CeO_2掺杂对CaO基吸收剂CO_2捕获性能的影响

以P123作为软模板剂,通过均相沉淀法制备了CeO_2掺杂的CaO基吸收剂,研究了CeO_2掺杂对CO_2捕获的影响。结果表明,CeO_2掺杂可促进表面氧物种的生成,从而促进CaO与CO_2的碳酸化反应。CaO-CeO_2的相互作用一方面促进了从Ca到表面氧物种的电子转移;另一方面,由于部分Ca离子对晶格中Ce离子的取代,晶格的电中性被打破,有利于CeO_2中晶格氧的逸出,以及氧空位和O^(2-)的生成。本实验制备的纯CaO吸收剂的碳酸化反应活化能为28.1 kJ/mol,而掺杂CeO_2后活化能显著降低,且当Ce/Ca(物质的量比)为0.25时达到最低值10.2 kJ/mol。另外,CeO_2的掺杂有利于CaO的分散,进而减缓CaO烧结。CeO_2掺杂的吸收剂在碳酸化/煅烧循环中表现出良好的CO_2捕获性能和循环稳定性。

Ni/Al2O3催化剂作用下乙酸水蒸气催化重整制氢研究

采用浸渍法制备Ni/Al2O3催化剂,并利用BET、XRD、GC-MS、TG等对反应前后催化剂及液态产物进行了表征。采用固定床反应器考察了Ni/Al2O3催化剂作用下乙酸水蒸气重整制氢的反应性能,研究了反应温度、水碳比、CaO吸收剂等因素对气体组分体积分数变化以及氢气收率的影响。结果表明,在重整反应温度为600℃、水碳比为5的条件下,氢气体积分数可达92.9%,其收率为97.9%;添加CaO吸收剂后,氢气体积分数增加了6.1%,但其收率下降15%。反应后催化剂的XRD和TG表征结果表明,CaO吸收剂的加入抑制了催化剂表面消碳反应的进行,进而造成Ni/Al2O3催化剂作用下氢气收率的下降。

Modification of CaO-based sorbents prepared from calcium acetate for CO_2 capture at high temperature

CaO-based sorbent is considered to be a promising candidate for capturing CO_2 at high temperature. However,the adsorption capacity of CaO decreases sharply with the increase of the carbonation/calcination cycles. In this study, CaO was derived from calcium acetate(CaAc_2), which was doped with different elements(Mg, Al,Ce, Zr and La) to improve the cyclic stability. The carbonation conversion and cyclic stability of sorbents were tested by thermogravimetric analyzer(TGA). The sorbents were characterized by N_2 isothermal adsorption measurements, scanning electron microscopy(SEM) and X-ray diffraction(XRD). The results showed that the cyclic stabilities of all modified sorbents were improved by doping elements, while the carbonation conversions of sorbents in the 1st cycle were not increased by doping different elements. After 22 cycles, the cyclic stabilities of CaO–Al, CaO–Ce and CaO–La were above 96.2%. After 110 cycles, the cyclic stability of CaO–Al was still as high as 87.1%. Furthermore, the carbonation conversion was closely related to the critical time and specific surface area.

基于CaO引导的甲烷蒸汽重整化学链燃烧制氢系统

为在重整气中得到高纯H2和降低尾气CO2分离成本，建立了基于CaO引导的甲烷蒸汽重整化学链燃烧制氢系统，该系统在重整反应器中加入CaO吸收剂，用以吸收重整器内的CO2，提高重整气中H2浓度，形成的CaCO3固体在煅烧器中受热分解重新生成CaO。利用AspenPlus进行了过程模拟及热力学分析，并研究主要参数对系统性能的影响，得到优化的操作条件为：CaO循环量／CH4比为0．5，CH4（燃料）／CH4比为0．35，NiO循环量／CH4比为1．4。CaO循环量／CH4比从0变化到O．5时，重整气中H2浓度从O．60增长到0．99；CH4（燃料）／CH4比在0．25～０．45区间变化时，重整气中Ｈ２浓度从0．86提高到0．99，产气量增加；NiO循环量，CH4比在1～1．6区间变化时，重整气中H2浓度从0．88增长到0．99，系统有效能效率变化较小。