DE102021131890A1 - Process for the production of synthetic jet fuel or fuel additive - Google Patents

Abstract

The present invention relates to a process for the production of synthetic aircraft turbine fuel or fuel additive comprising the conversion of liquid and/or gaseous hydrocarbons into a product mixture containing acetylene and at least one other unsaturated product mixture component which has 2 to 5 carbon atoms, and the conversion of thereby obtained acetylene and/or the at least one other unsaturated product mixture component to jet turbine fuel or fuel additive.

Description

field of invention

The present invention relates to a process for the production of synthetic aircraft turbine fuel or fuel additive comprising the conversion of liquid and/or gaseous hydrocarbons into a product mixture containing acetylene and at least one other unsaturated product mixture component which has 2 to 5 carbon atoms, and the conversion of thereby obtained acetylene and/or the at least one other unsaturated product mixture component to jet turbine fuel or fuel additive.

Technical background and state of the art

The global consumption of jet fuel before the COVID-19 pandemic was enormous, amounting to about 340 billion liters per year. It can be expected that this level will be reached again in the long term and with increasing control over the pandemic situation. In view of limited petroleum reserves, intensive research must be carried out into ways of producing synthetic fuels and fuel additives in order to ensure long-term availability.

With a view to the internationally agreed climate targets, it is also necessary to minimize the ecological impact of air traffic and to produce jet fuel sustainably or based on renewable raw materials. This is particularly true because, unlike e.g. road mobility, pure electrification of air traffic only appears possible in very few cases in the foreseeable future. Not least because of this, air traffic is one of the so-called "hard to abate" sectors.

Various manufacturing processes have already been proposed in the past for the production of sustainable synthetic jet fuels and fuel additives. Each manufacturing process results in a product with an individual composition and can potentially have an adverse effect on aircraft components, such as the function and service life of the engine. Therefore, it is common for every new product to go through an approval process.

According to ASTM International, seven processes for the production of sustainable fuels are currently approved (see additions to the ASTM D7566 standard).

One of the processes that has already been certified is the so-called “Alcohol-to-Jet” (AtJ) process, which is promising for commercial use. The process, which can be implemented on an industrial scale, starts with bioethanol as the alcohol, for example. The bioethanol can, for example, be obtained from organic material in various biochemical and/or thermochemical ways. In the production process, bioethanol is dehydrated in a first step, with ethylene being obtained as an intermediate product. This can be converted by oligomerization and at least partial hydrogenation to a mixture of hydrocarbons containing a fraction suitable as jet fuel. Another "alcohol-to-jet" process variant certified according to ASTM D7566, which can probably also be implemented on an industrial scale, is based on isobutanol, which can also be obtained biochemically by fermentation with yeast. An advantage of the AtJ routes is the comparatively high yield of jet fuel or fuel additive (cf. IEA Bioenergy, "Progress in Commercialization of Biojet/Sustainable Aviation Fuels (SAF): Technologies potential and challenges", IEA Bioenergy Task 39, May 2021).

Nevertheless, the raw material base for the production of bioethanol and biochemically produced isobutanol is limited, which is why there is a need for further or supplementary solutions for the sustainable production of jet fuel.

Other routes for producing sustainable jet fuels include the HEFA process or processes based on Fischer-Tropsch synthesis. These routes also have considerable potential to reduce the CO ₂ emissions associated with air traffic, provided sustainable raw materials and energies are used, eg the Fischer-Tropsch synthesis uses synthesis gas from sustainable sources such as the gasification of sustainable biomass. However, the amount of sustainable raw materials available for the HEFA process, eg waste oils such as used cooking oil, is also limited. Although the amount of sustainable raw materials available for the Fischer-Tropsch synthesis is larger, the disadvantage is that the proportion of by-products that are not suitable as jet fuel is usually particularly large.

Experts have already recognized this disadvantage in the HEFA process and processes based on the Fischer-Tropsch synthesis, but have not yet solved it in the best possible way. Starck et al. (Starck L, Pidol L, Jeuland N, Chapus T, Bogers P, Bauldreay J, "Production of Hydroprocessed Esters and Fatty Acids (HEFA) - Optimization of Process Yield", Rev. IFP Energies Nouvelles, 71 (10), 2016) complain, for example, about the low yield of flight doors Binary fuel in the HEFA process. They see one of the causes of the yield loss in the isomerization reaction, which is required for improved flow behavior at low temperatures. According to the analysis by Starck et al. the isomerization is accompanied by undesired degradation reactions which lead to the formation of low-boiling hydrocarbons which are unsuitable as jet fuel. For this reason, they propose to apply milder conditions in the isomerization step. From the authors' point of view, the usefulness of HEFA produced in this way as an aircraft turbine fuel additive is not significantly affected by this. They show that the mixture of HEFA with conventional jet fuel meets all essential specifications.

This concept may be helpful when using HEFA as an additive to conventional jet fuel, but it is not compatible with the long-term goal of switching air traffic to fully-fledged, purely sustainably produced jet fuel.

In addition, the formation of low-boiling hydrocarbons cannot be completely prevented, even under milder isomerization conditions, and the question remains as to how the low-boiling fraction can be put to ecologically sensible use.

object of the invention

Against this background, it was an object of the present invention to overcome the disadvantages of the prior art and to provide an improved process for the production of synthetic aircraft turbine fuel or fuel additive. In particular, a process should be specified that allows the production of synthetic jet fuel or fuel additive with a high yield, starting mainly from low-boiling hydrocarbons that cannot be used directly as jet fuel, and only producing small amounts of low-boiling hydrocarbons. It was also intended to increase the volume potential for the sustainable production of jet fuel or fuel additive without additional consumption of sustainable, e.g. biogenic raw materials and/or energies.

Summary of the Invention

This object is achieved by the method having the features in claim 1. Further advantageous variants of the method can be found in the dependent claims.

The process according to the invention for the production of synthetic aircraft turbine fuel or fuel additive comprises the following steps: a) converting liquid and/or gaseous hydrocarbons into a product mixture containing acetylene and at least one other unsaturated product mixture component which has 2 to 5 carbon atoms, b) converting the acetylene obtained in step a) and/or the at least one other unsaturated product mixture component to jet turbine fuel or fuel additive.

An advantage of the process according to the invention is that in step a) acetylene and another unsaturated product mixture component which has 2 to 5 carbon atoms is obtained. Both acetylene and the other unsaturated product mixture components are intermediates that can be used in many ways, since they have high reactivities due to their multiple bonds and can therefore be easily converted into materials. They can therefore be used not only for the production of jet fuel or fuel additives, but also for the production of a whole range of chemicals. This is helpful because the method according to the invention can be designed and/or operated within certain limits independently of the respective demand for jet fuel. If less jet fuel is needed, some of the intermediate products can be withdrawn and further processed into specific other chemicals as needed.

In step a) of the process, the liquid and/or gaseous hydrocarbons are preferably converted into a product mixture in which the at least one other unsaturated product mixture component is ethylene. Acetylene and ethylene are those representatives of the unsaturated compounds that have a minimal number of carbon atoms. They can react by oligomerization to form saturated hydrocarbons with a higher number of carbon atoms (in the case of acetylene, optionally after prior partial hydrogenation to form ethylene). By adjusting the process conditions, the number of carbon atoms in the products obtained can vary over a wide range.

The product mixture obtained in step a) can contain at least 10% by weight, more preferably at least 20% by weight, very preferably at least 30% by weight, in particular at least 40% by weight, of a mixture of acetylene and contain ethylene.

In step b) of the method, at least one component of the product mixture obtained in step a) is reacted further, so that jet turbine fuel or fuel additive is produced. The conversion of acetylene and/or the min At least one other unsaturated product mixture component, for example ethylene, preferably takes place without the formation of methane. Furthermore, the reaction of acetylene and/or the at least one other unsaturated product mixture component can be carried out in such a way that the molecular weight is only increased during the reaction. Expressed differently, the term "reacting the acetylene obtained in step a) and/or the at least one other unsaturated product mixture component" in the context of the present invention is preferably understood to mean reactions that do not result in the splitting of hydrocarbons to obtain hydrocarbons with a lower number of C lead atoms. Cracking should preferably not be included in the “reacting” in step b).

The reacting in step b) may require that one or more aliphatic hydrocarbons and/or hydrogen be added to acetylene and/or the at least one other unsaturated product mixture component. In this case, the aliphatic hydrocarbons or the hydrogen preferably originate from other processes, i.e. they were not produced in step a) of the present process.

The method according to the invention makes a new raw material base available for the production of synthetic jet fuel. With the process, it is now possible in particular to use hydrocarbons as starting materials that were previously considered less desirable. These are, for example, by-products or by-products that accrue in the production of synthetic jet fuels or fuel additives according to the prior art.

For example, at least 10% by weight, preferably at least 40% by weight, particularly preferably at least 75% by weight, in particular at least 90% by weight, of the liquid and/or gaseous hydrocarbons can be selected from a fraction comprising or consisting of hydrocarbons with up to 10 C-atoms, which is obtained in the production of HEFA (hydroprocessed esters and fatty acids) and/or a fraction comprising or consisting of hydrocarbons with up to 10 C-atoms, which is obtained by Fischer-Tropsch synthesis , and/or a fraction comprising or consisting of hydrocarbons with up to 10 carbon atoms, which is obtained in the production of aircraft turbine fuel additive from alcohol (AtJ).

In a particularly preferred embodiment variant, the liquid and/or gaseous hydrocarbons which are reacted in step a) of the process consist of at least 10% by weight, preferably at least 40% by weight, particularly preferably at least 75% by weight, in particular at least 90% by weight of a fraction consisting of hydrocarbons with up to 10 carbon atoms obtained in the production of HEFA and/or a fraction consisting of hydrocarbons with up to 10 carbon atoms obtained by Fischer-Tropsch -Synthesis, and/or a fraction consisting of hydrocarbons with up to 10 carbon atoms, obtained in the production of aircraft turbine fuel additive from alcohol (AtJ).

The fraction comprising or consisting of hydrocarbons with up to 10 carbon atoms, which is obtained in the production of HEFA, can be regarded as a by-product or co-product arising in the production of synthetic jet fuels or fuel additive according to the prior art. The same applies to the fraction comprising or consisting of hydrocarbons with up to 10 carbon atoms, which is obtained by Fischer-Tropsch synthesis, or the fraction comprising or consisting of hydrocarbons with up to 10 carbon atoms, in the production of aircraft turbine fuel additive is obtained from alcohol (AtJ).

Furthermore, it is preferred if the fraction comprising or consisting of hydrocarbons with up to 10 carbon atoms, which is obtained in the production of HEFA, is based on vegetable and/or animal oils and/or fats of various origins. The vegetable and/or animal oils and/or fats particularly preferably come from sustainable sources (eg from tall oil, algae, waste cooking oils, production waste, ...). In the production of HEFA, the oils and/or fats are hydrogenated, optionally split and/or isomerized (hydrotreatment) in an atmosphere containing H ₂ and then fractionated. A fraction that includes or consists of hydrocarbons with more than 10 carbon atoms, or a fraction that has an average number of more than 10 carbon atoms, can be admixed to jet fuels provided the conditions of ASTM D7566 are met. The light fraction, which contains hydrocarbons with up to 10 carbon atoms or has an average number of less than 10 carbon atoms, cannot be used as an aviation turbine fuel additive. However, the method according to the invention now makes it possible to also upgrade the light fraction to aircraft turbine fuel or fuel additive.

The circumstances under which the fraction comprising or consisting of hydrocarbons with up to 10 carbon atoms in the Fischer-Tropsch synthesis or in the production of aircraft turbine fuel additive from alcohol (AtJ) are obtained are known to the person skilled in the art. noted however, that the fraction comprising or consisting of hydrocarbons with up to 10 carbon atoms, which is obtained by Fischer-Tropsch synthesis, does not have to be the fraction usually referred to as "FT Crude". The fraction can correspond to an after-treated “FT Crude” fraction, the after-treatment being able to consist, for example, of hydrotreatment, in particular hydrocracking, and/or refining. The same applies to the fraction comprising or consisting of hydrocarbons with up to 10 carbon atoms, which is obtained from alcohol (AtJ) in the production of aircraft turbine fuel additive. Again, this fraction does not have to be a direct product of an AtJ process that is limited to its essential steps. Rather, this fraction may have gone through various post-treatment steps.

Optionally, the liquid and/or gaseous hydrocarbons that are converted in step a) of the process can also contain fractions of biomethane. Biomethane is methane that is not of fossil origin. Biomethane can, for example, be produced from biogenic substances by means of fermentation. Methane generated from synthesis gas (carbon monoxide and/or carbon dioxide and renewable hydrogen, e.g. hydrogen from biogenic sources and/or obtained with the help of renewable electricity) can also be understood as biomethane in the context of the present invention. In order to avoid that the consumption of sustainable biogenic raw materials or other renewable energy sources is increased unnecessarily by the method according to the invention, biomethane is generally only used if there is not enough by-product or co-product that is used in the production of synthetic jet fuel or - state-of-the-art fuel additive is available. The liquid and/or gaseous hydrocarbons which are reacted in step a) of the process preferably consist of at most 60% by weight, particularly preferably at most 25% by weight, in particular at most 10% by weight, of biomethane.

In the event that biomethane makes up at least part of the liquid and/or gaseous hydrocarbons, it does not have to be taken directly from a biogas plant. Instead, biomethane can also be transported via the natural gas network.

In a preferred embodiment, the synthetic jet fuel or fuel additive produced by the process according to the invention comprises at least 90% by weight hydrocarbons which have 6 to 24 carbon atoms, particularly preferably 7 to 20 carbon atoms, in particular 8 to 18 carbon atoms, for example 8 to 16 carbon atoms. The synthetic jet fuel or fuel additive produced by the process according to the invention preferably comprises or consists of hydrocarbons which have a molar average number of 10 to 14 carbon atoms.

The conversion of the hydrocarbons in step a) of the method according to the invention preferably comprises a partial oxidation or takes place—at least partially—in the plasma state.

If the reaction of the hydrocarbons includes partial oxidation, the process conditions in step a) of the process according to the invention preferably correspond to those of the Sachse-Bartholome process or the Montecatini process.

When the conversion of the hydrocarbons occurs at least partially in the plasma state, the plasma state can be generated either at low or moderate temperature (cold or non-thermal plasma) or at high temperature (thermal plasma).

The conversion of the hydrocarbons in step a) preferably takes place in the thermal plasma state.

The term "plasma" according to A. Fridman (Plasma Chemistry, Cambridge University Press, 2009) generally refers to a gas containing free electrons and ions. However, a plasma state is often only spoken of when a gas contains electrically charged particles in an amount sufficient to influence and sufficiently change its electrical properties and behavior compared to the normal gas state. An example of an electrical property is electrical conductivity. Electrical conductivity is increased in the plasma state, particularly in the plasma state assumed at elevated temperatures (i.e., thermal plasma state) over electrical conductivity in the gaseous state (see, e.g., tabulated data for hydrogen, nitrogen, oxygen, air, and selected noble gases in M.I. Boulos, Thermal Plasmas, Fundamentals and Applications, Vol. 1, 1994).

From the field of acetylene production by means of a plasma, the person skilled in the art is familiar with various methods and apparatuses which are suitable for generating the plasma. They can be used in step a) of the method according to the invention in order to convert the hydrocarbons into a plasma state. For further details on suitable processes and apparatus, reference is made at this point to the entry on "acetylene" in Ullmann's Encyclopedia (cf., for example, the explanations on the processes and Reactors developed by Hoechst and Chemische Werke Hüls in the 2012 English edition of Ullmann's Encyclopedia).

The conditions mentioned above for the reaction in step a), i.e. the reaction comprising partial oxidation or the reaction at least partially in the plasma state, make the method according to the invention robust and contribute to the fact that the composition of the starting materials can be changed to a certain extent. In addition, the apparatus and process conditions used for this reaction in step a) can also be adapted to the composition of the starting materials. Due to the large number of these degrees of freedom, the method according to the invention is particularly flexible in use.

Mixtures of a wide variety of hydrocarbons in different proportions by weight can be used as starting materials for the process according to the invention. It is preferred that the hydrocarbons used as starting materials for the process according to the invention are liquid and/or gaseous at normal pressure and room temperature, or are liquid and/or gaseous at least after appropriate heating before conversion step a). As a result, the method according to the invention can be operated cost-effectively. If the market price for one of the hydrocarbons used increases, another, preferably cheaper, hydrocarbon can be used instead.

The reaction of the hydrocarbons in step a) can comprise a step a1) in which at least some of the hydrocarbons are reacted in a first reaction zone of an apparatus. If the reaction in step a) includes partial oxidation or takes place at least partially in the thermal plasma, the first reaction zone preferably has an average temperature of 1200 to 2500° C., particularly preferably 1300 to 2200° C., in particular 1400 to 2000° C., at at least one position °C, on.

The mean temperature is preferably the arithmetic mean which results from the temperatures at several points evenly distributed over the cross section of the apparatus (the cross section is to be understood perpendicular to the main flow direction of the hydrocarbons and/or the product mixture components). These temperatures can be measured, but they can also be determined by simulation, for example CFD simulation.

In a further preferred variant of the process according to the invention, the hydrocarbons which are reacted in step a) are divided before they enter the apparatus. A first portion of the hydrocarbons is fed into the first reaction zone of the apparatus, so that at least some of the hydrocarbons are converted in step a1). Another portion of the hydrocarbons can be fed into the apparatus downstream of the first reaction zone separately from the first portion of the hydrocarbons and combined with the at least partially reacted first portion of the hydrocarbons.

Thus, the other part of the hydrocarbons can be fed to a step a2) together with the at least partially converted first part of the hydrocarbons. In step a2), the other part of the hydrocarbons is also at least partly reacted in a second reaction zone of the apparatus. In this case the second reaction zone is arranged downstream of the first reaction zone. If the reaction in step a) includes partial oxidation or takes place at least partially in the thermal plasma, the second reaction zone preferably has an average temperature of between 500 and 1200° C., particularly preferably between 600 and 1100° C., in particular between 700 and 1000 °C, the method according to which the mean temperature is determined has already been described above. In this temperature range, for example, dehydrogenation reactions can take place, for example an alkane from the rest of the hydrocarbons can be converted to the corresponding alkene and hydrogen. Alternatively or additionally, transfer hydrogenation reactions can take place, for example by converting acetylene and an alkane into ethylene and the relevant alkene. Such transfer hydrogenation reactions and process conditions under which these reactions can occur are, in connection with the production of ethylene, for example from WO 2007/003312 A1 and the WO 2007/082746 A1 known.

In the process variant described above, in which the first reaction zone has a temperature of from 1200 to 2500° C., the other part of the hydrocarbons can act as a quench stream in a number of ways. On the one hand by the sensible heat that is required to heat up the other part of the hydrocarbons when the temperature of the other part of the hydrocarbons is lower than the average temperature in the apparatus at the feed point of the other part of the hydrocarbons. On the other hand, by the latent heat that is required to vaporize the other part of the hydrocarbons if this other part is fed in liquid. Furthermore, by endothermic reactions, which enter the other part of the hydrocarbons after feeding into the apparatus can, for example, dehydrogenation reactions (a kind of chemical quenching).

The weight ratio between the first part of the hydrocarbons that goes through step a1) and the further part of the hydrocarbons that is fed separately therefrom downstream of the first reaction zone should preferably be adjusted so that after feeding in the further part of the hydrocarbons at least one Position in the second reaction zone an average temperature of at least 500 ° C, more preferably at least 600 ° C, especially at least 700 ° C results. The weight ratio can depend on various parameters, for example on the specific energy input into the first part of the hydrocarbons in step a1), the composition, the temperature and/or the state of aggregation of the other part of the hydrocarbons at the feed point and can therefore vary within wide ranges.

In a further preferred process, the hydrocarbons which are converted in step a) are taken from different sources or different stocks. For example, a first part of the hydrocarbons, which is reacted according to step a1) in a first reaction zone of an apparatus, comes from a first source or a first supply, while another part of the hydrocarbons, together with the at least partially reacted first part of the hydrocarbons fed to step a2) originates from a second source or from a second supply.

Two separate hydrocarbon streams are preferably fed to the apparatus in which the reaction of step a) takes place, it being possible for the two streams to be fed from different sources or different supplies and to have different compositions. The first hydrocarbon stream which is reacted in step a1) in a first reaction zone of an apparatus particularly preferably has a higher average molar mass than the second hydrocarbon stream which is fed to step a2) together with the at least partially reacted first part of the hydrocarbons.

The process control with regard to the temperature and the optional separate introduction of a further part of the hydrocarbons in step a) can be controlled in such a way that part of the acetylene is converted to ethylene by means of transfer hydrogenation and/or to other downstream products, in particular to elemental, by means of other reactions carbon and hydrogen. In this way, a desired ratio of acetylene to the at least one other unsaturated product mixture component can be set. If, for example, a low ratio is desired, it can be advantageous to choose the conditions in step a2) in the second reaction zone in such a way that the highest possible conversion of acetylene takes place, so that at the end of step a) the molar ratio of acetylene increases of the at least one other unsaturated product mixture component is less than 1.0, in particular less than 0.5.

The product mixture from step a) can also contain elemental carbon, which is removed before step b). Before the elemental carbon is separated off, the product mixture obtained in step a) is preferably at least partially cooled. This is done, for example, using a heat exchanger, preferably with the simultaneous generation of steam. Alternatively or additionally, the product mixture can be cooled in a heat exchanger with preheating of the liquid and/or gaseous hydrocarbons used in step a). The latter is preferred in terms of energy, since the heat of the product mixture can be reused directly in the process according to the invention. The cooled product mixture is preferably transferred to a solids separator. There, elementary carbon can preferably be separated as carbon black, for example by means of a cyclone, a filter or a scrubber or a combination of these devices.

The separated carbon is preferably sequestered or put to a use in which the separated carbon is not converted into CO ₂ .

A use in which the separated carbon is not converted into CO ₂ is any material use of carbon in which complete oxidation or combustion does not take place. For example, carbon can be used to replace industrial carbon black or added to asphalt, bitumen or cement. In this way, the method of the present invention helps remove carbon from the atmosphere. The use of the carbon produced without complete oxidation or combustion thus has a positive effect on the CO ₂ footprint of the process and the products produced, in particular the synthetic jet fuel or fuel additive.

In a variant of the method according to the invention, the amount of elementary carbon that is generated and sequestered or used as a material without CO ₂ formation can be made dependent on the CO ₂ footprint of the hydrocarbons used as starting materials. The higher CO ₂ footprint of the starting materials, the greater is preferably the amount of elemental carbon.

It is also possible, especially if the conversion of the hydrocarbons in step a) takes place at least partially in the plasma state, the amount of elemental carbon that is generated and sequestered or used as a material without CO ₂ formation depends on the availability of renewable or other CO ₂ low electrical energy generated, especially the CO ₂ footprint of the electricity used. In this context, the term renewable energies is understood to mean regenerative energies from wind power and/or PV sources and/or hydroelectric power and/or geothermal power plants and/or tidal power plants and/or power plants with biogenic input materials. The method is particularly preferably operated in such a way that the generation of the carbon and sequestration or use without CO ₂ formation is adapted to the time-varying CO ₂ footprint of the stream. For example, if there is a large supply of renewable electrical energy or if the CO ₂ footprint of the electricity used is small, the amount of elemental carbon is preferably smaller.

The person skilled in the art can set the amount of elemental carbon which is formed in step a) by choosing suitable process parameters. This is possible without interrupting the process or during ongoing operation. Suitable process parameters which have a direct influence on the amount of elemental carbon are, for example, the temperature and the residence time of the hydrocarbons in step a), in particular the temperature and residence time in the second reaction zone. For example, a higher mean temperature and a longer residence time in the hot reaction zone can be achieved within the given limits by throttling the feed stream of liquid and/or gaseous hydrocarbons under otherwise the same conditions. Alternatively or additionally, to achieve a higher average temperature and a longer residence time in the hot reaction zone, the average molar mass of the starting materials (i.e. the liquid and/or gaseous hydrocarbons) can be increased while the process parameters otherwise remain the same.

The process parameters can be selected, for example, so that the amount of elemental carbon that is formed in step a) is 2 to 80%, preferably 5 to 60%, in particular 10 to 40% of the amount of carbon that is in step a ) used hydrocarbons.

The reaction in step b) of the process according to the invention preferably comprises the following process steps: b1) fractionation, with an olefin-rich fraction being obtained, and b2) oligomerization of the olefin-rich fraction. The olefin-rich fraction can also be a fraction that consists exclusively of olefins. Further olefin-rich fractions from other processes can also be added to the olefin-rich fraction before the oligomerization. The other olefin-rich fractions can have a proportion of 10 to 90% by weight, preferably 20 to 80% by weight, particularly preferably 25 to 75% by weight, of the fraction resulting after the addition. The olefin-rich fraction which is oligomerized in step b2) preferably contains at least 20% by weight of ethylene, preferably at least 50% by weight, particularly preferably at least 80% by weight of ethylene, very particularly preferably at least 97% by weight of ethylene .

In a preferred embodiment, catalysts and/or reaction conditions for the conversion of olefins according to the prior art of the AtJ process are used for step b2).

At least some of the oligomers from step b2) are optionally hydrogenated in a step b3) and then optionally fractionated. This is dependent on the level of olefin content that is considered acceptable in the fuel to be produced. In a preferred embodiment, catalysts and/or reaction conditions for the hydrogenation of olefins according to the prior art of the AtJ process are used for step b3).

The acetylene obtained in step a) or a portion thereof can be selectively hydrogenated to ethylene before step b). The selective hydrogenation preferably proceeds over a catalyst. Some of the ethylene can be recycled and combined with the product mixture from step a), which has not yet been hydrogenated, from which any elemental carbon present has already been separated off. The selective hydrogenation results in lower acetylene concentrations, which is advantageous for heat management, catalyst service life and/or selectivity, since the hydrogenation of acetylene is highly exothermic.

In a preferred variant of the process according to the invention, at least part of the acetylene obtained in step a) and/or part of the at least one other unsaturated product mixture component is separated off before step b) and further processed into products other than aircraft turbine fuel and fuel additive.

The products that differ from jet fuel and fuel additive include, for example, polyolefins, in particular polyethylene, polypropylene and copolymers and blends of the aforementioned; vinyl acetate; acrylic acid; vinyl chloride; and acrylonitrile. To produce the polyolefins, all alpha-olefins contained in the at least one other unsaturated product mixture component are preferably separated off and then polymerized. To produce the products vinyl acetate, acrylic acid, vinyl chloride and acrylonitrile, acetylene is separated off and reacted with various reactants. Vinyl acetate can be produced from acetylene and acetic acid, for example, while hydrogen chloride is required in addition to acetylene to produce vinyl chloride.

In the process according to the invention, advantages can also result from separating off or using the elemental hydrogen still present in the product mixture in step a). This can be separated off in step b) and/or at least partly used for the hydrogenation, in particular for the hydrogenation in step b3). In a further preferred process variant, at least some of the hydrogen separated off is used to dilute the hydrocarbons before the reaction in step a).

It is also preferred that those product mixture components that are not used either for the production of aircraft turbine fuel and fuel additive or for the production of other products are wholly or at least partially recycled and reused as liquid and/or gaseous hydrocarbons in step a).

character list

• 1 zeigt das AtJ-Verfahren nach dem Stand der Technik.
• 2 zeigt ein Fließbild als Beispiel für das erfindungsgemäße Verfahren.

Preferred embodiments of the invention are explained in more detail with reference to the following figures, without wishing to limit the invention thereto.

• 1 shows the AtJ method according to the prior art.
• 2 shows a flow chart as an example of the method according to the invention.

At the in 1 In the AtJ process shown, ethanol is first dehydrated in step 1 and thus converted to ethylene. In a step 2, ethylene is then oligomerized to give a mixture of hydrocarbons having the desired average molar mass and/or molar mass distribution. Since the resulting mixture, which is obtained in this way, generally contains more unsaturated hydrocarbons than desired, it is hydrogenated in step 3 using molecular hydrogen as required. The resulting product is finally fractionated in a step 4, so that a fraction K suitable as jet fuel and by-products NP are obtained, for example using thermal separation processes, in particular rectifications. The fraction that is to serve as jet turbine fuel or fuel additive K comprises at least 90% by weight of paraffinic hydrocarbons having 8 to 18 carbon atoms per molecule.

The illustration in 2 shows an embodiment of the method according to the invention, in which at least part E1 of the hydrocarbons in step a) is reacted in the plasma state and with the formation of acetylene and at least one other unsaturated component, the plasma being a thermal plasma here and one in a first reaction zone RZ1 Reactor is generated by applying an electrical voltage between two electrodes. A part E2 of the hydrocarbons is fed into a second reaction zone RZ2 downstream of the first reaction zone RZ1 or immediately before it. This part E2 can be regarded as a quench stream since it leads to rapid, noticeable cooling of the at least partially converted stream E1. However, the resulting mixture temperature is still comparatively high, so that further reactions take place even without the addition of catalysts. To a certain extent, the feeding point of the stream E2 marks the beginning of the second reaction zone RZ2. Examples of reactions which take place in the second reaction zone RZ2 are: dehydrogenation of paraffinic hydrocarbons to give the corresponding olefins or the reaction of paraffinic hydrocarbons and acetylene by means of transfer hydrogenation to give the corresponding olefins and ethylene. Some reactions that preferably take place in the second reaction zone RZ2 are given as examples. Among other things, elementary solids can be obtained under these conditions. At the end of the plasma reactor, the product mixture is present at a temperature of, for example, 800.degree. The product mixture is then cooled (not shown), for example with the generation of steam and/or at least partially with preheating of the feed stream E1 and/or the further stream E2. The cooled product mixture is transferred to a solids separator 10 where elemental carbon (carbon black, "CB") is separated, for example by means of a cyclone, a filter or a scrubber or a combination of these devices. The elemental carbon is sequestered (“S”). The remaining portions of the product mixture are passed on to a hydrogenation unit 20 in which acetylene can be selectively hydrogenated (see reaction equation). The product mixture treated in this way is sent to a column 30 for fractionation. Olefinic fractions, ie ethylene, propylene and olefins with more than 4 carbon atoms combined and fed into a reactor 40, in which an oligomerization is carried out up to the desired chain length. The oligomer or oligomer-rich mixture produced is hydrogenated in a unit 50 . A portion of the hydrogen also obtained in the fractionation is used for this purpose. Finally, the product mixture is fractionated 60 into a fraction K that can be used as jet fuel and a by-product fraction NP. At least 90% by weight of this fraction K consists of hydrocarbons which have 6 to 24 carbon atoms.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• WO 2007/003312 A1 [0040]
• WO 2007/082746 A1 [0040]

Claims (10)

A method of making synthetic jet fuel or fuel additive, comprising the steps of: a) converting liquid and/or gaseous hydrocarbons into a product mixture containing acetylene and at least one other unsaturated product mixture component which has 2 to 5 carbon atoms, b) converting the acetylene obtained in step a) and/or the at least one other unsaturated product mixture component to form jet fuel or fuel additive. procedure after claim 1 , wherein at least 10% by weight, preferably at least 40% by weight, particularly preferably at least 75% by weight, in particular at least 90% by weight, of the liquid and/or gaseous hydrocarbons are selected from: - comprising or consisting of a fraction from hydrocarbons with up to 10 carbon atoms obtained in the production of HEFA (hydroprocessed esters and fatty acids), and/or - a fraction comprising or consisting of hydrocarbons with up to 10 carbon atoms obtained by Fischer-Tropsch Synthesis is obtained, and / or - a fraction comprising or consisting of hydrocarbons with up to 10 carbon atoms, which in the production of aircraft turbine fuel additive from alcohol (AtJ) is obtained. Method according to one of the preceding claims, wherein the conversion of the hydrocarbons in step a) comprises a partial oxidation or at least partially takes place in the plasma state, the plasma state preferably being generated by electrical discharge. Process according to any one of the preceding claims, wherein the reacting of the hydrocarbons in step a) comprises: a1) Reacting at least some of the hydrocarbons in a first reaction zone of an apparatus, the first reaction zone preferably having an average temperature of 1200 to 2500° C. at at least one position. procedure after claim 4 , wherein the reaction of the hydrocarbons in step a) further comprises: a2) reaction of at least a further part of the hydrocarbons in a second reaction zone, the second reaction zone being arranged downstream of the first reaction zone and the second reaction zone preferably having at least one position in the middle temperature between 500 and 1200°C. The method according to any one of the preceding claims, wherein the product mixture in step a) also contains elemental carbon, which is separated before step b), wherein the separated carbon is preferably sequestered or at least partially supplied to a use in which no conversion of the separated carbon to CO ₂ takes place. Method according to one of the preceding claims, wherein the reaction in step b) comprises the following method steps: b1) fractionation, whereby an olefin-rich fraction is obtained, b2) oligomerization of the olefin-rich fraction, where appropriate at least some of the oligomers from step b2) are hydrogenated in a further step b3) and then optionally fractionated and where appropriate at least part of a further fraction obtained in step b1) is recycled before step a). Process according to any one of the preceding claims, wherein at least part of the acetylene obtained in step a) is selectively hydrogenated to ethylene before step b), with part of the ethylene formed from acetylene preferably being recycled and combined with part of the product mixture from step a). . Process according to one of the preceding claims, wherein at least part of the acetylene obtained in step a) and/or part of the at least one other unsaturated product mixture component is separated off before step b) and further processed into products other than aircraft turbine fuel and fuel additive. Process according to one of the preceding claims, wherein the product mixture in step a) also contains elemental hydrogen which is separated off in step b) and/or at least partially used for the hydrogenation in step b).

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