ساخت و بهينه سازي كاتاليست هاي واناديل پيروفسفات (VPO)

Preparation and Optimization of VPO Catalysts

Vanadium-phosphorus oxides (VPO) are the most widely used catalysts for the selective oxidation of butene and n-butane to maleic anhydride. In the present study the vanadium-Phosphorus-Oxide (VPO) catalysts with different p/v atomic ratio and different reflux time were prepared using alcohol based preparation procedures. The effect of reduction agents (benzyl alcohol or allyl alcohol) and calcinations atmosphere (air or pure oxygen) were investigated. A comparative study has been conducted between promoted VPO catalysts (with molybdenum) and unpromoted VPO catalysts. Effects of P/V atomic ratio, reflux time and calcinations atmosphere on crystalline structure were studied. In addition effects of P/V atomic ratio, reflux time, reduction agent and presence of promoter on surface area, reduction temperature and active sites were interpreted. The catalysts have been characterized by X-Ray diffraction (XRD) spectroscopy, Fourier Infrared Spectroscopy (FT- IR), BET, SEM and ammonia TPD study. Prepared catalysts were found to be effective for the oxidation of n- butane to maleic anhydride (MA). With the addition of Mo promoter, high n-butane selectivity to maleic anhydride (98%) was observed at 425 ｰC.