RU2058296C1 - Method for production of citraconic anhydride - Google Patents

Abstract

FIELD: production of medicinal preparations. SUBSTANCE: methyl acetylene is used as reagent 1, oxygen being used as reagent 2. Reaction is carried out in the presence of carbon monoxide, ratio of carbon monoxide and methyl acetylene being 6-1:1. Catalytic system PdBr₂-organic solvent also being used. Ketone, or acetic acid or acetonitrile or 8-butyrolactone are used as mentioned above organic solvent. Mentioned above catalytic system contains (mol/l): H₂O 0.05-08, LiBr 0.1-0.16, water 0.45-2.2. EFFECT: improves efficiency of method. 8 tbl

Description

 The invention relates to organic synthesis.

 Citraconic anhydride (CA), a valuable multi-purpose sinton, is used to cure epoxy resins, to produce drugs, plasticizers, copolymers, layered materials with increased resistance to glass transition and whitening of lubricants, itaconic acid.

Known methods for the synthesis of citraconic anhydride from citric or itaconic acids. The selectivity of the formation of citraconic anhydride is 39-98% and 31-85%, respectively. The process is carried out at temperatures of 165-210 ^about C. There is also a known method of producing citraconic anhydride or citraconic acid from methyl succinic acid (through the stage of chlorination and dehydrochlorination). The process is carried out at 400-500 ° ^C. The maximum selectivity of citraconic anhydride and citraconic acid (CC) is 75-80% basic and essential disadvantages these methods are technologies complexity associated with high temperature synthesis, the use of expensive and scarce raw material (citric, itaconic , methyl succinic acid (MY)). For the latter method, a significant drawback is the high aggressiveness of chlorine in the chlorination stage.

 Citraconic anhydride and citraconic acid are formed in small quantities during the oxidation of o-xylene to phthalic anhydride. Several options have been proposed for the isolation of citraconic anhydride from wastewater from the production of phthalic anhydride, based on the extraction of 5-membered cyclic dicarboxylic anhydrides (citraconic, succinic, methyl succinic, itaconic) with tertiary amines.

 The disadvantages of these options are the complexity of the technology associated with the use of energy-intensive azeotropic distillation, as well as the high price and scarcity of tertiary amines.

 The main method for producing dicarboxylic acid anhydrides is the catalytic oxidation of various hydrocarbons by air in the presence of catalysts (oxides or salts of V, Mo, Bi, Mn and other metals of groups 5 and 6 of the periodic system). The yield of the target products depends on the ratio of the components of the catalyst and the method of preparation and modification of the catalyst.

The closest in technical essence and attainable effect is a process for the preparation of citraconic anhydride by oxidation of isoprene air ^at 400 ° C for catalysts containing oxides of vanadium, molybdenum, bismuth, antimony V ratios: Mo: Bi = 1: 0.421: 0.217 or V: Mo: Sb = 1: 0.42: 0.347. These conditions provide a 100% degree of isoprene conversion and a selectivity of the formation of citraconic anhydride of -30%. Many by-products are formed (aldehydes, mono- and dicarboxylic acids and their conversion products), the resulting complex mixture of products requires the use of complex methods for the isolation of the target product.

 The disadvantages of this method of producing citraconic anhydride is the complexity of the technology associated with the use of high temperature and complex methods for the isolation of the target product, low selectivity, the use of expensive and scarce isoprene raw materials.

These disadvantages are overcome in the proposed method for producing citraconic anhydride by carbonylation of methylacetylene, carried out in accordance with reactions (1) or (2), or (1) and (2) in a certain ratio in one technological stage in the presence of a homogeneous PdBr ₂ -LiBr- catalyst system organic solvent at temperatures of 30-60 ^{° C,} atmospheric pressure of the gaseous mixture of carbon monoxide and oxygen methylacetylene.

2[H] (1)
CH₃C ≡ CH+2CO+0,5O₂ ___→ C

(2)
Процесс проводят в проточном по газу термостатируемом реакторе с интенсивным перемешиванием газовой и жидкой фаз. Продукты карбонилирования идентифицируют и анализируют методами ЯМР-, ИК-, хроматомасс-спектроскопии, газожидкостной хроматографии и потенциометрического титрования. Кроме основного продукта процесса (селективность 30-80%), образуется цитраконовая кислота (20-30%) и в незначительных количествах метилянтарная кислота и соответствующий ей ангидрид, кротоновая кислота (КК), лактон 3-метил-бутен-2-овой кислоты. Целевой продукт вместе с цитраконовой кислотой выделяют экстракцией бензолом, гексаном, ацетоном или их смесями. Показатели процесса определяются концентрациями бромидов палладия и лития, воды, парциальными давлениями метилацетилена, оксида углерода, кислорода.CH ₃ C ≡ CH + 2CO + H ₂ O ___ → C

2 [H] (1)
CH ₃ C ≡ CH + 2CO + 0.5O ₂ ___ → C

(2)
The process is carried out in a gas-flowing thermostatic reactor with intensive mixing of the gas and liquid phases. The carbonylation products are identified and analyzed by NMR, IR, gas chromatography, mass spectroscopy, gas-liquid chromatography and potentiometric titration. In addition to the main product of the process (selectivity of 30-80%), citraconic acid (20-30%) is formed and, in small amounts, methyl succinic acid and its corresponding anhydride, crotonic acid (CC), and lactone 3-methyl-buten-2-one acid. The target product, together with citraconic acid, is isolated by extraction with benzene, hexane, acetone or mixtures thereof. Process indicators are determined by the concentrations of palladium and lithium bromides, water, and partial pressures of methylacetylene, carbon monoxide, and oxygen.

At palladium concentrations less than 0.1 mol / l (when carrying out the process according to equation (1)), the formation of the target product is very low, and an increase in [Pd] above 0.5 mol / l leads to an increased formation of methylacetylene oligomers and a decrease selectivity (examples 2-7). In the presence of oxygen, the selectivity and productivity of the process for the target product increases. The increase in the content (partial pressure) of oxygen above 20% leads to a decrease in the productivity of the process due to a decrease in the partial pressures of methylacetylene and carbon monoxide (examples 16-19). The process proceeds in the temperature range of 20-60 ^about C (examples 12-15).

The best range for CO: C ₃ H ₄ ratios is from 6: 1 to 1: 1 (Examples 20-28). When this ratio decreases below 1, the selectivity of the process decreases due to an increase in the oligomerization of C ₃ H ₄ , and when the ratio CO: C ₃ H ₄ > 6 increases, the productivity and selectivity of the process also decrease (examples 20-28).

The optimal concentration of water during the process should be maintained constant and in the range of 1: 5 wt. (0.45-2.2 mol / L). When the concentration of water decreases below 1% (0.45 mol / L), the productivity of the process is too low, and when the increase (H ₂ O) exceeds 5% (2.2 mol / L), the catalytic system loses stability (examples 34-37).

 Within the framework of these limitations, the proposed method for producing citraconic anhydride provides a simplification of the technology (lowering the temperature of the process) and a significant increase in selectivity compared to the prototype.

 Methylacetylene is a by-product of the pyrolysis of straight-run gasolines, thermo-oxidative pyrolysis of methane and does not find qualified use. Carbon monoxide is a byproduct in many industries. Utilization of by-products to produce citraconic anhydride, among other beneficial effects, would help preserve the environment.

EXAMPLE 1. 0.3194 g (0.1 mol / L) PdBr ₂ and 0.208 g (0.2 mol / L) LiBr are charged into a glass thermostatic reactor equipped with a reflux condenser and stirrer, and 12 ml are poured acetone with a water content of 2 wt. and stirred for 10-15 minutes at 40 ^about C until the salts are dissolved. Then pass the gas mixture CO: C ₃ H ₄ : O ₂ in the ratio of CO: C ₃ H ₄ = 1.8: 1 with a content of O ₂ 15 vol. at a rate of 15 ml / min. The gas composition at the inlet and outlet of the reactor is controlled by gas adsorption chromatography. The experiment was carried out for 3 hours. Then, 100 ml of C ₆ H _{6 was} added to the cooled contact solution and transferred to a separatory funnel. The mass of the contact solution after the experiment is 10.72 g. The composition of the solution is wt. acetone 80.92; citraconic anhydride 11.03; citraconic acid 5.1; methyl succinic acid 1.9; crotonic acid 1.05. After mixing, the products pass into the upper benzene layer. The layers are separated. The upper layer is distilled. The composition of the distillate, wt. citraconic anhydride 88.3; methyl succinic anhydride 6.9; crotonic acid 4.7.

 The performance of the process according to C.A. is 0.35 mol / l h (40 g / l h), according to C.K. 0.15 mol / L h

 Fresh acetone is added to the lower layer to a volume of 12 ml and water to 2 wt. and repeat the cycle (table 1).

 Methylacetylene carbonylation products are analyzed by IR, NMR, mass spectroscopy and GLC chromatography.

1.36 L of gas was absorbed in 3 hours, including CO- 0.8 L; C ₃ H ₄ 0.42 L; O2 0.14 l.

 The lower layer is used to prepare the catalyst in the following cycles (table 1).

PRI me R s 2-7. In a glass reactor, thermostated at 40 ^about C, load the desired amount of PdBr ₂ and LiBr, 12 ml of acetone with a water content of 2 wt. turn on the stirrer and mix the solution for 10 minutes. The gas mixture is then passed with a ratio of CO: C ₃ H ₄ = 2: 1 at a rate of 15 ml / min. The gas mixture contains 0.5 (vol.) O ₂ . After 3 hours, stirring and the gas mixture are stopped. The results are presented in table.2.

PRI me R s 8-11 The experiments are carried out as in example 2, at various concentrations of PdBr ₂ and LiBr. But in the reactor serves a gas mixture of CO: C ₃ H ₄ : O ₂ with a ratio of CO: C ₃ H ₄ = 2: 1 with an O ₂ content _of 15 vol. The results are presented in table. 3.

PRI me R s 12-15. 0.3194 g of PdBr ₂ (0.1 mol / l) and 0.208 g of LiBr (0.2 mol / l) are loaded into a glass reactor, thermostated at the desired temperature, 12 ml of acetylacetone with a water content of 3 wt. stirred for 10 min at the desired temperature until the salts are dissolved. Then pass the gas mixture of CO: C ₃ H ₄ : O ₂ with a ratio of CO: C ₃ H ₄ = 1.9: 1 at a content of 15 vol. O ₂ at a rate of 15 ml / min. The experiment is carried out for 2 hours (table 4).

PRI me R s 16-19. The experiments are carried out as in example 2. In the reactor serves a gas mixture of CO: C ₃ H ₄ : O ₂ with a ratio of CO: C ₃ H ₄ = 2.5: 1, but at different partial pressures of O ₂ (table 5).

PRI me R s 20-28. The experiments are carried out as in example 2, but with a change in the ratio of carbon monoxide and methylacetylene. The gas mixture contains 15 vol. About ₂ . The results are presented in table.6.

PRI me R s 29-33. The experiments are carried out as in example 2, but in various solvents. A gas mixture of CO: C ₃ H ₄ : O ₂ with a ratio of CO: C ₃ H ₄ = 2: 1 at a content of 15 vol. O ₂ (table 7).

 PRI me R s 34-37. The experiments are carried out, as in example 2, but at different concentrations of water (table 8).

Claims (1)

METHOD FOR PRODUCING A CITRACONE ANHYDRIDE by reacting a carbon-containing unsaturated compound with oxygen in the presence of a catalyst, characterized in that methylacetylene is used as a carbon-containing unsaturated compound, carbon monoxide is introduced into the reaction system in the range of the ratio carbon monoxide methylacetylene (6 1) 1, and catalyst is used system PdBr ₂ AiBr H ₂ O organic solvent such as a ketone, or acetic acid or acetonitrile, or γ-butyrolactone with concentrations components in the ranges in mol / l:
PdBr ₂ 0.05 0.8
LiBr 0.1 0.16
H ₂ O 0.45 2.2
Solvent Else
the process is carried out at 20 to 60 ^o C,
while the oxygen content in the reaction system is in the range of 0.5 to 19 vol.

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