Selective isomerization of 2-methylpentane and 4-methyl-1-pentene over the molybdenum oxide supported on aluminum orthophosphate

In this work,we have focused our attention on catalytic activity and selectivity of molybdenum oxide supported alpo4 (moalp) since studies on this kind of catalysts are much fewer and its composition seems to lead to better acid characteristics. the alpo4 (alp) used as a support was synthetized by coprecipitation and the catalysts moalp (4 wt %) was prepared by impregnation of alp with the ammonium heptamolybdate (nh4)6mo7o24·4h2o. this system was characterized in detail using bet surface area measurement,porosimetry,x-ray diffraction (xrd),ftir spectroscopy,temperature programmed reduction (tpr) and x-ray photoelectron spectroscopy (xps). bet and porosimetry analysis showed that this solid is mesoporous. tpr and xps indicated an in situ reduction of this catalyst by hydrogen at 450°c which enabled to reduce mo(vi) to lower oxidation states. the catalytic activities and isomerization selectivity's of 2-methylpentane (2mp) and 4-mthyl-1-pentene (4m1pene) using moalp system,at atmospheric pressure yield a mixture of cracked and isomerized compounds were interpreted in terms of dual sites on the catalyst surface. the mechanism of hydrocarbon isomerization on moalp has been explained by a bifunctional mechanism,in which dehydrogenation - hydrogenation occurs on metallic sites and skeletal isomerization takes place on acidic sites. from correlation with xps measurements,it can be concluded that mo(v) species are responsible for acidic isomerization and that mo(iv) species exhibit metallic dehydrogenation properties. © 2017,university of mohammed premier oujda morocco.