Method for directly preparing fatty alcohol by catalyzing grease based on nickel-based dual-carrier catalyst

Abstract

The invention relates to the technical field of fatty alcohol preparation, and particularly discloses a method for directly preparing fatty alcohol by catalyzing grease based on a nickel-based dual-carrier catalyst, which comprises the following steps: mixing a nickel salt aqueous solution, a metal oxide and activated carbon by a co-impregnation method, and sequentially carrying out drying, air calcination and hydrogen reduction treatment on the mixture formed by mixing, the nickel-based dual-carrier catalyst is prepared; the method comprises the following steps: adding the nickel-based dual-carrier catalyst, grease and an organic solvent into a reaction kettle, introducing hydrogen, and carrying out hydrogenation reaction at a preset temperature to generate fatty alcohol. The catalyst is prepared through a co-impregnation method, the process is simple, operation and large-scale production are easy, and meanwhile the catalyst is excellent in cycle stability and still keeps high catalytic activity after being repeatedly used for multiple times; the Ni-based dual-carrier catalyst prepared by the method can efficiently convert grease into fatty alcohol, the highest yield of the fatty alcohol can reach 80% or above, the selectivity is high, and the content of by-products such as alkane is low.

Description

Technical Field

[0001] The invention relates to the technical field of fatty alcohol preparation, and in particular to a method for directly preparing fatty alcohol from oils and fats using a nickel-based dual-carrier catalyst. Background Art

[0002] Most existing fatty alcohols are derived from fatty acids or fatty acid methyl esters derived from oils and fats. The oils and fats (or triglycerides) need to be hydrolyzed or methylated first. There are many reaction steps, involving the separation and purification of intermediates, and the cost is high. There are few processes in the existing technology that can directly realize the one-step preparation of fatty alcohols from oils and fats. Specifically, the existing commercial production route of fatty alcohols involves a two-step process: first, fatty acid triglycerides are converted into fatty acid methyl esters through an ester exchange reaction, and then hydrogenated using a copper-chromium (Cu-Cr) catalyst to produce fatty alcohols. However, commercial Cu-Cr catalysts operate under high temperature (200-400°C) and high pressure (20-30MPa H2) reaction conditions, which poses a potential risk of chromium leaching and poses serious environmental risks.

[0003] Foreign Journal: Highly selective and low-temperature hydrothermal conversion of natural oils to fatty alcohols (DOI:10.1039 / c9gc01260e), the author used RuSn / NC to achieve the hydrogenation of oils to fatty alcohols at 140°C and 5MPa H2. However, this method uses precious metals and heavy metal tin as catalysts, which are expensive and easy to pollute the environment. Foreign Journal: Direct hydrogenation of natural oils to fatty alcohols enabled by an alcoholysis / hydrogenation relaystrategy and two-phase solvent system (DOI:10.1039 / d4ob00822g), the author used ruthenium complex as catalyst and base as additive, and achieved the conversion from triglycerides to fatty alcohols in a reaction time of 24h. Its disadvantage is that it uses a homogeneous catalyst ruthenium complex, the catalyst cost is high and difficult to recover.

[0004] Therefore, the existing technology still needs to be improved and developed. Summary of the Invention

[0005] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a method for directly preparing fatty alcohols from oils and fats based on a nickel-based dual-support catalyst, aiming to solve the problem that the prior art requires the use of precious metal catalysts to prepare fatty alcohols, resulting in high preparation costs and easy environmental pollution.

[0006] The technical solutions of the present invention are as follows:

[0007] A method for directly preparing fatty alcohols from oils and fats using a nickel-based dual-support catalyst, comprising the following steps:

[0008] A nickel-based dual-support catalyst is prepared by mixing a nickel salt aqueous solution, a metal oxide and activated carbon by a co-impregnation method, and sequentially drying, air calcining and hydrogen reduction treatment are performed on the mixture.

[0009] A nickel-based dual-support catalyst, oil and organic solvent are added to a reactor and hydrogen is introduced. A hydrogenation reaction occurs at a preset temperature to produce fatty alcohols.

[0010] The method for directly preparing fatty alcohols from oils and fats based on a nickel-based dual-support catalyst, wherein the nickel salt aqueous solution is one or more of a nickel nitrate aqueous solution, a nickel acetate aqueous solution, and a nickel chloride aqueous solution; and the metal oxide is one or more of aluminum oxide, zirconium oxide, iron oxide, tungsten oxide, titanium oxide, manganese oxide, cobalt oxide, and zinc oxide.

[0011] The method for directly preparing fatty alcohols from oils and fats using a nickel-based dual-support catalyst is characterized in that the mass of the nickel element in the nickel-based dual-support catalyst accounts for 0.1-20% of the total mass of the nickel-based dual-support catalyst.

[0012] The method for directly preparing fatty alcohols from oils and fats based on a nickel-based dual-support catalyst comprises the following steps: in the step of mixing a nickel salt aqueous solution, a metal oxide, and activated carbon by a co-impregnation method, the mass ratio of the metal oxide to the activated carbon is 1:0.1-10.

[0013] The method for directly preparing fatty alcohol from oil and fat using a nickel-based dual-carrier catalyst comprises the following steps: drying the mixture at a temperature of 80-120° C. for 10-20 hours.

[0014] The method for directly preparing fatty alcohols from oils and fats using a nickel-based dual-carrier catalyst comprises the following steps: in the step of air calcining the mixed mixture, the temperature is raised to 350-400° C. at a heating rate of 2-5° C. / min under an air atmosphere and maintained for 3-5 hours.

[0015] The method for directly preparing fatty alcohols from oils and fats using a nickel-based dual-support catalyst comprises the following steps: in the step of subjecting the mixed mixture to hydrogen reduction treatment, introducing an inert gas to purge and replace the air; then introducing hydrogen or a mixture of hydrogen and nitrogen; and heating the mixture to 350-400° C. at a heating rate of 5-10° C. / min and maintaining the temperature for 3-5 hours; and subjecting the calcined mixture to reduction activation to prepare the nickel-based dual-support catalyst.

[0016] The method for directly preparing fatty alcohols from oils and fats using a nickel-based dual-support catalyst, wherein the organic solvent is one of n-hexane, n-dodecane and cyclohexane.

[0017] The method for directly preparing fatty alcohols from oil and fat using a nickel-based dual-support catalyst comprises the following steps: adding the nickel-based dual-support catalyst, oil and fat, and an organic solvent into a reactor and introducing hydrogen, with the flow rate of the introduced hydrogen being 0.5-5.0 L / min.

[0018] The method for directly preparing fatty alcohols from oils and fats using a nickel-based dual-support catalyst comprises the following steps: in the step of hydrogenation reaction occurring at a preset temperature, the preset temperature is 200-300° C., and the reaction time is 10-15 hours.

[0019] Beneficial effects: The present invention uses non-precious metal Ni as the active metal. Not only is the cost of Ni much lower than that of precious metals, but it is also significantly more environmentally friendly than catalysts containing heavy metals, avoiding potential environmental problems such as chromium leaching. The catalyst of the present invention is prepared by a co-impregnation method, which has a simple process, is easy to operate and mass-produce. At the same time, the catalyst has excellent cyclic stability and can be reused multiple times while still maintaining a high catalytic activity, further reducing the cost of the catalyst. The Ni-based dual-support catalyst (loaded on metal oxides and activated carbon) prepared by the present invention can efficiently convert oils (triglycerides) into fatty alcohols, with a fatty alcohol yield of up to 80% or more, high selectivity, and a low content of by-products such as alkanes. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The present invention is a flow chart of a method for directly preparing fatty alcohols from oils and fats using a nickel-based dual-support catalyst. DETAILED DESCRIPTION

[0021] The present invention provides a method for directly preparing fatty alcohols from oils and fats using a nickel-based dual-support catalyst. To clarify the objectives, technical solutions, and effects of the present invention, the present invention is described in further detail below. It should be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention.

[0022] See also Figure 1 , Figure 1The present invention provides a method for directly preparing fatty alcohols from oils and fats using a nickel-based dual-support catalyst, as shown in the figure, which includes the following steps:

[0023] S10, mixing a nickel salt aqueous solution, a metal oxide, and activated carbon by a co-impregnation method, and sequentially drying, air calcining, and hydrogen reducing the mixture to obtain a nickel-based dual-support catalyst;

[0024] S20, adding a nickel-based dual-support catalyst, oil and fat, and an organic solvent into a reactor and introducing hydrogen gas to cause a hydrogenation reaction at a preset temperature to generate fatty alcohol.

[0025] Specifically, the present invention uses non-precious metal Ni as the active metal and prepares a nickel-based dual-carrier catalyst by a co-impregnation method. Not only is Ni much cheaper than precious metals, but it is also significantly more environmentally friendly than heavy metal-containing catalysts, avoiding potential environmental problems such as chromium leaching. At the same time, the nickel-based dual-carrier catalyst prepared by the present invention has obvious advantages over single-carrier catalysts. It has strong catalytic activity and excellent cyclic stability. It can maintain a high catalytic activity after repeated use, further reducing the cost of the catalyst. The Ni-based dual-carrier catalyst prepared in this application can efficiently convert oils (triglycerides) into fatty alcohols, with a fatty alcohol yield of up to 80% or more, and high selectivity, and a low content of by-product alkanes. The oil in this application refers to a natural oil or non-natural oil whose main component is triglyceride. For example, the natural oil includes but is not limited to palm oil, coconut oil, olive oil, soybean oil, etc.; the non-natural oil includes but is not limited to tricaprin, caprylic triglyceride, etc.

[0026] In some embodiments, the nickel salt aqueous solution is one or more of a nickel nitrate aqueous solution, a nickel acetate aqueous solution, and a nickel chloride aqueous solution, but is not limited thereto. The nickel salts selected in this embodiment are all those with good water solubility, a moderate decomposition temperature, and few residual impurities. Nickel nitrate is preferred in this embodiment because nickel nitrate has excellent water solubility and decomposes completely (generating NiO and gas) during calcination, leaving little residue.

[0027] In some embodiments, the metal oxide is one or more of aluminum oxide, zirconium oxide, iron oxide, tungsten oxide, titanium oxide, manganese oxide, cobalt oxide, and zinc oxide, but is not limited thereto. In this embodiment, metal oxides having good thermal stability and compatibility with activated carbon are selected as catalyst supports. In this embodiment, zinc oxide and aluminum oxide are preferred as supports, both of which provide high mechanical strength and thermal stability, are relatively low in cost, and are widely applicable.

[0028] In some embodiments, in the nickel-based dual-support catalyst, the mass of nickel element accounts for 0.1-20% of the total mass of the nickel-based dual-support catalyst. Specifically, a lower nickel loading is conducive to the formation of smaller and highly dispersed nickel nanoparticles. Small nickel nanoparticles have a higher specific surface area and more exposed active sites, and are generally more catalytically active. If the nickel loading is too high (>20wt%), it is easy to cause the Ni particles to agglomerate and grow during calcination and reduction, reducing the effective active surface area and possibly clogging the carrier pores; if the nickel loading is too low (<0.1wt%), it is easy to cause the generated nickel nanoparticles to be less, and it is impossible to achieve comprehensive loading on the carrier surface (reduction of active sites), which also reduces the overall catalytic activity. In this embodiment, the mass of nickel element accounts for 0.1-20% of the total mass of the nickel-based dual-support catalyst, while ensuring sufficient active sites, maximizing dispersion and metal utilization efficiency.

[0029] In some embodiments, in the step of mixing the nickel salt aqueous solution, metal oxide and activated carbon by co-impregnation, the mass ratio of the metal oxide to the activated carbon is 1:0.1-10. Specifically, in the process of preparing the nickel-based dual-support catalyst, activated carbon as a nickel-based support can provide an extremely high specific surface area (usually hundreds or even thousands of m 2 / g), which is conducive to the high dispersion and loading of active metal (Ni), and its developed pore structure (especially mesopores and macropores) is conducive to the diffusion and mass transfer of macromolecular triglycerides and product fatty alcohols. Its surface functional groups may participate in anchoring metal precursors or reaction intermediates, but its mechanical strength and thermal stability are relatively poor. The metal oxide can provide excellent thermal stability and mechanical strength as a carrier to prevent the catalyst from structurally collapsing during high-temperature calcination, reduction and reaction. Some oxides may provide weakly acidic or alkaline sites to assist in cracking or deoxidation steps. In this embodiment, metal oxide and activated carbon are selected to form a dual carrier, which can fully utilize the high specific surface area and excellent mass transfer performance of activated carbon, and can obtain sufficient thermal / mechanical stability through metal oxide, avoiding excessive ablation or structural collapse that may occur in pure activated carbon carriers at high temperatures. Further, the mass ratio of metal oxide to activated carbon in this embodiment is 1:0.1-10, preferably 1:1. Too high an activated carbon ratio may sacrifice stability, and too high a metal oxide ratio may reduce the overall specific surface area, which is not conducive to Ni dispersion and reactant diffusion.

[0030] In some specific embodiments, a calculated amount of Ni salt is dissolved in an appropriate amount of deionized water. The amount of water should be just enough to immerse and wet all the carrier powders (activated carbon AC + metal oxide MOx) to form a stirrable slurry, but not too much to avoid a long subsequent drying time. The initial wetness impregnation method is usually adopted; then the activated carbon powder and the metal oxide powder are physically mixed in advance, and then the uniformly mixed carrier powder is slowly added to the nickel salt aqueous solution while stirring vigorously (or using a rotary evaporator) to ensure that the solution is evenly absorbed by the carrier to avoid local oversaturation or agglomeration. Stirring is continued for a period of time (e.g., 1-2 hours) to allow the metal ions to be fully adsorbed and distributed on the surface and inner pores of the carrier to obtain a mixture.

[0031] In some embodiments, the step of drying the mixture is performed at a temperature of 80-120° C. for 10-20 hours. Specifically, the mixture is transferred to a drying oven and dried at a temperature of 80-120° C. for 10-20 hours to completely remove physically adsorbed water, prevent material splashing or structural damage due to rapid evaporation of water during subsequent calcination, and preliminarily fix the metal salt on the surface of the support.

[0032] In some embodiments, in the step of air calcining the mixture, the temperature is raised to 350-400°C at a heating rate of 2-5°C / min under an air atmosphere and maintained for 3-5 hours. Specifically, the dried material is transferred to a muffle furnace or a tube furnace, and the temperature is raised to 350-400°C at a heating rate of 2-5°C / min under an air atmosphere and maintained for 3-5 hours to thermally decompose the nickel salt (e.g., nickel nitrate) into the corresponding metal oxide (NiO). The decomposition gas (NO2, etc.) is carried away by the air flow. The high temperature of 350-400°C in this embodiment helps to form a certain interaction between the metal oxide particles and the support, and preliminarily stabilizes the catalyst structure. At the same time, at 350-400°C in air, the surface of the activated carbon undergoes partial oxidation and ablation (combustion). This plays two important roles: pore formation and pore unblocking: ablation of some amorphous carbon and substances that block the pores increases the porosity of the catalyst, especially the mesopores and macropores that are conducive to the entry and exit of large molecules, significantly improving the mass transfer performance. Surface modification: oxygen-containing functional groups (carboxyl, carbonyl, phenolic hydroxyl, etc.) are introduced on the surface of activated carbon. These functional groups can serve as anchor points to help stabilize and disperse the metal Ni particles in the subsequent reduction step and prevent them from excessive migration and agglomeration.

[0033] In this example, the calcination temperature and time must be strictly controlled. Too low a temperature or too short a time will result in incomplete decomposition; too high a temperature or too long a time will lead to excessive ablation and loss of the activated carbon (or even complete burnout), sintering and growth of metal oxides, a decrease in specific surface area and pore volume, and ultimately deterioration of catalyst performance. A temperature of 350-400°C for 3-5 hours effectively decomposes salts and moderately creates pores without excessively damaging the activated carbon skeleton or metal dispersion.

[0034] In some embodiments, in the step of subjecting the mixed mixture to hydrogen reduction treatment, an inert gas is introduced to purge and replace the air, and then hydrogen or a mixture of hydrogen and nitrogen is introduced, and the temperature is raised to 350-400°C at a heating rate of 5-10°C / min and maintained for 3-5h, and the calcined mixture is subjected to reduction activation to obtain a nickel-based dual-support catalyst.

[0035] Specifically, the calcined material (NiO / AC / MOx in this case) is transferred to a tubular reduction furnace or reactor, and an inert gas (such as nitrogen or argon) is introduced to purge and replace the air. Then, hydrogen or a mixture of hydrogen and nitrogen is introduced, and the temperature is raised to 350-400°C at a heating rate of 5-10°C / min and maintained for 3-5 hours for reduction activation. After the reduction is completed, it is cooled to room temperature (or the required temperature) under a hydrogen atmosphere. The reduced catalyst is sensitive to air (will be oxidized and inactivated) and needs to be stored in an inert atmosphere until it is put into the reaction. The core function of hydrogen reduction in this embodiment is to reduce the metal oxide (mainly NiO) generated by calcination into catalytically active metal nickel nanoparticles. The reduction temperature and time affect the size and dispersion of the Ni particles. Maintaining the temperature at 350-400°C for 3-5 hours can usually achieve relatively complete reduction of NiO while avoiding excessive sintering and growth of Ni particles, maintaining a small particle size and high dispersion. It can also further remove some oxygen-containing species that may remain on the surface of the metal oxide or activated carbon after calcination, completing the final formation and stabilization of the catalyst active phase under a reducing atmosphere.

[0036] In some embodiments, the organic solvent is one of n-hexane, n-dodecane and cyclohexane, but is not limited thereto. The organic solvent of this embodiment is mainly used to reduce the solubility of the reactants and improve the solubility and diffusion efficiency of hydrogen in the liquid phase. N-dodecane, which has a large boiling point difference with the product and is stable at high temperatures, is preferably used as the reaction solvent.

[0037] In some embodiments, in the step of adding a nickel-based dual-support catalyst, grease, and an organic solvent to a reactor and introducing hydrogen, the flow rate of the hydrogen is 0.5-5.0 L / min. Specifically, if the flow rate of the hydrogen is too low (<0.5 L / min), H2 may not diffuse to the catalyst surface in time, the reaction rate may decrease, intermediates (such as aldehydes) may be retained, and excessive decarboxylation may occur to produce alkanes; if the flow rate of the hydrogen is too high (>5.0 L / min), the high airflow may cause catalyst particle wear or splashing. An appropriate hydrogen flow rate can ensure that H2 is continuously replenished to the liquid-solid interface, avoiding "hydrogen starvation" on the catalyst surface.

[0038] In some embodiments, a nickel-based dual-support catalyst, oil, and organic solvent are added to a reactor and hydrogen is introduced. A hydrogenation reaction is carried out at a preset temperature of 200-300° C. for 10-15 hours to produce fatty alcohols.

[0039] Specifically, the direct hydrogenation of oils and fats (triglycerides, RCOO-CH2-CH(OOCR')-CH2-OOCR") to fatty alcohols (R-CH2OH, R'-CH2OH, R"-CH2OH) over a Ni-based dual-support catalyst primarily involves two steps: hydrogenolysis and hydrodeoxygenation (HDO). The mechanism of action of the Ni-based dual-support catalyst in this process can be summarized as follows:

[0040] 1) Adsorption and activation: Triglyceride macromolecules first adsorb onto the catalyst surface. The high specific surface area (especially the activated carbon portion) and optimized pore structure of the dual carrier facilitate adsorption and mass transfer. Nano-nickel particles adsorb and dissociate hydrogen molecules (H2→2H), generating highly reactive adsorbed hydrogen atoms (H).

[0041] 2) Triglyceride Hydrocracking (C-O Bond Cleavage): Triglyceride molecules adsorbed on the catalyst (involving Ni sites and acidic / basic sites on the support) undergo hydrogenolysis cleavage of the C(O)-O bond (acyloxy bond) or C-O bond (alkoxy bond) in the ester bond (RCOO-CH2-) under the action of H*. The main pathway is: hydrogenolysis typically occurs preferentially at the O-CH2 bond of the glycerol backbone, producing fatty acids (RCOOH), fatty aldehydes, and the corresponding diglycerides and monoglycerides.

[0042] In this step, Ni 0 The provided H* is necessary for the cleavage of the CO bond.

[0043] 3) Hydrodeoxygenation (HDO) of fatty acids or fatty aldehydes to produce fatty alcohols: The generated fatty acids (RCOOH) or fatty aldehydes need to be further deoxygenated to obtain the target fatty alcohols (RCH2OH). This is the rate-limiting step and core catalytic point of the entire process. Ni catalysts mainly catalyze the following pathways:

[0044] Hydrodeoxygenation (direct HDO): fatty acids (RCOOH) adsorbed on Ni 0 At the active site, the carboxyl group (-COOH) is first hydrogenated to an aldehyde group (-CHO): RCOOH+2H*→RCHO+H2O; the aldehyde group (-CHO) is further rapidly hydrogenated to an alcohol group (-CH2OH): RCHO+2H*

[0045] →RCH2OH. Overall reaction: RCOOH + 4H* → RCH2OH + H2O. This is the main and desired pathway for the formation of fatty alcohols over Ni-based catalysts, which requires a catalyst with strong hydrogenation activity to saturate the C=O bond.

[0046] The present invention forms highly dispersed small-sized Ni nanoparticles by providing two supports and combining co-impregnation and optimized calcination and reduction conditions, providing abundant hydrogenation (activation of H2) and hydrogenolysis (breaking of CO bonds) active sites. Among them, the high specific surface area, developed pore structure (especially after moderate pore formation by air calcination) and surface properties of the activated carbon support are very conducive to the adsorption and diffusion of large molecular triglycerides and fatty acids and the desorption of product fatty alcohols, which is the key to overcoming the mass transfer limitations of large molecular reactants. The metal oxide component provides the structural stability required by the catalyst under high temperature reactions, preventing excessive pyrolysis or structural collapse of the activated carbon, maintaining the stability of the active sites and unobstructed pores. The synergistic use of the two supports balances high surface area / mass transfer (AC) and stability (MOx). The two supports may synergize with the active metal Ni through their respective surface properties (acidity and alkalinity, functional groups) to jointly promote the efficient conduct of complex multi-step reactions (adsorption, cracking, hydrogenation, dehydration). For example, the weakly acidic sites on the support may assist the adsorption of triglycerides or fatty acids and the activation of CO bonds.

[0047] The nickel-based dual-support catalyst prepared in the present invention can directly catalyze the hydrogenation of triglycerides to fatty alcohols. The core of this catalyst lies in the strong hydrogenation and hydrogenolysis capabilities provided by its highly dispersed nickel nanoparticle sites, the macromolecular mass transfer channels provided by the dual-support structure (especially activated carbon), and the overall thermal stability and possible synergistic effects. Together, these promote the cracking of triglycerides into fatty acids and their further efficient conversion into fatty alcohols via the hydrodeoxygenation (HDO) pathway.

[0048] The present invention will be further explained below by means of specific embodiments:

[0049] Example 1

[0050] A method for directly preparing fatty alcohols from oils and fats using a nickel-based dual-support catalyst, comprising the following steps:

[0051] Accurately weigh the Ni salt, activated carbon powder, and zinc oxide based on the target loading (e.g., 1 wt% Ni, activated carbon: zinc oxide = 1:1). The mass of metallic Ni accounts for 1% of the total catalyst mass (Ni + AC + MOx). To prepare 100g of catalyst, 1g of elemental Ni is required. Converted to Ni(NO3)2·6H2O (Ni content ~20.2%), approximately 1g / 0.202≈4.95g is required. Based on a 1:1 activated carbon (AC): zinc oxide mass ratio, to prepare 100g of catalyst (containing 1g Ni), activated carbon + zinc oxide = 99g. At this 1:1 ratio, activated carbon = 49.5g, zinc oxide = 49.5g.

[0052] Dissolve the calculated amount of Ni salt in an appropriate amount of deionized water. The amount of water should be just enough to immerse and wet all the carrier powder to form a stirrable slurry, but not too much to avoid prolonged subsequent drying time. The initial wetness impregnation method is usually adopted. Then, the activated carbon powder and the metal oxide powder are physically mixed in advance. Then, the mixed carrier powder is slowly added to the nickel salt aqueous solution while stirring vigorously to ensure that the solution is evenly absorbed by the carrier to avoid local oversaturation or agglomeration. Continue stirring for 1 hour to allow the metal ions to be fully adsorbed and distributed on the surface and inner pores of the carrier to obtain a mixture.

[0053] The mixture was transferred to a drying oven and dried at 100°C for 12 hours to completely remove physically adsorbed water, prevent the material from splashing or structural damage due to rapid evaporation of water during subsequent calcination, and preliminarily fix the metal salt on the surface of the support to obtain a dry material;

[0054] The dried material is transferred to a muffle furnace, and the temperature is raised to 400°C at a heating rate of 5°C / min and maintained for 4 hours in an air atmosphere to thermally decompose the nickel salt (e.g., nickel nitrate) into the corresponding metal oxide (NiO). The decomposition gas (such as NO2) is carried away by the air flow to obtain a calcined material;

[0055] The calcined material (NiO / AC / MOx in this case) was transferred to a tubular reduction furnace, nitrogen was introduced to purge and replace the air, and then hydrogen was introduced. The temperature was raised to 400°C at a rate of 10°C / min and maintained for 5 hours for reduction activation. After the reduction was completed, the material was cooled to room temperature (or the desired temperature) under a hydrogen atmosphere to obtain a nickel-based dual-support catalyst, which was recorded as 1wt% Ni / ZnO-C.

[0056] 1 g of palm oil, 50 mg of 1 wt% Ni / ZnO-C, and 10 mL of n-hexane were added to the reactor in sequence. Hydrogen was introduced at a flow rate of 3.0 L / min and the reaction was carried out at 280° C. for 12 h. The yield of the obtained fatty alcohol was 84%.

[0057] Example 2

[0058] A method for directly preparing fatty alcohols from oils and fats using a nickel-based dual-support catalyst, comprising the following steps:

[0059] The preparation of nickel-based dual-support catalyst is the same as that in Example 1;

[0060] 1 g of tricaprin, 50 mg of nickel-based dual-support catalyst, and 10 mL of n-hexane were added to the reactor in sequence. The flow rate of hydrogen was 3.0 L / min, and the reaction was carried out at 280° C. for 12 h. The yield of fatty alcohol was 82%.

[0061] Example 3

[0062] A method for directly preparing fatty alcohols from oils and fats using a nickel-based dual-support catalyst, comprising the following steps:

[0063] The preparation of nickel-based dual-support catalyst is the same as that in Example 1;

[0064] 1 g of coconut oil, 50 mg of nickel-based dual-support catalyst, and 10 mL of n-hexane were added to the reactor in sequence. The flow rate of hydrogen was 3.0 L / min. The reaction was carried out at 280° C. for 12 h. The yield of fatty alcohol was 78%.

[0065] Example 4

[0066] A method for directly preparing fatty alcohols from oils and fats using a nickel-based dual-support catalyst, comprising the following steps:

[0067] A nickel-based dual-support catalyst was prepared by referring to the method of Example 1, in which the mass of metal Ni accounted for 0.75% of the total mass of the catalyst (Ni+AC+MOx), and was recorded as 0.75wt%Ni / ZnO-C;

[0068] 1 g of palm oil, 50 mg of 0.75 wt% Ni / ZnO-C, and 10 mL of n-hexane were added to the reactor in sequence. Hydrogen was introduced at a flow rate of 3.0 L / min and the reaction was carried out at 280° C. for 12 h. The yield of the fatty alcohol was 70%.

[0069] Example 5

[0070] A method for directly preparing fatty alcohols from oils and fats using a nickel-based dual-support catalyst, comprising the following steps:

[0071] A nickel-based dual-support catalyst was prepared by referring to the method of Example 1, in which the mass of metal Ni accounted for 0.5% of the total mass of the catalyst (Ni+AC+MOx), and was recorded as 0.5wt%Ni / ZnO-C;

[0072] 1 g of palm oil, 50 mg of 0.5 wt% Ni / ZnO-C, and 10 mL of n-hexane were added to the reactor in sequence. Hydrogen was introduced at a flow rate of 3.0 L / min. The reaction was carried out at 280° C. for 12 h. The yield of the fatty alcohol was 66%.

[0073] Comparative Example 1

[0074] A method for directly preparing fatty alcohols from oils and fats using a nickel-based dual-support catalyst, comprising the following steps:

[0075] The preparation of nickel-based dual-support catalyst is the same as that in Example 1;

[0076] 1 g of palm oil, 50 mg of 1 wt% Ni / ZnO-C, and 10 mL of n-hexane were added to the reactor in sequence. Hydrogen was introduced at a flow rate of 3.0 L / min and the reaction was carried out at 280° C. for 6 h. The yield of the obtained fatty alcohol was 15%.

[0077] Comparative Example 2

[0078] A method for directly preparing fatty alcohols from oils and fats using a nickel-based dual-support catalyst, comprising the following steps:

[0079] The preparation of nickel-based dual-support catalyst is the same as that in Example 1;

[0080] 1 g of palm oil, 50 mg of 1 wt% Ni / ZnO-C, and 10 mL of n-hexane were added to the reactor in sequence. Hydrogen was introduced at a flow rate of 3.0 L / min and the reaction was carried out at 150° C. for 12 h. The yield of the obtained fatty alcohol was 20%.

[0081] Comparative Example 3

[0082] A method for directly preparing fatty alcohols from oils and fats using a nickel-based single-carrier catalyst, comprising the following steps:

[0083] Accurately weigh the Ni salt and activated carbon powder according to the target loading (e.g., 1 wt% Ni). The mass of metallic Ni accounts for 1% of the total mass of the catalyst (Ni + activated carbon). To prepare 100 g of catalyst, 1 g of elemental Ni is required, which, converted to Ni(NO3)2·6H2O (Ni content ~20.2%), requires approximately 1 g / 0.202≈4.95 g. To prepare 100 g of catalyst (containing 1 g Ni), the activated carbon = 99 g.

[0084] Dissolve the calculated amount of Ni salt in an appropriate amount of deionized water. The amount of water should be just enough to immerse and wet all the carrier powder to form a stirrable slurry, but not too much to avoid prolonged subsequent drying time. The initial wetness impregnation method is usually adopted. Then slowly add the activated carbon to the nickel salt aqueous solution while stirring vigorously to ensure that the solution is evenly absorbed by the carrier to avoid local oversaturation or agglomeration. Continue stirring for 1 hour to allow the metal ions to be fully adsorbed and distributed on the surface and inner pores of the carrier to obtain a mixture.

[0085] The mixture was transferred to a drying oven and dried at 100°C for 12 hours to completely remove physically adsorbed water, prevent the material from splashing or structural damage due to rapid evaporation of water during subsequent calcination, and preliminarily fix the metal salt on the surface of the support to obtain a dry material;

[0086] The dried material is transferred to a muffle furnace, and the temperature is raised to 400°C at a heating rate of 5°C / min and maintained for 4 hours in an air atmosphere to thermally decompose the nickel salt (e.g., nickel nitrate) into the corresponding metal oxide (NiO). The decomposition gas (such as NO2) is carried away by the air flow to obtain a calcined material;

[0087] The calcined material (NiO / AC in this case) was transferred to a tubular reduction furnace, nitrogen was introduced to purge and replace the air, and then hydrogen was introduced. The temperature was raised to 400°C at a rate of 10°C / min and maintained for 5 hours for reduction activation. After the reduction was completed, the material was cooled to room temperature (or the desired temperature) under a hydrogen atmosphere to obtain a nickel-based single-support catalyst, which was recorded as 1wt% Ni / C.

[0088] 1 g of palm oil, 50 mg of 1 wt% Ni / C, and 10 mL of n-hexane were added to the reactor in sequence. Hydrogen was introduced at a flow rate of 3.0 L / min and the reaction was carried out at 280° C. for 12 h. The yield of the fatty alcohol was 0%.

[0089] Comparative Example 4

[0090] A method for directly preparing fatty alcohols from oils and fats using a nickel-based single-carrier catalyst, comprising the following steps:

[0091] Accurately weigh the Ni salt and activated carbon powder according to the target loading (e.g., 1 wt% Ni). The mass of metallic Ni accounts for 1% of the total mass of the catalyst (Ni + zinc oxide). To prepare 100 g of catalyst, 1 g of elemental Ni is required, which, converted to Ni(NO3)2·6H2O (Ni content ~20.2%), requires approximately 1 g / 0.202≈4.95 g. To prepare 100 g of catalyst (containing 1 g Ni), zinc oxide = 99 g.

[0092] Dissolve the calculated amount of Ni salt in an appropriate amount of deionized water. The amount of water should be just enough to immerse and wet all the carrier powder to form a stirrable slurry, but not too much to avoid prolonged subsequent drying time. The incipient wetness impregnation method is usually adopted. Then slowly add the metal oxide powder to the nickel salt aqueous solution while stirring vigorously to ensure that the solution is evenly absorbed by the carrier to avoid local oversaturation or agglomeration. Continue stirring for 1 hour to obtain a mixture.

[0093] The mixture was transferred to a drying oven and dried at 100°C for 12 hours to completely remove physically adsorbed water, prevent the material from splashing or structural damage due to rapid evaporation of water during subsequent calcination, and preliminarily fix the metal salt on the surface of the support to obtain a dry material;

[0094] The dried material is transferred to a muffle furnace, and the temperature is raised to 400°C at a heating rate of 5°C / min and maintained for 4 hours in an air atmosphere to thermally decompose the nickel salt (e.g., nickel nitrate) into the corresponding metal oxide (NiO). The decomposition gas (such as NO2) is carried away by the air flow to obtain a calcined material;

[0095] The calcined material (NiO / zinc oxide in this case) was transferred to a tubular reduction furnace, nitrogen was introduced to purge and replace the air, and then hydrogen was introduced. The temperature was raised to 400°C at a rate of 10°C / min and maintained for 5 hours for reduction activation. After the reduction was completed, the material was cooled to room temperature (or the desired temperature) under a hydrogen atmosphere to obtain a nickel-based dual-support catalyst, which was recorded as 1wt% Ni / zinc oxide.

[0096] 1 g of palm oil, 50 mg of 1 wt% Ni / zinc oxide, and 10 mL of n-hexane were added to the reactor in sequence. Hydrogen was introduced at a flow rate of 3.0 L / min and the reaction was carried out at 280° C. for 12 h. The yield of the obtained fatty alcohol was 37%.

[0097] The data from Examples 1-5 demonstrate that the present invention's solution can efficiently catalyze the direct production of fatty alcohols from natural and non-natural oils, with yields exceeding 80%. Comparison of the data from Examples 1 and 4-5 demonstrates that, within a predetermined range, the yield of fatty alcohols increases with increasing Ni nanoparticle loading on the dual-support. Comparison of the data from Example 1 and Comparative Examples 3-4 demonstrates that a nickel-based single-support catalyst prepared using activated carbon alone is unable to catalyze the production of fatty alcohols from oils, and a nickel-based single-support catalyst prepared using zinc oxide alone yields less than half the yield of fatty alcohols from oils compared to Example 1. Comparison of the data from Example 1 and Comparative Example 1 demonstrates that the initial reaction phase (the first 6 hours) primarily involves the production of intermediates, resulting in a low yield of fatty alcohols in Comparative Example 1. A large amount of fatty alcohols is produced in the later stages of the reaction, as shown in Example 1. Comparison of the data from Example 1 and Comparative Example 2 demonstrates that the activity of the nickel-based dual-support catalyst is low at temperatures too low (150°C), resulting in a low yield of fatty alcohols (20%).

[0098] It should be understood that the application of the present invention is not limited to the above examples. For those skilled in the art, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for directly preparing fatty alcohols from oils and fats using a nickel-based dual-support catalyst, characterized in that: Including steps: A nickel-based dual-support catalyst is prepared by mixing a nickel salt aqueous solution, a metal oxide and activated carbon by a co-impregnation method, and sequentially drying, air calcining and hydrogen reduction treatment are performed on the mixture. A nickel-based dual-support catalyst, oil and organic solvent are added to a reactor and hydrogen is introduced. A hydrogenation reaction occurs at a preset temperature to produce fatty alcohols.

2. The method for directly preparing fatty alcohols from grease using a nickel-based dual-support catalyst according to claim 1, wherein: The nickel salt aqueous solution is one or more of nickel nitrate aqueous solution, nickel acetate aqueous solution and nickel chloride aqueous solution; the metal oxide is one or more of aluminum oxide, zirconium oxide, iron oxide, tungsten oxide, titanium oxide, manganese oxide, cobalt oxide and zinc oxide.

3. The method for directly preparing fatty alcohols from grease using a nickel-based dual-support catalyst according to claim 1, wherein: In the nickel-based dual-carrier catalyst, the mass of nickel element accounts for 0.1-20% of the total mass of the nickel-based dual-carrier catalyst.

4. The method for directly preparing fatty alcohols from grease using a nickel-based dual-support catalyst according to claim 1, wherein: In the step of mixing the nickel salt aqueous solution, metal oxide and activated carbon by a co-impregnation method, the mass ratio of the metal oxide to the activated carbon is 1:0.1-10.

5. The method for directly preparing fatty alcohols from grease using a nickel-based dual-support catalyst according to claim 1, wherein: In the step of drying the mixture, the mixture is dried at a temperature of 80-120° C. for 10-20 hours.

6. The method for directly preparing fatty alcohols from grease using a nickel-based dual-support catalyst according to claim 5, wherein: In the step of calcining the mixture in air, the temperature is raised to 350-400° C. at a heating rate of 2-5° C. / min under air atmosphere and maintained for 3-5 hours.

7. The method for directly preparing fatty alcohols from grease using a nickel-based dual-support catalyst according to claim 6, wherein: In the step of performing hydrogen reduction treatment on the mixed mixture, an inert gas is introduced to purge and replace the air, and then hydrogen or a mixture of hydrogen and nitrogen is introduced, and the temperature is raised to 350-400°C at a heating rate of 5-10°C / min and maintained for 3-5 hours. The calcined mixture is reduced and activated to obtain a nickel-based dual-support catalyst.

8. The method for directly preparing fatty alcohols from grease using a nickel-based dual-support catalyst according to claim 1, wherein: The organic solvent is one of n-hexane, n-dodecane and cyclohexane.

9. The method for directly preparing fatty alcohols from grease using a nickel-based dual-support catalyst according to claim 1, wherein: In the step of adding the nickel-based dual-support catalyst, grease and organic solvent into the reactor and introducing hydrogen, the flow rate of the introduced hydrogen is 0.5-5.0 L / min.

10. The method for directly preparing fatty alcohols from oils and fats using a nickel-based dual-support catalyst according to claim 1, wherein: In the step of causing the hydrogenation reaction at a preset temperature, the preset temperature is 200-300° C., and the reaction time is 10-15 hours.

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