Combined carbon dioxide and oxygen process for ethylbenzene dehydrogenation to styrene

1. A process for oxidative dehydrogenation of a hydrocarbon feedstock comprising:

(a) providing an oxidative dehydrogenation reactor system containing a carbon dioxide oxidative dehydrogenation catalyst, said reactor containing an oxygen-selective membrane which separates the reactor into first and second gas passages;

(b) feeding the hydrocarbon feedstock and carbon dioxide to the first gas passage, where the molar feed ratio of carbon dioxide to total hydrocarbon feedstock is 0.1 to 10;

(c) feeding oxygen to the second gas passage to obtain oxygen transported through said membrane, where the molar feed ratio of oxygen to total hydrocarbon feedstock is 0.01 to 1.0;

(d) contacting the hydrocarbon feedstock, carbon dioxide, and transported oxygen with the carbon dioxide oxidative dehydrogenation catalyst to produce a dehydrogenation product stream comprising a dehydrogenated hydrocarbon product, unreacted hydrocarbon feedstock, by-products and offgas;

(e) feeding the dehydrogenation product stream to a primary separation section comprising a condensation system and a separation system; and

(f) cooling and condensing at least a portion of the dehydrogenation product stream in the condensation system, and separating the unreacted hydrocarbon feedstock, condensed by-products and the offgas from the dehydrogenation product stream in the separation system.

2. The process of claim 1 , further comprising feeding the unreacted hydrocarbon feedstock from (d) to the oxidative dehydrogenation reactor system.

3. The process of claim 1 , wherein the hydrocarbon feedstock is a paraffin and the dehydrogenated hydrocarbon product is an olefin.

4. The process of claim 1 , wherein the hydrocarbon feedstock is ethylbenzene and the dehydrogenated hydrocarbon product is styrene.

5. The process of claim 4 , wherein the molar feed ratio of carbon dioxide to ethylbenzene is 0.3 to 8 and the molar feed ratio of oxygen to ethylbenzene is 0.02 to 0.6.

6. The process of claim 1 , wherein the oxidative dehydrogenation reactor system includes an O 2 —ODH reactor upstream from the oxygen-selective membrane-assisted dehydrogenation reactor.

7. The process of claim 1 , wherein the oxygen is supplied by air.

8. The process of claim 1 further comprising

(g) feeding the offgas to a compressor, wherein the offgas comprises carbon monoxide and wherein the product of the compressor is compressed gas comprising carbon monoxide;

(h) feeding the compressed gas into an oxidizer that converts carbon monoxide to carbon dioxide wherein the product of the oxidizer comprises carbon dioxide;

(i) recovering the carbon dioxide from the oxidizer; and

(j) recycling the recovered carbon dioxide to the oxidative dehydrogenation reactor.

9. The process of claim 1 further comprising

(g) feeding the offgas into a compressor, wherein the offgas comprises carbon monoxide and wherein the product of the compressor is compressed gas comprising carbon monoxide;

(h) feeding the compressed gas into a water-gas shift unit wherein the product of the water-gas shift unit is converted gas comprising carbon dioxide;

(i) feeding the converted gas into a separator that separates carbon dioxide in the converted gas wherein the separator product comprises carbon dioxide;

(j) recovering the carbon dioxide from the separator; and

(k) recycling the recovered carbon dioxide to the reactor.

10. The process of claim 1 further comprising

(g) feeding the offgas into an absorber/adsorber that separates carbon dioxide wherein the offgas comprises carbon dioxide and wherein the product of the absorber/adsorber comprises carbon dioxide;

(h) recovering the carbon dioxide from the absorber/adsorber; and

(i) recycling the recovered carbon dioxide to the reactor.

11. The process of claim 1 further comprising

(g) feeding the offgas into an absorber/adsorber that separates carbon dioxide from carbon monoxide wherein the offgas comprises carbon dioxide and carbon monoxide and wherein the product of the absorber/adsorber comprises carbon dioxide and the by-product of the absorber/adsorber comprises carbon monoxide;

(h) feeding the by-product into a water-gas shift unit wherein the product of the water-gas shift unit is converted gas comprising carbon dioxide;

(i) feeding the converted gas into a separator wherein the separator product comprises carbon dioxide; and

(j) recovering the carbon dioxide from the absorber/adsorber and separator; and

recycling the recovered carbon dioxide to the reactor.

12. The process of claim 1 , wherein the reactor contains a selective carbon monoxide and hydrogen oxidation catalyst to convert carbon monoxide to carbon dioxide and to convert hydrogen to water.

13. The process of claim 12 , wherein heat from the conversion of carbon monoxide and hydrogen is used in the dehydrogenation reaction.

14. The process of claim 12 , wherein the membrane itself is a selective carbon monoxide and hydrogen oxidation catalyst.

15. The process of claim 1 , wherein the catalyst comprises a selective carbon monoxide and hydrogen oxidation catalyst disposed on a surface of the membrane.

16. The process of claim 1 , wherein the oxygen is introduced to the reactor at multiple feed points.

17. The process of claim 1 , wherein the process employs a multi-function catalyst for carbon monoxide oxidation and hydrocarbon dehydrogenation.

18. A process for oxidative dehydrogenation of a hydrocarbon feedstock comprising:

(a) providing an oxidative dehydrogenation reactor system containing a carbon dioxide oxidative dehydrogenation catalyst, said reactor containing an oxygen-selective membrane which separates the reactor into first and second gas passages;

(b) feeding the hydrocarbon feedstock and carbon dioxide to the first gas passage, where the molar feed ratio of carbon dioxide to total hydrocarbon feedstock is 0.1 to 10;

(c) feeding oxygen to the second gas passage to obtain oxygen transported through said membrane, where the molar feed ratio of oxygen to total hydrocarbon feedstock is 0.01 to 1.0;

(d) contacting the hydrocarbon feedstock, carbon dioxide, and transported oxygen with the carbon dioxide oxidative dehydrogenation catalyst to produce a dehydrogenation product stream comprising a dehydrogenated hydrocarbon product, unreacted hydrocarbon feedstock, by-products and offgas;

(e) feeding the dehydrogenation product stream to a primary separation section comprising a condensation system and a separation system;

(f) cooling and condensing at least a portion of the dehydrogenation product stream in the condensation system, and separating the unreacted hydrocarbon feedstock, condensed by-products and the offgas from the dehydrogenation product stream in the separation system;

(g) feeding the offgas into a compressor, wherein the offgas comprises carbon dioxide and carbon monoxide and wherein the product of the compressor is compressed gas comprising carbon monoxide and carbon dioxide;

(h) feeding the compressed gas into a separator to produce a stream comprising carbon monoxide and a stream comprising carbon dioxide;

(i) feeding the carbon monoxide stream into an oxidizer to produce carbon dioxide;

(j) recovering the carbon dioxide from the oxidizer; and

(k) recycling the recovered carbon dioxide to the reactor.

19. A process for oxidative dehydrogenation of a hydrocarbon feedstock comprising:

(a) providing an oxidative dehydrogenation reactor system containing a carbon dioxide oxidative dehydrogenation catalyst, said reactor containing an oxygen-selective membrane which separates the reactor into first and second gas passages;

(b) feeding the hydrocarbon feedstock and carbon dioxide to the first gas passage, where the molar feed ratio of carbon dioxide to total hydrocarbon feedstock is 0.1 to 10;

(c) feeding oxygen to the second gas passage to obtain oxygen transported through said membrane, where the molar feed ratio of oxygen to total hydrocarbon feedstock is 0.01 to 1.0;

(d) contacting the hydrocarbon feedstock, carbon dioxide, and transported oxygen with the carbon dioxide oxidative dehydrogenation catalyst to produce a dehydrogenation product stream comprising a dehydrogenated hydrocarbon product, unreacted hydrocarbon feedstock, by-products and offgas;

(e) feeding the dehydrogenation product stream to a primary separation section comprising a condensation system and a separation system;

(f) cooling and condensing at least a portion of the dehydrogenation product stream in the condensation system, and separating the unreacted hydrocarbon feedstock, condensed by-products and the offgas from the dehydrogenation product stream in the separation system;

(g) feeding the offgas into an absorber/adsorber that separates carbon dioxide from carbon monoxide wherein the offgas comprises carbon dioxide and carbon monoxide and wherein the product of the absorber/adsorber comprises carbon dioxide and the by-product of the absorber/adsorber comprises carbon monoxide;

(h) feeding the by-product into a separator wherein the product of the separator is separated gas comprising carbon monoxide;

(i) feeding the separated gas into an oxidizer that converts carbon monoxide to carbon dioxide wherein the oxidizer product comprises carbon dioxide;

(j) recovering the carbon dioxide from the absorber/adsorber and oxidizer; and

(k) recycling the recovered carbon dioxide to the reactor.

20. A process for oxidative dehydrogenation of a hydrocarbon feedstock comprising:

(a) providing an oxidative dehydrogenation reactor system containing a carbon dioxide oxidative dehydrogenation catalyst, said reactor containing an oxygen-selective membrane which separates the reactor into first and second gas passages;

(b) feeding the hydrocarbon feedstock and carbon dioxide to the first gas passage, where the molar feed ratio of carbon dioxide to total hydrocarbon feedstock is 0.1 to 10;

(c) feeding oxygen to the second gas passage to obtain oxygen transported through said membrane, where the molar feed ratio of oxygen to total hydrocarbon feedstock is 0.01 to 1.0;

(d) contacting the hydrocarbon feedstock, carbon dioxide, and transported oxygen with the carbon dioxide oxidative dehydrogenation catalyst to produce a dehydrogenation product stream comprising a dehydrogenated hydrocarbon product, unreacted hydrocarbon feedstock, by-products and offgas;

(e) feeding the dehydrogenation product stream to a primary separation section comprising a condensation system and a separation system;

(f) cooling and condensing at least a portion of the dehydrogenation product stream in the condensation system, and separating the unreacted hydrocarbon feedstock, condensed by-products and the offgas from the dehydrogenation product stream in the separation system;

(g) feeding the offgas into an absorber/adsorber that separates carbon dioxide from carbon monoxide wherein the offgas comprises carbon dioxide and carbon monoxide and wherein the product of the absorber/adsorber comprises carbon dioxide and the by-product of the absorber/adsorber comprises carbon monoxide;

(h) feeding the by-product into a separator that separates carbon monoxide wherein the product of the separator is separated gas comprising carbon monoxide;

(i) feeding the separated product into a water-gas shift unit wherein the product of the water-gas shift unit is converted gas comprising carbon dioxide;

(j) feeding the converted gas into a separator that separates carbon dioxide in the converted gas wherein the separator product comprises carbon dioxide;

(k) recovering the carbon dioxide from the absorber/adsorber and separator; and

(l) recycling the recovered carbon dioxide to the reactor.