Full-continuous chemical synthesis method of citral

Abstract

The invention belongs to the technical field of fine chemical engineering, and particularly relates to a citral full-continuous chemical synthesis method. A plurality of feeding pumps, a mixer, a microreactor, a back pressure valve, a liquid-liquid separator and an online filter are connected according to a citral linear synthesis route to form a fully continuous chemical synthesis device, so that fully continuous chemical synthesis of citral is realized; products with consistent quality can be stably produced, the integration degree is high, the occupied area for production is small, the unit productivity is high, meanwhile, the yield can be adjusted according to requirements, and the amplification effect existing in a kettle type process is avoided.

Description

Technical Field

[0001] This invention belongs to the field of fine chemical technology, specifically relating to a fully continuous chemical synthesis method for citral. Background Technology

[0002] Citral (3,7-dimethyl-2,6-octadienal) is a terpene aliphatic aldehyde, holding a very important position among open-chain monoterpenes. Its relative molecular weight is 152.23, and its molecular formula is C2. 10 H 16 Citral, with a boiling point of 102-104℃ / 1.6kPa, is a colorless or pale yellow transparent liquid. It is generally composed of two isomers, geranialdehyde (trans-citral, boiling point 110-112℃ / 1.6kPa) and neraldehyde (cis-citral, boiling point 102-104℃ / 1.6kPa). The mixture of these two isomers has a boiling point of 228-229℃ at normal pressure. Its structural formula is as follows:

[0003]

[0004] Currently, the mainstream industrial synthesis route for citral is as follows: First, isobutylene is condensed with formaldehyde to generate the intermediate 3-methyl-3-buten-1-ol, which is then used to prepare the raw materials for the synthesis of citral, namely isopentenol and 3-methyl-3-butenal; finally, citral is obtained through aldol condensation and Claisen-Cope rearrangement. This production process typically employs a batch reaction mode, requiring the sequential synthesis of multiple intermediates, with the intermediate products being distilled and purified after each reaction stage. Due to the involvement of multiple distillation and purification operations, its energy consumption cost is relatively high, accounting for approximately 30% of the total production cost. This high energy consumption is mainly due to the need for repeated material separation and purification processes during the reaction.

[0005] Currently, the production process of citral still requires further optimization and innovation. Through in-depth research into the reaction mechanism, improvement of the process flow, reduction of energy consumption, enhancement of raw material conversion efficiency, and the realization of intelligent control, it is expected to significantly increase the overall yield from isopentenol to citral, thereby creating greater economic benefits. This technological breakthrough will bring a qualitative leap to the industrial production of citral. Summary of the Invention

[0006] The purpose of this invention is to provide a fully continuous chemical synthesis device for citral with high production efficiency, good and stable product quality, and low emissions of waste gas, wastewater, and solid waste, as well as its application.

[0007] The fully continuous chemical synthesis method for citral provided by this invention involves sequentially connecting multiple feed pumps, mixers, microreactors, back pressure valves, liquid-liquid separators, and online filters according to a linear synthesis route for citral, forming a fully continuous chemical synthesis apparatus. The specific steps are as follows:

[0008] (1) Prepared materials 1 and 2 are pumped to mixing tank 1 via pumps 1 and 2 respectively for thorough mixing; after mixing, the mixture is directly fed into reactor 1 via connecting pipes for chlorination reaction at -15-0℃ for 15-25 minutes; the reaction liquid flowing out of reactor 1 enters tank 1, which is a stirred tank with a filter core in the middle, i.e., a filter tank, used to filter out insoluble solids, and the filtrate is used as material 3; wherein:

[0009] Component 1 is a dichloromethane suspension of alumina with a concentration of 0.26-0.36 kg / L; Component 2 is a mixture of isoprene with a concentration of 0.5-0.6 kg / L and thionyl chloride with a concentration of 0.44-0.54 kg / L; the flow ratio of Component 1 to Component 2 is 5.6-6:1; the time in reaction 1 is 15-25 min; Component 3 is an isoprene dichloromethane solution with a concentration of 0.10-0.13 kg / L.

[0010] (2) Material 3 is fully mixed in mixing 2 by pump 3 and material 4 conveyed by pump 4, and then directly enters reaction 2 for esterification reaction at 100-120℃ for 50-80 minutes.

[0011] Material 4 is a dichloromethane suspension containing sodium acetate at a concentration of 0.57-0.67 kg / L and tetrabutylammonium bromide at a concentration of 0.2-0.3 kg / L; the flow ratio of material 3 to material 4 is 6.6-7.6:1, and the retention time in reaction 2 is 50-80 min;

[0012] (3) The reaction liquid flowing out from reactor 2 enters mixer 3 and is mixed evenly with material 5 conveyed by pump 5 in mixer 3. Then it enters reactor 3 and undergoes hydrolysis reaction at 100-120℃ for 10-15 minutes; wherein:

[0013] Material 5 is a 10%-30% sodium hydroxide aqueous solution; the flow ratio of the reaction solution to material 5 is 3.8-4:1, and the retention time in reaction 3 is 10-15 min;

[0014] (4) The outflowing reaction liquid from reaction 3 flows through back pressure valve 1. The function of back pressure valve 1 is to regulate the reaction pressure in reaction 2 and reaction 3. The outflowing liquid from back pressure valve 1 directly enters fraction 1. In fraction 1, the organic phase and the aqueous phase are separated. Fraction 1 is equipped with an upper outlet and a lower outlet. The upper outlet is connected to tank 2, which is used to store the separated upper waste liquid. The lower outlet is connected to pump 6, which transports the lower liquid to the distiller. The function of the distiller is to remove the solvent dichloromethane from the reaction liquid. The recovered solvent dichloromethane is condensed and stored in tank 3. The liquid after removing the solvent is material 6, which is an isopentenol solution with a concentration of 0.88-0.95 kg / L.

[0015] (5) Material 6 is pumped to mixer 4 by pump 7. Mixer 4 is a four-way micro mixer with three inlets and one outlet. The other two inlets of mixer 4 are: the oxygen inlet of material 7 by gas flow controller and the water inlet of material 8 by pump 8. The flow ratio of the three channels is controlled to be 5.7-7:120-150:1. The mixture is evenly mixed in mixer 4 and then enters reverse 4 for oxidation reaction at 70-90℃ for 3-7 minutes.

[0016] (6) The reaction liquid flowing out of reaction 4 flows through back pressure valve 2, which is used to regulate the reaction pressure in reaction 4; the liquid flowing out of back pressure valve 2 enters separator 2, where the organic phase and aqueous phase are separated into layers. Separator 2 is provided with an upper outlet and a lower outlet; the upper outlet is connected to pump 9, and the lower outlet is connected to pump 8; material 9 is transported to mixer 5 by pump 9. Mixer 5 is a four-way micro mixer with three inlets and one outlet. The other two inlets of mixer 5 are: the inlet of material 11 supplied by pump 11 and the inlet of material 10 supplied by pump 10; the flow ratio of the three is controlled to be 66-76:298-308:1. After being mixed evenly in mixer 5, the mixture enters reaction 5 and undergoes aldol condensation reaction at 100-130℃ for 120-150 minutes;

[0017] Material 9 is a mixed solution of isopentenol with a concentration of 50%-55% and isopentenal with a concentration of 45%-50%;

[0018] Material 10 is an aqueous solution of toluenesulfonic acid with a concentration of 4.3-5 kg / L, which is the inlet for conveying materials;

[0019] Material 11 is a cyclohexane solution of isopentenol with a concentration of 0.21-0.29 kg / L;

[0020] The flow ratio of the three materials is controlled at 66-76:298-308:1, and the residence time in the mixture is 120-150 min.

[0021] (7) The reaction liquid flowing out from reactor 5 is material 12, which is a solution of acetal in cyclohexane with a concentration of 0.22-0.26 kg / L; material 12 is pumped into reactor 6 through pump 12 and subjected to a series Claisen-Cope rearrangement reaction at 200-280℃ for 5-10 minutes; the reaction liquid flowing out from reactor 6 flows through back pressure valve 3, the function of which is to regulate the reaction pressure in reactor 6; the outflow liquid from back pressure valve 3 is pumped into tank 4 through pump 13, the function of which is to recover the cyclohexane solution of isopentenol; the reaction liquid after recovery is pumped to tank 5 through pump 14, the function of which is to distill and purify the product citral;

[0022] The present invention prepares citral with a purity of over 96% and a citral yield of over 70%.

[0023] Among them, Mix 1 to Mix 5 are abbreviations for the first to fifth micro mixers, Reverse 1 to Reverse 6 are abbreviations for the first to sixth microreactors, Back pressure valve 1 to Back pressure valve 3 are abbreviations for the first to third back pressure valves, and Separator 1 and Separator 2 are abbreviations for the first liquid-liquid separator and the second liquid-liquid separator.

[0024] Preferably, pumps 1 and 4 are peristaltic pumps capable of conveying slurry, and pumps 2, 3, 5, 6, 7, 8, 9, 10, 11, 12, 13, and 14 are plunger pumps capable of conveying solutions.

[0025] Preferably, Mixer 1 to Mixer 5 are three micromixers connected in series in a U-shape, with fluid channel dimensions of 100μm-20mm (circular or square), length of 1-100cm, applicable flow rate of 1-3000mL / min, and material of one or more of glass, polytetrafluoroethylene, stainless steel, Hastelloy, tantalum, and zirconium.

[0026] Preferably, reverse 1, reverse 2, reverse 3, and reverse 6 are tubular microreactors with built-in X-shaped mixing components, such as... Figure 2 As shown, this is a double-layer structure consisting of an outer tube and an inner tube. The space between the outer and inner tubes forms a heat exchange flow channel, while the inner tube serves as a reactant channel. Multiple X-shaped components 3 are arranged sequentially within the inner tube. Each end of the tube has a reactant outlet 1 and a reactant inlet 5, respectively, and the sides of both ends of the tube have heat exchange fluid outlets 2 and heat exchange fluid inlets 4. The fluid channel dimensions range from 100μm to 20mm, and the material is one or a combination of several of the following: glass, polytetrafluoroethylene (PTFE), stainless steel, Hastelloy, tantalum, and zirconium.

[0027] Preferably, the reverse 4 is a fixed-bed microreactor (filled with Pt / C catalyst), such as Figure 3 As shown, similar to structure 1, it also has a double-layer structure consisting of an outer tube and an inner tube. The space between the outer and inner tubes is a heat exchange flow channel, and the inner tube is a reactant channel filled with catalyst 8. The tube body has a reactant outlet 6 and a reactant inlet 10 at each end, and a heat exchange fluid outlet 7 and a heat exchange fluid inlet 9 on the sides of both ends. The fluid channel size is 100μm-20mm, and the material is one or a combination of stainless steel, Hastelloy, tantalum, and zirconium.

[0028] Preferably, the reverse 5 is a CSTR reactor, such as... Figure 4 As shown, it consists of three reaction units connected in series. Each reaction unit is composed of a jacketed glass bottle (reaction vessel 13) with a volume of 25-50 mL, a condenser 11, and a storage tank 12, which are connected in sequence by pipelines. Control valves are installed on the pipelines. The material can be glass.

[0029] Preferably, separators 1 and 2 are liquid-liquid separators designed based on the principle of gravity settling, such as... Figure 5As shown, the liquid-liquid separator has a cylindrical structure with hot fluid pipelines on both sides. A material inlet 14 and an upper light phase outlet 18 are located at the top of the cylinder, and a lower heavy phase outlet 17 is located at the bottom. A heat exchange fluid outlet 16 is located above the side hot fluid pipelines, and a heat exchange fluid inlet 15 is located below them. The separator has an inner diameter of 1-20 cm and a height of 1-200 cm. It is made of one or a combination of glass, polytetrafluoroethylene (PTFE), stainless steel, Hastelloy, tantalum, and zirconium.

[0030] Preferably, tank 1 is a filter tank with a sand core filter layer, such as... Figure 6 As shown, it has a stirring function to prevent solid materials from settling on the filter layer and clogging it, thus reducing filtration efficiency. The filter tank is cylindrical with a double-layer structure, consisting of an outer tank and an inner tank, with a heat exchange flow channel between them. Inside the inner tank, a sand core filter layer 24 is laid at the bottom, and a stirring paddle 23 is installed in the middle of the tank. A material inlet 19 is located at the top of the tank, and a filtrate outlet 20 is located at the bottom. A heat exchange fluid inlet 21 is located on the outside of the tank, below the heat exchange flow channel, and a heat exchange fluid outlet 22 is located at the top.

[0031] Preferably, tanks 2, 3, and 4 are liquid storage tanks, and tank 5 is a distillation tank used for the distillation and purification of citral.

[0032] Preferably, the back pressure valve 1, back pressure valve 2, and back pressure valve 3 are made of stainless steel or Hastelloy, the connecting pipes are 1.6mm-10mm in size, and the pressure conditions range from 0.1 to 10.0MPa.

[0033] In this invention, material 1 is a slurry obtained by dispersing alumina in dichloromethane; material 2 is a mixture of isoprene and sulfonium chloride; material 3 is a solution of isoprene chloride, the product generated by the reaction of material 1 and material 2, in dichloromethane; material 4 is a slurry obtained by dispersing sodium acetate and tetrabutylammonium bromide in dichloromethane; material 5 is a 10-30% aqueous solution of sodium hydroxide; material 6 is a solution of isoprene acetate, the product generated by the reaction of material 3 and material 4, and isoprene alcohol, the product generated by the reaction of material 5, in dichloromethane, followed by solvent removal of isoprene alcohol; material 7 is oxygen; material 8 is water; material 9 is a mixture of isoprene alcohol and isoprene aldehyde, the products generated by the reaction of material 6, material 7 and material 8; material 10 is an aqueous solution of p-toluenesulfonic acid; material 11 is a cyclohexane solution of isoprene alcohol; and material 12 is a solution of acetal, the product generated by the reaction of material 9, material 10 and material 11, in cyclohexane.

[0034] Compared with batch reactors, this invention has higher production efficiency, better and more stable product quality, and less waste emissions. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the process for a fully continuous chemical synthesis apparatus for citral.

[0036] Figure 2 Illustration of a tubular microreactor with an internal X-shaped mixing component.

[0037] Figure 3 This is a diagram of a fixed-bed microreactor.

[0038] Figure 4 The diagram shows a CSTR reactor.

[0039] Figure 5 This is a structural diagram of a liquid-liquid separator.

[0040] Figure 6 This is a structural diagram of a filter tank with a sand core filter layer.

[0041] The labels in the diagram are as follows: 1-Reactant outlet, 2-Heat exchange fluid outlet, 3-X-shaped component, 4-Heat exchange fluid inlet, 5-Reactant inlet, 6-Reactant outlet, 7-Heat exchange fluid outlet, 8-Catalyst, 9-Heat exchange fluid inlet; 10-Reactant inlet, 11-Condenser, 12-Storage tank, 13-Reaction tank, 14-Material inlet, 15-Heat exchange fluid inlet, 16-Heat exchange fluid outlet, 17-Lower heavy phase outlet, 18-Upper light phase outlet; 19-Material inlet, 20-Filtrate outlet, 21-Heat exchange fluid inlet, 22-Heat exchange fluid outlet, 23-Agitator, 24-Sand core filter layer. Detailed Implementation

[0042] The present invention will be further described below with reference to specific embodiments and accompanying drawings.

[0043] Example 1

[0044] (1) Prepared materials 1 and 2 are pumped to mixing tank 1 via pumps 1 and 2 respectively for thorough mixing; after mixing, the mixture is directly fed into reactor 1 via connecting pipes for chlorination reaction at -15-0℃ for 15-25 minutes; the reaction liquid flowing out of reactor 1 enters tank 1, which is a stirred tank with a filter core in the middle, i.e., a filter tank, used to filter out insoluble solids, and the filtrate is used as material 3; wherein:

[0045] Material 1 is a dichloromethane suspension of alumina with a concentration of 0.26 kg / L; Material 2 is a mixture of isoprene with a concentration of 0.5 kg / L and thionyl chloride with a concentration of 0.44 kg / L; the flow ratio of Material 1 to Material 2 is 5.6:1; the time in reaction 1 is 15 min; Material 3 is an isoprene dichloromethane solution with a concentration of 0.10 kg / L.

[0046] (2) Material 3 is fully mixed in mixing 2 by pump 3 and material 4 conveyed by pump 4, and then directly enters reaction 2 for esterification reaction at 100°C for 50 minutes.

[0047] Material 4 is a dichloromethane suspension containing sodium acetate at a concentration of 0.57 kg / L and tetrabutylammonium bromide at a concentration of 0.2 kg / L; the flow ratio of material 3 to material 4 is 6.6:1, and the retention time in reaction 2 is 50 min;

[0048] (3) The reaction liquid flowing out from reactor 2 enters mixer 3 and is mixed evenly with material 5 conveyed by pump 5 in mixer 3. Then it enters reactor 3 and undergoes hydrolysis reaction at 100°C for 10 minutes; wherein:

[0049] Material 5 is a 10% sodium hydroxide aqueous solution; the flow ratio of the reaction solution to material 5 is 3.8:1, and the retention time in reaction 3 is 10 min;

[0050] (4) The outflowing reaction liquid from reaction 3 flows through back pressure valve 1. The function of back pressure valve 1 is to regulate the reaction pressure in reaction 2 and reaction 3. The outflowing liquid from back pressure valve 1 directly enters fraction 1. In fraction 1, the organic phase and the aqueous phase are separated. Fraction 1 is equipped with an upper outlet and a lower outlet. The upper outlet is connected to tank 2, which is used to store the separated upper waste liquid. The lower outlet is connected to pump 6, which transports the lower liquid to the distiller. The function of the distiller is to remove the solvent dichloromethane from the reaction liquid. The recovered solvent dichloromethane is condensed and stored in tank 3. The liquid after removing the solvent is material 6, which is a 0.88 kg / L isopentenol solution.

[0051] (5) Material 6 is pumped to mixer 4 by pump 7. Mixer 4 is a four-way micro mixer with three inlets and one outlet. The other two inlets of mixer 4 are: the oxygen inlet of material 7 by gas flow controller and the water inlet of material 8 by pump 8. The flow ratio of the three channels is controlled to be 5.7:120:1. The mixture is evenly mixed in mixer 4 and then enters reverse 4 for oxidation reaction at 70°C for 3 minutes.

[0052] (6) The reaction liquid flowing out of reaction 4 flows through back pressure valve 2, which is used to regulate the reaction pressure in reaction 4; the liquid flowing out of back pressure valve 2 enters separator 2, where the organic phase and aqueous phase are separated into layers. Separator 2 is provided with an upper outlet and a lower outlet; the upper outlet is connected to pump 9, and the lower outlet is connected to pump 8; material 9 is transported to mixer 5 by pump 9. Mixer 5 is a four-way micro mixer with three inlets and one outlet. The other two inlets of mixer 5 are: the inlet of material 11 supplied by pump 11 and the inlet of material 10 supplied by pump 10; the flow ratio of the three is controlled to be 66:298:1. After being mixed evenly in mixer 5, the mixture enters reaction 5 and undergoes aldol condensation reaction at 100°C for 120 minutes;

[0053] Material 9 is a mixed solution of 50% isopentenol and 50% isopentenal;

[0054] Material 10 is an aqueous solution of toluenesulfonic acid with a concentration of 4.3 kg / L, which is the inlet for conveying materials;

[0055] Material 11 is a cyclohexane solution of isopentenol with a concentration of 0.21 kg / L;

[0056] The flow ratio of the three materials is controlled at 66:298:1, and the residence time in reverse 5 is 120 min;

[0057] (7) The reaction liquid flowing out of reactor 5 is feed 12, which is a solution of acetal in cyclohexane with a concentration of 0.22 kg / L. Feed 12 is pumped into reactor 6 via pump 12 and subjected to a series Claisen-Cope rearrangement reaction at 200°C for 5 minutes. The reaction liquid flowing out of reactor 6 flows through back pressure valve 3, which regulates the reaction pressure in reactor 6. The effluent from back pressure valve 3 is pumped into tank 4 via pump 13. Tank 4 is used to recover the cyclohexane solution of isopentenol. The recovered reaction liquid is pumped to tank 5 via pump 14. Tank 5 is used to distill and purify the product citral with a purity of 96%. The citral yield is 70%.

[0058] Example 2

[0059] (1) Prepared materials 1 and 2 are pumped to mixing tank 1 via pumps 1 and 2 respectively for thorough mixing; after mixing, the mixture is directly fed into reactor 1 via connecting pipes and subjected to chlorination reaction at -10℃ for 18 minutes; the reaction liquid flowing out of reactor 1 enters tank 1, which is a stirred tank with a filter core in the middle, i.e., a filter tank, used to filter out insoluble solids, and the filtrate is used as material 3; wherein:

[0060] Material 1 is a dichloromethane suspension of alumina with a concentration of 0.28 kg / L; Material 2 is a mixture of isoprene with a concentration of 0.52 kg / L and thionyl chloride with a concentration of 0.46 kg / L; the flow ratio of Material 1 to Material 2 is 5:1; the time in reaction 1 is 18 min; Material 3 is an isoprene dichloromethane solution with a concentration of 0.12 kg / L.

[0061] (2) Material 3 is fully mixed in mixing 2 by pump 3 and material 4 conveyed by pump 4, and then directly enters reaction 2 for esterification reaction at 110°C for 55 minutes.

[0062] Material 4 is a dichloromethane suspension containing sodium acetate at a concentration of 0.59 kg / L and tetrabutylammonium bromide at a concentration of 0.22 kg / L; the flow ratio of materials 3 and 4 is 6.8:1, and the retention time in reaction 2 is 55 min;

[0063] (3) The reaction liquid flowing out from reactor 2 enters mixer 3 and is mixed evenly with material 5 conveyed by pump 5 in mixer 3. Then it enters reactor 3 and undergoes hydrolysis reaction at 110°C for 12 minutes; wherein:

[0064] Material 5 is a 15% sodium hydroxide aqueous solution; the flow ratio of the reaction solution to material 5 is 3.8:1, and the retention time in reaction 3 is 12 min;

[0065] (4) The outflowing reaction liquid from reaction 3 flows through back pressure valve 1. The function of back pressure valve 1 is to regulate the reaction pressure in reaction 2 and reaction 3. The outflowing liquid from back pressure valve 1 directly enters fraction 1. In fraction 1, the organic phase and the aqueous phase are separated. Fraction 1 is equipped with an upper outlet and a lower outlet. The upper outlet is connected to tank 2, which is used to store the separated upper waste liquid. The lower outlet is connected to pump 6, which transports the lower liquid to the distiller. The function of the distiller is to remove the solvent dichloromethane from the reaction liquid. The recovered solvent dichloromethane is condensed and stored in tank 3. The liquid after removing the solvent is material 6, which is a 0.82 kg / L isopentenol solution.

[0066] (5) Material 6 is pumped to mixer 4 by pump 7. Mixer 4 is a four-way micro mixer with three inlets and one outlet. The other two inlets of mixer 4 are: the oxygen inlet of material 7 by gas flow controller and the water inlet of material 8 by pump 8. The flow ratio of the three channels is controlled to be 5.9:120:1. The mixture is evenly mixed in mixer 4 and then enters reverse 4 for oxidation reaction at 75°C for 4 minutes.

[0067] (6) The reaction liquid flowing out of reaction 4 flows through back pressure valve 2, which is used to regulate the reaction pressure in reaction 4; the liquid flowing out of back pressure valve 2 enters separator 2, where the organic phase and aqueous phase are separated into layers. Separator 2 is provided with an upper outlet and a lower outlet; the upper outlet is connected to pump 9, and the lower outlet is connected to pump 8; material 9 is transported to mixer 5 by pump 9. Mixer 5 is a four-way micro mixer with three inlets and one outlet. The other two inlets of mixer 5 are: the inlet of material 11 supplied by pump 11 and the inlet of material 10 supplied by pump 10; the flow ratio of the three is controlled to be 66:298:1. After being mixed evenly in mixer 5, the mixture enters reaction 5 and undergoes aldol condensation reaction at 100°C for 120 minutes;

[0068] Material 9 is a mixed solution of isopentenol and isopentenal with a concentration of 48% and 52% respectively.

[0069] Material 10 is an aqueous solution of toluenesulfonic acid with a concentration of 4.3 kg / L, which is the inlet for conveying materials;

[0070] Material 11 is a cyclohexane solution of isopentenol with a concentration of 0.22 kg / L;

[0071] The flow ratio of the three materials is controlled at 66:298:1, and the residence time in reverse 5 is 130 min;

[0072] (8) The reaction liquid flowing out of reactor 5 is feed 12, which is a solution of acetal in cyclohexane with a concentration of 0.23 kg / L. Feed 12 is pumped into reactor 6 via pump 12 and subjected to a series Claisen-Cope rearrangement reaction at 200°C for 7 minutes. The reaction liquid flowing out of reactor 6 flows through back pressure valve 3, which regulates the reaction pressure in reactor 6. The effluent from back pressure valve 3 is pumped into tank 4 via pump 13. Tank 4 is used to recover the cyclohexane solution of isopentenol. The recovered reaction liquid is pumped to tank 5 via pump 14. Tank 5 is used to distill and purify the product citral with a purity of 94%. The citral yield is 72%.

[0073] Example 3

[0074] (1) Prepared materials 1 and 2 are pumped to mixing tank 1 via pumps 1 and 2 respectively for thorough mixing; after mixing, the mixture is directly fed into reactor 1 via connecting pipes and subjected to chlorination reaction at -12℃ for 20 minutes; the reaction liquid flowing out of reactor 1 enters tank 1, which is a stirred tank with a filter core in the middle, i.e., a filter tank, used to filter out insoluble solids, and the filtrate is used as material 3; wherein:

[0075] Material 1 is a dichloromethane suspension of alumina with a concentration of 0.26 kg / L; Material 2 is a mixture of isoprene with a concentration of 0.5 kg / L and thionyl chloride with a concentration of 0.44 kg / L; the flow ratio of Material 1 to Material 2 is 5.6:1; the time in reaction 1 is 20 min; Material 3 is an isoprene dichloromethane solution with a concentration of 0.10 kg / L.

[0076] (2) Material 3 is fully mixed in mixing 2 by pump 3 and material 4 conveyed by pump 4, and then directly enters reaction 2 for esterification reaction at 120°C for 54 minutes.

[0077] Material 4 is a dichloromethane suspension containing sodium acetate at a concentration of 0.57 kg / L and tetrabutylammonium bromide at a concentration of 0.2 kg / L; the flow ratio of material 3 to material 4 is 6.6:1, and the retention time in reaction 2 is 54 min;

[0078] (3) The reaction liquid flowing out from reactor 2 enters mixer 3 and is mixed evenly with material 5 conveyed by pump 5 in mixer 3. Then it enters reactor 3 and undergoes hydrolysis reaction at 100°C for 10 minutes; wherein:

[0079] Material 5 is a 10% sodium hydroxide aqueous solution; the flow ratio of the reaction solution to material 5 is 3.8:1, and the retention time in reaction 3 is 10 min;

[0080] (4) The outflowing reaction liquid from reaction 3 flows through back pressure valve 1. The function of back pressure valve 1 is to regulate the reaction pressure in reaction 2 and reaction 3. The outflowing liquid from back pressure valve 1 directly enters fraction 1. In fraction 1, the organic phase and the aqueous phase are separated. Fraction 1 is equipped with an upper outlet and a lower outlet. The upper outlet is connected to tank 2, which is used to store the separated upper waste liquid. The lower outlet is connected to pump 6, which transports the lower liquid to the distiller. The function of the distiller is to remove the solvent dichloromethane from the reaction liquid. The recovered solvent dichloromethane is condensed and stored in tank 3. The liquid after removing the solvent is material 6, which is a 0.88 kg / L isopentenol solution.

[0081] (5) Material 6 is pumped to mixer 4 by pump 7. Mixer 4 is a four-way micro mixer with three inlets and one outlet. The other two inlets of mixer 4 are: the oxygen inlet of material 7 by gas flow controller and the water inlet of material 8 by pump 8. The flow ratio of the three channels is controlled to be 5.7:120:1. The mixture is evenly mixed in mixer 4 and then enters reverse 4 for oxidation reaction at 70°C for 3 minutes.

[0082] (6) The reaction liquid flowing out of reaction 4 flows through back pressure valve 2, which is used to regulate the reaction pressure in reaction 4; the liquid flowing out of back pressure valve 2 enters separator 2, where the organic phase and aqueous phase are separated into layers. Separator 2 is provided with an upper outlet and a lower outlet; the upper outlet is connected to pump 9, and the lower outlet is connected to pump 8; material 9 is transported to mixer 5 by pump 9. Mixer 5 is a four-way micro mixer with three inlets and one outlet. The other two inlets of mixer 5 are: the inlet of material 11 supplied by pump 11 and the inlet of material 10 supplied by pump 10; the flow ratio of the three is controlled to be 66:298:1. After being mixed evenly in mixer 5, the mixture enters reaction 5 and undergoes aldol condensation reaction at 100°C for 120 minutes;

[0083] Material 9 is a mixed solution of isopentenol and isopentenal with a concentration of 45% and 55% respectively.

[0084] Material 10 is an aqueous solution of toluenesulfonic acid with a concentration of 4.3 kg / L, which is the inlet for conveying materials;

[0085] Material 11 is a cyclohexane solution of isopentenol with a concentration of 0.21 kg / L;

[0086] The flow ratio of the three materials is controlled at 66:298:1, and the residence time in reverse 5 is 120 min;

[0087] (9) The reaction liquid flowing out of reactor 5 is feed 12, which is a solution of acetal in cyclohexane with a concentration of 0.22 kg / L. Feed 12 is pumped into reactor 6 via pump 12 and subjected to a series Claisen-Cope rearrangement reaction at 240°C for 5 minutes. The reaction liquid flowing out of reactor 6 flows through back pressure valve 3, which regulates the reaction pressure in reactor 6. The effluent from back pressure valve 3 is pumped into tank 4 via pump 13. Tank 4 is used to recover the cyclohexane solution of isopentenol. The recovered reaction liquid is pumped to tank 5 via pump 14. Tank 5 is used to distill and purify the product citral with a purity of 95%. The citral yield is 66%.

[0088] It should be noted that although the above embodiments have been described herein, this does not limit the scope of patent protection of the present invention. Therefore, any changes and modifications made to the embodiments described herein based on the innovative concept of the present invention, or equivalent structural or procedural transformations made using the content of the present invention's specification and drawings, directly or indirectly applying the above technical solutions to other related technical fields, are all included within the scope of protection of the claims of the present invention.

Claims

1. A fully continuous chemical synthesis method for citral, characterized in that, A fully continuous chemical synthesis apparatus is constructed by connecting multiple feed pumps, mixers, microreactors, back pressure valves, liquid-liquid separators, and online filters according to a linear synthesis route for citral; the specific synthesis steps are as follows: (1) Prepared materials 1 and 2 are pumped to mixing tank 1 via pumps 1 and 2 respectively for thorough mixing; after mixing, the mixture is directly fed into reactor 1 via connecting pipes for chlorination reaction at -15-0℃ for 15-25 minutes; the reaction liquid flowing out of reactor 1 enters tank 1, which is a stirred tank with a filter core in the middle, i.e., a filter tank, used to filter out insoluble solids, and the filtrate is used as material 3; wherein: Component 1 is a dichloromethane suspension of alumina with a concentration of 0.26-0.36 kg / L; Component 2 is a mixture of isoprene with a concentration of 0.5-0.6 kg / L and thionyl chloride with a concentration of 0.44-0.54 kg / L; the flow ratio of Component 1 to Component 2 is 5.6-6:1; the time in reaction 1 is 15-25 min; Component 3 is an isoprene dichloromethane solution with a concentration of 0.10-0.13 kg / L. (2) Material 3 is fully mixed in mixing 2 by pump 3 and material 4 conveyed by pump 4, and then directly enters reaction 2 for esterification reaction at 100-120℃ for 50-80 minutes. Material 4 is a dichloromethane suspension containing sodium acetate at a concentration of 0.57-0.67 kg / L and tetrabutylammonium bromide at a concentration of 0.2-0.3 kg / L; the flow ratio of material 3 to material 4 is 6.6-7.6:1, and the time in reaction 2 is 50-80 min; (3) The reaction liquid flowing out from reactor 2 enters mixer 3 and is mixed evenly with material 5 conveyed by pump 5 in mixer 3. Then it enters reactor 3 and undergoes hydrolysis reaction at 100-120℃ for 10-15 minutes; wherein: Material 5 is a 10%-30% sodium hydroxide aqueous solution; the flow ratio of the reaction solution to material 5 is 3.8-4:1, and the retention time in reaction 3 is 10-15 min; (4) The outflowing reaction liquid from reaction 3 flows through back pressure valve 1. The function of back pressure valve 1 is to regulate the reaction pressure in reaction 2 and reaction 3. The outflowing liquid from back pressure valve 1 directly enters fraction 1. In fraction 1, the organic phase and the aqueous phase are separated. Fraction 1 is equipped with an upper outlet and a lower outlet. The upper outlet is connected to tank 2, which is used to store the separated upper waste liquid. The lower outlet is connected to pump 6, which transports the lower liquid to the distiller. The function of the distiller is to remove the solvent dichloromethane from the reaction liquid. The recovered solvent dichloromethane is condensed and stored in tank 3. The liquid after removing the solvent is material 6, which is an isopentenol solution with a concentration of 0.88-0.95 kg / L. (5) Material 6 is pumped to mixer 4 by pump 7. Mixer 4 is a four-way micro mixer with three inlets and one outlet. The other two inlets of mixer 4 are: the oxygen inlet of material 7 by gas flow controller and the water inlet of material 8 by pump 8. The flow ratio of the three channels is controlled to be 5.7-7:120-150:

1. The mixture is evenly mixed in mixer 4 and then enters reverse 4 for oxidation reaction at 70-90℃ for 3-7 minutes. (6) The reaction liquid flowing out of reaction 4 flows through back pressure valve 2, which is used to regulate the reaction pressure in reaction 4; the liquid flowing out of back pressure valve 2 enters separator 2, where the organic phase and aqueous phase are separated into layers. Separator 2 is provided with an upper outlet and a lower outlet; the upper outlet is connected to pump 9, and the lower outlet is connected to pump 8; material 9 is transported to mixer 5 by pump 9. Mixer 5 is a four-way micro mixer with three inlets and one outlet. The other two inlets of mixer 5 are: the inlet of material 11 supplied by pump 11 and the inlet of material 10 supplied by pump 10; the flow ratio of the three is controlled to be 66-76:298-308:

1. After being mixed evenly in mixer 5, the mixture enters reaction 5 and undergoes aldol condensation reaction at 100-130℃ for 120-150 minutes; Material 9 is a mixed solution of isopentenol with a concentration of 50%-55% and isopentenal with a concentration of 45%-50%; Material 10 is an aqueous solution of toluenesulfonic acid with a concentration of 4.3-5 kg / L, which is the inlet for conveying materials; Material 11 is a cyclohexane solution of isopentenol with a concentration of 0.21-0.29 kg / L; The flow ratio of the three materials is controlled at 66-76:298-308:1, and the residence time in the mixture is 120-150 min. (7) The reaction liquid flowing out from reactor 5 is material 12, which is a solution of acetal in cyclohexane with a concentration of 0.22-0.26 kg / L; material 12 is pumped into reactor 6 through pump 12 and subjected to a series Claisen-Cope rearrangement reaction at 200-280℃ for 5-10 minutes; the reaction liquid flowing out from reactor 6 flows through back pressure valve 3, the function of which is to regulate the reaction pressure in reactor 6; the outflow liquid from back pressure valve 3 is pumped into tank 4 through pump 13, the function of which is to recover the cyclohexane solution of isopentenol; the reaction liquid after recovery is pumped to tank 5 through pump 14, the function of which is to distill and purify the product citral; Among them, Mix 1 to Mix 5 are abbreviations for the first to fifth micro mixers, Reverse 1 to Reverse 6 are abbreviations for the first to sixth microreactors, Back pressure valve 1 to Back pressure valve 3 are abbreviations for the first to third back pressure valves, and Separator 1 and Separator 2 are abbreviations for the first liquid-liquid separator and the second liquid-liquid separator.

2. The fully continuous chemical synthesis method for citral according to claim 1, characterized in that, Pumps 1 and 4 are peristaltic pumps for conveying slurry, while pumps 2, 3, and 5-14 are plunger pumps for conveying solutions.

3. The fully continuous chemical synthesis method for citral according to claim 1, characterized in that, Mixer 1 to Mixer 5 are three micro-mixers connected in series in a U-shape. The fluid channel size is circular or square with a diameter of 100μm-20mm, a length of 1-100cm, and a flow rate of 1-3000mL / min.

4. The fully continuous chemical synthesis method for citral according to claim 1, characterized in that, Reactor 1, Reactor 2, Reactor 3, and Reactor 6 are tubular microreactors with built-in X-shaped mixing components and fluid channel dimensions of 100μm-20mm; Reactor 4 is a fixed-bed microreactor filled with Pt / C catalyst and its fluid channel dimensions are 100μm-20mm; Reactor 5 is a CSTR reactor, consisting of three 25-50mL jacketed glass bottles, a water separator, and a condenser.

5. The fully continuous chemical synthesis method for citral according to claim 1, characterized in that, The first and second separators are liquid-liquid separators designed based on the principle of gravity settling. The inner diameter of the separator is 1-20cm and the height is 1-200cm.

6. The fully continuous chemical synthesis method for citral according to claim 1, characterized in that, Tank 1 is a filter tank with a sand core filter layer; tanks 2, 3, and 4 are liquid storage tanks, and tank 5 is a distillation tank.

7. The fully continuous chemical synthesis method for citral according to claim 1, characterized in that, The back pressure valves 1, 2, and 3 have connecting pipes with dimensions of 1.6mm-10mm and pressure conditions ranging from 0.1 to 10.0MPa.

Images