Dehydrogenation Of C4 Paraffins To C4 Olefins

Dehydrogenation of light alkanes is a valuable approach to produce alkenes from feedstocks of low-cost saturated hydrocarbons. The dehydrogenation is commercially carried out with platinum metal catalysts and supported chromium oxide catalysts. Important drawbacks still exist with the implementation of this catalytic reaction. First, alkane dehydrogenation is an endothermic process, it requires relatively high temperatures and low pressures. Under these conditions, thermal cracking and olefin polymerization are easy to appear. In addition, coke formation is also promoted with the alkane transformation being quite unselective given all C?H and C?C bonds display close reactivity. The key factor to achieve above process is development of higher efficent catalyst.VO_x catalysts were respectively prepared via high temperature solid state reaction and impregnation methods. The samples were characterized by N₂ adsorption-desorption, XRD, TPR and FT-IR techniques. The results showed that the physical structures, reduction properties and reaction performances of VOx catalysts are greatly influenced by preparation methods. Reaction performances of the catalysts were also studied. The results showed that the calcination temperature and loading effected on the activation of catalysts. The reaction conditions such as reaction temperature, feed composition, weight hourly space velocity (WHSV) and reaction time were investigated by micro-reaction equipment under the optimal preparation conditions of catalysts. The performances of VO_x/FCC spent catalyst free oxygen were higher than that with oxygen. The activities of VO_x/Al₂O₃ were higher, while the selectivity is similar in the dehydrogenation without oxygen.In order to improve the reaction performance and stability of the catalysts, additive metals (K, Sn , Ni, Co, Cr and Ce) are introduced to the catalysts. It is found that the activity of catalysts decreased after introduction of K and Sn, however, the selectivity to C4 olefins and the stability of the catalysts increased. The catalytic activity was signi?cantly increased and the products selectivity was slightly influenced with the adding of Ni.