FI60228C - FOERFARANDE FROSTAELLNING AV JETBRAENSLE - Google Patents

Description

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Ma lBJ (11 'utlAggNINGSSKRIFT CUZZö # 5¾¾ c (4¾ 1 ^ ^ ^ (51) K ».ik.3 / int.ci.3 G 10 G 4-5 / 4-6 FINLAND —FINLAND (21) Patent Application - Patentanaöknlng 2313/72 (22) HekemlapUrl - Ansdknlngidtg 21.00.72 '' (23) Primary Cloud —Giltlghctsdag 21.08.72 (41) Become Public - Bllvlt offentllg 03.03.73

Patent and Registration Office .... , .. , . . . ,,, -. . , (44) Date of entry | -

Patent- and registration- 'Antökan utlagd och utl.skrlftan publicerad 31.08.8l (32) (33) (31) Privilege claimed — Begird prloritet 02.09.71 USA (US) 177439 (71) The Lummus Company, 1515 Broad Street, Bloomfield , New Jersey 07003, USA (72) Morgan Chuan-Yuan Sze, Upper Montclair, New Jersey, USA (7 * 0 Berggren Oy Ab (54) Method of Production of Jet Fuel - Förfarande för framställ-Ning av jetbränsle This invention The invention relates in particular to a process for the use of such hydrocarbons as a feedstock in the production of jet fuel suitable for use in airplanes faster than sound.

In order to be suitable for use in airplanes that are faster than sound, jet fuel must meet requirements that, in some respects, exceed the requirements for jet fuel that are suitable for use in ordinary subsonic airplanes. In particular, jet fuel used in airplanes faster than sound must meet the requirements for a low freezing point and a high Lumino meter. The freezing point of fuel used in such airplanes must be at least as low as -49.5 ° or lower. Compare, for example, the requirements for "S.S.T. proposed fluel A" in Hydrocarbon Processing, April 1971> page 154, Table 2. Luminometer reading is a measure of the combustion properties of a fuel. The higher this figure, the less smoke the fuel generates during takeoff and the lower the amount of radiation generated by the flame. This figure is determined by the method 2 60228 described in A STM designation D1322-51! T. A high luminometer number is associated with a low aroma content and also means a high smoke point.

It has been found that fuels with low luminometer readings burn strongly with a radiant flame and also generate too much smoke during takeoff. Fuels with a relatively high aroma content generally have a relatively low luminometer number. It has also been found that the luminometer number can generally be increased by increasing the paraffin content of the jet fuel. It has further been found, as mentioned in U.S. Patent No. 3,720,769, that the freezing point of jet fuel can be reduced by isomerizing straight-chain paraffins to branched or iso-paraffins.

In addition, it has been found that substances boiling in the boiling range of fuel oil are suitable raw materials for jet fuel. However, these substances alone do not have the low freezing point or high luminometer reading required for fuel used in faster aircraft, even when treated differently. Current specifications generally require that the fuel luminometer be greater than 77 mm. In addition, these fuels must meet other quality requirements, such as high thermal stability, combustion quality and heat content, especially if they are intended to be suitable for faster transport.

Accordingly, it is an object of the present invention to provide jet fuel suitable for use in faster-than-sound aircraft. It is a further object of the invention to produce jet fuel fuels having a freezing point below -50 ° C and a relatively high luminometer number. It is a further object of the invention to produce such jet fuel fuels having a low aromatic content. It is a further object of the invention to produce such jet fuels using petroleum hydrocarbons as the starting material, which generally boil in the boiling range of fuel oil. Other objects and advantages of the invention will become apparent from the following description.

It should be noted, however, that the fuels prepared in accordance with this invention are suitable for use in aircraft other than airborne aircraft. They are generally high-quality jet turbine fuels that meet and exceed the quality requirements for fuels used both below Mach l and faster than sonic jets.

3 60228

The process according to the invention is characterized in that (a) a mixture containing a petroleum fraction boiling substantially in the boiling range of the fuel oil, substantially free of sulfur-containing impurities, and a mixture of branched olefinic hydrocarbons having an average of 9-16 carbon atoms per molecule is subjected to downstream contact through a first reaction zone having an operating temperature of 93-302 ° C and an elevated pressure in contact with the hydrogenation catalyst, (b) removing from the first reaction zone a gas phase effluent consisting of hydrogen and vaporized liquid, and a partially hydrogenated liquid phase; the liquid phase effluent is passed to a second reaction zone having an operating temperature of 122 to 232 ° C and the pressure is elevated, (d) said liquid phase effluent is hydrogenated by introducing a hydrogen-rich gas into the second reaction zone upstream of it; and (e) removing from said second reaction zone a gas phase effluent consisting of hydrogen and vaporized liquids, and a liquid phase effluent which is jet fuel.

The accompanying drawing is a schematic representation of the process of the present invention.

As can be seen from the drawing, the hydrogenation zones are both contained in the same hydrogenation vessel, which is a vertical cylinder with convex ends and pressure-resistant walls. The interior of the vessel is divided into a plurality of chambers, i.e., zones, which are the Upper Reaction Chamber 16, the Central Gas Separation Zone 20, and the Lower Reaction Chamber 18 by horizontal baffles 12, 14, and 24, preferably torn plates or the like. The reaction chambers 16 and 18 are filled with which may be any known hydrogenation-dehydrogenation catalyst such as Raney nickel, or nickel, platinum or palladium, preferably with a support such as alumina, silica, diatomaceous earth, magnesium oxide, zirconia or another inorganic oxide, or other inorganic oxide combinations. In zone 16, the catalyst is supported by the midsole 12. In zone 18, the catalyst is supported by a similar midsole 24. The midsole 24 is preferably some distance above the bottom of the reaction vessel, thus limiting the additional lower chamber, i.e. zone 26, from above.

Fresh aromatic feedstock, which boils substantially in the boiling range of the fuel oil and which will be explained in more detail below, is fed into the system down line 62. A mixture of branched olefins, which is also explained below, 10-50 by volume, preferably 15-40 by volume, is fed to this feed stream via line 60. calculated on the aromatic raw material. The combined raw material to proceed along the lead h6, and is supplied with the hydrogen stream 38. It then passes via line 40 along the direction of the arrow until this agrees with the line 44, where it is added to the separator 34 for future recycling the condensed liquid. The mixture of feedstock, recycle liquid and hydrogen thus obtained then passes via line 42 to the first zone 16 of the hydrogenation vessel, which operates at a temperature of about 168 to about 260 ° C and a pressure of about 28.6 to 107 ° C.

The mixture of feedstock, recycle liquid and hydrogen passes down through the catalyst in zone 16 under adiabatic reaction conditions in which a considerable amount of aromatics are hydrogenated to the corresponding naphthenic compounds and the olefins are also substantially completely hydrogenated to the corresponding isoparaffins. The reaction product leaving zone 16 is a biphasic mixture. Its liquid phase is a mixture of saturated and somewhat unsaturated compounds. Its gas phase is a mixture of hydrogen, inert gaseous impurities and vaporized liquid hydrocarbons having a composition generally similar to that of the liquid phase of the reaction product.

The liquid phase of the effluent flows downwards through the steam separation zone 20 to the second hydrogenation zone 18 (through the intermediate base 14 which acts as a distribution plate).

In the reaction zone 18, the hydrogen fed down line 48 and passing through the chamber 26 comes into countercurrent contact with the liquid phase effluent, completing the hydrogenation of the aromatics. Hydrogen is fed without preheating, at a relatively low temperature compared to the temperature of the liquid phase effluent from zone 16. The temperature of the hydrogen is generally not higher than about 37> 8-48.8 ° C.

The liquid phase leaving the hydrogenation zone 18 remains briefly in the chamber 26 so that the vapors can escape but close the access line 50 to prevent hydrogen escape. The liquid phase is recovered in line 50 and contains a very small amount, usually less than 1 volume, of unhydrogenated aromatics and virtually no olefins. The gas phase effluent from the reaction zone 18 contains excess hydrogen, inert gaseous impurities, and vaporized hydrocarbons similar to the gas phase effluent from the zone 16.

The gas phase effluents from both the first hydrogenation zone 16 and the second hydrogenation zone 18 accumulate in the vapor separation zone 20. The combined gas phase fraction is discharged along line 28 and first passed through a heat exchanger, i.e. waste waste boiler 52, processes, or for general purposes. The vapor phase, which is still hot, is then passed down line 54, preferably through condenser 32, in which system the remaining vaporized liquid phase components condense back into liquids. The resulting two-phase system, consisting of hydrogen gas, inert gases, and rehydrated hydrocarbons, is passed to a separator 34 in which the liquid phase and the gas phase are separated. The liquid phase is led along line M to be mixed with the feed stream of hydrogenation zone 16 as previously described. The gas phase, which consists of hydrogen and inert gases, can be partially released into the atmosphere, for example up to line 56, to prevent the enrichment of inert contaminants in the system.

The remainder and most of this gas phase is recycled along line 36 to be mixed with the first hydrogenation zone 16 feed stream in line 40. Fresh feedwater may be added from line 48 down line 58 to recycle gas if the recycled hydrogen is not sufficient for the first hydrogenation zone.

An important feature of this invention is internal temperature control. Reactions of the type in question are exothermic. Low discharge temperatures promote the production of the desired type of jet fuel. In addition, uncontrolled reactions must be prevented to avoid the formation of coke and unwanted by-products. Thus, processes for hydrogenating aromatics to jet fuel usually require external temperature control devices. In the process according to the invention, instead, an inherent temperature control is obtained, especially in the second hydrogenation zone 18. As the hydrogen supplied from line 48 passes upwards through this zone, part of the heat in this chamber is used to heat the hydrogen. Another portion of the heat is used to evaporate the reaction product liquid in zone 18 to the extent that it is sufficient to saturate the gas stream exiting this zone to the vapor separation zone 20. Similarly, the temperature of the first reaction zone 16 is controlled by the consumption of heat for partial evaporation of the liquid feed stream. The vaporized liquid exits the vapor separation zone 20 down line 28 as described above. A similar process for preparing cyclohexane from benzene using this same internal temperature control is described in U.S. Patent 3,450,784.

The vaporized hydrocarbons recovered from the vapor separation zone 20 and used for recycling are part of the hydrogenated feedstock and contain up to about 5% aromatics. The volume ratio of recycled material to fresh feedstock is generally in the range of 0.25: 1.0-1.5 · Ί.0, and depends on several factors such as the partial pressure and purity of hydrogen, the desired temperature in the reactor, and the like.

The major part of the feedstock fed to this process is a petroleum fraction which generally boils in the boiling range of the fuel oil, namely between about 149 ° C and about 288 ° C. This part of the raw material may be straight-run fuel oil, heavy naphtha, heating oil, catalytically cracked cyclic oil, etc. The process of the invention does not provide for the removal of sulfur compounds in a practical amount, although some may occur; as a result, most of the raw materials have to be desulfurized before the raw material is fed to the process, usually in a separate unit (not shown).

The olefin mixture used in the process of the invention is a medium molecular weight oligomer of propylene or butene isomers, or a mixed oligomer of C8-C4 olefins. Because this oligomer is a polymer of olefins, it is unsaturated in itself and contains 9 to 16 carbon atoms per molecule. Most suitable are C 2 -C 2 C 1-6 olefic compounds, and of these, those with a large number of branched chains are particularly suitable.

In general, these oligomers and mixtures thereof boil between about I38 and about 174 ° C, preferably between 171-260 ° C. Suitable are oligomers such as propylene trimer and tetramer, butene trimer and tetramer, and propylene-butene and ethylene-propylene-butene mixed oligomers, as well as mixtures such as polymer-gasoline. Butigens, or oligomers formed by butenes with ethylenes and / or propylenes, are expected to be particularly suitable because they have the greatest tendency to form branched chains.

If sulfur compounds have been removed from the fuel oil part of the feedstock just before it is fed to the first hydrogenation zone, it is so hot that it does not need to be further heated to bring it to the reaction temperature. Instead, if it is obtained from a simple fractionation process or allowed to cool before being subjected to this process, it must be preheated. In any case, the hydrogen fed to the first hydrogenation zone 16 must be preheated before it is fed to this zone. The liquid recycled to this zone must also be preheated.

The hydrogenation of olefinic oligomers is also an exothermic reaction that takes place easily at a slightly lower temperature than the hydrogenation of a fuel oil feedstock, which generally requires an inlet temperature of at least 177-182 ° C. This saves costs and minimizes the risk of overreaction when the feedstock is fed to the reactor at a lower temperature, generally about 93- to about 177 ° C, preferably 107-163 ° C. The maximum temperature at the exit of the first reaction zone is generally limited to 302 ° C. The exotherm of the hydrogenation of the olefins raises the temperature of the feedstock some of its way through the first reaction zone 16 and thus "triggers" the hydrogenation of the fuel oil feedstock. Thus, if the fuel oil feedstock does not require preheating, the olefin feedstock can be mixed with it without having to preheat the olefins.

If preheating of hydrogen, recycled liquid and feedstock is necessary, it can be performed in many ways and either separately or with the same delivery and in the same equipment. A convenient method in this process is to utilize the heat contained in the vapors removed from the vapor separation zone 20 flowing along lines 28 and 34. Hydrogen (and, if necessary, feedstock), together with recirculation along line 44. In the echo of the barrier, line 42 is passed through heat exchanger 30 where it preheats to the desired feed temperature through indirect heat trap with partially cooled vapors down line 54. In some circumstances, this heat exchange may have the additional effect of partially condensing some of the combined steam from the hydrocarbons, facilitating the separation of the hydrocarbons from the hydrogen and other gases in the separator 34 for recycling.

If the fresh fuel oil feed is already hot enough so that it; does not require preheating, it must be passed past the preheater in the usual way to overheat overheating and adverse side reactions. The fresh fuel oil feed is then fed into the system down line 43 instead of line 46. The olefinic feedstock can be mixed with it due to 41. In this case, only hydrogen and recycled liquid hydrocarbons are preheated.

Alternatively, the preheating of the fresh feedstock, recyclable liquid, and stretch can be performed in separate heat exchangers and the heated materials are then mixed together before being fed to the reactor. This separate preheating can be performed using any available heat source, for example, a hot steam mixture flowing down line 54.

The ratio of hydrogen to fresh feed in the mixture fed to reaction zone 16 can range from a minimum of one mole per stoichiometric sanitary to each double bond, to as much as about three moles per double bond, and results in a ratio of up to 860228 48 of hydrogen entering the reaction zone. VAA>. the liquid substance may range from about 0.3 to about 1.0 moles per mole.

L.H.3.V. is maintained in the first zone 16 preferably between about 0.5 and about 6.0 based on the fresh feed, and in the second zone 18 generally slightly higher.

The temperature conditions in the second zone must be set so that the temperature of the liquid product in the outlet line 50 remains between about 121 and about 232, preferably between about 149 and about 204 ° C to maximize conditions, promote hydrogenation of aromatics to naphthenes, and as close to equilibrium as possible.

To further illustrate the nature of this invention and its mode of application, the following specific example is set forth.

Example

A mixture of 80% straight distillate fuel oil (previously desulfurized and nitrogen compounds) and 20% crude propylene tetramer was treated in the system of the drawing. The characteristics of the raw materials were as follows:

Fire oil y

Boiling point at the beginning 175 ° C

End point 260 ° C

Aromatics, by volume- # 16.5 Freezing point -47 ° 0

Luminometer number, mm 48

Smoke point, mm 21.5

Propylene tetramer

Boiling point at the beginning 181 ° C

End point 204 ° C

Freezing point below -58.5 ° C

The smoke point of the fuel oil and propylene tetramer raw material mixture was 22.3 mm and the luminometer reading was 50 mm.

The reactor was operated using an inlet temperature to zone 16 of 214 ° C, a total pressure of 64 aty and a total of L.L.S.V. of 1.83. The total ratio of hydrogen to fresh feedstock hydrocarbons was 700 S.C.F. per barrel of fresh raw material.

The reaction product contained 1.3 volumes of unsaturated aromatics, had a freezing point of -50 ° C, a smoke point of 34.6 mm and a Lumino meter number of 36 mm.

Claims (15)

960228 The foregoing description is not intended to be exhaustive, as modifications to the invention in accordance with the principles set forth above will no doubt readily occur to those skilled in the art. Accordingly, the invention is not to be construed as limited to what has been described above, but only as limited by the appended claims. A process for preparing jet fuel, characterized in that (a) a mixture comprising petroleum oil boiling substantially in the boiling range of a fuel oil, substantially free of sulfur-containing impurities, and a mixture of branched olefinic hydrocarbons having an average of 9 to 16 carbon atoms per molecule, with a hydrogen-containing gas through a first reaction zone having an operating temperature of 93 to 302 ° C and an elevated pressure in contact with the hydrogenation catalyst; c) said liquid phase effluent is passed to a second reaction zone having an operating temperature between 122-232 ° C and an elevated pressure, (d) said liquid phase effluent is hydrogenated by introducing a hydrogen-rich gas into the second reaction zone corresponding to and in contact with the hydrogenation catalyst, and (e) removing from said second reaction zone a gas phase effluent consisting of hydrogen and vaporized liquids and a liquid phase effluent which is jet fuel. Process according to Claim 1, characterized in that the mixture according to (a) is preheated before it is fed to the first reaction zone. A method according to claim 2, characterized in that the gas phase effluent streams of the first and second reaction zones are combined and indirectly exchanged for heat with the feed stream of the first reaction zone in order to cool said gas phase effluent streams and preheat said feed stream. ^. A process according to claim 1, characterized in that the gas phase effluents of the first and second reaction zones are cooled to such an extent that the vaporized liquid components contained therein condense, and said liquid components are separated from the remaining gas components and returned to the first reaction zone as a liquid feed. A method according to claim 4, characterized in that the majority of said remaining gas components are returned as feed to the first reaction zone. Process according to Claim 4, characterized in that the volume ratio of the recycled liquid to the fresh feedstock is between 0.25: 1.0 and 1.5; A method according to claim 1, characterized in that said petroleum fraction, which boils substantially in the boiling range of the fuel oil, is subjected to the removal of sulfur compounds before it is mixed according to (a). A method according to claim 7, characterized in that said petroleum fraction is a straight-run fuel oil from which sulfur compounds have been removed. A process according to claim 1, characterized in that said petroleum fraction, which boils substantially in the boiling range of the fuel oil, is mixed in step (a) with a mixture of branched olefinic hydrocarbons having an average of 12 to 16 carbon atoms per molecule. Process according to Claim 9, characterized in that the mixture of olefinic hydrocarbons is propylene tetramer. Process according to Claim 1, characterized in that the mixture of olefinic hydrocarbons is an oligomer of butenes. Process according to Claim 1, characterized in that in step (e) a liquid phase effluent with a freezing point of less than -50 ° C is generated. Process according to Claim 1, characterized in that the olefinic hydrocarbons are mixed in a ratio of 10 to 50% by volume. petroleum fraction. Process according to Claim 13, characterized in that the olefinic hydrocarbons are mixed in a ratio of 15 to 40% by volume. petroleum fraction. The process of claim 1, wherein the second hydrogenation zone is operated at a temperature of about 150 to about 205 ° C. 13 60228