Oxidative dehydrogenation process with hydrocarbon moderator gas and reduced nitrogen feed
Oxidative dehydrogenation includes: (a) providing a gaseous feed stream to a catalytic reactor, the feed stream comprising a dehydrogenation reactant, oxygen, superheated steam, hydrocarbon moderator gas and optionally nitrogen, wherein the molar ratio of moderator gas to oxygen in feed stream is typically from 4:1 to 1:1 and the molar ratio of oxygen to nitrogen in the feed stream is at least 2; (b) oxidatively dehydrogenating the reactant in the reactor to provide a dehydrogenated product enriched effluent product stream; and (c) recovering dehydrogenated product from the effluent product stream. One preferred embodiment is a process for making butadiene including dimerizing ethylene to n-butene in a homogeneous reaction medium to provide a hydrocarbonaceous n-butene rich feed stream and oxidatively dehydrogenating the n-butene so formed.
1. A method of oxidatively dehydrogenating a dehydrogenation reactant comprising:
(a) providing a gaseous feed stream to a catalytic reactor, the feed stream comprising a dehydrogenation reactant, oxygen, superheated steam and a hydrocarbon moderator gas,
wherein hydrocarbon moderator gas is added to the dehydrogenation reactant to adjust the amount of moderator gas in the gaseous feed stream; and
wherein the molar ratio of hydrocarbon moderator gas to oxygen in the feed stream is from 50:1 to 0.5:1;
(b) oxidatively dehydrogenating the dehydrogenation reactant in the reactor to generate an effluent product stream enriched in a dehydrogenated product derived from said dehydrogenation reactant; and
(c) recovering said dehydrogenated product from the effluent product stream.
2. The method according to claim 1 , wherein the molar ratio of hydrocarbon moderator gas to oxygen in the feed stream is from 8:1 to 0.5:1.
3. The method according to claim 1 , wherein the molar ratio of hydrocarbon moderator gas to oxygen in the feed stream is from 3:1 to 1.5:1.
4. The method according to claim 1 , wherein the feed stream optionally comprises nitrogen and the molar ratio of oxygen:nitrogen in the feed stream is at least 0.5.
5. The method according to claim 2 , wherein the molar ratio of oxygen:nitrogen in the feed stream is at least 2.
6. The method according to claim 1 , wherein the molar ratio of oxygen to dehydrogenation reactant in the feed stream is from 0.2:1 to 0.4:1.
7. The method according to claim 1 , wherein the molar ratio of oxygen to dehydrogenation reactant in the feed stream is from 0.4:1 to 0.8:1.
8. The method according to claim 1 , wherein the catalytic reactor has disposed therein a ferrite catalyst.
9. The method according to claim 1 , further comprising recovering from the effluent product stream a heat recovery stream having a heating value of greater than 5,000 Btu/lb.
10. The method according to claim 1 , wherein said moderator gas comprises an alkane.
11. The method according to claim 10 , wherein said moderator gas comprises methane, ethane, propane, butane, pentane or hexane.
12. The method according to claim 11 , wherein said moderator gas comprises methane.
13. The method according to claim 1 , wherein said dehydrogenation reactant comprises n-butenes and said dehydrogenated product comprises butadiene.
14. The method according to claim 1 , further comprising:
(d) recovering moderator gas from the from the effluent product stream; and
(e) recycling moderator gas recovered from the effluent product stream to the reactor.
15. The method according to claim 14 , wherein from 50% by weight up to 97.5% by weight of the moderator gas in the effluent product stream is recovered and recycled to the reactor.
16. A method of producing butadiene from an ethylene raw material feed comprising:
(a) providing ethylene to a homogeneous reaction medium housed in a dimerization reactor;
(b) dimerizing ethylene to n-butene in the homogeneous reaction medium to provide a hydrocarbonaceous n-butene rich feed;
(c) mixing said hydrocarbonaceous butene rich feed with steam, oxygen and a hydrocarbon moderator gas to form an oxidative dehydrogenation reactor feed stream and superheating said oxidative dehydrogenation reactor feed stream to a temperature of at least 204° C. (400° F.), wherein the molar ratio of hydrocarbon moderator gas to oxygen in the feed stream is from 8:1 to 0.5:1;
(d) feeding the an oxidative dehydrogenation reactor feed stream to an oxidative dehydrogenation reactor;
(e) oxidatively dehydrogenating the n-butene reactant in the oxidative dehydrogenation reactor to generate an effluent product stream enriched in butadiene derived from said n-butene; and
(f) recovering said butadiene from the effluent product stream.
17. The method according to claim 16 , wherein the homogeneous reaction medium in the dimerization reactor comprises a homogeneous catalyst comprising a nickel compound and an alkyl aluminum co-catalyst.
18. The method according to claim 17 , wherein the homogeneous catalyst comprises a nickel phosphine oxide and ethyl aluminum dichloride.
19. The method according to claim 16 , wherein the n-butene in the oxidative dehydrogenation reaction feed stream are predominantly 2-butenes.
20. A method of co-producing butene-1 and butadiene from an ethylene raw material feed comprising:
(a) providing ethylene to a homogeneous reaction medium including a homogeneous titanium/aluminum catalyst housed in a dimerization reactor;
(b) dimerizing ethylene predominantly to butene-1 in the homogeneous reaction medium to provide (i) a hydrocarbonaceous butene-1 rich feed and (ii) a butene-1 rich product stream;
(c) withdrawing and purifying the butene-1 rich product stream and recovering butene-1 therefrom;
(d) mixing said hydrocarbonaceous butene rich feed with steam, oxygen and a hydrocarbon moderator gas to form an oxidative dehydrogenation reactor feed stream and superheating said oxidative dehydrogenation reactor feed stream to a temperature of at least 204° C. (400° F.), wherein the molar ratio of hydrocarbon moderator gas to oxygen in the feed stream is from 8:1 to 0.5:1;
(e) feeding the an oxidative dehydrogenation reactor feed stream feed stream to an oxidative dehydrogenation reactor;
(f) oxidatively dehydrogenating the n-butene in oxidative dehydrogenation reactor to generate an effluent product stream enriched in butadiene derived from said n-butene; and
(g) recovering said butadiene from the effluent product stream.
21. The method according to claim 1 , wherein natural gas is provided to the feed stream.
22. The method according to claim 1 , wherein the hydrocarbon moderator gas:reactant hydrocarbon molar ratio is from 3 to 12 and the hydrocarbon moderator gas:oxygen molar ratio is from 8:1 to 45:1.