| With the development of industry and the improvement of living standards, market demand for higher alcohols is becoming biger and biger. However, traditional production technologes of higher alcohols are as usual as complicated, energy consumption big, polluted heavily and catalyst costs high, but the new method for producing higher alcohols, which is one step process with syngas under new catalyst, is technology simple, catalyst costs low, of energy saving and environmental protection, and hence is promising for industrialization. But the performance of Co/AC catalyst is still under scientific reasearch in lab, which could be further improved for the CO conversion and the higher alcohols selectivity in order to optimize the Co/AC catalyst for industrialization.This paper mainly investigated the influences of alkaline earth metal promoters, Al, Cu, Ru, Pd promoters and different support pre-treatment methods on the performance of catalyst. The AC support and catalysts were characterized by X-ray diffraction (XRD), H2 Temperature programmed reduction (H2-TPR), CO chemisorption, scanning electron microscope (SEM), He temperature promgrammed desorption (He-TPD) and so on. The results are as follows:1. The effects of Mg, Ca, Sr, Ba promoters on the performance of Co/AC catalyst were investigated. The results indicated that dopping a small amount of alkaline earth metal promoter could enhance Co dispersion, CO conversion; dopping a little Mg promoter would promote the Co2C generation so as to increase the yield of higher alcohols; especially that, adding a little Ca promoter could obviously encourage the formation of CO2C. To sum up, Ca is the most effective promoter among Mg, Ca, Sr, Ba for producing higher alcohols, promoting CO conversion from 39.8% to 50.6%, higher alcohols proportion in alcohol from 42.6% to 57.2%, higher alcohol yield from 3.70% to 5.41%. Combining XRD characterization and literatuers reports, it was found that whether the alkaline element could promote the Co2C formation might be related to ionic radius and dosage of the dopping element.2. The effects of Al, Cu, Ru, Pd promoters on the performance of CoZrLa/AC catalyst were investigated, the related discussion and analysis about the influence of the above promoters was mainly focused on A1 and Pd. The results revealed that adding Al or Cu or Ru suppressed the production of higher alcohols, while Pd promoted; and Al remarkablely restrained the formation of Co2C so as to make higher alcohols output diminished, although Pd had the same effect as Al on Co2C formation, enhanced higher alcohols selectivity owing to providing another active site. Besides, there was a kind of competitive advantage effect between Zr, La and the third promoter when dopping on CoZrLa/AC catalyst, that is, Zr could notablely weaken the dopping effect of Al or pd, denting the interaction effect of Al or Pd with Co.3. The effects of support pre-treatment with HNO3, HNO3-H2O2, and support thermal treatment on the performance of CoZrLa/AC catalyst were investigated. The results indicated that support pre-treatment with HNO3-H2O2 made the CO conversion and higher alcohols selectivity higher than pre-treatment with HNO3, and support thermal treatment could tailor the surface oxygenic functional groups so as to remarkably affact the catalytic performance.It was demonstrated that, support pre-treatment with HNO3-H2O2 increased the total amount of the surface oxygenic functional groups, particularly the carboxyl group, with the physical propertity no changing, which controled the quantities of Co2C, adjusted the ration of Co/Co2C, increased the CO conversion and higher alcohols selectivity; and support thermal treatment in 450℃,600 ℃,800 ℃ could made the carboxyl group, lactone group, phenolic hydroxyl group wiped out one after the other. Combining catalyst performance and related characterization, it was also found that carboxyl group and phenolic hydroxyl group were good for higher alcohols production while the lactone group was bad. |
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