JP2003327562A - Method for producing alkyl nitrite - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an alkyl nitrite, comprising reacting an alkanol with nitrogen monoxide and oxygen to produce the alkyl nitrite, by which the alkyl nitrite can be efficiently produced at a high production rate. <P>SOLUTION: This method for producing the alkyl nitrite, comprising supplying the alkanol into the upper portion of a reaction tower for producing the alkyl nitrite to flow down to the lower portion of the reaction tower, supplying the nitrogen monoxide and the oxygen or their mixture gas into the lower portion of the reaction tower, and simultaneously reacting the alkanol with the nitrogen monoxide and the oxygen, is characterized by (1) extracting the bottom from the bottom portion of the reaction tower, introducing the bottom into a reactor for converting nitric acid, supplying carbon monoxide or hydrogen to react the nitric acid and the alkanol with the carbon monoxide or the hydrogen in the bottom in the presence of a platinum group metal catalyst to produce the alkyl nitrite, and (2) supplying the produced alkyl nitrite into the alkanol- flowing zone of the reaction tower. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a process for producing an alkyl nitrite in which nitric oxide, oxygen and an alkanol are reacted with each other to produce an alkyl nitrite. It relates to a method of manufacturing. Alkyl nitrite is a useful compound for various oxidation processes (production of dialkyl oxalate, dialkyl carbonate, etc.).

[0002]

2. Description of the Related Art A process for producing an alkyl nitrite by reacting nitric oxide, oxygen and an alkanol to produce an alkyl nitrite is to supply the alkanol to the upper part of the reaction column and to make it flow from the upper part to the lower part of the reaction column. , A method of reacting nitric oxide and oxygen with an alkanol to produce alkyl nitrite while supplying nitric oxide and oxygen or a mixed gas thereof to the lower part of the reaction tower, and extracting alkyl nitrite from the top of the reaction tower Are known (Patent Documents 1 and 2). However, in this method, since a considerable amount of nitric acid is produced as a by-product, there has been a demand for a method capable of efficiently producing alkyl nitrite by increasing the production ratio of alkyl nitrite.

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 or mercury, or iron (II) oxide or diarsenic trioxide (non-concentrated). Patent Document 1). However, these methods utilize a stoichiometric reaction and require a large amount of the above-mentioned metals and oxides, which is not preferable as an industrial method.

[0004]

[Patent Document 1] JP-A-11-189570

[Patent Document 2] JP-A-6-298706

[Non-Patent Document 1] Chemistry Dictionary 1 Reduced Edition No. 32, 665
page

[0005]

DISCLOSURE OF THE INVENTION The present invention relates to a process for producing an alkyl nitrite in which nitric oxide, oxygen and an alkanol are reacted to produce an alkyl nitrite, and the production ratio of the alkyl nitrite is increased to efficiently and efficiently generate nitrous acid. It is an object to provide a method capable of producing alkyl.

[0006]

The present inventors have completed the present invention as a result of intensive studies to solve the above problems. That is, the present invention supplies alkanol to the upper part of the reaction tower for producing alkyl nitrite and causes it to flow from the upper part to the lower part of the reaction tower, while nitric oxide and oxygen or a mixed gas thereof is supplied to the lower part of the reaction tower. In a process for producing an alkyl nitrite, in which nitric oxide, oxygen and an alkanol are reacted to produce an alkyl nitrite while being supplied, (1) a tower bottom liquid is extracted from a bottom of a reaction tower for producing an alkyl nitrite to convert nitric acid. Is introduced into a reactor for use in the presence of a platinum group metal catalyst, carbon monoxide or hydrogen is supplied, and nitric acid and alkanol in the bottom liquid of the column are reacted with carbon monoxide or hydrogen to generate alkyl nitrite. (2) The method for producing an alkyl nitrite, characterized in that the alkyl nitrite is supplied to an area where an alkanol is flowing down in a reaction tower for producing an alkyl nitrite.

[0007]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below with reference to the drawings. In the present invention, as shown schematically in FIG. 1, an alkanol supply line 11 is used to supply liquid alkanol to the upper part (between the upper part and the top part) of a reaction tower 1 for producing alkyl nitrite (hereinafter, also referred to as reaction tower 1); The same) to flow down from the upper part of the reaction tower 1 to the lower part thereof, and at the same time, nitric oxide and oxygen or a mixed gas thereof is supplied to the lower part of the reaction tower 1 (between the lower part and the bottom part;
The same shall apply hereinafter) while reacting nitric oxide, oxygen and alkanol (gas-liquid contact reaction; first reaction) to generate alkyl nitrite (first alkyl nitrite).

In the present invention, subsequently, the produced alkyl nitrite is withdrawn from the top of the reaction column 1 through the first reaction gas withdrawing line 13, and the bottom liquid is removed from the reaction column 1.
Withdrawing from the bottom of the column through a column bottom liquid withdrawing line 14 and introducing a part of the column bottom liquid (deriving column bottom liquid) into the nitric acid conversion reactor 2 (hereinafter, also referred to as reactor 2),
By supplying carbon monoxide or hydrogen from the nitric acid conversion gas supply line 16 to the reactor 2 and reacting nitric acid and alkanol in the bottom liquid of the introduction column with carbon monoxide or hydrogen in the presence of a platinum group metal catalyst. , Nitric acid (produced as a by-product in the first reaction)
Is converted to alkyl nitrite, and the alkyl nitrite (second
Alkyl nitrite) is extracted through the second reaction gas extraction line 17 and is supplied to the area of the reaction column 1 where the alkanol is flowing down (that is, nitric acid is converted to alkyl nitrite and recovered). As an area where the alkanol of the reaction column 1 for supplying the second alkyl nitrite flows down, an intermediate portion (described later) of the reaction column 1 is preferable.

In the present invention, further, "the above-mentioned outlet bottom liquid (most of it) is taken out by a tower bottom liquid circulation line 18 branched from the middle of the bottom liquid take-out line 14 and is introduced into a cooler 3 for cooling. The cooled tower bottom liquid (cooling tower bottom liquid) is circulated and supplied to an intermediate portion of the reaction tower 1, preferably below a connecting portion of the second reaction gas extraction line 17, and is supplied from the intermediate portion of the reaction tower 1. It is particularly preferable to react the nitric oxide, oxygen and alkanol while continuously performing the bottom liquid circulation operation under the conditions described below.

The present invention will be described in more detail below. Nitrogen monoxide supplied to the reaction tower 1 for producing alkyl nitrite may contain nitrogen dioxide, dinitrogen trioxide, dinitrogen tetraoxide, etc. in addition to nitric oxide. It is preferably more than 50% of the total of nitrogen dioxide and nitrous oxide in terms of gram atom. Oxygen (molecular oxygen) is 0.02 to 1 mol of nitric oxide.
It is preferable to mix and use 0.25 mol, more preferably 0.05 to 0.20 mol.

The above-mentioned nitric oxide and oxygen are usually mixed with an inert gas (nitrogen, carbon dioxide, etc.) and used as a raw material in the lower portion (preferably the upper portion thereof) of the reaction tower 1 for producing alkyl nitrite. It is supplied as a gas, and its composition is such that the total of nitric oxide and oxygen is 3 to 40% by volume (especially 5 to 20% by volume), and the inert gas is 10 to 90% by volume (especially 20 to 8% by volume).
It is preferably about 0% by volume. The source gas is
2-40% by volume of alcohol in vapor or mist form
Of carbon monoxide and nitrite may be further contained.

The nitric oxide and oxygen or a mixed gas thereof are mixed with, for example, nitric oxide (usually mixed with an inert gas) in an oxygen supply line 15 so as to have the above composition.
Oxygen is supplied to the lower part of the reaction tower 1 through the source gas supply line 12 as a source gas. Alternatively, nitric oxide and oxygen may be separately supplied (usually mixed with an inert gas) to the lower portion of the reaction tower 1 so as to have the above composition.

The alkanol supplied to the reaction tower 1 for producing alkyl nitrite is preferably an alkanol having 1 to 3 carbon atoms (especially methanol) such as methanol and ethanol, and alkyl nitrite is produced corresponding to this alkanol. To do. The alkanol is preferably used in the range of −15 ° C. to 50 ° C., more preferably −10 ° C. to 30 ° C. (cooled if necessary), and the alkanol is supplied to the upper part of the reaction column 1 for reaction. It is preferable that the column is made to flow from the upper part to the lower part and the nitric oxide, oxygen and alkanol are subjected to countercurrent gas-liquid contact reaction. The amount of the liquid alkanol supplied to the upper part of the reaction tower is the total nitric oxide supplied to the reaction tower (the total supply amount of nitric oxide to the reaction tower 1; the nitric oxide in the source gas and the nitric oxide produced from the nitric oxide and oxygen). Of each of the above-mentioned nitrogen oxides, and also nitric oxide introduced into the reaction tower 1 from the reactor 2;
It is preferably 3 to 2 times the molar amount. Further, in the present invention, as described above, a part of the alkanol may be contained in the raw material gas in the form of vapor or mist and supplied to the lower part of the reaction tower 1, and the composition of the raw material gas may be changed by another supply line. You may supply to the lower part of the reaction tower 1 within the range.

The temperature for reacting nitric oxide, oxygen and alkanol in the reaction tower 1 is 0 to 100 ° C., more preferably 5 to 100 ° C.
It is preferably in the range of 80 ° C, particularly 10 to 60 ° C. In the present invention, when reacting nitric oxide, oxygen and an alkanol, as described above, the bottom liquid of the reaction tower 1 is withdrawn via a liquid transport means (not shown) such as a pump, Most of the bottom liquid (deriving tower bottom liquid) is taken out and guided to the cooler 3 to be cooled, and the cooled tower bottom liquid (cooling tower bottom liquid) is circulated and supplied to the intermediate portion of the reaction tower 1 to cause reaction tower 1
It is more preferable to continuously carry out the column bottom liquid circulation operation. This bottom liquid circulation operation is
To the reaction tower 1 nitric oxide and oxygen (or mixed gas thereof)
It is preferable to carry out simultaneously and continuously with the operation of supplying alkanol and alkanol to react them, and the bottom liquid extracted from the bottom of the reaction column 1 (deriving bottom liquid) is a reaction that occurs in the lower region of the reaction column 1. It is preferable to use most of the bottom liquid circulation operation in a range where heat can be effectively removed and the reaction temperature can be maintained within the above range.

In the column bottom liquid circulation operation, (a) the circulating feed amount of the column bottom liquid (that is, the amount of the cooling column bottom liquid supplied to the intermediate portion of the reaction column 1) is adjusted to the alkanol supply amount to the reaction column 1. 50-30
0 times by weight, further 60 to 180 times by weight, especially 70 to 16 times
The amount of the alkanol supplied to the reaction tower 1 and the total amount of the alkanol in the tower bottom liquid (that is, the cooling tower bottom liquid) circulated and supplied to the middle part of the reaction tower 1 are the same as The total nitrous oxide supplied to the tower 1 (total nitrogen oxide supply to the reaction tower 1) is 20 to 150 times mol, further 30 to 120 times mol, and (c) the alkanol concentration in the bottom liquid is 1
The amount is preferably 5 to 60% by weight, more preferably 20 to 55% by weight. In the bottom liquid circulation operation, the outlet bottom liquid is
It is preferable to cool to a temperature in the range of about 0 to 60 ° C and lower than the temperature of the bottom liquid at the bottom of the reaction tower 1 by 1 to 20 ° C (particularly 3 to 10 ° C). In the present invention, the reaction heat generated in the lower region of the reaction tower 1 can be effectively removed and the nitric acid produced as a by-product can be reduced by performing the tower bottom liquid circulation operation particularly under the conditions (a) to (c). It can be suppressed to a level, and the first reaction can be efficiently performed.

The amount of alkanol supplied to the reaction tower 1 is the total amount of liquid and vapor-like (or mist-like) alkanol newly supplied into the reaction tower 1 from the outside, for example, as shown in FIG. For example, liquid alkanol supplied through the alkanol supply line 11 to the upper part of the reaction tower 1,
It is the total amount of vapor-like (or mist-like) alkanol that accompanies the nitric oxide supplied from the source gas supply line 12 to the lower part of the reaction tower 1. The alkanol in the circulation bottom liquid (cooling bottom liquid) circulated and supplied to the middle part of the reaction tower 1 through the bottom liquid circulation line 18 and the second reaction gas extraction line 17 supply from the reactor 2 to the reaction tower 1. Done second
Alkanol that accompanies the alkyl nitrite is not included in the amount of alkanol supplied to the reaction column 1. The alkanol in the bottom liquid of the circulation tower (bottom liquid of the cooling tower) is preferably about 0.5 to 6 times mol, more preferably about 1 to 5 times mol of the total supply amount of nitric oxide to the reaction tower 1.

As shown in FIG. 1, the reaction tower 1 has an upper region capable of absorbing water for removing water produced by a reaction (first reaction) of nitric oxide, oxygen and an alkanol, and an upper region. It may be any one having a lower region where the first reaction can be carried out, but it is preferable that the upper region and the lower region are installed at an appropriate interval (referred to as an intermediate portion).

The upper region may be of any type as long as it has a function of allowing alkanol to flow down and absorbing water in an upward flow by the alkanol. For example, it may have a multi-stage distillation column type structure having a plurality of trays such as sieve trays and valve trays, or a packed column type structure filled with a packing material such as Raschig rings and pole rings. Also,
The lower region may have any form as long as it has a function of effectively performing the first reaction. For example, it may have a multi-stage distillation column type or packed column type structure similar to the upper region.

That is, as the reaction tower 1, for example, as shown in FIG. 1, the upper area of the reaction tower 1 has a multi-stage distillation tower type or packed tower type structure, and the lower area has a packed tower type structure. Further, it is preferable to have a structure in which the upper region and the lower region are integrally and continuously connected with each other at an appropriate interval (that is, with an intermediate portion provided).

In the reaction tower 1, as shown in FIG.
The feed gas supply line 12 for supplying nitric oxide is in the lower part (preferably in the upper part thereof), the alkanol supply line 11 for supplying the alkanol is in the upper part, and the produced alkyl nitrite (first First reaction gas extraction line 1 for extracting alkyl nitrite)
Preferably 3 are each connected to the top. An oxygen supply line 15 for supplying oxygen may be connected to the source gas supply line 12, and the first reaction gas extraction line 13 may be purged for purging a part of the first reaction gas. The line 19 may be further connected.

In the reaction tower 1, as shown in FIG.
A column bottom liquid withdrawal line 14 for withdrawing the column bottom liquid and introducing it into the reactor 2, an area where the alkanol of the reaction column 1 flows down the alkyl nitrite (alkyl secondary nitrite) produced in the reactor 2 ( Preferably, the second reaction gas withdrawing line 17 to be supplied to the reaction tower 1) and the bottom liquid withdrawing line 14 are branched from the middle of the reaction liquid to draw the bottom liquid.
It is preferable that the column bottom liquid circulation lines 18 for circulation supply are connected to the middle part (preferably below the connection part of the line 17) of the above. A liquid transporting means (not shown) is installed between the branch point of the tower bottom liquid circulation line 18 and the reaction tower 1 in the tower bottom liquid extraction line 14, and a cooler is installed in the tower bottom liquid circulation line 18. 3 is preferably installed.

On the other hand, in the reactor 2, a nitric acid converting gas supply line 16 for supplying carbon monoxide or hydrogen is preferably provided in the lower part, and the column bottom liquid withdrawing line 14 is preferably provided in the middle part or the upper part. 2 Reaction gas extraction line 17
Is preferably connected to the top, and the drainage line 20 is preferably connected to the bottom. The reactor 2 is capable of carrying out a reaction of nitric acid and alkanol with carbon monoxide or hydrogen (a reaction of reacting nitric acid with carbon monoxide or hydrogen and alkanol to convert to alkyl nitrite; second reaction). It is not particularly limited as long as it is provided, and for example, a stirring tank, a packed tower, a trickle bed type and the like can be used, and a plurality of types or a multi-stage type may be used.

In the present invention, as described above, it is preferable to continuously perform the column bottom liquid circulation operation in which most of the outlet column bottom liquid is circulated to the intermediate portion of the reaction column 1. Then, a part of the outlet bottom liquid is continuously or intermittently introduced into the reactor 2 to react nitric acid and alkanol in the inlet bottom liquid with carbon monoxide or hydrogen in the presence of the platinum group metal catalyst. Preferably. At this time, it is preferable that the amount of the outlet bottom liquid introduced into the reactor 2 (the amount of the inlet bottom liquid) is adjusted so that the level of the bottom liquid of the reaction column 1 becomes constant.

The concentration of the alkanol in the bottom liquid of the introduction column is 15 to 60% by weight, more preferably 20 to 55% by weight because the alkanol concentration in the bottom liquid of the reaction column 1 is preferably controlled as described above. % Is preferable. The concentration of nitric acid is not particularly limited from the reaction itself of nitric acid and alkanol with carbon monoxide or hydrogen (for example, 60% by weight or less is sufficient), but the reaction is performed by circulating the bottom liquid. Since it is preferable to efficiently generate the alkyl nitrite in the tower 1, it is preferably 20% by weight or less, more preferably 1 to 20% by weight, and particularly preferably about 2 to 15% by weight. In addition, the bottom liquid also contains water by-produced in the first reaction and a small amount of alkyl nitrite.

In the second reaction, for example, the bottom liquid of the reaction tower 1 is continuously withdrawn through the bottom liquid withdrawing line 14 and a part of the liquid is continuously or intermittently introduced into the reactor 2.
Further, a platinum group metal catalyst is introduced and the solution is stirred under normal pressure or under pressure while carbon monoxide or hydrogen is circulated in the liquid, or carbon monoxide or hydrogen is introduced into the reactor 2. It is carried out by stirring the solution under pressure.
In addition, the reactor 2 is filled with a platinum group metal catalyst (as a fixed bed), and the tower bottom liquid extracted from the bottom of the reaction tower 1 (deriving tower bottom liquid) and carbon monoxide or hydrogen are countercurrently or cocurrently flowed. It can also be carried out by distributing it at. The reaction is carried out in the liquid phase, and a batch system or a continuous system is possible.

The carbon monoxide or hydrogen used in the second reaction may be as it is or diluted with an inert gas (such as nitrogen), and is 1 to 1 mol of nitric acid in the bottom liquid of the introduction column.
It is preferable to use -20 mol, more preferably 1.5-10 mol, and especially 2-5 mol. When the present invention is combined with a synthesis reaction using carbon monoxide and alkyl nitrite (production of dialkyl oxalate, etc.), nitric acid and alkanol in the bottom liquid of the introduction column may be reacted with carbon monoxide. preferable.

The temperature for reacting nitric acid and alkanol with carbon monoxide or hydrogen is 0 to 300 ° C., more preferably 20 to
It is preferably 100 ° C. The pressure of carbon monoxide or hydrogen is from normal pressure to 200 atm (about 20 MPa), further from normal pressure to 30 atm (about 3 MPa), particularly 3 to 10 atm.
m (about 0.3 MPa to about 1 MPa) is preferable. Further, the reaction can be carried out until the nitric acid concentration (residual nitric acid concentration) of the bottom liquid (introduced bottom liquid) introduced into the reactor 2 becomes 1% by weight or less, further 0.5% by weight or less. It is preferable in suppressing the recovery loss of the platinum group metal due to the elution or dissolution of the group metal or its compound.

The platinum group metal catalyst may be used by dissolving or suspending the platinum group metal or its compound as it is. Usually, in consideration of catalyst recovery, the platinum group metal is supported on a carrier to support a solid catalyst. (Fixed bed or suspension bed). In that case, the supported amount of the platinum group metal is preferably 0.01 to 20% by weight, and more preferably 0.1 to 15% by weight, in terms of metal, based on the carrier. Examples of the carrier include activated carbon and alumina, and activated carbon is preferable. The carrier may have any shape as long as it can be applied to a fixed bed or a suspension bed (powder, granule, pulverized product, etc.), but powder is preferable. The size of the carrier may be any size that can be applied to the fixed bed or the suspension bed. Examples of the platinum group metal include palladium, platinum, ruthenium, rhodium, and osmium, but palladium and platinum are preferable, and palladium is particularly preferable.

The platinum group metal catalyst is used in an amount of 0.1 in terms of metal with respect to the bottom liquid (introduced bottom liquid) introduced into the reactor 2.
0001 to 0.2% by weight, and further 0.0005 to 0.1
It is preferably in the range of 0.005 to 0.05% by weight. Specifically, for example, palladium metal supported on activated carbon at 10% by weight (10% by weight Pd / C).
When used, the amount used is 0.001 to 2% by weight, and more preferably 0.005 to 1% by metal, based on the bottom liquid of the introduction column.
It is preferably in the range of wt%, particularly 0.05 to 0.5 wt%.

The white metal metal catalyst is reacted as an alkanol solution or suspension from the middle of the bottom liquid outlet line 14 (between the branch point of the bottom liquid circulation line 18 and the reactor 2; not shown). It may be supplied to the reactor 2 or separately (not shown) and directly to the reactor 2. Further, the solid catalyst (fixed bed or suspension bed) may be charged in the reactor 2 in advance.

That is, in the present invention, the nitric acid concentration is 20% by weight.
In the liquid, in the presence of a solid catalyst (preferably a powder) in which a white metal metal or a compound thereof is supported on a carrier, the following (further 1 to 15% by weight, particularly 2 to 10% by weight) bottom liquid is used. The nitric acid and alkanol in the bottom liquid introduced into the reactor 2 are reacted with carbon monoxide or hydrogen until the nitric acid concentration (remaining nitric acid concentration) of 1 is less than 1% by weight (preferably less than 0.5% by weight). Is particularly preferred. As a result, the white metal metal or its compound eluted or dissolved in the liquid by contact with nitric acid can be re-loaded on the carrier, and the process can be performed in which the recovery loss of the platinum group metal can be suppressed to a very low level. From this viewpoint, in the case of continuous reaction, the reactor 2
It is preferable to use multiple tanks (two tanks or more). Further, in order to further suppress the recovery loss, it is also preferable to treat the waste liquid of the reactor 2 with an adsorbent such as activated carbon or alumina (for example, pass through an adsorbent-filled column).

The alkyl nitrite produced in the reactor 2 (second
As described above, the alkyl nitrite may be supplied to the area where the alkanol is flowing down in the reaction column 1 while being accompanied by carbon monoxide or hydrogen through the second reaction gas extraction line 17. Above all, it is preferable to supply the intermediate portion of the reaction tower 1, particularly above the connecting portion of the bottom liquid circulation line 18 (located in the intermediate portion of the reaction tower 1) which is the intermediate portion.

The present invention is very useful in synthetic reactions using carbon monoxide and alkyl nitrite (production of dialkyl oxalate, production of dialkyl carbonate, etc.). For example,
In general, the process as shown in FIG. 2 makes it possible to continuously produce dialkyl oxalate with high space-time yield and high selectivity while suppressing the loss of nitrogen content.

That is, in this process, carbon monoxide is supplied to the reactor 4 for producing dialkyl oxalate (hereinafter, also referred to as reactor 4) through the CO supply line 21, and alkyl nitrite-containing gas is circulated through the gas extraction line 13 ( In the presence of a platinum group metal-based catalyst, each was supplied from above by the first reaction gas extraction line 13) in the production of alkyl nitrite.
Carbon monoxide and alkyl nitrite are reacted (third reaction) to generate dialkyl oxalate (dialkyl oxalate production step), and then the reaction gas (third reaction gas; containing dialkyl oxalate) 3 The reaction gas withdrawal line 22 draws it out from the lower part, introduces it into the lower part of the absorption tower 5 (the absorption liquid consisting of alkanol flows down from the upper part with the absorption liquid supply line 23), and the produced dialkyl oxalate is condensed into the absorption liquid.・ Dissolve (absorption process)
The condensed liquid is extracted from the bottom of the absorption tower 5 through the absorption liquid extraction line 24, and then the condensed liquid is purified by distillation (distillation purification process; not shown) to obtain dialkyl oxalate.

In this process, the non-condensable gas in the absorption tower 5 (containing nitric oxide by-produced in the third reaction and containing carbon monoxide, alkanol vapor, inert gas, etc.) is non-condensed gas. An extraction line 12 (a raw material gas supply line 12 for the production of alkyl nitrite) is extracted from the top of the absorption tower 5, and oxygen is supplied to and mixed with this through an oxygen supply line 15, and the mixed gas (for the production of alkyl nitrite) is mixed. While supplying the raw material gas) to the lower part of the regeneration tower 1 (reaction tower 1 in the case of alkyl nitrite production), the alkanol is supplied through the alkanol supply line 11 so as to flow down from the upper part to the lower part of the regeneration tower. Gas-liquid contact reaction of nitric oxide, oxygen and alkanol to produce alkyl nitrite (first alkyl nitrite) (regenerated from nitric oxide)
(Regeneration step), the alkyl nitrite-containing gas is circulated through the gas extraction line 13 (first in the production of alkyl nitrite).
It includes a step for continuously producing dialkyl oxalate by supplying the reaction gas from the top of the regeneration tower 1 to the reactor 4 through a reaction gas extraction line 13). At this time,
In the process, the bottom liquid of the regeneration tower 1 is continuously withdrawn from the bottom by a bottom liquid extraction line 14, cooled, and circulated and supplied to an intermediate portion of the regeneration tower 1 by a bottom liquid circulation line 18, and An operation of purging a part of the circulating gas from the purge line 19 continuously or intermittently is included.

Further, in this process, a part of the bottom liquid extracted from the bottom of the regeneration tower 1 is continuously or intermittently reacted for nitric acid conversion so that the level of the bottom liquid of the regeneration tower 1 becomes constant. Introduced into the reactor 2, preferably in the middle or upper part, and in the presence of a platinum group metal catalyst, carbon monoxide is supplied to the reactor 2, preferably in the lower part, by a nitric acid conversion gas supply line 16, and the introduction bottom liquid The nitric acid and alkanol contained therein are reacted with carbon monoxide to generate alkyl nitrite (convert nitric acid into alkyl nitrite), and the alkyl nitrite (second alkyl nitrite) is discharged through the second reaction gas extraction line 17. It includes a step of supplying from the top of the reactor 2 to an intermediate part of the regeneration tower 1 (particularly above the connection part of the line 18 which is the intermediate part) and supplies it to the reactor 4 together with the circulating gas.
As a result, the nitric acid produced as a by-product in the regeneration tower 1 can be efficiently converted and recovered as an alkyl nitrite to be reused in the production of a dialkyl oxalate, and at the same time, the nitrogen content (nitric acid) generated by purging the bottom liquid can be increased. In addition to suppressing the loss of nitrogen, a simple method of replenishing nitric acid can be used as a means of compensating for the loss of nitrogen content (alkyl nitrite, nitric oxide) due to the purging of the circulating gas, and the replenishment amount is also reduced. be able to.

[0037]

EXAMPLES The present invention will be described in detail with reference to examples and comparative examples according to the process shown in FIG. The nitric acid was analyzed by ion chromatography, and the palladium was analyzed by I
It was analyzed by PC and the others by gas chromatography. Pd / C means a solid catalyst in which palladium metal (Pd) is supported on activated carbon (C).

Example 1 Reaction column 1 (packing tower; diagram having a diameter of 158 mm and a height of 1400 mm (having a Raschig ring packed bed of 10 mm from 50 mm below the top and 800 mm and a Raschig ring packed bed of 10 mm from 30 mm below this packed bed) 1)
From the line 12 of No. 1, a source gas having a composition of 15% by volume of nitric oxide, 20% by volume of carbon monoxide, 4.8% by volume of methanol and 60.2% by volume of nitrogen was added at 15.0 Nm ³ / h (pressure: 3.
2 kg / cm ² G; about 0.32 MPaG), and oxygen was supplied from line 15 at 0.5 Nm ³ / h. Further, a methanol solution at 20 ° C. was supplied from the line 11 at the top at 4.4 L / h. The pressure of the tower was 3.0 kg / cm ² G (about 0.3 MPa) with the valve attached to the line 13.
Adjusted to G).

The bottom liquid is withdrawn from the line 14 at the bottom of the tower and cooled by a pump attached thereto through a cooler to obtain 360
It was returned to the middle part of the tower at a flow rate of L / h. The cooler was adjusted by passing cooling water of 5 ° C. through the jacket side so that the bottom temperature was 40 ° C. When the composition of each part was measured at a stable point in this state, it was found from the line 13 at the top of the column that methyl nitrite was 1.94 Nm ³ / h and 0.25 Nm ^{3 of} nitric oxide.
/ H, methanol 0.73 Nm ³ / h, nitrogen 12.75
Nm ³ / h (methyl nitrite 12.4% by volume, nitric oxide 1.6% by volume, methanol 4.7% by volume, nitrogen 81.4
% Gas) was obtained with a flow rate of 15.67 Nm ³ / h. The water content was 0.05% by volume or less. Also,
The composition of the bottom liquid is 40.1% by weight of methanol and 52.2 of water.
% By weight, 7.4% by weight nitric acid, 0.4% by weight methyl nitrite
Then, it was extracted from the line 14 at a flow rate of 1.66 L / h.

Stirrer, gas supply nozzle (line 16),
10 L autoclave equipped with a liquid extraction nozzle (line 20; with a sintered metal filter) and a gas extraction nozzle (line 17; cooler installed in the middle of the pipe) connected to the middle part of the packed tower (position 850 mm from the top) (Reactor 2; SUS316, with liquid level gauge) was charged with 6 L of the bottom liquid (extracted liquid) and 12 g of 10 wt% Pd / C (manufactured by NE Chemcat; powder) and purged with carbon monoxide. Carbon monoxide 5 kg / cm ² G (about 0.5 M
PaG). Next, while extracting gas from the gas extraction nozzle so as to maintain this pressure, carbon monoxide was supplied from the gas supply nozzle at 1 Nm ³ / h, and the temperature was raised to 80 ° C. under stirring. Three hours after the temperature reached 80 ° C., the extracted liquid was introduced at a flow rate of 1.66 L / h. Approximately 1. liquid was extracted from the liquid extraction nozzle so that the temperature and surface of the reaction liquid in the autoclave would be constant.
It was withdrawn at a flow rate of 56 L / h. The composition of the extracted liquid is
Methanol was 39.8% by weight, water was 59.5% by weight, nitric acid was 0.2% by weight, methyl nitrite was 0.4% by weight, and the nitric acid conversion rate was 97.3%. The gas extracted from the autoclave had a composition of 3.36% by volume of methyl nitrite, 3.36% by volume of carbon dioxide, 80.67% by volume of carbon monoxide, 8.40% by volume of methanol, and 0.42% by volume of water. so,
It was introduced into the middle stage of the packed column at about 1.2 Nm ³ / h. The Pd concentration in the liquid extracted from the autoclave was 1.2 ppm on a weight basis.

Comparative Example 1 In Example 1, when the operation in the autoclave (reactor 2) (introduction of the bottom liquid, introduction of the raw material gas, conversion of nitric acid, etc.) was stopped, by-product nitric acid did not produce methyl nitrite at all. It could not be recovered, and the production rate of methyl nitrite could not be increased.

[0042]

INDUSTRIAL APPLICABILITY According to the present invention, in a method for producing an alkyl nitrite in which nitric oxide, oxygen and an alkanol are reacted to produce an alkyl nitrite, the production rate of the alkyl nitrite is increased to efficiently produce the alkyl nitrite. be able to. That is, conventionally, since a considerable amount of nitric acid is produced in the reaction of nitric oxide, oxygen and an alkanol, the nitrogen content is lost and the production rate of alkyl nitrite is reduced. Nitric acid can be efficiently converted into alkyl nitrite, and a very efficient alkyl nitrite production process can be constituted. Further, the present invention, because the recovery loss of the platinum group metal used as a catalyst when converting nitric acid to alkyl nitrite can be suppressed to a very low level,
It is possible to configure an efficient process. The present invention is
It is very useful in synthetic reactions using carbon monoxide and alkyl nitrite. For example, in the production of dialkyl oxalate, the loss of nitrogen content can be suppressed (nitric acid can be regenerated to alkyl nitrite and reused), and the loss of nitrogen content (nitric acid) due to purging of the bottom liquid and regeneration gas can be achieved. As a means for compensating for the loss of the nitrogen component (alkyl nitrite, nitric oxide) due to the purging of, the simple method of replenishing nitric acid can be used, and the replenishing amount can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic process diagram illustrating an alkyl nitrite production process.

FIG. 2 is a schematic process diagram illustrating a dialkyl oxalate manufacturing process.

[Explanation of symbols]

1: Reactor or regeneration tower for producing alkyl nitrite 2: Reactor for nitric acid conversion 3: Cooler 4: Reactor for producing dialkyl oxalate 5: Absorption tower 11: Alkanol supply line 12: Raw material gas supply line or non-condensing Gas extraction line 13: first reaction gas extraction line or circulation gas extraction line 14: tower bottom liquid extraction line 15: oxygen supply line 16: nitric acid conversion gas supply line 17: second reaction gas extraction line 18: tower bottom liquid circulation Line 19: Purge line 20: Waste liquid extraction line 21: CO supply line 22: Third reaction gas extraction line 23: Absorption liquid supply line 24: Absorption liquid extraction line

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Claims (7)

[Claims] 1. An alkanol is supplied to an upper part of a reaction tower for producing alkyl nitrite to flow from an upper part of the reaction tower to a lower part thereof, and nitric oxide and oxygen or a mixed gas thereof is supplied to a lower part of the reaction tower. While reacting nitric oxide, oxygen and alkanol to generate alkyl nitrite,
In the method for producing alkyl nitrite, (1) the bottom liquid is extracted from the bottom of the reaction column for producing alkyl nitrite and introduced into a reactor for nitric acid conversion, and carbon monoxide or hydrogen is supplied in the presence of a platinum group metal catalyst. Then, the nitric acid and alkanol in the bottom liquid of the tower are reacted with carbon monoxide or hydrogen to generate alkyl nitrite, and (2) the alkyl nitrite is flowed down by the alkanol of the reaction tower for producing alkyl nitrite. A method for producing alkyl nitrite, which comprises supplying the same to an area where 2. The process for producing an alkyl nitrite according to claim 1, wherein the alkyl nitrite produced in the reactor for converting nitric acid is fed to a zone from an intermediate portion to a lower portion of a reaction tower for producing an alkyl nitrite. 3. The method for producing an alkyl nitrite according to claim 1, wherein the platinum group metal catalyst is a solid catalyst in which a white metal metal or a compound thereof is supported on a carrier. 4. The method for producing an alkyl nitrite according to claim 1, wherein the platinum group metal is palladium or platinum. 5. The nitric acid concentration of the bottom liquid of the reaction tower for producing alkyl nitrite is 20% by weight or less, and the alkanol concentration is 15%.
The method for producing an alkyl nitrite according to claim 1 or 3, wherein the amount is -60% by weight. 6. The nitric acid and alkanol in the bottom liquid introduced into the reactor for converting nitric acid are reacted with carbon monoxide or hydrogen until the nitric acid concentration in the bottom liquid is 1% by weight or less. Alternatively, the method for producing an alkyl nitrite according to 3 above. 7. A column bottom liquid circulation operation in which the column bottom liquid extracted from the bottom of the reaction column for producing alkyl nitrite is introduced into a cooler to be cooled and the cooled column bottom liquid is circulated and fed to the intermediate part of the reaction column. And (a) the circulation supply amount of the bottom liquid is 50 to 300 times the supply amount of the alkanol to the reaction column, and (b) the supply amount of the alkanol to the reaction column and the circulation supply column to the middle part of the reaction column. The total amount of the alkanol in the bottom liquid is 20 to 150 times mol of the total supply amount of nitric oxide to the reaction tower, and (c)
The process for producing an alkyl nitrite according to claim 1, which is continuously carried out under the condition that the alkanol concentration in the bottom liquid is 15 to 60% by weight.