Continuous process for the production of alkanes

Abstract

Continuous reductive dehydroxymethylation process for the production of alkanes from primary aliphatic alcohols having 3 to 25 carbon atoms in a reactor in the presence of hydrogen and a catalyst at a pressure of ≥ 2 bar, characterized in that the dehydroxymethylation is carried out in the gas phase.

Description

[0001] This invention relates to a continuous reductive dehydroxymethylation method for preparing alkanes from primary aliphatic alcohols having 3-25 carbon atoms in a reactor in the presence of hydrogen and a catalyst. Existing technology

[0002] Alkanes can be used, for example, in decorative cosmetics and care formulations, as taught in WO 2007 / 068371A1 (BASFSE).

[0003] WO 2007 / 068371A1 (BASF SE) also describes a method for preparing hydrocarbons from fatty alcohols by reductive dehydroxymethylation in the liquid phase (see Example 2). No mention is made of conducting the reaction in the gas phase.

[0004] DE 10 2010 033 523A1 (Saltigo GmbH) teaches a method for preparing straight-chain saturated alkanes from primary straight-chain alcohols of the formula R-OH, wherein R represents a straight-chain saturated linear alkyl group having 8-24 carbon atoms, comprising dehydroxymethylation of the primary alcohol in the presence of a ruthenium catalyst and hydrogen, at a pressure of 50-150 bar and a temperature of 150-250 °C. The dehydroxymethylation is carried out in the liquid phase (see Examples 1 and 2). No mention is made of carrying out the reaction in the gas phase.

[0005] Helvetica Chimica Acta, Vol. 60, Fasc. 8 (1977), No. 290, teaches a one-step catalytic procedure for the cleavage of C(1), C(2) bonds of long-chain aliphatic alcohols using undecanoyl alcohol or dodecanoyl alcohol as examples in a continuous flow tubular reactor with a Ni / Cu catalyst. The paper does not mention whether the reaction takes place in the gas phase or the liquid phase, nor does it specify the reaction pressure.

[0006] Elmer J. Badin, in his article entitled "Catalytic Dehydrogenation I. Catalytic Conversion of Alcohols into Aldehydes, Paraffins and Olefins", Journal of the American Chemical Society, Vol. 65, No. 10, 1943, pp. 1809-1813, describes the catalytic dehydrogenation of aliphatic alcohols. The method, carried out in the liquid phase at atmospheric pressure, yields only very low yields of alkanes.

[0007] Large-scale operation in the liquid phase poses safety risks due to its highly exothermic nature. This risk can be mitigated by operating massive liquid recirculation flows, which makes the method technically more demanding and therefore less economically viable.

[0008] As described in the article by Hermann Pines and T.P. Kobylinski entitled "Hydrogenolysis of Alcohols", Journal of Catalysis 17, 375-383 (1970), neopentyl alcohol can be converted to isobutane, in particular. The reaction of butanol to propane in the presence of a nickel catalyst under a hydrogen atmosphere is also described. However, the major product is the corresponding ether. The use of long-chain fatty alcohols in such reactions is not mentioned. The reactions are carried out in the gas phase, but only at atmospheric pressure, and not on an industrial scale, but rather on a "micro" scale.

[0009] W.M.A., I. This, and P. Schleyer also described the reductive dehydroxymethylation of primary organic alcohols in their article entitled “Direct Reduction of Alcohols to Hydrocarbons,” Zeitschrift für Naturforschung, Part B, 1982, 37B(3). No long-chain fatty alcohols were disclosed or suggested as suitable precipitates. The reactions were carried out in the gas phase, but only at atmospheric pressure, and not on an industrial scale, but only on a “micro” scale.

[0010] GB 1051826 describes a method for preparing a primary monohydric alcohol by removing hydroxymethyl from a dihydric alcohol using a nickel catalyst under a hydrogen atmosphere. According to the embodiments provided in this application, the reaction is carried out in the liquid phase. There is no mention of carrying out the reaction in the gas phase.

[0011] Technical issues

[0012] The technical problem to be solved by this invention is to improve existing methods for preparing alkanes from corresponding primary alcohols and to overcome one or more of the shortcomings of the prior art, especially the aforementioned shortcomings. It is intended to find a method that can be implemented with high conversion, high yield (including space-time yield), and selectivity. Furthermore, it is intended to find a method with low safety risks.

[0013] Surprisingly, the aforementioned technical problem has been found to be solved by a continuous reduction dehydroxymethylation method for preparing alkanes from primary aliphatic alcohols having 3-25 carbon atoms in a reactor in the presence of hydrogen and a catalyst at a pressure of ≥2 bar, characterized in that the dehydroxymethylation is carried out in the gas phase.

[0014] Unless otherwise expressly stated, any reference to pressure in the context of this invention refers to absolute pressure.

[0015] Surprisingly, implementing this method at pressures ≥2 bar resulted in increased selectivity, as no corresponding hints exist in the art. According to the aforementioned cited article by WFMaier et al., the highest pressure for dehydroxymethylation taught in the art is 1 bar.

[0016] Implementing this method in the gas phase reduces safety risks. Surprisingly, long-chain primary alcohols with fairly high boiling points can evaporate even at high concentrations under pressures of ≥2 bar, which is not mentioned in the art. As stated in the preceding paragraph, the highest pressure taught in the art is 1 bar.

[0017] When the reaction is carried out in the liquid phase, a liquid recirculation flow is required to demonstrate that the reaction is highly exothermic. When the reaction is carried out in the gas phase, this liquid recirculation flow is not required. For the gas-phase method of this invention, the liquid retention of the corresponding alcohol in the reactor is much smaller than in the liquid-phase method. It can also be operated at lower pressures compared to the pressures typically used in the liquid phase. Therefore, the risks of thermal explosion, reactor rupture, and release of flammable products are much lower. Thus, the safety risks are lower compared to operating the method in the liquid phase. Invention Details

[0019] It is not intended that the invention be bound by any theory or limited in any way. It is believed that reductive dehydroxymethylation is carried out as follows (shown as an example using dodecane-1-ol):

[0020]

[0021] In the first step, the alcohol is dehydrogenated. The resulting aldehyde is then decarbonylated to give the desired alkane.

[0022] It is generally advantageous to hydrogenate the carbon monoxide produced by reductive dehydroxymethylation to methane.

[0023] Methanation is believed to proceed as follows:

[0024]

[0025] The resulting water evaporates and does not adversely affect the reductive dehydroxymethylation process. Therefore, no specific measures are needed to remove it from the reaction mixture.

[0026] Therefore, the CO content in the reactor is quite low. Thus, catalyst lifetime can be extended by preventing CO poisoning. This is particularly advantageous when the method is operated in recirculating gas mode. Operating the method in recirculating gas mode without converting carbon monoxide to methane would lead to rapid CO accumulation in the reactor, thus posing a risk of rapid catalyst poisoning. Therefore, when carbon monoxide is converted to methane, the catalyst lifetime of the method operating in recirculating gas mode can be significantly increased.

[0027] Given the low CO content in the reactor, a catalyst capable of catalyzing both the reductive dehydroxymethylation of primary alcohols and the hydrogenation of carbon monoxide (CO) produced by reductive dehydroxymethylation to methane (CH4) is preferred. In principle, this can be any catalyst with strong hydrogenation activity, such as those containing platinum, palladium, ruthenium, or nickel. A nickel-containing catalyst is preferred. The catalyst preferably contains ≥10% by weight, particularly ≥20% by weight, more particularly 30-90% by weight, and very particularly 40-80% by weight of Ni.

[0028] The composition of the catalyst (in weight percent) is based on the total mass of the catalyst.

[0029] The Ni catalyst can also be a supported catalyst. Preferably, it contains 20-80 wt% Ni and 20-80 wt% support, particularly 30-80 wt% Ni and 20-70 wt% support, more particularly 40-80 wt% Ni and 20-60 wt% support, and very particularly 50-80 wt% Ni and 20-50 wt% support.

[0030] Preferably, the amounts of Ni and support in each catalyst are 80-100% by weight, particularly 90-100% by weight, even more particularly 95-100% by weight, and very particularly 97-100% by weight.

[0031] Preferably, the support is Al2O3 or SiO2 or a mixture of the two, with SiO2 being particularly preferred.

[0032] Given the low CO content in the reactor, reductive dehydroxymethylation can also be carried out in a first reactor containing a first catalyst, and the resulting CO can be methanated in a second reactor containing a second catalyst. The first catalyst can be any catalyst with sufficient catalytic activity for reductive dehydroxymethylation but not sufficient catalytic activity for methanation. The second catalyst can be any catalyst with sufficiently strong hydrogenation activity to catalyze the hydrogenation of carbon monoxide (CO) produced by reductive dehydroxymethylation to methane (CH4).

[0033] The first catalyst may be, for example, a copper-containing catalyst. The second catalyst may be, for example, a catalyst containing platinum, ruthenium, palladium, or nickel. Preferably, any of the above-mentioned nickel catalysts.

[0034] If the reaction is carried out in a recirculating gas mode (as further outlined below), a catalyst capable of catalyzing both processes can be used, i.e., the reductive dehydroxymethylation of the primary alcohol and the hydrogenation of carbon monoxide (CO) produced by the reductive dehydroxymethylation to methane (CH4) (Alternative 1); or the reductive dehydroxymethylation can be carried out in a first reactor containing a first catalyst, and the resulting CO can be methanated in a second reactor containing a second catalyst. In Alternative 2, the gas is recirculated after the CO is converted to methane in the second reactor. Otherwise, the CO is recirculated back to the first reactor, where rapid catalyst deactivation may occur due to CO poisoning. Alternative 1 is preferred.

[0035] For any alternative, all preferred features described herein, including but not limited to those relating to pressure, temperature, catalyst hourly space velocity, feedstock (alcohol), and the molar ratio of hydrogen to alcohol, are also preferred. Unless otherwise expressly stated, in the case of Alternative 2, all corresponding preferred features pertain to both reaction steps, namely reductive dehydroxymethylation and methanation.

[0036] The above teachings should not be construed in any way as a limitation on the number of reactors used in the two alternatives. For example, for Alternative 1, more than one reactor may be used, each equipped with a corresponding catalyst that catalyzes reductive dehydroxymethylation and methanation. The operating conditions of each reactor may differ, particularly the temperature, which may vary significantly. For Alternative 2, reductive dehydroxymethylation may be carried out in multiple reactors equipped with corresponding catalysts, for example. Similarly, methanation may also be performed using multiple reactors equipped with corresponding catalysts. Likewise, the operating conditions of reactors packed with different catalysts may differ.

[0037] The method of the present invention can be carried out at pressures of 2-50 bar, particularly 5-40 bar, more particularly 8-35 bar, and very particularly 11-25 bar. Pressures above 50 bar are less preferred because operating the method at such high pressures does not significantly increase selectivity, but requires increased technical effort.

[0038] The preferred reaction temperature is 100-350℃, particularly 150-300℃, even more particularly 200-280℃, and very particularly 210-260℃.

[0039] This method can be carried out in an isothermal or adiabatic manner. Isothermal operation can be achieved, for example, by removing the enthalpy of reaction released during the reaction in one or more reactors using appropriate internal or external cooling equipment. In the context of this invention, substantially isothermal conditions should be understood as a temperature rise along the reactor axis not exceeding 6°C, preferably not exceeding 3°C. The temperature difference is determined by the temperature at the reactor outlet and the temperature at the reactor inlet.

[0040] Depending on the reactor's operating conditions, it can be switched from a pure isothermal operating mode (with the aforementioned temperature rise) to an adiabatic operating mode, where the temperature rise in the reactor can, for example, be as high as 50°C.

[0041] In adiabatic operation, the released enthalpy of reaction is not removed but retained in the reaction mixture. When the reaction takes place in one or more fixed-bed reactors, depending on the reaction conditions used, the adiabatic process mode results in the reaction mixture temperature rising by 50°C or higher during its passage through the reactor. To control and monitor the temperature of one or more reactors, multiple measuring points / (thermometer sleeves) can be installed within them.

[0042] Dehydroxymethylation in the gas phase is preferably achieved by evaporating the alcohol in a hydrogen-containing gas stream and feeding it into the reactor in gaseous form. Unless otherwise explicitly stated, hydrogen refers to molecular hydrogen (H2). The hydrogen-containing gas stream is used for evaporation of the alcohol. Furthermore, the hydrogen contained therein serves as a reactant. For evaporation of the alcohol, the flow rate of the hydrogen-containing gas stream is preferably 250-60000 L / min. s The catalyst volume is 480-53000 Ls / L catalyst·h, more preferably 1200-45000 Ls / L catalyst·h. Ls refers to the volume under standard conditions (p = 1 atm, T = 0°C), and the unit is liters.

[0043] Evaporation can be carried out, for example, in a liquid-feed evaporator, a heating coil, or a cross-flow heating device.

[0044] The hydrogen-containing gas stream can consist essentially of hydrogen. Preferably, it contains 95-100% by volume, particularly 97-99.5% by volume of hydrogen. The composition (volume %) is based on the total volume of all gaseous components. In these embodiments, the method is not operated in a recirculated gas mode.

[0045] Preferably, the method operates in a recirculated gas mode. A recirculated gas mode truly means continuously recirculating gas back to the reactor.

[0046] The recirculated airflow velocity can be 200-50000L. s / L catalyst·h, preferably 400-45000L s / L catalyst·h, more preferably 1000-40000L s / L catalyst·hour

[0047] In the context of this invention, recirculated gas refers to a gas stream that is recycled back into the reactor before the addition of fresh hydrogen and before the evaporation of alcohol. The recirculated gas can be used for evaporating alcohol. In these embodiments, the recirculated gas constitutes a hydrogen-containing gas stream. Alternatively, the recirculated gas can be combined with fresh hydrogen, and the combined stream can be used to evaporate alcohol. In these embodiments, the recirculated gas, together with the fresh hydrogen stream, constitutes a hydrogen-containing gas stream.

[0048] Most preferably, the method operates in a recirculating gas mode, whereby, after the alkanes and water condense from the reaction mixture, a portion of the resulting gaseous effluent is discharged, and the remainder is recycled back into the reactor as a recirculating gas stream, thereby continuously feeding a fresh hydrogen stream into the method, and thus the recirculating gas stream alone, or the recirculating gas stream together with the fresh hydrogen stream, constitutes a hydrogen-containing gas stream for evaporating the alcohol. Preferably, the recirculating gas stream together with the fresh hydrogen stream constitutes a hydrogen-containing gas stream. Partially discharging the generated gaseous effluent is advantageous because if fresh hydrogen is continuously added, the total gas stream to be treated will continuously increase. At some point, it will be technically impossible to process the amount of gas to be treated.

[0049] Figure 1 The possible configurations for the recirculated gas mode are further illustrated. When fresh hydrogen is added via lines 3a, 3b, or 3c, the recirculated gas flow, together with the fresh hydrogen flow, constitutes the hydrogen-containing gas flow for evaporating the alcohol. When fresh hydrogen is added via line 3d, the recirculated gas flow constitutes the hydrogen-containing gas flow for evaporating the alcohol independently.

[0050] The recirculated airflow velocity can be 200-50000L. s / L catalyst·h, preferably 400-45000L s / L catalyst·h, more preferably 1000-40000L s / L catalyst·h; the flow rate of fresh hydrogen gas can be 50-1000L / h. s / L catalyst·h, preferably 80-8000L s The catalyst per liter per hour is more preferably 200-5000 L / h. s / L catalyst·hour. Ls refers to the volume under standard conditions (p = 1 atm, T = 0°C), in liters. Preferably, the amount of fresh hydrogen is adjusted to match the amount of alcohol supplied to the catalyst, with a minimum molar ratio of 2:1, to ensure complete hydrogenation of CO to methane.

[0051] Preferably, the recirculated gas stream may have the following composition: 5-90 vol% hydrogen, 5-90 wt% methane, and equal to or less than 5 vol% other compounds; preferably 10-90 vol% hydrogen, 10-90 wt% methane, and less than 2 vol%, particularly less than 1 vol% other compounds. The composition (volume %) is based on the total volume of all gaseous components under standard conditions (p = 1 atm, T = 0°C). The composition of the recirculated gas can be analyzed by gas chromatography (gas chromatography on a molecular sieve as the stationary phase, thermal conductivity detection, and external standard quantification).

[0052] Other compounds include molecular oxygen, molecular nitrogen, and low-boiling-point alkanes such as ethane, propane, or n-butane. The CO content is typically less than 0.1% by volume, preferably less than 0.05% by volume, or even less than 0.03% by volume.

[0053] The fresh hydrogen stream typically consists essentially of hydrogen. Preferably, it contains 95-100% by weight, particularly 97-99.5% by weight of hydrogen. The composition (wt%) is based on the total mass of all gaseous components.

[0054] Preferably, the molar ratio of hydrogen to alcohol is 2-400, particularly 6-200, more particularly 7-50, very particularly 8-30, or even 6-20, 7-15 or 8-10.

[0055] When this method operates in recirculated gas mode, the molar ratio refers to the molar ratio of fresh hydrogen to alcohol. Because hydrogen is present in the recirculated gas, the effective molar ratio in the reactor can be higher. The effective molar ratio refers to the molar ratio of hydrogen to alcohol, taking into account the amount of hydrogen in both the fresh and recirculated hydrogen streams. The amount of hydrogen in the recirculated gas can be analyzed, for example, by gas chromatography as described above.

[0056] The effective molar ratio of hydrogen to alcohol can be 2-500, particularly 20-300, more particularly 40-200, and very particularly 60-100. These ranges can be achieved when the recirculated gas flow has any of the above-mentioned preferred flow rates and the molar ratio of hydrogen to alcohol is selected according to the above-mentioned preferred ranges.

[0057] This method is carried out in one or more suitable reactors. The preferred reactor is a tubular reactor. Examples of suitable reactors with a recirculating gas flow can be found in Ullmann's Encyclopedia of Industrial Chemistry, 5th edition, Volume B4, pp. 199-238, "Fixed-Bed Reactors". Alternatively, reductive dehydroxymethylation is advantageously carried out in a bundled tubular reactor or a single-feed unit. In a single-feed unit, the tubular reactor in which the reaction takes place can consist of multiple (e.g., two or three) individual tubular reactors connected in series.

[0058] Catalysts are typically used in the form of catalyst molded articles; for example, tablets, balls, rings, extrusions (e.g., wires). The catalyst is preferably arranged as a fixed bed in the reactor. Flow can be from the top or from the bottom toward the fixed catalyst bed.

[0059] When the catalyst is arranged in a fixed bed, mixing the catalyst with inert packing material to "dilute" the catalyst may improve the selectivity of the reaction. The packing material ratio in the catalyst formulation can be 20-80% by volume, particularly 30-60% by volume, and especially 40-50% by volume.

[0060] The mass hourly space velocity is 0.05-2 kg alcohol / L catalyst (bed volume)·h, preferably 0.1-1 kg alcohol / L catalyst (bed volume)·h, more preferably 0.15-0.8 alcohol / L catalyst (bed volume)·h, or even 0.2-0.65 kg alcohol / L catalyst (bed volume)·h.

[0061] This method is typically carried out in a manner that results in an alcohol conversion rate of 80-100%, particularly 90-100%, even more particularly 95-100%, and very particularly 98-100%.

[0062] The method of this invention is suitable for the reaction of primary aliphatic alcohols having 3-25, preferably 8-24, carbon atoms. In the context of this invention, primary aliphatic alcohols are also referred to as "primary alcohols" or "alcohols". The term "aliphatic" should refer to any functionalized or non-functionalized organic residue that does not contain an aromatic ring system. It may have any functional group.

[0063] Primary alcohols can be fatty alcohols having 8-24 carbon atoms. They can be prepared in known ways from renewable feedstocks such as coconut oil, palm oil, or palm kernel oil, for example by transesterification with methanol or by saponification with a strong base (such as KOH or NaOH) or acid followed by hydrogenation. In addition to pure fatty alcohols, other straight-chain or branched, mono- or poly-alcohols, mixtures of alcohols, or derived alcohols having 3-25, preferably 8-24 carbon atoms, prepared on an industrial scale, can also be used in principle, and these are preferred. The use of fatty alcohols with an even number of carbon atoms is particularly preferred because otherwise, odd-numbered alkanes are difficult to prepare.

[0064] Preferably, the alcohol is a fatty alcohol having the general formula R-CH2-OH, wherein R is C7-C. 23 Alkyl groups, especially C7-C 17 Alkyl groups, especially C9-C 15 Alkyl, very specifically C 11 -C 15 alkyl.

[0065] In a preferred embodiment, the alcohol is a straight-chain fatty alcohol. Therefore, in the above general formula, R is a straight-chain C7-C... 23 Alkyl groups, especially straight-chain C7-C 17 Alkyl groups, more particularly straight-chain C9-C 15 Alkyl groups, very specifically straight-chain C 11 -C 15 alkyl.

[0066] For the same reasons mentioned above, it is preferred to use the corresponding fatty alcohol having an even number of carbon atoms. Therefore, it is preferable that the alcohol is a fatty alcohol having the general formula R-CH2-OH, wherein R is C7, C9, C6, C7, C8, C9 ... 11 C 13 C 15 C 17 C 19 C 21 C 23 Alkyl groups, especially C7, C9, C6 11 C 13 C 15 C 17 Alkyl groups, especially C9 and C6 groups. 11 C 13 C 15 Alkyl, very specifically C 11 C 13 C 15 alkyl.

[0067] Among these fatty alcohols having an even number of carbon atoms, those with straight chains are particularly preferred. Therefore, preferably, the alcohol is a fatty alcohol having the general formula R-CH2-OH, wherein R is a straight-chain C7, C9, C2, C3, C4, C5, C6, C7, C9 ...11 C 13 C 15 C 17 C 19 C 21 C 23 Alkyl groups, especially straight-chain C7, C9, C6... 11 C 13 C 15 C 17 Alkyl groups, especially straight-chain C9 and C16 groups. 11 C 13 C 15 Alkyl groups, very specifically straight-chain C 11 C 13 C 15 alkyl.

[0068] A mixture of any of the primary alcohols mentioned above may also be used.

[0069] In a highly preferred embodiment, the method of the present invention is used to prepare undecane and tridecane by reductive dehydroxymethylation of dodecane-1-ol and tetradecane-1-ol.

[0070] The alkanes prepared according to the present invention can be used to prepare cosmetic formulations, such as shampoos, hair lotions, foam baths, shower gels, creams, gels, emulsions, alcohols and water / alcohol solutions, wax / fatty compounds, stick formulations, powders, and pastes. These formulations may contain, as other adjuvants and additives, mild surfactants, oil components, emulsifiers, pearlescent waxes, consistency factors, thickeners, fatliquoring agents, stabilizers, polymers, polysiloxane compounds, fats, waxes, lecithin, phospholipids, biological agents, UV protection factors, antioxidants, deodorants, antiperspirants, dandruff removers, film-forming agents, swelling agents, insect repellents, self-tanning agents, tyrosine inhibitors (bleaching agents), water-soluble growth promoters, solubilizers, preservatives, fragrance oils, dyes, etc. Alkanes are preferably used as oil components.

[0071] This invention allows for the preparation of alkanes with specific chain lengths as individual components in cosmetic formulations, serving as so-called lightweight emollients, or even their mixing in specific ways to achieve particular properties, such as spreading behavior, volatility, or even flash point. More specifically, the possibility of mixing alkanes based on a building block principle offers a significant advantage over alkanes from petrochemical sources (which exist almost entirely as complex mixtures of branched and unbranched hydrocarbons). In these cases, further post-processing via distillation requires considerable effort or risks undesirable isomer residues in the product. Furthermore, toxicological assessments of a given hydrocarbon or mixture of given hydrocarbons are much simpler and safer, which is particularly important for cosmetic applications.

[0072] Therefore, the present invention also relates to a method for preparing a cosmetic formulation, characterized in that one or more alkanes are prepared according to any one of the preceding claims, and the resulting one or more alkanes are mixed with one or more other compounds to obtain a cosmetic formulation.

[0073] Figure 1 The preferred embodiment is shown. The alcohol is supplied to the saturator (4) via line (1) and recirculated gas via line (2). The recirculated gas is passed through compressor (11) to increase its pressure to the required reaction pressure. Fresh hydrogen can be supplied directly to the saturator (4) via line (3a) or to the recirculated gas via line (3b). Alternatively, it can be supplied to the recirculated gas and then passed through compressor (11). This is advantageous because the hydrogen stream has a higher pressure than the recirculated gas, thus reducing the energy required for the compressor. Hydrogen can also be supplied directly to the reactor via line (3d). Theoretically, it is also possible to combine these methods to add hydrogen (i.e., (3a) to (3d)). The alcohol is evaporated in the saturator (4), and the resulting gas stream is supplied to the reactor (6) via line (5). The reaction mixture is passed through a heat exchanger (8) and optionally via line (7) through a cryostat, where it is cooled and fed into a high-pressure separator (9), where a gaseous effluent consisting mainly of hydrogen and methane is discharged. The gaseous effluent is partially discharged via line (10). The residue is recycled as a recirculation stream to a saturator (4) via line (2). The crude reaction product from the high-pressure separator (9) is fed via line (12) into a low-pressure separator (13), where it is further degassed. The resulting gas stream, consisting mainly of hydrogen and methane, is discharged via line (15). The crude reaction product, particularly the high-value alkanes and high-boiling compounds, is removed from the low-pressure separator (13) via line (14). The crude alkane product can be further purified.

[0074] The following examples are for illustrative purposes only and should not be construed as limiting the invention in any way. Example

[0075] The experiment was conducted in a continuous flow (top-down) gas-phase reactor. The reactor consisted of a 2.1 m double-walled oil-heated tube with an inner diameter of 4.11 cm. From bottom to top, the tube was filled with 40 ml of ceramic rings (2.5–3.5 mm in diameter), 0.5 L of catalyst (60 wt% nickel on 40 wt% SiO2, BASF SE), and 1.8 L of ceramic rings (2.5–3.5 mm in diameter). After filling, nitrogen was replaced with hydrogen and the gas was cooled in 200 L of [gas flow rate missing]. S The catalyst is activated by heating it to 280°C (circulating oil temperature) for 24 hours under standard conditions (p = 1 atm, T = 0°C).

[0076] The feed of supplemental hydrogen, recirculated gas, and mixed alcohols is heated to the desired temperature and fed into the liquid feed evaporator. The oil thermostat of the double-walled reactor tubes is set to the desired reactor temperature. The reactor output is first cooled with cooling water using two heat exchangers, then cooled to 10°C using a cryostat and fed into the high-pressure separator. Liquid and gas phase separation occurs there. The liquid phase is depressurized to a low-pressure separator maintained at 30°C; the remaining gaseous components are discharged from this separator to a flare, and the liquid is discharged into a collection container for use as the crude reactor output. The gas phase from the high-pressure separator is recirculated in a specified amount via a gas compressor and used as the carrier gas for the feed. Excess gas is discharged into the flare for combustion via a pressure control valve. The conversion and selectivity of the crude output are determined by gas chromatography.

[0077] Both the liquid feed evaporator and reactor were set to 230°C. A 300L... S / h Freshly replenished H2 (corresponding to 600L) S / L catalyst·hour) and approximately 40,000L S / h recirculated gas (corresponding to 8000L) S A mixture of 0.3 kg / h catalyst ( / L catalyst·h) and 0.3 kg / h mixed fatty alcohols was fed into the reactor. The mixed fatty alcohols were a mixture of approximately 72 wt% dodecyl alcohol and 26 wt% tetradecyl alcohol (containing approximately 2 wt% other alcohols). The mixed fatty alcohols used in these experiments were obtained by hydrogenating a corresponding mixture of lauric acid and myristic acid derived from palm kernel oil and coconut oil. The palm kernel oil was sourced from Indonesia, Malaysia, and Colombia. The coconut oil was sourced from Indonesia and the Philippines. Pressure was varied as described in Table 1. Table 1 shows the output composition, including conversion and selectivity.

[0078] Discussion of Results:

[0079] Figure 2 Based on entries 1-3 of the table above, the selectivity dependence related to reaction pressure was visualized. Selectivity decreases as reaction pressure decreases. Therefore, pressures below 2 bar result in lower selectivity than those at 2 bar and higher pressures.

[0080] Table 1—Results

[0081]

[0082] Loading rate: catalyst hourly space velocity, in kg alcohol / L catalyst (bed volume)·hour.

[0083] MR: Molar ratio of fresh H2 to mixed fatty alcohols

[0084] RG: Recirculated Gas

[0085] Conversion rate: Conversion rate of mixed lipid alcohols

[0086] Selectivity: Valuable products include undecane (C11) and tridecane (C20). 13 Selectivity of )

Claims

1. A continuous reductive dehydroxymethylation process for the preparation of alkanes from primary aliphatic alcohols in a reactor in the presence of hydrogen and a catalyst at a pressure of 11-25 bar, characterized in that The dehydroxymethylation is carried out in the gas phase, wherein the alcohol is a fatty alcohol having the general formula R-CH2-OH, wherein R is C7-C 23 alkyl, wherein the process is operated in a recycle gas mode, wherein after condensation of the alkane and water from the reaction mixture, the gaseous effluent produced is partially withdrawn and the remainder is recycled to the reactor as a recycle gas stream, wherein a fresh hydrogen stream is continuously fed to the process, and wherein the separate recycle gas stream or the recycle gas stream together with the fresh hydrogen stream constitutes the hydrogen-containing stream for vaporizing the alcohol, and wherein the catalyst comprises > 10 wt% Ni.

2. The method of claim 1, wherein R is C7-C 17 alkyl.

3. The method of claim 2, wherein R is C9-C 15 alkyl.

4. The method of claim 3, wherein R is C 11 -C 15 alkyl.

5. The method of claim 2, wherein The alcohol is a linear aliphatic alcohol.

6. The method according to any one of claims 1-5, characterized by The process is carried out at a pressure of 11 to 20 bar.

7. The method of claim 2, wherein The process is operated in a recycle gas mode.

8. The method of claim 6, wherein The flow rate of the recycle gas stream is 200-50000 L s per liter of catalyst per hour.

9. The method of claim 8, wherein The flow rate of the recycle gas stream is 400-45000 L s per liter of catalyst per hour.

10. The method of claim 9, wherein The flow rate of the recycle gas stream is 1000-40000 L s per liter of catalyst per hour.

11. The method of any one of claims 1-5, wherein The catalyst hourly space velocity is 0.05 to 2 kg alcohol per liter catalyst (bed volume) per hour.

12. The method of claim 11, wherein The catalyst hourly space velocity is 0.1 to 1 kg alcohol per liter catalyst (bed volume) per hour.

13. The method of claim 12, wherein The catalyst hourly space velocity is 0.15 to 0.8 kg alcohol per liter catalyst (bed volume) per hour.

14. The method of claim 2, wherein The catalyst hourly space velocity is 0.05 to 2 kg alcohol per liter catalyst (bed volume) per hour.

15. The method of claim 1, wherein The recycle gas stream has the following composition: 5 to 90 vol% hydrogen, 5 to 90 wt% methane and equal to or less than 5 vol% other compounds.

16. The method of claim 15, wherein The recycle gas stream has the following composition: 10 to 90 vol% hydrogen, 10 to 90 wt% methane and less than 2 vol% other compounds.

17. The method of claim 16, wherein The recycle gas stream has the following composition: 10 to 90 vol% hydrogen, 10 to 90 wt% methane and less than 1 vol% other compounds.

18. The method of claim 8, wherein The recycle gas stream has the following composition: 5 to 90 vol% hydrogen, 5 to 90 wt% methane and equal to or less than 5 vol% other compounds.

19. The method of claim 11, wherein The recycle gas stream has the following composition: 5 to 90 vol% hydrogen, 5 to 90 wt% methane and equal to or less than 5 vol% other compounds.

20. The process according to claim 1, wherein the catalyst comprises > 20 wt% Ni.

21. The process according to claim 20, wherein the catalyst comprises 30 to 90 wt% Ni.

22. The process according to claim 21, wherein the catalyst comprises 40 to 80 wt% Ni.

23. The method of claim 1, wherein The catalyst is a supported catalyst containing 20 to 80 wt% Ni and 20 to 80% of a support.

24. The method of claim 23, wherein The catalyst is a supported catalyst containing 30 to 80 wt% Ni and 20 to 70 wt% of a support.

25. The method of claim 24, wherein The catalyst is a supported catalyst containing 40 to 80 wt% Ni and 20 to 60 wt% of a support.

26. The method of claim 25, wherein The catalyst is a supported catalyst containing 50 to 80 wt% Ni and 20 to 50 wt% of a support.

27. The method of claim 23, wherein The support is AI2O3 or SiO2 or a mixture of both.

28. The method of claim 27, wherein The support is SiO2.

29. The method of any one of claims 1-5, wherein The molar ratio of hydrogen to alcohol is 2 to 400.

30. The method of claim 29, wherein The molar ratio of hydrogen to alcohol is 6 to 200.

31. The method of claim 30, wherein The molar ratio of hydrogen to alcohol is 7 to 50.

32. The method of claim 31, wherein The molar ratio of hydrogen to alcohol is 8 to 30.

33. The method of claim 29, wherein The molar ratio of hydrogen to alcohol is 6 to 20.

34. The method of claim 33, wherein The molar ratio of hydrogen to alcohol is 7 to 15.

35. The method of claim 34, wherein The molar ratio of hydrogen to alcohol is 8 to 10.

36. The method according to any one of claims 1-5 for the preparation of undecane and tridecane by reductive dehydroxymethylation of dodecan-1-ol and tetradecan-1-ol.

37. A method of preparing a cosmetic formulation, characterized in that producing one or more alkanes according to any one of claims 1-36 and mixing the resulting one or more alkanes with one or more other compounds to obtain the cosmetic formulation.

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