The partial oxidation of butane over silica-supported vanadium-phosphorus oxides and the selective oxidation of carbon monoxide in a hydrogen-rich stream over alumina-supported gold.

摘要

As a means to improve control over all selective oxidation reactions, this study focused on the two title systems. Industrially, the partial oxidation of butane to maleic anhydride (MA) occurs over unsupported vanadium-phosphorus oxides (VPO) consisting primarily of (VO)2P2O7 . However, supported catalysts offer many potential benefits over unsupported catalysts. Using XRD, Raman spectroscopy and reaction studies, this study of silica-supported VPO investigated (1){A0}VO(H2PO4) 2-derived catalysts and (2){A0}the VPO-silica interaction of catalysts with phosphorus to vanadium (PN) molar ratios of 1.1.; Both unsupported and silica-supported catalysts derived from VO(H 2PO4)2 were studied. For butane oxidation, the unsupported sample was less active and more selective towards MA than the supported sample. Adding phosphorus to the supported sample increased MA selectivity without decreasing activity. The activity of the catalysts was attributed to alpha1-VOPO4. Propane, butane and pentane oxidation over the unsupported catalyst suggested alkane activation occurs at the secondary carbon.; VPO-silica interaction was studied by comparing hydrophobic and hydrophilic silica. Under certain conditions, the crystalline VPO phases formed depended on the silica type. The VPO-silica interaction was relatively much weaker on hydrophobic silica allowing the formation of (VO)2P 2O7 under mild calcination conditions. However, MA selectivity depended more strongly on the P/V ratio of the catalysts than on preparation method, pretreatment procedure or nature of the silica surface.; The desire to decrease CO concentrations in reformer streams used to power fuel cells has increased interest in selective CO oxidation in H 2-rich environments. XRD, UV-vis, TEM and reaction studies were used to investigate the synthesis and catalytic properties of alumina-supported gold catalysts for this reaction. The use of Mg citrate in the deposition-precipitation synthesis resulted in smaller gold particles than the synthesis in which Mg citrate was not used. Increasing the time between adding the gold solution and adding the Mg citrate to the gamma-Al2O3 support increased the gold loading. Smaller gold particles were more active and more selective towards CO2 than larger gold particles.