Method of producing a fuel additive

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

passing a first process stream comprising C4 hydrocarbons through a methyl tertiary butyl ether synthesis unit producing a first recycle stream and a methyl tertiary butyl ether product;

passing the first recycle stream through a hydration unit producing the fuel additive and a second recycle stream;

passing the second recycle stream through a recycle hydrogenation unit, wherein at least a portion of butene present in the second recycle stream is converted to butane within the recycle hydrogenation unit;

passing the second recycle stream from the recycle hydrogenation unit and through a deisobutanizer unit; and

recycling the second recycle stream from the deisobutanizer unit to the methyl tertiary butyl ether synthesis unit;

wherein greater than or equal to 40% by weight of any butane present in the second recycle stream is converted to isobutylene in the deisobutanizer unit prior to recycling to the methyl tertiary butyl ether synthesis unit.

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

3. The method of claim 1 , further comprising passing a first feed stream through a hydrocracking unit, forming a second feed stream and passing the second feed stream through a selective hydrogenation unit prior to passing through the methyl tertiary butyl ether synthesis unit, forming the first process stream.

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

wherein the first recycle stream exiting the methyl tertiary butyl ether synthesis unit comprises less than or equal to 5% isobutylene by weight; and

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

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

6. The method of claim 1 , wherein methanol and isobutylene are present in the methyl tertiary butyl ether synthesis unit in a molar ratio of one mole of isobutylene to 0.1 mole to 5 moles of methanol.

7. The method of claim 1 , wherein greater than or equal to 90% by weight of any isobutylene present in the first process stream is converted to methyl tertiary butyl ether within the methyl tertiary butyl ether synthesis unit, and further comprising withdrawing the methyl tertiary butyl ether product from the methyl tertiary butyl ether synthesis unit.

8. The method of claim 1 , wherein the first recycle stream comprises less than or equal to 3.0% by weight butadiene prior to passing through the hydration unit.

9. 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.

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

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

12. The method of claim 11 , wherein the fuel additive product comprises at least one of 2-butanol, tert-butyl alcohol, or a C4-dimer, and wherein the fuel additive product comprises 1 to 25 weight % of trimethylpentane.

13. The method of claim 12 , wherein an octane number of the fuel additive product is greater than or equal to 80 in accordance with the Anti-Knock Index.

14. The method of claim 12 , wherein a Reid vapor pressure of the fuel additive product is less than or equal to 55 kiloPascals.

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

16. The method of claim 1 , further comprising drying the second recycle stream before or after passing to the recycle hydrogenation unit.

17. The method of claim 1 , further comprising withdrawing a secondary hydrocarbon stream from the hydrocracking unit and passing the secondary hydrocarbon stream through a total hydrogenation unit to produce a total hydrogenated stream, the total hydrogenation unit converting olefins present in the secondary hydrocarbon stream to alkanes; and

feeding the total hydrogenated stream to the deisobutanizer unit.

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

passing a first feed stream comprising C4 hydrocarbons through a fluid catalytic cracking unit forming a second feed stream;

passing the second feed stream through a hydrogenation unit forming a first process stream;

passing the first process stream through a methyl tertiary butyl ether synthesis unit producing a first recycle stream, wherein methanol and isobutylene are present in the methyl tertiary butyl ether synthesis unit in a molar ratio of one mole of isobutylene to 0.1 mole to 2 moles of methanol;

withdrawing a methyl tertiary butyl ether product from the methyl tertiary butyl ether synthesis unit;

withdrawing the first recycle stream from the methyl tertiary butyl ether synthesis unit and passing the first recycle stream through a hydration unit producing the fuel additive and a second recycle stream, wherein a temperature within the hydration unit is 30° C. to 200° C., a pressure within the hydration unit is 500 kiloPascals to 10,000 kiloPascals, and wherein greater than or equal to 90% by weight of any butene present in the first recycle 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 C4 dimer;

passing the second recycle stream through a recycle hydrogenation unit, wherein at least a portion of butene present in the second recycle stream is converted to butane within the recycle hydrogenation unit;

passing the second recycle stream from the recycle hydrogenation unit and through a deisobutanizer unit forming an isobutylene-containing recycle stream; and

recycling the isobutylene-containing recycle stream from the deisobutanizer unit to the methyl tertiary butyl ether synthesis unit;

wherein greater than or equal to 40% by weight of any butane present in the second recycle stream is converted to isobutylene in the deisobutanizer unit prior to recycling to the methyl tertiary butyl ether synthesis unit;

wherein an octane number of the fuel additive is greater than or equal to 83 in accordance with the Anti-Knock Index; and

wherein a Reid vapor pressure of the fuel additive is 8 kiloPascals to 53 kilopascals.

19. The method of claim 18 , wherein the deisobutanizer unit comprises a deisobutanizer column, an isomerization unit, and a dehydrogenation unit in series; and wherein the deisobutanizer column is operated at a temperature of 50 to 120° C. and a pressure of 800 to 100 kilopascals.

20. The method of claim 1 , wherein methanol and isobutylene are present in the methyl tertiary butyl ether synthesis unit in a molar ratio of one mole of isobutylene to 1.06 moles to 1.2 moles of methanol.