RU2631429C1 - Method of producing 4,4-dimethyl-1,3-dioxane (versions) - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing 4,4-dimethyl-1,3-dioxane (DMD) from isobutylene and formaldehyde by condensing isobutylene with formaldehyde aqueous solution in presence of phosphoric acid at elevated temperature and pressure in presence of synthetic NaA zeolites with pore diameter of 4 E or CaA with pore diameter of 5 E, the content of which is maintained in amount of 3.5-5.0 wt % of the reaction mass and the subsequent release of DMD from the reaction mass.

EFFECT: increasing the selectivity of DMD formation by reducing the amount of produced high-boiling by-products, including hydrogenated pyrans.

3 cl, 1 tbl, 3 ex

Description

The invention relates to the field of basic organic and petrochemical synthesis, and in particular to a technology for producing 4,4-dimethyl-1,3-dioxane from isobutylene and formaldehyde.

One of the most common industrial methods for producing isoprene is the dioxane method through the intermediate synthesis of 4,4-dimethyl-1,3-dioxane (DMD). DMD is obtained by liquid-phase condensation of isobutylene contained in fractions of C ₄ hydrocarbons with formaldehyde used in the form of a 20-40% aqueous solution, followed by isolation of dimethyldioxane from the reaction mixture [Ogorodnikov S.K., Idlis G.S. Isoprene production. L .: Chemistry, 1973, p. 48-58]. The principal disadvantage of this method is the low selectivity of the process. The yield of high-boiling by-products (WFP) is 440-460 kg per 1 ton of isoprene, more than 90% of which are WFP from the synthesis of dimethyldioxane [ibid, p. 72].

A known method for producing 4,4-dimethyl-1,3-dioxane from isobutylene and formaldehyde at a temperature of 100-110 ° C in the presence of sulfuric acid. The disadvantage of this method is the high corrosiveness of the reaction medium and the need for additional processing of the oil layer with an alkali solution [USSR Author's Certificate No. 361174, IPC C07D 319/06, publ. 12/07/1972].

Known methods for producing DMD in an aqueous medium from isobutylene and formaldehyde using a carboxylic acid as a catalyst [French Patent No. 2490642, IPC C07D 319/06, publ. 03/26/1982], salts of polysulfonic acid and a metal of group I or II [French Patent No. 2490643, C07D 319/06, publ. 03/26/1982], oxalic acid [USSR author's certificate No. 991715, IPC C07D 319/06, publ. 12/27/1999; RF patent №2255936, IPC C07D 319/06, publ. 07/10/2005].

A known method of producing DMD from formaldehyde and isobutylene in a weight ratio of 1.1-1.2 in an aqueous solution at 90-110 ° C and a pressure of 17-25 atm, in the presence of oxalic acid. To increase the selectivity for DMD and trimethylcarbinol (TMK) by reducing the formation of by-products and losses of isobutylene, 3-6% of TMK in the calculation of DMD and 5-20% of DMD from the resulting amount are returned to the reaction zone. According to the authors, the return of TMC to the reaction zone can reduce the formation of TMC esters with runway components and at the same time slow down the progress of the DMD hydrolysis reaction with the formation of runway [RF Patent No. 2062270, IPC C07D 319/06, C07C 31/12, publ. 06/20/1996].

The disadvantage of the above methods for producing DMD is the lack of selectivity for the target DMD due to the formation of runways due to the poor mutual solubility of hydrocarbons and the aqueous layer containing the catalyst and formaldehyde.

A known method of producing DMD [RF Patent No. 2255936, IPC C07D 319/06, publ. July 10, 2005] by condensation of an aqueous solution of formaldehyde and an isobutylene-containing fraction at 80-100 ° C and a pressure of 1.6-2.0 MPa in the presence of an acid catalyst. To increase the selectivity of the formation of DMD by reducing the formation of process wastes, distillate is sent to the condensation zone on a vacuum distillation column of the runway mixture. The return to the reaction zone of the synthesis products leads to an increase in the load on the reactor, respectively, a decrease in the conversion of the starting reagents and an increase in the content of hydrogenated pyranes (GP), which is a disadvantage of the known method.

Closest to the proposed technical essence and the achieved result is a known method for producing 4,4-dimethyl-1,3-dioxane [RF Patent No. 2330848, IPC C07D 319/06, publ. 08/10/2008] by condensation of isobutylene with an aqueous solution of formaldehyde in the presence of phosphoric acid, taken as an acid catalyst, at elevated temperature and pressure and subsequent isolation of 4,4-dimethyl-1,3-dioxane from the reaction mixture, the condensation being carried out in the presence of surfactants. The surfactant content is maintained in an amount of 0.001-10.0 wt.% Of the reaction mass. The method allows to increase the selectivity of the formation of DMD.

The disadvantages of this method are the insufficiently high selectivity for the target DMD due to the formation of runways, including GP, as well as the need for disposal of spent surfactants.

The aim of the invention is to increase the selectivity of the formation of DMD by reducing the amount of hydrogenated pyranes formed.

. Конденсацию проводят в присутствии цеолита NaA с диаметром пор 4

или СаА с диаметром пор 5

. Содержание синтетических цеолитов выдерживают в количестве 3,5-5,0 мас.% от реакционной массы.The goal is achieved by the proposed method for producing 4,4-dimethyl-1,3-dioxane by condensation of isobutylene with an aqueous solution of formaldehyde in the presence of phosphoric acid at elevated temperature and pressure and subsequent isolation of DMD from the reaction mixture, while condensation is carried out in the presence of synthetic zeolites with pore diameter 4-5

. Condensation is carried out in the presence of zeolite NaA with a pore diameter of 4

or CaA with a pore diameter of 5

. The content of synthetic zeolites is maintained in the amount of 3.5-5.0 wt.% From the reaction mass.

. Использование синтетических цеолитов с диаметром пор 4-5

обеспечивает более высокую степень превращения исходных реагентов - изобутилена и формальдегида, селективность по ДМД из-за уменьшения образования ВПП, в том числе ГП.The difference of the invention is that in order to increase the selectivity of the formation of DMD, synthetic zeolites with a pore diameter of 4-5 are additionally introduced into the reaction mixture

. The use of synthetic zeolites with a pore diameter of 4-5

provides a higher degree of conversion of the starting reagents - isobutylene and formaldehyde, selectivity for DMD due to a decrease in the formation of runways, including GP.

или СаА с диаметром пор 5

.The process under consideration is one of heterogeneous liquid-phase catalytic reactions. The separation of phases in the reactor, due to the mutual insolubility of the aqueous layer containing formaldehyde and the catalyst, and the hydrocarbon containing isobutylene, is the main problem of the selective formation of the target product of the process of condensation of isobutylene with formaldehyde. To solve this problem and increase the chemical affinity of the components of the heterogeneous mixture, the use of synthetic zeolites with a specific pore diameter as porous cocatalysts is proposed. The introduction of porous cocatalysts with a certain pore diameter into the reaction mass provides a more intensive course of the condensation reaction of isobutylene with formaldehyde, contributes to an increase in the yield of DMD and a decrease in the formation of HP. As an acid catalyst, 80-85% solutions of phosphoric acid are used; as an isobutylene-containing fraction, an isobutane-isobutylene fraction with an isobutylene content of 95-99 wt. %, formaldehyde is used, for example, in the form of a 16-22% aqueous solution. As porous cocatalysts, for example, synthetic NaA zeolites with a pore diameter of 4 can be used.

or CaA with a pore diameter of 5

.

The synthesis of DMD is as follows. The calculated amount of formalin, phosphoric acid, synthetic zeolite and isobutane-isobutylene fraction with a molar ratio of formaldehyde / isobutylene equal to 1.55: 1 is placed in a reactor equipped with a loading opening. The reactor is mounted on a mixing device and placed in a coolant with a predetermined temperature in the range of 80-90 ° C. Further include stirring. Overpressure in the range of 5-6 atm is maintained in the reactor, which ensures the process in the condensed phase. At the end of the experiment, the reaction mixture is cooled, discharged from the reactor, the zeolite is separated by filtration from the reaction mixture, then the oil and water layers are separately subjected to further processing. DMD is isolated from the oil layer by extraction. Then the content of DMD is determined by the chromatographic method of the internal standard. The selectivity of the process is determined by the ratio of DMD / runway in the resulting reaction mixture.

The implementation of the proposed method for producing DMD is illustrated by the following examples.

Example 1 (control, for comparison).

5.2 g of formalin with a formaldehyde concentration of 16.1 wt.% (0.028 mol), 1.1 g (0.018 mol) of isobutylene, 0.29 g of 81% phosphoric acid are placed in a reactor equipped with a loading opening. The molar ratio of formaldehyde / isobutylene is 1.55: 1. The reactor is mounted on a mixing device and placed in a coolant with a predetermined temperature. Further include stirring. A temperature of 82 ° C and a pressure of 6 atm are maintained in the reactor. The reaction mass is maintained with constant stirring for 1 hour. At the end of the experiment, the reactor is cooled to 25-30 ° C, the reaction mass is discharged from the reactor, the synthetic zeolite is separated from the reaction mass by filtration, then the oil and water layers are separately subjected to further processing. DMD is isolated from the oil layer by extraction. Get DMD 0.15 g (36% of theory), the ratio of DMD / runway is 2: 1.

Example 2

, что составляет 4,0% от массы реакционной смеси. В реакторе выдерживают температуру 82°С, давление 6 атм. Получают ДМД 0,17 г (41,0% от теоретического). Высококипящие побочные продукты, в том числе гидрированные пираны, в реакционной массе отсутствуют.The process is carried out analogously to example 1. 5.2 g of formalin solution with a concentration of formaldehyde of 16.0 wt.% (0.028 mol), 1.1 g of isobutylene (0.018 mol), 0.29 g of 81% phosphoric acid are placed in the reactor. The molar ratio of formaldehyde / isobutylene is 1.55: 1. An additional 0.25 g of synthetic NaA zeolite with a pore diameter of 4 is added to the reaction mixture.

, which is 4.0% by weight of the reaction mixture. A temperature of 82 ° C and a pressure of 6 atm are maintained in the reactor. DMD of 0.17 g (41.0% of theory) is obtained. High boiling point by-products, including hydrogenated pyranes, are absent in the reaction mass.

Example 3

, что составляет 4,0% от массы исходной реакционной смеси. В реакторе выдерживают температуру 82°С, давление 6 атм. Получают ДМД 0,18 г (44,0% от теоретического). Высококипящие побочные продукты, в том числе гидрированные пираны, в реакционной массе отсутствуют.The process is carried out analogously to example 1. 5.2 g of formalin solution with a concentration of formaldehyde of 16.0 wt.% (0.028 mol), 1.1 g (0.018 mol) of isobutylene, 0.29 g of 81% phosphoric acid are placed in the reactor. The molar ratio of formaldehyde / isobutylene is 1.55: 1. An additional 0.25 g of synthetic CaA zeolite with a pore diameter of 5 is added to the reaction mixture.

, which is 4.0% by weight of the initial reaction mixture. A temperature of 82 ° C and a pressure of 6 atm are maintained in the reactor. DMD 0.18 g (44.0% of theory) is obtained. High boiling point by-products, including hydrogenated pyranes, are absent in the reaction mass.

или 5

и содержание цеолитов количестве 3,5-5,0 мас.% от реакционной массы. Целесообразность выбранных пределов показателей технологического процесса конденсации представлена в таблице 1.The optimal conditions for the selective formation of DMD as a result of condensation of formaldehyde with isobutylene in the presence of synthetic zeolites are with a pore diameter of 4

or 5

and the content of zeolites in an amount of 3.5-5.0 wt.% from the reaction mass. The feasibility of the selected limits of the indicators of the technological process of condensation is presented in table 1.

DMD synthesis conditions: molar ratio formaldehyde: isobutylene = 1.55: 1, temperature 82 ° C, pressure 6 atm, synthesis time 1 hour.

или 5

в количестве меньше чем 3,5 мас.% приводит к снижению выхода ДМД, а более чем 5,0 мас.% - не приводит к увеличению выхода ДМД, но обуславливает дополнительный расход реагента.Application for the process of synthetic zeolites with pore diameters of 4

or 5

in an amount of less than 3.5 wt.% leads to a decrease in the yield of DMD, and more than 5.0 wt.% - does not lead to an increase in the yield of DMD, but causes an additional consumption of reagent.

ведет к уменьшению выхода и селективности образования целевого ДМД. Использование синтетического цеолита NaX с диаметром пор 9

ведет к резкому снижению выхода и селективности образования целевого ДМД.The use of synthetic zeolite KA with a pore diameter of 3

leads to a decrease in the yield and selectivity of the formation of the target DMD. The use of synthetic zeolite NaX with a pore diameter of 9

leads to a sharp decrease in the yield and selectivity of the formation of the target DMD.

As can be seen from the above examples, the present invention improves the selectivity of the formation of DMD by reducing the amount of high-boiling by-products formed, including hydrogenated pyranes.

Claims (3)

1. The method of producing 4,4-dimethyl-1,3-dioxane by condensation of isobutylene with an aqueous solution of formaldehyde in the presence of phosphoric acid at elevated temperature and pressure and subsequent isolation of 4,4-dimethyl-1,3-dioxane from the reaction mass, characterized the fact that the condensation is carried out in the presence of synthetic NaA zeolites with a pore diameter of 4

. 2. The method of obtaining 4,4-dimethyl-1,3-dioxane by condensation of isobutylene with an aqueous solution of formaldehyde in the presence of phosphoric acid at elevated temperature and pressure and the subsequent isolation of 4,4-dimethyl-1,3-dioxane from the reaction mass, characterized the fact that the condensation is carried out in the presence of synthetic zeolite CaA with a pore diameter of 5

. 3. The method of obtaining 4,4-dimethyl-1,3-dioxane according to claims. 1 and 2, characterized in that the content of synthetic zeolites is maintained in an amount of 3.5-5.0 wt.% From the reaction mass.