Highly selective and stable CsPW/Nb2O5 catalysts for dehydration of glycerol to acrolein
Highly selective and stable CsPW/Nb2O5 catalysts for dehydration of glycerol to acrolein
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DOI：
10.1016/s1872-2067(12)60666-4
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发表时间：
2013-09
影响因子：
16.5
通讯作者：
刘蓉;王铁峰;刘畅;金涌
中科院分区：
文献类型：
--
作者：
刘蓉;王铁峰;刘畅;金涌
研究了以Nb 2 O 5为载体的Cs+取代Keggin型磷钨酸盐Cs2.5H0.5PW12O40（CsPW）催化甘油在300 °C气相脱水制丙烯醛的反应。采用N2吸附-脱附、X射线衍射、傅里叶变换红外光谱、拉曼光谱和NH3程序升温脱附等方法对催化剂进行了表征。结果表明，刘易斯酸中心是副产物形成的主要原因，中等强度的布朗斯特酸中心是甘油脱水生成丙烯醛的活性中心。焙烧温度和负载量对负载型磷钨酸铯的酸性有影响。当负载量≤ 20wt%时，CsPW在Nb 2 O 5上分散良好，体相CsPW的强酸中心被转化为选择性的中酸中心。在500 °C下焙烧的负载量为20%的CsPW催化剂，甘油转化率为96%，丙烯醛选择性为80%，10 h内无明显失活。活性降低20%的催化剂通过在500 °C下用空气简单焦炭燃烧来再生。
Acrolein production by gas-phase dehydration of glycerol at 300 °C, catalyzed by a Cs+-substituted Keggin-type phosphotungstate, Cs2.5H0.5PW12O40(CsPW), supported on Nb2O5was investigated. The catalysts were characterized using N2adsorption-desorption, X-ray diffraction, Fourier-transform infrared and Raman spectroscopies, and NH3temperature-programmed desorption. It was demonstrated that Lewis acid sites were responsible for byproduct formation, and that Brönsted acid sites of medium strength were the active sites for acrolein production by glycerol dehydration. The acidity of the supported CsPW was affected by the calcination temperature and CsPW loading. The CsPW was well dispersed on Nb2O5at loadings ≤ 20 wt%, and the strong acid sites of bulk CsPW were converted to selective medium acid sites. The CsPW catalyst with 20% of CsPW loading calcined at 500 °C gave 96% of glycerol conversion and 80% of acrolein selectivity, and there was no significant deactivation in 10 h. The catalyst with a 20% decrease in activity was regenerated by simple coke burning with air at 500 °C.