Propylene is one of the most important chemical building blocks.With the fast economic development,the consumption of propylene from chemical industry is increasing rapidly,which cause traditional processes for propylene production(stream cracking and fluid catalytic cracking)cannot meet the market demand.However,in recent years,the large-scale exploitation of shale gas makes an increase in propane supply.Thus,propane dehydrogenation(PDH)process becomes more attractive.Nowadays,commercial PDH processes use Pt-based or Cr Ox based catalyst.Nevertheless,they are either expensive or toxic,which constrains the development of PDH industry.Therefore,it is essential to find out an alternative catalyst.Previous studies have found that VOx-based catalyst can be used in PDH process and it is a promising catalyst due to its low cost,low toxicity and excellent regeneration stability.However,the activity of VOx-based catalyst is lower than Pt based and Cr Ox based catalyst.Thus,the aim of this thesis is to improve the activity of VOx-based catalysts and we focus on the interaction between VOx and support.The structures of catalysts are resolved and structure-performance correlations are proposed,which provides a practical method to improve PDH activity and gives insights into the catalyst design.Firstly,the nature of anchoring site of VOx onγ-Al2O3 and its impact to PDH reaction is studied.Along with diffuse reflectance infrared Fourier transform spectroscopy,Raman spectroscopy,it is found that VOx prefer anchoring on the HO-μ1-Al V site while show no preference between HO-μ1-Al VI and HO-μ2-Al.Catalytic performance test shows VOx anchoring on HO-μ1-Al V site have higher TOF than anchoring on Al VI-OH or(Al)2-OH.With the help of in situ Raman study,we find VO-μ1-Al V bonds are easily reduced and low coordinated V species forms when VOxanchors on HO-μ1-Al V,which leads to a better C-H activation.Secondly,this thesis describes the structure and catalytic properties of VOx/Zr O2catalyst.When using Zr O2 as support,the catalyst shows six times higher turnover frequency(TOF)than using commercialγ-Al2O3.Combining H2-temperature program reduction,in situ Raman,X-ray photoelectron spectroscopy and theoretical studies,we find that the interaction between VOx and Zr O2 can facilitate the reduction of V-O bonds,including V=O,V-O-V and V-O-Zr.The promoting effect on PDH activity could be attributed to the formation of low coordinated V species in VOx/Zr O2 which is more active in C-H activation. |