Multi-staged catalyst systems and process for converting alkanes to alkenes and to their corresponding oxygenated products
Alkenes, unsaturated saturated carboxylic acids, saturated carboxylic acids and their higher analogues are prepared cumulatively from corresponding alkanes utilizing using a multi-staged catalyst system and a multi-stage process which comprises steam cracking of alkanes to corresponding alkenes at flame temperatures and at short contact times in combination with one or more oxidation catalysts for catalytically converting the corresponding alkenes to further corresponding oxygenated products using short contact time reactor conditions.
1. A multi-staged catalyst system for converting a C 3 -C 8 alkane to the corresponding C 3 -C 8 alkene, the corresponding C 3 -C 8 oxygenate, and mixtures thereof, said catalyst system comprising:
(A) a first catalyst capable of catalyzing the full oxidation of the C 3 -C 8 alkane to produce heat, carbon dioxide and steam, and comprising (a) at least one metal selected from the group consisting of Ag, Au, Ir, Ni, Pd, Pt, Rh, Ru, alloys thereof and combinations thereof; and (b) at least one modifier selected from the group of metal oxides including the metals Bi, In, Mg, P, Sb, Zr, Group 1-3 metals, lanthanide metals and combinations thereof, the first catalyst being situated in a first reaction stage comprising a temperature between 500° C. and 1000° C. and a residence time no greater than 100 milliseconds;
(B) a second catalyst comprising an activated zeolite and capable of catalyzing the endothermic dehydrogenation of the C 3 -C 8 alkane to produce the corresponding C 3 -C 8 alkene, in the presence of the heat and carbon dioxide produced using the first catalyst, in a second reaction stage comprising a temperature greater than 500° C. and a residence time no greater than 100 milliseconds; and
(C) a third catalyst capable of selective oxidation of the corresponding C 3 -C 8 alkene, produced using the second catalyst, to produce C 3 -C 8 oxygenates, in a third reaction stage comprising a temperature greater than 300° C.
2. The multi-staged catalyst system according to claim 1 , wherein at least one of the first, second and third catalysts is impregnated on a metal oxide support.
3. The multi-staged catalyst system according to claim 1 , wherein the first catalyst further comprises: (c) at least one metal oxide including the metals Cd, Co, Cr, Cu, Fe, Mn, Ni, Nb, Ta, V and Zn.
4. The multi-staged catalyst system according to claim 1 , wherein the second catalyst further comprises phosphorous; and the third catalyst comprises a selective oxidation catalyst comprising at least one oxide of a metal selected from the group consisting of Mo, Fe, P and V.