RU2527455C1 - Method of producing aldehydes - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing aldehydes via hydroformylation of terminal or internal olefins in the presence of a catalyst system containing rhodium and a mono- or polyphosphite ligand. An antioxidant is added to the reaction mixture, the antioxidant being phenols or thioureas of general formulae:

where R denotes identical or different aliphatic or aromatic univalent radicals or hydrogen, and hydroformylation is carried out in liquid phase in a solvent medium in form of aldehyde, with rhodium concentration of 0.1-2 mmol/l, at temperature of 20-150°C and pressure of 0.2-5 MPa, wherein the amount of the antioxidant is 1-30 mol/mol phosphite ligand.

EFFECT: invention enables to obtain end products using an efficient method at low raw material costs.

2 tbl, 15 ex

Description

The invention relates to basic organic, fine organic and petrochemical synthesis and can be used for hydroformylation of olefins into the corresponding aldehydes.

Hydroformylation of linear olefins is an industrial large-scale process for producing aldehydes and products based on them. One option for the process is the hydroformylation of olefins on homogeneous rhodium catalysts modified with phosphite ligands. Along with the advantages, such catalytic systems have several disadvantages - the high cost of Rh and ligands, and the high reactivity of ligands in undesirable destructive processes. The appearance of acids, water, oxygen and other chemically active compounds in the reaction medium leads to the rapid degradation of triorganophosphites. There are several ways of converting phosphite ligands - hydrolysis with the formation of acid phosphites, interaction with aldehydes with further rearrangement into alpha-hydroxyphosphonates, oxidation (Applied Catalysis A, 2001, T.212. S. 61-81).

Despite the fact that phosphite ligands are considered more resistant to oxidation than phosphine ligands, this is true only in the case of oxidation by molecular oxygen. In an aliphatic aldehyde medium, ligand oxidation proceeds at significantly higher rates, since the aldehyde acts as an oxygen mediator. The interaction of the aldehyde with oxygen produces highly active radicals of acyl, hydroperoxide and other types, as well as peroxide (Uspekhi Khimii, 1985, Vol. 54. Issue 6. P.903-922), which are able to interact with the ligand faster than molecular oxygen, for example (Advances in Chemistry, 1971, Vol. 40. Issue 2. S.254-275):

RCHO + O ₂ → RC (O) OOH; (RO) ₃ P + RC (O) OOH → RC (O) OH + (RO) ₃ P = O.

For these reasons, high demands are made on the purity of the raw materials used. To suppress the noticeable oxidation of phosphites, the oxygen content in the feed should not exceed 1-10 ppm or less. For this reason, to increase the service life of the catalyst composition, stages of deep purification of raw materials from oxygen are necessary. This leads to a rise in price of the resulting aldehydes and products based on them. In addition, at the time of the initial start of the process, the oxidation of the ligand by the oxygen not completely removed from the system and sorbed on the equipment with oxygen is especially intense.

The literature describes several methods for slowing down the degradation of a phosphite ligand by introducing various additives into the reaction mixture. However, based on their chemical nature, they do not solve oxidation problems. Thus, a method is known for hydroformylating olefins (US Pat. No. 5,364,950) with additives of compounds containing an oxirane ring to bind hydroxyphosphonates. These substances allow inactivation of acids formed from phosphites, but do not have antioxidant properties.

A method is proposed for neutralizing acids formed from phosphites by continuously passing part of the stream of catalyst solution through a column with an ion-exchange resin (US Pat. No. 4,599,206). However, this method requires the introduction of additional equipment that can be a source of sorbed oxygen.

A known method of producing aldehydes by hydroformylation of olefins (US patents 5731472, US 5744650) with the introduction into the reaction mixture of amines or nitrogen-containing heterocycles that interfere with the autocatalytic hydrolysis of phosphites. However, the addition of amines causes side processes, for example, oligomerization of aldehydes. In addition, amines cannot prevent the oxidation of phosphite in an aldehyde solution.

There is evidence of the addition of 2,6-ditretbutyl-4-methylphenol to the hydroformylation reaction mixture as an antioxidant (WO 195003702, US 4,599,206). However, what technical result this leads to and how it affects the stability of the phosphite ligand is not reported. At the same time, it is known that insufficiently voluminous mononuclear phenols are able to transesterify P-O bonds of ligands, destroying their structure, which is especially critical for polyphosphites and high temperature regions (above 100-110 ° C). This prevents the use of large concentrations of antioxidants of this type, which are necessary to reduce the requirements for the purification of raw materials and achieve at the same time a long-term action of the catalytic complex.

Monophosphines (US 6153800, US 2012/0029242) can be used to stabilize expensive polyphosphites. However, the addition of phosphines causes a decrease in the activity of the catalyst; moreover, the use of specific and rather inaccessible ligands (both phosphine and phosphite) is required to level this effect.

The objective of the invention is the creation of an effective way to obtain aldehydes and reduce costs for its implementation by mitigating the requirements for the quality of purification of raw materials and reduce the consumption of expensive organophosphorus ligand.

The technical result consists in suppressing the oxidation of an organophosphorus ligand by oxygen impurities in the presence of an aldehyde product or solvent, as a result of which the degradation of the ligand is slowed down, the service life of the catalytic system is prolonged and, therefore, its consumption is reduced. At the same time, the requirements for raw material purity and hardware design are reduced in terms of preventing the contact of the catalyst solution with atmospheric oxygen.

The technical result is achieved by adding to the reaction medium during hydroformylation of olefins on a rhodium catalyst modified with phosphite ligands, antioxidants of the thiourea class and bulk bisphenols in amounts of 1-30 equivalents relative to the ligand. These antioxidants have the general formulas:

where R is the same or different aliphatic or aromatic monovalent radicals or hydrogen. As antioxidants from these formulas, thiourea, N-methyl-N, N′-diphenylthiourea, 2,2′-methylene bis (6-tert-butyl-4-methylphenol), 2,2′-bis can be used (4, 6-di-tert-butylphenol) and others.

The presented substances act as radical traps, binding active oxidizing agents formed from aldehyde and oxygen, and thus prevent the oxidation of phosphite. For example, reactions are carried out:

Hydroformylation of olefins can be carried out at temperatures of 20-150 ° C, a total pressure of hydrogen, carbon monoxide and unsaturated compounds of 0.05-5 MPa, a partial pressure of hydrogen of 0.01-3 MPa, a partial pressure of carbon monoxide of 0.01-3 MPa.

The implementation of the present invention is illustrated by the following examples.

Example 1

33.36 mg of diphosphite ligand A are dissolved in 10 ml of acetone. The prepared solution in an amount of 1 ml in air is transferred into a 4 ml vial containing 2 ml of acetone, shaken and analyzed by HPLC. After 14 and 42 minutes, the concentration of phosphite in the solution does not change and corresponds to the calculated 1.11 mg / ml. This example demonstrates that ligand A is resistant to air in an acetone solution.

Ligand A

Example 2

The operations are carried out analogously to example 1 except that instead of 2 ml of acetone, 2 ml of freshly distilled butyraldehydes (a mixture of n- and isobutyral with a ratio of n / iso ~ 1) are placed in a vial. Immediately after mixing the solutions by HPLC, the initial phosphite A is not detected, and peaks are observed related to the products of oxidation of one or two phosphorus atoms. This example shows that in the presence of aldehydes, ligand A undergoes rapid oxidation in air.

Examples 3-6

The operations are carried out analogously to example 2 with the exception that 13 mol per 1 mol of phosphite A 2,2′-methylene bis (6-tert-butyl-4-methylphenol), N-methyl-N, N′- diphenylthiourea, thiourea or 2,2′-bis (4,6-di-tert-butylphenol). Samples are analyzed by HPLC at the time intervals indicated in Table 1, finding the amount of phosphite remaining in% relative to its calculated initial concentration (1.11 mg / ml). The result is presented in table 1.

Examples 3-6 show that the addition of antioxidants of the phenol, thiourea and phosphine class slows down the oxidation of a phosphite ligand in an aldehyde solution.

Table 1 Example Antioxidant* N% Immediately after mixing 14 min after mixing 42 min after mixing 2 no 0 0 0 3 MVTVMR 80 79 75 four Mdptu ~ 100 88 59 5 TU 72 53 31 6 Bdtbp 98 88 85 * MWTMP = 2,2′-methylene bis (6-tert-butyl-4-methylphenol), MDPTU = N-methyl-N, N′-diphenylthiourea, TU = thiourea, BDTBP = 2,2′-bis (4 , 6-di-tert-butylphenol).

N,% = 100% * C / Co, where C is the current phosphite concentration in the solution, Co is the initial phosphite concentration calculated on the basis of the load.

Comparative Example 1C

In a 100 ml Parr Instrument steel autoclave equipped with thermostatic and mixing devices, 20 ml of a mixture of butyraldehydes (n / iso ~ 1), 1.52 mg Rh (acac) (CO) ₂ and 50.33 mg are placed in an argon stream ligand A (A / Rh = 10, [Rh] = 0.3 mmol / L). The autoclave is purged with nitrogen (3 * 1.5 MPa) and heated to 90 ° C. After that, a sample of the liquid phase (1 ml) corresponding to the solution before the start of the reaction is taken. A portion of the solution (0.2 ml) was placed in a vial (0.3 ml) containing ~ 3 mg of thiourea, and the fraction of undegradable free ligand in% of the theoretical amount found on the basis of the catalyst load was determined by HPLC. Then 3 ml of propylene are introduced into the autoclave, the total pressure is adjusted to 2 MPa by means of synthesis gas supply (H ₂ / CO = 1) and the process is carried out at a constant pressure, finding the initial reaction rate (TOF, mol of aldehyde per 1 mol of Rh per hour) on the absorption of synthesis gas from a calibrated measuring tank. Upon completion of the synthesis gas absorption, the autoclave is cooled, hydroformylation regioselectivity (S _H ) is calculated based on GLC analysis of the initial and resulting aldehyde mixture. The fraction of the non-degraded ligand is determined by HPLC as described above. The result is presented in table 2. Comparative example 1C shows that in the absence of an antioxidant and without special measures to prevent oxygen from entering the solvent, more than 90% of the free diphosphite ligand decomposes before the reaction begins.

Comparative Example 2C

All operations are carried out similarly to comparative example 1C except that the catalyst is first loaded into the autoclave in an argon stream, after which the autoclave is vacuumized with an oil pump to 0.1 Torr and butyraldehyde freshly distilled in the atmosphere is introduced through a thin steel capillary. The loading is carried out in a current of CO without depressurization of the distillation apparatus. The result is presented in table 2. In comparison with example 1C, comparative example 2C shows that measures to prevent the contact of the aldehyde solvent with atmospheric oxygen significantly slow down the destruction of the diphosphite ligand.

Examples 7-9

All operations are carried out similarly to comparative example 1C, except that before loading the aldehyde solvent, an antioxidant is placed in the autoclave (see Table 2) in an amount of 3 mol per 1 mol of ligand A. In comparison with comparative example 1C, examples 7-9 show that the addition of an antioxidant prevents the dramatic oxidation of free diphosphite during hydroformylation. In comparison with comparative example 2C, it is seen that the antioxidant practically does not affect the speed and regioselectivity of the target reaction.

Comparative Example 3C

In a 100 ml Parr Instrument steel autoclave equipped with thermostatic and mixing devices, 19 ml of a mixture of butyraldehydes (n / iso ~ 1), 1 ml of a solution of Rh (acac) (CO) ₂ in p-xylene containing 0.517 mg of the indicated rhodium complex, and 38.86 mg of ligand B (B / Rh = 30, [Rh] 0.1 mmol / L). The autoclave is purged with nitrogen (3 * 1.5 MPa) and heated to 90 ° C. After that, a sample of the liquid phase (1 ml) corresponding to the solution before the start of the reaction is taken. A portion of the solution (0.2 ml) was placed in a vial (0.3 ml) containing ~ 3 mg of thiourea, and the fraction of undegraded free ligand was determined by HPLC. Then 8 ml of propylene are introduced into the autoclave, the total pressure is adjusted to 2.1 MPa by means of synthesis gas (H ₂ / CO = 1) and the process is carried out at a constant pressure, finding the initial reaction rate (TOF, mol of aldehyde per 1 mol of Rh per hour) on the absorption of synthesis gas from a calibrated measuring tank. Upon completion of the synthesis gas absorption, the autoclave is cooled, the regioselectivity of hydroformylation (S _H ) is calculated on the basis of GLC analysis of the initial and resulting mixture of aldehydes. The fraction of non-degraded free ligand is determined by HPLC as described above. The result is shown in Table 2. Comparative example 3C shows that in the absence of an antioxidant and without taking special measures to prevent oxygen from entering the solvent, about 50% of the free monophosphite ligand decomposes before the reaction begins. At the same time, the intensive formation of an oxidation product, phosphate, is detected by HPLC.

Ligand B

Example 10

All operations are carried out analogously to comparative example 3C, except that before loading the aldehyde solvent, 2,2′-methylene bis (6-tert-butyl-4-methylphenol) is placed in the autoclave, (see table 2) in an amount of 3 mol per 1 mol of ligand B. In comparison with comparative example 3C, example 10 shows that the addition of an antioxidant significantly slows down the oxidation of free monophosphite.

Comparative Example 4C

In a 100 ml Parr Instrument steel autoclave equipped with thermostatic and mixing devices, 17 ml of a mixture of butyraldehydes (n / iso ~ 1), 3 ml of a solution of Rh (acac) (CO) ₂ in p-xylene containing 7.78 mg of the indicated rhodium complex, and 195.11 mg of ligand B (B / Rh = 10, [Rh] 1.5 mmol / L). The autoclave is purged with nitrogen (3 * 15 atm) and heated to 130 ° C. After that, a sample of the liquid phase (1 ml) corresponding to the solution before the start of the reaction is taken. A portion of the solution (0.2 ml) was placed in a vial (0.3 ml) containing ~ 3 mg of thiourea, and the fraction of undegraded free ligand was determined by HPLC. Next, 8 ml of butene-2 is introduced into the autoclave, the total pressure is adjusted to 3.5 MPa by means of synthesis gas (H ₂ / CO = 1) and the process is carried out at constant pressure, finding the initial reaction rate (TOF, mol of aldehyde per 1 mol Rh per hour) for the absorption of synthesis gas from a calibrated measuring tank. Upon completion of the synthesis gas absorption, the autoclave is cooled, the regioselectivity of hydroformylation (S _H ) is calculated based on GLC analysis. The fraction of the non-degraded ligand is determined by HPLC as described above. The result is shown in Table 2. Comparative example 4C shows that in the absence of an antioxidant and without taking special measures to prevent oxygen from entering the solvent, about 50% of the free monophosphite ligand decomposes before the reaction begins.

Example 11

All operations are carried out similarly to comparative example 4C, except that before loading the aldehyde solvent, 2,2'-bis (4,6-di-tert-butylphenol) is placed in the autoclave (see Table 2) in an amount of 30 mol per 1 mol ligand B. In comparison with comparative example 4C, example 11 shows that the addition of an antioxidant prevents the dramatic oxidation of free monophosphite and does not impair the performance of the hydroformylation process of the internal olefin.

table 2 Example Ligand Antioxidant ^* Antioxidant / ligand TOF, h ^-1 Sh ^** ,% N ^*** ,% before the reaction after the reaction 1C BUT No - 13100 93 7 0 2C BUT No - 14400 96 92 fifty 7 BUT MVTVMR 3 13300 95 99 54 8 BUT TU 3 11400 95 87 49 9 BUT Mdptu 3 13000 96 99 fifty 3C B No - 58700 55 49 40 10 B MVTVMR 3 63300 57 84 69 4C B No - 44130 thirty 52 33 eleven B Bdtbp thirty 46280 31 97 93 ^* MBTBMP = 2,2′-methylene bis (6-tert-butyl-4-methylphenol), MDPTU = N-methyl, N, N′-diphenylthiourea, TU = thiourea, BDTBP = 2,2′-bis (4 , 6-di-tert-butylphenol). ^** Sh = 100% × n / (n + iso), where n is the yield of linear aldehyde, iso is the yield of branched aldehyde. ^*** N,% = 100% * C / Co, where C is the current concentration of phosphite in solution, Co is the initial concentration of free ligand, calculated on the basis of the load of phosphite and rhodium.

Claims (1)

The method of producing aldehydes by hydroformylation of terminal or internal olefins in the presence of a catalytic system containing rhodium and a mono- or polyphosphite ligand, characterized in that an antioxidant is added to the reaction mixture, which are used phenols or thioureas, of the general formulas:

,
where R is the same or different aliphatic or aromatic monovalent radicals or hydrogen, and hydroformylation is carried out in the liquid phase in a solvent medium, which is used as an aldehyde, at a rhodium concentration of 0.1-2 mmol / l, at a temperature of 20-150 ° C and pressure of 0.2-5 MPa, while the amount of antioxidant is 1-30 mol per 1 mol of phosphite ligand.