A Study On The Higher Alcohol Synthesis From Syngas On CuCo Catalyst Prepared By Co-Reduction Method

Higher alcohol,which consists of the mixed alcohols with one or more carbon atoms,is one of the most important industrial chemicals and has been utilized as the transportation fuel,fuel additives and chemical intermediates in some synthesis reactions.Recently,most reaserchers have focused their attention on the synthesis of higher alcohol since its promising alpplications in the future.Among various synthesis technologies for higher alcohol,converting the synthesis gas(syngas)which is obtained from the coal gasification to higher alcohol on the suitable catalysts is considered as a promising process.Many catalysts which can achieve syngas-higher alcohol conversion have been reported,but the modified Fischer-Tropsch synthesis catalyst(CuCo catalyst)is so far considered to be one of the most feasible catalysts for industrial applications.Compared with other catalysts,the CuCo catalyst just needs relatively mild reaction conditions,and its selectivity towards higher alcohol is relatively high.In this dissertation,the CuCo catalyst is used as the research object and its Cu/Co ratios are regulated via a co-reduction method.The impacts of Cu/Co ratio diference on the performance of syngas-higher alcohol conversion are systematically studied by means of XRD,XPS,TEM,SEM,TPD,TPR,in situ DRIFTS,etc.Finally,this dissertation also discusses the structural evolution of CuCo catalyst under the reaction conditions.The main research contents and results of this dissertation are listed in the following:1 A series of catalysts with different Cu/Co ratios are prepared via co-reduction method.The effects of Cu/Co ratio difference on the performance of syngas-higher alcohols conversion are studied.The catalysts would be pretreated in the H2 atmosphere at 300? for 4 hours to be reduced.After that,the syngas would be purged into the reaction vessel and the reaction would occur.The exprimental results demonstrate that the Cu0.25Co0.75 catalyst with Cu/Co molar ratio of 0.3 could perform the highest catalytic activity at the temperature of 250?,the pressure of 3.0 MPa,and the space velocity of 3900 h-1.Specifically,the Cu0.25Co0.75 catalyst achieves a CO conversion rate of 71.27%,a space-time yield of 147.65 g kg-1 h-1 of total alcohol,and a high C2+OH/MeOH ratio of 4.40.The results of H2-TPR and CO-TPD show that the Cu0.25Co0.75 catalyst has a low H2 reduction temperature and a high CO desorption temperature,suggesting the high CO adsorption capacity of Cu0.25Co0.75 catalyst.For Co-based catalysts,the strong CO adsorption boosts the conversion of CO,and a large amount of C*adsorbates are crucial to the alcohol synthesis.In situ DRIFTS results show that the surface of Cu0.25Co0.75 catalyst is more conducive to the growth of carbon chains.2 Based on the above results,the HAS reaction time of Cu0.25Co0.75 catalyst is prolonged to investigate the possible structural evolution.It is worth noting that the catalytic activity could be obviously changed with the longer reaction time.Some characterizations prove that the Co2C phase would be formed on the surface of catalyst,and the formed Co2C can work as Cu to boost the formation of alcohol.Correspondingly,the content of Co on the surface of catalyst would decrease,resulting in the weakening of the dissociative adsorption of CO and the reduction of the conversion rate of CO.