JP4026350B2 - Method for producing alkyl nitrite - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for easily and efficiently producing alkyl nitrite from nitric acid and alkanol. Alkyl nitrite is a useful compound in various oxidation processes (production of dialkyl oxalate, dialkyl carbonate, etc.).
[0002]
[Prior art]
As a method for producing alkyl nitrite, a method of reacting nitric oxide and alkanol is known (JP-A-11-189570, JP-A-6-298706, etc.). However, this method was not satisfactory in terms of using nitric oxide as a starting material. That is, nitric oxide can be obtained by partial oxidation of ammonia or reaction of nitrite and acid. However, the former has problems such as severe oxidation conditions and a narrow operating range. Since nitrate was expensive, there was a problem that it was disadvantageous for industrial implementation.
[0003]
Furthermore, the above-mentioned method of reacting nitric oxide and alkanol is not satisfactory in that a considerable amount of nitric acid is produced as a by-product, and a method for efficiently producing alkyl nitrite while suppressing loss of nitrogen components has been desired. .
[0004]
On the other hand, as a method for producing nitric oxide, a method is known in which concentrated nitric acid is reduced with a metal such as bismuth, copper, lead, mercury, iron oxide (II), or diarsenic trioxide (Chemical Univ.). Dictionary 1 reduced edition, 32nd edition, page 665). However, these methods utilize an equimolar reaction and require a large amount of the above metals and oxides, which is not preferable as an industrial method.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide an industrially suitable method for producing alkyl nitrite capable of producing alkyl nitrite simply, inexpensively and efficiently.
[0006]
[Means for Solving the Problems]
As a result of intensive studies to solve the above-mentioned problems, the present inventors have completed the present invention. That is, this invention relates to the manufacturing method of the alkyl nitrite characterized by making nitric acid and an alkanol react with carbon monoxide or hydrogen in presence of a platinum group metal catalyst.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, nitric acid-containing aqueous solution can be preferably used as nitric acid. The nitric acid-containing aqueous solution is not particularly limited and may be a high-concentration nitric acid-containing aqueous solution. However, in consideration of catalyst recovery (recovery loss of platinum group metal component due to elution or dissolution of platinum group metal or a compound thereof) In order to effectively suppress the above), the nitric acid concentration is preferably 60% by weight or less, more preferably 20% by weight or less. Further, the nitric acid-containing aqueous solution may have a low concentration, and an alkyl nitrite can be efficiently produced even when the nitric acid concentration is 0.1% by weight or more. That is, when alkyl nitrite is produced industrially in consideration of catalyst recovery, the nitric acid-containing aqueous solution has a nitric acid concentration of 60% by weight or less (particularly 0.1 to 60% by weight), more preferably 20% by weight or less. What is (especially 0.1-20 weight%) is preferable, and what is 1-20 weight% is the most preferable especially.
[0008]
In the present invention, examples of the alkanol include methanol, ethanol, n-propanol, and i-propanol. Among these, methanol is preferable. The alkanol is the above-mentioned aqueous solution containing nitric acid (the concentration of nitric acid is 60% by weight or less (particularly 0.1 to 60% by weight), further 20% by weight or less (particularly 0.1 to 20% by weight), especially 1 to 20% by weight. It is preferable to use it after being contained (uniformly dissolved or mixed), and the concentration may be in the range of 5 to 70% by weight. Such nitric acid-containing aqueous solution containing alkanol is, for example, a by-product in the above-described method for producing alkyl nitrite by reacting nitric oxide with alkanol (JP-A-11-189570, JP-A-6-298706, etc.). A nitric acid-containing aqueous solution.
[0009]
In the present invention, examples of the platinum group metal catalyst include palladium, platinum, ruthenium, rhodium and osmium. Palladium and platinum are preferable, and palladium is more preferable. As the platinum group metal catalyst, the platinum group metal or a compound thereof can be used as it is (dissolved or suspended) in a nitric acid-containing aqueous solution. The catalyst is preferably used as a solid catalyst (in a fixed bed or suspension bed).
[0010]
In that case, the supported amount of the platinum group metal or the compound thereof is preferably 0.01 to 20% by weight, more preferably 0.1 to 15% by weight in terms of metal with respect to the carrier. Examples of platinum group metal compounds include inorganic acid salts (nitrates, hydrochlorides, sulfates, etc.) and organic acid salts (acetates, etc.) of the platinum group metals. Examples of the carrier include activated carbon and alumina, and activated carbon is preferable. The shape of the carrier is not particularly limited as long as it can be applied to a fixed bed or suspension bed (powder, granule, crushed material, etc.). The size of the carrier may be any as long as it can be applied to a fixed bed or a suspended bed.
[0011]
The platinum group metal catalyst is used in an amount of 0.0001 to 0.2% by weight, more preferably 0.0005 to 0.1% by weight, particularly 0.005 to 0.05% by weight in terms of metal based on the nitric acid-containing aqueous solution. % Is preferred. Specifically, for example, when 10% by weight of palladium metal supported on activated carbon (10% by weight Pd / C) is used, the amount used is 0.001 to 0.001 in terms of metal with respect to the nitric acid-containing aqueous solution. It is preferably 2% by weight, more preferably 0.005 to 1% by weight, and particularly preferably 0.05 to 0.5% by weight.
[0012]
Carbon monoxide and hydrogen may be used as they are or diluted with an inert gas such as nitrogen, and 1 to 20 moles, more preferably 1.5 to 10 moles, particularly 2 to 5 moles are used per mole of nitric acid. preferable.
[0013]
The temperature at the time of reacting nitric acid and alkanol with carbon monoxide or hydrogen is preferably 0 to 300 ° C, more preferably 20 to 100 ° C. The pressure of carbon monoxide or hydrogen is preferably from atmospheric pressure to 200 atm, more preferably from atmospheric pressure to 30 atm, particularly from 3 to 10 atm. The reaction is carried out until the nitric acid concentration (residual nitric acid concentration) in the reaction solution is 1% by weight or less, and further 0.5% by weight or less. It is preferable for suppressing recovery loss of metal components. In this case, if necessary, the reactor may be plural or multi-staged.
[0014]
That is, in the present invention, a solid catalyst in which a white metal or a compound thereof is supported on a support using a nitric acid-containing aqueous solution having a nitric acid concentration of 60% by weight or less (more preferably in the above range) and an alkanol of 5 to 70% by weight. It is particularly preferable to carry out the reaction in the presence of (preferably powder) until the nitric acid concentration (residual nitric acid concentration) in the reaction solution is 1% by weight or less (preferably in the above range). As a result, it is possible to make the support again support the white metal metal or its compound eluted or dissolved in the reaction solution by contact with nitric acid, and it is possible to achieve a process with substantially no recovery loss of the platinum group metal component. .
[0015]
The reaction of nitric acid and alkanol with carbon monoxide or hydrogen can be performed in a liquid phase, batchwise or continuously. In this reaction, for example, a nitric acid-containing aqueous solution (containing nitric acid and alkanol) and a platinum group metal catalyst are placed in a reactor, and the solution is stirred while carbon monoxide or hydrogen is circulated in the liquid. It is carried out by stirring the solution under pressure of carbon oxide or hydrogen. Furthermore, it can also be carried out by filling the reactor with a platinum group metal catalyst (as a fixed bed) and allowing the aqueous solution containing nitric acid and carbon monoxide or hydrogen to flow in countercurrent or cocurrent. The reactor may be a stirring tank, packed tower, trickle bed type, or the like. The produced alkyl nitrite is led out of the reaction system along with carbon monoxide or hydrogen (purified by washing or the like if necessary) and used for other reactions.
[0016]
【Example】
Next, the present invention will be specifically described with reference to examples and comparative examples. Nitric oxide and carbon dioxide were analyzed by gas chromatography, nitric acid was analyzed by ion chromatography, and dissolved palladium was analyzed by atomic absorption. Pd / C means a solid catalyst in which palladium metal (Pd) is supported on activated carbon (C), and Pt / C means a solid catalyst in which platinum metal (Pt) is supported on activated carbon (C).
[0017]
Example 1
In a 500 ml autoclave (manufactured by SUS316) equipped with a stirrer, gas supply nozzle, gas extraction nozzle, liquid extraction nozzle (with sintered metal filter), 14.7 wt% nitric acid aqueous solution 102 g, methanol 198 g, 10 wt% Pd / C 0.6 g (manufactured by NE Chemcat; powder) was added, purged with carbon monoxide, and then pressurized to 6 atm with carbon monoxide. Next, the temperature was raised to 60 ° C. while extracting gas from the gas extraction nozzle so as to maintain this pressure and supplying carbon monoxide from the gas supply nozzle at 6 NL (normal liter) / h with stirring.
[0018]
One hour after the temperature reached 60 ° C., the gas derived from the gas extraction nozzle was analyzed. As a result, methyl nitrite was 40% by volume, nitric oxide was 15% by volume, and carbon dioxide was 45% by volume. When the nitric acid concentration in the reaction solution was measured 3 hours after the temperature reached 60 ° C., the nitric acid concentration was 0.27 wt%, and the nitric acid conversion rate based on the charged nitric acid was 95%.
[0019]
Example 2
The reaction was performed in the same manner as in Example 1 except that instead of carbon monoxide, a carbon monoxide-nitrogen mixed gas (carbon monoxide content: 15 volumes) was supplied from the gas supply nozzle at 20 NL / h.
One hour after the temperature reached 60 ° C., the gas discharged from the gas extraction nozzle was analyzed. As a result, methyl nitrite was 11% by volume, nitric oxide was 0.1% by volume, and carbon dioxide was 10% by volume. It was. The nitric acid concentration in the reaction solution 3 hours after the temperature reached 60 ° C. was 0.47 wt%, and the nitric acid conversion rate based on the charged nitric acid was 91%.
[0020]
Example 3
The reaction was performed in the same manner as in Example 1 except that hydrogen was supplied at 6 NL / h from the gas supply nozzle instead of carbon monoxide.
One hour after the temperature reached 60 ° C., the gas extracted from the gas extraction nozzle was analyzed. As a result, 4.4% by volume of methyl nitrite, 0.1% by volume of nitric oxide, and 3.5% of carbon dioxide were obtained. It was volume%. Further, the nitric acid concentration in the reaction solution 5 hours after the temperature reached 60 ° C. was 4.45% by weight, and the conversion rate of nitric acid based on the charged nitric acid was 10.3%.
[0021]
Example 4
The reaction was conducted in the same manner as in Example 1 except that 0.6 g of 3 wt% Pt / C (manufactured by NE Chemcat; powder) was used instead of 10 wt% Pd / C.
Two hours after the temperature reached 60 ° C., the gas discharged from the gas extraction nozzle was analyzed. As a result, methyl nitrite was 8% by volume, nitric oxide was 0.2% by volume, and carbon dioxide was 12% by volume. It was. Further, the nitric acid concentration in the reaction solution at this time was 3.12% by weight, and the conversion rate of nitric acid based on the charged nitric acid was 38%.
[0022]
Example 5
A 500 ml autoclave (manufactured by SUS316) equipped with a stirrer, gas supply nozzle, gas extraction nozzle, liquid supply nozzle, liquid extraction nozzle (with sintered metal filter) was charged with 14.7 wt% nitric acid aqueous solution 102 g, methanol 198 g, 10 weight. 0.6 g of% Pd / C (manufactured by NE Chemcat; powder) was added, purged with carbon monoxide, and then pressurized to 6 atm with carbon monoxide. Next, while extracting gas from the gas extraction nozzle so as to maintain this pressure, while stirring, while supplying a carbon monoxide-nitrogen mixed gas (carbon monoxide content: 15 volumes) from the gas supply nozzle at 20 NL / h, The temperature was raised to 80 ° C.
[0023]
One hour after the temperature reached 80 ° C., feeding of a solution of 5% by weight of nitric acid, 66% by weight of methanol and 29% by weight of water was started at 90 g / h, and extraction of the reaction liquid was started at about 75 g / h. . Seven hours after starting the supply of the solution and the extraction of the reaction solution, the gas discharged from the gas extraction nozzle was analyzed. As a result, 9.1% by volume of methyl nitrite, 0.4% by volume of nitric oxide, and carbon dioxide were analyzed. It was 6.4% by volume. At that time, when the liquid derived from the liquid discharge nozzle was analyzed, the nitric acid concentration was 0.35% by weight, and the nitric acid conversion rate based on the charged nitric acid was 93%. The palladium dissolved in the liquid was 3 ppm in terms of metal.
[0024]
【The invention's effect】
According to the present invention, alkyl nitrite can be produced simply, inexpensively and efficiently. That is, by using nitric acid as a starting material, loss of nitrogen component can be suppressed, and alkyl nitrite can be produced easily, inexpensively and efficiently. In particular, if the concentration of nitric acid and residual nitric acid in the starting nitric acid-containing aqueous solution (including alkanol) is controlled using a solid catalyst in which a platinum group metal or its compound is supported on a carrier, the recovery loss of the platinum group metal component is reduced. Thus, the catalyst can be efficiently recovered while being suppressed, and an industrially suitable method for producing alkyl nitrite can be provided. In addition, the present invention can efficiently produce alkyl nitrite even in a low-concentration nitric acid-containing aqueous solution (including alkanol). For recovering nitrogen components from such nitric acid-containing aqueous solution as alkyl nitrite. Very useful.

Claims (6)

A process for producing alkyl nitrite, comprising reacting nitric acid and alkanol with carbon monoxide or hydrogen in the presence of a platinum group metal catalyst. The method for producing alkyl nitrite according to claim 1, wherein the platinum group metal catalyst is a solid catalyst in which a platinum group metal or a compound thereof is supported on a carrier. The method for producing an alkyl nitrite according to claim 1 or 2, wherein the platinum group metal is palladium or platinum. The method for producing an alkyl nitrite according to claim 2, wherein the nitric acid is a nitric acid-containing aqueous solution having a nitric acid concentration of 60% by weight or less. The method for producing an alkyl nitrite according to claim 4, wherein the nitric acid-containing aqueous solution contains 5 to 70% by weight of alkanol. The method for producing alkyl nitrite according to claim 2, wherein the reaction is carried out until the nitric acid concentration in the reaction solution is 1 wt% or less.