CN114570375B - Hydrotalcite-based catalyst, preparation method thereof and application of hydrotalcite-based catalyst in efficient catalytic preparation of vanillin - Google Patents
Hydrotalcite-based catalyst, preparation method thereof and application of hydrotalcite-based catalyst in efficient catalytic preparation of vanillin Download PDFInfo
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Abstract
The invention discloses a hydrotalcite-based catalyst, a preparation method thereof and application thereof in high-efficiency catalytic preparation of vanillin, and belongs to the technical fields of functional catalyst preparation and biomass engineering. The invention firstly prepares Cu containing metal cation by coprecipitation method 2+ 、Mg 2+ And Fe (Fe) 3+ And then roasting in air at 200-800 ℃ to obtain the composite metal oxide catalyst consisting of the three metal ions. The catalyst can efficiently catalyze lignin in biomass materials (such as fir wood powder) to depolymerize to vanillin, and the final vanillin yield is 20.61wt% (calculated based on the lignin content in fir wood powder). The reaction system can directly take wood powder as a raw material, the reaction condition is mild, the catalyst is cheap and easy to prepare, and the catalyst is easy to recycle after the reaction (the recovery rate is higher than 85 percent); in addition, the biomass solid residue obtained after the reaction is mainly carbohydrate such as cellulose, and can be used as pulp, biomass materials, fuel ethanol raw materials and the like with high value.
Description
Technical Field
The invention belongs to the technical field of functional catalyst preparation and biomass engineering, and particularly relates to a hydrotalcite-based catalyst, a preparation method thereof and application thereof in high-efficiency catalytic preparation of vanillin.
Background
Hydrotalcite (LDHs) is an anionic layered double hydroxide material, and the chemical composition can be expressed as M 1-X 2+ M X 3+ (OH) 2 [A n- ] x/n ·mH 2 The O, LDHs material has the advantages that the metal elements of the laminate are dispersed in an atomic level, the composition proportion of the laminate is adjustable, and the intercalation anions are presentThe structural characteristics of the proton exchange, the finite field effect, the structural memory effect and the like are good catalysts or catalyst precursors. The composite metal oxide (MMO) obtained by topological transformation of LDHs through high temperature and other methods has the advantages of excellent adsorption capacity, adjustable acid and alkali on the surface, limiting effect and the like, and can be used as a carrier of a catalyst or directly used as the catalyst for a plurality of reactions.
Vanillin (Vanillin) is an organic compound extracted from the pods of Vanilla (Vanilla planifolia) belonging to the genus Vanilla of the family Orchidaceae, which emits the fragrance of the pods of Vanilla and the aroma of milk, and is an indispensable important raw material for food additives, and is widely used in the fields of life such as tobacco, perfume, cosmetics, daily chemicals, and in rubber, plastics, and pharmaceuticals.
Lignin (Lignin) is one of the three major components of lignocellulosic biomass, containing three basic structural units of p-hydroxypropyl (H), guaiacyl (G) and syringyl (S). The lignin macromolecules contain a large number of aromatic groups and unsaturated bonds, and have great potential in preparing high-added-value aromatic compounds such as vanillin and the like. Lignin is taken as a renewable biomass resource, has the advantages of low cost, wide sources, large yield and the like, and is an ideal organic resource for solving the shortage of fossil resources and environmental pollution in the 21 st century.
In the existing technology for preparing vanillin by catalytic depolymerizing lignin based on a catalytic wet air oxidation method (CWAO), the lignin raw materials are mostly alkali lignin, lignin sulfonate and the like which are obtained by processing, and the lignin structure of the raw materials is inevitably damaged irreversibly in the processing process, so that the yield is lower than about 10-15% when the vanillin is prepared. In recent years, with the development and advancement of Lignin-first strategy, studies have been made to directly use unprocessed Lignin raw materials such as resin extracted wood flour to prepare vanillin by a catalytic wet air oxidation method (cwhao), and the vanillin yield is improved to about 15-20%. The existing technology for preparing vanillin by using lignin still has the following problems: technical research of Lignin-first strategy is in the primary stage, and practical technology is scarce; o used in the reaction 2 The pressure is high, about 1.2MPa, and the safety requirement on reaction equipment is high; liquid phase catalyst (CuSO) for catalytic reactions 4 ,FeSO 4 Etc.) or solid phase catalysts (nano-scale CuO, etc.) cannot be or are difficult to recover, and are reused. The problems of high catalytic reaction cost, serious resource waste, low vanillin production efficiency, reduced operation safety and difficulty in being put into practical industrial application in the prior art are caused, and the problems are to be solved.
For the above reasons, the present application is presented.
Disclosure of Invention
In view of the above-mentioned problems or drawbacks of the prior art, it is an object of the present invention to provide a hydrotalcite-based catalyst, a process for its preparation and its use in the efficient catalytic preparation of vanillin, which solve or at least partially solve the above-mentioned technical drawbacks of the prior art.
In order to achieve the first object of the present invention, the present invention adopts the following technical scheme:
a method for preparing a hydrotalcite-based catalyst, comprising the steps of:
(i) Sodium hydroxide (NaOH) and sodium carbonate (Na) are mixed according to the proportion 2 CO 3 ) Mixing, adding into deionized water, and dissolving to form mixed alkali liquor;
(ii) Dropwise adding the mixed alkali liquor into the mixed metal salt solution at a constant speed under the constant temperature of 60-80 ℃ and stirring condition, and continuously stirring until full reaction is achieved after the dropwise adding is finished; after the reaction is finished, standing, filtering, washing, drying and grinding the obtained precipitate into powder to obtain a catalyst precursor; wherein: the mixed metal salt solution consists of soluble copper salt, soluble magnesium salt, soluble ferric salt and deionized water;
(iii) And roasting the catalyst precursor for 2 hours at the temperature of 200-800 ℃ under the air condition to obtain the hydrotalcite-based catalyst.
Further, in the step (i) of the above technical scheme, the mass ratio of the sodium hydroxide to the sodium carbonate is 1:1-1:2, and more preferably is 5:8.
Further, in the step (i) of the above technical solution, theOH in the mixed alkali solution - The concentration of the ions may be 0.1 to 2mol/L, and more preferably 0.375mol/L.
Further, in the step (ii) of the above technical scheme, the molar ratio of the three metal ions in the mixed metal salt solution, namely Cu 2+ :Mg 2+ :Fe 3+ ＝1.6:3.7:1.0。
Further, in the above-mentioned step (ii), the sum of the concentrations of the respective metal ions in the metal salt solution is preferably 0.1 to 0.5mol/L, more preferably 0.15mol/L, that is, [ Cu ] 2+ ]+[Mg 2+ ]+[Fe 3+ ]＝0.15mol/L。
Further, in the step (ii) of the above technical scheme, the volume ratio of the mixed alkali solution to the mixed metal salt solution is preferably 1:2.
further, in the step (ii) of the above technical scheme, the stirring speed is 400-450 r/min.
Further, in the step (ii) of the above technical scheme, the stirring reaction time is preferably 15 to 30 minutes.
Further, in the step (ii) of the above technical scheme, the standing is preferably carried out at a constant temperature of 60 to 80 ℃ for 1 to 3 hours.
Further, in the step (ii) of the above technical scheme, the soluble copper salt may be at least one of copper nitrate, copper sulfate, copper chloride, and the like; the soluble magnesium salt can be at least one of magnesium nitrate, magnesium chloride, magnesium sulfate and the like; the soluble ferric salt can be at least one of ferric nitrate, ferric chloride, ferric sulfate and the like. In the actual preparation of the catalyst precursor, it is ensured that the anions in the metal salts, i.e. soluble copper salt, soluble magnesium salt and soluble iron salt, are the same, e.g. when the soluble copper salt is copper nitrate, the soluble magnesium salt is magnesium nitrate and the soluble iron salt is ferric nitrate.
Preferably, in the above technical solution, the mixed metal salt solution is a mixed metal nitrate solution, because the nitrate is less soluble in water and is more easily precipitated.
Further, in the above technical scheme, in the step (ii), the calcination temperature of the catalyst precursor is preferably 400 to 800 ℃, more preferably 600 ℃.
A second object of the present invention is to provide a hydrotalcite-based catalyst prepared by the above method.
The third object of the invention is to provide the application of the hydrotalcite-based catalyst prepared by the method in high-efficiency catalytic preparation of vanillin.
A process for preparing vanillin with high yield by using a catalytic wet air oxidation method (CWAO) comprises the following specific steps:
adding NaOH solution into a high-temperature high-pressure reaction kettle, then filling oxygen of 0.1-1.20 Mpa, and continuously adding biomass materials and hydrotalcite-based catalysts into the reaction kettle; heating the reaction kettle to 120-180 ℃ and stirring the mixture at constant temperature for reaction for 0.5-3 hours, centrifuging the product after the reaction is completed, acidifying the obtained liquid phase, centrifuging, extracting the obtained acidified liquid phase, and evaporating to obtain biomass oil rich in vanillin; wherein: the hydrotalcite-based catalyst is prepared by the method.
Further, in the above technical scheme, the concentration of the NaOH solution is preferably 0.5-2.0 mol/L, more preferably 1.0-2.0 mol/L, and most preferably 2.0mol/L.
Further, in the above technical scheme, the pressure of the oxygen is preferably 0.1-0.6 Mpa, and more preferably 0.35Mpa.
Further, according to the technical scheme, the biomass material can be lignin-containing plants, for example, the biomass material can be at least one of wood, wood flour, straw, bark, lignin and the like. The biomass material is preferably a biomass material obtained by resin extraction pretreatment.
Furthermore, according to the technical scheme, the biomass material is preferably fir wood powder, and is more preferably fir wood powder obtained after extraction pretreatment.
Preferably, according to the technical scheme, the extraction pretreatment process specifically comprises the following steps: extracting fir wood powder by using toluene and absolute ethyl alcohol with the volume ratio of 2:1 as an extracting solution at the temperature of 110 ℃ to obtain pretreated fir wood powder.
Further, according to the technical scheme, the mass ratio of NaOH to biomass materials in the reaction system is 5:3.
Further, according to the technical scheme, the mass ratio of the hydrotalcite-based catalyst to the biomass material is 1:40-6:40, and is more preferably 3:40.
Further, according to the technical scheme, the temperature of the constant-temperature reaction is preferably 150 ℃, and the reaction time is preferably 75 minutes.
Further, according to the technical scheme, the stirring speed of the reaction is 400-600 rpm.
Further, according to the technical scheme, the post-treatment process specifically comprises the following steps:
and centrifuging a product obtained by the reaction, separating a solid precipitate (containing unreacted biomass components and a solid catalyst), and separating and recovering the catalyst from the unreacted biomass components through strong magnet adsorption. After solid-liquid separation, dilute H is added into the obtained liquid phase 2 SO 4 The solution, the resulting liquid phase was acidified to ph=2 and the resulting precipitate was centrifuged off. Then adding ethyl acetate into the acidified liquid phase to extract and separate a reaction product, continuously extracting for 2-5 times, and combining extract solutions; removing ethyl acetate by rotary evaporation to obtain biomass oil rich in vanillin.
The mechanism involved in the preparation of the hydrotalcite-based catalyst is as follows:
the invention utilizes a coprecipitation method to mix a mixed solution of sodium hydroxide and sodium carbonate serving as a precipitant with a mixed solution of metal salt in a specific proportion under the condition of constant temperature heating at a certain dropping speed, so as to generate hydroxide precipitates with uniformly distributed components. Stopping stirring, and heating at constant temperature to obtain precipitate, and crystallizing to obtain Cu 2+ 、Fe 3+ 、Mg 2+ Metal cations and OH - 、CO 3 2- An anionic composition of an alkaline layered metal hydroxide, namely a catalyst precursor hydrotalcite. The hydrotalcite which is filtered, washed, dried and ground into powder is roasted for a certain time at 200-800 ℃, and then the hydrotalcite is dehydrated to bind water, and the hydroxide component is dehydrated to become the composite metal oxide catalyst. And precursorsCompared with the prior art, the calcined catalyst has the advantages that the internal alkaline site is exposed, the specific surface area is increased, and a certain hydrotalcite layered structure is reserved, so that the catalyst is beneficial to catalytic reaction.
Compared with the prior art, the invention has the following beneficial effects:
(1) The invention relates to hydrotalcite-based agent and a process for preparing vanillin with high yield by converting biomass material by using a Catalytic Wet Air Oxidation (CWAO) system, which comprises the steps of preparing Cu containing metal cation by a coprecipitation method 2+ 、Mg 2+ And Fe (Fe) 3+ The hydrotalcite precursor is roasted in air at 200-800 ℃ to obtain a composite metal oxide catalyst consisting of the three metal ions; cu in the catalyst 2+ In the reaction of oxidatively depolymerizing biomass material (such as fir wood powder), the oxidation reaction can be accelerated to form phenoxy free radical, fe 3+ Combines with-OOH generated by the reaction, is favorable for the conversion of reaction intermediates to target product vanillin, mg 2+ An alkaline site is mainly provided for the catalytic reaction, which is beneficial to depolymerization of lignin in biomass materials; under the condition of lower oxygen pressure than the traditional process, the catalyst can efficiently catalyze lignin in biomass materials (such as fir wood powder) to depolymerize to generate vanillin, and the final vanillin yield is 20.61wt% (calculated based on the lignin content in fir wood powder). The reaction system can directly take wood powder as a raw material, the reaction condition is mild, the catalyst is cheap and easy to prepare, and the catalyst is easy to recycle after the reaction (the recovery rate is higher than 85 percent); in addition, the biomass solid residue obtained after the reaction is mainly carbohydrate such as cellulose, and can be used as pulp, biomass materials, fuel ethanol raw materials and the like with high value.
(2) The invention directly takes biomass material as raw material, and can prepare vanillin with high yield by using low-cost heterogeneous catalyst under milder reaction condition (lower oxygen pressure and alkali content).
Drawings
FIG. 1 is a process for preparing vanillin in high yield by the Catalytic Wet Air Oxidation (CWAO) method of the invention for preparing hydrotalcite-based catalysts;
in fig. 2: the upper left graph shows the vanillin yield comparison of application example 1 and application examples 5 to 8; the upper right graph shows the vanillin yield comparison of application example 1 and application examples 9 to 10; the lower left graph shows the vanillin yield comparison of application example 1 and application examples 11 to 14; the lower right graph shows the comparison of vanillin yields prepared in application example 1 and application examples 15 to 22;
FIG. 3 is a graph comparing the spectra of the biomass oil and gas phase prepared in application example 1 and comparative example 1;
FIG. 4 shows recovery of Cu from the precipitation of a stock solution after completion of the reaction in application example 1 of the present invention 1.6 Mg 3.7 Fe 1.0 -a flow diagram of an MMO catalyst;
FIG. 5 is a hydrotalcite-based catalyst Cu prepared in example 1 of the present invention 1.6 Mg 3.7 Fe 1.0 -a physical map of MMO;
FIG. 6 is a graph showing comparison of vanillin yields prepared in application example 6 and application examples 23 to 28.
Detailed Description
The invention is described in further detail below by way of examples. The present embodiment is implemented on the premise of the present technology, and a detailed embodiment and a specific operation procedure are now given to illustrate the inventive aspects of the present invention, but the scope of protection of the present invention is not limited to the following embodiments.
The equipment and materials used in the present invention are commercially available or are commonly used in the art. The methods in the following examples are conventional in the art unless otherwise specified.
The vanillin yield calculation formula referred to in the following examples is as follows:
vanillin yield% = [ vanillin yield (g)/(wood flour mass (g)% wood flour lignin content) ] × 100%;
note that: the lignin content of fir powder used in the experiment is 30%.
The catalyst recovery rate calculation formula involved in the following examples is as follows:
catalyst recovery% = mass of catalyst (g) recovered once/mass of catalyst added in a single reaction (g) ×100%.
Example 1
The preparation method of the hydrotalcite-based catalyst in the embodiment specifically comprises the following steps:
(i) 19.5011g sodium hydroxide (NaOH) and 31.0037g sodium carbonate (Na 2 CO 3 ) Sequentially dissolving in deionized water, uniformly mixing, and preparing into 1.3L of mixed alkali liquor;
(ii) The mixed alkali solution is dripped into a solution containing 23.9293g of copper sulfate trihydrate (CuSO) at a stirring speed of 400r/min and a constant temperature of 70℃ at a speed of 2 drops/s 4 ·3H 2 O), 24.9985g of ferric nitrate nonahydrate (Fe (NO) 3 ) 3 ·9H 2 O) and 58.1908g of magnesium nitrate hexahydrate (Mg (NO) 3 ) 2 ·6H 2 O) 2.6L of the mixed metal aqueous solution; stirring for 15min after the dripping is finished; stopping stirring, and standing at 70 ℃ for 2 hours; filtering, washing with distilled water, baking at 80 ℃ for 12 hours, precipitating, and grinding into powder to obtain 19.69g of catalyst precursor;
(ii) Roasting the catalyst precursor for 2 hours at 600 ℃ under the air condition to obtain the hydrotalcite-based catalyst Cu 1.6 Mg 3.7 Fe 1.0 -MMO 9.97g。
Example 2
The preparation method of the hydrotalcite-based catalyst in the embodiment specifically comprises the following steps:
(i) 12.0792g sodium hydroxide (NaOH) and 19.0784g sodium carbonate (Na 2 CO 3 ) Sequentially dissolving in deionized water, uniformly mixing, and preparing into 0.8L of mixed alkali liquor;
(ii) The mixed alkali solution is dripped into a solution containing 14.7239g of copper sulfate trihydrate (CuSO) at a stirring speed of 450r/min and a constant temperature of 70℃ at a speed of 2 drops/s 4 ·3H 2 O), 15.3852g of ferric nitrate nonahydrate (Fe (NO) 3 ) 3 ·9H 2 O) and 36.1268g of magnesium nitrate hexahydrate (Mg (NO) 3 ) 2 ·6H 2 O) 1.6L of the mixed metal aqueous solution; stirring for 15min after the dripping is finished; stopping stirring, and standing at 70 ℃ for 2 hours; filtering, washing with distilled water, baking at 80deg.C for 12 hr, precipitating, and grinding to obtain catalyst precursor 7.86g；
(ii) Roasting the catalyst precursor for 2 hours at 600 ℃ under the air condition to obtain the hydrotalcite-based catalyst Cu 1.6 Mg 3.7 Fe 1.0 -MMO 4.18g。
Example 3
The preparation method of the hydrotalcite-based catalyst of this example is basically the same as that of example 2, except that: in this example, magnesium nitrate hexahydrate (Mg (NO 3 ) 2 ·6H 2 The amount of O) was 58.1908g. The mass of the catalyst precursor and the target product prepared in this example were also substantially the same as in example 2.
Example 4
The preparation method of the hydrotalcite-based catalyst in the embodiment specifically comprises the following steps:
(i) 1.5000g of sodium hydroxide (NaOH) and 2.3848g of sodium carbonate (Na 2 CO 3 ) Sequentially dissolving in deionized water, uniformly mixing, and preparing into 0.1L of mixed alkali liquor;
(ii) The mixed alkali solution is dripped into a solution containing 1.8303g of copper sulfate trihydrate (CuSO) at a stirring speed of 400r/min and a constant temperature of 70℃ at a speed of 2 drops/s 4 ·3H 2 O), 1.9230g of ferric nitrate nonahydrate (Fe (NO) 3 ) 3 ·9H 2 O) and 4.5158g of magnesium nitrate hexahydrate (Mg (NO) 3 ) 2 ·6H 2 O) 0.2L of the mixed metal aqueous solution; stirring for 15min after the dripping is finished; stopping stirring, and standing at 70 ℃ for 2 hours; filtering, washing with distilled water, baking at 80 ℃ for 12 hours, precipitating, and grinding into powder to obtain 1.75g of catalyst precursor;
(ii) Roasting the catalyst precursor for 2 hours at 600 ℃ under the air condition to obtain the hydrotalcite-based catalyst Cu 1.6 Mg 3.7 Fe 1.0 -MMO 1.01g。
Example 5
The preparation method of the hydrotalcite-based catalyst of this example is basically the same as that of example 1, except that: the calcination temperature of the catalyst precursor was 200 ℃.
Example 6
The preparation method of the hydrotalcite-based catalyst of this example is basically the same as that of example 1, except that: the calcination temperature of the catalyst precursor was 300 ℃.
Example 7
The preparation method of the hydrotalcite-based catalyst of this example is basically the same as that of example 1, except that: the calcination temperature of the catalyst precursor was 400 ℃.
Example 8
The preparation method of the hydrotalcite-based catalyst of this example is basically the same as that of example 1, except that: the calcination temperature of the catalyst precursor was 500 ℃.
Example 9
The preparation method of the hydrotalcite-based catalyst of this example is basically the same as that of example 1, except that: the calcination temperature of the catalyst precursor was 700 ℃.
Example 10
The preparation method of the hydrotalcite-based catalyst of this example is basically the same as that of example 1, except that: the calcination temperature of the catalyst precursor was 800 ℃.
Application example 1
The process for preparing vanillin with high yield by using a catalytic wet air oxidation method (CWAO) comprises the following specific steps:
(a) 100g of fir wood powder is extracted by a Soxhlet extractor at 110 ℃ by using toluene and ethanol=2:1 as extraction liquid, so as to obtain pretreated fir wood powder.
(b) Adding 25ml of 2mol/L NaOH into a high-temperature high-pressure reaction kettle, charging 0.35MPa oxygen, continuously taking 1.2000g of fir wood powder of which the resin is extracted in the step (a) and 0.0903g of hydrotalcite-based catalyst prepared in the example 1, adding the fir wood powder and the hydrotalcite-based catalyst into the reaction kettle, reacting for 75min at 150 ℃ under the stirring condition of 600rpm, centrifugally separating and precipitating a product, and adsorbing and recycling the catalyst by a strong magnet; adding dilute H with concentration of 2.3mol/L into liquid phase 2 SO 4 Acidifying the solution to ph=2, and continuing to centrifugally separate the precipitate; adding ethyl acetate with the volume ratio of 1:1 into the obtained acidified liquid phase, extracting and separating a reaction product, continuously extracting for 3 times, and combining extract solutions; removing ethyl acetate by rotary evaporation to obtain main productA biomass oil of vanillin; wherein: the mass of the recovered catalyst was 0.0775g, and the recovery rate of the catalyst was 85.83% and the yield of vanillin was 21.25% by weight.
The calculation formula of the catalyst in this application example is as follows: the catalyst added was 0.0903g, the catalyst recovered was 0.0775g, and the catalyst recovery was% = 0.0775/0.0903 x 100% ≡ 85.83%.
The calculation formula of vanillin yield in this application example is as follows: the mass of the added wood flour is 1.2000g, the yield of vanillin is 0.0762g, and the yield of vanillin is= [ 0.0765/(1.2000 x 0.3) ]x100% ≡21.25%. And (3) injection: the lignin content in the fir powder used in the invention is 30 percent.
Application example 2
The process for preparing vanillin with high yield by using a catalytic wet air oxidation method (CWAO) comprises the following specific steps:
(a) 100g of fir wood powder is extracted by a Soxhlet extractor at 110 ℃ by using toluene and ethanol=2:1 as extraction liquid, so as to obtain pretreated fir wood powder.
(b) Adding 25ml of 2mol/L NaOH into a high-temperature high-pressure reaction kettle, charging 0.35MPa oxygen, continuously taking 1.2001g of fir wood powder of which the resin is extracted in the step (a) and 0.0902g of hydrotalcite-based catalyst prepared in the example 1, adding the obtained mixture into the reaction kettle, reacting for 75min at 150 ℃ under the stirring condition of 600rpm, centrifugally separating and precipitating a product, and adsorbing and recovering the catalyst by a strong magnet; adding dilute H with concentration of 2.3mol/L into liquid phase 2 SO 4 Acidifying the solution to ph=2, and continuing to centrifugally separate the precipitate; adding ethyl acetate with the volume ratio of 1:1 into the obtained acidified liquid phase, extracting and separating a reaction product, continuously extracting for 3 times, and combining extract solutions; removing ethyl acetate by rotary evaporation to obtain biomass oil with vanillin as a main product; wherein: the mass of the recovered catalyst was 0.0765g, and the recovery rate of the catalyst was 84.81% and the yield of vanillin was 20.05%.
Application example 3
The process for preparing vanillin with high yield by using a catalytic wet air oxidation method (CWAO) comprises the following specific steps:
(a) 100g of fir wood powder is extracted by a Soxhlet extractor at 110 ℃ by using toluene and ethanol=2:1 as extraction liquid, so as to obtain pretreated fir wood powder.
(b) Adding 25ml of 2mol/L NaOH into a high-temperature high-pressure reaction kettle, charging 0.35MPa oxygen, continuously taking 1.2005g of fir wood powder of which the resin is extracted in the step (a) and 0.0906g of hydrotalcite-based catalyst prepared in the example 1, adding the obtained mixture into the reaction kettle, reacting for 75min at 150 ℃ under the stirring condition of 600rpm, centrifugally separating and precipitating a product, and adsorbing and recovering the catalyst by a strong magnet; adding dilute H with concentration of 2.3mol/L into liquid phase 2 SO 4 Acidifying the solution to ph=2, and continuing to centrifugally separate the precipitate; adding ethyl acetate with the volume ratio of 1:1 into the obtained acidified liquid phase, extracting and separating a reaction product, continuously extracting for 3 times, and combining extract solutions; removing ethyl acetate by rotary evaporation to obtain biomass oil with vanillin as a main product; wherein: the mass of the recovered catalyst was 0.0771g, and the recovery rate of the catalyst was 85.10% and the yield of vanillin as a product was 21.05% by weight.
Application example 4
The process for preparing vanillin with high yield by using a catalytic wet air oxidation method (CWAO) comprises the following specific steps:
(a) 100g of fir wood powder is extracted by a Soxhlet extractor at 110 ℃ by using toluene and ethanol=2:1 as extraction liquid, so as to obtain pretreated fir wood powder.
(b) Adding 25ml of 2mol/L NaOH into a high-temperature high-pressure reaction kettle, charging 0.35MPa oxygen, continuously taking 1.2007g of fir wood powder of which the resin is extracted in the step (a) and 0.0910g of hydrotalcite-based catalyst prepared in the example 1, adding the fir wood powder and the hydrotalcite-based catalyst into the reaction kettle, reacting for 75min at 150 ℃ under the stirring condition of 600rpm, centrifugally separating and precipitating a product, and adsorbing and recovering the catalyst by a strong magnet; adding dilute H with concentration of 2.3mol/L into liquid phase 2 SO 4 Acidifying the solution to ph=2, and continuing to centrifugally separate the precipitate; adding ethyl acetate with the volume ratio of 1:1 into the obtained acidified liquid phase, extracting and separating a reaction product, continuously extracting for 3 times, and combining extract solutions; removing ethyl acetate by rotary evaporation to obtain biomass oil with vanillin as a main product; wherein: recovery of catalyst qualityThe amount was 0.0782g, and the recovery rate of the catalyst was 85.93% and the yield of vanillin was 20.07%.
Application example 5
A process for preparing vanillin with high yield by catalytic wet air oxidation (cwhao) of this application example is substantially the same as that of application example 1, except that: the reaction time in step (b) of this example was 0.5h.
Application example 6
A process for preparing vanillin with high yield by catalytic wet air oxidation (cwhao) of this application example is substantially the same as that of application example 1, except that: the reaction time in step (b) of this example was 1h.
Application example 7
A process for preparing vanillin with high yield by catalytic wet air oxidation (cwhao) of this application example is substantially the same as that of application example 1, except that: the reaction time in step (b) of this example was 1.5h.
Application example 8
A process for preparing vanillin with high yield by catalytic wet air oxidation (cwhao) of this application example is substantially the same as that of application example 1, except that: the reaction time in step (b) of this example was 2.0h.
Application example 9
A process for preparing vanillin with high yield by catalytic wet air oxidation (cwhao) of this application example is substantially the same as that of application example 1, except that: the reaction temperature in step (b) of this example was 120 ℃.
Application example 10
A process for preparing vanillin with high yield by catalytic wet air oxidation (cwhao) of this application example is substantially the same as that of application example 1, except that: the reaction temperature in step (b) of this example was 180 ℃.
Application example 11
A process for preparing vanillin with high yield by catalytic wet air oxidation (cwhao) of this application example is substantially the same as that of application example 1, except that: in the reaction system of the step (b) of this example, naOH was not added, i.e., the concentration of NaOH was 0mol/L.
Application example 12
A process for preparing vanillin with high yield by catalytic wet air oxidation (cwhao) of this application example is substantially the same as that of application example 1, except that: the concentration of NaOH in the reaction system of step (b) of this example was 0.4mol/L.
Application example 13
A process for preparing vanillin with high yield by catalytic wet air oxidation (cwhao) of this application example is substantially the same as that of application example 1, except that: the concentration of NaOH in the reaction system of step (b) of this example was 1.2mol/L.
Application example 14
A process for preparing vanillin with high yield by catalytic wet air oxidation (cwhao) of this application example is substantially the same as that of application example 1, except that: the concentration of NaOH in the reaction system of step (b) of this example was 1.6mol/L.
Application example 15
A process for preparing vanillin with high yield by catalytic wet air oxidation (cwhao) of this application example is substantially the same as that of application example 1, except that: the reaction system of step (b) of this example was not additionally charged with oxygen, and the reaction was carried out under air conditions.
Application example 16
A process for preparing vanillin with high yield by catalytic wet air oxidation (cwhao) of this application example is substantially the same as that of application example 1, except that: the reaction system of step (b) of this example was charged with 0.1MPa of oxygen.
Application example 17
A process for preparing vanillin with high yield by catalytic wet air oxidation (cwhao) of this application example is substantially the same as that of application example 1, except that: the reaction system of step (b) of this example was charged with 0.2MPa oxygen.
Application example 18
A process for preparing vanillin with high yield by catalytic wet air oxidation (cwhao) of this application example is substantially the same as that of application example 1, except that: the reaction system of step (b) of this example was charged with 0.25MPa oxygen.
Application example 19
A process for preparing vanillin with high yield by catalytic wet air oxidation (cwhao) of this application example is substantially the same as that of application example 1, except that: the reaction system of step (b) of this example was charged with 0.5MPa oxygen.
Application example 20
A process for preparing vanillin with high yield by catalytic wet air oxidation (cwhao) of this application example is substantially the same as that of application example 1, except that: the reaction system of step (b) of this example was charged with 0.75MPa oxygen.
Application example 21
A process for preparing vanillin with high yield by catalytic wet air oxidation (cwhao) of this application example is substantially the same as that of application example 1, except that: the reaction system of step (b) of this example was charged with 1.0MPa of oxygen.
Application example 22
A process for preparing vanillin with high yield by catalytic wet air oxidation (cwhao) of this application example is substantially the same as that of application example 1, except that: the reaction system of step (b) of this example was charged with 1.2MPa of oxygen.
In fig. 2: the upper left graph shows the comparative graph of vanillin yields prepared in application example 1 and application examples 5 to 8, and examined the effect of different reaction times (h) on vanillin yields; the upper right graph shows the comparative graph of vanillin yields prepared in application example 1 and application examples 9 to 10, and examined the effect of different reaction temperatures (. Degree.C.) on vanillin yields; the lower left graph is a comparison graph of vanillin yield prepared in application example 1 and application examples 11 to 14, and is examined on the effect of NaOH concentration (mol/L) on vanillin yield; the lower right graph shows comparative yields of vanillin prepared in application example 1 and application examples 15 to 22, which are examined for O 2 Pressure (MPa) opposite fragranceInfluence of the yield of lanin. As can be seen from FIG. 2, when the reaction time was 1.25h (75 min), the NaOH concentration was 2mol/L, the reaction temperature was 150℃and O 2 The pressure of 0.35MPa is most favorable for the catalytic reaction.
Application example 23
A process for preparing vanillin with high yield by catalytic wet air oxidation (cwhao) of this application example is substantially the same as application example 6, except that: the catalyst used in step (b) of this application example was a hydrotalcite-based catalyst prepared in example 5.
Application example 24
A process for preparing vanillin with high yield by catalytic wet air oxidation (cwhao) of this application example is substantially the same as application example 6, except that: the catalyst used in step (b) of this application example was a hydrotalcite-based catalyst prepared in example 6.
Application example 25
A process for preparing vanillin with high yield by catalytic wet air oxidation (cwhao) of this application example is substantially the same as application example 6, except that: the catalyst used in step (b) of this application example was a hydrotalcite-based catalyst prepared in example 7.
Application example 26
A process for preparing vanillin with high yield by catalytic wet air oxidation (cwhao) of this application example is substantially the same as application example 6, except that: the catalyst used in step (b) of this application example was a hydrotalcite-based catalyst prepared in example 8.
Application example 27
A process for preparing vanillin with high yield by catalytic wet air oxidation (cwhao) of this application example is substantially the same as application example 6, except that: the catalyst used in step (b) of this application example was a hydrotalcite-based catalyst prepared in example 9.
Application example 28
A process for preparing vanillin with high yield by catalytic wet air oxidation (cwhao) of this application example is substantially the same as application example 6, except that: the catalyst used in step (b) of this application example was the hydrotalcite-based catalyst prepared in example 10.
Comparative example 1 (CK group)
A method for producing a biomass oil of this comparative example, which is substantially the same as that of application example 1, differs only in that: this comparative example did not employ any catalyst.
Fig. 3 is a graph comparing the oil and gas phase diagrams of biomass prepared in application example 1 and comparative example 1. As can be seen from fig. 3, the addition of the hydrotalcite-based catalyst according to the present invention significantly favors the formation of vanillin.
FIG. 6 is a graph showing comparison of vanillin yields prepared in application example 6 and application examples 23 to 28. As can be seen from FIG. 6, the catalyst calcined at 600℃gave the highest yield of vanillin, which was the best catalyst.
The technical principle of the present invention is described above in connection with the specific embodiments. These descriptions are intended only to illustrate the principles of the invention and should not be taken in any way as limiting the scope of the invention. Other embodiments of the invention will be apparent to those skilled in the art from consideration of this specification without undue burden.
Claims (7)
1. A process for preparing vanillin in high yield by catalytic wet air oxidation (cwhao), which is characterized in that: the method comprises the following specific steps:
adding NaOH solution into a high-temperature high-pressure reaction kettle, then filling oxygen of 0.1-1.25 Mpa, and continuously adding biomass material and hydrotalcite-based catalyst into the reaction kettle; heating the reaction kettle to 120-180 ℃ and stirring the mixture at constant temperature for reaction for 0.5-3 hours, centrifuging the product after the reaction is completed, acidifying the obtained liquid phase, centrifuging, extracting the obtained acidified liquid phase, and evaporating to obtain biomass oil rich in vanillin; wherein: the preparation method of the hydrotalcite-based catalyst specifically comprises the following steps:
(i) Sodium hydroxide (NaOH) and sodium carbonate (Na) are mixed according to the proportion 2 CO 3 ) Mixing, adding into deionized water, and dissolving to form mixed alkali liquor;
(ii) Dropwise adding the mixed alkali liquor into the mixed metal salt solution at a constant speed under the constant temperature of 60-80 ℃ and stirring condition, and continuously stirring until full reaction is achieved after the dropwise adding is finished; after the reaction is finished, standing, filtering, washing, drying and grinding the obtained precipitate into powder to obtain a catalyst precursor; wherein: the mixed metal salt solution consists of soluble copper salt, soluble magnesium salt, soluble ferric salt and deionized water;
(iii) And roasting the catalyst precursor for 2 hours at the temperature of 200-800 ℃ under the air condition to obtain the hydrotalcite-based catalyst.
2. The process for preparing vanillin with high yield by catalytic wet air oxidation (cwhao) of claim 1, wherein: in the step (i), the mass ratio of the sodium hydroxide to the sodium carbonate is 1:1-1:2; OH in the mixed alkali liquor - The concentration of the ions is 0.1-2 mol/L.
3. The process for preparing vanillin with high yield by catalytic wet air oxidation (cwhao) of claim 1, wherein: in step (ii), cu in the mixed metal salt solution 2+ 、Mg 2+ 、Fe 3+ The molar ratio of (2) is 1.6:3.7:1.0.
4. The process for preparing vanillin with high yield by catalytic wet air oxidation (cwhao) of claim 1, wherein: the concentration of the NaOH solution is 0.5-2.0 mol/L.
5. The process for preparing vanillin with high yield by catalytic wet air oxidation (cwhao) of claim 1, wherein: the pressure of the oxygen is 0.35MPa.
6. The process for preparing vanillin with high yield by catalytic wet air oxidation (cwhao) of claim 1, wherein: the temperature of the constant temperature reaction is 150 ℃ and the reaction time is 75min.
7. The process for preparing vanillin with high yield by catalytic wet air oxidation (cwhao) of claim 1, wherein: the mass ratio of the hydrotalcite-based catalyst to the biomass material is 1:40-6:40.
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