A kind of preparation method of paraldehyde

Abstract

The present invention relates to a preparation method of triacetaldehyde, using ionic liquid 1-ethyl-3-butylsulfonic acid imidazole p-toluenesulfonate as a catalyst, no other solvent is required during the reaction process, cost is saved, and it is more environmentally friendly. In addition, the method of the present invention not only greatly improves the conversion rate of acetaldehyde, but also has good reaction selectivity, improves the utilization rate of raw materials, and has more atomic economy. Furthermore, the post-processing of the present invention is simple, and the product can be separated by a simple vacuum distillation operation, and the ionic liquid catalyst can be reused, which is more environmentally friendly.

Description

Technical Field

[0001] The invention relates to the field of organic synthesis, and in particular to a method for preparing paraldehyde. Background Art

[0002] Triacetaldehyde is also known as secondary (acetyl) aldehyde, triacetaldehyde, and secondary aldehyde. Its molecular formula is C6H 12 O3, colorless oily liquid, with aromatic smell; its melting point is 12.6℃, boiling point is 128℃, relative density is 0.994 (20 / 4℃), it is insoluble in water, but miscible in most organic solvents; in the presence of a small amount of acid, it can be decomposed into acetaldehyde again, which can be used as a stable form of acetaldehyde, facilitating the storage and transportation of acetaldehyde. It is used as a solvent, organic synthesis, rubber accelerator and antioxidant. It is used in the fields of pesticides, fragrance, medicine and coatings.

[0003] The current method for preparing triacetaldehyde is usually to use acetaldehyde as a raw material and to generate triacetaldehyde by polymerization under acidic conditions. CN102250054A discloses the preparation of triacetaldehyde using acetaldehyde as a raw material and a strong acidic cationic resin with a sulfonic acid group on a styrene-divinylbenzene copolymer as a catalyst, and the acetaldehyde conversion rate can reach more than 90%. CN105367542A discloses that ethanol is first subjected to a dehydrogenation reaction to obtain acetaldehyde, and then calcium chloride is used as a catalyst to obtain triacetaldehyde. The patent does not report the specific reaction yield. CN 113173907 A discloses the preparation of triacetaldehyde by a fixed bed reactor in the presence of acetaldehyde, a solvent and a catalyst, wherein the solvent is selected from methanol and ethanol, and the catalyst is selected from a strong acidic cationic resin or a solid acid. The patent claims that the conversion rate of acetaldehyde and the selectivity of triacetaldehyde are both more than 99%. JP2002145877A discloses the preparation of trimeraldehyde using acetaldehyde as a raw material and ZrOCl2 as a catalyst, wherein the acetaldehyde conversion rate is 76%.

[0004] Liu Ruijiang et al. (Journal of Nanjing University of Technology, 2004, 26(6), 29) studied the reaction law of acetaldehyde to trimeraldehyde, and investigated the effect of different acids (hydrochloric acid, sulfuric acid, formic acid, oxalic acid, ferric chloride, palladium chloride) on the polymerization of acetaldehyde. Zuolin Zhu et al. (Synthesis, 1998, (4), 417) disclosed that MTO was used as a catalyst to prepare trimeraldehyde from acetaldehyde, and the conversion rate could reach 80-99%.

[0005] CN101544628A discloses a method for preparing acetal compounds by catalysis of room temperature ionic liquids, wherein the ionic liquids used are imidazolyl and pyridyl functionalized ionic liquids. However, the conversion rate of the method is not high. When acetic acid aqueous solution is used as the raw material, the content of triacetaldehyde is only 14% after 4 hours of reaction.

[0006] Yu Xinyu et al. (Chinese Journal of Chemistry, 2006, 24, 1066) reported a method for preparing trimerized aldehydes by polymerization of aldehyde compounds catalyzed by ionic liquids. They investigated the effects of different ionic liquids on the reaction and found that [Et3NH]Cl / FeCl3 had the best effect, with a selectivity of 100% and a conversion rate of 90.2%.

[0007] In summary, in the method for preparing triacetaldehyde at present, mostly acid (such as inorganic acid, organic acid, Lewis acid, heteropoly acid, acidic cationic resin, etc.) is used as catalyst. When using these acids as catalyst, there are problems such as product is difficult to separate, conversion rate is not high, in addition catalyst is difficult to recycle, production cost increases greatly, is unfavorable for industrialized production. CN101544628A discloses using ionic liquid as catalyst, but its reaction conversion rate is low, causes waste of raw materials, and is difficult to industrialize. Yu Xinyu etc. can improve the conversion rate of reaction to a certain extent by using FeCl3 to coordinate ionic liquid as catalyst, but its conversion rate is only 90.2%, and still has a large amount of raw material reaction incomplete. Therefore, it is urgent to provide a kind of green and environmentally friendly preparation method of triacetaldehyde suitable for industrialized production. Summary of the invention

[0008] In order to solve the above technical problems existing in the prior art, the present invention provides a method for preparing paraldehyde. The method of the present invention has mild reaction conditions, the catalyst can be reused, conforms to the concept of green chemistry, is more environmentally friendly, and the raw material conversion rate and selectivity are greatly improved.

[0009] The present invention provides a method for preparing paraldehyde, which is characterized by comprising the following steps:

[0010] Acetaldehyde is used as a raw material, and a polymerization reaction is carried out under the catalysis of an ionic liquid to prepare trimeraldehyde; the ionic liquid is 1-ethyl-3-butyl sulfonic acid imidazolium p-toluenesulfonate.

[0011] Preferably, the polymerization temperature is 0-60°C, more preferably 20-40°C, most preferably room temperature.

[0012] Preferably, the polymerization reaction time is 0.4-4 hours, more preferably 0.5-2 hours, most preferably 0.5-1 hour.

[0013] Preferably, the mass ratio of the ionic liquid to acetaldehyde is 1:(5-100), more preferably 1:(10-20).

[0014] Preferably, the preparation method of paraldehyde comprises the following steps:

[0015] Add acetaldehyde and ionic liquid into the reactor, stir and react at room temperature for 0.5-1 hour. After the reaction is completed, recover acetaldehyde by vacuum distillation and collect the product trimeraldehyde. The residue is the ionic liquid, which can be recycled.

[0016] When acetaldehyde is used as a raw material and a polymerization reaction is carried out under acidic conditions, the products generated include trimeraldehyde, tetrameraldehyde, etc. When the activity of the catalyst is low, the conversion rate of acetaldehyde may be low, the utilization rate of the raw material is reduced, and ultimately the yield is reduced; when the activity of the catalyst is high, acetaldehyde may be over-polymerized, and a large amount of tetrameraldehyde by-product may be generated, which reduces the purity of the product and affects the yield of the product.

[0017] Based on the existing literature reports, the inventors have conducted extensive research and investigation on a variety of ionic liquids, and finally selected the ionic liquid catalyst 1-ethyl-3-butylsulfonic acid imidazolium p-toluenesulfonate of the present invention. The ionic liquid catalyst has high catalytic activity, can improve the conversion rate of acetaldehyde, and has high selectivity, which can greatly reduce the content of by-products. Compared with [Et3NH]Cl / FeCl3 reported by Yu Xinyu et al., the conversion rate of the method of the present invention is above 95.0%, which is greatly improved, and an unexpected technical effect has been achieved.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The method of the present invention uses ionic liquid as a catalyst, and no other solvent is required during the reaction process, which saves costs and is more environmentally friendly. In addition, the method of the present invention uses a specific ionic liquid as a catalyst, which not only greatly improves the conversion rate of acetaldehyde, but also has good reaction selectivity, improves the utilization rate of raw materials, and has more atom economy. Furthermore, the post-processing of the present invention is simple. Since the boiling point of the raw material acetaldehyde is low, the boiling point of the product trimeraldehyde is only 128°C, and the product can be separated by a simple vacuum distillation operation. The ionic liquid catalyst can be reused, which is more environmentally friendly. DETAILED DESCRIPTION

[0020] The following examples are provided to illustrate the present invention in detail. The following examples are provided to better illustrate the present invention and are not intended to limit the scope of the present invention. The materials, reagents, etc. used in the following examples, unless otherwise specified, can be obtained from commercial sources.

[0021] Therefore, before describing the present invention in detail, it should be understood that the present invention is not limited to the system or process parameters of the specific examples which may vary of course. It should also be understood that the terms used herein are only for the purpose of describing a specific embodiment of the present invention, and are not intended to limit the scope of the present invention in any way. The examples used anywhere in this specification (including the examples of any terms discussed herein) are merely illustrative and in no way limit the scope and meaning of the present invention or any illustrative terms. Similarly, the present invention is not limited to the various embodiments given in this specification. Unless otherwise defined, all technical and scientific terms used herein have the same meanings as those of ordinary skill in the art to which the present invention belongs. In the event of a conflict, this document (including definitions) shall prevail.

[0022] Example 1

[0023] In a stainless steel reactor, 44.0 g of acetaldehyde and 3.5 g of 1-ethyl-3-butanesulfonic acid imidazolium p-toluenesulfonate ionic liquid were added, and the mixture was stirred at room temperature for 0.5 h.

[0024] Then, the reaction liquid was subjected to reduced pressure distillation to recover the unreacted acetaldehyde and collect the product triacetaldehyde; the residue was 1-ethyl-3-butylsulfonic acid imidazolium p-toluenesulfonate ionic liquid, which could be further recycled to obtain 41.8 g of triacetaldehyde, with a yield of 95.0% and a purity of 99.5% according to GC analysis.

[0025] Example 2

[0026] In a stainless steel reactor, 44.0 g of acetaldehyde and 3.5 g of 1-ethyl-3-butanesulfonic acid imidazolium p-toluenesulfonate ionic liquid were added, and the mixture was stirred at room temperature for 1 h.

[0027] Then, the reaction liquid was subjected to reduced pressure distillation to recover the unreacted acetaldehyde and collect the product triacetaldehyde; the residue was 1-ethyl-3-butyl sulfonic acid imidazolium p-toluenesulfonate ionic liquid, which could be further recycled to obtain 41.6 g of triacetaldehyde, with a yield of 94.5% and a purity of 99.2% according to GC analysis.

[0028] Example 3

[0029] In a stainless steel reactor, 440 g of acetaldehyde and 50 g of 1-ethyl-3-butyl imidazolium p-toluenesulfonate ionic liquid were added, and the mixture was stirred at room temperature for 0.5 h.

[0030] Then, the reaction liquid was subjected to reduced pressure distillation to recover the unreacted acetaldehyde and collect the product triacetaldehyde; the residue was 1-ethyl-3-butylsulfonic acid imidazolium p-toluenesulfonate ionic liquid, which could be further recycled to obtain 421 g of triacetaldehyde with a yield of 95.7% and a purity of 99.5% according to GC analysis.

[0031] Example 4

[0032] In a stainless steel reactor, add 220 g of acetaldehyde and 15 g of 1-ethyl-3-butyl imidazolium p-toluenesulfonate ionic liquid, and stir at room temperature for 1 h.

[0033] Then, the reaction liquid was subjected to reduced pressure distillation to recover the unreacted acetaldehyde and collect the product triacetaldehyde; the residue was 1-ethyl-3-butylsulfonic acid imidazolium p-toluenesulfonate ionic liquid, which could be further recycled to obtain 211 g of triacetaldehyde with a yield of 95.9% and a purity of 99.5% according to GC analysis.

[0034] Example 5

[0035] In a stainless steel reactor, 44.0 g of acetaldehyde and 3.5 g of 1-ethyl-3-butanesulfonic acid imidazolium p-toluenesulfonate ionic liquid were added, and the mixture was stirred at room temperature for 0.5 h.

[0036] After the reaction was completed, n-hexane (50 mL) was added to the reactor and stirred evenly. The solvent phase was decanted and analyzed by GC-MS. The results showed that the conversion rate of acetaldehyde was 96.1%.

[0037] Example 6

[0038] In a stainless steel reactor, 44.0 g of acetaldehyde and 3.5 g of 1-ethyl-3-butanesulfonic acid imidazolium p-toluenesulfonate ionic liquid were added, and the mixture was stirred at room temperature for 1 h.

[0039] After the reaction was completed, n-hexane (50 mL) was added to the reactor and stirred evenly. The solvent phase was decanted and analyzed by GC-MS. The results showed that the conversion rate of acetaldehyde was 95.7%.

Claims

1. A method for preparing paraldehyde, characterized in that: The steps include: Acetaldehyde is used as a raw material, and a polymerization reaction is carried out under the catalysis of an ionic liquid to prepare trimeraldehyde; the ionic liquid is 1-ethyl-3-butyl sulfonic acid imidazolium p-toluenesulfonate, the reaction temperature of the polymerization reaction is room temperature, the polymerization reaction time is 0.5-1 hour, and the mass ratio of the ionic liquid to acetaldehyde is 1:(10-20).

2. The preparation method according to claim 1, characterized in that: The method comprises the following steps: adding acetaldehyde and ionic liquid into a reaction kettle, stirring at room temperature for reaction for 0.5-1 hour, and after the reaction is finished, recovering acetaldehyde and collecting product trimeraldehyde by reduced pressure distillation, and the remainder is the ionic liquid, which can be recycled.