| 摘要 |
<p>Catalytic material is provided by a composition comprising the elements vanadium, non-water-contained hydrogen, phosphorus and non-water-contained oxygen. The VHPO elements are present in a relatively fixed atomic ratio range, there being more non-water-contained oxygen present than phosphorus by an atomic ratio of greater than five to one. The catalytic material comprises an anhydrous primary component having vanadium of mixed valence, hydrogen, phosphorus and oxygen in an empirical relationship defined by VHxPOy, wherein "x" has an average value in a range from about 1.29 to about 1.40, and "y" has an average value in a range from about 5.46 to about 5.55. The anhydrous VHPO catalytic material may also be described by a structural formula (VO)m(VO2)nH2n(PO4)n(P2O7)?, wherein m + n = 3, "m" has an average value in a range from about 0.90 to about 1.07, and "n" has an average value in a range from about 1.03 to about 2.10. The primary component is mostly amorphous and in its substantially anhydrous form is characterized by a powder X-ray diffraction pattern having board peaks with CuX or d-spacings of 4.30, 4.17 and 3.09.ANG.. The catalytic material is prepared by a process comprising the steps of reducing vanadium pentoxide with a reducing agent in an aqueous solution of phosphoric acid, followed by the step of oxidizing a portion of the vanadium species with an oxidizing agent to form a slurry of precipitate containing vanadium(IV) and vanadium(V) in contact with a water solution containing vanadium(IV). Subsequent removal of free water from the slurry provides a material which may be further heated to drive off water of hydration and thereafter calcined to fix the relative amounts of the VHPO elements in the anhydrous material. Freshly prepared catalytic material provides relatively high yields upon its initial use in the catalytic coxidation of hydrocarbon feedstocks, such as n-butane and benzene, to maleic anhydride.</p> |
