醇添加对钴基催化剂费托合成反应的影响

Effect of Alcohol Addition on Fischer-Tropsch Synthesis over Cobalt-Based Catalysts

在固定床微反应器上利用全产物在线分析方法,研究了钴基催化剂上伯醇CnH2n+1OH(n=2,3,5,6)在惰性气氛(Ar)和氢气气氛下的反应行为以及添加CnH2n+1OH对费托(FT)合成反应的影响,并结合原位漫反射傅里叶变换红外光谱(DRIFTS)表征.结果表明:碳数为n的醇在Ar气氛和H2气氛下反应主要有脱羰和脱水两条反应路径,分别生成碳数为n-1的烃和相同碳数的烃.低碳数醇(乙醇和正丙醇)的添加对费托合成产物分布无明显影响;而较高碳数的醇(正戊醇和正己醇)的加入使碳数为n-1以上烃的选择性显著增加,这是由于CnH2n+1OH加入后生成碳数为n-1和n的中间体可进一步发生链引发反应,生成更多的长链烃.

CnH2n＋1OH （n=2, 3, 5, 6） primary alcohol activation, hydrogenation and its additional effects on the performance of the Fischer-Tropsch （FT） synthesis over a cobalt catalyst were investigated in a fixed bed micro-reactor. All products were analyzed using an on-line gas chromatography. The diffuse reflectance infrared Fourier transform spectroscopy （DRIFTS） was used to investigate intermediates on the catalyst surface. In the presence of argon or hydrogen, CoH2n＋1OH underwent two main reactions： direct de-carbonylation to produce （CH2）n-1 hydrocarbons, and dehydration to produce （CH2）n hydrocarbons. The addition of lower carbon number alcohol （ethanol or 1-propanol） into the FT synthesis reaction had no significant effect on the hydrocarbon product distribution. While co-feeding higher carbon number alcohol （1-pentanol or 1-hexanol） into the FT synthesis reaction, the selectivity to hydrocarbons with carbon numbers greater than or equal to n-1 increased markedly because of the additive＇s chain initiation on the catalyst surface.