Catalyst for oxidn. of cyclic or acyclic alkane(s) to alkene(s), unsatd. aldehydes and acids - comprises nickel molybdate opt. impregnated with ammonium phosphate and mixed with tellurium molybdate, esp. for industrial scale conversion of propane to propylene, acrolein and acrylic acid

摘要

The catalyst for oxidn. of alkanes into alkenes and the corresp. ethylenically unsatd. aldehydes and carboxylic acids, has the formula: (NiO)x.(MoO3)y.(Te2MoO7)z.(P2O5)t (I); x,y,z and t are the respective percentages (by wt.) of the active agents, Ni, Mo, Te and P, and (x+y) = 0.1-15%, z = 0-10%, (0.1-10%) t = 0-10% and y/x = 1.2-9. Pref., the catalyst has a specific surface of 20-50 m2/g and an ave. particle size of 0.1-5mm. The catalyst is unsupported or mixed with a diluent or a solid or inert support. Pref., the alkane is contacted with O2(-contg. gas) in a mol. ratio alkane to O2 of 0.1-30, in the catalyst at 400-700 deg.C and 0.5-10 bars, e.g., for an apparent contact time of 0.01-30 s. The catalysts are prepd. by (i) preparing a first powdered precursor comprising a Ni molybdate of formula (NiO)x.(MoO3)y (II) from an aq. soln. of Ni nitrate and an aq. soln. of molybdic acid; (ii) opt. preparing a second powdered precursor comprising Te molybdate of formula Te2MoO7 (III) from an aq. soln. of ammonium paramolybdate and an aq. soln. of telluric acid; (iii) impregnating the precursor (II) with an aq. soln. of (NH4)2HPO4 to obtain a powdered impregnated precursor of formula (NiO)x.(MoO3)y.(P2O5)t (IV) and (iv) homogeneously mixing calculated amts. of the precursors (IV) and (III) to form the required catalyst (NiO)x.(MoO3)y.(Te2MoO7)z.(P2O5)t (I). The precursor (II) and/or the precursor (III) and/or the impregnated precursor (IV) and/or the final catalyst (I) may each be thermally treated at 200-700 deg.C for 15 mins. - 24 hrs. The catalyst is activated by a thermal treatment comprising raising the catalyst temp. stagewise to the alkane oxidn. temp. in the oxidn. reactor and maintaining it at the temp. for 5 mins. - 10 hrs. before introducing the reaction mixt. into the reactor. USE/ADVANTAGE - The catalysts are useful for oxidn. of 2-20C opt. cyclic alkanes into alkenes and the corresp. unsatd. aldehydes and carboxylic acids, esp. for industrial scale conversion of propane into a mixt. of propylene, acrolein and acrylic acid and conversion of isobutane into a mixt. of isobutene, methacrolein and methacrylic acid. The catalysts give controlled and selective oxidn. of alkenes in the gas phase at elevated temps. to pref. ethylenically unsatd. prods. without excessive conversion into total oxidn. prods., e.g., CO, CO2 and H2O.