A process for the preparation of 2,2,4,4-tetramethyl-1,3-cyclobutanedione

Abstract

The present application relates to a kind of 2,2,4,4-tetramethyl-1,3-cyclobutanedione preparation method.The present application first mixes isobutyric anhydride, small molecule alcohol and organic acid and carries out high-temperature cracking, so that isobutyric anhydride in it is cracked to generate isobutyric acid and dimethyl ethylene ketone, and the isobutyric acid generated simultaneously is esterified with small molecule alcohol under the action of organic acid to generate isobutyrate;The product after cracking is separated, and dimethyl ethylene ketone is absorbed using the isobutyrate obtained by separation, and dimerization is obtained 2,2,4,4-tetramethyl-1,3-cyclobutanedione.The present application can obtain higher yield under the same operating load, reduce the generation of carbon deposition and the corrosion to equipment in the reaction process, long running cycle, and low equipment investment.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of production of cyclobutanedione compounds, in particular to a preparation method of 2,2,4,4-tetramethyl-1,3-cyclobutanedione. BACKGROUND

[0002] Enone compounds (RR' = C = O) are important intermediates in organic synthesis. Due to the high unsaturation of the functional group, addition, decomposition and polymerization reactions can occur, and they are important intermediates for a variety of fine chemicals. 2,2,4,4-tetramethyl-1,3-cyclobutanedione (TMCB) is a product of dimethyl enone dimerization, mainly used to synthesize 2,2,4,4-tetramethyl-1,3-cyclobutanediol (CBDO). The existing TMCB industrial synthesis method is to produce dimethyl enone by high-temperature cracking of isobutyric acid or isobutyric anhydride, and dimethyl enone is obtained by solvent absorption and dimerization.

[0003] At present, this technology is mastered by Eastman. US2936324A, US5169994A and US5258556A disclose a method for preparing DMK by thermal cracking of isobutyric anhydride (ANIB) as raw material without adding catalyst, by controlling the thermal cracking reaction temperature to be 350-600℃, the absolute pressure to be 3.0-70kPa, and the residence time to be 0.05-10s, so that the conversion rate of ANIB can reach more than 80%, and the yield of DMK per pass can reach about 40%. Similar to Eastman Chemical Company, Arkema also discloses a method for preparing DMK by thermal cracking of isobutyric anhydride (ANIB) as raw material in patent documents US7435856B2 and CN100439311C. China Petroleum and Natural Gas Corporation Limited reports a similar method for preparing DMK by thermal cracking in patent application CN105732354A. This patent application considers using isobutyric acid as a thermal cracking raw material, because the cracking reaction activity of isobutyric acid is much lower than that of isobutyric anhydride, the thermal cracking temperature will be higher. Under the condition that the volume ratio of isobutyric acid raw material to inert gas is 1 / 10-1 / 5, the DMK is obtained by cracking reaction through a fixed bed cracking reactor, and then the DMK obtained after cracking is directly polymerized in solution in the same polymerization kettle to prepare 2,2,4,4-tetramethyl-1,3-cyclobutanedione. The innovation of this patent application is to directly dimerize the product after cracking, which reduces the equipment investment, eliminates the washing tower or absorption tower, and avoids the large consumption of absorption liquid and energy loss. However, in the thermal cracking process of isobutyric acid and isobutyric anhydride, the related conversion rate and yield indicators are low, which limits the popularization and application of the technology.

[0004] The current industry has more research on cracking and dimerization, and continuously develops new cracking processes and innovates existing processes. However, due to the high activity of enone compounds, when dimethyl enone cannot be effectively separated and absorbed, the reverse reaction of dimethyl enone and isobutyric acid to generate isobutyric anhydride will reduce the conversion rate, greatly reducing the economic efficiency of the process. Therefore, it is urgent to develop a new process to solve the problems of by-products, carbon deposition, low single-pass yield of enone compounds and more side reactions caused by further cracking of enone compounds. SUMMARY

[0005] In view of the deficiencies in the prior art, the purpose of the present application is to provide a preparation method of 2,2,4,4-tetramethyl-1,3-cyclobutanedione. The process simultaneously introduces small molecule alcohols and organic acids during the cracking process. The small molecule alcohols react with the isobutyric acid generated during cracking to form the corresponding ester, which facilitates the forward movement of the reaction, reduces the possibility of reverse reaction of isobutyric acid and dimethyl enone, and improves the conversion rate of the reaction. The generated ester product can well dissolve dimethyl enone, prevent the formation of carbon deposition by dimethyl enone, improve the stability of the entire device operation, and greatly improve the economic efficiency of the process operation.

[0006] To achieve the above-mentioned purposes, the technical solutions of the present application are as follows:

[0007] The present application provides a preparation method of 2,2,4,4-tetramethyl-1,3-cyclobutanedione, comprising the following steps:

[0008] 1) Mix isobutyric anhydride, small molecule alcohol and organic acid, and then perform high-temperature cracking reaction to crack the isobutyric anhydride to generate isobutyric acid and dimethyl enone, and the generated isobutyric acid is esterified with the small molecule alcohol to generate isobutyric ester under the action of the organic acid;

[0009] 2) The reaction liquid of step 1) is separated by condensation to obtain a gas phase containing dimethyl enone and a liquid phase containing isobutyric ester, wherein the liquid phase is separated by distillation to obtain isobutyric ester, and unreacted isobutyric anhydride, small molecule alcohol and isobutyric acid;

[0010] 3) The gas phase containing dimethyl enone of step 2) is introduced into the isobutyric ester separated in step 2) to adsorb dimethyl enone, and an isobutyric ester solution of dimethyl enone is obtained;

[0011] 4) The isobutyric ester solution of dimethyl enone of step 3) is subjected to polymerization reaction to obtain 2,2,4,4-tetramethyl-1,3-cyclobutanedione.

[0012] In the present application, the small molecule alcohol of step 1) is selected from C1-C6 alcohols, preferably C3-C5 monohydric alcohol or polyhydric alcohol, more preferably dihydric alcohol;

[0013] The small molecule alcohol is selected from any one or a combination of at least two of propanol, isobutyl alcohol, ethylene glycol, neopentyl glycol, and 1,2-propanediol, and is preferably neopentyl glycol.

[0014] In the present application, the organic acid in step 1) is selected from any one or a combination of at least two of sulfonic acid compounds, preferably benzene sulfonic acid, p-toluene sulfonic acid, methanesulfonic acid, ethanesulfonic acid, and propanesulfonic acid, and is more preferably p-toluene sulfonic acid.

[0015] In the present application, the mixing mass ratio of the isobutyric anhydride and the small molecule alcohol in step 1) is 1.6-4:1, such as 1.8:1, 2.5:1, 3.5:1, and is preferably 2-3:1.

[0016] The amount of the organic acid is 0.03-0.06% of the mass of the small molecule alcohol, such as 0.035%, 0.045%, and is preferably 0.04-0.055%.

[0017] In the present application, the isobutyric anhydride, the small molecule alcohol, and the organic acid in step 1) are first preheated after mixing, and the preheating temperature is 280-460°C, such as 300°C, 340°C, 400°C, and is preferably 310-370°C.

[0018] In the present application, the high-temperature pyrolysis reaction in step 1) is carried out at a reaction temperature of 400-650°C, such as 450°C, 480°C, 550°C, 600°C, and is preferably 420-500°C, a reaction pressure of 5-65 kpaA, such as 15 kpaA, 20 kpaA, 35 kpaA, 50 kpaA, and is preferably 10-25 kpaA, and a residence time of 0.01 s-0.7 s, such as 0.05 s, 0.3 s, 0.6 s, and is preferably 0.1 s-0.5 s. The high-temperature pyrolysis reaction simultaneously includes both pyrolysis and esterification processes, and the two reactions are carried out simultaneously and under the same reaction conditions. On the one hand, the isobutyric anhydride is pyrolyzed to generate isobutyric acid and dimethyl ethylene ketone, and the organic acid can promote the pyrolysis of isobutyric acid and improve the pyrolysis conversion rate. On the other hand, it is ensured that isobutyric acid is generated and esterified with the small molecule alcohol under the action of the organic acid to generate isobutyric ester.

[0019] In the present application, the high-temperature cracking reaction of step 1) is carried out in an inert gas environment, and the inert gas is selected from one of nitrogen, argon, CO2, methane, ethane, and propane; the inert gas is preheated before the reaction, and the preheating temperature is 280-460°C, for example, 300°C, 340°C, 400°C, preferably 310-370°C; the inert gas is used as a carrier gas and is fed simultaneously with isobutyric anhydride, a small-molecule alcohol, and an organic acid mixture; and the feeding flow rate of the raw material mixture and the inert gas is not particularly limited. The inert gas is used to dilute and control the residence time and pressure during the reaction, and the feeding amount of the raw material mixture and the inert gas is not particularly limited, and the residence time of the raw material mixture can be balanced by the inert gas within the required range.

[0020] In the present application, the condensation of step 2) is carried out at a temperature of 10-40°C, for example, 20°C, 30°C, preferably 15-25°C, for a time of 0.2-2h, for example, 0.4h, 0.8h, 1.5h, preferably 0.5-1h.

[0021] In the present application, the gas phase containing dimethyl vinyl ketone obtained by condensation in step 2) contains dimethyl vinyl ketone in an amount of 95wt% or more, preferably 95-99wt%, and the remaining amount is a small amount of isobutene, acetone, pentene, hexene, and heavy components and other impurities.

[0022] In the present application, the distillation of step 2) is a conventional operation in the art, and in some specific examples, the specific conditions preferably adopted are as follows: a temperature of 60-180°C, for example, 80°C, 100°C, 130°C, preferably 70-150°C; and a pressure of 15-50kPaA, for example, 18kpaA, 25kpaA, 35kpaA, 45kpaA, preferably 20-40kPaA.

[0023] In the present application, the isobutyric ester obtained by distillation in step 2) has a purity of >98.5wt%, and may also contain a small amount of isobutyric anhydride, organic acid, and other impurities.

[0024] The unreacted isobutyric anhydride, small-molecule alcohol, and isobutyric acid can be recycled and used as raw materials for the high-temperature cracking reaction of step 1) again.

[0025] In the present application, the adsorption of step 3) is carried out at a temperature of 40-120°C, for example, 60°C, 70°C, 100°C, preferably 50-80°C, for a time of 0.2-2h, for example, 0.4h, 0.8h, 1.5h, preferably 0.5-1h; and at a pressure of 10-25kPaA, for example, 13kpaA, 18kpaA, 23kpaA, preferably 15-20kPaA.

[0026] In the present application, the concentration of the isobutyric acid ester solution of dimethyl ethylene ketone obtained in step 3) is 5-20 wt%, preferably 10-15 wt%.

[0027] In the present application, the polymerization reaction in step 4) is carried out at a temperature of 80-160°C, for example 90°C, 11°C, 120°C, 140°C, preferably 100-130°C, for a time of 30-180 min, for example 50 min, 80 min, 100 min, 140 min, preferably 60-120 min, and at normal pressure.

[0028] In the preparation method of the present application, the conversion rate of isobutyric anhydride can be as high as 90% or more, and the selectivity of dimethyl ethylene ketone can be as high as 95%. After 1000 h of cumulative operation, there is no carbon powder deposition on the inner wall of the reactor.

[0029] In the polymerization reaction, the conversion rate of dimethyl ethylene ketone can be as high as 98% or more, and the selectivity of 2,2,4,4-tetramethyl-1,3-cyclobutanedione can be as high as 98.5% or more.

[0030] Compared with the prior art, the technical scheme of the present application has the following beneficial effects:

[0031] 1) Small molecule alcohols and organic acids are added to the raw materials. During the cracking reaction, isobutyric anhydride is cracked to produce isobutyric acid and dimethyl ethylene ketone. Under the action of the organic acid, isobutyric acid is esterified with the small molecule alcohol to form the corresponding ester. The consumption of isobutyric acid can effectively reduce the reverse reaction of isobutyric acid and dimethyl ethylene ketone, thereby improving the conversion rate of isobutyric anhydride cracking.

[0032] 2) The ester produced in the reaction can effectively dissolve dimethyl ethylene ketone, thereby inhibiting the further reaction of dimethyl ethylene ketone to produce carbon deposition. The use of this process can effectively prolong the operation time of the cracking reaction and improve the economy of the product.

[0033] 3) The ester produced in the esterification reaction is well dissolved in dimethyl ethylene ketone, and no additional solvent is needed for the dimerization of dimethyl ethylene ketone to form 2,2,4,4-tetramethyl-1,3-cyclobutanedione. Since the solvent is produced during the reaction, there is no problem of low efficiency of cooling and absorbing dimethyl ethylene ketone. DETAILED DESCRIPTION

[0034] The following examples will further illustrate the method provided by the present application, but the present application is not limited to the listed examples, and any other known changes within the scope of the claims of the present application should also be included.

[0035] Chromatographic analysis conditions: DB-5MS (30 m x 0.25 mm x 0.25 μm) column was used for analysis, and the specific operation conditions were as follows: 50℃ was kept for 2 min, increased to 100℃ at 5℃ / min, kept for 5 min, increased to 260℃ at 15℃ / min, kept for 5 min. The temperature of the sample injector was 240℃, and the temperature of the detector was 260℃.

[0036] The main raw material source information used in the embodiments of the present application is as follows, and other ordinary commercially available raw materials are used unless otherwise specified.

[0037] Isobutyric anhydride: Beijing Ino Kai Technology Co., Ltd., product purity > 98%;

[0038] Isobutyl alcohol: Araldin, product purity > 99%;

[0039] Neopentyl glycol: Beijing Ino Kai Technology Co., Ltd., product purity > 99%;

[0040] Trimethylolpropane: Beijing Ino Kai Technology Co., Ltd., product purity > 99%;

[0041] Pentaerythritol: Beijing Ino Kai Technology Co., Ltd., product purity > 99%;

[0042] p-Toluene sulfonic acid: Beijing Ino Kai Technology Co., Ltd., product purity > 99%;

[0043] Methanesulfonic acid: Beijing Ino Kai Technology Co., Ltd., product purity > 99%.

[0044] Example 1

[0045] The preparation of 2,2,4,4-tetramethyl-1,3-cyclobutanedione is as follows:

[0046] 1) Isobutyric anhydride, isobutyl alcohol, and p-toluene sulfonic acid were mixed to prepare a raw material solution, wherein the mass ratio of isobutyric anhydride to isobutyl alcohol was 4:1, and the mass of p-toluene sulfonic acid was 0.06% of isobutyl alcohol. The raw material solution was fed by a feeding pump at a feeding speed of 15 g / min, and nitrogen was fed at a feeding speed of 1500 ml / min. After mixing in a mixer, the mixture was preheated, and the preheating temperature was 280℃. The preheated mixture passed through a cracking reaction device (cracking reactor length 15 m) at a cracking temperature of 400℃, and the pressure during the reaction process was 5 KPaA, and the residence time was 0.7 s. Isobutyric anhydride in the mixture was cracked to generate isobutyric acid and dimethyl ethylene ketone, and isobutyl alcohol was esterified with isobutyric acid generated under the action of toluenesulfonic acid to generate isobutyl isobutyrate. The reaction liquid was sampled for gas chromatographic analysis.

[0047] 2) The reaction solution after reaction is rapidly passed through a condenser, the cooling temperature is controlled at 10°C, the gas-liquid mixture after cooling is separated in a separation tank, the cooling and separation time is 0.5h, the gas phase containing dimethyl vinyl ketone and the liquid phase containing isobutyl isobutyrate are obtained. In the gas phase containing dimethyl vinyl ketone, the dimethyl vinyl ketone content is 99wt%, the rest is a small amount of acetone and isobutene;

[0048] The liquid phase containing isobutyl isobutyrate is subjected to distillation operation, the distillation temperature is 105°C, the pressure is 20kPaA, isobutyl isobutyrate is separated from the top of the column, the purity is 99wt%, the rest is a small amount of isobutanol and isobutyric acid, the unreacted isobutyric anhydride, isobutyric acid and p-toluenesulfonic acid obtained from the bottom of the column can be continuously separated and recycled for use.

[0049] 3) The gas phase containing dimethyl vinyl ketone in step 2) is passed into the isobutyl isobutyrate separated from the top of the column in step 2), the isobutyl isobutyrate generated by reaction is used to adsorb dimethyl vinyl ketone, the adsorption temperature is 40°C, the time is 2h, the pressure is 10kPaA, the isobutyl isobutyrate solution of dimethyl vinyl ketone is obtained, the concentration is 12wt%;

[0050] 4) The isobutyl isobutyrate solution of dimethyl vinyl ketone in step 3) is put into a polymerization kettle for polymerization reaction, the reaction temperature is controlled at 80°C, the polymerization time is 180min, the reaction is carried out under normal pressure, 2,2,4,4-tetramethyl-1,3-cyclobutanedione is obtained, the reaction solution is sampled for gas chromatography analysis.

[0051] The gas chromatography analysis results: in the cracking reaction of step 1), the isobutyric anhydride conversion rate is 93.3%, the dimethyl vinyl ketone selectivity is 95.2%, the carbon deposition side reaction selectivity is <0.5%. After 1000h of cumulative operation, in the cracking reaction of step 1), the isobutyric anhydride conversion rate is 92.4%, the dimethyl vinyl ketone selectivity is 94.1%, and there is no carbon powder deposition on the inner wall of the reactor.

[0052] In the polymerization reaction of step 4), the dimethyl vinyl ketone conversion rate is 99.2%, the 2,2,4,4-tetramethyl-1,3-cyclobutanedione selectivity is 98.8%.

[0053] Example 2

[0054] 2,2,4,4-tetramethyl-1,3-cyclobutanedione is prepared, the steps are as follows:

[0055] 1) isobutyric anhydride, ethylene glycol, p-toluene sulfonic acid are mixed to form a raw material solution, the mass ratio of isobutyric anhydride to ethylene glycol is 2.04:1, the mass of p-toluene sulfonic acid is 0.051% of ethylene glycol, the feeding speed of the raw material solution is 28g / min, the feeding speed of nitrogen is 1500ml / min, the preheating temperature of the mixture in the mixer is 320℃, the cracking reaction device (the length of the cracking reactor is 15m), the cracking temperature is 460℃, the pressure of the reaction process is 15KPaA, the residence time is 0.5s, the isobutyric anhydride in the raw material solution is cracked to generate isobutyric acid and dimethyl ethylene ketone, the generated isobutyric acid is esterified with ethylene glycol to generate ethylene glycol diisobutyrate under the action of p-toluene sulfonic acid, and the reaction solution is sampled for gas chromatography analysis;

[0056] 2) the reaction solution after the reaction is rapidly passed through a condenser, the cooling temperature is controlled to be 20℃, the gas-liquid mixture after cooling is separated in a separation tank, the cooling and separation time is 1h, and the gas phase containing dimethyl ethylene ketone and the liquid phase containing ethylene glycol diisobutyrate are obtained. In the gas phase containing dimethyl ethylene ketone, the content of dimethyl ethylene ketone is 96wt%, and the rest is a small amount of acetone and isobutene;

[0057] The liquid phase containing ethylene glycol diisobutyrate is subjected to distillation operation, the distillation temperature is 145℃, the pressure is 15kPaA, the unreacted isobutyric anhydride, isobutyric acid and ethylene glycol are separated from the top of the column and can be continuously separated and recycled, and the ethylene glycol diisobutyrate is obtained from the column bottom, the purity is 98.5wt%, and the rest is a small amount of p-toluene sulfonic acid and isobutyric acid.

[0058] 3) the gas phase containing dimethyl ethylene ketone in step 2) is introduced into the ethylene glycol diisobutyrate separated from the column bottom in step 2), the ethylene glycol diisobutyrate generated by the reaction is used to adsorb dimethyl ethylene ketone, the adsorption temperature is 50℃, the time is 1.5h, the pressure is 15kPaA, and the ethylene glycol diisobutyrate solution of dimethyl ethylene ketone is obtained, and the concentration is 15wt%;

[0059] 4) the ethylene glycol diisobutyrate solution of dimethyl ethylene ketone in step 3) is introduced into a polymerization kettle to perform polymerization reaction, the reaction temperature is controlled to be 120℃, the polymerization time is 60min, the reaction is performed under normal pressure, and 2,2,4,4-tetramethyl-1,3-cyclobutanedione is obtained, and the reaction solution is sampled for gas chromatography analysis.

[0060] The gas chromatography analysis results show that in the cracking reaction of step 1), the conversion rate of isobutyric anhydride is 91.8%, the selectivity of dimethyl ethylene ketone is 96.4%, and the selectivity of carbon deposition side reaction is less than 0.5%. After 1000h of cumulative operation, in the cracking reaction of step 1), the conversion rate of isobutyric anhydride is 90.7%, the selectivity of dimethyl ethylene ketone is 95.1%, and no carbon powder is deposited on the inner wall of the reactor.

[0061] The conversion rate of dimethyl vinyl ketone in the polymerization reaction of Step 4) is 98.8%, and the selectivity of 2,2,4,4-tetramethyl-1,3-cyclobutanedione is 99.1%.

[0062] Example 3

[0063] The preparation of 2,2,4,4-tetramethyl-1,3-cyclobutanedione is as follows:

[0064] 1) The isobutyric anhydride, neopentyl glycol and methanesulfonic acid are mixed to form a raw material solution, wherein the mass ratio of isobutyric anhydride to neopentyl glycol is 2.67:1, and the mass of methanesulfonic acid is 0.053% of neopentyl glycol. The solution is fed into a feeding pump at a feeding speed of 30 g / min, and nitrogen is fed into the feeding pump at a feeding speed of 7500 ml / min. The mixture is preheated after mixing in a mixer, and the preheating temperature is 350°C. The mixture is fed into a cracking reaction device (the length of the cracking reactor is 15 m) at a cracking temperature of 520°C, and the pressure during the reaction process is 35 KPaA. The residence time is 0.1 s. The isobutyric anhydride in the mixture is cracked to generate isobutyric acid and dimethyl vinyl ketone, and the generated isobutyric acid is esterified with neopentyl glycol to generate isobutyric acid neopentyl glycol ester under the action of methanesulfonic acid. The reaction solution is sampled for gas chromatography analysis.

[0065] 2) The reaction solution after the reaction is rapidly passed through a condenser, and the cooling temperature is controlled at 30°C. The gas-liquid mixture after cooling is separated in a separation tank, and the cooling and separation time is 1.5 h. A gas phase containing dimethyl vinyl ketone and a liquid phase containing isobutyric acid neopentyl glycol ester are obtained. In the gas phase containing dimethyl vinyl ketone, the content of dimethyl vinyl ketone is 99 wt%, and the rest is a small amount of acetone and isobutene.

[0066] The liquid phase containing isobutyric acid neopentyl glycol ester is subjected to distillation operation, and the distillation temperature is 155°C and the pressure is 15 kPaA. Unreacted isobutyric anhydride, isobutyric acid and neopentyl glycol are separated from the top of the column and can be continuously separated and recycled for use. Isobutyric acid neopentyl glycol ester is obtained from the column bottom, and the purity is 98.8 wt%, and the rest is a small amount of methanesulfonic acid and isobutyric acid.

[0067] 3) The gas phase containing dimethyl vinyl ketone in Step 2) is introduced into the isobutyric acid neopentyl glycol ester separated from the column bottom in Step 2). The isobutyric acid neopentyl glycol ester generated by the reaction is used to adsorb dimethyl vinyl ketone. The adsorption temperature is 60°C, the time is 0.7 h, and the pressure is 20 kPaA. The isobutyric acid neopentyl glycol ester solution of dimethyl vinyl ketone is obtained, and the concentration is 17 wt%.

[0068] 4) The dimethyl vinyl ketone isobutyric acid neopentyl glycol ester solution in Step 3) is introduced into a polymerization kettle for polymerization reaction. The reaction temperature is controlled at 120°C, the polymerization time is 120 min, and the reaction is carried out at normal pressure. 2,2,4,4-tetramethyl-1,3-cyclobutanedione is obtained, and the reaction solution is sampled for gas chromatography analysis.

[0069] Gas chromatography analysis results: in the cracking reaction of step 1), the conversion rate of isobutyric anhydride was 94.2%, the selectivity of dimethyl vinyl ketone was 95.7%, and the selectivity of carbon deposition side reaction was <0.5%. After 1000h of cumulative operation, in the cracking reaction of step 1), the conversion rate of isobutyric anhydride was 92.8%, the selectivity of dimethyl vinyl ketone was 94.2%, and there was no carbon powder deposition on the inner wall of the reactor.

[0070] In the polymerization reaction of step 4), the conversion rate of dimethyl vinyl ketone was 99.0%, and the selectivity of 2,2,4,4-tetramethyl-1,3-cyclobutanedione was 99.0%.

[0071] Example 4

[0072] The preparation of 2,2,4,4-tetramethyl-1,3-cyclobutanedione is as follows:

[0073] 1) isobutyric anhydride, neopentyl glycol, and ethanesulfonic acid were mixed to prepare a raw material solution, in which the mass ratio of isobutyric anhydride to neopentyl glycol was 1.67:1, and the mass of ethanesulfonic acid was 0.033% of neopentyl glycol. The solution was fed into a cracking reaction device (cracking reactor 15m long) through a feeding pump at a feeding speed of 30g / min, and nitrogen was fed at a feeding speed of 27500ml / min. The mixture was preheated after mixing in a mixer, and the preheating temperature was 440°C. The isobutyric anhydride in the mixture was cracked to generate isobutyric acid and dimethyl vinyl ketone at a cracking temperature of 600°C, and the generated isobutyric acid was esterified with neopentyl glycol to generate isobutyric acid neopentyl glycol ester under the action of ethanesulfonic acid. The reaction solution was sampled for gas chromatography analysis;

[0074] 2) The reaction solution after reaction was rapidly passed through a condenser, and the cooling temperature was controlled at 40°C. The gas-liquid mixture after cooling was separated in a separation tank, and the cooling and separation time was 2h. A gas phase containing dimethyl vinyl ketone and a liquid phase containing isobutyric acid neopentyl glycol ester were obtained. In the gas phase containing dimethyl vinyl ketone, the content of dimethyl vinyl ketone was 95wt%, and the rest was a small amount of acetone and isobutene.

[0075] The liquid phase containing isobutyric acid neopentyl glycol ester was subjected to distillation operation at a distillation temperature of 155°C and a pressure of 15kPaA. Unreacted isobutyric anhydride, isobutyric acid, and neopentyl glycol were separated from the top of the column and could be continuously separated and recycled. Isobutyric acid neopentyl glycol ester was obtained from the bottom of the column, and the purity was 98.5wt%, and the rest was a small amount of ethanesulfonic acid and isobutyric acid.

[0076] 3) The gaseous phase containing dimethyl vinyl ketone of step 2) is passed into the isobutyl acid neopentyl glycol ester separated from the bottom of the column of step 2), and the isobutyl acid neopentyl glycol ester produced in the reaction is used to adsorb the dimethyl vinyl ketone, the adsorption temperature is 70°C, the time is 0.2h, and the pressure is 25kPaA, to obtain the isobutyl acid neopentyl glycol ester solution of dimethyl vinyl ketone with a concentration of 20wt%;

[0077] 4) The isobutyl acid neopentyl glycol ester solution of dimethyl vinyl ketone of step 3) is introduced into a polymerization kettle to perform a polymerization reaction, the reaction temperature is controlled at 160°C, the polymerization time is 30min, and the reaction is performed under normal pressure, to obtain 2,2,4,4-tetramethyl-1,3-cyclobutanedione, and the reaction liquid is sampled for gas chromatography analysis.

[0078] The gas chromatography analysis results show that in the cracking reaction of step 1), the conversion rate of isobutyric anhydride is 92.2%, the selectivity of dimethyl vinyl ketone is 95.9%, and the selectivity of carbon deposition side reaction is less than 0.5%. After 1000h of cumulative operation, in the cracking reaction of step 1), the conversion rate of isobutyric anhydride is 90.9%, the selectivity of dimethyl vinyl ketone is 94.1%, and there is no carbon powder deposition on the inner wall of the reactor.

[0079] In the polymerization reaction of step 4), the conversion rate of dimethyl vinyl ketone is 98.2%, and the selectivity of 2,2,4,4-tetramethyl-1,3-cyclobutanedione is 98.9%.

[0080] Comparative Example 1

[0081] 2,2,4,4-tetramethyl-1,3-cyclobutanedione is prepared by the following steps:

[0082] 1) Isobutyric anhydride is fed by a feeding pump at a feeding rate of 25g / min, nitrogen is fed at a feeding rate of 1500ml / min, and after mixing in a mixer, they are preheated at a preheating temperature of 320°C, and then pass through a cracking reaction device (cracking reactor with a length of 15m) at a cracking temperature of 460°C, and the pressure during the reaction is 15KPa, and the residence time is 0.5s, so that isobutyric anhydride in it is cracked to generate isobutyric acid and dimethyl vinyl ketone, and the reaction liquid is sampled for gas chromatography analysis;

[0083] 2) The reaction liquid after the reaction is rapidly passed through a condenser, the cooling temperature is controlled at 20°C, and the gas-liquid mixture after cooling is separated by a separation tank, the cooling and separation time is 1h, to obtain a gaseous phase containing dimethyl vinyl ketone and a liquid phase containing unreacted isobutyric anhydride and isobutyric acid, the content of dimethyl vinyl ketone in the gaseous phase containing dimethyl vinyl ketone is 95wt%, and the rest is a small amount of acetone and isobutene;

[0084] 3) The gas phase containing dimethyl ketene in step 2) is passed into isobutyl isobutyrate, and dimethyl ketene is absorbed by isobutyl isobutyrate at an adsorption temperature of 50°C, a time of 1.5 h, and a pressure of 15 kPaA to obtain a dimethyl ketene isobutyl isobutyrate solution with a concentration of 15 wt%.

[0085] 4) The dimethyl ketene isobutyl isobutyrate solution from step 3) was introduced into a polymerization reactor for polymerization. The reaction temperature was controlled at 120℃, the polymerization time at 60 min, and the reaction was carried out at atmospheric pressure. The reaction solution was analyzed by gas chromatography to obtain 2,2,4,4-tetramethyl-1,3-cyclobutanedione. Samples of the reaction solution were taken for gas chromatography analysis.

[0086] Gas chromatography analysis results: In step 1), the conversion rate of isobutyric anhydride was 82.7%, the selectivity of dimethyl ketone was 90.2%, and the selectivity of the carbon deposition side reaction was 2.9%. After a cumulative run of 1000 h, in step 1), the conversion rate of isobutyric anhydride was 66%, the selectivity of dimethyl ketone was 81%, and the carbon deposition was 15%. The excessive carbon deposition and carbon powder deposition on the inner wall of the reactor led to a significant decrease in the internal temperature of the pyrolysis reaction, resulting in a significant decrease in reaction activity.

[0087] In the polymerization reaction of step 4), the conversion rate of dimethyl ketone was 95.4%, and the selectivity of 2,2,4,4-tetramethyl-1,3-cyclobutanedione was 96.2%.

[0088] Comparative Example 2

[0089] The preparation method is the same as in Example 2, except that p-toluenesulfonic acid is not added in step 1), and solid acidic alumina is packed in the reactor as an esterification catalyst, while other operations and conditions remain unchanged.

[0090] Gas chromatography analysis results: In the pyrolysis reaction of step 1), the conversion rate of isobutyric anhydride was 82%, the selectivity of dimethyl ketone was 93.2%, and the selectivity of the carbon deposition side reaction was 4.1%. After a cumulative run of 300 hours, carbon powder was deposited on the inner wall of the reactor. Due to the carbon deposition, the solid acidic alumina became clogged and deactivated, causing the reaction to be unable to operate normally.

[0091] In the polymerization reaction of step 4), the conversion rate of dimethyl ketone was 98.1%, and the selectivity of 2,2,4,4-tetramethyl-1,3-cyclobutanedione was 98.2%.

Claims

1. A process for the preparation of 2,2,4,4-tetramethyl-1,3-cyclobutanedione, characterized in that the steps The application relates to a method for preparing 2,2,4,4-tetramethyl-1,3-cyclobutanedione. 1) mixing isobutyric anhydride, small-molecule alcohol and organic acid, and then performing high-temperature cracking reaction to crack the isobutyric anhydride to generate isobutyric acid and dimethyl ethylene ketone, and the generated isobutyric acid is esterified with the small-molecule alcohol to generate isobutyric ester under the action of the organic acid; 2) separating the reaction liquid of step 1) through condensation to obtain gas phase containing dimethyl ethylene ketone and liquid phase containing isobutyric ester, wherein the liquid phase is separated through distillation to obtain isobutyric ester, and unreacted isobutyric anhydride, small-molecule alcohol and isobutyric acid; 3) passing the gas phase containing dimethyl ethylene ketone of step 2) into the isobutyric ester separated in step 2) to adsorb dimethyl ethylene ketone, and obtaining dimethyl ethylene ketone isobutyric ester solution; 4) performing polymerization reaction on the dimethyl ethylene ketone isobutyric ester solution of step 3) to obtain 2,2,4,4-tetramethyl-1,3-cyclobutanedione. The small-molecule alcohol of step 1) is selected from C1-C6 alcohols; the organic acid is selected from sulfonic acid compounds; and the high-temperature cracking reaction is performed in an inert gas environment.

2. The production method according to claim 1, characterized by, The small-molecule alcohol of step 1) is selected from C3-C5 monohydric alcohol or polyhydric alcohol.

3. The preparation method according to claim 2, characterized in that, The small-molecule alcohol is selected from dihydric alcohol.

4. The method of claim 1, wherein, The small-molecule alcohol of step 1) is selected from any one or combination of at least two of propyl alcohol, isobutyl alcohol, ethylene glycol, neopentyl glycol and 1,2-propanediol.

5. The preparation method according to claim 1, characterized in that, The organic acid of step 1) is selected from any one or combination of at least two of benzene sulfonic acid, p-toluene sulfonic acid, methane sulfonic acid, ethane sulfonic acid and propane sulfonic acid.

6. The method of claim 1, wherein, The mixing mass ratio of the isobutyric anhydride and the small-molecule alcohol of step 1) is 1.6-4:

1. The amount of the organic acid is 0.03-0.06% of the mass of the small-molecule alcohol.

7. The preparation method according to claim 6, characterized in that, The mixing mass ratio of the isobutyric anhydride and the small-molecule alcohol is 2-3:

1.

8. The preparation method according to claim 6, characterized in that, The amount of the organic acid is 0.04-0.055% of the mass of the small-molecule alcohol.

9. The method of claim 1, wherein, The isobutyric anhydride, the small-molecule alcohol and the organic acid of step 1) are preheated after mixing, and the preheating temperature is 280-460 DEG C.

10. The method of claim 9, wherein, The preheating temperature is 310-370 DEG C.

11. The method of claim 1, wherein, The high-temperature cracking reaction of step 1) is performed at a reaction temperature of 400-650 DEG C, a reaction pressure of 5-65 kPaA and a residence time of 0.01 s-0.7 s.

12. The method of claim 11, wherein, The high-temperature cracking reaction is performed at a reaction temperature of 420-500 DEG C, a reaction pressure of 10-25 kPaA and a residence time of 0.1 s-0.5 s.

13. The method of claim 1, wherein, The inert gas of step 1) is selected from one of nitrogen, argon, CO2, methane, ethane and propane. The inert gas is preheated before reaction, and the preheating temperature is 280-460 DEG C.

14. The method of claim 13, wherein, The preheating temperature is 310-370 DEG C.

15. The method of claim 1, wherein, The condensation of step 2) is performed at a temperature of 10-40 DEG C for 0.2-2 h.

16. The method of claim 15, wherein, The condensation is performed at a temperature of 15-25 DEG C for 0.5-1 h.

17. The method of claim 1, wherein, The adsorption of step 3) is performed at a temperature of 40-120 DEG C for 0.2-2 h and a pressure of 10-25 kPaA.

18. The method of claim 17, wherein, The adsorption is performed at a temperature of 50-80 DEG C for 0.5-1 h and a pressure of 15-20 kPaA.

19. The method of claim 1, wherein, The polymerization reaction of step 4) is performed at a temperature of 80-160 DEG C for 30-180 min and a polymerization pressure of normal pressure.

20. The method of claim 19, wherein, The polymerization reaction is carried out at a temperature of 100-130°C for 60-120 minutes.