EP2342306A2

EP2342306A2 - Method for extracting gaseous hydrocarbons from biogenic raw materials

Info

Publication number: EP2342306A2
Application number: EP09783564A
Authority: EP
Inventors: Volker Heil; Wolfgang Urban; Axel Kraft; Christoph Unger; Karl Meller; Joachim Danzig; Ulrich Seifert; Andreas Menne; Anna Fastabend; Silvana Rossow
Original assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Current assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Priority date: 2008-09-30
Filing date: 2009-09-29
Publication date: 2011-07-13
Also published as: WO2010037756A3; AU2009299885A1; CA2738611A1; US8686210B2; AU2009299885B2; DE102008049778A1; US20110237854A1; CA2738611C; WO2010037756A2; ZA201102101B

Abstract

The invention relates to a method for extracting gaseous hydrocarbons, in particular liquid gas and/or a gas mixture resembling natural gas or one or more components contained in liquid gas or in the gas mixture resembling natural gas. The starting material used contains oxygen-containing hydrocarbons. The method comprises the following steps: providing the starting material – contacting the starting material with a porous catalyst in the absence of oxygen at a temperature of 300-850°C in a converting reactor, resulting in a hydrocarbon-containing product gas mixture, in which the proportion by weight of the gaseous hydrocarbons is greater than that of the liquid hydrocarbons, - collecting the hydrocarbon-containing product gas stream and supplying the product gas stream to a separating device, where product separation is performed.

Description

description

Process for the recovery of gaseous hydrocarbons from biogenic raw materials.

The invention relates to a process for the production of gaseous hydrocarbons, in particular of liquid gas and natural gas-like gas mixtures. Here are partially converted as starting materials oxygen-containing hydrocarbons on a catalyst in short-chain hydrocarbons. The process therefore represents a way to generate recyclables from waste materials (which might need to be eliminated costly).

This patent application claims the priority of German Patent Application DE 10 2008 049 778.9, the disclosure of which is hereby incorporated by reference.

In the past, there have been a number of proposals to convert fats or oils to fuels or other fuels into hydrocarbons. Thus, US Pat. No. 1,960,951 describes a process for the catalytic conversion of vegetable oils to obtain liquid hydrocarbons, in addition to which volatile products are formed. In this case activated carbon is used as the catalyst. The oil to be converted is pressurized by means of a compressed air compressor; then the passage in the liquid state through the heated activated carbon bed. This is a kind of "cracking", at least in the case of vegetable oils such as peanut oil.

DE 103 27 059 Al describes a method in which a fat or oil-containing or fatty acid-containing starting material at a temperature of 150 to 850 ⁰ C in the absence of oxygen in a reactor containing an activated carbon-residue bed is brought cyclically in con-. The fats are split and the Fatty acids decarboxylated and degraded to shorter chain hydrocarbons.

DE 10 2005 023 601 A1 describes a variant of the process according to DE 103 27 059 A1, in which the starting material is brought into contact with the activated carbon in the presence of water or a water-releasing material. Finally, DE 43 35 399 A1 describes a process for converting waste oil or bio-oil into diesel oil-like fuels, in which the vaporized starting material is brought into contact with catalysts containing perovskites at a temperature between 350 and 500 ° C.

All the above processes have in common that essentially liquid hydrocarbons (having at least five carbon atoms) are produced here. Shorter-chain hydrocarbons are only produced as (unwanted) by-products, which are used at best for heating the conversion reactors.

Furthermore, it is known that biomass can be converted into synthesis gas, from which alkanes are synthesized in the Fischer-Tropsch process. From the synthesis gas (H ₂ + CO) below hydrocarbons of different chain length are first rebuilt. The Fischer-Tropsch process also has the disadvantage that it can be economically implemented only on a very large scale and is associated with a considerable expenditure of energy.

It is also known to produce ethanol from biogenic raw materials (see, for example, BS Nordhoff, "Renewable raw materials in the chemical industry - away from oil?" Chemical Engineering 79 (5), 551 to 560). From this hydrogenation could be used to produce the pure hydrocarbon butane. However, this makes little sense commercially. Finally, it is known that n-heptane can be converted to carbon compounds of 2 to 4 carbon atoms by cracking zeolite catalysts (Rane, N., et al., "Cracking of n-heptanes over Bronsted acid sites and Lewis acid ga sites in ZSM -5 zeolites "Microporous and Mesoporous Materials 110, 2008, 279). However, this is a process that requires only a one-time cracking of the starting material in order to obtain fragments with 3 or 4 carbon atoms.

The present invention is therefore based on the object to overcome the disadvantages of the prior art and to provide a method by which oxygen-containing hydrocarbons or hydrocarbon mixtures in gaseous hydrocarbons, especially in liquefied petroleum gas and / or a natural gas-like gas mixture to convert.

This object is achieved by the method according to claim 1. Subclaims indicate advantageous developments.

According to the invention, for the production of gaseous hydrocarbons, a starting material containing or consisting of oxygen-containing hydrocarbons at a temperature of 300 to 850 ^° C. in the absence of unbound oxygen in a conversion reactor containing a porous catalyst is brought into contact with this catalyst so that a product spectrum is obtained in which the weight fraction of the gaseous hydrocarbons is greater than that of the liquid hydrocarbons. The fats, alcohols, polyols or organic acids contained in the starting materials are cleaved and the oxygen is at least partially removed from the compounds. In particular, CO and CO2 are formed from the oxygen. Fatty acids are decarboxylated and the long-chain hydrocarbons are converted into shorter-chain hydrocarbons. The product gas stream (which in addition to the hydrocarbons also carbon monoxide, carbon dioxide, hydrogen and an nertgas) is - if necessary - brought to the condensation in order to separate under normal conditions liquid hydrocarbons. Inert gases such as carbon dioxide and nitrogen can be recycled to the reactor for inerting.

According to the invention, a gaseous hydrocarbon is understood in particular to mean a hydrocarbon having chain lengths of 1 to 4 carbon atoms. The gaseous hydrocarbons therefore have a boiling point of less than 30 ^° C. at normal pressure (1013 mbar). Preferably, the gaseous hydrocarbons - as indicated in DIN 51622 - have a vapor pressure less than or equal to 13 bar at a temperature of 70 ⁰ C. In contrast, a liquid hydrocarbon is understood in particular a hydrocarbon having more than four carbon atoms. The boiling point of the liquid hydrocarbons is in particular greater than or equal to 28 ° C at atmospheric pressure (1013 mbar).

According to the invention, liquefied gas is understood as meaning hydrocarbons and mixtures thereof which contain essentially hydrocarbons having three or four carbon atoms. In particular, liquefied petroleum gas contains hydrocarbons selected from the group consisting of propane, propene, butane / isobutane, butene / isobutene or mixtures of 2 or more of the substances mentioned or consists thereof. Furthermore, a liquefied gas is understood in particular to be a mixture for domestic and commercial purposes in accordance with DIN 51622. According to this standard, blends for domestic and commercial purposes should contain no more than 60% by weight of hydrocarbons with four carbon atoms. At least 95% by mass thereof is composed of butane and butene isomers, the content of butane isomers having to predominate. The proportion of hydrocarbons with three carbon atoms must consist of at least 95% of propane and propene and the propane content must prevail.

Under a natural gas-like gas mixture is understood according to the invention a gas mixture whose proportion of hydrocarbon fen with one or two carbon atoms corresponding to the corresponding hydrocarbon content in pure natural gas (or at least the methane content in pure natural gas) or exceeds this proportion. In a natural gas-like gas mixture, therefore, the proportion of the components methane, ethane and ethene is at least 85 percent by volume, preferably more than 95 percent by volume and more preferably greater than 99 percent by volume.

The starting materials used according to the invention are oxygen-containing hydrocarbons or hydrocarbon mixtures. The starting materials are in particular biogenic starting materials. To mention in particular are as starting materials lipids and fat-like compounds; Starting materials which contain lipids and / or fatty compounds are understood here to mean that the starting materials contain or consist of lipids and / or essential constituents of lipids (such as polyalcohols or glycerol and also mono- and diglycerides). The hydrocarbons contained in the starting material usually consist of at least 99 wt .-% of oxygen-containing hydrocarbons. But it can also be used starting materials with a lower proportion of oxygen-containing hydrocarbons. In addition, water may also be present in the starting material; its proportion can be up to 25% by weight or more, based on the total weight of the starting material. For example, the proportion of water in used grease is often up to 8% by weight of water; The same applies to glycerine from the production of biodiesel, in which the water content may also be 20% by weight. In addition, glycerol from biodiesel production may still contain traces of catalyst and biodiesel.

According to the invention, a porous catalyst is understood as meaning a substance whose surface has pores which are accessible to the starting material or substances contained in it and which is capable of containing the starting material or the substances contained therein Cleave sections or catalytically support the cleavage of the starting material. Particularly suitable catalysts here are finely porous substances (ie substances having pores with a pore diameter less than or equal to 20 μm). Of these, according to the invention, substances which contain mesopores and / or micropores and / or submicropores are preferred (according to the IUPAC definition

[http://goldbook.iupac.org/M03853.html] mesopores have a pore diameter of 2 to 50 nm, micropores a pore diameter of 0.4 to 2 nm, and submicropores a pore diameter of less than 0.4 nm).

For the first time, the process according to the invention offers the possibility of achieving high yields of liquid gas components and natural gas-like gas mixtures by the cleavage of precursors, such as fats and oils, in particular biogenic precursors. The prior art processes are essentially designed to break down fats and similar materials to longer chain hydrocarbons. Essentially, therefore, these processes are about supplying the starting materials to the

Break down bonds formed between carbon atoms and heteroatoms. Cleavage of carbon-carbon bonds, on the other hand, is only of limited importance or even undesirable. In contrast, in the process of the invention, the cleavage of carbon-carbon bonds is much more important, so that the catalysts and the process parameters are designed to ensure a multiple cleavage of pure hydrocarbon chains. In contrast to the previously known methods, therefore, as a rule, at least twice as many carbon-carbon bonds as carbon-heteroatom bonds are cracked.

In contrast to the Fischer-Tropsch process, significantly fewer carbon-carbon bonds must be broken according to the invention; This provides a much less energy-intensive process. Furthermore, an advantage over the Fischer-Tropsch synthesis is that the There is no need for downstream downstream processing, which is unavoidable due to the formation of very long-chain, waxy by-products and is responsible for limiting the economy to a very large scale.

The product spectrum achieved by the process according to the invention, in which the proportion by weight of the gaseous hydrocarbons is greater than that of the liquid hydrocarbons, can be achieved in particular by realizing one or more of the following parameters or process characteristics: a.) Products with a chain length of more than four Carbon atoms are wholly or partially added to the starting material or "re-fed" to the conversion reactor, and these products can be fed into one of the process or mass transport steps prior to conversion. that the C 1 to C ₄ components are obtained in gaseous form, so that the liquid, longer-chain components can easily be separated off. b.) The residence times of the material to be cracked on the catalyst relate As the feed stream to catalyst ratios can be increased. In a batchwise procedure of the method according to the invention, the feedstream to

Catalyst ratio 0.1 to 1 gf _ee d * h ^-1 per gκataiysator and be ^¬ preferably 0.2 to 0.5 gfeed * h ^-1 per gκataiysator amount. In a continuous operation, the feed to catalyst ratio should be about 5 to 50 g _fee per g catalyst. The longer residence times on the catalyst cause multiple breaking of carbon-carbon bonds in one and the same starting molecule. c.) The process can be carried out at a higher pressure than in the prior art. It can be done not only at pressures between 20 and 2000 mbar, but also at pressures between 2000 and 20,000 mbar. Due to the higher pressure it can be achieved that the molecules to be cracked stay absorbed longer and / or more frequently at the reactive centers of the catalyst. This is advantageous if carbon-carbon bonds are to be cracked d.) The process according to the invention can be carried out at temperatures of from 300 to 700 ^° C., preferably at from 550 to 650 ^° C., in the conversion reactor. As a rule, the temperature is at least 450 ^° C. As with elevated pressure, elevated temperatures also lead to preferential breaking of carbon-carbon bonds in the cracking process, and therefore the product spectrum shifts to shorter-chain hydrocarbons. e.) The porous catalysts used may have a pore spectrum and / or a specific surface which is tailored to the starting materials to be converted. As a rule, this also ensures that even long-chain hydrocarbons are cracked to short-chain (Ci to C ₄ ) hydrocarbon fragments.

The starting material used according to the invention preferably contains or consists of biogenic lipids and / or waste oils / lubricants. The lipids are preferably selected from the group consisting of fats, oils, fatty acids, fatty acid esters, tall oils, monoglycerides, diglycerides and polyols. Examples include the polyols glycerol and sorbitol and fatty acid methyl esters. In the case of fats and oils, especially old fats and waste oils are considered. The term fats and oils here is a collective term for solid, semi-solid or liquid, more o or less viscous products of the plant or animal body, which consists essentially of mixed triglycerides of higher fatty acids with even number of carbon atoms and small amounts of acyl lipids like sterol esters and unsaponifiable ones. In the unsaponifiable portion are often many impurities such as mineral oils, plasticizers and biocides, which accumulate in fat due to their lipophilic character before. Catalysts which can be used according to the invention are, in particular, catalysts selected from the group consisting of activated carbons, carbon molecular sieves, activated cokes, carbon nanotubes, zeolites, and mixtures thereof, or mixtures of these substances (or mixtures) with perovskites and / or zinc chloride ,

As perovskite catalysts - in which the perovskites are usually present on a support material - for example, the DE 43 35 399 Al mentioned perovskite catalysts are suitable. Zinc chlorides are described, for example, in A. Demirbas et al. (2006) "New Options for Conversion of Vegetable Oil to Alternative Fuels." Energy Sources, Part A FIELD Filling Journal Title: Energy Sources, Part A: Recovery, Utilization, and Environmental Effects 28 (7): 619-626. All the above catalysts have in common that they have a large surface area. In part, acidic sites are present in the catalysts, which can also cause cleavage of bonds.

The porous catalyst particularly preferably has mesopores and / or micropores. It has been observed that in particular a proportion of at least 20% (in% of the total pores) of pores with a pore diameter greater than or equal to 20 nm can lead to an increased formation of gaseous hydrocarbons.

According to the invention, it has been found that in the case of catalysts which have a pore spectrum in which pore sizes between 0.4 nm and 10 nm in diameter are present in any order of magnitude, it is ensured that any molecule of the starting material or molecule fragment to be cracked in one can be sorbed the molecular size corresponding to about the same size number of pores, preferably a formation of hydrocarbons having one to four carbon atoms runs. To achieve this, it is also possible, for example, to use a mixture of different catalysts, for example a mixture of different zeolites. examples For example, zeolites usually have average major pore radii between 3.3 and 15 nm.

A particularly fine adjustment of the pore sizes and the Pore renverteilung and the catalyst surface is possible with activated carbons, which are therefore particularly well suited for the inventive method. For starting materials containing shorter-chain hydrocarbon fragments, activated carbons with lower pore radii are available; for larger starting molecules, e.g. Triglycerides with long-chain fatty acid

Substituents are available activated carbons with larger pores. The pore sizes can be influenced, for example, by the activation of the activated carbon. Thus, by physical activation methods (for example steam activation) smaller pores are available; These are made by widening of

Submicropores and very small micropores obtained. By chemical activation, larger pores (especially a larger proportion of mesopores) are obtained. Due to the chemical or physical activation, part of the carbon is selectively decomposed, which then results in the pore structure.

In the gas activation (physical activation) the starting material is normally at 800-1000 ⁰ C is activated, if necessary in a water vapor and / or carbon dioxide atmosphere for a carbonization process. Here, part of the carbon is gasified and pores are formed which form a large inner surface. Starting material as well as temperature and duration determine the later pore size and distribution. Therefore, the manufacturing process is particularly important for the properties of the coal. In chemical activation, for example, phosphoric acid,

Zinc chloride or other dehydrating materials used. With regard to the materials for the chemical activation, reference is made to H. von Kienle, E. Bäder, "activated carbon and its industrial application", Ferdinand Enke Verlag, Stuttgart, 1980, to which reference is made in full. Average pore sizes, which are between those of chemically or physically activated carbons, have activated granules (also called direct activates). In contrast to the form activated carbon, in which a carbon source is first mixed in powder form with a binder, followed by shaping, optionally drying, carbonization and activation, these activated granules are directly from the carbon support by comminution and activation and optionally interposed Carbonation step obtained. The pore structure can also be influenced by the parameters prevailing in the production of the activated carbon. In particular, this temperature, residence time and vapor dosing during drying, carbonation and activation are mentioned.

An influence on the cracking behavior of the porous catalyst on the one hand, and (in the case of activated carbon as a catalyst) the pore size of the catalyst can also by a catalyst added to the substance (in the present application called second catalyst), wherein the porous catalyst with the second Catalyst can be doped and / or impregnated.

In this case, doping means that the second catalyst is added to the porous catalyst during its production, so that a homogeneous distribution of the second catalyst is present in the finished porous catalyst. In contrast, in the impregnation treatment of the already finished porous catalyst is carried out with a material containing or consisting of the second catalyst, so that the second catalyst is present only on the surface (also the pore surface) of the porous catalyst. By means of a doping and / or impregnation, chemically active substances can thus be deliberately introduced into the pore system or the matrix of the catalyst, which can change the chemical reactions on the catalyst. As doping or impregnating substances in particular substances can be introduced, which themselves act once again catalytically; Alternatively, it is also possible to introduce substances which alter the properties of the porous catalyst (for example the pH value). Depending on the method used, the physical and adsorptive properties of the porous catalyst are also changed.

In the case of impregnation-which takes place as mentioned later-it should be noted that the application of the impregnation reagent changes the pore spectrum and reduces the pore volume. In particular, very small pores are blocked, so that in the case of impregnated substances, the proportion of large micropores and the mesopores is increased in comparison to small micropore. If, therefore, an impregnated catalyst is to be used for the process according to the invention, it is often necessary to mix in an unimpregnated catalyst, so that even small micropores (with a

Diameter smaller than 1 nm) in an amount sufficient to allow cracking even to the short chain hydrocarbons of 1 to 4 carbon atoms. In the case of doping with metal oxides or substances which form metal oxides (for example potassium carbonate) during the production process of the porous catalyst, active centers in which agglomerates of the metal oxide or clusters of the metal oxide are formed are formed in the finished porous catalyst (for example the finished activated form coal) which can then be cracking reactions.

It has been observed that the addition of acids to the porous catalyst generally results in a shift in the product spectrum towards liquid products (ie, hydrocarbons having more than four carbon atoms). According to the invention, it is therefore preferable to dope or impregnate the porous catalyst (for example the activated carbon) with alkaline components or to use not only acid-impregnated / doped catalysts but also undoped / unimpregnated or non-acid-doped / impregnated catalysts. In this case, especially when using alkaline-doped and / or impregnated porous catalysts, the pro- range of products to gaseous hydrocarbons. Due to the above-described problem in the impregnation of the catalysts, the use of doped catalysts is preferred.

It is also possible to add second catalysts to the porous catalyst according to the invention which serve to remove pollutants or foreign substances from the starting material or to convert them into separable gases. For example, it is conceivable to convert sulfur contained in the starting material by means of suitable catalysts (for example based on manganese oxide).

With regard to the preparation process for doped catalysts and the possible dopants (ie the second catalyst), reference is made to WO 2007/137856 A2, to which reference is made in full in this regard.

In an advantageous embodiment, the inventive method can be carried out so that the starting materials are supplied to the conversion reactor in liquid form. This has the advantage that an energy-intensive transfer of the unconverted starting material into the gas phase (or vapor phase) is not required; however, pressures greater than 2000 mbar are required in this variant.

On the other hand, if the raw material in the vapor or gas phase is transferred to the conversion reactor, it should be considered that even in the apparatus in which the starting material is transferred to the vapor or gas phase (in particular a combined reaction and phase change apparatus, in the an evaporation of the starting material and / or a decomposition of the starting material into vaporizable products and an evaporation thereof takes place - referred to in the context of this application evaporator) cracking processes can take place, so that the starting material already substantially in chemically altered form (eg in the form of Fragments) with the porous catalyst comes into contact. It is then also possible to use catalysts (in particular activated carbons) with a reduced proportion of very large pores (in particular mesopores). Such cracking processes take place especially when the starting material can not evaporate without decomposition, which is the case with triglycerides, for example; however, cracking processes generally also occur in the case of the undecomposable compounds which can be vaporized. In order to deliberately force a cleavage of the starting material or further cleavage of already cracked starting material in the evaporator, the mean wall temperature in the evaporator can be chosen so that it lies above the evaporation or decomposition temperature of the starting material (and in particular at least 50 ^° C.) above this temperature). The average wall temperature may be, for example, 340 to 500 ^° C. In the case of a starting material which consists of a mixture of different substances, the decomposition temperature of the starting material in accordance with the invention is defined as the temperature at which decomposition of at least 80% by weight of the sum of the substances vaporisable in the starting material takes place (can not be vaporized in this case considered compounds which are still liquid or solid at a temperature of 600 ⁰ C and not decompose, ie compounds which neither by themselves nor in the form of decomposition products in the vapor or gas phase can be converted). In one embodiment, the temperature in the evaporator may already substantially correspond to the temperature in the conversion reactor or may be only slightly below it (ie up to 50 ° C.); in individual cases, it can also be above this temperature.

In one embodiment, the evaporator employed contains at least partially cracking rate enhancement elements on its inner surface (ie, the surface which is in contact with the vaporized or vaporizable matter). According to a first variant, such elements for increasing the cracking rate may be chemically adapted surfaces or surface areas (which may be present in the form of a coating, for example). can), which may have in particular acidic centers (in particular, surfaces or surface areas of acidic metal oxides, for example of alumina, silica or silicates) may be mentioned. According to a second variant, these elements can be geometrically designed to increase the cracking rate in such a way that they contain regions whose temperature is markedly higher than the average wall temperature; To name for example, pyramidal structures, conical structures or similarly shaped structures whose point directed towards the evaporator inside due to high thermal conductivity of the material (in particular a metal, eg aluminum), from which they are formed, has a relation to the mean wall temperature significantly elevated temperature.

In a further advantageous embodiment, the method according to the invention can be carried out such that the contacting of the starting material with the porous catalyst takes place in the presence of water and / or a water-releasing material. The addition of water or water-releasing materials makes it possible to extend the service life of the catalyst. The addition of water is therefore useful, especially in the case of continuous processes. At least as much water should preferably be present that, based on the starting materials to be converted, at least one molar equivalent of water (in free form or in water)

Form of water-releasing substances) is present. In general, a water-releasing material is understood to mean a substance or a mixture of substances which contains either bound water which can be released or a substance or substance mixture which forms water by means of a chemical reaction, for example a condensation reaction (for example glycerol).

More preferably at least 10 percent by volume of water and / or based on the starting materials to be converted, at least two molar equivalents of water are present in the reaction space in the local and time average. The addition of water can be effected in particular by introducing a stream of water or vapor into the conversion reactor. Instead of water, water-containing substances or substances which split off water under the reaction conditions prevailing in the conversion reactor can also be used here. The

Water, water-containing mixture or water-releasing material can also be added to the starting materials. Often, the starting materials already contain water. Finally, the water or water-releasing material may also be added to the inert gas stream.

As a conversion reactor, any suitable, heatable furnace can be used. The conversion can be continuous or not continuous. By continuous operation, it is to be understood that the supply of starting materials takes place continuously. In particular, the starting materials can be added in gaseous or vaporous form. Conversion reactors thus come into consideration as fixed bed reactors of any type, moving beds, stationary and circulating fluidized bed reactors (including jet mixers), simulated fluidized bed, rotary grate generators, shaft furnaces, stack furnaces or rotary tube reactors.

The porous catalyst can be arranged in the conversion reactor in any desired way so that the substances to be converted can pass through or over the catalyst. The contact of the liquid or vaporous starting materials with the porous catalyst can be effected in any suitable manner, for example by spraying liquid, cold or heated starting material or by passing a gas stream with gaseous or vaporous starting materials through the bed. In some cases, a solid starting material can be added directly to the heated catalyst or directly into the conversion reactor. The catalyst can also be added continuously or discontinuously. To inert the reaction space this should be rinsed in advance with a carrier gas. As a carrier gas is in particular an inert gas (such as nitrogen or carbon dioxide), water or steam or a CO / CO2 mixture into consideration. If the starting materials to be converted are already introduced into the conversion reactor in gaseous form, it is advisable to take them up in a gas stream of carrier gas and to transfer them into the reactor with it. Alternatively, however, the carrier gas can also be passed separately into the reactor. The inertization of the conversion reactor space is necessary since otherwise unwanted reactions of the catalyst occur at high temperatures (for example, it is possible to burn activated carbon used as a catalyst). For the purposes of this invention, a carrier gas is therefore understood as meaning a gas which serves to displace oxygen or other substances which lead to undesired reactions on the catalysts. The use of CO 2 or CO / CO 2 mixtures as carrier gas has the advantage that a separation step can be saved during product preparation, since CO 2 and CO are produced as splitting products of the conversion reaction anyway, while nitrogen as carrier gas must be separated from the product spectrum obtained.

The product gas stream obtained by contacting the starting material with the catalyst is finally fed to a separating device, such as a quencher. Here, the shorter-chain Ci- to C4-hydrocarbons can be separated from the longer-chain products. A separation of the liquid gas fraction from the natural gas-like fraction can be carried out by distillation or else by membrane separation processes or else by elevated pressure. Furthermore, the hydrocarbons contained in the liquid gas fraction and the natural gas-like fraction can also be isolated in pure form. Here too, distillative or membrane separation processes are suitable.

In a preferred embodiment, the proportion by weight of the gaseous hydrocarbons in the product gas stream is opposite over the liquid hydrocarbons 1.5 times, preferably 2 times, more preferably 3 times increased. The weight fraction of unreacted starting material present in the product gas stream is preferably at most 35 percent, more preferably at most 15 percent, and most preferably at most two percent, based on the proportion of gaseous hydrocarbons contained in the product gas stream.

If the olefin content in the product gas stream is too high, gas treatment may also be carried out before the separation step.

In this case, for example, a catalytic hydrogenation are used in the unsaturated hydrocarbons in the presence of externally added or incurred in the reaction hydrogen or in the shift reaction of CO and water vapor hydrogen produced (optionally in the presence of the hydrogenation catalysts required for this) are hydrogenated. The hydrogenation route can be connected downstream of the conversion reactor; it can also be arranged in the conversion reactor behind the region in which the conversion takes place. Alternatively, however, it is also possible to impregnate or dope the catalyst used for the conversion reaction with a suitable hydrogenation catalyst. Common hydrogenation catalysts are palladium or platinum; These can be applied in known manner in the form of solutions to the porous catalyst or added in the preparation of the porous catalyst.

Preferably, products of the 3rd gas family and products of the 2nd gas family according to "DVGW regulations, worksheet G260, gas quality 01/2000" and DIN 51622 should preferably be contained in the product gas stream.

An important application of the liquefied gas produced according to the invention is therefore the conditioning of natural gas substitutes. The firing properties of these natural gas substitutes to the natural gas quality required locally for the feed-in. can be adapted with liquefied gases. The liquefied gas produced by the process according to the invention (if appropriate also with Cl and C2 constituents still present as well as carrier gas) can therefore be admixed with biogas whose methane content is too high to be used as natural gas. Thus, from biogas (which may originate from fermentation processes, for example) and the liquefied gas obtained according to the invention, a natural gas can be produced in which all components are biogenic. Furthermore, the liquefied gas produced according to the invention for generating natural gas substitute (a liquefied petroleum gas mixture, which is also referred to as peak shaving gas) serve to cover consumption peaks in the public gas network.

The Cl and C2 fractions of the product mixture can also be used as substitutes for natural gas. This includes e.g. the thermal or motor use or the use as a vehicle fuel (CNG) both at the place of production and after feeding the natural gas-like gas mixture into the natural gas grid.

Without limiting the generality, the invention will be explained in more detail below on the basis of exemplary embodiments:

The following parameters are used:

Vibration density [g / l] according to DIN ISO 787, part 11

Iodz ahl [mgi _od / g _Akt ivkohie] (according to AWWA B 60 0 - 7 8 Powdered Act i - vated Carbon) specific surface area by means of BET determination according to DIN 66 131

Benzene loading [% by weight]

Pore sizes and adsorption pore volumes

To determine the bulk density, a coal bed is compacted under defined vibratory conditions (1250 strokes, drop height 3.0 mm) using a tamping volumeter in a 250 ml graduated cylinder. The investigated activated carbon forms are around activated carbon pellets with a diameter of 2 to 4 mm. In principle, activated carbon pellets or moldings can be used with a usual diameter of 1 - 6 mm.

The determination of the benzene loading is carried out by conversion from the Cyclohexanbeladung. Here, cyclohexane vapor-saturated air is mixed with pure air in different proportions; As a result, charge streams with different partial pressures are set. The loading of the activated carbon takes place in U-tubes, which are in a thermostated water bath. The activated carbon is with air, for example, to 9/10, 1/10 and 1/100 saturated with cyclohexane or loaded at the indicated concentration, at 20 ⁰ C to equilibrium or to constant weight. The loading takes place in the first step with the highest concentration at a partial pressure ratio of 0.9. Subsequently, the desorption takes place at a partial pressure ratio of 0.1 to constant weight. Another desorption step is carried out at a partial pressure ratio of 0.01.

The iodine value describes the amount of iodine [mg] which is adsorbed by 1 g activated carbon in the powdered state from 100 ml of a 0.1 N iodine solution (0.05 M 12) until a residual normality or final concentration of 0.02 N is reached.

From the total nitrogen loading, the adsorption pore volume is calculated. The distribution of pore sizes is calculated from the desorption isotherm using the BJH (Barrett, Joyner and Halenda) equation. In this connection, reference may be made to J. U. Kepler, R. Staudt, Gas Adsorption Equilibria, Experimental Meth ods and Adsorptive Isotherms, Springer, 2005.

example 1

As a starting material, for example, a mixture of vegetable and animal fat can be used. This will be after a first grease preheat that serves that To liquefy fat at 70 ⁰ C and reduce its viscosity so that it can be promoted via a pump in a defined flow rate in a second preheating, further heated to 180 ⁰ C. From the second preheating, the grease passes into an evaporator by means of an overflow, which ensures the maintenance of a constant volumetric flow. This can be designed, for example, as a bottom evaporator. In the evaporator, the fat is evaporated at 450 ⁰ C and combined with water vapor (which is preheated to the temperature prevailing in the conversion reactor) and nitrogen. The mixture of fat vapor, water vapor and nitrogen is then fed to a charcoal packed fixed bed reactor. On the activated carbon, the fats are converted into a mixture of hydrocarbons, which are condensed for analysis of the product mixture, separated by means of a gas chromatograph and analyzed by means of a mass spectrometer. In the process, "liquid product" (ie hydrocarbons with more than five carbon atoms) is separated from the liquid gas fraction and the gas-like fraction and can be burned, for example, to supply energy for the conversion process be returned to the process and replace the Stickstoffström in inert gas.

Example 2 - Conversion of used fat to activated carbon at 500 ° C.

Old fat (collected from the catering industry) is fed to a reactor charged with activated charcoal as described in Example 1. The conversion reaction is in a discontinuously operated conversion reactor to which 1 g of starting material is metered per minute, at 500 ⁰ C 1013 mbar, with a residence time of 3 seconds and at a feed stream to catalyst ratio of 0.45 gf _ee d * h ^{~ 1} per g kataiysator, operated.

The activated carbon type 1 is used as the activated carbon. It is a water activated activated carbon activated carbon on the basis of coconut shells with the following characteristics:

- specific surface 1109 m ² / g

Adsorption pore volume 0.436 cm ³ / g; - Volume-specific surface 525, 67 m ² / cm ³

- iodine value 1197 mg / g

- water content 2.65 wt .-%

- Vibration density 480 kg / m ³

- Bulk density 474 kg / m ³ - particle size 2.4 - 4.8 mm

- loading benzene at 20 ⁰ C (in each case is the concentration of benzene in g / m ³ and the associated load in% at a given measuring tolerance of +/- 2%): 288 g / m ³ - 35%; 32 g / m ³ - 32%; 3.2 g / m ³ - 28%; 1.6 g / m ³ - 26%; 0.3 g / m ³ - 22%

Pore radius distribution (in each case the pore diameter in nm and the corresponding proportion in% of the total pores are indicated): <6 nm - 56.1%; 6-8 nm - 4.9%; 8-10 nm - 3.6%; 10-12 nm - 3.6%; 12-16 nm - 4.1%; 16-20 nm - 3.6%; 20-80 nm - 19.6%; > 80 nm - 4.8%.

In such an implementation of the method, the product spectrum listed in Table 1 is formed. By "gas product" is meant any component whose boiling point at normal pressure is less than or equal to that of n-pentane. "Liquid product" means products having a higher boiling point. The product spectrum also includes the increase in mass of the activated carbon, since this must also have been produced by conversion of the starting materials. The liquid product formed in Example 2 is composed mainly of aromatic and polyaromatic compounds Table 1: Percentage of the various fractions in the total product.

Table 2 shows the composition of the gas product. In addition to CO and CO2 formed by decarboxylation and decarbonylation of the fatty acids, hydrogen and various hydrocarbons are also formed. The liquid gas fraction forms the largest proportion with about 22 wt .-%. Next arise about 10 wt .-% methane and 20 wt .-% C2 compounds.

Table 2: Composition of the "gaseous product"

Substance Share of product gas [wt%]

Methane 10,83

Ethan 17, 12

Ethen 3.2

Propane 15,44

Isobutane 6,54 n-pentane 5.1

CO 21, 62

CO2 9, 67 other substances (N2 -f- carbon-10,48 -hydrocarbons)

Example 3 - Conversion of waste fat in the presence of doped activated carbon

The conversion is carried out as described in Example 2. In contrast to this, activated carbon of type 2 (doped / impregnated activated carbon) contains alkaline doped active carbon. carbon or acid impregnated activated carbon used and the temperature in the catalyst bed is 450 - 460 ° C. Furthermore, work was carried out in Example 3 without the addition of water.

The alkaline doped activated carbon was obtained in this case, potassium carbonate and a Übergangsme ^¬ talloxid according to the method of WO 2007/137856 A2 were added currency ^¬ end of the manufacturing process the remaining starting materials of the activated carbon in the in the manufacturing process. It has the following properties: iodine number 1168 mg / g; Benzene loading: 0.9-36.45% by weight; 0.1-32.32% by weight; 0.01-17.02% by weight.

The acid impregnated activated carbon was obtained by impregnating a conventional steam-activated carbon with a phosphoric acid solution (impregnation was carried out by soaking and then drying the activated carbon). Here, activated apricot seeds were used (which activates ^¬ serdampf as Direktaktivat: no binder, no shaping) and HSPC ^ -imprägniert (7.7 wt .-% impregnation - Iodine Number prior to impregnation 1130 mg / g; iodine value after impregnation 785 mg / g).

In Table 3, the proportion of the products obtained is placed ^¬ leads.

Table 3: Share of the different fractions in the total product in percent by weight

Claims

claims

1. A process for the production of gaseous hydrocarbons, in particular of liquid gas and / or a natural gas-like gas mixture or one or more components contained in the liquid gas or in the natural gas-like gas mixture, from a starting material containing or consisting of oxygen-containing hydrocarbons, comprising the following steps:

- Provision of the starting material - contacting the starting material in the absence of oxygen at a temperature of 300-850 ⁰ C in a conversion reactor with a porous catalyst, so that a hydrocarbon-containing product gas mixture is formed in which the weight fraction of gaseous hydrocarbons is greater than the liquid hydrocarbons,

- Collecting the hydrocarbon-containing product gas stream and supplying the product gas stream to a separating, in which a product separation takes place.

2. The method according to any one of the preceding claims, wherein the liquefied petroleum gas is a hydrocarbon mixture whose hydrocarbons are selected from the group consisting of propane, propene, butane, butene, isobutane and isobutene and mixtures thereof.

3. The method of claim 1 or 2, wherein the natural gas-like gas mixture consists of methane and / or ethane and / or ethene or contains these substances or a mixture of these substances.

4. The method according to any one of the preceding claims, wherein the feed stream to catalyst ratio is 0.1 to 1, preferably 0.2 to 0.5 gfeed * h ^{~ 1} per gκataiysator and the process is carried out batchwise.

5. A method according to the preceding claim, wherein the starting material is selected from the group consisting from fats, oils, fatty acids, fatty acid esters, tall oils, monoglycerides, diglycerides and polyols, and mixtures thereof.

6. The method according to any one of the preceding claims, wherein the porous catalyst is selected from the group consisting of activated carbon, carbon molecular sieves, activated coke, carbon nanotubes, mixtures thereof or mixtures of these substances with perovskites and / or zinc chloride.

7. The method according to any one of the preceding claims, wherein the porous catalyst contains mesopores and / or micropores.

8. The method according to any one of claims 5 to 7, wherein the porous catalyst is doped with a second catalyst and / or impregnated.

9. The method according to any one of claims 5 to 7, wherein the porous catalyst is doped with a basic component and / or impregnated.

10. The method according to any one of the preceding claims, wherein the starting material is supplied before contacting with the porous catalyst of an evaporation device.

11. A process according to the preceding claim, wherein reactions take place in the evaporation device in which at least part of the starting material is decomposed.

12. The method according to any one of the preceding claims, wherein the contacting of the starting material with the porous catalyst takes place in the presence of water and / or a water-releasing material.

13. A process as claimed in the preceding claim, wherein the water or water-releasing material used is added to the inert gas stream and / or added to the starting material and / or vaporized into the conversion reactor. is passed and / or contained in the starting material.

14. The method according to any one of the preceding claims, wherein the weight fraction of the gaseous hydrocarbons in the product gas stream is at least 1.5 times, preferably 2 times, more preferably 3 times higher than the proportion of liquid hydrocarbons.

15. The method according to any one of the preceding claims, wherein the weight fraction of unreacted starting material in the product gas stream is at most 35%, preferably at most 15%, more preferably at most 2% of the proportion of gaseous hydrocarbons.

16. The method according to any one of the preceding claims, wherein the unreacted starting material and / or contained in the product gas stream, liquid under normal conditions wholly or partly the starting material or the conversion or vertierungsreaktor during a process step or a mass transfer step, prior to the conversion reaction in the conversion reactor takes place, be supplied.