JPH1045665A - Production of glyoxylic acid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable direct synthesis of glyoxylic acid which is useful as a raw material for synthesizing perfumes, medicines, agrochemicals and the like by bringing glycolic acid into contact with molecular oxygen in the presence of a specific catalyst in high selectivity and high yield from a readily available raw material. SOLUTION: In the presence of (A) a catalyst containing (A1 ) FePO4 or (A2 ) Fe3 (P2 O7 )2 perferably containing >=20wt.% of A1 or A2 in which the atomic ratio of P/Fe is 1/1-1.8-1), (B) glycolic acid is brought into contact with (C) molecular oxygen (for example, a gas in which oxygen is diluted with nitrogen in an oxygen concentration of 10-30vol.% or air). In a preferred embodiment, the reaction is carried out at 200-280 deg.C under normal pressure for a contact time of 0.2-7 seconds.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing glyoxylic acid from glycolic acid, and more particularly to a method for producing glyoxylic acid by oxidatively dehydrogenating glycolic acid in the presence of an iron phosphate-based catalyst. Glyoxylic acid is useful as a raw material for synthesizing fragrances (such as vanillin), pharmaceuticals (such as blood coagulants and analgesics), pesticides (such as insecticides and plant growth regulators) and organic chemicals, and as raw materials for producing high molecular compounds. Compound.

[0002]

2. Description of the Related Art As a method for producing glyoxylic acid, a method for electrolytic reduction of oxalic acid (US Pat. No. 4,692,226) is known.
), A method of oxidizing glyoxal with nitric acid (Japanese Unexamined Patent Publication No.
176456), a method of oxidizing glycolic acid with an oxidase (PCT Int. Appl. WO95)
01444) and the like, and in particular, a method using an oxidase and a method using electrolytic reduction have recently attracted attention. However, all of these methods are low in productivity and complicated in operation. Further, a method of dehydrogenating glycolic acid in the presence of copper or a catalyst containing copper and zirconium is also known (JP-A-6-157399), but the selectivity and yield of glyoxylic acid are low.

[0003] In addition, a method of hydrolyzing a glyoxylate obtained by oxidizing a glycolate is also known. However, when glycolic acid is used as a raw material, a step of esterifying glycolic acid, an oxidation of glycolate, Step 3 of glyoxylate ester hydrolysis step
There is a problem that a process is required and the process becomes complicated. The glycolic acid ester is oxidized by, for example, contacting the glycolic acid ester with molecular oxygen in the presence of a catalyst in which ferric phosphate is supported on α-alumina (JP-A-2-91046). However, the yield of glyoxylate is not so high, and the preparation of the catalyst requires complicated pretreatment.

[0004]

SUMMARY OF THE INVENTION In view of the above technical background, the present invention oxidizes glycolic acid, which is industrially easily available, to directly convert glyoxylic acid with high selectivity and high yield. It is an object to provide a manufacturing method.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to provide an FeP.
This is achieved by a method for producing glyoxylic acid, which comprises contacting glycolic acid with molecular oxygen in the presence of a catalyst containing O ₄ or Fe ₃ (P ₂ O ₇ ) ₂ .

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The glycolic acid used as a raw material in the present invention contains glycolic acid in an amount of 1% by weight or more, particularly 3 to 70% by weight, and more preferably 5% by weight.
It is preferably an aqueous solution of glycolic acid containing about 50% by weight.

The catalyst used in the present invention is FePO_Four(Re
Ferric acid) or Fe_Three(P_TwoO₇)_TwoCatalyst containing
It is. FePO_FourAs a tridemite type, quartz type
FePO_FourAnd Fe_Three(P_TwoO₇)_TwoWhen
For example, α-type (Y-phase) and β-type (B-phase) Fe_Three(P
_TwoO₇)_TwoIs mentioned. Among these, α-type and β-type
Fe_Three(P_TwoO₇)_TwoIs stably present during the reaction,
Are also suitable as catalysts because they show high activity and high selectivity.
You.

The catalyst is FePO_FourOr Fe_Three(P
_TwoO₇)_TwoEven if they consist of
Even if they are present, they are also mixed with diluents.
They may be combined. In addition, FePO_FourWhen
Fe_Three(P_TwoO₇)_TwoMay be used. Furthermore,
The catalyst is Fe_TwoP_TwoO₇(Ferrous pyrophosphate)
Α-type Fe_Three(P_TwoO₇)_TwoStrange
From Fe _TwoP_TwoO₇Consisting of or
Is Fe_TwoP_TwoO₇May be contained.
No. FePO in catalyst_FourOr Fe_Three(P_TwoO₇)_TwoIncluding
The amount is less than 100% by weight, more than 10% by weight, in particular
It is preferably at least 20% by weight. Also, the catalyst
Excess phosphoric acid may be contained, but phosphorus
The acid is the atomic ratio of phosphorus to iron contained in the catalyst (P: Fe)
Is contained in the range of 1: 1 to 1.8: 1.
Is preferred.

Among the above-mentioned catalysts, as a method for preparing FePO ₄ , for example, after mixing (or kneading) an iron-containing compound and a phosphorus-containing compound in the presence of water, a coprecipitate (or kneaded material) is mixed. ) Is dried and calcined. At this time, as the iron-containing compound, inorganic salts of iron (iron nitrate, iron carbonate, iron chloride, ferrous phosphate, etc.), organic acid salts of iron (iron oxalate, iron acetate, etc.), oxidation of iron (Eg, iron oxide), iron hydroxide (eg, iron hydroxide) and the like. Examples of the phosphorus-containing compound include ammonium salts of phosphoric acid (eg, ammonium phosphate), phosphoric acid (eg, orthophosphoric acid, metaphosphoric acid, etc.). ), And phosphorus chlorides (such as phosphorus pentachloride).

In the above catalyst preparation, drying is performed in air at a temperature of 50 to 200 ° C., and calcination is performed in air at 300 to 200 ° C.
C. or higher, especially at a temperature of 400 to 800.degree. If the calcination temperature is lower than 300 ° C., FePO ₄ may not be sufficiently generated, and if it is higher than 800 ° C., the specific surface area of the obtained catalyst may be extremely small, which is not preferable.

The α-type Fe ₃ (P ₂ O ₇ ) ₂ is FePO
₄ is brought into contact with a reducing gas at 100 to 600 ° C., especially 160 to 500 ° C., to form Fe ₂ P ₂ O ₇ (completely divalent iron atoms are reduced).
Reoxidize at 0-550 ° C (contact with molecular oxygen)
It is prepared by Examples of the reducing gas include hydrogen (H ₂ ), ammonia, carbon monoxide, hydrocarbons (methane, ethane, etc.) and other organic substances (methanol,
A gas containing formaldehyde, glycolic acid, etc.) is used. These reducing gases may be a pure gas, a mixed gas, or a gas diluted with an inert gas. Also, β-type Fe ₃ (P ₂ O ₇ )
₂ means that FePO ₄ is heated to 100 to 600 ° C.,
It is prepared by contacting the above reducing gas at 00 ° C. (partially reducing iron atoms).

The molecular oxygen used in the present invention is supplied to the reaction system as a molecular oxygen-containing gas. As the molecular oxygen-containing gas, oxygen gas, inert gas (nitrogen gas, etc.)
Gas, air, etc., diluted with nitrogen gas are used, and among them, gas (O ₂ concentration: 10 to 30% by volume) diluted with nitrogen gas and air are preferably used. In the reaction for producing glyoxylic acid, it is preferable that molecular oxygen is supplied in an amount of 0.3 to 20 mol, particularly 0.4 to 5 mol, per 1 mol of glycolic acid.

The reaction of the present invention is carried out in the gas phase, for example, by supplying glycolic acid and molecular oxygen to a reactor filled with the above-mentioned catalyst. At this time, the reaction temperature is 180 to 300
C., particularly preferably from 200 to 280C. The reaction pressure may be normal pressure, pressurized or reduced pressure,
Generally, normal pressure is appropriate. The contact time is 0.1
It is preferably about 10 to 10 seconds, particularly about 0.2 to 7 seconds. Further, the reaction of the present invention is not limited to the gas phase, and may be carried out, for example, in a liquid phase suspension system or a trickle system.

In the present invention, steam may be supplied to the reactor together with glycolic acid or molecular oxygen to carry out the reaction. A larger amount of water vapor supplied to glycolic acid tends to improve the selectivity and yield of the target product, but an excessively large amount of water vapor is not preferable because the economic efficiency is reduced. The water vapor is preferably supplied in an amount of 2 to 100 mol, particularly 5 to 80 mol, per 1 mol of glycolic acid. For example, the required amount of water vapor can be supplied by heating and evaporating a glycolic acid aqueous solution, or the required amount of water can be separately evaporated and supplied. The glyoxylic acid produced as described above is separated and purified by a general method such as distillation under reduced pressure or thin film after condensing a reaction gas derived from a reactor, for example.

[0015]

Next, the present invention will be described specifically with reference to examples and comparative examples. The conversion of glycolic acid, the selectivity of glyoxylic acid, and the yield of glyoxylic acid were determined by the following equations.

[0016]

(Equation 1)

[0017]

(Equation 2)

[0018]

(Equation 3)

[0019] Example 1 Water 5000ml ferric nitrate [Fe (NO _{3) 3} · 9H
₂ O] was dissolved 122g, the pH was adjusted to 8.0 by adding ammonia to the solution. The generated precipitate is separated and 8
After adding 41.5 g of 5% by weight phosphoric acid, the solution was added to 10%.
Heated at 0 ° C. for 1 hour then evaporated to dryness. The obtained dried product was dried in air at 150 ° C. for 8 hours, pulverized and sized to 4 to 10 mesh, and fired in air at 480 ° C. for 5 hours to obtain 49 g of a fired product. The obtained calcined product (particle diameter: 1 to 2 mm) is a tridemite-type FePO ₄ (ferric phosphate) from an X-ray diffraction spectrum, and according to redox titration, 95% or more of the iron atoms are trivalent. Was iron.

Example 2 The fired product obtained in Example 1 was filled in a stainless steel reaction tube having an inner diameter of 18 mm, and then N ₂ : H ₂ (volume ratio) =
While flowing a 1: 1 mixed gas at 50 ml / min, 3
Reduction was performed at 00 ° C. for 5 hours. From the X-ray diffraction spectrum, the obtained reduced product was found to be β-type Fe ₃ (P ₂ O ₇ ) ₂ (B
Phase).

Example 3 The fired product obtained in Example 1 was filled into a stainless steel reaction tube having an inner diameter of 18 mm, and then N ₂ : H ₂ (volume ratio) =
5: 1 while flowing a 1: 1 mixed gas at 50 ml / min.
Reduction was performed at 00 ° C. for 5 hours to obtain Fe ₂ P ₂ O ₇ (ferrous pyrophosphate). Next, air: water vapor (volume ratio)
Oxidation was performed at 480 ° C. for 2 hours while flowing a mixed gas of 10: 3 at 100 ml / min. The obtained oxide was found to be α-type Fe ₃ (P ₂ O ₇ ) from the X-ray diffraction spectrum.
₂ (Y phase), and according to redox titration, 36% of the iron atoms were divalent iron.

Examples 4 to 8 Tridemite-type FeP obtained in Example 1 was used as a catalyst.
After filling 20 g of O ₄ into a stainless steel reaction tube having an inner diameter of 18 mm, glycolic acid: oxygen: nitrogen: water vapor [flow (mmol / hr) ratio] = 12.3: 3.8 to 2 under normal pressure.
While flowing at a ratio of 5: 500: 480, the reaction was carried out for 3 hours at the reaction temperature, oxygen concentration and contact time shown in Table 1. The reaction gas was cooled and the recovered product was analyzed by gas chromatography. Table 1 shows the results.

Examples 9 to 11 The β-type Fe ₃ (P
_The reaction and analysis were carried out in the same manner as in Example 4 except that 20 g of ₂ O ₇ ) ₂ (B phase) was used. Table 1 shows the results.

Examples 12 and 13 The α-type Fe ₃ (P) obtained in Example 3 was used as a catalyst.
_The reaction and analysis were carried out in the same manner as in Example 4 except that 20 g of ₂ O ₇ ) ₂ (Y phase) was used. Table 1 shows the results. Table 1 shows the results of the examples.

[0025]

[Table 1]

Comparative Example 1 A comparative example shows an example in which similar VP-based and heteropolyacid-based catalysts are applied to the reaction of the present invention as a catalyst for the oxidative dehydrogenation reaction. V ₂ O ₅ 18.2 g of benzyl alcohol - isobutyl alcohol: to reflux for 2 hours to give a black suspension in [1 1 (volume ratio)] solution. After 21.2 g of 98% by weight phosphoric acid was added thereto and refluxed for 2 hours, the solvent was removed to obtain a solid. The solid is dried in air at 150 ° C for 6 hours, then in air at 300 ° C for 6 hours and 45 hours.
It was baked at 0 ° C. for 12 hours. The obtained oxide was (VO) ₂ P ₂ O ₇ (vanadiyl phosphate; V / P = 1 / 1.06) from the X-ray diffraction spectrum. Example 4 except that 20 g of the above (VO) ₂ P ₂ O ₇ was used as a catalyst.
The reaction and analysis were performed in the same manner as described above. Table 1 shows the results.

Comparative Example 2 As a catalyst, H ₃ Mo ₁₂ O ₄₀ (phosphomolybdic acid; manufactured by Kanto Chemical Co.) was calcined in air at 370 ° C. for 6 hours.
The reaction and analysis were carried out in the same manner as in Example 4 except that g was used. Table 1 shows the results.

Comparative Example 3 Example 4 was repeated except that 20 g of H ₅ PMo ₁₂ V ₂ O ₄₀ (phosphorus vanadomolybdic acid; manufactured by Kanto Chemical Co.) fired at 370 ° C. for 6 hours in air was used as a catalyst. Reaction and analysis were performed similarly. Table 1 shows the results. Table 2 shows the results of the comparative example.

[0029]

[Table 2]

[0030]

According to the present invention, glyoxylic acid can be directly produced with high selectivity and high yield from glycolic acid which is industrially easily available.

Claims (2)

[Claims] 1. In the presence of a catalyst containing FePO ₄ ,
A method for producing glyoxylic acid, which comprises contacting glycolic acid with molecular oxygen. 2. A method for producing glyoxylic acid, which comprises contacting glycolic acid with molecular oxygen in the presence of a catalyst containing Fe ₃ (P ₂ O ₇ ) ₂ .