Deoxygenation of fatty acids for preparation of hydrocarbons
Embodiments of methods for making renewable diesel by deoxygenating (decarboxylating/decarbonylating/dehydrating) fatty acids to produce hydrocarbons are disclosed. Fatty acids are exposed to a catalyst selected from a) Pt and MO 3 on ZrO 2 (M is W, Mo, or a combination thereof), or b) Pt/Ge or Pt/Sn on carbon, and the catalyst decarboxylates at least 10% of the fatty acids. In particular embodiments, the catalyst consists essentially of 0.7 wt % Pt and 12 wt % WO 3 , relative to a mass of catalyst, or the catalyst consists essentially of a) 5 wt % Pt and b) 0.5 wt % Ge or 0.5 wt % Sn, relative to a mass of catalyst. Deoxygenation is performed without added hydrogen and at less than 100 psi. Disclosed embodiments of the catalysts deoxygenate at least 10% of fatty acids in a fatty acid feed, and remain capable of deoxygenating fatty acids for at least 200 minutes to more than 350 hours.
1. A method, comprising:
providing a catalyst comprising platinum that is combined with a non-transition metal to facilitate dehydrogenation;
exposing a composition comprising fatty acids to the catalyst; and
dehydrogenating at least 10% of the fatty acids with the catalyst to produce a product comprising branched, cyclic, and/or aromatic compounds.
2. The method of claim 1 wherein at least a portion of the fatty acids are unsaturated fatty acids, and dehydrogenating further comprises transfer hydrogenation.
3. The method of claim 1 wherein the catalyst deoxygenates at least 10% of the product.
4. The method of claim 3 wherein the product further comprises deoxygenated hydrocarbons, and at least a portion of the deoxygenated hydrocarbons are cyclic and/or aromatic.
5. The method of claim 1 wherein the non-transition metal is Ge, Sn, or a combination thereof.
6. The method of claim 1 wherein the catalyst further comprises Pt/Ge on carbon, Pt/Sn on carbon, or a combination thereof.
7. The method of claim 6 wherein the catalyst further comprises 1 wt % to 5 wt % Pt, and 0.1 wt % to 5 wt % Ge, Sn, or a combination of Ge and Sn, relative to a mass of the catalyst.
8. The method of claim 1 wherein exposing the composition to the catalyst is performed in a hydrogen-deficient atmosphere.
9. The method of claim 8 wherein the catalyst is disposed in a column, the method further comprising flowing the composition and a non-hydrogen gas through the column.
10. The method of claim 9 wherein the non-hydrogen gas comprises nitrogen, argon, 1%-100% oxygen, air, or a combination thereof.
11. The method of claim 1 wherein the method is performed in the presence of a hydrogen scavenger.
12. The method of claim 11 wherein the hydrogen scavenger is oxygen.
13. The method of claim 1 wherein the product comprises alkyl-substituted aromatic compounds.
14. The method of claim 1 wherein the product comprises alkylated benzenes.
15. The method of claim 1 wherein the product is suitable for use as an aviation fuel.
16. The method of claim 1 wherein the fatty acids are obtained from a plant oil, a plant fat, an animal fat, or any combination thereof.
17. The method of claim 1 wherein the fatty acids comprise oleic acid, linoleic acid, or a combination thereof.
18. The method of claim 1 wherein the fatty acids in the composition are free fatty acids, fatty acid esters, fatty acid monoglycerides, fatty acid diglycerides, fatty acid triglycerides, or any combination thereof.
19. The method of claim 1 , wherein the composition comprises free fatty acids, the method further comprising:
providing a source of triglycerides;
hydrolyzing the triglycerides to produce free fatty acids and glycerol;
exposing the free fatty acids to the catalyst; and
dehydrogenating at least 10% of the fatty acids with the catalyst to produce the product comprising branched, cyclic, and/or aromatic compounds.
20. A method, comprising:
providing a catalyst comprising platinum combined with Ge, Sn, or a combination thereof, wherein the catalyst is disposed in a column;
flowing a composition comprising fatty acids and a non-hydrogen gas through the column; and
dehydrogenating at least 10% of the fatty acids with the catalyst to produce a product comprising branched, cyclic, and/or aromatic compounds.