Method for effectively improving purity of linalool product

Abstract

The invention provides a method for effectively improving the purity of a linalool product, which comprises the following steps of: adding a catalyst into a reaction solution for preparing linalool through selective hydrogenation of dehydrolinalool, catalyzing an incompletely converted dehydrolinalool raw material to carry out isomerization reaction, generating 3, 7-dimethyl-3, 6-octadiene-2-ketone and citral of which the boiling point is greatly different from that of linalool, and separating the 3, 7-dimethyl-3, 6-octadiene-2-ketone and citral. The linalool is produced through selective hydrogenation of the dehydrolinalool, a small amount of dehydrolinalool raw materials are left in the obtained hydrogenation reaction liquid, the boiling points of the dehydrolinalool and the linalool are very close, a self-cyclization reaction is easily generated, and cyclization impurities with the boiling point close to that of the linalool are generated; therefore, rectification and purification of linalool have the defects of high number of tower plates, large reflux ratio, high product loss and the like. According to the method, a small amount of catalyst is added into the reaction liquid to catalyze isomerization conversion of residual dehydrolinalool into citral and other high-boiling-point impurities, and compared with a rectification scheme adopted by a traditional process, the method has the advantages that rectification energy consumption and product loss are effectively reduced, and a linalool product with higher purity is obtained at lower separation cost.

Description

Technical Field

[0001] The invention belongs to the field of fine chemicals and flavors and fragrances, and particularly relates to a method for adding a small amount of catalyst into a reaction solution for preparing linalool by selectively hydrogenating dehydrolinalool, catalyzing the isomerization of incompletely converted dehydrolinalool into impurities having a large difference in boiling point from linalool in a distillation tower bottom, thereby realizing efficient separation of impurities related to dehydrolinalool and improving the purity of the linalool product. Background Art

[0002] Linalool is a colorless oily liquid at room temperature, insoluble in water, and miscible with common solvents such as ethanol, ether, ethyl acetate, and tetrahydrofuran. Linalool has a sweet, typical floral and woody aroma, and a fresh lily scent. Linalool can be used to prepare various floral flavors such as lily, orange blossom, lilac, lavender, and rose. Linalool can be used not only in floral flavors, but also in non-floral flavors such as fruity, fresh, woody, aldehyde, oriental, and amber. It can also be used to prepare artificial essential oils such as orange leaves, bergamot, lavender, and lavender oil. It can then be used in perfumes, daily chemicals, cleaning products, food, and other fields. According to relevant statistics, linalool is one of the most commonly used spices in perfume, daily chemicals, and other flavor formulas.

[0003] Linalool from different sources has slightly different aromas. Natural linalool separated from essential oils is generally more fragrant and penetrating, but it is often not a single aroma; while synthetic linalool has a higher purity, a relatively single component, and its aroma is generally purer. The aroma of natural linalool from different plants is also different. The aroma of linalool separated from rosewood oil is a fragrant and sweet woody green aroma; the incidental floral fragrance isolated from white orchid leaf oil may be due to trace amounts of floral components; linalool separated from camphor oil often carries trace amounts of camphor and other scents, and the aroma is relatively poor. In addition to being used directly as a fragrance raw material, linalool is also an important synthetic intermediate that can be used to synthesize a variety of other fragrance products, such as nerolidol, tetrahydrolinalool, linalyl acetate, etc. Linalool is also a key intermediate in the synthesis of tocopherol and tocopherol acetate.

[0004]

[0005] As shown above, the selective triple bond hydrogenation of dehydrolinalool can conveniently obtain linalool. This reaction generally uses Lindella catalyst. The main side reaction is the further hydrogenation of linalool to form dihydrolinalool. Too much dihydrolinalool will reduce the product yield; so in the actual reaction, the reaction needs to be terminated in time. In addition to the main product linalool, the main impurity in the reaction liquid is a small amount of residual raw material dehydrolinalool. The boiling point of dehydrolinalool is 198.0℃, and the boiling point of linalool is 196.3℃. The boiling points of the two are very close, and distillation separation is extremely difficult; and dehydrolinalool will also undergo intramolecular cyclization under heating conditions to generate a five-membered cyclic alcohol by-product. The boiling point of this by-product is also similar to that of linalool, which further increases the difficulty of purifying the linalool product; so at present, the distillation and purification of linalool requires a very high number of plates and reflux ratio, which not only causes a lot of material loss, but also high energy consumption.

[0006]

[0007] In summary, linalool is an important fragrance product, which can be obtained by selective hydrogenation of dehydrolinalool. During the reaction, dehydrolinalool is generally not completely converted, and a small amount of dehydrolinalool raw material will remain in the product liquid. Since dehydrolinalool and linalool have similar boiling points, and cyclization side reactions will occur during the distillation process to generate cyclization by-products, the number of distillation separation plates of linalool is relatively high, resulting in high product losses and high energy consumption. Therefore, it is currently necessary to develop a new linalool distillation and purification method to improve the linalool distillation separation yield and reduce separation energy consumption. Summary of the invention

[0008] The purpose of the present invention is to provide a method for effectively improving the purity of linalool products, by adding a small amount of catalyst to the dehydrolinalool hydrogenation reaction liquid, catalyzing the residual dehydrolinalool to be converted into impurities that are easier to separate, thereby achieving the improvement of the purity of the linalool product. The present invention is novel in concept, converts the difficult-to-separate dehydrolinalool into easily separable citral and 3,7-dimethyl-3,6-octadiene-2-one, and completes the relevant conversion in the distillation process. The method has the advantages of simple operation, mild conditions, small amount of catalyst, etc., and has good potential application value.

[0009] In order to achieve the above objectives and technical effects, the present invention adopts the following technical solutions:

[0010] A method for effectively improving the purity of a linalool product, specifically comprising: adding a catalyst to a reaction solution in which dehydrolinalool is selectively hydrogenated to prepare linalool, catalyzing an isomerization reaction of the incompletely converted dehydrolinalool raw material to generate 3,7-dimethyl-3,6-octadien-2-one and citral, which have boiling points that are significantly different from those of linalool, thereby achieving efficient separation and effectively improving the purity of the linalool product.

[0011] The reaction route is shown below:

[0012]

[0013] In the present invention, the content of the raw material dehydrolinalool in the dehydrolinalool selective hydrogenation reaction liquid is 0.05-0.5wt%.

[0014] In the present invention, the catalyst is composed of a metal catalyst and an acid catalyst; the metal catalyst is obtained by in-situ complexation of a metal salt and a ligand, the metal salt may be but is not limited to a gold salt, a copper salt, a silver salt, etc., preferably, the metal salt is gold chloride, gold bromide, chlorocarbonyl gold, tetrachloroauric acid, dimethyl (acetylacetone) gold, dimethyl (trifluoroacetylacetone) gold, triphenylphosphine chlorogold, silver tetrafluoroborate, silver trifluoromethanesulfonate, silver bis(trifluoromethanesulfonylimide), silver bis(trifluoromethanesulfonylimide), silver hexafluorophosphate, cuprous tetrafluoroborate, copper tetrafluoroborate, trifluoromethanesulfonate, copper bis(trifluoromethanesulfonylimide), cupric chloride, cuprous chloride, etc., and the amount of the metal salt is 0.001-0.01wt% of the mass of the reaction solution;

[0015] In the present invention, the ligand may be, but is not limited to, a phosphine ligand, a nitrogen-phosphorus ligand, a pyridine ligand, a sulfur ligand, and the like. Preferably, the ligand is triphenylphosphine, tri(3-methylphenyl)phosphine, tri(4-methylphenyl)phosphine, 1,2-diphenylphosphinoethane, 1,3-diphenylphosphinopropane, 1,4-diphenylphosphinobutane, 1,8-bis(diphenylphosphino)naphthalene, tributylphosphine, tricyclohexylphosphine, tricyclopentylphosphine, 2-(diadamantylphosphine)biphenyl, 1-[2-bis-tert-butylphosphinophenyl]-3,5-diphenyl-1-H pyrazole, and the like. The amount of the ligand used is 0.002-0.02wt% of the mass of the reaction solution.

[0016] In the present invention, the acid catalyst can be but not limited to benzenesulfonic acid, p-toluenesulfonic acid, p-chlorobenzenesulfonic acid, p-bromobenzenesulfonic acid, naphthalenesulfonic acid, methanesulfonic acid, ethanesulfonic acid, 2-butylsulfonic acid, fluorosulfonic acid, 2-iodobenzenesulfonic acid, benzylsulfonic acid, cresolsulfonic acid, methylbenzene methanesulfonic acid, hexylsulfonic acid, 2-(N-morpholine)ethanesulfonic acid. Preferably, the amount of the acid catalyst is 0.002-0.02wt% of the mass of the reaction solution.

[0017] In the present invention, the metal salt, the ligand and the acid catalyst are added simultaneously to the dehydrolinalool selective hydrogenation reaction liquid.

[0018] In the present invention, optionally, before the catalytic isomerization reaction, a step of separating and recovering the solvent from the dehydrolinalool selective hydrogenation reaction liquid is further included, preferably by vacuum distillation.

[0019] In the present invention, the temperature of the catalytic isomerization reaction is 90-120° C., and the reaction time is 2-6 hours.

[0020] In the present invention, the impurities generated by the catalytic isomerization of dehydrolinalool and the isomerization catalyst are finally distributed in the heavy components in the bottom of the deweighting tower, and are discharged from the distillation system along with the heavy components, thereby achieving separation from the product linalool.

[0021] The present invention adopts the above technical solution and has the following positive effects:

[0022] 1. The present invention has a novel concept. A catalyst is added to the hydrogenation reaction liquid to convert the residual dehydrolinalool into high-boiling impurities, thereby reducing the number of plates and energy consumption of linalool distillation separation, and effectively improving the purity of the linalool product.

[0023] 2. The present invention uses a metal catalyst and an acid catalyst for synergistic catalysis to efficiently complete the efficient conversion of the dehydrolinalool remaining in the reaction solution. DETAILED DESCRIPTION

[0024] The present invention is described in detail below by examples, but the present invention is not limited to the following examples.

[0025] The main raw material information is as follows:

[0026] Dehydrolinalool, purity 98%, Aladdin reagent; 5% palladium calcium carbonate, Inokite; 1% palladium calcium carbonate, Evonik catalyst; methanol, ethanol, reagent grade, J&K reagent, purity 99%; gold chloride, silver tetrafluoroborate, silver bis(fluorosulfonyl)imide, dimethyl(acetylacetonate)gold, Alfa Aesar, purity 99%; triphenylphosphine chlorogold, silver hexafluorophosphate, purity 99%, Aldrich reagent; bis(trifluoromethanesulfonyl)imide copper, triphenylphosphine, tricyclohexylphosphine, purity 99%, J&K reagent; 2-(bisadamantylphosphine)biphenyl, 1,4-diphenylphosphinobutane, 1-[2-bis(tert-butylphosphinophenyl)-3,5-diphenyl-1-H-pyrazole, purity 98%, Sinoco catalyst;

[0027] p-Toluenesulfonic acid, p-Chlorobenzenesulfonic acid, cresolsulfonic acid, purity 99%, Aladdin reagent; methanesulfonic acid, purity 99%, Sinopharm reagent; 2-(N-morpholino)ethanesulfonic acid, purity 99%, McLean reagent. Linalool standard, citral standard, purity 99%, Myrel Biochemical Technology.

[0028] The gas chromatography test conditions of the present invention are as follows:

[0029] Instrument model: Agilent 8890B; Chromatographic column: Capillary column HP-5 (30m×0.30mm×0.25μm); Initial temperature 60℃, raised to 110℃ at a rate of 5℃ / min; then raised to 170℃ at a rate of 10℃ / min, maintained for 5.0min. Carrier gas: high-purity nitrogen, split ratio 35:1, split flow 42mL / min. Carrier gas saving: 19mL / min, start waiting time 5.0min. Injection temperature 250℃, detector FID, detector temperature 250℃, air flow 350mL / min, hydrogen flow 30mL / min, tail gas flow 60mL / min, injection volume 0.1μL.

[0030] Embodiment 1:

[0031] Selective hydrogenation of dehydrolinalool to linalool

[0032] At room temperature, solvent methanol (441g), hydrogenation raw material dehydrolinalool (883g, 5.8mol), 5.0% Lindela catalyst (4.4g, 0.5wt% of substrate mass) were added to the autoclave in sequence. The autoclave was sealed, and after the pressure test was carried out for 30min without any problems, the air in the reactor was replaced 3 times with nitrogen, and then the nitrogen was replaced 3 times with hydrogen, and finally 5barG of hydrogen was injected. The autoclave was stirred and kept warm, and the coil cooling and stirring shaft cooling in the reactor were turned on to keep the temperature in the reactor at 30°C. The reaction was kept warm for 3 hours, and samples were taken and analyzed at regular intervals. The reaction progress was detected by GC. When the conversion rate of dehydrolinalool reached or exceeded 99.5%, the stirring of the reactor and the hydrogen feeding were turned off in time, and the exhaust method was turned on to slowly exhaust the hydrogen. The hydrogen was replaced with nitrogen three times, and then the reaction solution was pressed out of the reactor through a filter with nitrogen. GC detection was performed again. The main components of the reaction solution were as follows (excluding the solvent peak and normalizing the area): methyl heptenone 0.27%, dehydrolinalool 0.32%, linalool 95.54%, dihydrolinalool 1.46%, and heavy components 2.41%.

[0033] Embodiment 2:

[0034] Selective hydrogenation of dehydrolinalool to linalool

[0035] At room temperature, ethanol solvent (1157g), hydrogenation raw material dehydrolinalool (1157g, 7.6mol), 1.0% Lindela catalyst (9.3g, 0.8wt% of substrate mass) were added to 5L of autoclave in sequence, the autoclave was sealed, and after the pressure test was carried out for 30min without any problem, the air in the reactor was replaced 3 times with nitrogen, and then the nitrogen was replaced 3 times with hydrogen, and finally 10barG of hydrogen was injected. The autoclave was turned on for stirring and heat preservation, and the coil cooling and stirring shaft cooling in the reactor were turned on to keep the temperature in the reactor at 50°C. The reaction was kept warm for 4 hours, and sampling and analysis were performed at regular intervals. The reaction progress was detected by GC. When the conversion rate of dehydrolinalool reached or exceeded 99.5%, the stirring of the reactor and the hydrogen feeding were turned off in time, and the exhaust method was turned on to slowly exhaust the hydrogen. The hydrogen was replaced with nitrogen three times, and then the reaction solution was pressed out of the reactor through a filter with nitrogen. GC detection was performed again. The main components of the reaction solution were as follows (excluding the solvent peak and normalizing the area): methyl heptenone 0.26%, dehydrolinalool 0.43%, linalool 95.63%, dihydrolinalool 1.36%, and heavy components 2.32%.

[0036] Embodiment 3:

[0037] Refining of the selective hydrogenation reaction solution of dehydrolinalool, the reaction solution is from Example 1

[0038] First, the solvent is separated and recovered by vacuum distillation, the distillation temperature is 71-73°C, the pressure is 60kPa, and there is no extraction from the bottle mouth condenser after distillation for 1h, and the methanol content in the reaction solution after vacuum distillation is less than 0.1%. At room temperature, the selective hydrogenation reaction solution of dehydrolinalool (206.0g), gold chloride (2.1mg), silver tetrafluoroborate (2.1mg), triphenylphosphine (4.1mg) after desolvation are added to a 2L three-necked flask equipped with a magnetic stirrer in sequence, and finally p-toluenesulfonic acid (4.1mg) is added. After all the materials are added, a 1m long distillation column and a reflux ratio controller are connected above the 2L three-necked flask, and a 3*3 tripod screw filler is filled in the column, and the total number of plates is ~30. The three-necked flask is placed in an oil bath, and the oil bath stirring and heating are turned on. The stirring is controlled at 600rpm, and the oil bath temperature is controlled at 120°C, so that the temperature in the three-necked flask is maintained at 100°C. Turn on the condensing water and vacuum system at the top of the tower, control the condensing temperature at 5°C, and the pressure at the top of the tower at 1kPa. After the temperature and pressure of the top and the bottom of the tower are stable, and the top of the tower begins to reflux stably, turn on the reflux ratio controller, the top reflux ratio is 5-7:1, and the light components and products are cooled and liquefied by the top condenser before extraction. The temperature before the condensation of the light components at the top of the tower is about 90°C, and the material stays in the bottom of the tower for 3 hours. Take samples of the top of the tower at regular intervals, and analyze the sample composition by GC. The results are as follows. By adopting the above conditions, the composition of linalool obtained by top distillation is as follows: methyl heptenone (0.290%), dehydrolinalool + 3,7-dimethyl 3,6-octadien-2-one (0.007%), linalool (98.324%), dihydrolinalool (1.327%), and heavy components (0.053%); the sum of linalool and dihydrolinalool is 99.651%, reaching the level of superior products, and the distillation yield is 91.3%. The bottom composition is as follows: methyl heptenone (0.062%), citral and 3,7-dimethyl 3,6-octadien-2-one (3.621%), linalool (66.183%), dihydrolinalool (2.866%), and heavy components (27.268%).

[0039] Embodiment 4:

[0040] Refining of the selective hydrogenation reaction solution of dehydrolinalool, the reaction solution is from Example 1

[0041] First, the solvent was separated and recovered by vacuum distillation, the distillation temperature was 71-73°C, the pressure was 60kPa, and after distillation for 1h, there was no extraction from the bottle mouth condenser, and the methanol content in the reaction solution after vacuum distillation was less than 0.05%. At room temperature, the dehydrogenated linalool selective hydrogenation reaction solution (238.0g), dimethyl (acetylacetone) gold (23.8mg), 2-(diadamantylphosphine) biphenyl (47.6mg) after desolvation were added to a 2L three-necked flask equipped with a magnetic stirrer in sequence, and finally p-chlorobenzenesulfonic acid (47.6mg) was added. After all the materials were added, a 1m long distillation column and a reflux ratio controller were connected above the 2L three-necked flask, and a 3*3 tripod screw filler was filled in the column, and the total number of plates was ~30. The three-necked flask was placed in an oil bath, and the oil bath stirring and heating were turned on. The stirring was controlled at 600rpm, and the oil bath temperature was controlled at ~103°C, so that the temperature in the three-necked flask was maintained at 95°C. Turn on the condensing water and vacuum system at the top of the tower, control the condensing temperature at 5°C, and the top pressure at 0.7kPa. After the top and bottom temperatures and pressures are stable, and the top of the tower begins to reflux stably, turn on the reflux ratio controller, the top reflux ratio is 5-7:1, the light components and products are cooled and liquefied by the top condenser and then extracted. The temperature before the condensation of the light components at the top of the tower is about 83°C, and the material stays in the bottom of the tower for 1 hour. Take samples of the top of the tower at regular intervals, and analyze the sample composition by GC. The results are as follows. By adopting the above conditions, the composition of linalool obtained by distillation at the top of the tower is as follows: methyl heptenone (0.281%), dehydrolinalool + 3,7-dimethyl 3,6-octadien-2-one (0.003%), linalool (98.436%), dihydrolinalool (1.254%), and heavy components (0.026%); the sum of linalool and dihydrolinalool is 99.690%, reaching the level of superior products, and the distillation yield is 93.2%. The composition of the bottom of the tower is as follows: methyl heptenone (0.119%), citral and 3,7-dimethyl 3,6-octadien-2-one (4.642%), linalool (56.000%), dihydrolinalool (4.279%), and heavy components (34.960%).

[0042] Embodiment 5:

[0043] Refining of the selective hydrogenation reaction solution of dehydrolinalool, the reaction solution is from Example 1

[0044] First, the solvent was separated and recovered by vacuum distillation, the distillation temperature was 71-73°C, the pressure was 60kPa, and there was no extraction from the bottle mouth condenser after distillation for 1h. The methanol content in the reaction solution after vacuum distillation was less than 0.05%. At room temperature, the dehydrogenated linalool selective hydrogenation reaction solution (387.0g), silver bis(fluorosulfonyl)imide (19.4mg), 1,4-diphenylphosphinobutane (38.7mg) after desolvation were added to a 2L three-necked flask equipped with a magnetic stirrer in sequence, and finally p-methanesulfonic acid (77.4mg) was added. After all the materials were added, a 1m long distillation column and a reflux ratio controller were connected above the 2L three-necked flask, and a 3*3 tripod screw packing was filled in the column, and the total number of plates was ~30. The three-necked flask was placed in an oil bath, and the oil bath stirring and heating were turned on. The stirring was controlled at 600rpm, and the oil bath temperature was controlled at ~125°C, so that the temperature in the three-necked flask was maintained at 110°C. Turn on the condensing water and vacuum system at the top of the tower, control the condensing temperature at 5°C, and the top pressure at 1kPa. After the top and bottom temperatures and pressures are stable, and the top of the tower begins to reflux stably, turn on the reflux ratio controller, the top reflux ratio is 5-7:1, the light components and products are cooled and liquefied by the top condenser and then extracted. The temperature before the condensation of the light components at the top of the tower is about 90°C, and the material stays in the bottom of the tower for 6 hours. Take samples of the top of the tower at regular intervals, and analyze the sample composition by GC. The results are as follows. By adopting the above conditions, the composition of linalool obtained by top distillation is as follows: methyl heptenone (0.286%), dehydrolinalool + 3,7-dimethyl 3,6-octadien-2-one (0.017%), linalool (98.238%), dihydrolinalool (1.407%), and heavy components (0.052%); the sum of linalool and dihydrolinalool is 99.645%, reaching the level of superior products, and the distillation yield is 93.4%. The bottom composition is as follows: methyl heptenone (0.041%), citral and 3,7-dimethyl 3,6-octadien-2-one (4.581%), linalool (57.588%), dihydrolinalool (2.200%), and heavy components (35.590%).

[0045] Embodiment 6:

[0046] Refining of the selective hydrogenation reaction solution of dehydrolinalool, the reaction solution is from Example 2

[0047] First, the solvent was separated and recovered by vacuum distillation, the distillation temperature was 71-73°C, the pressure was 60kPa, and there was no extraction from the bottle mouth condenser after distillation for 1h. The ethanol content in the reaction solution after vacuum distillation was less than 0.05%. At room temperature, the dehydrogenated linalool selective hydrogenation reaction solution (483.0g), bis(trifluoromethanesulfonyl imide) copper (48.3mg), tricyclohexylphosphine (58.0mg) after desolvation were added to a 2L three-necked flask equipped with a magnetic stirrer in sequence, and finally 2-(N-morpholine) ethanesulfonic acid (72.5mg) was added. After all the materials were added, a 1m long distillation column and a reflux ratio controller were connected above the 2L three-necked flask, and a 3*3 tripod screw filler was filled in the column, and the total number of plates was ~30. The three-necked flask was placed in an oil bath, and the oil bath was turned on for stirring and heating. The stirring was controlled at 600rpm, and the oil bath temperature was controlled at 120°C, so that the temperature in the three-necked flask was maintained at 100°C. The condensation water and vacuum system at the top of the tower are turned on, and the condensation temperature is controlled at 5°C and the pressure at the top of the tower is controlled at 1kPa. After the temperature and pressure of the top and the bottom of the tower are stable, and the top of the tower begins to reflux stably, the reflux ratio controller is turned on, and the top reflux ratio is 2 to 5:1. The light components and products are extracted after cooling and liquefaction through the top condenser. The temperature before the condensation of the light components at the top of the tower is about 90°C, and the material stays in the bottom of the tower for 3h. The top of the tower is sampled regularly, and the sample composition is analyzed by GC. The results are shown below. By adopting the above conditions, the composition of linalool obtained by top distillation is as follows: methyl heptenone (0.278%), dehydrolinalool (0.009%), linalool (98.509%), dihydrolinalool (1.170%), and heavy components (0.044%); among which linalool and dihydrolinalool add 99.679%, reaching the level of superior products, and the distillation yield is 94.2%. The bottom composition of the tower is as follows: methyl heptenone (0.134%), dehydrolinalool + citral and 3,7-dimethyl 3,6-octadien-2-one (7.222%), linalool (49.169%), dihydrolinalool (4.429%), and heavy components (39.046%).

[0048] Embodiment 7:

[0049] Refining of the selective hydrogenation reaction solution of dehydrolinalool, the reaction solution is from Example 2

[0050] First, the solvent was separated and recovered by vacuum distillation, the distillation temperature was 71-73°C, the pressure was 60kPa, and there was no extraction from the bottle mouth condenser after distillation for 1 hour. The ethanol content in the reaction solution after vacuum distillation was less than 0.05%. At room temperature, the dehydrogenated linalool selective hydrogenation reaction solution (519.0g), triphenylphosphine chlorogold (5.2mg), silver hexafluorophosphate (7.8mg), 1-[2-di-tert-butylphosphinophenyl]-3,5-diphenyl-1-H pyrazole (15.6mg) were added to a 2L three-necked flask equipped with a magnetic stirrer in sequence, and finally cresol sulfonic acid (51.9mg) was added. After all the materials were added, a 1m long distillation column and a reflux ratio controller were connected above the 2L three-necked flask, and a 3*3 tripod screw filler was filled in the column, and the total number of plates was ~30. Place the three-necked flask in an oil bath, start the oil bath stirring and heating, control the stirring at 600rpm, and control the oil bath temperature at about 120℃, so that the temperature in the three-necked flask is maintained at 100℃. Turn on the top condensing water and vacuum system, control the condensation temperature at 5℃, and the top pressure at 1kPa. After the top and bottom temperature and pressure of the tower are stable, and the top of the tower begins to reflux stably, turn on the reflux ratio controller, the top reflux ratio is 1 to 5:1, and the light components and products are cooled and liquefied by the top condenser before extraction. The temperature before the condensation of the light components at the top of the tower is about 90℃, and the material stays in the bottom of the tower for 2h. Take samples of the top produced liquid regularly, and analyze the sample composition by GC. The results are as follows. By adopting the above conditions, the composition of linalool obtained by top distillation is as follows: methyl heptenone (0.274%), dehydrolinalool + 3,7-dimethyl 3,6-octadien-2-one (0.008%), linalool (98.522%), dihydrolinalool (1.145%), and heavy components (0.049%); the sum of linalool and dihydrolinalool is 99.667%, reaching the level of superior products, and the distillation yield is 93.9%. The bottom composition is as follows: methyl heptenone (0.042%), citral and 3,7-dimethyl 3,6-octadien-2-one (6.864%), linalool (51.406%), dihydrolinalool (4.652%), and heavy components (37.035%).

[0051] Comparative Example

[0052] The selective hydrogenation reaction liquid of dehydrolinalool was purified without adding an isomerization catalyst. The reaction liquid was from Example 2.

[0053] First, the solvent was separated and recovered by vacuum distillation, with a distillation temperature of 71-73°C and a pressure of 60kPa. After distillation for 1h, there was no extraction from the bottle mouth condenser, and the ethanol content in the reaction solution after vacuum distillation was less than 0.05%. At room temperature, the dehydrogenated linalool selective hydrogenation reaction solution (519.0g) after desolvation was added to a 2L three-necked flask equipped with a magnetic stirrer in sequence. After the addition was completed, a 1m long distillation column and a reflux ratio controller were connected above the 2L three-necked flask. The column was filled with 3*3 tripod screw packing, and the total number of plates was ~30. The three-necked flask was placed in an oil bath, and the oil bath was turned on for stirring and heating. The stirring was controlled at 600rpm, and the oil bath temperature was controlled at about 120°C, so that the temperature in the three-necked flask was maintained at 100°C. The top condensation water and vacuum system were turned on, and the condensation temperature was controlled at 5°C and the top pressure was controlled at 1kPa. After the temperature and pressure of the tower top and the tower bottom are stable and the tower top begins to reflux stably, the reflux ratio controller is turned on, the tower top reflux ratio is 1 to 5:1, and the light components and products are extracted after cooling and liquefaction through the tower top condenser. The temperature before the condensation of the light components at the top of the tower is about 90°C, and the material stays in the tower bottom for 2 hours. The tower top produced liquid is sampled regularly, and the sample composition is analyzed by GC. The results are shown below. By adopting the above conditions, the composition of linalool obtained by top distillation is as follows: methyl heptenone (0.293%), dehydrolinalool (0.455%), linalool (97.976%), dihydrolinalool (1.223%), and heavy components (0.053%); among which linalool and dihydrolinalool add 99.199%, and the distillation yield is 87.8%; compared with the addition of isomerization catalyst, both data are reduced to a certain extent. The bottom composition is as follows: methyl heptenone (0.021%), dehydrolinalool (0.248%), linalool (78.676%), dihydrolinalool (2.350%), and heavy components (18.705%); since dehydrolinalool, linalool, and dihydrolinalool have similar boiling points, more linalool remains in the bottom.

Claims

1. A method for improving the purity of a linalool product, specifically comprising: adding a catalyst to a reaction solution in which dehydrolinalool is selectively hydrogenated to prepare linalool, catalyzing an isomerization reaction of the incompletely converted dehydrolinalool raw material to generate 3,7-dimethyl-3,6-octadien-2-one and citral, which have a boiling point that is significantly different from that of linalool, and separating them.

2. The method according to claim 1, characterized in that In the dehydrolinalool selective hydrogenation reaction liquid, the content of the raw material dehydrolinalool is 0.05-0.5wt%.

3. The method according to claim 1 or 2, characterized in that The catalyst is composed of a metal catalyst and an acid catalyst; the metal catalyst is obtained by in-situ complexation of a metal salt and a ligand, the metal salt is selected from one or more of a gold salt, a copper salt, and a silver salt, preferably, the metal salt is gold chloride, gold bromide, chlorocarbonyl gold, tetrachloroauric acid, dimethyl (acetylacetonate) gold, dimethyl (trifluoroacetylacetonate) gold, triphenylphosphine chlorogold, silver tetrafluoroborate, silver trifluoromethanesulfonate, silver bis(trifluoromethanesulfonylimide), silver bis(trifluoromethanesulfonylimide), silver hexafluorophosphate, cuprous tetrafluoroborate, copper tetrafluoroborate, trifluoromethanesulfonate, copper bis(trifluoromethanesulfonylimide), cupric chloride, cuprous chloride, etc., and the amount of the metal salt is 0.001-0.01wt% of the mass of the reaction solution.

4. The method according to any one of claims 1 to 3, characterized in that: The ligand is selected from phosphine ligands, nitrogen-phosphorus ligands, pyridine ligands, sulfur ligands, etc. Preferably, the ligand is triphenylphosphine, tri(3-methylphenyl)phosphine, tri(4-methylphenyl)phosphine, 1,2-diphenylphosphinoethane, 1,3-diphenylphosphinopropane, 1,4-diphenylphosphinobutane, 1,8-bis(diphenylphosphino)naphthalene, tributylphosphine, tricyclohexylphosphine, tricyclopentylphosphine, 2-(bisadamantylphosphine)biphenyl, 1-[2-bis-tert-butylphosphinophenyl]-3,5-diphenyl-1-H pyrazole, etc. The amount of the ligand used is 0.002-0.02wt% of the mass of the reaction solution.

5. The method according to any one of claims 1 to 4, characterized in that: The acid catalyst is selected from one or more of benzenesulfonic acid, p-toluenesulfonic acid, p-chlorobenzenesulfonic acid, p-bromobenzenesulfonic acid, naphthalenesulfonic acid, methanesulfonic acid, ethanesulfonic acid, 2-butylsulfonic acid, fluorosulfonic acid, 2-iodobenzenesulfonic acid, benzylsulfonic acid, cresolsulfonic acid, methylbenzene methanesulfonic acid, hexylsulfonic acid, and 2-(N-morpholine)ethanesulfonic acid. Preferably, the amount of the acid catalyst is 0.002-0.02wt% of the mass of the reaction solution.

6. The method according to any one of claims 1 to 5, characterized in that: Optionally, before the catalytic isomerization reaction, the method further comprises a step of separating and recovering the solvent from the dehydrolinalool selective hydrogenation reaction liquid, preferably by vacuum distillation.

7. The method according to any one of claims 1 to 6, characterized in that: The temperature of the catalytic isomerization reaction is 90-120° C., and the reaction time is 2-6 hours.

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