| Bio-oil is a kind of liquid fuel manufactured through fast pyrolysis technology of biomass, it is multi-component mixture highly oxygenated with a great amount of macromolecules, which nearly includes all species of oxygenated organics, such as esters, ethers, acetaldehydes, ketones, phenols, organic acids, and alcohols. Its high corrosiveness and instability derived from substantial amounts of organic acid and reactive acetaldehydes lead bio-oil must to be upgraded to more stable for high quantity fuel oil. At present, a large number of studies focused on hydrogenation or esterification singly. Few researchers have integrated them into one step for bio-oil upgrading. In this paper, the major work is focused on the study of bifunctional catalysts preparation and the performance of catalytic hydrogenation-esterification reaction over bifunctional catalyst, in order to supply technical support and theoretical basis for upgrading research of bio-oil.Bifunctional catalysts Pd-Ni/HZSM-5and Pd-Co/HZSM-5were prepared using HZSM-5as support by the incipient-wetness impregnation method in this paper. Effect of Si/Al ratio and loading of active component, calcination and reduction temperature of catalyst, reaction condition (reaction temperature, H2/aldehyde ratio, catalyst amount) on catalytic performance were systematically studied. The esterification and hydrogenation performance of catalyst Pd-Ni/HZSM-5were also examined. The results showed that the optimal reaction conditions of Pd-Ni/HZSM-5catalyst are as follows:the loading of Ni is15%, calcination temperature is723K, reduction temperature is473K, reaction temperature is513K,H2/aldehyde ratio is5, Si/Al ratio of HZSM-5is25and catalyst amount is2.0g. In result, the conversion of acetic acid is62.3%, the selectivity to ethyl acetate is87.5%. The optimal reaction conditions of Pd-Co/HZSM-5catalyst are as follows:the loading of Co is10%, calcination temperature is723K, reduction temperature is523K, reaction temperature is493K, H2/aldehyde ratio is5, Si/Al ratio of HZSM-5is25and catalyst amount is2.0g. The conversion of acetic acid is55.2%, the selectivity to ethyl acetate is56.2%. It was found that compared with the Pd-Co/HZSM-5catalyst, Pd-Ni/HZSM-5catalyst showed higher activity from experimental results.The results from the hydrogenation and esterification experiments of bimetal bifunctional catalysts showed that Pd-Ni/HZSM-5bimetal bifunctional catalyst revealed better function of hydrogenation. Effects of different Si/Al ratio (140,80,50,38,25) on hydrogenation and esterification reaction performance of Pd/Ni-HZSM-5catalyst were studied. The results of hydrogenation experiments showed that the Si/Al ratio of molecular sieve made no difference to the hydrogenation function of Pd/Ni-HZSM-5catalyst, and the ratio of hydrogenation were all higher than95%. While, the results of esterification reaction showed that it is benefit to esterification reaction when the Si/Al ratio was reduced.HZSM-5were modified by ammonium flouride and phosphotungstic acid, catalysts Pt/F-HZSM-5and Pt/P-HZSM-5were prepared, the experiment condition of Pt/F-HZSM-5and Pt/P-HZSM-5catalysts were optimized. The results showed that the optimal reaction conditions of Pt/F-HZSM-5catalyst are as follows:the content of F is10%, calcination temperature of this catalyst is773K, reduction temperature is538K, reaction temperature is513K, H2/aldehyde ratio is5, Si/Al ratio of HZSM-5is25and catalyst amount is2.0g. The conversion of acetic acid is72.4%, the selectivity to ethyl acetate is89.0%. The optimal reaction conditions of Pt/P-HZSM-5catalyst are as follows: the content of phosphotungstic acid is20%, calcination temperature of this catalyst is773K, reduction temperature is473K, reaction temperature is463K, H2/aldehyde ratio is5, Si/Al ratio of HZSM-5is25and catalyst amount is2.0g. The conversion of acetic acid is65.3%, the selectivity to ethyl acetate is76.3%. |
