CAJ | 학술논문

通过共沉淀法和沉积-沉淀法制备出了具有良好热稳定性的Al_2O_3改性Fe_2O_3基金催化剂,并通过透射电镜(TEM)、X射线衍射(XRD)、N_2吸附-脱附及热重和差示扫描最热(TG-DSC)分析等表征手段对催化剂的结构与表面形貌进行了研究分析.TEM测试结果表明:500℃焙烧后,未掺杂Al_2O_3的催化剂中金颗粒粒径分布较宽,平均粒径约为7.0 nm,载体颗粒尺寸在50-100 nm范围内;而掺杂Al_2O_3的催化剂中金颗粒粒径分布变窄,平均粒径约为5.0 nm,且载休颗粒大小也明显小于未掺杂Al_2O_3的催化剂,保持在30-50 nm的范围内.N_2吸附-脱附测试结果表明,Al_2O_3的掺杂有利于保持催化剂的介孔结构和比表面积,从而提高了载体的热稳定性.XRD和TG-DSC测试结果表明,Al_2O_3的掺杂可以有效地抑制Fe_2O_3的结晶,进而抑制了高温焙烧过程中金颗粒的长大.选用CO低温氧化反应对催化剂的活性进行了评价,即使在500℃高温下焙烧12 h,掺杂了 Al_2O_3的催化剂仍然可在26.7℃将CO完全转化,而未掺杂Al_2O_3的催化剂CO最低完全转化温度(T_(100))高达61.6℃.Al_2O_3的掺杂显著提高了催化剂的热稳定性能.
통과공침정법화침적-침정법제비출료구유량호열은정성적Al_2O_3개성Fe_2O_3기금최화제,병통과투사전경(TEM)、X사선연사(XRD)、N_2흡부-탈부급열중화차시소묘최열(TG-DSC)분석등표정수단대최화제적결구여표면형모진행료연구분석.TEM측시결과표명:500℃배소후,미참잡Al_2O_3적최화제중금과립립경분포교관,평균립경약위7.0 nm,재체과립척촌재50-100 nm범위내;이참잡Al_2O_3적최화제중금과립립경분포변착,평균립경약위5.0 nm,차재휴과립대소야명현소우미참잡Al_2O_3적최화제,보지재30-50 nm적범위내.N_2흡부-탈부측시결과표명,Al_2O_3적참잡유리우보지최화제적개공결구화비표면적,종이제고료재체적열은정성.XRD화TG-DSC측시결과표명,Al_2O_3적참잡가이유효지억제Fe_2O_3적결정,진이억제료고온배소과정중금과립적장대.선용CO저온양화반응대최화제적활성진행료평개,즉사재500℃고온하배소12 h,참잡료 Al_2O_3적최화제잉연가재26.7℃장CO완전전화,이미참잡Al_2O_3적최화제CO최저완전전화온도(T_(100))고체61.6℃.Al_2O_3적참잡현저제고료최화제적열은정성능.
Al_2O_3-modified Fe_2O_3 based gold catalysts with good thermal stability were prepared by co-precipitation and deposition-precipitation method. Characterization techniques, such as transmission electron microscope (TEM), X-ray diffraction (XRD), N_2 adsorption-desorption, and thermogravimetry-differential scanning calorimetry (TG-DSC), were used to investigate the structures, and surface morphologies of the catalysts. TEM results showed that after calcination at 500℃ the size distribution of the gold particles in the catalyst without Al_2O_3 doping was wide, the average diameter of the gold particles was about 7.0 nm and the size of the support particles ranged from 50 to 100 nm. However, the size distribution of the gold particles in the Al_2O_3-doped catalysts was narrow and the average diameter of the gold particles was around 5.0 nm. The Al_2O_3-doped Fe_2O_3 based Au particle size remained in a range of 30-50 nm, which is smaller than that of the Fe_2O_3 grains that were not doped with Al_2O_3. N_2 adsorption-desorption measurements showed that Al_2O_3 doping resulted in a stable mesoporous structure for the catalysts and remained a higher specific surface area, which promoted the thermal stability of the support. XRD and TG-DSC results indicated that Al_2O_3 doping retarded the crystallization of the support and consequently inhibited the growth of gold particles during high-temperature calcination. Low temperature CO oxidation was used as a probe reaction to evaluate the catalytic activity. Even when calcined at 500℃ for 12 h, the catalyst with Al_2O_3 doping achieved complete CO conversion at 26.7℃ while the lowest temperature of the complete CO conversion (T_(100)) of the catalyst without Al_2O_3 doping was as high as 61.6℃. Apparently, thermal stability is enhanced considerably by Al_2O_3 doping.