit operation. In this paper, recent advances on membrane processes for CO2 separation are reviewed. The researches indicate that the optimization of operating process designs could improve the separation performance, reduce the energy consumption and decrease the cost of membrane separation systems. With the improvement of membrane materials recently, membrane processes are beginning to be competitive enough for CO2 separation, especially for postcombustion CO2 capture, biogas upgrading and natural gas carbon dioxide removal, compared with the traditional separation methods. We summarize the needs and most promising research directions for membrane processes for CO2 separation in current and future membrane applications. As the time goes by, novel membrane materials developed according to the requirement proposed by process optimization with increased selectivity and/or permeance will accelerate the industrialization of membrane process in the near future. Based on the data collected in a pilot scale test, more effort could be made on the optimization of membrane separation processes. This work would open up a new horizon for CO2 separation/Capture on Carbon Capture Utilization and Storage (CCUS).
    Recent progress of amine modified sorbents for capturing CO2 from flue gas
    Xinglei Zhao, Qian Cui, Baodeng Wang, Xueliang Yan, Surinder Singh, Feng Zhang, Xing Gao, Yonglong Li
    2018, 26(11):  2292-2302.  doi:10.1016/j.cjche.2018.04.009
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    Under the Paris agreement, China has committed to reducing CO2 emissions by 60%-65% per unit of GDP by 2030. Since CO2 emissions from coal-fired power plants currently account for over 30% of the total carbon emissions in China, it will be necessary to mitigate at least some of these emissions to achieve this goal. Studies by the International Energy Agency (IEA) indicate CCS technology has the potential to contribute 14% of global emission reductions, followed by 40% of higher energy efficiency and 35% of renewable energy, which is considered as the most promising technology to significantly reduce carbon emissions for current coal-fired power plants. Moreover, the announcement of a Chinese national carbon trading market in late 2017 signals an opportunity for the commercial deployment of CO2 capture technologies.
    Currently, the only commercially demonstrated technology for post-combustion CO2 capture technology from power plants is solvent-based absorption. While commercially viable, the costs of deploying this technology are high. This has motivated efforts to develop more affordable alternatives, including advanced solvents, membranes, and sorbent capture systems. Of these approaches, advanced solvents have received the most attention in terms of research and demonstration. In contrast, sorbent capture technology has less attention, despite its potential for much lower energy consumption due to the absence of water in the sorbent. This paper reviews recent progress in the development of sorbent materials modified by amine functionalities with an emphasis on material characterization methods and the effects of operating conditions on performance. The main problems and challenges that need to be overcome to improve the competitiveness of sorbent-based capture technologies are discussed.
    Recent developments and consideration issues in solid adsorbents for CO2 capture from flue gas
    Lijuan Nie, Yuanyuan Mu, Junsu Jin, Jian Chen, Jianguo Mi
    2018, 26(11):  2303-2317.  doi:10.1016/j.cjche.2018.07.012
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    The increase in energy demand caused by industrialization leads to abundant CO2 emissions into atmosphere and induces abrupt rise in earth temperature. It is vital to acquire relatively simple and cost-effective technologies to separate CO2 from the flue gas and reduce its environmental impact. Solid adsorption is now considered an economic and least interfering way to capture CO2, in that it can accomplish the goal of small energy penalty and few modifications to power plants. In this regard, we attempt to review the CO2 adsorption performances of several types of solid adsorbents, including zeolites, clays, activated carbons, alkali metal oxides and carbonates, silica materials, metal-organic frameworks, covalent organic frameworks, and polymerized high internal phase emulsions. These solid adsorbents have been assessed in their CO2 adsorption capacities along with other important parameters including adsorption kinetics, effect of water, recycling stability and regenerability. In particular, the superior properties of adsorbents enhanced by impregnating or grafting amine groups have been discussed for developing applicable candidates for industrial CO2 capture.
    CO2 absorption into a phase change absorbent: Water-lean potassium prolinate/ethanol solution
    Yangyang Bian, Shufeng Shen
    2018, 26(11):  2318-2326.  doi:10.1016/j.cjche.2018.02.022
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    Phase change solvents are attractive energy-efficient absorbents for carbon dioxide (CO2) capture due to CO2-rich phase formation. Potassium prolinate + water + ethanol (ProK/W/Eth) solution has shown good capture characteristics as a promising one in our previous work. In this work, absorption rate of CO2, solubility of N2O, and heat of absorption for ProK/W/Eth solution were investigated using a stirred cell reactor and a CPA201 reaction calorimeter and these results were also compared with the aqueous ProK and 30 mass% MEA solutions. Using ethanol as a solvent can substantially increase the CO2 physical solubility and the absorption rate of CO2 in ProK/W/Eth solutions is far higher than that in aqueous 30 mass% MEA solutions especially at a low CO2 loading range. Solid precipitation, obtained from the liquid-to-solid phase change absorption, was analyzed by 13C NMR and DSC-TGA. The enthalpy change for ProK/W/Eth solutions at various CO2 loading was also discussed.
    Modelling of a post-combustion carbon dioxide capture absorber using potassium carbonate solvent in Aspen Custom Modeller
    Yue Wu, Fan Wu, Guoping Hu, Nouman R. Mirza, Geoffrey W. Stevens, Kathryn A. Mumford
    2018, 26(11):  2327-2336.  doi:10.1016/j.cjche.2018.06.005
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    The process models for an equilibrium CO2 absorber and a rate based CO2 absorber using potassium carbonate (K2CO3) solvents were developed in Aspen Custom Modeller (ACM) to remove CO2 from a flue gas. The process model utilised the Electrolyte Non-Random Two Liquid (ENRTL) thermodynamic model and various packing correlations. The results from the ACM equilibrium model shows good agreement with an inbuilt Aspen Plus® model when using the same input conditions. By further introducing a Murphree efficiency which is related to mass transfer and packing hydraulics, the equilibrium model can validate the experimental results from a pilot plant within a deviation of 10%. A more rigorous rate based model included mass and energy flux across the interface and the enhancement effect resulting from chemical reactions. The rate based model was validated using experimental data from pilot plants and was shown to predict the results to within 10%. A parametric sensitivity analysis showed that inlet flue gas flowrate and K2CO3 concentration in the lean solvent has significant impact on CO2 recovery. Although both models can provide reasonable predictions based on pilot plant results, the rate based model is more advanced as it can explain mass and heat transfer, transport phenomena and chemical reactions occurring inside the absorber without introducing an empirical Murphree efficiency.
    Mass transfer correlations for membrane gas-solvent contactors undergoing carbon dioxide desorption
    Colin A. Scholes, Shufeng Shen
    2018, 26(11):  2337-2343.  doi:10.1016/j.cjche.2018.05.005
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    Membrane gas-solvent contactors are a hybrid technology combining solvent absorption with membrane gas separation, which demonstrates potential for CO2 capture through the ability of the membrane to rigidly control the mass transfer area. Membrane contactors have been successfully demonstrated for CO2 absorption, and there is strong research interest in using membrane contactors for the complimentary CO2 desorption process to regenerate the solvent. However, understanding and modelling the various stages of mass transfer in the desorption process is less well-known, given the existing mass transfer correlations had been developed from absorption experiments. Hence, mass transfer correlations for membrane contactors are reviewed here, and their appropriateness for desorption analysed. This is achieved through simulating CO2 desorption through a membrane contactor from loaded 30wt% monoethanolamine solvent to enable comparison of the correlations. It was found that the most cited correlations by Yang and Cussler were valid for shell side parallel flow, while that of Kreith and Black was viable for shell side cross flow. A limitation of all of these correlations is that they assume single phase flow on both sides of the membrane; however, the high temperature of CO2 desorption can lead to partial solvent vaporisation and hence two phases present on one side of the membrane contactor during desorption. A mass transfer correlation is established here for two phase parallel flow on the shell side of a membrane contactor, based on experimental results for three composite and one asymmetric hollow fibre membrane contactors stripping CO2 from loaded MEA at 105-108℃. This correlation is comparable to that reported in the literature for mass transfer in other two phase systems, but differs from the standard format for membrane contactors in terms of the exponent on the dimensionless Schmidt and Reynolds numbers.
    Carbon deposition and catalytic deactivation during CO2 reforming of CH4 over Co/MgO catalyst
    Jianwei Li, Jun Li, Qingshan Zhu
    2018, 26(11):  2344-2350.  doi:10.1016/j.cjche.2018.05.025
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    The deactivation mechanism of Co/MgO catalyst for the reforming of methane with carbon dioxide was investigated. The conversion of CH4 displayed a significant decrease in the initial stage caused by carbon deposition. There were two types of cokes, carbon nanotubes (CNTs) and carbon nano-onions (CNOs). The number of the CNO layers that coated on the surface of Co nanoparticles (NPs) increased rapidly in the initial reforming time, which was responsible for the deactivation of the Co/MgO catalyst. The deposition of CNOs was attributed to the oxidation of Co NPs. Therefore, the deactivation of the Co/MgO catalyst was originated from the first oxidization of the Co NPs into Co3O4 by O species (OH intermediate, CO2, H2O) during the reforming reaction, which accelerates the formation of coke that blocked the active metal, thus led to catalyst deactivation.
    The CO2 absorption and desorption performance of the triethylenetetramine + N,N-diethylethanolamine + H2O system
    Yaoyao Li, Changjun Liu, Richard Parnas, Yingying Liu, Bin Liang, Houfang Lu
    2018, 26(11):  2351-2360.  doi:10.1016/j.cjche.2018.04.014
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    Post-combustion CO2 capture (PCC) process faces significant challenge of high regeneration energy consumption. Biphasic absorbent is a promising alternative candidate which could significantly reduce the regeneration energy consumption because only the CO2-concentrated phase should be regenerated. In this work, aqueous solutions of triethylenetetramine (TETA) and N,N-diethylethanolamine (DEEA) are found to be efficient biphasic absorbents of CO2. The effects of the solvent composition, total amine concentration, and temperature on the absorption behavior, as well as the effect of temperature on the desorption behavior of TETA-DEEA-H2O system were investigated. An aqueous solution of 1 mol·L-1 TETA and 4 mol·L-1 DEEA spontaneously separates into two liquid phases after a certain amount of CO2 is absorbed and it shows high CO2 absorption/desorption performance. About 99.4% of the absorbed CO2 is found in the lower phase, which corresponds to a CO2 absorption capacity of 3.44 mol·kg-1. The appropriate absorption and desorption temperatures are found to be 30℃ and 90℃, respectively. The thermal analysis indicates that the heat of absorption of the 1 mol·L-1 TETA and 4 mol·L-1 DEEA solution is -84.38 kJ·(mol CO2)-1 which is 6.92 kJ·(mol CO2)-1 less than that of aqueous MEA. The reaction heat, sensible heat, and the vaporization heat of the TETA-DEEA-H2O system are lower than that of the aqueous MEA, while its CO2 capacity is higher. Thus the TETA-DEEA-H2O system is potentially a better absorbent for the post-combustion CO2 capture process.
    Ni/bentonite catalysts prepared by solution combustion method for CO2 methanation
    Yuexiu Jiang, Tongxia Huang, Lihui Dong, Zuzeng Qin, Hongbing Ji
    2018, 26(11):  2361-2367.  doi:10.1016/j.cjche.2018.03.029
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    A 20 wt% Ni/bentonite catalyst was prepared by a solution combustion synthesis (SCS), which exhibited higher activity for the CO2 methanation than that of an impregnation method (IPM), and the catalyst prepared by SCS showed a CO2 conversion of 85% and a CH4 selectivity of 100% at 300℃, atmospheric pressure, and 3600 ml·(g cat)-1·h-1, and the catalyst exhibited stable within a 110-h reaction. The results showed higher metallic Ni dispersion, smaller Ni particle size, larger specific surface area and lower reduction temperature in the Ni/bentonite prepared by SCS than that of IPM. And the Ni/bentonite prepared by the SCS moderated the interaction between NiO and bentonite.
    High-efficiency and pollution-controlling in-situ gasification chemical looping combustion system by using CO2 instead of steam as gasification agent
    Zhe Shen, Zhiyu Huang
    2018, 26(11):  2368-2376.  doi:10.1016/j.cjche.2018.03.016
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    Using CO2 as gasification agent instead of steam in in-situ coal gasification chemical looping combustion (iG-CLC) power plant can eliminate energy consumption for steam generation, thus obtaining higher system efficiency. In this work, a comparative study of iG-CLC power plant using steam and CO2 as gasification agent is concentrated on. The effects of steam to carbon ratio (S/C) and CO2 to carbon ratio (CO2/C) on the fuel reactor temperature, char conversion, syngas composition and CO2 capture efficiency are separately investigated. An equilibrium carbon conversion of 88.9% is achieved in steam-based case as S/C ratio increases from 0.7 to 1.1, whereas a maximum conversion of 84.2% is obtained in CO2-based case with CO2/C ranging from 0.7 to 1.1. Furthermore the effects of oxygen carrier to fuel ratio (φ) on system performances are investigated. Increasing φ from 1.0 to 1.4 helps to achieve char conversion from 75.9% to 88.9% in steam-based case, by contrast the char conversion can achieve 66.3%-84.2% in CO2-based case within the same φ range. In terms of iG-CLC power plant, recycling partial CO2 to the fuel reactor improves the overall performance. Approximately 3.9% of net power efficiency are increased in CO2-based plant, from steam-based plant. Higher CO2 capture efficiency and lower CO2 emission rate are observed in CO2-gasified iG-CLC power plant, expecting to be 90.63% and 85.18 kg·MW-1·h-1, respectively.
    Supported ionic liquid sorbents for CO2 capture from simulated flue-gas
    Jiajia Ren, Zheng Li, Yifeng Chen, Zhuhong Yang, Xiaohua Lu
    2018, 26(11):  2377-2384.  doi:10.1016/j.cjche.2018.04.025
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    Supported ionic liquid (IL) sorbents for CO2 capture were prepared by impregnating tetramethylammonium glycinate ([N1111] [Gly]) into four types of porous materials in this study. The CO2 adsorption behavior was investigated in a thermogravimetric analyzer (TGA). Among them, poly(methyl methacrylate) (PMMA)-[N1111] [Gly] exhibits the best CO2 adsorption properties in terms of adsorption capacity and rate. The CO2 adsorption capacity reaches up to 2.14 mmol·g-1 sorbent at 35℃. The fast CO2 adsorption rate of PMMA-[N1111] [Gly] allows 60 min of adsorption equilibrium time at 35℃ and much shorter time of 4 min is achieved at 75℃. Further, Avrami's fractional-order kinetic model was used and fitted well with the experiment data, which shows good consistency between experimental results and theoretical model. In addition, PMMA-[N1111] [Gly] remained excellent durability in the continuous adsorption-desorption cycling test. Therefore, this stable PMMA-[N1111] [Gly] sorbent has great potential to be used for fast CO2 adsorption from flue-gas.
    Impregnation of carbonaceous nanofibers into glassy polymer-based composite membrane for CO2 separation
    Pannir Selvam Murugiah, Pei Ching Oh, Kok Keong Lau
    2018, 26(11):  2385-2390.  doi:10.1016/j.cjche.2018.05.023
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    The development of defect-free composite membrane (CM) is often challenging due to poor dispersion and distribution of filler particles in the polymer matrix. Despite the attractive physicochemical properties and gas separation performance of carbon nanotube (CNT) based CM, CNT displayed poor dispersion characteristics in most polymer matrix domain. Instead of incorporating CNT, a viable alternative, carbon nanofiber (CNF) which exhibits similar properties as CNT, but improved dispersion quality in the polymer matrix is found. In this work, CNF particles were incorporated in poly(2,6-dimethyl-1,4-phenylene oxide) (PPOdm) polymer continuous phase for CM development. The optimum gas separation performance of the PPOdm-CNF CM (11.25 at 197.02 barrer of CO2 permeability) was obtained at 3 wt% of CNF loading. Compared to pristine PPOdm membrane, CO2 permeability and CO2/CH4 selectivity of PPOdm-3 wt% CNF CM were enhanced by 180% and 55%, respectively. At 3 wt% CNF loading, the filler particles were dispersed and distributed more homogenously, in which no obvious CNF agglomeration was observed. In addition, the incorporation of CNF particles also enhanced the mechanical and thermal properties of the resultant CM.