摘要
近年来,温室效应以及由其引起的环境变化受到越来越多的关注,CO2的捕获、分离与封存成为遏制C02排放,减少大气中C02浓度的有效方法之一。Li4SiO4作为高温下(500℃-720℃)循环吸收CO2的优良吸收剂,用于化石燃料电厂及相关的密集C02排放源,具有很大的应用前景。因此,研究Li4SiO4的合成及其吸收-解吸CO2性能,在环境和经济领域具有重要的意义。
本论文以石英(SiO2)、正硅酸乙酯(TEOS, C8H20O4Si)和煤矸石作为硅源,以Li2CO3和LiOH·H2O为锂源,分别采用固相法、溶胶-凝胶法和水热法合成Li4SiO4,并研究了其在高温下的CO2吸收-解吸性能。以XRD、SEM、热分析(DSC-TG和DTA-TG)为表征和测试手段,对Li4SiO4的合成方法、反应动力学、样品形貌、粒度和吸收CO2性能等做了系统研究,具体分为如下四部分：
(1)以石英(Si02)和Li2CO3为原料,采用传统固相法,研究了原料配比(n(Li+):n(Si4+)=4:1-4.4:1)、反应温度(500-1000℃)、石英粒度(75-180μm,45-75μm, 38-45μm和小于38μm)对Li4SiO4合成的影响规律。发现石英粒径小于38μm时,在800℃煅烧4h可合成出纯Li4SiO4其C02最大吸收率为31.3wt%。
(2)将煤矸石进行煅烧、酸浸、洗涤、干燥等预处理后,所得产物与Li2CO3在800℃煅烧4h合成出Li4SiO4样品。煤矸石经过600℃煅烧等预处理后,所制样品的最大CO2吸收率最高,达到20.9wt%；而直接利用未经过预处理的煤矸石合成的样品,其最大CO2吸收率最低,仅为16.4wt%。
(3)以TEOS为硅源,在碱性条件下通过TEOS水解合成包裹于Li2CO3表面的Si02凝胶,将其在600℃、650℃和700℃煅烧6h后合成Li4SiO4。结果表明,经过700℃煅烧合成的Li4Si04,CO2的最大吸收率最高,达到了32.9wt%。
(4)以TEOS为硅源,LiOH·H2O为锂源,采用水热反应得到Li2SiO3和Li2CO3的复合粉体,再在700℃煅烧4h可合成出Li4SiO4。结果发现,当水热反应过程中添加CTAB时,所合成的Li4SiO4样品在低温时的CO2吸收率较高,但其C02最大吸收率较低(31.9wt%)；当不添加CTAB时,所得Li4SiO4样品的最大吸收率高达34.3wt%。
In recent years, the environment change which is resulted from greenhouse effect has attached more and more attention. CO2 capture and sequestration is an effective way to reduce its release to the atmosphere and curb the greenhouse effect. As an excellent adsorbent material for CO2 capture at high temperature(500℃-720℃), Li4SiO4 applied in the large stationary sources like fossil fired power stations and related industries has a promising future. Therefore, it is significant to investigate the synthesis and CO2 adsorption-desorption performance of Li4SiO4, especially in the area of environment and economy.
In this paper, quartz (SiO2), TEOS and coal gangue were chosen as silicon sources to synthesize Li4SiO4, while Li2CO3 and LiOH·H2O as lithium sources. X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermal analysis (DSC-TG and DTA-TG) were used as test and characterization methods. The method and kinetic process of synthesis, microstructure, particle size and CO2 adsorption capacities have been researched systematically. The whole process is divided into the following four parts:
(1) Quartz (SiO2) and Li2CO3 were used as raw materials to synthesize Li4SiO4, according to the traditional solid-state reaction. With different sintering temperatures (500℃-1000℃), different mixture ratios (n(Li+):n(Si4+)=4:1-4.4:1) and different particle sizes of quartz (75-180μm,45-75μm,38-45μm and below 38μm), Li4SiO4 samples were obtained. Using Li2CO3 and quartz below 38μm, pure Li4SiO4 was synthesized at 800℃for 4h. The maximum CO2 adsorption capacity of pure Li4SiO4 was up to 31.3wt%.
(2) Coal gangue firstly experienced pretreatment such as calcination activation, ultrasonic acid-leaching, filtration and water washing, then the dried solid products was used as the silica source to synthesize Li4SiO4 at 800℃for 4h. The CO2 adsorption results showed that the sample with pretreatment at 600℃had the largest adsorption capacity which was up to 20.9wt%. However, the sample synthesized directly with coal gangue showed the lowest CO2 adsorption capacity which was up to 16.4wt%.
(3) TEOS was used as the silica source to synthesize Li4SiO4 with sol-gel method, by which the precursor (LiCO3 coated by SiO2 gel) was obtained as a result of the hydrolysate of TEOS on the alkaline condition. At 600,650 and 700℃for 6h, the precursor was calcinated and the samples were obtained. The sample calcined at 700℃showed the largest adsorption capacity which was up to 32.9wt%.
(4) TEOS and LiOH·H2O were used as raw materials to synthesize Li4SiO4 by hydrothermal method. The composite powders of Li2SiO3 and Li2CO3 were obtained by hydrothermal method and they were calcined at 700℃for 4h to synthesize Li4SiO4. The CO2 adsorption results showed that samples added with CTAB had a rapid adsorption rate and the largest adsorption capacity reached to 31.9wt%. The sample added without CTAB had a relatively slow adsorption rate, while it owned a larger adsorption capacity which is up to 34.3wt%.
引文
[1]王明星,张仁健,郑循华.温室气体的源与汇[J].气候与环境研究,2000,5(1)：75～79
[2]徐世晓,赵新全,孙平等.温室效应及全球气候变暖[J].青海师范大学学报(自然科学版),2001,(4)：43-47.
[3]IPCC,2007:Climate Change 2007:Synthesis Report [R]. Contribution of Working Croups Ⅰ,Ⅱ and Ⅲ to the Fourth Assessment Report of the Intergovernment Panel on Climate Change [Core Writing Team, Pachauri, R.K. And Reisinger, A. (Eds.)]-IPCC Geneva. Switzerland, pp 104.
[4]Thomas Conway and Pieter Tans. NOAA/ESRL (www.esrl.noaa.gov/gmd/ccgg/trends/).
[5]巢青尘,陈文颖.碳捕获和存储技术综述及对我国的影响[J].地球科学进展,2006,21(3)：291～298.
[6]Yang H Q, Xu Z H, Fan M H et al. Progress in carbon dioxide separation and capture:A review[J]. J Environ Sci-China,2008,20 (1):14～27.
[7]王泽平,周涛,张记刚等.电厂二氧化碳捕捉技术对比研究[J].环境科学与技术,2011,34(11)：83～87.
[8]黄斌,刘练波,许世森.二氧化碳捕获和封存技术进展[J].中国电力,2007,40(3)：14-17.
[9]王琦,程易,吴昌宁等.新型节能CO2零排放工艺—化学循环燃烧技术[J].化学进展,2008,20(10)：1612-1620.
[10]吕碧洪,金佳佳,张莉.有机胺溶液吸收CO2的研究现状及进展[J],石油化工,2011,40(8)：803～809.
[11]Choi S, Drese J H, Jones C W. Adsorbent materials for carbon dioxide capture from large anthropogenic point sources[J]. ChemSusChem,2009,2 (9):796～854.
[12]Figueroa J D, Fout T, Plasynski S et al. Advances in CO2 capture technology-The U.S. Department of Energy's Carbon Sequestration Program[J]. Int J Greenh Gas Con,2008,2 (1):9-20.
[13]黄煜煜,李振山,蔡宁生.高温CO2吸附／吸收剂的研究进展[J].热能动力工程,2005,20(6)：557～561.
[14]李莉,袁文辉,韦超海.二氧化碳高温吸附剂及其吸附过程[J].化工进展,2006,25(8)：918-922.
[15]徐如人主编.分子筛及多孔材料化学[M].北京：科学出版社,2004.
[16]Aschenbrenner O, McGuire P, Alsamaq S et al. Adsorption of carbon dioxide on hydrotalcite-like compounds of different compositions [J]. Chem Eng Res Des,2011,89 (9A):1711～1721.
[17]任斌,考宏涛,郭涛等.基于钙基吸收剂吸收CO2的研究进展[J].化学工程,2011,39(9)：26～29.
[18]李青辉.CaO基高温CO2吸附剂研究[D].浙江：浙江大学,2009.
[19]Ortiz-Landeros J, L. Avalos-Rendon T, Gomez-Yanez C et al. Analysis and perspectives concerning CO2 chemisorption on lithium ceramics using thermal analysisfJ]. J Thenn Anal Calorim,2011, DOI:10.1007/s10973-011-2063-y.
[20]Nair B N, Burwood R P, Goh V J et al. Lithium based ceramic materials and membranes for high temperature CO2 separation[J]. Prog Mater Sci,2009,54(5):511～541.
[21]尹先升.锆酸锂材料的设计、合成及高温CO2吸附性能[D].上海：华东理工大学,2012.
[22]刘叶凤.高温二氧化碳吸附剂的合成及表征[D].浙江：浙江师范大学,2010.
[23]Nakagawa K, Ohashi T. A novel method of CO2 capture from high tempe[J]. J Electrochem Soc,1998,1 (4):1344～1346.
[24]Kato M, Yoshikawa S, Nakagawa K. Carbon dioxide absorption by lithium orthosilicate in a wide range of temperature and carbon dioxide concentrations [J]. J Mater Sci Lett,2002,21 (6):485～487.
[25]牛恺,尹邦跃.正硅酸锂陶瓷粉末合成研究[C].2006全国核材料学术交流会论文集.成都：中国核学会材料分会,2006：133-136.
[26]冯勇进,冯开明,罗天勇.正硅酸锂陶瓷粉末的合成[C].中国核科学技术发展报告-中国核科学2009年学术年会论文集.北京：中国核学会,2009：61-65.
[27]吕国强,阳书文,马文会等.Li4Si04回收CO2的实验研究[J].热能动力工程,2009,24(5)：644-647.
[28]Zagorowsky G M, Prikhodko G P, Ogenko V M et al. Investigation of kinetics solid-phase synthesis of lithium orthosilicate[J]. J Therm Anal Calorim,1999,55,699～705.
[29]丁铸,张鸣,刘鹏.高温条件下吸收CO2材料的研究[J].中国科技信息,2009,(11)：40～41.
[30]Pfeiffer H, Bosch P, Bulbulian S. Synthesis of lithium silicates [J]. J Nucl Mater,1998,257 (3):309～317.
[31]宋秀芹,陈汝芳,贾密英.溶胶-凝胶法合成Li4SiO4[J].应用化学,2000,17(3)：304-306.
[32]袁文辉,梁杰,李莉.Li4SiO4的合成表征及CO2吸附与模拟[J].化工进展,2009,28：306-309.
[33]梁杰.脱除烟道气中CO2, SO2和NOx高温吸附剂的研究即C02吸附模拟[D].广州：华南理工大学,2011.
[34]Chang C -C, Wang C C, Kumta P N. Chemical synthesis and characterization of lithium orthosilicate (Li4SiO4). Mater Design,2001,22 (7):617～623.
[35]王银杰,其鲁,江卫军.高温下硅酸锂吸收CO2的研究[J].无机化学学报,2006,22(2)：268～272.
[36]阳书文,于洁,吕国强等.可循环利用的Li4SiO4吸收CO2的实验研究[J].中国稀土学报,2008,26：657～660.
[37]尹霞,黄孝华,郭泰民等.以硅微粉为原料合成吸收CO2材料硅酸锂的研究[J].中国陶瓷,47(12)：70～72.
[38]王珂,郭欣,赵鹏飞等.飞灰-硅酸锂吸收剂捕获CO2的实验研究[J].工程热物理学报,2011,32(7)：1257～1259.
[39]Olivares-Marin M, Drage T C, Maroto-Valer M M. Novel lithium-based sorbents from fly ashes for CO2 capture at high temperatures[J]. Int J Greenh Gas Con,2010,4 (4):623～ 629.
[40]陕绍云,张中勇,贾庆明等.不同硅源对硅酸锂高温吸收CO2的影响[J].化工新型材料,2011,39(10)：73～75.
[41]Shan S Y, Jia Q M, Jiang L H et al. Effect of different silicon sources on CO2 absorption properties of Li4SiO4 at high temperature[J]. Adv Mater Res,2011,213:515～518.
[42]李芹超.硅酸锂的合成及其高温吸收CO2的性能研究[D].昆明：昆明理工大学,2012.
[43]Wang K, Guo X, Zhao P F et al. High temperature capture of CO2 on lithium-based sorbents from rice husk ash[J]. J Hazard Mater,2011,189 (1-2):301～307.
[44]Bretado M E, Velderrain V G, Gutierrez D L, Collins-Martinez V, Ortiz A L. A new synthesis route to Li4SiO4 as CO2 catalytic/sorbent[J]. Catal Today,2005,107～108:863～867.
[45]翁端,万杰,冉锐.高温CO2吸附材料硅酸锂的合成及吸附过程研究[J].科技导报,2011,29(22)：25～30.
[46]Wu X W, Wen Z Y, Xu X G et al. Synthesis and characterization of Li4Si04 nano-powders by a water-based sol-gel process[J]. J Nucl Mater,2009,392 (3):471～475.
[47]Wu X W, Wen Z Y, Xu X G et al. Fabrication of Li4SiO4 pebbles by a sol-gel technique[J]. Fusion Eng Des,2010,85 (2):222～226.
[48]丁铸,邢锋,康健.高温吸碳材料的合成[J].中国粉末技术,2009,15(5)：65-67.
[49]任德刚.硅酸锂吸附CO2的特性研究[J].电力建设,2010,31(8)：63～66.
[50]Kato M, Nakagawa K, Essaki K et al. Novel CO2 absorption using lithium-containing oxide[J]. Int J Appl Ceram Tec,2005,2 (6):467～475.
[51]Essaki K, Kato M, Nakagawa K. CO2 removal at high temperature using packed bed of lithium silicate pellets[J]. J Ceram Soc Jpn,2006,114 (9):739～742.
[52]Essaki K, Kato M, Uemoto H. Influence of temperature and CO2 concentration on the CO2 absorption properties of lithium silicate pellets[J]. J Mater Sci Lett,2005,40(18):5017～ 5019.
[53]董红英,任艳萍,张建勇等.硅酸锂粉末吸收二氧化碳的性能分析[J].粉末冶金技术,2011,29(6)：413-418.
[54]Pacciani R, Torres J, Solsona P et al. Influence of the concentration of CO2 and SO2 on the absorption of CO2 by a lithium orthosilicate-based absorbent[J]. Environ Sci Technol,2011, 45 (16):7083～088.
[55]王银杰,其鲁,江卫军.K的掺杂对硅酸锂吸收CO2性能的影响[J].北京理工大学学报,2006,26(5)：458～460+470.
[56]王银杰,其鲁,代化克.Na掺杂对硅酸锂吸收CO2性能的影响[J].物理化学学报,2006,22(7)：860～863.
[57]Mejia-Trejo V L, Fregoso-Israel E, Pfeiffer H. Textural, structural, and CO2 chemisorption effects produced on the lithium orthosilicate by its doping with sodium (Li4-xNaxSiO4)[J]. Chem Mater,2008,20 (22):7171～7176.
[58]Gauer C, Heschel W. Doped lithium orthosilicate for absorption of carbon dioxide[J]. J Mater Sci,2006,41 (8):2405～2409.
[59]汪文哲,熊贵,张军营等.高温下Ti掺杂对Li4SiO4吸收CO2的性能的影响[J].动力工程学报,2010,30(8)：623～627.
[60]阳书文,于洁,马文会等.K和Ca的掺杂对硅酸锂高温吸收CO2性能的影响[J].中山大学学报(自然科学版),2009,48(增刊2)：143-146.
[61]Seggiani M, Puccini M, Vitolo S. High temperature and low concentration CO2 sorption on Li4SiO4 based sorbents:Study of the used silica and doping method effects [J]. Int J Greenh Gas Con,2011,5 (4):741-748.
[62]Venegas M J, Fregoso-Israel E, Escamilla R et al. Kinetic and reaction mechanism of CO2 sorption on Li4SiO4:Study of the particle size effect[J]. Ind Eng Chem Res,2007,46 (8): 2407-2412.
[63]Okumura T, Matsukura Y, Gotou K et al. Particle size dependence of CO2 absorption rate powdered Li4SiO4 with different particle size[J]. J Ceram Soc Jpn,2008,116(12):1283 ～ 1288.
[64]吕国强,王华,马文会等.Li4SiO4吸收CO2的实验研究[J].工业加热,2007,36(5)：4-7.
[65]Rodriguez-Mosqueda R, Pfeiffer H. Thermokinetic analysis of the CO2 chemisorption on Li4SiO4 by using different gas flow rates and particle sizes[J]. J Phys Chem A,2010,114 (13):4535～4541.
[66]狄跃忠,冯乃祥,董维维等.真空热还原制取金属锂过程中Li2CO3热分解的研究[J].有色金属(冶炼部分),2009,(6)：28～30.
[67]Tang T, Zhang Z, Meng J B et al. Synthesis and characterization of lithium silicate powders[J]. Fusion Eng Des,2009,84 (12):2124～2130.
[68]唐涛.锂基陶瓷基态与缺陷性质的第一原理计算及硅酸锂中氘行为的实验研究[D].绵阳：中国工程物理研究院,2010.
[69]Cruz D, Bulbulian S, Lima E et al. Kinetic analysis of the thermal stability of lithium silicates (Li4SiO4 and Li2SiO3)[J].J Solid State Chem,2006,179 (3):909～916.
[70]吉红新.y-LiAlO2基发光材料的合成及发光性能研究[J].绵阳：西南科技大学,2008.