CN1260395C - Synthesis of dimethyl benzaldehyde - Google Patents

Abstract

The present invention relates to a method for synthesizing 3, 5-dimethyl benzaldehyde (DBAL) by indirectly electrolyzing and oxidizing 1, 3, 5-tri-methylbenzene, for synthesizing 2, 3-DBAL and 2, 6-DBAL by indirectly electrolyzing and oxidizing 1, 2, 3-tri-methylbenzene, for synthesizing 2, 4-DBAL, 3, 4-DBAL and 2, 5-DBAL by indirectly electrolyzing and oxidizing 1, 2, 4-tri-methylbenzene. The method uses an electrolytic tank without membranes with Pb as a cathode, Pb containing Pb alloy or PbO#2 as an anode, MnSO#4-H#2SO#4 having the current density Da of 3 to 30A. dm#+[-2] as an electrolyte to prepare high-valence oxide of manganese mainly containing Mn#+[4+] and Mn#+[3+], namely a Mn oxidation medium which respectively oxidizes 1, 3, 5-tri-methylbenzene to prepare 3, 5-DBAL, 1, 2, 3-tri-methylbenzene to prepare 2, 3-DBAL and 2, 6-DBAL, 1, 2, 4-tri-methylbenzene to prepare 2, 4-DBAL, 3, 4-DBAL and 2, 5-DBAL. Refined products having the purity larger than or equal to 98% are obtained by decompression rectification.

Description

The synthesization of dimethyl method of benzaldehyde

The present invention relates to the novel synthesis of 6 kinds of dimethylbenzaldehydes (below be abbreviated as DBAL) isomer, these 6 kinds of DBAL isomer are: 3, and 5-DBAL, 2,3-DBAL, 2,6-DBAL, 2,4-DBAL, 3,4-DBAL and 2,5-DBAL.

These 6 kinds of DBAL isomer all are important fine-chemical intermediates, are widely used in medicine, macromolecular material, dyestuff, agricultural chemicals and other organic syntheses.Will point out that especially these 6 kinds of DBAL may be used to synthetic transparent nucleator for polypropylene, be non-toxic plastic auxiliary agent of new generation, is widely used in packaging material for food.

Traditional synthesizes 3,5-DBAL, 2,3-DBAL, 2,6-DBAL, 2,4-DBAL, 3,4-DBAL and 2, the method for 5-DBAL is a lot, but all is the method for continuing to use general organic synthesis without exception, the synthetic operational path is long, and step is numerous, and subsidiary material are used manyly, severe reaction conditions, side reaction is many, and product yield is low, and refining quite difficulty, waste is many, and environmental pollution is serious, in environmental consciousness growing 21 century, above-mentioned traditional methodology of organic synthesis is restricted, even is eliminated.

Synthetic method a kind of cleaning, free of contamination, highly selective has shown great vitality, and it is the method for organic electrosynthesis of being developed out by electrochemistry and organic chemistry two subject crossing.Electrolytic synthesis does not generally consume or consumes less subsidiary material except being the product with feedstock conversion, unique consumption be clean electric power, so be a kind of Green Chemical Technology, meet the new concept of 21 century environment protection.

Now with 2,4-DBAL is an example, and its traditional synthesis process process divided for three steps: synthetic, decomposition and refining.

(1) synthetic: by traditional methodology of organic synthesis, be raw material with exsiccant m-xylene and CO, liquid superacid HF-BF ₃Be catalyzer, be lower than under the condition of 0 ℃ and pressurization 2.0MPa, make the stable comple of m-xylene and CO reaction generation DBAL.This reaction is carried out fast, and emits a large amount of reaction heat, therefore must stir constantly and safeguard that low temperature is beneficial to the absorption of CO gas.

(2) decompose: the DBAL complex compound that is come out by synthesis reactor is sent into decomposition tower and is decomposed, and is heating medium with benzene, under controlled temperature＞100 ℃ and the 0.4MPa, benzene vapor with heat heats the DBAL complex compound, make its decomposition obtain rough DBAL, after the DBAL complex compound decomposes, volatile HF, BF ₃Separate HF liquefaction after cooling off, BF by cat head ₃Because of boiling point is-100 ℃, so be to be gaseous state, the two circulates respectively and returns synthetic tower again.

(3) refining: the product of being discharged by the decomposition tower bottom is rough DBAL, wherein contains benzene, unreacted m-xylene and low boilers and high boiling product.Separate by distillation, benzene returns decomposition tower, and unreacted m-xylene returns synthesis reactor, isolate low, high boiling product at last after, obtain purified DBAL product.

Though this method is present industrial preparation 2, there are many drawbacks in one of main method of 4-DBAL:

At first, synthesis condition is quite harsh.Use liquid superacid HF-BF when synthetic ₃As catalyzer.As everyone knows, HF, BF ₃Be the very strong compound of toxicity, and have extremely strong corrodibility, glass also is corroded, so all synthesis device, pipeline, valve and metrical instruments all will use anti-HF and BF in this synthesis system ₃The corrosive material, thus make the cost and the maintenance cost costliness of equipment.

The second, need keep low temperature and high pressure when synthetic.At HF-BF ₃Catalyzer exists down, and the reaction of CO and m-xylene will keep the pressure of temperature of reaction＜0 ℃ and 2.0MPa, could generate stable DBALHBF ₄Complex compound because this reaction is thermopositive reaction, moment is emitted a large amount of reaction heat, so to be equipped with stirring in the reactor, heat conduction and refrigerating system, to guarantee system temperature of reaction＜0 ℃, just can keep stable synthesis condition.

The 3rd, well-known, HF-BF ₃It is a kind of good hydroformylation catalyst; yet it equally also has very strong katalysis to reactions such as the isomerization of m-xylene and disproportionations under identical temperature; so if reaction conditions is if there is imbalance in the building-up reactions of m-xylene and CO; then make the isomerization and the disproportionation reaction of dimethylbenzene become quite serious; even the reaction tendency that a presumptuous guest usurps the role of the host occurs, thereby be difficult to obtain DBALHBF ₄

The 4th, decomposition reaction column structure complexity.Decomposition reaction is heating medium with benzene, by entering at the bottom of the tower in the tower, by well heater be heated＞100 ℃, pressure is adjusted downward to 0.4MPa.DBALHBF ₄Complex compound decomposes after heating, and obtain thick DBAL and discharge at the bottom of by tower, and HF and BF ₃Volatile one-tenth gaseous state is separated by cat head, and HF is liquid state, BF after cooling off ₃Be gaseous state, the two circulates respectively and returns synthesis reactor.Make a general survey of the shift direction of above-mentioned decomposition reaction process material composition and each material etc., cause this decomposition reaction column structure complexity, technological operation is difficulty rather, only under material balance and heat balance, just can make this tower smooth running, attends to one thing and lose sight of another otherwise easily produce.

The 5th, refining difficulty.Used raw material is a C8 aronmatic, and general C8 aronmatic has four kinds of isomer, i.e. o-Xylol, m-xylene, p-Xylol and ethylbenzene.At HF-BF ₃Catalyzer exists down, and by the CO formylation, ethylbenzene can generate ethylbenzene formaldehyde, 231 ℃ of its boiling points and 2, and the boiling point of 4-DBAL only differs 2 ℃ for 233 ℃, is difficult to separation, thereby has influenced 2, the purity of 4-DBAL and use value.

Step is numerous as mentioned above in traditional methodology of organic synthesis in order to overcome, and subsidiary material are used manyly, cryogenic high pressure, and side reaction is many, many drawbacks such as refining difficulty, and it is raw material that the present invention has set up with the trimethylbenzene, the selective electrolysis oxidation style is synthesized DBAL.The present invention is achieved by following technical scheme.

1. electrolytic synthesis 3,5-DBAL, 2,3-DBAL, 2,6-DBAL, 2,4-DBAL, 3,4-DBAL, 2, the preparation method of 5-DBAL is characterized in that, in undivided cell, is negative electrode with Pb, Pb, contains Pb alloy or oPbO ₂Be anode, feed direct current electrolysis MnSO ₄-H ₂SO ₄Electrolytic solution makes and mainly contains Mn ⁴⁺And Mn ³⁺The high oxide of manganese be the Mn oxidation medium, then the Mn oxidation medium is moved in the oxidation reactor, selective oxidation 1,3, the 5-trimethylbenzene generates 3,5-DBAL; The oxidation 1 generates 2,3-DBAL and 2,6-DBAL; Oxidation 1,2, the 4-trimethylbenzene generates 2,4-DBAL, 3,4-DBAL and 2,5-DBAL can make 3 of purity 〉=98.0% through rectification under vacuum again, 5-DBAL, 2,6-DBAL, 2,3-DBAL, 2,4-DBAL, 3,4-DBAL and 2,5-DBAL.

2. according to above-mentioned 1 described preparation method, it is characterized in that electrolytic solution is by MnSO ₄And H ₂SO ₄Form H in the electrolytic solution ₂SO ₄Content between 2.0～8.0mol/L, MnSO ₄Content is between 0.1～3.0mol/L.

3. according to above-mentioned 1 described preparation method, it is characterized in that electrolysis MnSO ₄-H ₂SO ₄The bath temperature of electrolytic solution between 10～60 ℃, anodic current density is at 3～30Adm during electrolysis ^-2Between, electrolysis makes and mainly contains Mn till the theoretical current consumption of Mn ⁴⁺And Mn ³⁺The high oxide of manganese.

4. according to above-mentioned 1 described preparation method, it is characterized in that the oxidation medium immigration of the Mn that electrolysis generates is equipped with in the oxidation reactor of stirring, heating, temperature control, condensation and thermometer, and add Mn ⁴⁺And Mn ³⁺1,3 of 2～4 times of theoretical amount, 5-trimethylbenzene or 1 or 1,2, the 4-trimethylbenzene, stirring reaction at a certain temperature, by 1,3, the 5-trimethylbenzene generates 3, and 5-DBAL generates 2 by 1,3-DBAL and 2,6-DBAL; By 1,2, the 4-trimethylbenzene generates 2,4-DBAL, 3,4-DBAL and 2,5-DBAL.

5. according to above-mentioned 4 described preparation methods, it is characterized in that the temperature of reaction of Mn oxidation medium in oxidation reactor is between 50～130 ℃.

6. according to above-mentioned 4 described preparation methods, it is characterized in that the reaction times of Mn oxidation medium in oxidation reactor to be the Mn oxidation medium all be converted into by atropurpureus colourless till faint yellow.

At first, in aseptate electrolyzer, be negative electrode with Pb, Pb, contain Pb alloy or PbO ₂Be anode, under 10～60 ℃ of bath temperatures, with 3～30Adm ^-2The anodic current density electrolysis contain the free H of 2.0～8.0mol/L ₂SO ₄MnSO with 0.1～3.0mol/L ₄The electrolytic solution of forming, electrolysis is to Mn ²⁺---→ Mn ⁴⁺Till the theoretical current consumption, make and mainly contain Mn ⁴⁺And Mn ³⁺The high oxide of manganese as oxidation medium, the Mn oxidation medium is moved into by electrolyzer is equipped with in stirring, heating, temperature control, condensation and the thermometric oxidation reactor then, add with Mn ⁴⁺+ Mn ³⁺1,3 of 2～4 times of theoretical amount, the 5-trimethylbenzene, or 1 or 1,2,4-trimethylbenzene, stirring reaction, control reaction temperature is between 50～130 ℃, about 0.5～1 hour reaction times, atropurpureus Mn oxidation medium disappears, and occurs colourless to flaxen oil phase, can stop stirring reaction, divide and get oil phase.Water is for containing Mn ²⁺Acid MnSO ₄Solution reclaims the product of minimal amounts of dissolved at aqueous phase with the benzene extraction, and the water after the extraction returns electrolytic tank electrolysis and is regenerated as the Mn oxidation medium, enters the oxidizing reaction of next round again.Benzene extraction and oil phase merge, and can obtain highly purified product through rectification under vacuum.

In sum, the inventive method is used the main salt of cheap manganese salt as oxidation medium, and the moiety of electrolytic solution is simple, and MnSO is only arranged ₄And H ₂SO ₄, in aseptate electrolyzer, the electrolytic condition of controlling well carries out electrolysis just can obtain the Mn oxidation medium, and not only preparation is easy but also regeneration is also easy.Its biggest advantage has four aspects: one, the Mn oxidation medium can be realized recycling in building-up process, does not produce pollutents such as waste water, waste residue, belongs to Green Chemical Technology; Two, because the Mn oxidation medium recycles, can produce a large amount of products, production cost is descended significantly, realize high added value and Sustainable development with limited resources; Three, the redox potential E of Mn oxidation medium ⁰(1.51V Vs NHE 296.16K), to the oxidizing reaction selectivity height of trimethylbenzene, thereby side reaction is few, and aldehyde productive rate height is refining easily, the pure rate height of product; Four, three methyl can only be with the electrolytic oxidation of this Mn oxidation medium on the phenyl ring, and one of selective oxidation is a carbonyl, and it is not oxidized to keep two methyl, in any case and be also out of the question with general traditional methodology of organic synthesis.

The present invention is further specified by following embodiment.

Embodiment one.In the uncovered undivided cell of the columned useful volume 1200ml of φ 110mm * h140mm, install the dull and stereotyped anode of pure lead of 120mm (height) * 90mm (wide), its useful area 1.57dm with electronic stirring ², respectively load onto the pure plumbous planar cathode of a slice 120mm (height) * 45mm (wide) in the anode both sides, the useful area of every negative electrode is 0.39dm ², in electrolyzer, inject 1000ml then by 8.0mol/LH ₂SO ₄With 0.65mol/L MnSO ₄The electrolytic solution of forming shallow rosy, the direct current electrolysis of input 6.28A is stirred electrolytic solution and is controlled 25 ± 3 ℃ of the temperature of electrolytic solution, energising electrolysis 333min, stop electrolysis and stirring when importing electric weight 34.84Ah altogether, obtaining the atropurpureus electrolysate is the Mn oxidation medium.Shift out in the four-necked bottle that the Mn oxidation medium is injected into 2000ml, this four-necked bottle is equipped with the mercury contact thermometer of electronic stirring, condensation, thermo detector and automatic temperature control system, utilize the benzvalene form electric heating cooker that atropurpureus Mn oxidation medium is preheated to 55 ± 5 ℃, add then 180ml do not have purity of color be 99% 1,3, the 5-trimethylbenzene, stirring reaction, after 2 hours, reaction solution gradually becomes red-purple by atropurpureus, at last for extremely light yellow extremely colourless, last 128min altogether, reaction finishes and cools to room temperature, and it is settlement separate that reaction solution moves into separating funnel, divides water intaking phase, oil phase.Water is dissolved in wherein 3 with 25ml benzene extraction at every turn, and 5-DBAL repeats 3 times.Extraction back water can return electrolyzer and carry out electrolytic regeneration, realizes recycling.The oil phase that the oil phase of extraction and aforementioned oxidizing reaction branch are got merges, and can obtain 3 of purity 98.8% by rectification under vacuum, and 5-DBAL 37.5g, the productive rate of entire reaction course product are 85%.

Embodiment two.In the uncovered undivided cell of the columned useful volume 1200ml of φ 110mm * h140mm, install 120mm (height) * 90mm (wide) Ti base β-PbO with electronic stirring ₂Dull and stereotyped anode a slice, its useful area 1.57dm ², respectively load onto the pure plumbous planar cathode of a slice 120mm (height) * 22.5mm (wide) in the anode both sides, the useful area of every negative electrode is 0.20dm ², in electrolyzer, inject then by 2.0mol/L H ₂SO ₄With 2.8mol/L MnSO ₄The electrolytic solution 1000ml that forms, the direct current of input 47.1A starts agitator, 45 ± 5 ℃ of control electrolyte temperatures, electrolysis 191.4min imports the 150.1Ah electric weight altogether, stops electrolysis, obtains atropurpureus electrolysate Mn oxidation medium.The Mn oxidation medium is moved in the four-necked bottle oxidation reactor of the 2000ml identical, oxidation medium is preheated to 90 ± 5 ℃ simultaneously with embodiment one, progressively add 500ml purity and be 99% 1,2,4-trimethylbenzene, stirring reaction, behind about 63min, reaction solution gradually becomes red-purple by atropurpureus, becomes lilac at leisure again, becomes at last in the clarification pale yellow solution to have yellow oil, reaction finishes, cool to room temperature, it is settlement separate that reaction solution moves to separating funnel, divides water intaking phase, oil phase.Water is dissolved in wherein DBAL with the extraction of 25ml benzene at every turn, repeats 3 times.Extraction back water can return electrolyzer and carry out electrolytic regeneration, realizes recycling.The oil phase that the oil phase of extraction and aforementioned oxidizing reaction branch are got merges, can obtain 3 of purity 98.5% by rectification under vacuum, 2 of 4-DBAL 117.4g, purity 99%, 2 of 4-DBAL 35.5g and purity 98%, 5-DBAL 1.58g, the total aldehyde production rate of reaction process is 81%.

Embodiment three.Use and implement two identical electrolyzer, electrode and other devices, injection is by 4.8mol/LH ₂SO ₄With 0.8mol/L MnSO ₄The electrolytic solution 1000ml that forms, the direct current of input 23.6A starts agitator, 30 ± 5 ℃ of control electrolyte temperatures, electrolysis 109min imports the 42.88Ah electric weight altogether, stops electrolysis, obtains atropurpureus Mn oxidation medium.The Mn oxidation medium is moved in the four-necked bottle oxidation reactor of the 2000ml identical with embodiment one, oxidation medium is preheated to 125 ± 5 ℃ simultaneously, progressively add 200ml purity and be 98.5% 1,2,3-trimethylbenzene, stirring reaction, behind about 25min, the reaction solution color progressively shoals, and becomes red-purple, lilac by atropurpureus, becomes at last in the clarification light red solution to have yellow oil.Reaction finishes, and cools to room temperature, and it is settlement separate that reaction solution moves to separating funnel, divides water intaking phase, oil phase.Water is dissolved in wherein DBAL, triplicate with the extraction of 25ml benzene at every turn.Extraction back water can return electrolyzer and carry out electrolytic regeneration, realizes recycling.The oil phase that the oil phase of extraction and aforementioned oxidizing reaction branch are got merges, and can obtain 2 of purity 99% by rectification under vacuum, 2 of 3-DBAL 42g and purity 98.3%, and 6-DBAL4.8g, the total aldehyde production rate of reaction process is 86%.

Claims (6)

1. electrolytic synthesis 3,5-dimethylbenzaldehyde (being abbreviated as DBAL below the dimethylbenzaldehyde), 2,3-DBAL, 2,6-DBAL, 2,4-DBAL, 3,4-DBAL, 2, the preparation method of 5-DBAL is characterized in that, in undivided cell, be negative electrode with Pb, Pb, contain Pb alloy or PbO ₂Be anode, feed direct current electrolysis MnSO ₄-H ₂SO ₄Electrolytic solution makes and mainly contains Mn ⁴⁺And Mn ³⁺The high oxide of manganese, promptly the Mn oxidation medium moves to the Mn oxidation medium in the oxidation reactor then, selective oxidation 1,3, the 5-trimethylbenzene generates 3,5-DBAL; The oxidation 1 generates 2,3-DBAL and 2,6-DBAL; Oxidation 1,2, the 4-trimethylbenzene generates 2,4-DBAL, 3,4-DBAL and 2,5-DBAL can make 3 of purity 〉=98% through rectification under vacuum again, 5-DBAL, 2,6-DBAL, 2,3-DBAL, 2,4-DBAL, 3,4-DBAL and 2.5-DBAL.

2. preparation method according to claim 1 is characterized in that electrolytic solution is by MnSO ₄And H ₂SO ₄Form H in the electrolytic solution ₂SO ₄Content between 2.0～8.0mol/L, MnSO ₄Content is between 0.1～3.0mol/L.

3. preparation method according to claim 1 is characterized in that electrolysis MnSO ₄-H ₂SO ₄The bath temperature of electrolytic solution is between 10～60 ℃, and anodic current density is at 3～30Adm during electrolysis ^-2Between, electrolysis makes and mainly contains Mn till the theoretical current consumption of Mn ⁴⁺And Mn ³⁺The high oxide of manganese.

4. preparation method according to claim 1 is characterized in that the oxidation medium immigration of the Mn that electrolysis generates is equipped with in the oxidation reactor of stirring, heating, temperature control, condensation and thermometer, and adds Mn ⁴⁺+ Mn ³⁺1,3 of 2～4 times of theoretical amount, 5-trimethylbenzene or 1 or 1,2, the 4-trimethylbenzene, stirring reaction at a certain temperature, by 1,3, the 5-trimethylbenzene generates 3, and 5-DBAL generates 2 by 1,3-DBAL and 2,6-DBAL; By 1,2, the 4-trimethylbenzene generates 2,4-DBAL, 3,4-DBAL and 2,5-DBAL.

5. preparation method according to claim 4 is characterized in that the temperature of reaction of Mn oxidation medium in oxidation reactor is between 50～130 ℃.

6. preparation method according to claim 4 is characterized in that the reaction times of Mn oxidation medium in oxidation reactor to be the Mn oxidation medium all is converted into by atropurpureus colourless till faint yellow.