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化石燃料的燃烧已造成更多的CO2排入大气[1]。1800—2020年,大气中CO2的体积分数由280 cm3·m−3升至410 cm3·m−3,造成全球表面气温上升约1.2 ℃[2-3]。为应对全球气候变暖,各国纷纷出台了CO2减排政策,中国亦明确了“碳中和”目标[4]。CO2捕集技术能从工业排放点源处减少CO2排放,还可吸收大气中已有的CO2,因而对水泥和钢铁等重工业的深度脱碳、低碳氢能的规模化生产、低碳电力供给、实现“碳中和”等具有重要意义[5-7]。
CO2捕集技术包括化学吸收、固体吸附和膜分离等[8-10]。综合考虑对设备腐蚀性、能耗、分离效率和适用范围等问题,固体吸附法(包括钙基吸附剂、多孔物理吸附剂和固态胺吸附剂)被认为是很有前途的CO2分离技术[11-12]。其中,固态胺吸附剂具有以下优势:CO2选择性高、吸附能力强、吸附速率快和能耗低;适用范围广,可用于低浓度CO2捕集;且操作温度低,通常运行温度为50~180 ℃,可广泛应用于工业烟气CO2捕集[9]。固态胺吸附剂通常是将有机胺如聚乙烯亚胺(Polyethyleneimine,PEI)、四乙烯五胺(Tetraethylenepentamine,TEPA)、五乙烯六胺(Pentaethylenehexamine,PEHA)等浸渍或嫁接到多孔载体上制备而成[13]。多孔载体的结构和性质很大程度上决定了固态胺吸附剂的CO2吸附性能。包括多孔沸石、介孔二氧化硅、有机框架材料、多孔活性炭、多孔树脂等在内的多种载体材料陆续被研究人员开发出。宋春山等[14]采用模板剂法合成出具有倒锥形孔道的介孔二氧化硅并负载PEI制备固态胺吸附剂,其CO2吸附能力达到214 mg·g−1。IRANI等[15]采用TEPA浸渍碳纳米管,制备得到的固态胺吸附剂具有220 mg·g−1以上的CO2吸附能力。然而,过于复杂的制备过程及多种昂贵试剂的使用导致吸附剂的成本居高不下。另外,李凯敏等[11]发现,在使用CO2作为解吸气升温解吸固态胺吸附剂过程中,该吸附剂往往会在几个循环后因生成尿素链而快速失活。而只有使用CO2作为解吸气方能获得高纯CO2用于后续利用或封存[16]。因此,亟需开发在CO2解吸气氛下,廉价且具备高稳定性的固态胺吸附剂。
多孔Al2O3具有较高的比表面,且热稳定性好,在催化剂、催化剂载体、吸附剂载体等领域应用广泛。Al2O3载体作为两性物质含有较多的路易斯酸性位点,使得制备得到的材料往往具有较特殊的性能[17]。然而,多孔Al2O3的孔体积往往小于介孔二氧化硅、活性炭等载体,使得难以负载高含量的活性胺,进而导致铝基固态胺吸附剂的CO2吸附性能不尽如人意[18]。
本研究以铝酸钠和硫酸铝2种从铝土矿中提取的工业副产物为原料,采用共沸蒸馏的方式进行扩孔合成大孔体积Al2O3,并以此负载PEI制备铝基固态胺吸附剂,进一步优化多孔Al2O3的孔隙结构。然后,重点研究铝基固态胺吸附剂的吸附性能和循环稳定性,并结合分析表征,揭示铝基固态胺吸附剂的循环稳定性机制,以期为进一步开发低成本、高稳定性固态胺吸附剂提供参考。
高性能铝基固态胺吸附剂的制备及其对CO2的吸附
Preparation and CO2 adsorption of high-performance aluminum-based solid amine adsorbent
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摘要: 以铝酸钠和硫酸铝为原料,通过共沸蒸馏合成大孔体积Al2O3,并以此作为载体浸渍聚乙烯亚胺(PEI)制备铝基固态胺吸附剂,再系统研究了其对CO2的吸附性能及循环稳定性。通过老化、共沸蒸馏等工艺,在最佳工艺参数下制得孔体积为2.75 cm3·g−1的多孔Al2O3载体,进而制备得到优等级吸附剂(60%PEI@Al2O3-4 h),其对CO2的饱和吸附能力可达到194 mg·g−1。该吸附剂在惰性解吸气氛和CO2解吸气氛下均具有稳定的循环性能,10次循环后其对CO2的吸附量依然为186 mg·g−1和148 mg·g−1,分别衰减不到1%和15.2%。本研究结果可为开发低成本、高稳定性固态胺吸附剂提供参考。Abstract: The porous Al2O3 with large-pore volume was synthesized by azeotropic distillation with sodium aluminate and aluminum sulfate as raw materials, which was used as a support to impregnate polyethyleneimine (PEI) for preparing aluminum-based solid amine adsorbent. The CO2 adsorption performance and cyclic stability of the adsorbent were systematically investigated subsequently. The porous Al2O3 supports with apore volume of 2.75 cm3·g−1 were prepared by aging and azeotropic distillation processes under the optimal technological parameters, and then the superior grade adsorbent (60%PEI@Al2O3-4 h) with a saturation CO2 adsorption capacity of 194 mg·g−1 was prepared. In addition, the adsorbent had stable cyclic performance in inert desorption atmosphere and CO2 desorption atmosphere. After 10 cycles, the CO2 adsorption capacity of 60%PEI@Al2O3-4 h still retained 186 mg·g−1 and 148 mg·g−1, with attenuation of less than 1% and 15.2%, respectively. This study can provide reference for developing low-cost and high-stability solid amine adsorbents.
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表 1 不同合成条件制备得到的多孔Al2O3孔结构参数
Table 1. Pore structure parameters of the porous Al2O3 under different synthesis conditions
样品 SBET/(cm2·g−1) V/( cm3·g−1) D/nm 未共沸-未老化 77.1 0.36 17.6 共沸-未老化 433.1 2.49 20.2 共沸-老化2 h 449.4 2.59 21.3 共沸-老化4 h 495.7 2.75 20.3 共沸-老化6 h 474.2 2.51 19.0 注:SBET表示比表面积;V表示孔体积;D表示BJH吸附平均
孔径。 -
[1] 李函珂, 党成雄, 杨光星, 等. 面向二氧化碳捕集的过程强化技术进展[J]. 化工进展, 2020, 39(12): 4919-4939. [2] JAHANDAR LASHAKI M, KHIAVI S, SAYAYI A. Stability of amine-functionalized CO2 adsorbents: a multifaceted puzzle[J]. Chemical Society Reviews, 2019, 48(12): 3320-3405. doi: 10.1039/C8CS00877A [3] 王君雅, 羊莹, 宁平. 碱金属硝酸盐对促进LDH基材料吸附CO2 性能的影响[J]. 环境工程学报, 2018, 12(12): 3379-3388. doi: 10.12030/j.cjee.201808095 [4] 张亚朋, 崔龙鹏, 刘艳芳, 等. 3种典型工业固废的CO2矿化封存性能[J]. 环境工程学报, 2021, 15(7): 2344-2355. doi: 10.12030/j.cjee.202101003 [5] TIAN S C, YAN F, ZHANG Z T, et al. Calcium-looping reforming of methane realizes in situ CO2 utilization with improved energy efficiency[J]. Science advances, 2019, 5: eaav5077. doi: 10.1126/sciadv.aav5077 [6] 米剑锋, 马晓芳. 中国CCUS 技术发展趋势分析[J]. 中国电机工程学报, 2019, 39(9): 2537-2543. [7] FANG M X, YI N T, DI W T, et al. Emission and control of flue gas pollutants in CO2 chemical absorption system - a review[J]. International Journal of Greenhouse Gas Control, 2020, 93: 102904. doi: 10.1016/j.ijggc.2019.102904 [8] 陈旭, 杜涛, 李刚, 等. 吸附工艺在碳捕集中的应用现状[J]. 中国电机工程学报, 2019, 39(S1): 155-163. [9] 秦红艳, 张晓云, 张鹏志, 等. 氨基改性CO2固体吸附材料的研究进展[J]. 材料导报, 2013, 27(19): 39-42. [10] YANG Z Q, HE C Q, SUI H, et al. Recent advances of CO2-responsive materials in separations[J]. Journal of CO2 Utilization, 2019, 30: 79-99. doi: 10.1016/j.jcou.2019.01.004 [11] LI K M, JIANG J G, TIAN S C, et al. Polyethyleneimine–nano silica composites: a low-cost and promising adsorbent for CO2 capture[J]. Journal of Materials Chemistry A, 2015, 3(5): 2166-2175. doi: 10.1039/C4TA04275A [12] 马双忱, 韩剑, 方文武, 等. 燃煤烟气中CO2脱除方法的分析与探讨[J]. 电力科技与环保, 2011, 27(2): 4-8. doi: 10.3969/j.issn.1674-8069.2011.02.002 [13] 仇雪霞, 刘新民. 以废塑料为基材的大孔型离子交换树脂的制备, 表征和吸附性能[J]. 环境工程学报, 2020, 14(1): 224-235. doi: 10.12030/j.cjee.201903198 [14] LOU F J, ZHANG A F, ZHANG G H, et al. Enhanced kinetics for CO2 sorption in amine-functionalized mesoporous silica nanosphere with inverted cone-shaped pore structure[J]. Applied Energy, 2020, 264: 114637. doi: 10.1016/j.apenergy.2020.114637 [15] IRANI M, JACOBSON A T, GASEM K A M, et al. Modified carbon nanotubes/tetraethylenepentamine for CO2 capture[J]. Fuel, 2017, 206: 10-18. doi: 10.1016/j.fuel.2017.05.087 [16] JEON S, JUNG H, KIM S H, et al. Double-layer structured CO2 adsorbent functionalized with modified polyethyleneimine for high physical and chemical stability[J]. ACS Applied Materials Interfaces, 2018, 10: 21213-21223. doi: 10.1021/acsami.8b01749 [17] 蔡卫权, 余小锋. 高比表面大中孔拟薄水铝石和γ-Al2O3的制备研究[J]. 化学进展, 2007, 19(9): 1323-1330. [18] BHOWMIK K, CHAKRAVARTY A, BYSAKH S, et al. γ-Alumina nanorod/reduced graphene oxide as support for poly(ethylenimine) to capture carbon dioxide from flue gas[J]. Energy Technology, 2016, 4(11): 1409-1419. doi: 10.1002/ente.201600186 [19] SHEN X H, YAN F, LI C Y, et al. Biogas upgrading via cyclic CO2 adsorption: Application of highly regenerable PEI@nano-Al2O3 adsorbents with anti-urea properties[J]. Environmental Science Technology, 2021, 55(8): 5236-5247. doi: 10.1021/acs.est.0c07973 [20] CAI W Q, LI H Q, ZHANG Y. Azeotropic distillation-assisted preparation of macro-mesostructured γ-Al2O3 nanofibres of crumpled sheet-like morphology[J]. Materials Chemistry and Physics, 2006, 96(1): 136-139. doi: 10.1016/j.matchemphys.2005.06.053 [21] SHEN X H, YAN F, LI C Y, et al. Amine-functionalized nano-Al2O3 adsorbent for CO2 separation from biogas: Efficient CO2 uptake and high anti-urea stability[J]. Journal of Cleaner Production, 2022, 332: 130078. doi: 10.1016/j.jclepro.2021.130078 [22] SIEGELMAN R L, MILNER P J, KIM E J, et al. Challenges and opportunities for adsorption-based CO2 capture from natural gas combined cycle emissions[J]. Energy & Environmental Science, 2019, 12(7): 2161-2173. [23] 赵蓓蓓, 王际童, 王梅, 等. 树脂基固态胺吸附剂室温下对低浓度CO2的吸附性能研究[J]. 环境科学学报, 2014, 34(11): 2892-2898. [24] WANG W J, MOTUZAS J, ZHAO X S, et al. 2D/3D assemblies of amine-functionalized graphene silica (templated) aerogel for enhanced CO2 sorption[J]. ACS Applied Materials Interfaces, 2019, 11(33): 30391-30400. doi: 10.1021/acsami.9b07192 [25] LI C Y, YAN F, SHEN X H, et al. Highly efficient and stable PEI@Al2O3 adsorbents derived from coal fly ash for biogas upgrading[J]. Chemical Engineering Journal, 2021, 409: 128117. doi: 10.1016/j.cej.2020.128117 [26] LI K M, JIANG J G, CHEN X J, et al. Research on urea linkages formation of amine functional adsorbents during CO2 capture process: Two key factors analysis, temperature and moisture[J]. Journal of Physical Chemistry C, 2016, 120(45): 25892-25902. doi: 10.1021/acs.jpcc.6b08788