Zhongli He,Bing Song,Cai Liang,Bin Liu,Zhirui Ma,Keliang Pang,Jiangang Yang
Concerns about arsenic emission issues are growing as the arsenic discharged from coal-fired power plants seriously endangers the ecological environment and public health. The gas-phase arsenic capture by a CaO–Ca12Al14O33 synthetic sorbent at 1000–1200 °C in the simulated flue gas was conducted, with the influence of the addition ratio of Ca12Al14O33, temperature, retention time, and acid gases NO/SO2 considered in the study. The results indicated that the synthetic sorbent containing 15 wt % Ca12Al14O33 (Ca85Al15) exhibited much better arsenic adsorption performance than CaO, which was ascribed to the greatly strengthened sintering resistance of CaO particles by adding Ca12Al14O33, enabling arsenic adsorption and chemical reactions. Both the increasing temperature and retention time facilitated arsenic adsorption by Ca85Al15, and the hypertoxic arsenic vapor (As3+) was converted into arsenate (Ca3(AsO4)2) with less toxicity. In the presence of NO, the arsenic capture was gradually suppressed with increasing retention time. On the other hand, SO2 could slightly facilitate the capture of arsenic at 1000–1100 °C for 10 min; nevertheless, due to the formation of Ca4Al6O12SO4, the promotion effect was inhibited at a higher temperature and a longer retention time. In general, the study provided a basis for developing highly efficient solid sorbents toward controlling arsenic vapor emission derived from coal combustion, and the appropriate conditions for arsenic capture were at 1000–1100 °C.
Chunxiao Zhang,Yingjie Li,Zirui He,Jianli Zhao,Dong Wang
Herein, a hollow microtubular Fe/Mn-promoted CaO-Ca 12 Al 14 O 33 bi-functional material was prepared by the bio-template method and used for H 2 production from sorption enhanced water gas shift (SEWGS). The microtubular Fe/Mn-promoted CaO-Ca 12 Al 14 O 33 exhibits excellent CO 2 capture and H 2 production performance in SEWGS/regeneration cycles. The stable hollow microtubular structure improves available adsorption and catalytic sites in Fe/Mn-promoted CaO-Ca 12 Al 14 O 33 for CO 2 capture and H 2 production. Mn addition improves CO 2 affinity capacity of the microtubular material. The Fe-Mn interaction increases redox ability of Fe 3+ /Fe 3+, 2+ , which promotes CO conversion. Moreover, the formed Ca 2 Fe 2 O 5 and Ca 2 MnO 4 both increase oxygen vacancies to promote catalytic activity of the microtubular material for WGS and its CO 2 capture capacity. The CO conversions for the microtubular material with the Fe/Mn/Al/Ca molar ratio= 10/2/10/100 are 98.7% and 94.0% after 20 cycles under the mild and severe calcination conditions, respectively. The hollow microtubular bi-functional material shows good prospect for efficient H 2 production from SEWGS.
Co-gasification of biomass and waste plastics is a promising technology for H 2 production. In this work, Ni-CaO-Ca 12 Al 14 O 33 and Ni-CaO-MgO bi-functional materials were prepared from carbide slag for H 2 production in sorption-enhanced steam gasification experiments of cellulose/polyethylene mixtures. The H 2 production and CO 2 capture performances of Ni-CaO-Ca 12 Al 14 O 33 and Ni-CaO-MgO in sorption-enhanced steam gasification of cellulose/polyethylene were studied and compared. Density functional theory calculations, including the density of states, electron differential densities, and adsorption energies were performed to investigate the effect of supports on the stability and reactivity of Ni-CaO-based bifunctional materials at a microscopic level. The results exhibit that polyethene contributes to improving the H 2 production effectiveness of cellulose sorption-enhanced steam gasification, the optimum mass ratio of cellulose to polyethene is 0.5:0.5. The CO 2 capture capacity, H 2 yield, and H 2 concentration using Ni-CaO-Ca 12 Al 14 O 33 can be respectively 2.0, 2.6, and 1.4 times as high as those using Ni-CaO-MgO in the 20th cycle, which indicates the higher cyclic stability and catalytic activity of Ni-CaO-Ca 12 Al 14 O 33 . Density functional theory results also indicate that Ca 12 Al 14 O 33 can better retain the stable structure of Ni-CaO-based materials, which is consistent with the experimental results. Compared with MgO, Ca 12 Al 14 O 33 is a better framework for Ni-CaO-based bifunctional material for H 2 production in the sorption-enhanced steam gasification process.
Macroporous europium-doped Ca12Al14O33 (C12A7:Eu3+) was prepared via a sol–gel method followed by heat-treatment, and the crystal structure, luminescence performance and metal ion luminescence sensing of C12A7:Eu3+ were investigated and evaluated in detail. The process of the sol–gel method and heat-treatment promotes the formation of a single mayenite phase C12A7:Eu3+, and the Eu3+ ions are incorporated into the crystal lattice and replace the position of the Ca2+ ions without destroying the lattice structure of C12A7. The interconnected macropores not only increase the lighting area but also reduce the concentration quenching effect, leading to a significant enhance of luminescence intensity. The resultant macroporous C12A7:Eu3+ can be used as a luminescence performance sensor and displays the potential practical application for metal ion detection. The macroporous C12A7:Eu3+ sensor has a good response to Pb2+ ions, whose linear equation between concentration (CPb) and luminescence intensity (F) of (F0 − F)/F0 = 1.412 + 0.3428 log10(CPb) can be obtained.
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