METHOD FOR PRODUCTION OF AVIATION FUEL

Abstract

A process plant and a process for production of a hydrocarbon suitable for use as jet fuel from a feedstock being a renewable feedstock or an oxygenate feedstock, including combining the renewable feedstock with an amount of a hydrocracked intermediate product, directing it to contact a material catalytically active in hydrodeoxygenation under hydrodeoxygenation conditions to provide a hydrodeoxygenated intermediate product, fractionating the hydrodeoxygenated intermediate product in at least two fractions including a first fraction of which at least 90% boils below a defined boiling point and a second fraction of which at least 90% boils above the defined boiling point, directing at least an amount of the second fraction to contact a material catalytically active in hydrocracking under hydrocracking conditions to provide the hydrocracked intermediate product, the process being suited for efficiently converting the upper-boiling point of an oxygenate feedstock such as a renewable feedstocks to a lower boiling product.

Claims

1. A process for production of a hydrocarbon fraction suitable for use as jet fuel from an oxygenate feedstock, comprising the steps of a. combining the feedstock with an amount of a hydrocracked intermediate product to form a combined feedstock, directing the combined feedstock to contact a material catalytically active in hydrodeoxygenation (HDO) under hydrodeoxygenation conditions to provide a hydrodeoxygenated intermediate product, b. fractionating said hydrodeoxygenated intermediate product in at least two fractions, including a first fraction of which at least 90% boils below a defined boiling point and a second fraction of which at least 90% boils above said defined boiling point, c. directing at least an amount of said second fraction to contact a material catalytically active in hydrocracking (HDC) under hydrocracking conditions to provide the hydrocracked intermediate product.

2. The process according to claim 1 wherein step b comprises separating the hydrocracked intermediate product according to boiling point, to provide a hydrocracked intermediate jet product having T10 above 205° C. and final boiling point below 310° C. according to ASTM D86.

3. The process according to claim 1, wherein the total volume of hydrogen sulfide relative to the volume of molecular hydrogen in the gas phase of the total stream directed to contact the material catalytically active in hydrodeoxygenation is at least 50 ppm.sub.v, possibly originating from an added stream comprising one or more sulfur compounds.

4. The process according to claim 1, wherein said feedstock comprises at least 50% wt triglycerides or fatty acids.

5. The process according to claim 1, wherein hydrodeoxygenation conditions involve a temperature in the interval 250-400° C., a pressure in the interval 30-150 Bar, and a liquid hourly space velocity (LHSV) in the interval 0.1-2 and wherein the material catalytically active in hydrodeoxygenation comprises molybdenum or possibly tungsten, optionally in combination with nickel and/or cobalt, supported on a carrier comprising one or more refractory oxides.

6. The process according to claim 1, wherein hydrocracking conditions involve a temperature in the interval 250-400° C., a pressure in the interval 30-150 Bar, and a liquid hourly space velocity (LHSV) in the interval 0.5-4, optionally together with intermediate cooling by quenching with cold hydrogen, feed or product and wherein the material catalytically active in hydrocracking comprises (a) one or more active metals taken from the group platinum, palladium, nickel, cobalt, tungsten and molybdenum, (b) an acidic support taken from the group of a molecular sieve showing high cracking activity, and having a topology MFI, BEA and FAU and amorphous acidic oxides and (c) a refractory support.

7. The process according to claim 1, wherein the process conditions are selected such that the conversion, defined as the difference in the amount of material boiling above 310° C. in said hydrocracked intermediate product and the amount of material boiling above 310° C. in said second fraction, relative to the amount of material boiling above 310° C. in said second fraction, is above 20%.

8. The process according to claim 1, wherein at least an amount of said first fraction is directed to contact a material catalytically active in hydrodearomatization (HDA) under hydrodearomatization conditions to provide a hydrodearomatized product comprising less than 1 wt/wt %, calculated by total mass of aromatic molecules relative to all hydrocarbons in the stream.

9. The process according to claim 8, wherein hydrodearomatization conditions involve a temperature in the interval 200-350° C., a pressure in the interval 20-100 Bar, and a liquid hourly space velocity (LHSV) in the interval 0.5-8 and wherein said material catalytically active in hydrodearomatization comprises an active metal taken from the group comprising platinum, palladium, nickel, cobalt, tungsten and molybdenum, and a refractory support.

10. The process according to claim 8 wherein a hydrogen rich stream comprising at least 90 vol/vol % hydrogen is directed to contact the material catalytically active in hydrodearomatization (HDA).

11. The process according to claim 1, wherein at least an amount of said first fraction or said hydrodearomatized product is directed to contact a material catalytically active in isomerization (ISOM) under isomerization conditions.

12. The process according to claim 1, wherein isomerization conditions involves a temperature in the interval 250-350° C., a pressure in the interval 20-100 Bar, and a liquid hourly space velocity (LHSV) in the interval 0.5-8 and wherein the material catalytically active in isomerization comprises an active metal taken from the group comprising platinum, palladium, nickel, cobalt, tungsten and molybdenum, an acidic support and an amorphous refractory support comprising one or more oxides taken from the group comprising alumina, silica and titania.

13. The process according to claim 1, wherein the treated product is directed to a gas/liquid separator (SEP4) to provide a second stage gaseous fraction and a treated intermediate jet product which is directed to a further means of separation (STAB), to provide said hydrocarbon fraction suitable for use as a jet fuel and a treated product off gas.

14. A process plant for production of a hydrocarbon fraction from an oxygenate feedstock, said process plant comprising a hydrodeoxygenation section (HDO), a hydrocracking section (HDC) and a fractionation section (FRAC), said process plant being configured for a. directing the feedstock and an amount of a hydrocracked intermediate product to the hydrodeoxygenation section (HDO) to provide a hydrodeoxygenated intermediate product, b. separating the hydrodeoxygenated intermediate product in said fractionation section (FRAC) to provide at least two fractions, including a low boiling product fraction and a high boiling product fraction, c. directing at least an amount of the high boiling product fraction to the hydrocracking section (HDC) to provide a hydrocracked intermediate product, d. directing at least an amount of said hydrocracked intermediate product said further feedstock.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0057] FIG. 1 shows a process according to the present disclosure.

[0058] FIG. 2 shows a simplified illustration of a process according to the present disclosure.

[0059] FIG. 3 shows a simplified illustration of a process according to the prior art.

DETAILED DESCRIPTION

[0060] FIG. 1 shows a process layout for production of a hydrocarbon suitable for use as jet fuel (98) from a renewable feedstock (2), wherein the renewable feedstock (2) is combined with a hydrocracked intermediate product (14) and directed as a hydrodeoxygenation feed stream (6) together with an amount of a hydrogen rich stream (12) to a hydrodeoxygenation section (HDO) where it contacts a material catalytically active in hydrodeoxygenation under hydrodeoxygenation conditions. This provides a hydrodeoxygenated intermediate product (22). The hydrodeoxygenated intermediate product (22) is directed to a gas/liquid separator (SEP1) where it is separated into a gaseous fraction (26) and a liquid hydrocracked intermediate product (34). The gaseous fraction (26) is split in an optional purge (28) and a recycle gas (30) which is pressurized in a compressor (CM1) and directed as hydrogen supply (12) to the hydrodeoxygenation section (HDO) and a hydrocracking section (HDC). The liquid hydrocracked intermediate product (34) is directed to a stripper (STR), which also receives a stripping medium (38) and optionally a stripper overhead recycle (40). From the stripper a gaseous stripper product (42) is directed to a gas/liquid separator (SEP2), from which an vapor phase product (46) and a light naphtha fraction (48) are withdrawn. An amount of the light naphtha is withdrawn as product (50), an amount (52) may optionally be directed as feed (90) to a kerosene stabilizer (STAB) and an amount is directed as overhead recycle (40) to the stripper (STR). The liquid stripper product (54) is directed to fractionator (FRAC), from which a light overhead stream (58) is directed to an overhead vessel (OV), from which a heavy naphtha (62) is withdrawn. An amount of heavy naphtha (64) is withdrawn as product and a further amount (66) is directed as fractionator recycle (66). A high boiling product fraction (68) is split in to a recycle stream (72) and a reboiled stream (74). The recycle stream (72) is combined with a gaseous fraction (78) and directed as a hydrocracker feed stream (4) to a hydrocracking section (HDC) operating under hydrocracking conditions. From a side column (SC) a hydrodeoxygenated intermediate jet product (80) is withdrawn and combined with a of hydrogen rich stream (84) and directed as feed (82) to a post treat section (PT), where it contacts a material catalytically active in isomerization (ISOM) under isomerization conditions and a material catalytically active in hydrodearomatization (HDA) under hydrodearomatization conditions, optionally receiving further hydrogen, providing a treated product (86), which is directed to a product gas/liquid separator (SEP4) from which a second gaseous fraction (78) is withdrawn and combined with the recycle stream (72) and provided as make-up hydrogen in a feedstream to a hydrocracking section (HDC). An intermediate jet product (88) is withdrawn from the product gas/liquid separator (SEP4), and directed to a further means of separation (STAB), such as a kerosene stabilizer, from which a liquid product (94) is withdrawn and split in a hydrocarbon fraction suitable for use as jet fuel (98) and a reboiler liquid (96). The gaseous overhead from the kerosene stabilizer (92) is combined with the gaseous stripper product (42) and directed to a gas/liquid separator (SEP2).

[0061] In a further embodiment (not shown) the second gaseous fraction (78) is not directed as make-up gas for the hydrodeoxygenation section, but instead directed to the posttreatment section (PT), requiring an additional compressor, but also resulting in added simplicity. In this case make-up hydrogen is then added separately to the hydrodeoxygenation section.

[0062] In a further embodiment the gaseous overhead from the kerosene stabilizer (92) may be handled in a separate overhead circuit with the benefit of simplicity and independence, but at the cost of extra equipment items for cooling, separation and reflux pumps.

[0063] In a further embodiment the separator, fractionation and light ends recovery sections can be configured in multiple ways as it is known to the skilled person. If light materials like LPG or propane are valuable, the recovery of these can be improved by using a sponge oil absorption system e.g. using the heavy naphtha from the fractionator overhead as lean oil and returning the rich oil to the stripper.

[0064] FIG. 2 is a simplified figure showing a layout similar to that of FIG. 1, omitting supply of gaseous streams and details of separation for simplicity. A renewable feedstock (202) is combined with a hydrocracked intermediate product (206) and directed as a hydrodeoxygenation feed stream (204) together with an amount of a hydrogen rich stream (not shown) to a hydrodeoxygenation section (HDO) where it contacts a material catalytically active in hydrodeoxygenation under hydrodeoxygenation conditions. This provides a hydrodeoxygenated intermediate product (212). The hydrodeoxygenated intermediate product (212) is directed to a fractionation section (FRAC) shown for simplicity as a single unit, separating the hydrodeoxygenated intermediate product in a light overhead stream (220), a naphtha stream (222), a hydrodeoxygenated intermediate jet product (224) and a high boiling product fraction (226). The high boiling product fraction (226) is directed as a recycle stream to a hydrocracking section (HDC) operating under hydrocracking conditions, providing a hydrocracked intermediate product (206), which, as mentioned, is combined with the renewable feedstock (202). The hydrodeoxygenated intermediate jet product (224) is directed as feed to a post treat section (PT), where it contacts a material catalytically active in isomerization (ISOM) and a material catalytically active in hydrodearomatization (HDA) under hydrodearomatization conditions, providing a treated jet fuel product (218).

[0065] FIG. 3 shows an example of the prior art, in a level of detail similar to FIG. 2, omitting supply of gaseous streams and details of separation for simplicity. A renewable feedstock (302) is combined with a recycle diluent stream (310) and directed as a hydrodeoxygenation feed stream (304) together with an amount of a hydrogen rich stream (not shown) to a hydrodeoxygenation section (HDO) where it contacts a material catalytically active in hydrodeoxygenation under hydrodeoxygenation conditions. This provides a hydrodeoxygenated intermediate product (306), from which gases are separated e.g. in a stripper (SEP), providing a sweet hydrodeoxygenated intermediate product (308), which is split into said recycle diluent stream (310) and an isomerization feed (312) which is directed to a hydroisomerization section (ISOM) where it contacts a material catalytically active in isomerization under isomerization conditions, providing a dewaxed intermediate product (314). The dewaxed intermediate product (314) is directed to a hydrocracking section (HDC) where it contacts a material catalytically active in hydrocracking under hydrocracking conditions, providing a hydrocracked product (316). The hydrocracked product (316) is directed to a fractionation section (FRAC) shown for simplicity as a single unit, separating the hydrocracked product in a light overhead stream (320), a naphtha stream (322), a jet product (324) and a bottom diesel fraction (326).

EXAMPLES

[0066] The performance of the process layouts shown in FIGS. 2 and 3 have been compared, based on two similar feedstocks, and process conditions optimized for maximum jet yield.

[0067] Table 1 shows the characteristics of a renewable feedstock which is a mixture of 50% used cooking oil and 50% animal fat. The feedstock comprises 6% aromatics and 80% boils above 500° C.; mainly due to the presence of high boiling triglycerides.

[0068] Feedstock A was treated in a process in accordance with FIGS. 2 and 3, and the results of this treatment is shown in Table 2.

[0069] In the hydrotreatment a significant conversion of boiling point is seen due to triglycerides being converted to alkanes. In addition, an amount of conversion is observed in the hydrocracking reactor and the isomerization reactor. The true conversion per pass is however quite low, since the amount of recycle is high.

[0070] The results of both examples show a production of a jet fuel with excellent properties, a low freezing point (−40° C.) and a low aromatics content (<0.5 wt %). The example according to the present disclosure (FIG. 2) has a jet yield of 67 wt/wt %, whereas the Example according to the prior art (FIG. 3) has a jet yield of 58 wt/wt %, whereas 11 wt/wt % diesel is produced. In addition, naphtha is produced in both scenarios. In a process designed for production of jet, the yield difference of 9% is of course valuable.

[0071] The configuration of FIG. 2, where the product of hydrodeoxygenation is split in a light and a heavy fraction and the heavy fraction is recycled to a hydrocracking reactor upstream the hydrodeoxygenation, results in a full conversion of heavy feedstock to jet product, while avoiding directing light hydrocarbons to the hydrocracking section, and thus a higher yield of jet product compared to the configuration of FIG. 3.

TABLE-US-00001 TABLE 1 SG 0.9209 Aromatics in feed, 6 wt/wt % distillation: SimDist, wt/wt % IBP 340  5% 365 10% 398 20% 533 30% 582 40% 597 50% 601 60% 602 70% 608 80% 610 90% 611 95% 612 FBP 695

TABLE-US-00002 TABLE 2 Example FIG. 2 FIG. 3 P 70barg 70 barg T(HDO) 320 320° C. T(HDC) 350 310 T(DWX) 330 320 LHSV (DWX)  2  2 LHSV HDC  1  1 Freezing pt Jet −40° C. −40° C. Aromatics content in jet boiling range <0.5 wt/wt % <0.5 wt/wt % Naphtha boiling range yield  12  11 (bp.30-110° C.), wt/wt % Jet boiling range yield (bp.110-310° C.),  67  61 wt/wt % Heavier than jet yield (bp.310-370° C.), —  8 wt/wt %