Study On Preparation And Performances Of Catalyst For The Synthesis Of 1,3-butadiene Via Two-step Process From Ethanol

1,3-butadiene is an important chemical product in petrochemical industry which is widely used in producing synthetic rubber. In the 1920 s, the bioethanol method was industrially used as the feed of the production of 1,3-butadiene when oil extraction was extraordinarily expensive. However, nowadays butadiene is mainly produced by two methods: dehydrogenation of butane and butene and isolation from C4 steam cracker fractions. Aware of the gradually decreasing resources of non-renewable oil and the deterioration in environment, there is a strong urge to reduce the usage of this natural resource, which incentive the innovation in producing 1,3-butadiene. Many researchers have showed great interest in the ways from renewable feedstock to produce butadiene and with the technological advancement in bioethanol industry, bioethanol again, gradually becomes a potential feedstock in the formation of butadiene.In this work, the two-step process to produce butadiene from ethanol over ZrO2/SiO2 catalyst was studied, and focused on the structure-activity relationship of ZrO2/SiO2 catalyst for this process. The influence of process condition on the catalytic activity and the deactivition mechanism of catalyst were investigated.It was showed that the ZrO2/ SiO2 prepared by Sol-gel method appeared the higher selectivity for butadiene. The mixing between compounds was more uniform, has showed best dispersion of ZrO2 on SiO2 and the largest specific surface area. According to orthogonal optimization experiment result, the optimized calcination temperature was 650?, nitric acid concentration was 2 mol/L, mixing temperature was 30? and content of zironia was 2wt%, respectively. Furthermore, catalyst only possessed Lewis acid sites, and the strength of weak acid sites became stronger with the increase of zirconium content, but the specific surface area was gradually decreased. These results could illustrate that the Lewis acidic sites would be necessary for the object reaction.The optimized reaction conditions were obtained through orthogonal experimental design. The mole ratio of ethanol to acetaldehyde was 3.5:1, WHSV was 1.8 h-1, reaction temperature was 320?. Under these conditions, the selectivity of butadiene was reached to 61.06%. The conversion of ethanol and actaldehyde were 41.38% and 52.56%, respectively.The study on the deactivation of ZrO2/SiO2 catalyst showed that the decrease of weak acid sites and specific surface area would be caused by the carbon deposition on the surface of catalyst, which were responsible for the catalyst deactivition. In addition, it was also found that there were mainly two kinds of deposited carbonaceous species, which could be eliminated at lower temperature name as L carbonaceous species and the coke that can be eliminated at higher temperature name as H carbonaceous species. With the increase of reaction temperature, the proportion of H species was gradually increased. With the increase of reaction temperature, the amount of carbon deposition was gradually reduced, indicating that the L carbonaceous species would occupy a larger proportion than H ones.