A method for synthesizing hydroxybenzonitrile from lignin-based aromatic aldehyde

Abstract

The present invention discloses a method for preparing hydroxybenzonitrile from a lignin-based aromatic aldehyde, comprising: a nitrilation reaction of the aromatic aldehyde with hydroxylamine hydrochloride to produce an aromatic nitrile; diluting the aromatic nitrile with a solvent to obtain an aromatic nitrile solution; and subjecting the aromatic nitrile to a vapor-phase hydrodeoxygenation reaction under the catalytic action of a molybdenum-based catalyst to produce hydroxybenzonitrile; the carrier of the molybdenum-based catalyst is selected from titanium dioxide, aluminum oxide, silicon dioxide, and activated carbon; and the Mo loading is 5 to 20%. The present invention proposes for the first time a route for preparing hydroxybenzonitrile from a lignin-based aromatic aldehyde, which has fewer steps and less pollution. Using renewable energy lignin as a raw material instead of petrochemical resources to synthesize hydroxybenzonitrile saves resources and alleviates energy shortages. The process of synthesizing aromatic nitrile from the aromatic aldehyde nitrilation is short in time and high in yield, and the use of a Mo-based catalyst is highly active in the vapor-phase hydrodeoxygenation of aromatic nitrile.

Description

Technical Field

[0001] The present invention discloses a method for synthesizing hydroxybenzonitrile from lignin-based aromatic aldehyde, and particularly relates to a method for preparing hydroxybenzonitrile from aromatic aldehyde through two steps of nitrilation and hydrodeoxygenation. Background Art

[0002] Lignin, composed of a large number of aromatic structures, is an ideal resource for producing platform chemicals to replace fossil fuels. As a natural high-molecular-weight aromatic compound, lignin's abundant reactive functional groups, such as hydroxyl, quinone, and aldehyde groups, offer significant conversion advantages and value-added potential. However, lignin's degradation is limited by its complex three-dimensional structure and stubborn resistance to degradation, leaving biorefining technologies, such as its comprehensive utilization, still in the exploratory stage. Therefore, achieving efficient value-added conversion of lignin and fully utilizing the reactive functional groups in its depolymerization products to produce functional chemicals is of great significance.

[0003] Oxidative depolymerization of lignin is a key pathway for lignin degradation. During this reaction, the C-C bonds and ether bonds of lignin are broken, ultimately generating a variety of aromatic compounds rich in reactive functional groups, such as aromatic aldehydes and their derivatives, benzoquinone, and guaiacol. The high-value conversion of lignin oxidative depolymerization products is an effective approach for the comprehensive utilization of lignin. In particular, establishing a synthetic route from lignin-based derivatives to platform chemicals holds significant exploratory value.

[0004] Hydroxybenzonitrile is an important fine chemical raw material for the synthesis of pesticides, pharmaceuticals, dyes, and liquid crystal materials, and possesses enormous economic value. The industrial production of hydroxybenzonitrile originates from petroleum refining and chemical engineering. Propylene phenyl, produced by catalytic cracking of petroleum, is then synthesized into phenol through the cumene method, followed by a series of processes including alkylation, oxidation, and amination. This petroleum-based production route inevitably results in significant resource consumption. Currently, numerous studies have reported on the conversion of aromatic aldehydes into value-added chemicals, biofuels, and high-performance materials through methods such as dehydration and amination, hydrodeoxygenation, and esterification. In particular, the amination and nitrilation of aromatic aldehydes to produce aromatic nitriles can achieve yields exceeding 90% using a one-pot reaction of aromatic aldehydes with hydroxylamine hydrochloride. While the conversion of aromatic aldehydes to aromatic nitriles has achieved excellent results, downstream conversion routes for aromatic nitriles remain elusive. In particular, the conversion of vanillyl nitrile to hydroxybenzonitrile has not been reported. Summary of the Invention

[0005] The present invention provides a method for preparing hydroxybenzonitrile from a wood-based aromatic aldehyde. The method uses hydroxylamine hydrochloride as a nitrogen source to directly nitrilate the aromatic aldehyde to form an aromatic nitrile. The aromatic nitrile is then subjected to vapor-phase hydrodeoxygenation using a Mo metal-doped molybdenum-based catalyst under a suitable hydrogen pressure to produce hydroxybenzonitrile. The molybdenum-based catalyst improves the efficiency of methoxyl removal during the hydrodeoxygenation process, thereby achieving efficient preparation of hydroxybenzonitrile. The aromatic aldehyde raw material of the present invention is obtained by oxidative depolymerization of lignin, a renewable resource. This method provides a new approach for producing hydroxybenzonitrile from alternative petrochemical resources, alleviates energy shortages, and offers a new option for downstream production of high-value platform chemicals from lignin.

[0006] The technical solution adopted in the present invention is:

[0007] A method for preparing hydroxybenzonitrile from lignin-based aromatic aldehyde, wherein the method uses lignin-based aromatic aldehyde as raw material and prepares the hydroxybenzonitrile compound through a two-step process, comprising the following steps:

[0008] Step (1), the aromatic aldehyde reacts with hydroxylamine hydrochloride to produce an aromatic nitrile;

[0009] In step (2), the aromatic nitrile is diluted with a solvent to obtain an aromatic nitrile solution, which is subjected to a gas-phase hydrodeoxygenation reaction under the catalytic action of a molybdenum (Mo)-based catalyst to generate hydroxybenzonitrile.

[0010] In step (1), the aromatic aldehyde is at least one of vanillin and syringaldehyde.

[0011] The aromatic nitrile is at least one of 3-methoxy-4-hydroxybenzonitrile and 3,5-dimethoxy-4-hydroxybenzonitrile.

[0012] Specifically, one selected from formic acid or acetic acid, one selected from sodium formate or sodium acetate, aromatic aldehyde and hydroxylamine hydrochloride are put into a reaction device, the molar ratio of aromatic aldehyde to hydroxylamine hydrochloride is 1:1 to 1:1.25, the molar ratio of aromatic aldehyde to formic acid or acetic acid is 1:1 to 1:1.5, and the molar ratio of aromatic aldehyde to sodium formate or sodium acetate is 1:1 to 1:2.5. The reaction is carried out at a temperature of 80 to 100° C. for 6 to 12 hours. After the reaction is completed, the reaction liquid is cooled to room temperature, the reaction device is immersed in water, excess sodium chloride is added to the reaction liquid for salting out, filtering, and vacuum drying to obtain aromatic nitrile.

[0013] Formic acid or acetic acid acts as both a solvent and a catalyst in the reaction.

[0014] Sodium formate or sodium acetate is alkaline and promotes the intermolecular oxidation reaction during the reaction.

[0015] In step (2), the hydroxybenzonitrile is 3-hydroxybenzonitrile, 4-hydroxybenzonitrile or a mixture thereof.

[0016] The mass ratio of the aromatic nitrile to the molybdenum-based catalyst is 0.2:0.8 to 0.2:1.4, preferably 0.2:1 to 0.2:1.2, and more preferably 0.2:1.

[0017] The solvent for dissolving the aromatic nitrile is one of pyridine, acetonitrile and N,N-dimethylformamide.

[0018] The concentration of the aromatic nitrile solution is 5-20 wt.%, preferably 10 wt.%.

[0019] The carrier of the molybdenum-based catalyst is selected from one of titanium dioxide, aluminum oxide, silicon dioxide and activated carbon, preferably titanium dioxide or aluminum oxide; the loading amount of Mo is 5-20%, preferably 10-20%, more preferably 10%.

[0020] The molybdenum-based catalyst is prepared by an equal volume impregnation method or an ion exchange method.

[0021] The molybdenum-based catalyst is prepared by an equal volume impregnation method: ammonium molybdate is dissolved in water to prepare an ammonium molybdate solution, a carrier is added to the ammonium molybdate solution, an oil bath is performed at a temperature of 80-100°C and a rotation speed of 500 r / min, the solvent is removed, the product is dried at 100°C for 10 hours, ground, calcined in a muffle furnace at 400-600°C for 10 hours, passed through a 60-mesh sieve, and reduced at 300-400°C in a hydrogen atmosphere to obtain the molybdenum-based catalyst.

[0022] The molybdenum-based catalyst is prepared by an ion exchange method: ammonium molybdate is dissolved in water to prepare an ammonium molybdate solution, a hydroxide corresponding to the carrier is added, and ion exchange occurs between the ammonium molybdate and the hydroxide in an oil bath at 80-100°C and a rotation speed of 500 r / min. The solvent is removed, the solution is dried at 105°C for 10 hours, ground, calcined in a muffle furnace at 400-600°C for 10 hours, passed through a 60-mesh sieve, and reduced at 300-400°C in a hydrogen atmosphere to obtain the molybdenum-based catalyst.

[0023] The hydroxide corresponding to titanium dioxide is titanium hydroxide; the hydroxide corresponding to aluminum oxide is aluminum hydroxide; and the hydroxide corresponding to silicon dioxide is silicon hydroxide.

[0024] Before use, the molybdenum-based catalyst is reduced at 300-400° C. in a hydrogen atmosphere.

[0025] The temperature of the hydrodeoxygenation reaction is 350-450°C, preferably 380°C.

[0026] The pressure of the hydrodeoxygenation reaction is 0.1-1 MPa, preferably 0.1-0.5 MPa.

[0027] The present invention has the following advantages:

[0028] 1) This invention proposes for the first time a route for preparing hydroxybenzonitrile from lignin-based aromatic aldehydes, which has fewer steps and less pollution. Using renewable energy lignin as a raw material instead of petrochemical resources to synthesize hydroxybenzonitrile saves resources and alleviates energy shortages.

[0029] 2) The process of synthesizing aromatic nitriles (3-methoxy-4-hydroxybenzonitrile or 3,5-dimethoxy-4-hydroxybenzonitrile) from aromatic aldehydes is short in time and high in yield. The use of Mo-based catalysts has high efficiency in the gas-phase hydrodeoxygenation of aromatic nitriles.

[0030] 3) Biomass resources rich in lignin structure, such as straw, have not been effectively processed. The method of the present invention provides a new option for the downstream high-value conversion of lignin. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a gas-phase catalytic hydrodeoxygenation experimental device; wherein, 1-quartz tube, 2-pyrolysis furnace, 3-injector, 4-condenser.

[0032] Figure 2 The GC-MS component analysis results of the gas-phase catalytic hydrodeoxygenation product of 3-methoxy-4-hydroxybenzonitrile in Example 4 are shown.

[0033] Figure 3 These are the GC-MS component analysis results of the gas-phase catalytic hydrodeoxygenation product of 3,5-dimethoxy-4-hydroxybenzonitrile in Example 5. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is further described below through specific embodiments.

[0035] Example 1

[0036] One-pot Nitrilation of Vanillin to 3-Methoxy-4-Hydroxybenzonitrile

[0037] 5.75 g (125 mmol) of formic acid, 6.8 g (100 mmol) of sodium formate, 7.6 g (50 mmol) of vanillin and 4.375 g (62.5 mmol) of hydroxylamine hydrochloride were added to a 200 mL beaker and reacted in an 80 ° C water bath for 6 h. The reaction solution was cooled to room temperature and the beaker was immersed in water. An excess of (5 g) of sodium chloride was added to the reaction solution for salting out. After all the product was precipitated, it was filtered and the filter cake was vacuum dried to obtain 3-methoxy-4-hydroxybenzonitrile.

[0038] The components were determined and the yield was calculated using gas chromatography-mass spectrometry (GC-MS) and gas chromatography using an internal standard method. The results showed that the yield of 3-methoxy-4-hydroxybenzonitrile was 92.8% and the conversion rate of vanillin was 100%.

[0039] GC-MS detection conditions: Agilent 7890B-5977B, HP-5MS column, initial temperature of 40 °C, heating to 330 °C at 10 °C / min, and holding for 5 min.

[0040] Gas chromatography detection conditions: Shimadzu GC 2010 Plus, HP-5 column, initial temperature of 40 °C, heating at 10 °C / min to 330 °C, and holding for 5 min.

[0041] Example 2

[0042] One-pot Nitrilation of Syringaldehyde to 3,5-Dimethoxy-4-hydroxybenzonitrile

[0043] In a 200 mL beaker, 5.75 g (125 mmol) of formic acid, 6.8 g (100 mmol) of sodium formate, 9.1 g (50 mmol) of syringaldehyde and 4.375 g (62.5 mmol) of hydroxylamine hydrochloride were added. The mixture was reacted in an 80 ° C water bath for 6 h. The reaction solution was cooled to room temperature, and the beaker was immersed in water. An excess of (5 g) of sodium chloride was added to the reaction solution for salting out. After all the product was precipitated, it was filtered and the filter cake was vacuum dried to obtain 3,5-dimethoxy-4-hydroxybenzonitrile.

[0044] The components were determined and the yield was calculated using gas chromatography-mass spectrometry (GC-MS) and gas chromatography analysis (test conditions were the same as in Example 1) using the internal standard method. The results showed that the yield of 3,5-dimethoxy-4-hydroxybenzonitrile was 90.2% and the conversion rate of syringaldehyde was 100%.

[0045] Example 3

[0046] Mo is used as a loading metal and one of titanium dioxide, aluminum oxide, silicon dioxide and activated carbon is used as a carrier. An equal volume impregnation method or an ion exchange method is used to prepare a Mo-based catalyst with a Mo loading amount of 5-20%.

[0047] Equal-volume impregnation method: Using ammonium molybdate as the source of metallic Mo in the Mo-based catalyst, ammonium molybdate was first dissolved in 200 mL of deionized water. Then, catalyst support solid powders (titanium dioxide, aluminum oxide, silicon dioxide, activated carbon) were added and the mixture was in an oil bath under mild conditions (80°C, 500 rpm). After the oil bath, the water was evaporated using a rotary evaporator, and the mixture was dried in a drying oven at 100°C for 10 hours. The mixture was ground and calcined in a muffle furnace at 500°C for 10 hours. The mixture was then passed through a 60-mesh sieve and reduced in a pyrolysis furnace at 400°C under a hydrogen atmosphere at 0.1 MPa for 2 hours.

[0048] Table 1. Mo-based catalysts prepared by equal volume impregnation method

[0049]

[0050]

[0051] Ion exchange method: Using ammonium molybdate as the source of metallic Mo in the Mo-based catalyst, ammonium molybdate is first dissolved in 200 mL of deionized water. The corresponding hydroxides (titanium hydroxide, aluminum hydroxide, silicon hydroxide) of the catalyst support (titanium dioxide, aluminum oxide, silicon dioxide) are then added. Ion exchange occurs between the ammonium molybdate and the hydroxides under mild conditions (80°C, 500 rpm) in an oil bath. After the oil bath, water is evaporated using a rotary evaporator, and the product is dried in a drying oven at 105°C for 10 hours, ground, and calcined in a muffle furnace at 500°C for 10 hours. The product is then passed through a 60-mesh sieve and reduced in a pyrolysis furnace at 400°C and 0.1 MPa of hydrogen for 2 hours.

[0052] Table 2. Mo-based catalysts prepared by ion exchange method

[0053]

[0054] Example 4

[0055] The reaction raw materials 3-methoxy-4-hydroxybenzonitrile and 3,5-dimethoxy-4-hydroxybenzonitrile were respectively dissolved in pyridine to prepare raw material solutions with a concentration of 10 wt.%.

[0056] Hydrodeoxygenation experiment: Figure 1 Shown, select the Mo / TiO with 10% metal Mo loading as catalyst (prepared by embodiment 3 equal volume impregnation method). Take 1g Mo / TiO , pack into quartz tube and form fixed-bed reactor, quartz tube is arranged in pyrolysis furnace, guarantee the Mo / TiO in quartz tube Catalyst is positioned at the pyrolysis zone of reactor, quartz tube upper and lower ends stretch out pyrolysis furnace respectively, feed conduit one end is connected with the syringe that raw material is housed, one end stretches in quartz tube, push raw material into quartz tube and carry out catalytic reaction by controlling syringe pump, quartz tube lower end is connected with condensing tube and is used to collect liquid product. Before reaction starts, first pass into N 2 get rid of the air in the quartz tube, then pass into H with flow velocity 200mL / min in quartz tube 2 make reaction pressure maintain 0.1MPa, pyrolysis furnace is warming up to 380 ℃ of reaction temperature by programmed temperature (20 ℃ / min). The injection pump was turned on and the raw material solution was pumped into the fixed bed reactor at a mass ratio of the reaction raw material to the catalyst of 0.2:1. The reaction raw material was reacted under the action of the catalyst for 30 minutes. The quartz tube and condenser were taken out and allowed to cool to room temperature. The liquid product in the condenser was collected with methanol, and the product composition was analyzed to determine the yield.

[0057] GC-MS and detection conditions: Agilent 7890B-5977B, HP-5MS column, initial temperature of 40 °C, heating at 10 °C / min to 330 °C, and holding for 5 min.

[0058] Gas chromatography detection conditions: Shimadzu GC 2010 Plus, HP-5 column, initial temperature of 40 °C, heating to 330 °C at a rate of 10 °C / min, and maintaining for 5 min.

[0059] The GC-MS analysis results of the products of gas phase catalytic hydrodeoxygenation of 3-methoxy-4-hydroxybenzonitrile are shown in Figure 2 The GC-MS analysis results of the gas phase catalytic hydrodeoxygenation products of 3,5-dimethoxy-4-hydroxybenzonitrile are shown in Figure 3 The reaction raw material conversion rate and product selectivity are shown in Table 3.

[0060] Table 3. Reaction raw material conversion rate and product selectivity

[0061]

[0062] Example 5

[0063] The effects of different temperatures on the hydrodeoxygenation reaction were tested.

[0064] 3-Methoxy-4-hydroxybenzonitrile was used as the reaction raw material, and pyridine was used to prepare a raw material solution with a concentration of 10 wt.%. Mo / TiO2 with a metal Mo loading of 10% was selected as the catalyst (prepared by the equal volume impregnation method in Example 3).

[0065] Hydrodeoxygenation experimental device is with embodiment 4, weighs the Mo / TiO after 1g reduction, is loaded into quartz tube and forms fixed-bed reactor.Before reaction starts, first pass into N2The air in quartz tube is excluded, then H is passed into quartz tube with flow velocity 200mL / min. Make pressure in quartz tube be maintained at 0.1MPa, pyrolysis furnace is warmed up to reaction temperature (350,380,400,450 DEG C) by programmed temperature (20 DEG C / min).Open syringe pump, according to the mass ratio of 3-methoxy 4-hydroxybenzonitrile and catalyst, be 0.2:1, material solution is pumped into fixed-bed reactor, when reaction pressure is 0.1MPa, reaction raw materials react 30min under catalyst action.Take out quartz tube and condenser tube, be placed to room temperature, collect the liquid product in condenser tube with methanol, analyze and determine product composition and calculate yield.

[0066] The results, shown in Table 4, demonstrate the significant influence of reaction temperature on the hydrodeoxygenation reaction. As the reaction temperature increases, the feedstock conversion increases, reaching 100%. However, the sum of the selectivities for 4-hydroxybenzonitrile and 3-hydroxybenzonitrile increases first and then decreases with increasing temperature. The highest selectivity for both products is achieved at a reaction temperature of 380°C.

[0067] Table 4. Effect of reaction temperature on raw material conversion and product selectivity

[0068]

[0069] Example 6

[0070] The effects of different catalyst supports on the hydrodeoxygenation reaction were tested.

[0071] 3-Methoxy-4-hydroxybenzonitrile was used as the reaction raw material, and pyridine was used to prepare a raw material solution with a concentration of 10 wt.%. Different supported catalysts with a metal Mo loading of 10% were selected (all prepared by the equal volume impregnation method in Example 3).

[0072] Hydrodeoxygenation experimental device is with embodiment 4, weighs the catalyst after 1g reduction, is loaded into quartz tube and forms fixed-bed reactor.Before reaction starts, N is first passed into quartz tube to exclude the air in quartz tube, then H is passed into quartz tube with 200mL / min and pressure is maintained at 0.1MPa, pyrolysis furnace is raised to reaction temperature (380 DEG C) by programmed temperature (20 DEG C / min).Open syringe pump, according to the mass ratio of 3-methoxy 4-hydroxybenzonitrile and catalyst, is 0.2:1, material solution is pumped into fixed-bed reactor, when reaction pressure is 0.1MPa, reaction raw materials react 30min under catalyst action.Take out quartz tube and condenser tube, be placed to room temperature, collect the liquid product in condenser tube with methanol, analyze and determine product composition and calculate yield.

[0073] The results are shown in Table 5, indicating that the catalyst support has a certain influence on the hydrodeoxygenation activity of Mo-based catalysts. Mo-based catalysts supported on titanium dioxide, aluminum oxide, silicon dioxide, and activated carbon all catalyzed the hydrodeoxygenation of 3-methoxy-4-hydroxybenzonitrile to produce 4-hydroxybenzonitrile and 3-hydroxybenzonitrile, with the combined selectivity of 4-hydroxybenzonitrile and 3-hydroxybenzonitrile exceeding 50%. When TiO2 was used as the support for metallic Mo, the feedstock conversion was the highest, but there was no significant difference compared to the catalyst prepared using Al2O3 as the support. When Al2O3 was used as the support for metallic Mo, the combined selectivity of 4-hydroxybenzonitrile and 3-hydroxybenzonitrile was the highest, but there was no significant difference compared to the catalyst prepared using TiO2 as the support.

[0074] Table 5. Effect of catalyst support on feedstock conversion and product selectivity

[0075]

[0076] Example 7

[0077] The effects of different catalyst dosages on the hydrodeoxygenation reaction were tested.

[0078] 3-Methoxy-4-hydroxybenzonitrile was used as the reaction raw material, and pyridine was used to prepare a raw material solution with a concentration of 10 wt.%. Mo / TiO2 with different masses and a metal Mo loading of 10% was selected as the catalyst (prepared by the equal volume impregnation method in Example 3).

[0079] Hydrodeoxygenation experimental device is with embodiment 4, weighs the catalyst after different mass reduction, is loaded into quartz tube and forms fixed-bed reactor.Before reaction starts, N is first passed into quartz tubeThe air in quartz tube is excluded, then H is passed into quartz tube with flow velocity 200mL / minMake pressure maintenance at 0.1MPa, pyrolysis furnace is warmed up to reaction temperature (380 DEG C) by programmed temperature (20 DEG C / min).Open injection pump, according to the mass ratio of 3-methoxy 4-hydroxybenzonitrile and catalyst, be respectively 0.2:0.8,0.2:1,0.2:1.2,0.2:1.4, material solution is pumped into fixed-bed reactor, when reaction pressure is 0.1MPa, reaction raw materials react 30min under catalyst action.Take out quartz tube and condenser tube, be placed to room temperature, collect the liquid product in condenser tube with methanol, analyze and determine product composition and calculate yield.

[0080] The results, shown in Table 6, demonstrate that catalyst dosage has a significant impact on the hydrodeoxygenation reaction. Good feedstock conversion and product selectivity were achieved at a 3-methoxy-4-hydroxybenzonitrile to catalyst ratio of 0.2:0.8 to 0.2:1.4. The highest feedstock conversion was achieved at a 3-methoxy-4-hydroxybenzonitrile to catalyst ratio of 0.2:1.4, while the combined selectivity for 4-hydroxybenzonitrile and 3-hydroxybenzonitrile was highest at a 3-methoxy-4-hydroxybenzonitrile to catalyst ratio of 0.2:1. Taking all factors into consideration, a 3-methoxy-4-hydroxybenzonitrile to catalyst ratio of 0.2:0.1 to 0.2:1.2 was preferred.

[0081] Table 6. Effect of catalyst dosage on feed conversion and product selectivity

[0082]

[0083] Example 8

[0084] The effect of Mo / TiO2 with different metal Mo loading amounts on the hydrodeoxygenation reaction was tested.

[0085] 3-Methoxy-4-hydroxybenzonitrile was used as the reaction raw material, and pyridine was used to prepare a raw material solution with a concentration of 10 wt.%. Mo / TiO2 catalysts with different metal Mo loadings were selected (all prepared by the equal volume impregnation method in Example 3).

[0086] Hydrodeoxygenation experimental device is with embodiment 4, weighs the catalyst after 1g reduction, is loaded into quartz tube and forms fixed-bed reactor.Before reaction starts, N is first passed into quartz tubeThe air in quartz tube is excluded, then H is passed into quartz tube with flow velocity 200mL / minMake pressure maintenance at 0.1MPa, pyrolysis furnace is warmed up to reaction temperature (380 DEG C) by programmed temperature (20 DEG C / min).Open injection pump, according to the mass ratio of 3-methoxyl group 4-hydroxybenzonitrile and catalyst, it is 0.2:1, stock solution is pumped into fixed-bed reactor, when reaction pressure is 0.1MPa, reaction raw materials react 30min under catalyst action, take out quartz tube and condenser tube, be placed to room temperature, collect the liquid product in condenser tube with methanol, analyze and determine product composition and calculate yield.

[0087] The results, shown in Table 7, demonstrate that the Mo loading significantly influences the hydrodeoxygenation reaction. Good feedstock conversion and product selectivity are achieved at Mo loadings of 10% to 20%. The highest feedstock conversion is achieved at a Mo loading of 20%, while the combined selectivity for 4-hydroxybenzonitrile and 3-hydroxybenzonitrile is highest at a Mo loading of 10%.

[0088] Table 7. Effect of Mo metal loading on feedstock conversion and product selectivity

[0089]

[0090] Example 9

[0091] The effect of different hydrogen pressures on hydrodeoxygenation was tested.

[0092] 3-Methoxy-4-hydroxybenzonitrile was used as the reaction raw material, and pyridine was used to prepare a raw material solution with a concentration of 10 wt.%. Mo / TiO2 with a metal Mo loading of 10% was selected as the catalyst (prepared by the equal volume impregnation method in Example 3).

[0093] Hydrodeoxygenation experimental device is with embodiment 4, weighs the catalyst after 1g reduction, is loaded into quartz tube and forms fixed-bed reactor.Before reaction starts, N is first passed into quartz tube to exclude the air in quartz tube, then H is passed into quartz tube with flow velocity 200mL / min, pyrolysis furnace is warmed up to reaction temperature (380 DEG C) by programmed temperature (20 DEG C / min).Open syringe pump, according to the mass ratio of 3- methoxy 4- hydroxybenzonitrile and catalyst, it is 0.2:1, raw material solution is pumped into fixed-bed reactor, and under reaction pressure, is respectively 0.1,0.5,0.8,1MPa, reaction raw materials react 30min under catalyst action.Take out quartz tube and condenser tube, be placed to room temperature, collect the liquid product in condenser tube with methanol, analyze and determine product composition and calculate yield.

[0094] The results, shown in Table 8, demonstrate the significant influence of reaction pressure on the hydrodeoxygenation reaction. At reaction pressures between 0.1 and 1 MPa, both feedstock conversion and product selectivity achieved excellent results. At hydrogen pressures between 0.8 and 1 MPa, feedstock conversion reached 100%, and the combined selectivity for 4-hydroxybenzonitrile and 3-hydroxybenzonitrile exceeded 50%. The combined selectivity for 4-hydroxybenzonitrile and 3-hydroxybenzonitrile was highest at a hydrogen pressure of 0.1 MPa.

[0095] Table 8. Effect of hydrogen pressure on feed conversion and product selectivity

[0096]

Claims

1. A method for preparing hydroxybenzonitrile from a wood-based aromatic aldehyde, characterized in that: The following steps are involved: In step (1), an aromatic aldehyde reacts with hydroxylamine hydrochloride to generate an aromatic nitrile; the aromatic aldehyde is at least one of vanillin and syringaldehyde; the aromatic nitrile is at least one of 3-methoxy-4-hydroxybenzonitrile and 3,5-dimethoxy-4-hydroxybenzonitrile; In step (2), the aromatic nitrile is diluted with a solvent to obtain an aromatic nitrile solution, and a gas-phase hydrodeoxygenation reaction occurs under the catalytic action of a molybdenum-based catalyst to produce hydroxybenzonitrile; wherein the hydroxybenzonitrile is one of 3-hydroxybenzonitrile, 4-hydroxybenzonitrile, or a mixture thereof; the carrier of the molybdenum-based catalyst is selected from one of titanium dioxide, aluminum oxide, silicon dioxide, and activated carbon; and the Mo loading is 5 to 20%.

2. The method for preparing hydroxybenzonitrile from wood-based aromatic aldehyde according to claim 1, wherein: In step (2), the mass ratio of the aromatic nitrile to the molybdenum-based catalyst is 0.2:0.8 to 0.2:1.

4.

3. The method for preparing hydroxybenzonitrile from wood-based aromatic aldehyde according to claim 2, characterized in that: In step (2), the mass ratio of the aromatic nitrile to the molybdenum-based catalyst is 0.2:1 to 0.2:1.

2.

4. The method for preparing hydroxybenzonitrile from wood-based aromatic aldehyde according to claim 3, characterized in that: In step (2), the mass ratio of the aromatic nitrile to the molybdenum-based catalyst is 0.2:

1.

5. The method for preparing hydroxybenzonitrile from wood-based aromatic aldehyde according to claim 1, characterized in that: In step (2), the solvent is one of pyridine, acetonitrile and N,N-dimethylformamide.

6. The method for preparing hydroxybenzonitrile from wood-based aromatic aldehyde according to claim 1, characterized in that: In step (2), the concentration of the aromatic nitrile solution is 5 to 20 wt.%.

7. The method for preparing hydroxybenzonitrile from wood-based aromatic aldehyde according to claim 6, characterized in that: In step (2), the concentration of the aromatic nitrile solution is 10 wt.%.

8. The method for preparing hydroxybenzonitrile from wood-based aromatic aldehyde according to claim 1, characterized in that: In step (2), the carrier of the molybdenum-based catalyst is titanium dioxide or aluminum oxide.

9. The method for preparing hydroxybenzonitrile from wood-based aromatic aldehyde according to claim 8, characterized in that: In step (2), the carrier of the molybdenum-based catalyst is titanium dioxide.

10. The method for preparing hydroxybenzonitrile from wood-based aromatic aldehyde according to claim 1 or 8, characterized in that: In step (2), the loading amount of Mo is 10-20%.

11. The method for preparing hydroxybenzonitrile from wood-based aromatic aldehyde according to claim 10, characterized in that: In step (2), the loading amount of Mo is 10%.

12. The method for preparing hydroxybenzonitrile from wood-based aromatic aldehyde according to claim 1, characterized in that: In step (2), the temperature of the hydrodeoxygenation reaction is 350-450°C.

13. The method for preparing hydroxybenzonitrile from wood-based aromatic aldehyde according to claim 12, characterized in that: In step (2), the temperature of the hydrodeoxygenation reaction is 380°C.

14. The method for preparing hydroxybenzonitrile from wood-based aromatic aldehyde according to claim 1, characterized in that: In step (2), the pressure of the hydrodeoxygenation reaction is 0.1 to 1 MPa.

15. The method for preparing hydroxybenzonitrile from wood-based aromatic aldehyde according to claim 14, characterized in that: In step (2), the pressure of the hydrodeoxygenation reaction is 0.1-0.5 MPa.

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