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To remove elemental mercury (Hg 0 ) in chlorine-free coal combustion flue gas efficiently, CuCl 2 loaded CeO 2 -ZrO 2 sorbents (denoted as CC/CZ) were developed. In this way, the abundant Cl and affluent active chemical adsorbed oxygen (O∗) on the surface of the sorbent would be combined and made full use for Hg 0 removal. XRD, XPS, SEM, Raman, TG, and N 2 adsorption/desorption were employed to characterize the sorbents. Hg 0 removal behaviors over CC/CZ were studied using a lab-scale fixed-bed reactor. The sorbent with optimal loading 6% CuCl 2 exhibited superior and stable performances (89.6–97.1%) within a much wider applicable temperature range (100–300 °C) in the absence of HCl. The results also indicated that 6%CC/CZ exhibit very good performance at lower temperature (100–200 °C). The interaction between Cl and chemical adsorbed oxygen was observed and probably responsible for its superior Hg 0 removal performance. XPS results of the fresh, thermal-treated, and spent 6% CuCl 2 /CZ may explain the Hg 0 oxidation process. Hg 0 was mainly oxidized by the generated active chlorine species and the main reaction product was HgCl 2 . The active chlorine species were formed due to the interaction between chlorine and chemical adsorbed oxygen species. [ABSTRACT FROM AUTHOR]

A novel class of magnetically responsive catalytic sorbents are proposed and synthesized with a potential application to simultaneous removal of Hg 0 and NO at low temperature from the flue gases of coal-fired power plants. The catalytic sorbent consists of magnetite (Fe 3 O 4 ), molecular sieve (HZSM-5), supported silver nanoparticles and catalytically reactive component of V 2 O 5 . Each of these materials provides a unique function for the purpose of capturing mercury, removing NO, and separation from fly ash. After separation from the fly ash, the spent sorbent can be regenerated and reused, leaving an uncontaminated fly ash product. The successful synthesis as designed was confirmed and properties of the catalytic sorbent were characterized by several methods. The synthesized catalytic sorbent was able to completely capture Hg 0 at 150 °C with a capture capacity as high as 32.4 μg·g −1 , while achieving 84% removal of NO at 150 °C. Even at a relatively high space velocity, the catalytic sorbent achieved 97% Hg 0 and 80% NO removal simultaneously, while maintaining a good stability after repetitive regeneration and recycle. The magnetically responsive catalytic composite was shown to be a promising candidate for multi-pollutant emission control from coal-fired power plants. [ABSTRACT FROM AUTHOR]

A novel KI modified bentonite supported by starch sorbent (B–S–I) was synthesized and the comparison between B–S–I and the traditional KI modified bentonite sorbent (B–I) in Hg 0 removal was performed under simulated flue gas. The results showed that B–S–I exhibited more remarkable Hg 0 removal ability than B–I. This was because B–S–I demonstrated more excellent iodine uptake capacity due to the reaction between iodine and the starch loaded on B–S–I. I 2 was validated to exist in B–S–I due to the KI oxidation by air and starch–iodine complex could be formed. The starch–iodine complex was considered to have the ability to provide I 2 for Hg 0 to form iodated mercuric compounds. O 2 promoted Hg 0 removal while H 2 O inhibited them. B–S–I exhibited a higher extent of Hg 0 removal than B–I in the presence of O 2 because more KI adsorbed by B–S–I could be oxidized to I 2 by O 2 . SO 2 showed distinct effects on the two sorbents and mainly exhibited promotable for B–S–I. The starch loaded on B–S–I was considered to greatly promote the surface reactivity and more sulfur groups could be formed, which favored the chemisorption of Hg 0 . Increasing temperature in the range of 80–140 °C caused a rise in Hg 0 removal. Bentonite serving as support showed a good reusability to resynthesize B–S–I for Hg 0 removal. The major product was assumed to be HgI 2 . A reaction scheme of B–S–I that could explain its superiority to B–I was presumed based on the characterizations and adsorption study. [ABSTRACT FROM AUTHOR]

• Impregnated layer solution combustion contributes to enhancing CO 2 capture stability. • CaZrO 3 exhibits excellent property on improving CO 2 capture stability of limestone. • 10 wt% of CaZrO 3 sufficiently provides effective structural stability for limestone. Calcium looping is an effective post-combustion technology for CO 2 separation from flue gas due to its low-cost and highly accessible sorbent raw material (i.e., limestone). However, limestone easily occurs serious sintering during multiple high-temperature carbonation/calcination cycles. Here, three types of modification mode, including acetic acid acidification, wet and dry solution-impregnated cigarette butts-assisted combustion methods, were adopted to enhance the cyclic stability of limestone. The impregnated layer solution combustion mode is superior to acid acidification, which is mainly ascribed to the heat released from the combustion of cigarette butt playing the role of thermal pretreatment, thereby stabilizing the pore structure of limestone-derived sorbents. Incorporating different inert supports can further enhance the cyclic stability of limestone-derived sorbents synthesized by wet solution-impregnated cigarette butts-assisted combustion. The effectiveness of several inert supports in improving the cyclic stability of limestone-derived adsorbents is listed as follows: CaZrO 3 > MgO > Ca 12 Al 14 O 33 > CaMn 2 O 4. Moreover, the loading content of CaZrO 3 within limestone-derived sorbents was further optimized, and it was found that 10 wt% of CaZrO 3 sufficiently provides stable framework to inhibit high-temperature sintering (∼0.525 g-CO 2 /g-sorbent after 20 cycles). The uniformly dispersed CaZrO 3 support at the nanocrystalline scale effectively inhibiting sintering is responsible for the excellent cyclic CO 2 capture capability of CaZrO 3 -supported sorbents. [ABSTRACT FROM AUTHOR]

Li 4 SiO 4 sorbents for high-temperature CO 2 removal have drawn extensive attention owing to their potential application in carbon capture and storage (CCS). The major challenge in the application lies in the poor CO 2 capture performance under realistic conditions of low CO 2 concentrations, owing to the dense structure and poor porosity. In this work, Li 4 SiO 4 sorbents were prepared with porous micromorphologies and large contact areas using a variety of organometallic Li-precursors, achieving fast CO 2 sorption kinetics, high capacity and excellent cyclic stability at a low CO 2 concentration (15 vol%). It was found that a high conversion of ~ 74% was maintained for pure Li 4 SiO 4 even after 100 sorption/desorption cycles. Moreover, by doping with Na 2 CO 3 to reduce the CO 2 diffusion resistance, the conversion of the sorbent was further enhanced to 93.2%. The enhancement mechanism of alkali carbonate have been proven here to be ascribed to the formation of the eutectic melt of Li/Na carbonates, the existence and function of which has been confirmed in this study. [ABSTRACT FROM AUTHOR]

[Display omitted] • Direct solar-driven CaL can eliminate the adverse influence of coal combustion. • Dolomite-derived sorbents synthesized by cigarette butt-assisted combustion method. • Unitary or binary doping of optical absorption enhanced elements boosts solar absorbance. Calcium looping (CaL) is a promising technology for CO 2 capture owing to the widespread applicability and low-cost CaO-based sorbents. However, the SO 2 and ash from coal combustion in O 2 /CO 2 atmosphere for CaO regeneration is prone to cause rapid degradation for CaO-based sorbent. Hereby, a direct solar-driven CaL system is proposed to eliminate the adverse influence of coal combustion on CaO-based sorbent. Different unitary Mn-doped and binary-doped (Mn/Fe-, Mn/Cu- and Mn/Co-doped) dolomite-derived sorbents were synthesized by cigarette butt-assisted combustion method. The higher Mn doping ratio, the higher solar absorptance for unitary Mn-doped sorbent due to the gradually deepened blackness of the sample. Comprehensively considering the solar absorptance and CO 2 capture performance, the unitary Mn-doped sorbent (Ca&Mg: Mn=100:10) is an optimal candidate, which has a solar absorptance of 63.6 % and a carbonation conversion of 64.3 % in the 20th cycle. Compared with the unitary Mn-doped sorbent (Ca&Mg: Mn=100:10), the binary-doped sorbent (Ca&Mg: Mn: Fe=100:5:5) exhibits a comparable CO 2 capture capacity and a higher solar absorptance of 76.7 %. More importantly, the binary-doped sorbent (Ca&Mg: Mn: Fe=100:5:5) possesses the markedly faster CO 2 capture rate in the early carbonation stage due to the increased lattice defect of CaO. [ABSTRACT FROM AUTHOR]

[Display omitted] • Zr-incorporated, CaO-based sorbents were produced by cigarette butt-assisted combustion. • Cigarette butt-assisted combustion synthesis method is facile and time-saving. • Combustion temperature closely affects CO 2 capture performance of synthetic sorbents. • Higher Zr-based support contents contribute to the superior cyclic stability. Highly efficient and stable Zr-incorporated CaO-based sorbents were synthesized using a facile, cigarette butt-assisted combustion synthesis (CAC) method. Comparative investigation of CAC method with two common synthesis methods (i.e., wet-mixing, sol–gel) on producing CaO-based sorbents was conducted. The sorbents synthesized by the CAC and sol–gel methods exhibit superior cyclic CO 2 capture capability compared to wet-mixing. More importantly, the CAC belongs to impregnated layer solution combustion synthesis and takes markedly shorter time compared to sol–gel, possessing the potential of scaled-up preparation. The optimization of combustion temperature and incorporation ratio of Zr-based support on synthesis of CaO-based sorbents by CAC method was further conducted. The proper combustion temperature selected to synthesize Zr-incorporated CaO-based sorbents using CAC method is 750 °C. Too high or low combustion temperature may result in unsatisfactory pore structure of synthetic CaO-based sorbents because of excessive sintering or generating in-situ CaCO 3 , respectively. The synthetic CaO-based sorbents with 25 wt% of ZrO 2 exhibit the outstanding CO 2 capture performance (CaO carbonation conversion of 63.8% after 17 cycles) due to the generation of extensive CaZrO 3 grains acting as the inert skeleton. Additionally, the combination of cigarette butt-assisted combustion and graphite-moulding can prepare Zr-incorporated CaO-based pellets with desirable practicality. [ABSTRACT FROM AUTHOR]

The traditional development of CaO-based sorbents to be used in calcium looping process (CLP) consists of two steps: producing powders with improved cyclic performance by sorbent modification, followed by the subsequent granulation. However, this traditional routine is complicated and energy-consuming. Moreover, the improved performance would be weakened again during the granulation process. Hence, the implement of the modification and granulation within one step to produce CaO-based sorbents is of significant importance for CLP. This work, for the first time, proposes a simple and facile gel-casting technique to achieve the one-step synthesis of highly-efficient CaO-based sorbents pellets. The pellets modified with microcrystalline cellulose (CaO-MC) achieved considerable CO 2 capture capacity of ~ 0.48 g CO 2 /g sorbent at the 25th cycle under the mild calcination condition and retained relatively excellent performance of 0.41 g/g over 25 moderate cyclic tests, higher than those of the unmodified pellets (CaO-pellet). The decomposition of microcrystalline cellulose in CaO-MC does not change the cubic crystal structure of CaO, but brings more pores that contribute a lot to its superior CO 2 capture performance. Moreover, all synthesized pellets possess good attrition resistance, indicating the applicability of the prepared pellets to the application in CLP. [ABSTRACT FROM AUTHOR]

A screening of inert solid supports as metal skeletons of CaO-based sorbents was conducted in this work, aiming to provide the basis and guideline for the selection of inert solid refractories to produce high temperature CO 2 capture sorbent. We studied 12 different refractories including Al-, Ti-, Mn-, Mg-, Y-, Si-, La-, Zr-, Ce-, Nd-, Pr- and Yb-based supports, among which Yb and Pr are newly introduced ones. The sorbents were synthesized using the same wet-mixing method, by which the inert supports could be well dispersed among the ultra-fine active specie of CaO/CaCO 3 particles to fully play the role of frameworks for sintering resistance. The sorbents stabilized by these inert supports were also cyclically tested under the same conditions. Y- and Al-based supports were found to exhibit much superior cyclic performance than the other supports. Mn-, Mg-, La-, Yb- and Nd-based supports are also good candidates, whereas the other ones containing Ti-, Ce-, Zr-, Si- and Pr-based supports show less effectiveness. The melting point of the inert support and surface area of the synthetic sorbents are found to be the key factors to affect the sorbent performance. [ABSTRACT FROM AUTHOR]

Li 4 SiO 4 sorbents have exhibited promising prospects for high-temperature CO 2 capture. However, conventional Li 4 SiO 4 using solid-state reaction method usually exhibits dense structures with barren porosity, limiting the CO 2 sorption. To solve this problem, a sol-mixing method using organometallic lithium precursors was employed to produce 'new' Li 4 SiO 4 sorbents with improved CO 2 sorption performance. The obtained Li 4 SiO 4 from lithium salicylate precursor exhibited enhanced specific surface area and modified micromorphology compared to the conventional Li 4 SiO 4. The morphology showed that the 'new' Li 4 SiO 4 possessed many fluff-like folds on the surface, in comparison with the smooth surfaces of conventional sorbent. As a result, the 'new' sorbent exhibited CO 2 uptake of ~0.15 g/g, which is more than three times as high as that of the conventional one. Furthermore, the CO 2 uptake was further enhanced to 0.32 g/g by K 2 CO 3 doping. After granulation, the pellets also presented good CO 2 sorption performance as well as excellent mechanical strength for practical applications. Generally, the good sorption performance and excellent mechanical strength demonstrated the effectiveness of sol-mixing method and lithium salicylate as precursors for the production of efficient Li 4 SiO 4 sorbents. • Li 4 SiO 4 was prepared using lithium salicylate precursor via sol-mixing method. • The new sorbent exhibited the morphology with many fluff-like folds on the surface. • The CO 2 uptake of the new sorbent was over 3 times that of the conventional Li 4 SiO 4. • The granulated sorbents showed both good sorption performance and mechanical strength. [ABSTRACT FROM AUTHOR]