Method of producing a fuel additive

1. A method of producing a fuel additive, comprising:

passing a feed stream comprising C4 hydrocarbons through a butadiene extraction unit producing a first process stream;

passing the first process stream through a methyl tertiary butyl ether unit producing a second process stream and a methyl tertiary butyl ether product;

passing the second process stream through a hydration unit producing the fuel additive and a recycle stream, wherein the second process stream comprises butene, and wherein at least a portion of the butene present in the second process stream is converted to butanol within the hydration unit;

passing the recycle stream through a recycle hydrogenation unit; and

recycling the hydrogenated recycle stream from the recycle hydrogenation unit to a steam cracker unit and/or to the feed stream.

2. The method of claim 1 , wherein a source of the feed stream comprises a product of an olefin cracking process and/or an olefin production process.

3. The method of claim 1 , wherein the feed stream comprises at least one of propane, propylene, ethyl acetylene, vinyl acetylene, 1,3-butadiene, 1,2-butadiene, isobutylene, cis-2-butene, trans-2-butene, 1-butene, isobutane, or n-butane.

4. The method of claim 1 , wherein the butadiene extraction unit comprises extractive distillation, solvent degassing, solvent regeneration and/or solvent recovery.

5. The method of claim 1 , wherein the feed stream comprises butadiene, and wherein the first process stream withdrawn from the butadiene extraction unit comprises less than or equal to 5% butadiene by weight.

6. The method of claim 1 , further comprising contacting the first process stream with a catalyst within the methyl tertiary butyl ether unit, wherein the catalyst comprises an acid-type ion-exchange resin; and

wherein the second process stream exiting the methyl tertiary butyl ether unit comprises less than or equal to 5% isobutylene by weight.

7. The method of claim 1 , wherein a temperature within the methyl tertiary butyl ether unit is 15° C. to 150° C. and a pressure within the methyl tertiary butyl ether unit is 500 kiloPascals to 2800 kiloPascals.

8. The method of claim 1 , wherein methanol and isobutylene are present in the methyl tertiary butyl ether unit in a molar ratio of one mole of isobutylene to 0.05 moles to 10 moles of methanol.

9. The method of claim 1 , wherein the first process stream comprises isobutylene, and wherein greater than or equal to 75% by weight of the isobutylene present in the first process stream is converted to methyl tertiary butyl ether within the methyl tertiary butyl ether unit.

10. The method of claim 1 , further comprising withdrawing the methyl tertiary butyl ether product from the methyl tertiary butyl ether unit;

wherein the purity of the methyl tertiary butyl ether product is greater than or equal to 95%.

11. The method of claim 1 , wherein the second process stream comprises butadiene prior to passing through the hydration unit, and wherein the second process stream comprises less than or equal to 3.0% butadiene by weight prior to passing through the hydration unit.

12. The method of claim 1 , further comprising contacting the second process stream with a catalyst within the hydration unit, wherein the catalyst comprises at least one of phosphoric acid, hypophosphorous acid, ion-exchange resin, sulfur, polystyrene, polymer, or niobium oxide.

13. The method of claim 1 , wherein a temperature within the hydration unit is 30° C. to 250° C. and a pressure within the hydration unit is 500 kiloPascals to 20,000 kiloPascals.

14. The method of claim 1 , wherein greater than or equal to 90% by weight of the butene present in the second process stream is converted to butanol within the hydration unit.

15. The method of claim 1 , further comprising withdrawing a fuel additive product from the hydration unit.

16. The method of claim 15 , wherein the fuel additive product comprises at least one of 2-butanol, tert-butyl alcohol, or C4 dimer;

wherein the fuel additive product comprises 1 to 50 weight % of the at least one of 2-butanol, tert-butyl alcohol, or C4 dimer; and

wherein the fuel additive product comprises 1 to 25 weight % of trimethylpentane.

17. The method of claim 15 , wherein an octane number of the fuel additive product is greater than 85 in accordance with the Anti-Knock Index.

18. The method of claim 15 , wherein a Reid vapor pressure of the fuel additive product is less than or equal to 15 kiloPascals.

19. The method of claim 1 , wherein the recycle stream comprises butene, and wherein greater than or equal to 90% by weight of the butene present in the recycle stream is converted to butane within the recycle hydrogenation unit.

20. A method of producing a fuel additive, comprising:

passing a feed stream comprising C4 hydrocarbons through a catalytic cracking unit;

passing the feed stream through a butadiene extraction unit producing a first process stream, wherein the butadiene extraction unit comprises extractive distillation, solvent degassing, solvent regeneration, solvent recovery, or a combination thereof, and wherein the feed stream comprises butadiene and wherein the first process stream withdrawn from the butadiene extraction unit comprises less than or equal to 5% butadiene by weight;

withdrawing a butadiene product from the butadiene extraction unit;

passing the first process stream through a methyl tertiary butyl ether unit producing a second process stream and a methyl tertiary butyl ether product, wherein methanol and isobutylene are present in the methyl tertiary butyl ether unit in a molar ratio of one mole of isobutylene to 0.1 moles to 5 moles of methanol;

withdrawing the methyl tertiary butyl ether product from the methyl tertiary butyl ether unit, wherein the first process stream comprises isobutylene and wherein greater than or equal to 75% by weight of the isobutylene present in the first process stream is converted to methyl tertiary butyl ether within the methyl tertiary butyl ether unit;

passing the second process stream through a hydration unit producing the fuel additive and a recycle stream, wherein a temperature within the hydration unit is 30° C. to 250° C., a pressure within the hydration unit is 500 kiloPascals to 20,000 kiloPascals, and wherein the second process stream comprises butene and wherein 1.0 to 5090% by weight of the butene present in the second process stream is converted to butanol within the hydration unit;

withdrawing the fuel additive from the hydration unit, wherein the fuel additive comprises at least one of 2-butanol, tert-butyl alcohol, or a C4 dimer;

passing the recycle stream through a recycle hydrogenation unit, wherein the recycle stream comprises butene and wherein greater than or equal to 90% by weight of the butene present in the recycle stream is converted to butane within the recycle hydrogenation unit; and

recycling the hydrogenated recycle stream from the recycle hydrogenation unit to the catalytic cracking unit.