Methods of deoxygenation of tall oil and production of polymerizable monomers therefrom

Abstract

A method of deoxygenation of tall oil as well as methods for the production of aliphatic hydrocarbons and polymerizable monomers from tall oil. Sulphurous crude tall oil together with hydrogen gas is fed into a reactor comprising a catalyst bed. The oil is catalytically deoxygenated by hydrogen in the bed by use of a sulfided metal catalyst, e.g. a NiMoS catalyst. The flow exiting the reactor is cooled down and a hydrocarbon-bearing liquid phase is separated from a gas phase, followed by subjecting the liquid phase to distillation for removal of useless aromatic hydrocarbons and then to steam cracking to form a product containing olefins such as ethylene or propylene. By regulation of the deoxygenation temperature to be at least 270 C. but less than 360 C. the yield is rich in linear and cyclic aliphates that usefully turn to olefins in the steam cracking, while formation of napthalenes is reduced.

Claims

1. A method for the production of polymerizable olefins from tall oil, the method comprising the steps of: feeding sulphurous crude tall oil and hydrogen gas into a catalyst bed, the sulphurous crude tall oil having a content of 30 to 70 weight-% of fatty acids and a content of 20 to 50 weight-% of resin acids; catalytically deoxygenating the sulphurous crude tall oil by hydrogen in the catalyst bed in a temperature of 280 C. to 320 C. in the presence of a sulfided metal catalyst; cooling the flow which has exited the catalyst bed, and separating a hydrocarbon bearing-liquid phase from a gas phase; removing aromatic hydrocarbons from the hydrocarbon-bearing liquid phase to produce a hydrocarbon-bearing liquid distillate; and subjecting the hydrocarbon-bearing liquid distillate to steam cracking to form a product containing polymerizable olefins.

2. The method of claim 1, wherein water is separated from the hydrocarbon-bearing liquid phase before feeding the liquid into steam cracking.

3. The method of claim 1, wherein the aromatic hydrocarbons are removed from the hydrocarbon-bearing liquid phase before the steam cracking step by distilling the hydrocarbon-bearing liquid phase to separate the aromatic hydrocarbons from the hydrocarbon-bearing distillate.

4. The method of claim 1 wherein ethylene and/or propylene are produced by the steam cracking.

5. The method of claim 1, wherein the gas phase comprises contaminants, hydrogen gas, and C.sub.1 to C.sub.4 hydrocarbons, and wherein the gas phase is washed with diethyl amine to remove the contaminants, the hydrogen gas is circulated to the deoxygenation stage to be used as hydrogen-bearing gas, and the C.sub.1 to C.sub.4 hydrocarbons are recovered and passed to steam cracking.

6. The method of claim 1, wherein the sulphurous crude tall oil contains 0.05 to 0.5 weight-% of sulphur.

7. The method of claim 1, wherein the deoxygenation catalyst is a sulfided NiMo or CoMo catalyst.

8. The method of claim 1, wherein the hydrogen pressure at the deoxygenation step is 30 to 100 bar.

9. The method of claim 1, wherein the catalyst bed is a fixed bed formed by fixed bed material.

10. The method of claim 1, wherein the flows in the catalyst bed run from top to bottom.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) FIG. 1 is a schematic of an apparatus according to certain aspects of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(2) At first, the present invention is described with reference to the appended drawing (FIG. 1), which shows schematically an apparatus intended for the application of the invention.

(3) According to FIG. 1, the process generally comprises treatment of sulphurous crude tall oil 5 in a vertical reactor 1 having catalytic deoxygenating and cracking zones 2, 3 in said order. The output from the reactor 1 is separated into fractions, and the obtained linear and cyclic aliphates in particular are further cracked in a steam cracking apparatus 4, as such known from the field of petrochemistry and operated in a manner known to a skilled person. The products of the steam cracking are olefins, such as ethylene or propylene, which are useful as monomers for the production of biopolymers.

(4) The feed 5 of the crude tall oil, containing 30-70 weight-% of fatty acids and 20-50 weight-% of resin acids, as well as about 5 weight-% of sterols and/or stanols, 0.05-0.5 weight-% of sulphur etc. as minor components, is brought to an upper end of the reactor 1. In addition, hydrogen is fed to the upper end of the reactor 1 through a line 6. The reactor 1 is filled with quartz wool, which works as bed material 7 and the superimposed, separate zones 2, 3 of which comprise a NiMoS catalyst to deoxygenate the acids that were fed and a zeolite catalyst to crack carbon chains. The flow direction of the liquid and gas phases in the reactor 1 is from top to bottom. To adjust the reaction temperatures, the reactor 1 is provided with an electric heater 8.

(5) The hot reaction products exiting through the lower end of the reactor 1 are conducted to a cooler 9, and the liquefied product moves through a line 10 to a separating tank 11, which separates the aqueous phase 12 from the oil phase 13. The oil phase 13 proceeds to a distillator 14, which separates saturated aliphatic as well as cyclic hydrocarbons as distillate 15 from a residue 16 of aromatic hydrocarbons and esters, which is discarded from the process. The residue 16 would not produce useful monomers in steam cracking, and removing the aromatics by distillation prevents them from fouling and eventually clogging the steam cracker 4. The distillate 15 then proceeds to steam cracking 4, wherein cracking into low-molecular olefins 17 as the desired end product takes place through several intermediary stages. The olefins are used as starting materials of the production of biopolymers, such as polyethylene or polypropylene.

(6) The gases 18, which are not condensed in the cooler 9 and which contain hydrogen, oxides of carbon, possibly low-molecular hydrocarbons and other impurities, moves to a washer 19, treating the gas flow with diethyl amine. Pure hydrogen 20 is circulated back to the upper end of the reactor 1 to constitute part of the deoxygenating gas, a flow 21 of lower alkanes and water vapour are conducted to the steam cracker 4, and the oxides of carbon and other gaseous impurities 22 are removed from the process.

(7) In a simpler implementation of the process according to the invention the zeolite catalyst 3 in the reactor 1 and, along with that, the catalytic cracking may be omitted. In that case, circulating 20 the hydrogen can also be omitted due to the minor amount or lack of hydrogen exiting the reactor. In other respects, the apparatus and the process flow are as illustrated in the drawing.

EXAMPLE

(8) A series of eleven tests (1-11) was carried out by use of a sample of crude tall oil (CTO). Tests 1-5 were comparative and tests 6-11 accorded with the invention.

(9) The sulphurous CTO stemmed from sulphate cooking process. Water was not added to the CTO before it was fed to deoxygenation. The reactor corresponded to the one described in FIG. 1. Hydrogen was used as the deoxygenating gas. The deoxygenation catalyst was NiMo presulfided with H.sub.2S and H.sub.2 at 320 C. or a temperature gradually rising from 20 to 400 C. The deoxygenation temperature in the tests was in the range of 300-406 C., and the gas pressure was in the range of 50-56 bar. The liquid and gas products obtained from the catalytic deoxygenation were analysed. The results are shown in Table 1.

(10) The most important finding from the results is that the share of aromatic hydrocarbons in the liquid product of deoxygenation is significantly reduced as the deoxygenation temperature was dropped from around 400 C. to 300-350 C. The change was accompanied by a rise in the share of useful paraffinic (aliphatic) and naphthenic (cyclic) hydrocarbons. As the yield is turned to polymerizable olefins by steam cracking, the final yield of olefins will be increased accordingly.

(11) TABLE-US-00001 TABLE 1 Sample 1 2 3 4 5 6 7 8 9 10 11 Feedstock CTO g/h 6.1 5.8 6.2 5.7 6.0 6.0 6.0 6.0 6.0 6.0 6.0 Catalyst NiMo g 3 3 3 3.1 3.1 6 6 6 8 8 8 g Presulfiding H2S + H2 CTO H2S + H2 H2S + H2 320 C. 20-400 C. 320 C. 320 C. Reaction Time on stream h 2-4 4-6 6-8 4-6 6-8 2-4 4-6 6-8 2-4 4-6 6-8 Temperature C. 406 402 402 400 401 350 350 350 300 300 300 Pressure bar 52 54 54 56 55 50 50 50 50 50 50 WHSV based on HDO- 1/h 2 1.9 2 1.9 1.9 1.4 0.9 1.2 0.75 0.75 0.75 catalyst & CTO Hydrogen feed g/h 0.67 0.67 0.67 0.67 0.67 0.73 0.73 0.73 0.73 0.73 0.73 Hydrogen/CTO feed w/w 0.11 0.12 0.11 0.12 0.11 0.08 0.17 0.06 0.11 0.116 0.128 Liquid product Approximate yield, % 99 93 81 102 91 90 101 83 99 93 96 from liquid feed Aqueous phase, % of 7 11 12 7 7 10 12 14 4 13 16 total liquid product Composition, wt-% of GC-analyzed Paraffinic 37.6 50.5 42.3 38.5 35.8 53.6 49.3 55.1 59.2 59.9 58.3 Iso-paraffinic 11.6 5.4 7.8 12.9 11.6 5.4 5.1 5.1 2.5 2.8 1.9 Olefins 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Naphtenic (cyclic) 20.9 19.2 22.0 25.3 26.6 25.1 23.3 21.6 22.6 20.3 21.0 Monoaromatics 5.6 3.5 4.8 3.3 3.5 1.6 1.6 1.4 0.9 0.3 0.3 Polyaromatics 18.1 12.0 20.2 13.7 14.3 7.7 9.6 6.2 5.1 7.0 7.0 Esters 6.4 9.2 7.7 6.3 8.2 6.6 11.0 10.5 9.7 9.7 9.7 Gas product Approximate yield, % 8.8 9.1 8.6 7.6 7.3 7.7 9.4 6.9 5.3 6.5 6.5 of liquid feed Composition, % of gaseous products: average over average over 8 hours 8 hours CO 15 18 13.9 12.1 15.0 11.5 12.6 13.4 CO2 41 42 62.4 52.4 62.1 67.7 68.5 68.7 C1 + C2 1 17 11.1 15.5 10.5 15.5 14.0 14.3 C3 29 23 12.6 19.7 12.1 4.9 4.4 3.4