Methods of refining natural oil feedstocks
Methods are provided for refining natural oil feedstocks. The methods comprise reacting the feedstock in the presence of a metathesis catalyst under conditions sufficient to form a metathesized product comprising olefins and esters. In certain embodiments, the methods further comprise separating the olefins from the esters in the metathesized product. In certain embodiments, the methods further comprise hydrogenating the olefins under conditions sufficient to form a fuel composition. In certain embodiments, the methods further comprise transesterifying the esters in the presence of an alcohol to form a transesterified product.
1. A method of producing a fuel composition comprising:
providing (a) a feedstock comprising natural oil glycerides, and (b) low-molecular-weight olefins, wherein the low-molecular-weight olefins comprise olefins selected from the group consisting of propylene, 1-butene, 2-butene, and combinations thereof;
reacting the natural oil glycerides with the low-molecular-weight olefins in the presence of a metathesis catalyst to form a metathesized product comprising new olefins and esters;
flash-separating a light end stream from the metathesized product to separate and remove the light end stream from the metathesized product, the light end stream comprising a majority of hydrocarbons with carbon number between 2 and 4;
separating at least a portion of the new olefins in the metathesized product from the esters in the metathesized product to produce separated olefins;
separating a C18+ heavy end stream from the separated olefins, the heavy end stream having a majority of hydrocarbons with carbon numbers of at least 18; and
hydrogenating the separated olefins to form a fuel composition.
2. The method of claim 1 , wherein the fuel composition is: (a) a kerosene-type jet fuel having a carbon number distribution between 8 and 16, a flash point between 38° C. and 66° C., an auto ignition temperature of 210° C., and a freeze point between −47° C. and −40° C.; (b) a naphtha-type jet fuel having a carbon number distribution between 5 and 15, a flash point between −23° C. and 0° C., an auto ignition temperature of 250° C.; and a freeze point of −65° C.; or (c) a diesel fuel having a carbon number distribution between 8 and 25, a specific gravity of between 0.82 and 1.08 at 15.6° C., a cetane number of greater than 40; and a distillation range between 180° C. and 340° C.
3. The method of claim 1 , further comprising separating another light end stream from the separated olefins prior to hydrogenating the separated olefins, the another light end stream having a majority of hydrocarbons with carbon numbers between 3 and 8.
4. The method of claim 1 , further comprising separating a C18+ heavy end stream from the fuel composition to produce another heavy end stream, wherein the another heavy end stream having a majority of hydrocarbons with carbon numbers of at least 18.
5. The method of claim 1 , further comprising isomerizing the fuel composition, wherein a fraction of normal-paraffin compounds in the fuel composition are isomerized into iso-paraffin compounds.
6. The method of claim 1 , wherein the low-molecular-weight olefins comprise olefins selected from the group consisting of: 1-butene, 2-butene, and combinations thereof.
7. The method of claim 1 , wherein the low-molecular-weight olefins comprise olefins comprise 1-butene.
8. The method of claim 1 , wherein the flash-separation produces a bottom stream comprising a majority of hydrocarbons with carbon number between 3 and 5, wherein the bottom stream is recycled to the reaction step.
9. The method of claim 1 , further comprising introducing the metathesized product to an absorber prior to separating the metathesized product, wherein the absorber separates the metathesized product from the metathesis catalyst.