RU2057109C1 - Process for preparing 2,6-dimethyl substituted phenols - Google Patents

Abstract

FIELD: organic chemistry. SUBSTANCE: 2,6- dimethylsubstituted phenol are prepared by vapor phase orthomethylation of phenol, ortho-, metha-or paracresol with methanol under counterflow conditions in the presence of oxide iron-vanadium manganese catalysts which are molded with binder or applied on widely porous silica gel, then activated at 200-400 C and calcined to give catalysts with iron-vanadium-manganese atomic ratio of (0.5-1):(1-0.5): (0.05-0.5) containing more than 30 wt% active component. The catalyst has large pores having radius of more than 15 nm and pore size of 0.5-1.5 cm³/g. EFFECT: more efficient preparation process. 2 tbl

Description

 The invention relates to a process for the catalytic methylation of phenols having two ortho hydrogen atoms with the formation of 2,6-dimethyl derivatives of phenols in the presence of iron-vanadium manganese oxide catalysts.

 Methyl derivatives of phenols are very valuable substances and have a wide range of applications in organic and inorganic synthesis. They are used as antioxidants and stabilizers of fuels and lubricants, various fats, synthetic rubber, as well as starting materials in the synthesis of nonionic surfactants, structural materials, plant protection products, medicines, vitamin E, etc.

Currently, the main method for producing methyl derivatives of phenols is the catalytic methylation of phenol in the liquid and vapor phases [1] In the process of methylation, methyl ether and various isomeric methyl phenols are formed. As the catalysts, various acids, salts, individual oxides and oxide compositions are used. It was shown that the conditions of alkylation and the composition of the products formed substantially depend on the catalysts used. It follows from the published patent literature that the catalysts based on iron and vanadium oxides are the most effective in the ortho methylation reaction of phenols [2, 3]. It is proposed to methylate phenols containing at least one hydrogen atom in the ortho position in the presence of oxide catalysts containing iron and vanadium, as well as additives of the third component [2] The ranges of the compositions of the catalysts and the reaction mixture were established, at which methylation of the benzene ring in ortho . The selectivity by the sum of mono- and dimethylphenol on these catalysts is 97-98%; however, the selectivity for the formation of 2,6-dimethylphenols does not exceed 83%
The aim of the invention is to develop a more efficient method for producing 2,6-dimethyl derivatives of phenols.

As a result of the work, it was found that highly selective methylation of phenol, o-, m- and p-cresol with a selectivity of formation of 2,6-dimethyl derivatives up to 85-97% can be carried out on iron-vanadium manganese oxide catalysts containing components within the atomic ratios of Fe: V: Mn (0.5-1) :( 1-0.5) :( 0-0.5). The catalysts should be in the crystalline state and having after calcination in the temperature range of 500-800 ^C. large pores with radius greater than 15 nm and a volume of 0.5-1.5 cm ³ / g. In addition, in order to shorten the development period characteristic of catalysts of this type and increase selectivity, the catalysts must be activated by treatment with reducing agents, such as hydrogen, methanol, etc., before starting the reaction. at temperatures of 200-400 ^about C.

Any soluble salts of these elements, preferably iron and manganese nitrates and vanadium oxalate, can be used to prepare the iron-vanadium manganese oxide catalysts. Catalysts are obtained from a solution of salts of the starting components in the corresponding molar ratios using one of the methods: co-precipitation followed by filtration and drying, spray drying of a salt solution or suspension obtained from this solution at elevated pH. The resulting powder is either plasticized with a binder followed by granulation of the paste by extrusion through a die of a given shape and size, or tablets of a certain size are also prepared from it. The resulting granules or tablets of the catalyst are dried and calcined in the temperature range 500-800 ^about C.

In addition to massive catalysts, it is proposed to use supported catalysts in this process. It was shown that the most effective carrier is broad-pore silica gel with a pore radius of 30-4000 nm and a volume of 0.5-1.0 cm ³ / g. Aerosil is used for its preparation, which is first plasticized, granulated, and then the obtained granules are thermocouple in an autoclave at a temperature of 250-350 ^о С. and annealing.

The phenol methylation reaction is carried out in a flow reactor with a fixed catalyst bed. A sample of the catalyst is placed in a reactor with an internal diameter of 1.8 cm, a layer (4-5 cm) of crushed quartz with a particle size of 3-5 mm is poured on top, which serves as an evaporator of the reaction mixture. The catalyst was calcined in a reactor in a nitrogen flow (1.15 L / s) at a temperature of 350-550 ^C for 1 h. It was then treated with a reducing agent (hydrogen, methanol, etc.) at a temperature of 200 to 400 ^C. within 15-45 minutes After activation is complete, without stopping the supply of nitrogen, a mixture of phenol, methanol and water is fed into the reactor. The molar ratio between the components of the reaction mixture varies within Φ: M: B 1: (1-10) :( 1-10). The reaction is conducted at a temperature of 300-400 ^C. The reaction products collected in a cold trap and analyzed by gas-solid chromatography. Contact time is varied by changing the feed rate of the reaction mixture and the catalyst sample.

 According to the results of chromatographic analysis of the phenolic part and reaction products, the degree of phenol conversion and the methylation selectivity are determined. The degree of conversion (X,) is defined as the ratio of the number of moles of reacted phenol to the missing, the selectivity of methylated phenol formation (S,) is defined as the ratio of the number of moles of methylated phenol formed and the reacted phenol.

PRI me R 1. In a reactor equipped with a stirrer, pour 1.2 l of distilled water and bring its temperature to 70-90 ^about C, after which 300 g of oxalic acid are dissolved in it with stirring. Then, 100 g of V ₂ O ₅ are added to this solution; after its dissolution, the solution is cooled. To the resulting solution was added 444.2 g of Fe (NO ₃ ) ₃ 9H ₂ O and 63.1 g of Mn (NO ₃ ) ₂ 6H ₂ O. The atomic ratio of the components in the solution Fe: V: Mn 1: 1: 0.2. After dissolving the salts, a 12% ammonia solution is added to this solution with vigorous stirring until a pH of 4 is reached. The resulting suspension is sprayed on a spray dryer. The powder was calcined at 250 ^{° C,} and the binder is placed in a Z-shaped mixer and kneaded for 0.5 hours. The resulting paste was granulated by extrusion through a die of 3 mm diameter. Cylindrical granules with a size of 3 x 3 mm are dried, and then calcined at 650 ^about C.

4 g of catalyst are loaded into the reactor, a layer of quartz (4-5 cm) used as an evaporator of the reaction mixture is poured on top of the catalyst layer. Before testing, the catalyst activity is calcined in the reactor ^at 400 ° C under a nitrogen stream, then the temperature was lowered to 375 ^{° C} and, without stopping the supply of nitrogen to the reactor a liquid mixture of phenol (P), methanol (M), water (B) in a molar 1: 5: 3 ratio. The volumetric feed rate of the nitrogen-vapor mixture is 1410 h ^-1 . The reaction products are collected in a trap and analyzed by gas chromatography.

 A feature of iron-vanadium manganese catalysts is their development during the first hour in the reaction medium. The content of 2,6-xylene in the reaction products after 30 minutes is 64-65 mol.

 In the table. 1-3 show the results of the stationary activity of the catalysts.

PRI me R 2. In a reactor equipped with a stirrer, pour 2.6 liters of water, heated to 60 ^about C and dissolve in it 41.8 g of NH ₄ VO ₃ . In another vessel, a solution of iron and manganese salts is prepared; for this, 144.3 g of Fe (NO ₃ ) ₃ 9H ₂ O and 14.7 g of Mn (NO ₃ ) ₂ 6H ₂ O are dissolved in 100 ml of distilled water. In a reactor with a solution NH ₄ VO _{3 is} poured with a solution of salts of iron and manganese, the resulting suspension is evaporated to a pasty state and the paste is granulated by extrusion, granule size 3 x 3 mm. The granules are dried and calcined analogously to example 1. The atomic ratio of the components in the resulting catalyst Fe: V: Mn 1: 1: 0.14.

The activity test is carried out analogously to example 1, the volumetric feed rate of the nitrogen-vapor mixture of 1070 h ^-1 .

Example 3. A solution of vanadyl oxalate, iron nitrate (III) and manganese nitrate (II) (Fe: V: Mn 1: 1: 0.1), prepared analogously to example 1, is sprayed on a spray dryer. The resulting powder is tabletted, tablet size 3 x 3 mm. The heat treatment of the catalyst is similar to example 1. The activity test is analogous to example 1, the volumetric feed rate of the reaction mixture is 1020 h ^-1 .

PRI me R 4. The catalyst is prepared analogously to example 3, the atomic ratio of the components Fe: V: Mn 1: 1: 0.05. The activity test is analogous to example 1, the volumetric feed rate of the reaction mixture is 1020 h ^-1 , the molar ratio f: M: B 1: 8: 2.

PRI me R 5. The catalyst is prepared analogously to example 3, the atomic ratio of Fe: V: Mn 1: 1: 0.1. The activity test is analogous to example 1, the volumetric feed rate of the nitrogen-vapor mixture is 350 h ^-1 , the molar ratio Ф: M: B 1: 8: 2.

PRI me R 6. The catalyst is prepared analogously to example 5. The activity test is carried out analogously to example 1, the volumetric feed rate of 1060 h ^-1 , the molar ratio F: M: B 1: 5: 4.

PRI me R 7. The catalyst is prepared analogously to example 3, the atomic ratio of Fe: V: Mn 1: 1: 0.3. The activity test is carried out analogously to example 1, the volumetric feed rate of the nitrogen-vapor mixture of 880 h ^-1 .

PRI me R 8. The catalyst is prepared analogously to example 3 without manganese, the atomic ratio of Fe: V 1: 1. The activity test is carried out analogously to example 1, the volumetric feed rate of the nitrogen-vapor mixture of 830 h ^-1 .

 PRI me R 9. The catalyst is prepared analogously to example 8, the atomic ratio of Fe: V of 0.8: 1. The activity test is carried out analogously to example 8.

 PRI me R 10. The catalyst is prepared analogously to example 8, the atomic ratio of Fe: V of 1.2: 1. The activity test is carried out analogously to example 8.

PRI me R 11. The catalyst is prepared analogously to example 3 without iron, the atomic ratio V: Mn 1: 0.1. The activity test is carried out analogously to example 1, the volumetric feed rate of the nitrogen-vapor mixture of 580 h ^-1 .

 PRI me R 12. The catalyst is prepared analogously to example 11, the atomic ratio V: Mn 1: 0,3. The activity test is carried out analogously to example 11.

PRI me R 13. The catalyst is prepared analogously to example 1, the atomic ratio of Fe: V: Mn 1: 0.7: 0.3. The catalyst suspension is dried to a paste-like state, and then granulated by extrusion, granule size 3 x 3 mm The heat treatment of the granules is similar to example 1, the volumetric feed rate of the nitrogen-vapor mixture is 2210 h ^-1 , the molar ratio F: M: B 1: 8: 3.

PRI me R 14. The catalyst is prepared by impregnation of wide-pore silica gel with a solution of salts of iron, vanadium and manganese, prepared analogously to example 1, with an atomic ratio of Fe: V: Mn 1.1: 1: 0.2. Silica gel is prepared by mixing 1 kg of aerosil grade A-175, 2 l of water and 30 g of ammonium acetate in a Z-shaped paddle mixer. The mass is mixed until a plastic paste is formed, then it is granulated by extrusion through a die with a diameter of 3 mm. Granules of size 3 x 3 mm was air dried first ^at 20 ° C and then at ¹¹⁰ ° C, and then autoclaved in water vapor at ³⁵⁰ ° C for 24 h. The silica gel has a pore volume of 30-4000 nm radius 1 cm ³ / g, its specific surface area is 10 m ² / g.

Calcined at 200-300 ^C. silica doubly impregnated by incipient wetness with a solution of iron salts, vanadium and manganese, prepared analogously to Example 1, with intermediate drying the pellets at 110 ° ^C. The content of SiO ₂ in the catalyst is 73 wt. The heat treatment of the granules is similar to example 1. The activity test is analogous to example 1, the space velocity of the nitrogen-vapor mixture is 530 h ^-1 .

PRI me R 15. The catalyst is prepared analogously to example 14, the autoclaving temperature of silica gel 250 ^about C. The ratio of the components in the impregnating solution of Fe: V: Mn 1.4: 1.0: 0.2. The content of SiO ₂ in the catalyst 72 wt. The activity test is carried out analogously to example 1, the volumetric feed rate of the nitrogen-vapor mixture of 580 h ^-1 .

91,3%
П р и м е р 18. Катализатор готовят аналогично примеру 1. Испытание активности проводят аналогично примеру 1, вместо фенола используется о-крезол (о-Кр), соотношение о-Кр:M:B 1:5:3. Объемная скорость подачи азотно-паровoй смеси 1250 ч^-1.EXAMPLE Example 16. The catalyst is prepared analogously to Example 1: Test of activity was carried out analogously to Example 1. Before feeding the reaction mixture, the catalyst is activated: sparged with hydrogen for 30 minutes at a temperature of 250 ^{° C,} then the temperature was raised to 375 ^{° C} and reacted . The activity of the catalyst in 30 minutes approaches the stationary value: X ₃₀ 98.4% S _x30 75.4%
PRI me R 17. The catalyst is prepared analogously to example 1. The activity test is carried out analogously to example 1. Activation of the catalyst is carried out in pairs of methanol for 30 min at 350 ^about C. X ₃₀ 97.3% S

91.3%
PRI me R 18. The catalyst is prepared analogously to example 1. The activity test is carried out analogously to example 1, instead of phenol, o-cresol (o-Cr) is used, the ratio of o-Cr: M: B 1: 5: 3. The volumetric feed rate of the nitrogen-vapor mixture is 1250 h ^-1 .

 In the table. 1 shows the stationary characteristics of the activity of the catalysts of examples 1-18.

PRI me R 19. The catalyst is prepared analogously to example 1. The activity test is carried out analogously to example 1, instead of phenol, m-cresol (m-Cr) is used, the ratio of components in the reaction mixture is m-Cr: M: B 1: 5: 3 the volumetric feed rate of the nitrogen-vapor mixture of 1330 h ^-1 .

PRI me R 20. The catalyst is prepared analogously to example 1. The activity test is carried out analogously to example 19, the volumetric feed rate of the nitrogen-vapor mixture of 1570 h ^-1 .

PRI me R 21. The catalyst is prepared analogously to example 1, the activity test is carried out analogously to example 19, the ratio of components in the reaction mixture m-Cr: M: B 1: 8: 3, the volumetric feed rate of the reaction mixture is 1600 h ^-1 .

 The results of examples 19-21 are shown in table. 2.

PRI me R 22. The catalyst is prepared analogously to example 1. The activity test is carried out analogously to example 1, instead of phenol, p-cresol (p-Cr) is used, the ratio of components is p-Cr: M: B 1: 5: 3, space velocity filing a nitrogen-vapor mixture of 1370 h ^-1 .

PRI me R 23. The catalyst is prepared analogously to example 1. The activity test is carried out analogously to example 22, the volumetric feed rate of the nitrogen-vapor mixture of 1660 h ^-1 .

 The results of examples 22 and 23 are shown in table. 3.

 As can be seen from the above results, the proposed method for the methylation of phenols having hydrogen atoms in the ortho position in the presence of large-pore iron-vanadium manganese catalysts increases the activity and selectivity of the 2,6-methyl derivatives of phenols in comparison with known methods. In addition, the proposed preliminary activation of the catalysts in the presence of reducing agents significantly reduces the development period of such catalysts.

Claims (1)

METHOD FOR PRODUCING 2,6-DIMETHYL SUBSTITUTED PHENOLS by vapor-phase orthomethylation of phenols in the presence of oxide iron-manganese manganese catalysts, characterized in that the catalysts use massive catalysts pre-activated at a temperature of 200-400 ^° C in a reducing agent, or iron-yellow catalysts with broad porous silica gel not less than 30 wt. %, the atomic ratio of Fe and V metals is 0.5 - 1: 1 - 0.5 or Fe: V: Mn 0.5 - 1: 1 - 0.5: 0.05 - 0.5, while the catalyst has large pores with a radius of more than 15 nm with a pore volume of 0.5 - 1.5 cm ³ / g.

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