A method for preparing a fatty alcohol by hydrolyzing a fatty acid ester

Abstract

The application provides a method for preparing a fatty alcohol by hydrogenation reaction of a fatty acid ester, which adopts a tower reactor filled with a hydrogenation catalyst as a reactor, the reactor comprising a fatty acid ester feeding port located at the upper part of the reactor and a hydrogen feeding port located below the fatty acid ester feeding port, and further comprising a gas discharge port located at the top of the reactor and a fatty alcohol discharge port located at the bottom of the tower reactor; the method comprises the following steps: feeding the fatty acid ester into the tower reactor through the fatty acid ester feeding port, feeding hydrogen into the tower reactor through the hydrogen feeding port, and allowing the fatty acid ester and the hydrogen to undergo countercurrent hydrogenation reaction under the action of the hydrogenation catalyst to generate the fatty alcohol and a low-carbon alcohol, and collecting the fatty alcohol through the fatty alcohol discharge port and collecting the low-carbon alcohol and excess hydrogen through the gas discharge port; the low-carbon alcohol has a carbon number of 1-4. The method has good mass transfer and heat transfer effects, and can obtain high fatty acid ester conversion rate and fatty alcohol selectivity under mild conditions.

Description

Technical Field

[0001] This invention belongs to the field of petrochemicals and relates to a method for preparing fatty alcohols by hydrogenation reaction of fatty acid esters. Background Technology

[0002] Fatty alcohols are fine chemicals produced on a large industrial scale and are widely used in various fields such as chemical engineering, petroleum, metallurgy, fragrance, papermaking, food, medicine and health, and agriculture. Fatty alcohols prepared from natural oils and fats have advantages such as renewability, high safety, and good quality, making them the preferred choice for fields that come into contact with the human body, such as medicine and health, and daily chemical products, or fields that require high purity of fatty alcohols.

[0003] There are three main methods for preparing fatty alcohols from natural oils: direct hydrogenation of oils, hydrogenation of fatty acids, and hydrogenation of fatty acid esters. The method involving the reaction of oils with C1-C4 low-carbon alcohols to convert them into fatty acid esters, followed by hydrogenation to prepare fatty alcohols, has advantages such as relatively mild reaction conditions and high fatty alcohol yields, and is therefore the most widely used.

[0004] Reactors used for the hydrogenation of fatty acid esters to fatty alcohols mainly include fixed-bed and suspended-bed reactors. Examples include the suspended-bed hydrogenation technology for fatty alcohols developed by Simere in France and Marchon in the UK, and the fixed-bed hydrogenation technology developed by Henkel in Germany. The process of fixed-bed hydrogenation for fatty alcohols involves reacting fatty acid esters and circulating hydrogen under specific temperature and pressure through a fixed catalyst bed to produce fatty alcohols. Compared to suspended-bed hydrogenation, fixed-bed hydrogenation offers advantages such as faster reaction rates, shorter residence times, less backmixing, less wear on equipment from solid catalysts, and simpler separation, making it more widely used. However, fixed-bed hydrogenation also has drawbacks. For instance, the fatty acid ester hydrogenation reaction is exothermic, and the raw material fatty acid ester is in a liquid state. Since the catalytic hydrogenation equipment is a fixed-bed adiabatic reactor, the reactor temperature cannot be controlled by steam tracing or condensate, making it difficult to dissipate the heat released during the reaction. This results in difficulty in controlling the reactor temperature and the generation of a series of byproducts, such as alkanes. Furthermore, in fixed-bed reactors, uneven gas-liquid phase distribution and the formation of channeling can lead to localized overheating, with the reactant temperature continuously rising as the reaction proceeds. These poor mass and heat transfer issues not only easily cause excessive hydrogenation to form alkanes and reduce the selectivity of fatty alcohols, but also easily lead to problems such as active site aggregation and coking, accelerating catalyst deactivation; and even causing runaway reaction rates, posing safety risks. In addition, a separation unit is required after the fatty acid ester hydrogenation reaction to separate and recover fatty alcohol products, lower alcohols (such as methanol and ethanol), and hydrogen, further increasing the process complexity and production costs.

[0005] Currently, common techniques to overcome the poor mass and heat transfer effects in fixed-bed reactors include using highly saturated fatty acid esters as raw materials, increasing the amount of hydrogen, and using reaction solvents. Studies have shown that approximately 120 kJ of heat is released when each mole of a fatty acid carbon chain undergoes hydrogenation to saturation. Therefore, using highly saturated fatty acid esters as raw materials significantly reduces the heat of reaction and avoids overheating. However, this limits the range of raw materials that can be used, making it difficult to flexibly select low-cost raw materials based on price fluctuations. Increasing the amount of hydrogen allows the fatty acid ester raw material to be sprayed into the bed in a mist form, which can transfer the heat of reaction and avoid localized overheating. However, excessive hydrogen can easily lead to deep hydrogenation of the fatty acid ester into aliphatic hydrocarbons and increase reaction energy consumption. Using reaction solvents can promote the mutual solubility of reactants and reduce mass transfer resistance, but it increases the difficulty of product separation and reaction energy consumption.

[0006] Therefore, it is of great significance to develop a method for preparing fatty alcohols by hydrogenation of fatty acid esters that has a wide range of applications, good mass and heat transfer effects, and low energy consumption. Summary of the Invention

[0007] This invention provides a method for preparing fatty alcohols by hydrogenation reaction of fatty acid esters. This method involves hydrogenating fatty acid esters with hydrogen gas via convection, which has good mass and heat transfer effects and enables the reaction to achieve high fatty acid ester conversion and high fatty alcohol selectivity under mild conditions.

[0008] This invention provides a method for preparing fatty alcohols by hydrogenation reaction of fatty acid esters. The method uses a tower reactor filled with a hydrogenation catalyst as the reactor. The tower reactor includes a fatty acid ester inlet located at the top of the tower reactor and a hydrogen inlet located below the fatty acid ester inlet. The tower reactor also includes a gas outlet located at the top of the tower reactor and a fatty alcohol outlet located at the bottom of the tower reactor.

[0009] The method includes introducing fatty acid ester into the tower reactor through the fatty acid ester inlet, introducing hydrogen into the tower reactor through the hydrogen inlet, the fatty acid ester and the hydrogen undergoing a convective hydrogenation reaction under the action of the hydrogenation catalyst to generate fatty alcohol and low-carbon alcohol, and collecting fatty alcohol through the fatty alcohol outlet and collecting the low-carbon alcohol and excess hydrogen through the gas outlet.

[0010] The lower alcohol has 1 to 4 carbon atoms.

[0011] In the method described above, the molar ratio of the fatty acid ester to the hydrogen gas is 1:(10-300).

[0012] In the method described above, the temperature of the convective hydrogenation reaction is 160–300 °C, the pressure is 0.5–14 MPa, and the mass hourly space velocity (WHSV) of the fatty acid ester is 0.2–3 h⁻¹. -1 .

[0013] In the method described above, the temperature of the convective hydrogenation reaction is 180–260°C, the pressure is 1–8 MPa, and the mass hourly space velocity (WHSV) of the fatty acid ester is 0.5–2 h⁻¹. -1 .

[0014] The method described above, wherein the fatty acid ester is obtained by reacting animal or vegetable oils with the lower alcohol.

[0015] In the method described above, the fatty acid ester is obtained by reacting animal or vegetable oils with methanol.

[0016] In the method described above, the hydrogenation catalyst is selected from catalysts that have carbon-carbon double bond and ester group hydrogenation functions.

[0017] In the method described above, the interior of the tower reactor is provided with a packing layer for filling the hydrogenation catalyst, the porosity of which is 20-90%.

[0018] In the method described above, the porosity of the filler layer is 40-70%.

[0019] The method described above, wherein the tower reactor includes at least one hydrogen inlet;

[0020] The ratio of the furthest straight-line distance between the fatty acid ester inlet and the hydrogen inlet to the inner diameter of the tower reactor is greater than 8.

[0021] The present invention discloses a method for preparing fatty alcohols by hydrogenation of fatty acid esters. In this method, fatty acid esters and hydrogen are hydrogenated by convection under the condition of hydrogenation catalyst. Compared with the plug flow reaction of traditional fixed-bed reactors, convection can significantly improve the mass and heat transfer of the reaction. Low-carbon alcohols can also be continuously discharged from the top of the column in the gas phase, promoting the shift of reaction equilibrium. High fatty acid ester conversion and high fatty alcohol selectivity can be obtained under relatively mild reaction conditions. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of a tower reactor according to an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of the structure of a tower reactor according to another embodiment of the present invention.

[0024] Explanation of reference numerals in the attached figures:

[0025] 1: Fatty acid ester inlet;

[0026] 2: Hydrogen inlet;

[0027] 2a: First hydrogen inlet;

[0028] 2b: Second hydrogen inlet;

[0029] 3: Gas outlet;

[0030] 4: Fatty alcohol outlet;

[0031] 5: Filler layer. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0033] This invention provides a method for preparing fatty alcohols by hydrogenation reaction of fatty acid esters. The method uses a tower reactor packed with a hydrogenation catalyst. Figure 1 This is a schematic diagram of the structure of a tower reactor according to an embodiment of the present invention, as shown below. Figure 1 As shown, the tower reactor includes a fatty acid ester inlet 1 located at the top of the tower reactor and a hydrogen inlet 2 located below the fatty acid ester inlet 1. The tower reactor also includes a gas outlet 3 located at the top of the tower reactor and a fatty alcohol outlet 4 located at the bottom of the tower reactor.

[0034] The method includes introducing fatty acid esters into the tower reactor through fatty acid ester inlet 1 and hydrogen gas into the tower reactor through hydrogen inlet 2. The fatty acid esters and hydrogen gas undergo a convective hydrogenation reaction under the action of a hydrogenation catalyst to produce fatty alcohols and lower alcohols. The method also includes collecting the fatty alcohols through fatty alcohol outlet 4 and collecting the lower alcohols and excess hydrogen gas through gas outlet 3.

[0035] Among them, the number of lower alcohols ranges from 1 to 4.

[0036] The present invention is not limited to the location of the fatty acid ester inlet 1. As long as the fatty acid ester inlet 1 is located at the top of the tower reactor, it is beneficial for the fatty acid ester raw material to fall into the tower reactor by gravity to participate in the reaction. Figure 2 This is a schematic diagram of the structure of a tower reactor according to another embodiment of the present invention, as shown below. Figure 1 and Figure 2 As shown, the fatty acid ester inlet 1 is located on the upper part of the side wall of the tower reactor.

[0037] This invention does not limit the location or number of hydrogen inlets 2, as long as they are located below the fatty acid ester inlet 1, facilitating the upward flow of hydrogen to contact the fatty acid ester raw material and initiate a convection reaction. One or more hydrogen inlets 2 can be provided. Figure 1 As shown, the tower reactor includes a hydrogen inlet 2, which is located on the bottom of the side wall of the tower reactor. Figure 2 As shown, the tower reactor includes two hydrogen inlets, namely the first hydrogen inlet 2a and the second hydrogen inlet 2b, which are located at the bottom of the side wall of the tower reactor and the middle of the side wall of the tower reactor, respectively.

[0038] The gas outlet 3 of this invention is used to discharge excess hydrogen and low-carbon alcohols generated during the reaction process, and the fatty alcohol outlet 4 is used to discharge fatty alcohols generated during the reaction process.

[0039] The method for preparing fatty alcohols by hydrogenation reaction of fatty acid esters of the present invention includes: introducing fatty acid esters into the interior of a tower reactor through a fatty acid ester inlet 1 and introducing hydrogen gas into the interior of the tower reactor through a hydrogen inlet 2. Under the action of gravity, the fatty acid esters move downward along the axial direction of the tower, while the hydrogen gas, which has a lower density, moves upward along the axial direction of the tower. The descending fatty acid esters and the rising hydrogen gas will form convection in the tower and undergo a hydrogenation reaction under the action of a hydrogenation catalyst. The convection can increase the contact area between the fatty acid esters and hydrogen gas and can also allow the heat generated by the hydrogenation reaction to dissipate in a timely manner, resulting in good mass and heat transfer effects. This allows the reaction to achieve high fatty acid conversion rate and high fatty alcohol selectivity under relatively mild conditions.

[0040] The structure of the fatty acid ester of the present invention comes from two parts: one part is a fatty acid moiety with a long carbon chain, and the other part is a low-carbon alcohol moiety with 1 to 4 carbon atoms. After hydrogenation, the fatty acid ester can be reduced to the corresponding fatty alcohol and low-carbon alcohol. The carbon chain length of the reduced fatty alcohol is consistent with that of the fatty acid moiety, and the carbon chain length of the reduced low-carbon alcohol is consistent with that of the low-carbon alcohol moiety.

[0041] Using C1-C4 low-carbon alcohols as raw materials for the preparation of fatty acid esters can result in a large boiling point difference between the generated fatty alcohols and the by-product low-carbon alcohols. The fatty alcohols flow downwards under gravity and are discharged from the fatty alcohol outlet 4, where they are further collected. The generated low-carbon alcohols and excess hydrogen are discharged from the gas outlet 3. The discharged low-carbon alcohols and excess hydrogen can be further recovered and reused after condensation and separation.

[0042] In addition, lower alcohols have lower enthalpy of vaporization. For example, the molar enthalpy of vaporization of methanol at its normal boiling point is about 35.3 kJ / mol. During the reaction, the lower alcohols are distilled into a continuous gas phase and discharged from the top, which will significantly reduce the heat of reaction of the hydrogenation reaction.

[0043] In one specific embodiment, the molar ratio of fatty acid ester to hydrogen is 1:(10-300). A moderate excess of hydrogen is beneficial for sufficient contact between the fatty acid ester and hydrogen, which is conducive to the hydrogenation reaction. However, too much excess hydrogen will increase the reaction energy consumption and cost. Preferably, the molar ratio of fatty acid ester to hydrogen is 1:(30-80).

[0044] Furthermore, the temperature for the convective hydrogenation reaction is 160–300 °C, the pressure is 0.5–14 MPa, and the mass hourly space velocity (HHSV) of the fatty acid ester is 0.2–3 h⁻¹. -1 These convective hydrogenation reaction conditions allow for the efficient conversion of fatty acid esters and the efficient formation of fatty alcohols under relatively mild conditions. Preferably, the convective hydrogenation reaction temperature is 180–260°C, the pressure is 1–8 MPa, and the mass hourly space velocity (WHSV) of the fatty acid ester is 0.5–2 h⁻¹. -1 .

[0045] It should be noted that, in order to ensure that the lower alcohol can be smoothly discharged from the top of the tower reactor along with hydrogen, the reaction pressure should be lower than the saturated vapor pressure of the lower alcohol at the current reaction temperature.

[0046] In one specific embodiment, the fatty acid ester of the present invention is obtained by reacting animal and vegetable oils with low-carbon alcohols.

[0047] Both animal and vegetable oils are natural oils, possessing advantages such as renewability and high safety, which facilitates the production of higher-quality fatty alcohols. Specifically, animal oils can be triglycerides of palmitic acid, stearic acid, and oleic acid, while vegetable oils can be triglycerides of linoleic acid, linolenic acid, and ricinoleic acid.

[0048] Furthermore, the fatty acid esters of the present invention are obtained by reacting animal and vegetable oils with methanol. Since methanol is low in cost and highly reactive, it is usually chosen as the reaction raw material for preparing fatty acid esters.

[0049] This invention can use either a single fatty acid ester or a mixture of fatty acid esters as raw materials. When a mixture of fatty acid esters is used as raw materials, in order to facilitate separation from lower alcohols, the content of fatty acid esters with a carbon chain length of C12 to C24 is usually greater than 90 wt%.

[0050] This invention does not impose any particular limitation on the composition of the hydrogenation catalyst, as long as it has the function of hydrogenating carbon-carbon double bonds and ester groups. That is, the catalyst can both hydrogenate and reduce the unsaturated olefin portion of fatty acid esters to alkanes and hydrogenate and reduce the ester group portion to hydroxyl groups. In order to facilitate the separation of the catalyst from the raw materials and products after the reaction, a heterogeneous catalyst is usually selected to participate in the reaction.

[0051] The hydrogenation catalyst of the present invention is generally selected from supported catalysts, and the active component can be selected from at least one of Cu, Ni, Fe, Zn, Mn, Cr, Au, Ag, Pt, Pd, Ru, Rh, Co, and Mo. The support can be selected from conventional supports in the art such as alumina, silicon dioxide, and activated carbon.

[0052] In one specific embodiment, the tower reactor of the present invention is further provided with a packing layer for loading hydrogenation catalyst. In order to ensure that hydrogen and fatty acid ester can fully contact the hydrogenation catalyst in the packing layer and that the heat of reaction can be diffused in time, the porosity of the packing layer can be controlled to be 20-90%, preferably 40-70%.

[0053] The hydrogenation catalyst of this invention can be directly made into porous honeycomb ceramic as a packing material, or it can be fixed into a specific shape by means of pressing, extrusion, etc., or formed into a metal mesh by porous metal hanging bags. It can also be uniformly mixed with other packing materials such as traditional θ rings and corrugated plates before being loaded. When the hydrogenation catalyst is mixed with other packing materials, the mixing volume ratio of the hydrogenation catalyst to other packing materials should be not less than 30:100 to ensure that there is a sufficient amount of hydrogenation catalyst in the tower to participate in the reaction.

[0054] This invention does not limit the type of tower reactor; any tower reactor commonly used in the art can be used, including but not limited to packed towers, sieve plate towers, bubble cap towers, or valve trains.

[0055] Furthermore, the tower reactor of the present invention includes at least one hydrogen inlet, and in order to ensure that the fatty acid ester and hydrogen have sufficient convective contact time and contact area so that the reaction can proceed fully, the ratio of the furthest straight distance between the fatty acid ester inlet and the hydrogen inlet to the inner diameter of the tower reactor should be greater than 8.

[0056] It should be noted that the farthest straight-line distance refers to the straight-line distance between the fatty acid ester inlet and the hydrogen inlet furthest from it. When the tower reactor has only one hydrogen inlet, the farthest straight-line distance is the straight-line distance between the fatty acid inlet and this hydrogen inlet. When the tower reactor has multiple hydrogen inlets, the farthest straight-line distance is the straight-line distance between the fatty acid ester inlet and the hydrogen inlet furthest from it.

[0057] The method for preparing fatty alcohols by hydrogenation of fatty acid esters provided by the present invention will be further described in detail below with reference to specific embodiments.

[0058] Example 1

[0059] The structure of the tower reactor in this embodiment is similar to... Figure 2In this embodiment, the inner diameter of the tower reactor is 50 mm, and it includes a fatty acid ester inlet 1, a first hydrogen inlet 2a, a second hydrogen inlet 2b, a gas outlet 3, a fatty alcohol outlet 4, and a packing layer 5. The straight-line distance between the fatty acid ester inlet 1 and the first hydrogen inlet 2a is 6 m.

[0060] Among them, the gas outlet 3 is located at the top of the tower reactor, the fatty alcohol outlet 4 is located at the bottom of the tower reactor, the fatty acid ester inlet 1, the first hydrogen inlet 2a and the second hydrogen inlet 2b are located at the upper part, lower part and middle part of the side wall of the tower reactor, respectively, and the distance between the second hydrogen inlet 2b and the fatty acid ester inlet 1 and the first hydrogen inlet 2a is 3m.

[0061] The packing layer 5 is located between the fatty acid ester inlet 1 and the fatty alcohol outlet 4 of the tower reactor. The packing layer 5 is filled with a Pd / C catalyst with a loading of 10 wt%. The catalyst is filled in a metal wire mesh bag. The catalyst accounts for 60% of the total volume of the packing layer, and the porosity of the packing layer is 70%.

[0062] This embodiment describes a method for preparing fatty alcohols by hydrogenating fatty acid esters using the aforementioned tower reactor, which includes the following steps:

[0063] Fatty acid methyl esters prepared by reacting rapeseed oil with methanol are introduced into a tower reactor through fatty acid ester inlet 1. Hydrogen gas is split into two streams and introduced into the tower reactor through the first hydrogen inlet 2a and the second hydrogen inlet 2b, respectively, to allow the fatty acid methyl esters to undergo a convective hydrogenation reaction with hydrogen gas. The reaction temperature is 260℃, the pressure is 8MPa, and the mass hourly space velocity (HSV) of the fatty acid methyl esters is 3h⁻¹. -1 The molar ratio of hydrogen to fatty acid methyl ester introduced through the first hydrogen inlet 2a is 200:1, and the molar ratio of hydrogen to fatty acid methyl ester introduced through the second hydrogen inlet 2b is 80:1. The generated fatty alcohol is continuously discharged from the fatty alcohol outlet 4 at the bottom of the column, while excess hydrogen and methanol vapor are continuously discharged from the top of the column. After being discharged from the column, the excess hydrogen and methanol vapor are condensed and separated to separate methanol and hydrogen for reuse.

[0064] Gas chromatography analysis showed that the conversion rate of fatty acid methyl esters in this embodiment was 98.4%, and the selectivity of fatty alcohols was 75.6%.

[0065] Example 2

[0066] The structure of the tower reactor in this embodiment is similar to... Figure 1 In this embodiment, the inner diameter of the tower reactor is 50 mm, and it includes a fatty acid ester inlet 1, a hydrogen inlet 2, a gas outlet 3, a fatty alcohol outlet 4, a packing layer 5, and the straight-line distance between the fatty acid ester inlet 1 and the hydrogen inlet 2 is 6 m.

[0067] The fatty acid methyl ester inlet 1 is located on the upper part of the side wall of the tower reactor, the hydrogen inlet 2 is located on the lower part of the side wall of the tower reactor, the gas outlet 3 is located at the top of the tower reactor, and the fatty alcohol outlet 4 is located at the bottom of the tower reactor.

[0068] The packing layer 5 is located between the fatty acid ester inlet 1 and the gas inlet 2 of the tower reactor. The packing layer 5 is filled with a mixture of 5mm×5mm θ rings of copper-zinc-aluminum catalyst and 5mm×5mm θ rings of metal wire mesh, and is filled in a uniform mixing manner. The catalyst accounts for 30% of the total volume of the packing layer, and the porosity of the packing layer is 70%.

[0069] This embodiment describes a method for preparing fatty alcohols by hydrogenating fatty acid esters using the aforementioned tower reactor, which includes the following steps:

[0070] Fatty acid methyl esters (containing 85 wt% oleic acid methyl ester, 14 wt% linoleic acid methyl ester, and 1 wt% stearic acid methyl ester) are introduced into the tower reactor through fatty acid ester inlet 1. Hydrogen gas is introduced into the tower reactor through hydrogen inlet 2, causing the fatty acid methyl esters and hydrogen gas to undergo a convective hydrogenation reaction. The reaction temperature is 240℃, the pressure is 5 MPa, and the mass hourly space velocity (HSV) of the fatty acid methyl esters is 1 h⁻¹. -1 The molar ratio of fatty acid methyl ester to hydrogen is 1:100. The generated fatty alcohol is continuously discharged from the fatty alcohol outlet 4 at the bottom of the tower, while excess hydrogen and methanol vapor are continuously discharged from the top of the tower. After being discharged from the tower, the excess hydrogen and methanol vapor are condensed and separated to separate methanol and hydrogen for reuse.

[0071] Gas chromatography analysis showed that the conversion rate of fatty acid methyl esters in this embodiment was 99.5%, and the selectivity of fatty alcohols was 97.8%.

[0072] Example 3

[0073] The tower reactor in this embodiment has a structure that is basically the same as that in embodiment 1. The difference is that the packing layer 5 in this embodiment is filled with a mixture of nickel-based catalyst 5mm×5mm θ rings and metal wire mesh 5mm×5mm θ rings, which are filled in a uniform mixing manner. The catalyst accounts for 40% of the total volume of the packing layer, and the porosity of the packing layer is 60%.

[0074] This embodiment describes a method for preparing fatty alcohols by hydrogenating fatty acid esters using the aforementioned tower reactor, which includes the following steps:

[0075] Fatty acid methyl esters (containing 85 wt% oleic acid methyl ester, 14 wt% linoleic acid methyl ester, and 1 wt% stearic acid methyl ester) are introduced into the tower reactor through fatty acid ester inlet 1. Hydrogen gas is split into two streams and introduced into the tower reactor through the first hydrogen inlet 2 and the second hydrogen inlet, respectively, to allow the fatty acid methyl esters to undergo a convective hydrogenation reaction with hydrogen gas. The reaction temperature is 200℃, the pressure is 2 MPa, and the mass hourly space velocity (HSV) of the fatty acid methyl esters is 2 h⁻¹. -1 The molar ratio of hydrogen to fatty acid methyl ester introduced through the first hydrogen inlet 2 is 30:1, and the molar ratio of hydrogen to fatty acid methyl ester introduced through the second hydrogen inlet is 5:1. The generated fatty alcohol is continuously discharged from the fatty alcohol outlet 4 at the bottom of the column, while excess hydrogen and methanol vapor are continuously discharged from the top of the column. After being discharged from the column, the excess hydrogen and methanol vapor are condensed and separated to separate methanol and hydrogen for reuse.

[0076] Gas chromatography analysis showed that the conversion rate of fatty acid methyl esters in this embodiment was 96.7%, and the selectivity of fatty alcohols was 90.1%.

[0077] Example 4

[0078] The structure of the tower reactor in this embodiment is basically the same as that in embodiment 2. The difference is that the packing layer 5 in this embodiment is filled with a mixture of 5mm×5mm θ rings and 5mm×5mm θ rings of metal wire mesh with a loading of 3wt% Pt / SiO2 catalyst. The catalyst accounts for 50% of the total volume of the packing layer and is filled in a uniform mixing manner. The porosity of the packing layer is 50%.

[0079] This embodiment describes a method for preparing fatty alcohols by hydrogenating fatty acid esters using the aforementioned tower reactor, which includes the following steps:

[0080] Fatty acid methyl esters (containing 15 wt% palmitate methyl ester, 20 wt% oleate methyl ester, 5 wt% linoleate methyl ester, and 60 wt% stearate methyl ester) are introduced into a tower reactor through fatty acid ester inlet 1. Hydrogen gas is introduced into the tower reactor through hydrogen inlet 2, causing a convective hydrogenation reaction between the fatty acid methyl esters and hydrogen gas. The reaction temperature is 180℃, the pressure is 2 MPa, and the mass hourly space velocity (HSV) of the fatty acid methyl esters is 1 h⁻¹. -1 The molar ratio of fatty acid methyl ester to hydrogen is 1:50. The generated fatty alcohol is continuously discharged from the fatty alcohol outlet 4 at the bottom of the tower, while excess hydrogen and methanol vapor are continuously discharged from the top of the tower. After being discharged from the tower, the excess hydrogen and methanol vapor are condensed and separated to separate methanol and hydrogen for reuse.

[0081] Gas chromatography analysis showed that the conversion rate of fatty acid methyl esters in this embodiment was 98.9%, and the selectivity of fatty alcohols was 86.7%.

[0082] Example 5

[0083] The tower reactor in this embodiment has a structure that is basically the same as that in embodiment 1. The difference is that the packing layer 5 in this embodiment is filled with copper-zinc-aluminum catalyst structured packing, wherein the porosity of the packing layer is 60%.

[0084] This embodiment describes a method for preparing fatty alcohols by hydrogenating fatty acid esters using the aforementioned tower reactor, which includes the following steps:

[0085] Fatty acid methyl esters (including 10 wt% fatty acid ethyl esters) prepared by reacting cottonseed oil with methanol are introduced into a tower reactor through fatty acid ester inlet 1. Hydrogen gas is split into two streams and introduced into the tower reactor through the first hydrogen inlet 2 and the second hydrogen inlet, respectively, to allow the fatty acid methyl esters to undergo a convective hydrogenation reaction with hydrogen gas. The reaction temperature is 240℃, the pressure is 6 MPa, and the mass hourly space velocity (HSV) of the fatty acid methyl esters is 1 h⁻¹. -1 The molar ratio of hydrogen to fatty acid methyl ester introduced through the first hydrogen inlet 2 is 30:1, and the molar ratio of hydrogen to fatty acid methyl ester introduced through the second hydrogen inlet is 10:1. The generated fatty alcohol is continuously discharged from the fatty alcohol outlet 4 at the bottom of the column, while excess hydrogen and methanol vapor are continuously discharged from the top of the column. After being discharged from the column, the excess hydrogen and methanol vapor are condensed and separated to separate methanol and hydrogen for reuse.

[0086] Gas chromatography analysis showed that the conversion rate of fatty acid methyl esters in this embodiment was 99.3%, and the selectivity of fatty alcohols was 96.7%.

[0087] Example 6

[0088] The tower reactor structure and the method for preparing fatty alcohols by the hydrogenation reaction of fatty acid esters in this embodiment are basically the same as those in Example 1. The difference is that the catalyst in the packing layer 5 accounts for 20% of the total volume of the packing layer, and the porosity of the packing layer is 90%.

[0089] Gas chromatography analysis showed that the conversion rate of fatty acid methyl esters in this embodiment was 84.4%, and the selectivity of fatty alcohols was 96.6%.

[0090] Example 7

[0091] The structure of the tower reactor in this embodiment is basically the same as that of the tower reactor in embodiment 2. The difference is that the packing layer 5 in this embodiment is a mixed packing material containing 40% (accounting for the total volume of the packing layer) of copper-zinc-aluminum catalyst in 5mm×5mm θ rings and 5mm×5mm θ rings of metal wire mesh, and is packed in a uniform mixing manner. The catalyst accounts for 40% of the total volume of the packing layer, and the porosity of the packing layer is 60%.

[0092] This embodiment describes a method for preparing fatty alcohols by hydrogenating fatty acid esters using the aforementioned tower reactor, which includes the following steps:

[0093] Fatty acid ethyl esters prepared from soybean oil and ethanol are introduced into a tower reactor through fatty acid ester inlet 1. Hydrogen gas is introduced into the tower reactor through hydrogen inlet 2, causing a convective hydrogenation reaction between the fatty acid ethyl esters and hydrogen gas. The reaction temperature is 280℃, the pressure is 5MPa, and the mass hourly space velocity (HSV) of the fatty acid ethyl esters is 0.8h. -1 The molar ratio of fatty acid ethyl ester to hydrogen is 1:100. The generated fatty alcohol is continuously discharged from the fatty alcohol outlet 4 at the bottom of the column, while excess hydrogen and ethanol vapor are continuously discharged from the top of the column. After being discharged from the column, the excess hydrogen and ethanol vapor are condensed and separated to separate ethanol and hydrogen for reuse.

[0094] Gas chromatography analysis showed that the conversion rate of fatty acid ethyl esters in this embodiment was 99.6%, and the selectivity of fatty alcohols was 98.8%.

[0095] Example 8

[0096] The structure of the tower reactor in this embodiment is basically the same as that of the tower reactor in embodiment 7. The difference is that the inner diameter of the tower reactor is 50 mm, and the straight-line distance between the fatty acid ester inlet 1 and the hydrogen inlet 2 is 200 mm.

[0097] The method for preparing fatty alcohols by hydrogenation of fatty acid esters in this embodiment is the same as that in Example 7.

[0098] Gas chromatography analysis showed that the conversion rate of fatty acid ethyl esters in this embodiment was 39.6%, and the selectivity of fatty alcohols was 98.8%.

[0099] Comparative Example 1

[0100] The reactor in this comparative example is a tubular reactor with a packing layer inside. The packing layer is filled with a mixture of 5mm×5mm θ rings of copper-zinc-aluminum catalyst and 5mm×5mm θ rings of metal wire mesh, and is packed in a uniform mixing manner. The catalyst accounts for 30% of the total volume of the packing layer, and the porosity of the packing layer is 70%.

[0101] This comparative example uses the above-mentioned tubular reactor to prepare fatty alcohols via the hydrogenation reaction of fatty acid esters, and includes the following steps:

[0102] Fatty acid methyl esters (containing 85 wt% oleic acid methyl ester, 14 wt% linoleic acid methyl ester, and 1 wt% stearic acid methyl ester) and hydrogen gas were fed into a tubular reactor from top to bottom, allowing the fatty acid methyl esters to undergo a plug flow hydrogenation reaction with hydrogen gas. The reaction temperature was 240℃, the pressure was 5 MPa, and the mass hourly space velocity (HSV) of the fatty acid methyl esters was 1 h⁻¹. -1The molar ratio of fatty acid methyl ester to hydrogen is 1:100. The generated fatty alcohol, lower alcohol, and excess hydrogen are continuously discharged, and methanol and excess hydrogen are separated.

[0103] Gas chromatography analysis showed that the conversion rate of fatty acid methyl esters in this comparative example was 82.5%, and the selectivity of fatty alcohols was 94.8%.

[0104] Comparative Example 2

[0105] The tower reactor structure in this embodiment is the same as that in Embodiment 8.

[0106] This embodiment describes a method for preparing fatty alcohols by hydrogenating fatty acid esters using the aforementioned tower reactor, which includes the following steps:

[0107] Octyl stearate is introduced into a tower reactor through inlet 1, and hydrogen gas is introduced into the tower reactor through inlet 2, causing octyl stearate to undergo a convective hydrogenation reaction with hydrogen gas. The reaction temperature is 280℃, the pressure is 5MPa, and the mass hourly space velocity (HSV) of octyl stearate is 0.8h⁻¹. -1 The molar ratio of octyl stearate to hydrogen is 1:100. The generated fatty alcohol and liquid octanol are continuously discharged from the fatty alcohol outlet 4 at the bottom of the column, while excess hydrogen and a small amount of octanol vapor are continuously discharged from the top of the column.

[0108] Gas chromatography analysis showed that the conversion rate of octyl stearate in this embodiment was 59.6%, and the selectivity for fatty alcohols was 97.8%.

[0109] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing fatty alcohols by hydrogenation reaction of fatty acid esters, characterized in that, A tower reactor filled with a hydrogenation catalyst is used as the reactor. The tower reactor includes a fatty acid ester inlet located on the upper part of the side wall of the tower reactor and a hydrogen inlet located below the fatty acid ester inlet. The tower reactor also includes a gas outlet located at the top of the tower reactor and a fatty alcohol outlet located at the bottom of the tower reactor. The hydrogen inlet includes a first hydrogen inlet and a second hydrogen inlet, which are respectively located at the bottom of the side wall of the tower reactor and the middle of the side wall of the tower reactor. The method includes introducing fatty acid ester into the tower reactor through the fatty acid ester inlet, introducing hydrogen into the tower reactor through the hydrogen inlet, the fatty acid ester and the hydrogen undergoing a convective hydrogenation reaction under the action of the hydrogenation catalyst to generate fatty alcohol and low-carbon alcohol, and collecting fatty alcohol through the fatty alcohol outlet and collecting the low-carbon alcohol and excess hydrogen through the gas outlet. The lower alcohol has 1 to 4 carbon atoms; The tower reactor is equipped with a packing layer for filling the hydrogenation catalyst, and the porosity of the packing layer is 40-70%.

2. The method according to claim 1, characterized in that, The molar ratio of the fatty acid ester to the hydrogen gas is 1:(10~300).

3. The method according to claim 1 or 2, characterized in that, The convective hydrogenation reaction is carried out at a temperature of 160–300 °C, a pressure of 0.5–14 MPa, and a mass hourly space velocity (HHSV) of 0.2–3 h⁻¹ for the fatty acid ester. -1 .

4. The method according to claim 3, characterized in that, The convective hydrogenation reaction is carried out at a temperature of 180–260 °C, a pressure of 1–8 MPa, and a mass hourly space velocity (WHSV) of 0.5–2 h⁻¹ for the fatty acid ester. -1 .

5. The method according to any one of claims 1-4, characterized in that, The fatty acid ester is obtained by reacting animal and vegetable oils with the low-carbon alcohol.

6. The method according to claim 5, characterized in that, The fatty acid esters are obtained by reacting animal and vegetable oils with methanol.

7. The method according to any one of claims 1-6, characterized in that, The hydrogenation catalyst is selected from catalysts that have the hydrogenation function of carbon-carbon double bonds and ester groups.

8. The method according to any one of claims 1-7, characterized in that, The ratio of the furthest straight-line distance between the fatty acid ester inlet and the hydrogen inlet to the inner diameter of the tower reactor is greater than 8.

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