Research Of Co-based Catalysts For Higher Alcohols Synthesis Through CO Hydrogenation

With the development of industry and the improvement of living standards,market demand for higher alcohols is becoming larger and larger.Taditional production technologes of higher alcohols are complicated,high energy consumption,high cost and pollution,However,one step process producing higher alcohols with syngas under new catalyst is technology simple,environmental friendly,with low energy consumption and pollution,comply with the country called for in the new period and the international community environmental protection spirit is promising for industrialization.This paper mainly investigated the influences of carbon supports?active carbon derived from coconut shell?SAC?,derived from coal?CAC?and HSAG?and different concentrations of nitric acid treatment carbon materials,alkali metal additives?Na,K,Cs?,rare earth metal additives?La,Ce?on the performance of 15Co/AC catalyst.The carbon materials and catalysts were characterized by X-ray diffraction?XRD?,H₂ Temperature programmed reduction?H₂-TPR?,CO chemisorption so on.The results are as follows:1.The effects of SAC,CAC and HSAG on the performance of Co/AC catalyst were investigated.The results indicated that SAC supported catalyst CO conversion was 25.4%,the selectivity of alcohol was 19.9%;CAC which treatment by H₂-HNO3 supported catalyst CO conversion from 8.2%increased to 31.4%.However,HSAG treatmented by nitric acid 15Co/HSAG-4.6 catalyst CO conversion was 87.3%,the selectivity of alcohol was 4.5%,the catalyst which HSAG treatment with different concentration of nitric acid there were no difference in performance.SAC,CAC and HSAG have different physical structure.SAC and CAC have plentiful microporous structure and tremendous surface area,The activity of catalyst center located in microporous pore;HSAG has plane structure with small surface area.HSAG surface area decreased significantly treatment by nitric acid treatment,while the CO conversion was no difference,which illustrated suppots surface area had no inflence of cobalt based catalyst activity.The surface of SAC and CAC have S element and in the process of reaction grain growth were the reason active carbon supported catalysts had low CO conversion.HSAG supported catalyst had strong electron transfer capability,which has high CO conversion.HSAG supported catalyst which treatment by different concentrations of nitric acid have similar performance,the support through surface defect with Co,surface defect no change.H₂-TPR and In-situ XRD showed that the SAC,HSAG supported catalyst exhibited the same reduction,reduction process include Co3O4?CoO and CoO?Co.XRD characterization and literature analysis found that activated carbon supported catalyst is much easier to form the active center of alcohol Co2C,while the catalyst supported on HASG is more difficult.2.The effects of Na?K?Cs alkaline metal on the performance of 15Co/HSAG-4.6 catalysts were investigated.The results indicated that adding alkali additives to 15Co/HSAG-4.6 catalysts CO conversion reduced,Cs?Na additives could significantly improve the selectivity of alcohol as well as the distribution of high carbon alcohols.Adding alkali additives in 15Co/HSAG-4.6 Co dispersion increased,grain size were reduced,while alkali additives inhibited the catalysts hydrogenation activity resulting in the catalyst Co conversion declineed.Catalyst surface which was caidity could lead to some by-products especially alcohol dehydration,while alkali metal could modification surface acidity inhibit by-products,chain growth,improve the selectivity of alcohols.The effects of Cs additive contents on the performance of 15Co/HSAG-4.6 catalysts were investigated.The results showed that with increase of Cs additives content CO conversion reduced,while ROH selectivity reached biggest when Cs content was 1%then declined.Adding Cs promoter to 15Co/HSAG-4.6 catalyst could improve Co dispersion,Co grain size was reduced,while reduction temperature improved perhaps Co-Cs interaction increased,resulting in catalyst Co hydrogenation activity declined.3.The effects of La,Ce rare earth metal additives on the performance of 15Co/HSAG-4.6 catalysts were investigated.The results showed that the La,Ce additives reduced catalyst CO conversion and selectivity of CO2,Ce additives could significantly improve the selectivity of alcohol and high carbon alcohols.Catalyst Co dispersion decreased result in Co conversion decreased.