Method for selective decarboxylation of oxygenates

Abstract

A process plant and a method for producing a hydrocarbon mixture suitable for use as an aviation fuel having an end-boiling point according to ASTM D86 below 300° C. from a decarboxylation feedstock being a feedstock including fatty acid esters and/or triglycerides and including C18 side-chains, to a deoxygenated hydrocarbon mixture by directing the decarboxylation feedstock to contact a material catalytically active in decarboxylation under decarboxylation conditions where the ratio between deoxygenation by formation of carbon oxides and deoxygenation by formation of water is at least 1.5:1, 2:1 or 3:1, as measured by the ratio of C17 paraffins to C18 paraffins in the deoxygenated hydrocarbon mixture, with the associated benefit of such a decarboxylation based method selectively reducing the product carbon length by a single carbon atom, compared to a hydrodeoxygenation based method, which is beneficial for processes requiring a moderate reduction of end boiling point.

Claims

1. A method for producing a hydrocarbon mixture having an end-boiling point according to ASTM D86 below 300° C. and being suitable for use as an aviation fuel from a decarboxylation feedstock comprising fatty acid esters and/or triglycerides and wherein at least 40% of the carbon atoms of the decarboxylation feedstock are contained in C18 side-chains, by converting said decarboxylation feedstock in in the presence of a material catalytically selective towards decarboxylation, such that the ratio between deoxygenation by formation of carbon oxides and deoxygenation by formation of water is at least 1.5:1, as measured by the ratio of C17 paraffins to C18 paraffins in the deoxygenated hydrocarbon mixture.

2. A method according to claim 1 where decarboxylation 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 decarboxylation comprises nickel optionally in combination with other metals, supported on a carrier comprising one or more refractory oxides.

3. A method according to claim 1, wherein at least 60% or 80% of the carbon atoms of said decarboxylation feedstock is contained in C18 side chains.

4. A method according to claim 1, wherein the material catalytically active in decarboxylation comprises more than 5 wt % Ni, and less than 1 wt %, Co, Mo and W.

5. A method according to claim 1, wherein said decarboxylation feedstock is a saturated decarboxylation feedstock, comprising less than 10 wt % olefinic oxygenates.

6. A method according to claim 5, wherein said saturated decarboxylation feedstock is provided as the product of a hydrogenation reaction, receiving a raw oxygenate feedstock comprising at least 10 wt % olefinic oxygenates and selectively hydrogenating olefinic oxygenates under olefin pre-hydrogenation conditions, to provide said saturated decarboxylation feedstock.

7. A method according to claim 6 where pre-hydrogenation conditions involve a temperature in the interval from 150° C. to 280° 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 pre-hydrogenation comprises 5 wt % to 20 wt % molybdenum or tungsten, in combination with 1 wt % to 5 wt % nickel and/or cobalt, supported on a carrier comprising one or more refractory oxides.

8. A method according to claim 1, comprising separating the deoxygenated hydrocarbon mixture according to boiling point, to provide a hydrocracked intermediate aviation fuel having T10 below 205° C. and final boiling point below 300° C. according to ASTM D86.

9. A method 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 decarboxylation is at least 50 ppmv, optionally originating from an added stream comprising one or more sulfur compounds.

10. A method according to claim 1, wherein said decarboxylation feedstock comprises at least 50% wt triglycerides or fatty acids.

11. A method according to claim 1, further comprising a hydrocracking step, under active hydrocracking conditions, where the deoxygenated hydrocarbon mixture or a mixture derived therefrom is directed to contact a material catalytically active in hydrocracking.

12. A method according to claim 11, wherein hydrocracking conditions involve a temperature in the interval 300-450° C., a pressure in the interval 30-150 bar, and a liquid hourly space velocity (LHSV) in the interval 0.5-8 and wherein the material catalytically active in hydrocracking comprises an active metal taken from the group comprising platinum, palladium, nickel, cobalt, tungsten and molybdenum, an acidic support being one or more of an amorphous acidic oxides, and a molecular sieve showing high cracking activity.

13. A method according to claim 1, further comprising an isomerization step, under active isomerization conditions involves a temperature in the interval 250-350° C., a pressure in the interval 30-150 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, a molecular sieve showing high isomerization selectivity.

14. A process plant for production of a hydrocarbon fraction from an decarboxylation feedstock, said process plant comprising a decarboxylation section, a hydrocracking section and a fractionation section, said process plant being configured for directing the decarboxylation feedstock in combination with an amount of a hydrocracked intermediate product to the decarboxylation section to provide a deoxygenated hydrocarbon mixture, separating the deoxygenated hydrocarbon mixture in said fractionation section to provide at least two fractions, including a low boiling product fraction and a high boiling product fraction, directing at least an amount of the high boiling product fraction to the hydrocracking section to provide a hydrocracked intermediate product, directing at least an amount of said hydrocracked intermediate product to the decarboxylation section, wherein said decarboxylation section contains a catalytically active material comprising less than 1 wt %, Co, Mo or W.

Description

[0050] FIG. 1 is a simplified FIGURE showing a process layout for production of aviation fuel. A feedstock rich in oxygenates (100) is directed as a pre-hydrogenation feed stream together with an amount of a hydrogen rich stream (not shown) to a pre-hydrogenation section (PRE) where it contacts a material catalytically active in hydrogenation under olefin hydrogenation conditions, e.g. a sulfided NiMo catalyst supported on alumina typically operating below 250° C. This provides a pre-hydrogenated intermediate product (102). The pre-hydrogenated intermediate product (102) is combined with a hydrocracked bottom fraction (106) and directed as a deoxygenation feed (104) to a deoxygenation section (DO) comprising a material catalytically active in deoxygenation, such as a sulfided Ni catalyst supported on alumina and operating under deoxygenation conditions, providing a deoxygenated hydrocarbon mixture (112). The deoxygenated hydrocarbon mixture (112) is directed to a fractionation section (FRAC) shown for simplicity as a single unit, separating the hydrocracked intermediate product in a light overhead stream (120), a naphtha stream (122), a hydrotreated intermediate kerosene fraction (124) and a bottom fraction (126), as well as water and recycled hydrogen gas (not shown). An amount of the bottom fraction (126) is directed as a recycle stream, which together with hydrogen (not shown) is directed to a hydrocracking section (HDC) comprising a material catalytically active in hydrocracking operating under effective hydrocracking conditions. The hydrotreated intermediate kerosene fraction is directed to an isomerization section.

[0051] To control the temperature in the deoxygenation section, an amount of deoxygenated hydrocarbon mixture (112) may also be cooled, separated in gas and liquid fractions by flashing and the liquid fraction may be directed to be combined with the hydrocracked bottom fraction (106) as recycle, such that the recycled deoxygenated hydrocarbon mixture functions as a heat sink for the heat developed in the exothermal deoxygenation reaction.

[0052] In addition to this specific layout, alternative layouts may also be relevant, including a layout in which no hydrocracking section is included, or a layout where the hydrocracking section (HDC) is positioned between the deoxygenation section (DO) and the fractionation section (FRAC). Also in these layouts a recycle may be used as heat sink.

EXAMPLES

[0053] Two examples are presented to show the effect of the present disclosure.

Example 1

[0054] In a first example, two catalytically active materials compared on similar feedstock, for evaluation of the selectivity with respect to decarboxylation and hydrodeoxygenation.

[0055] Example 1 A involves reaction of a renewable feedstock here denoted Feed A having a fatty acid composition shown in Table 1, reacted in the presence of a catalytically active material (NiMoS), comprising 2.6 wt % Ni and 13 wt % Mo, and Example 1 B involves reaction of a renewable feedstock denoted Feed B, having a fatty acid composition shown in Table 1 reacted in the presence of a catalytically active material (NS), comprising 15 wt % Ni and a small amount, 0.3 wt %, Mo. In both cases the catalytically active material was sulfided, and an amount of dimethyl disulfide was added to the stream of reactants.

[0056] Examples 1A and 1B evaluate the reaction of the feedstock in a single deoxygenation reactor. Reaction conditions are also shown in Table 2, corresponding to the mildest severity ensuring removal of oxygen to below 2000 ppmwt in the feedstock. While the properties of Feed A and Feed B are different, and minor differences exist between the conditions of Experiment 1A and 1B, the similarities between the two experiments are sufficient for considering the results representative for the difference between the two catalytically active materials, which is seen to be that NiS is only 30% selective towards hydrodeoxygenation, whereas NiMoS is 90% selective towards hydrodeoxygenation, while the NiS-based catalytically active material requiring more severe conditions.

TABLE-US-00001 TABLE 1 Unit Feed A Feed B C8:0 Area % GC-AED 0.07 0.00 C10:0 Area % GC-AED 0.04 0.00 C12:0 Area % GC-AED 0.11 0.00 C14:0 Area % GC-AED 0.88 0.08 C14:1 Area % GC-AED 0.13 0.00 C15:0 Area % GC-AED 0.11 0.00 C16:0 Area % GC-AED 16.40 10.92 C16:1 Area % GC-AED 1.45 0.10 C17:1 Area % GC-AED 0.20 0.00 C18:0 Area % GC-AED 6.05 2.92 C18:1 Area % GC-AED 35.56 23.33 C18:2 Area % GC-AED 34.98 52.83 C18:3 Area % GC-AED 1.80 5.86 C20:0 Area % GC-AED 0.37 0.41 C20:1 Area % GC-AED 0.42 0.32 C20:2 Area % GC-AED 0.20 0.00 C21:0 Area % GC-AED 0.15 0.00 C22:0 Area % GC-AED 0.14 0.41 C22:1 Area % GC-AED 0.10 0.00 C23:0 Area % GC-AED 0.06 0.00 C24:0 Area % GC-AED 0.05 0.17 Unknown Area % GC-AED 0.73 2.64 compound

TABLE-US-00002 TABLE 2 Test A B Feed Unit Feed A Feed B Gas/oil ratio Nl/l 952 1500 Pressure barg 64 90 Hydrogen consumption Nl/l 385 283 LHSV PRE h.sup.−1 0.75 WABT PRE ° C. 210 Oxygen removed in PRE % 12 HDO selectivity PRE % 72 HYD of olefins PRE % 95 LHSV DO h.sup.−1 0.505 0.5 WABT DO ° C. 302 330 Oxygen removed in DO % 100 100 HYD of olefins DO % 100 100 HDO selectivity DO % 90 30

Example 2

[0057] Example 2 compares the practical process design using the two types of catalytically active material in a layout corresponding to FIG. 1, but without isomerization, i.e. assuming 124 as the product. For comparison a the process design was also calculated using a third type of catalytically active material, taken from EP1681337B, 5 wt % Pd/C, having a selectivity for decarboxylation of 97%, corresponding to a ratio between decarboxylation and hydrodeoxygenation of 32:1. In this example it was assumed that the feed consisted of C18:2, C18:1, C16:0 with a molar ratio of 3:2:1, corresponding largely to sunflower oil. A detailed overview of the stream composition for the different cases are shown in Table 3-Table 6.

[0058] For simplicity the examples assume a cooled reactor. In practice the temperature in the deoxygenation section (DO) would be limited by cooling an amount of deoxygenated hydrocarbon mixture (112) and combining it with the hydrocracked bottom fraction (106), to provide a heat sink.

[0059] Example 2A (Table 3) and Example 2B (Table 4) demonstrate the performance with a NiS based catalyst, corresponding to Example 1B. Table 3. Example 2A assumes an ideal configuration of the pre-hydrogenation reactor (PRE), with 100% hydrogenation of olefins, but no deoxygenation, whereas Example 2B corresponds to Example 1B, with 12% deoxygenation, with a hydro-deoxygenation selectivity of 72%. Both Example 2A and 2B assume 30% hydro-deoxygenation and 70% decarboxylation in the deoxygenation reactor.

[0060] Example 2C (Table 5) demonstrate the performance with a NiMoS based deoxygenation catalyst similar to that of Example 1A, but with 95% pre-hydrogenation as in Examples 1B and 2B, with 12% deoxygenation, with a hydro-deoxygenation selectivity of 72%. Example 2C assumes 30% hydro-deoxygenation and 70% decarboxylation in the deoxygenation reactor.

[0061] Example 2D (Table 6) demonstrate the performance with a 5 wt % Pd/C based catalyst as reported in EP1681337B, having a selectivity for decarboxylation of 97% and with 95% pre-hydrogenation as in Examples 1B, 2B and 2C, with 12% deoxygenation with a hydro-deoxygenation selectivity of 72%. Example 2D assumes 3% hydro-deoxygenation and 97% decarboxylation in the deoxygenation reactor, and otherwise a performance similar to Example 1B.

[0062] An overview of the performance of Examples 2A-2D is shown in Table 7. It is clearly shown that for a catalyst with high decarboxylation selectivity (2B and 2D) aviation fuel yield is 5.2% or even 7.5% higher than that of example 2C, while the hydrogen consumption is lower.

TABLE-US-00003 TABLE 3 100 102 104 112 126 106 Flow kg/h 100.0 100.0 120.0 120.0 20.0 20.0 Olefins wt % 74.18 0.00 0.00 0.00 0.00 0.00 H.sub.2 wt % 12.09 11.28 9.91 8.71 3.81 3.05 CO, CO.sub.2 wt % 0.00 0.00 0.00 6.00 0.00 0.00 C.sub.1-4 wt % 0.00 0.00 0.00 3.77 0.00 0.00 Naphtha wt % 0.00 0.00 2.72 2.72 0.00 16.29 (C.sub.5-7) Jet yield wt % 0.00 0.00 12.85 57.45 0.00 77.01 (C.sub.8-17) Heavy (C.sub.18) wt % 0.00 0.00 0.00 16.05 96.19 0.00 C5-160° C. wt % 0.00 0.00 6.61 6.61 0.00 39.64 160° C.- wt % 0.00 0.00 8.95 53.55 0.00 53.65 300° C. >300° C. wt % 0.00 0.00 0.00 16.05 96.19 0.00

TABLE-US-00004 TABLE 4 100 102 104 112 126 106 Flow kg/h 100.0 100.0 123.4 123.4 23.4 23.4 Olefins wt % 74.18 3.71 3.01 0.00 0.00 0.00 H.sub.2 wt % 12.09 11.07 9.55 8.49 3.81 3.05 CO, CO.sub.2 wt % 0.00 0.31 0.25 5.42 0.00 0.00 C.sub.1-4 wt % 0.00 74.99 62.47 0.00 0.00 0.00 Naphtha wt % 0.00 0.00 3.09 3.09 0.00 16.29 (C.sub.5-7) Aviation fuel wt % 0.00 3.40 17.36 55.53 0.00 77.01 yield (C.sub.8-17) Heavy (C.sub.18) wt % 0.00 5.55 4.50 18.24 96.19 0.00 C5-160° C. wt % 0.00 0.00 7.52 7.52 0.00 39.64 160° C.- wt % 0.00 3.40 12.93 51.10 0.00 53.65 300° C. >300° C. wt % 0.00 5.55 4.50 18.24 96.19 0.00

TABLE-US-00005 TABLE 5 100 102 104 112 126 106 Flow kg/h 100.0 100.0 158.6 158.6 58.6 58.6 Olefins wt % 74.18 3.71 2.34 0.00 0.00 0.00 H.sub.2 wt % 12.09 11.07 8.10 6.78 3.81 3.05 CO, CO.sub.2 wt % 0.00 0.31 0.19 0.73 0.00 0.00 C.sub.1-4 wt % 0.00 0.54 0.34 2.91 0.00 0.00 Naphtha wt % 0.00 0.00 6.02 6.02 0.00 16.29 (C.sub.5-7) Aviation fuel wt % 0.00 3.40 30.61 40.35 0.00 77.01 yield (C.sub.8-17) Heavy (C.sub.18) wt % 0.00 5.55 3.50 35.56 96.19 0.00 C5-160° C. wt % 0.00 0.00 14.65 14.65 0.00 39.64 160° C.- wt % 0.00 3.40 21.98 31.71 0.00 53.65 300° C. >300° C. wt % 0.00 5.55 3.50 35.56 96.19 0.00

TABLE-US-00006 TABLE 6 100 102 104 112 126 106 Flow kg/h 100.0 100.0 107.5 107.5 7.5 7.5 Olefins wt % 74.18 3.71 3.45 0.00 0.00 0.00 H.sub.2 wt % 12.09 11.07 10.51 9.61 3.81 3.05 CO, CO.sub.2 wt % 0.00 0.31 0.28 8.49 0.00 0.00 C.sub.1-4 wt % 0.00 0.54 0.50 4.22 0.00 0.00 Naphtha wt % 0.00 0.00 1.14 1.14 0.00 16.29 (C.sub.5-7) Aviation fuel wt % 0.00 3.40 8.56 65.61 0.00 77.01 yield (C.sub.8-17) Heavy (C.sub.18) wt % 0.00 5.55 5.16 6.74 96.19 0.00 C5-160° C. wt % 0.00 0.00 2.78 2.78 0.00 39.64 160° C.- wt % 0.00 3.40 6.92 63.98 0.00 53.65 300° C. >300° C. wt % 0.00 5.55 5.16 6.74 96.19 0.00

TABLE-US-00007 TABLE 7 A B C D DCO catalyst NiS NiS NiMOS Pd/C HYD PRE reactor % 100 95 95 95 DO PRE reactor % 0 12 12 12 HDO selectivity % 72 72 72 72 PRE reactor HYD DO reactor % 100 100 100 100 DO DO reactor % 100 100 100 100 HDO selectivity % 30 30 90 3 DCO reactor CO, CO.sub.2 yield wt % 8.2 7.6 1.3 10.4 C.sub.1-4 yield wt % 5.1 5.1 5.3 5.2 Naphtha yield (C.sub.5-7) wt % 3.7 4.3 10.9 1.4 Aviation fuel yield wt % 78.4 78.0 72.8 80.3 (C.sub.8-17) Hydrogen consumption g/kg 27 29 41 23