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摘要: 采用程序升温脱附（TPD）、Boehm滴定以及质量滴定（Mass titration）等方法分析了多壁碳纳米管(MWCNT)经过浓硝酸改性处理前后的表面酸性和酸性分布；同时运用XRD技术研究了碳纳米管负载Co-Mo催化剂的表面物种和活性组分的分散；并在高压微型反应器中，以二苯并噻吩（DBT）为模型化合物，对碳纳米管负载的Co-Mo催化剂体系进行了加氢脱硫（HDS）活性评价，以期揭示碳纳米管的表面修饰对其负载Co-Mo催化剂HDS性能的影响。研究结果表明：MWCNT表面呈一定的碱性，通过浓硝酸化学修饰以后，反而呈现较强的酸性，并且随着酸处理时间的延长，表面的酸性进一步增加。如，M-MWCNT-6（酸化6h）表面总酸量为1.29×10-3mol/g，M-MWCNT-24（酸化24h）表面总酸量为2.46×10-3mol/g。酸改性提高了Co-Mo催化剂在MWCNT表面的分散程度，以致Co-Mo/MWCNT催化剂的HDS活性和选择性明显高于Co-Mo/γ-Al2O3催化体系。然而，Co-Mo/M-MWCNT-6的HDS活性以及选择性与Co-Mo/MWCNT相差不多，略有降低，但是仍比Co-Mo/γ-Al2O3催化体系的HDS活性高。Co-Mo/M-MWCNT-24催化剂的HDS活性降低很多，并且催化性能发生了很大改变，产物中出现了大量的副产物-1,2-二苯基乙烷。表明，深度酸化改性反而不利于提高碳纳米管负载Co-Mo催化体系的HDS活性。
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关键词:
- 碳纳米管,表面改性,加氢脱硫
Abstract: Multi-walled carbon nanotubes (MWCNT) were modified by concentrated nitric acid and the effect on surface acidity, dispersion of Co-Mo catalysts on them, and hydrodesulfurization (HDS) activity were respectively characterized by temperature-programmed desorption (TPD) and Boehm and mass titration, XRD and a flow micro-high pressure reactor using dibenzothiophene (DBT) as the sulfur-containing model compound. It is found that MWCNT is slightly basic and that modified MWCNT shows strong acidity with total amount of acid for 6 and 24h modified samples, M-MWCNT-6 and M-MWCNT-24 being 1.29×10-3 and 2.46×10-3 mol/g respectively. The dispersion of Co-Mo catalyst on MWCNT is significantly improved after the modification. The activity and selectivity for HDS are apparently higher for Co-Mo/MWCNT than for Co-Mo/Al2O3. For the modified samples, however, a slight and a significant decrease of activity and selectivity for HDS is observed for both Co-Mo/M-MWCNT-6 and Co-Mo/M-MWCNT-24 with a large proportion of byproduct found for the latter, indicating that significant modification is unfavorable for HDS. -
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