CAJ | 학술논문

CuO-CeO_2系列催化剂是高效的CO选择性氧化反应的催化剂,通过原佗漫反射红外光谱对掺杂碱金属和碱土金属氧化物的CuO-CeO_2催化剂表面的吸附物种进行了研究.结果表明CuO-CeO_2系列催化剂上,2 106 cm~(-1)处出现CO的红外吸附峰.在反应气氛中,此峰的强度随着温度先升高后降低,说明Cu+是CO主要的活性吸附中心.低温下催化剂表面吸附的CO主要以可逆形式脱附出来,而高温下CO则以不可逆的形式脱附出来.催化剂表面在3 660 cm~(-1)处出现尖锐的红外峰,归属于CeO_2经还原产生的Ce-(OH)_2偕式基团.在1 568,2 838和2 948 cm~(-1)附近处出现甲酸根的红外谱峰,以及1 257和1 633 cm~(-1)处出现碳酸根物种的红外峰.甲酸根物种是气相的CO与表面的羟基反应生成的产物,该物种的C-H键断裂生成碳酸根物种,这两物种均会降低催化剂的高温活性.Cu_1Li_1Ce_9O_δ催化剂出现较强的CO_2和甲酸根的红外峰,温度高于180℃时,该催化剂上还能看到微弱的CO红外峰,说明锂离子的给电子性质有利于提高Cu_1Li_1Ce_9O_δ催化剂上CO的不可逆脱附,抑制氢的活化吸附,同时促进了甲酸根物种的生成.低温下Cu_1Mg_1Ce_9O_δ和Cu_1Ba_1Ce_9O_δ催化剂上CO的吸附量较多,但主要以可逆脱附形式脱附出来,对CO选择性氧化没有贡献.
CuO-CeO_2계렬최화제시고효적CO선택성양화반응적최화제,통과원타만반사홍외광보대참잡감금속화감토금속양화물적CuO-CeO_2최화제표면적흡부물충진행료연구.결과표명CuO-CeO_2계렬최화제상,2 106 cm~(-1)처출현CO적홍외흡부봉.재반응기분중,차봉적강도수착온도선승고후강저,설명Cu+시CO주요적활성흡부중심.저온하최화제표면흡부적CO주요이가역형식탈부출래,이고온하CO칙이불가역적형식탈부출래.최화제표면재3 660 cm~(-1)처출현첨예적홍외봉,귀속우CeO_2경환원산생적Ce-(OH)_2해식기단.재1 568,2 838화2 948 cm~(-1)부근처출현갑산근적홍외보봉,이급1 257화1 633 cm~(-1)처출현탄산근물충적홍외봉.갑산근물충시기상적CO여표면적간기반응생성적산물,해물충적C-H건단렬생성탄산근물충,저량물충균회강저최화제적고온활성.Cu_1Li_1Ce_9O_δ최화제출현교강적CO_2화갑산근적홍외봉,온도고우180℃시,해최화제상환능간도미약적CO홍외봉,설명리리자적급전자성질유리우제고Cu_1Li_1Ce_9O_δ최화제상CO적불가역탈부,억제경적활화흡부,동시촉진료갑산근물충적생성.저온하Cu_1Mg_1Ce_9O_δ화Cu_1Ba_1Ce_9O_δ최화제상CO적흡부량교다,단주요이가역탈부형식탈부출래,대CO선택성양화몰유공헌.
CuO-CeO_2 series catalysts are the effective catalysts for the selective CO oxidation in hydrogen-rich gas.The adsorption species on the CuO-CeO_2 catalysts doped with alkali and alkaline earth metal oxides were investigated with in situ diffuse reflectance FTIR spectroscopy (irrsitu DRIFTS) technique.The results showed that a bane at 2 106 cm~(-1),due to the carbonyl species,appeared on the CuO-CeO_2 catalysts.In the reaction atmosphere,the intensity of this band increased first and then decreased with increasing the temperatures.It was noted that the main active adsorption sites of the CuO-CeOz catalysts were Cu~+ species.At lower temperatures,the carbonyl species were desorbed from the surface of CuO-CeO_2 catalysts in the reversible form,while they were desorbed mainly in the irreversible form at the higher temperatures.A sharp peak at 3 660 cm~(-1),attributed to the geminal Ce(OH)2 group,was also apparent on the surface of reduced CuO-CeO_2 catalyst.The peaks at 1 568,2 838 and 2 948 cm~(-1) were attributed to formate species and the peaks centered at 1 257 and 1 633 cm~(-1) were assigned to carbonate species.CO could react with the active hydroxyl species and generate formate species.At higher temperatures,the C-H bond of formate species could break and form carbonate species.These two species would decrease the performance of CuO-CeO_2 catalysts at higher temperatures.The stronger IR peaks attributed to CO_2 and formate species were observed,moreover there was still a weak IR peak assigned to carbonyl species for Cu_1Li_1Ce_9O_δ catalyst when the temperature was above 180 ℃.It was shown that as the electron donor,the doping of Li2O on CuO-CeO_2 catalyst could contribute to the irreversible desorption of CO at lower temperatures and inhibit the adsorption of H2 on the catalytic surface,and benefit the formation of formate species as well.Although the amounts of CO adsorption on Cu_1Mg_1Ce_9O_δ and Cu_1Ba_1Ce_9O_δ catalysts were much more than other catalysts at lower temperatures,they were mainly desorbed in the reversible form,which had no contribution to the selective CO oxidation.