JPH02184656A - Method and reaction vessel for preparing alkyl nitrite - Google Patents

Abstract

PURPOSE: To obtain an alkyl nitrite useful as an additive for motor fuel, a stabilizer for vinyl compounds, a dizo reagent, etc., in a high yield by the reaction/rectification of a nitrogen oxide, a lower alcohol, and oxygen using a specified container.

CONSTITUTION: A nitrogen oxide, a lower alcohol, and oxygen are reacted at 50-200°C in the presence of a platinum group catalyst using a reactor having a reactor section and a rectification section to obtain alkyl nitrite. A scrubbing agent for washing water and nitric acid produced in the reactor is supplied above the rectification section, a gas reaction product flow containing an alkyl nitrite is taken out from the rectification section, and a liquid flow containing the scrubbing agent and water is taken out from the lower part of the reactor section.

COPYRIGHT: (C)1990,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a process for making alkyl nitrite, particularly methyl nitrite, and a compact reaction vessel in which the process is carried out.

DESCRIPTION OF RELATED ART Alkyl nitrites, i.e., esters of nitrous acid, are useful in a variety of fields, including as additives in automotive fuels, stabilizers for vinyl compounds such as quenching agents, diazotization reagents, and chemical synthesis reagents. I know. Methods for producing alkyl nitrites can be found in particular in U.S. Pat. . The method of producing alkyl nitrite (referred to herein as the "nitride process") may be more fully understood by reference to the following equation.

(1) 2 No + O, $ 2 No.

(2) No, +No, N, O.

(3) ROH+NtOs RO
NO+HONO(4) ROH+HONO-RONO
+H, 0 (5) N, 0. +H,02HONO(6)
2 No, Nto4(
7) ROH+NtO4RONO+HNO3(8)
NtO4+HtOHONO+HNO.

(wherein R represents a methyl or ethyl group).

The desired series of reactions to produce alkyl nitrite occurs through reactions (1) to (4). Integrating these reactions results in the following total product reaction:

(I) 2 ROH+ 2 No+! /20. -2
Since the water produced in the RONO+H,0 reaction (4) can react with dinitrogen dioxide (Nto8), reaction (5) occurs. Reaction producing alkyl nitrite and further water (4
), if sufficient alcohol is supplied to react with substantially all of the nitrous acid produced in reaction (5),
reaction (prisoner can tolerate)

Reactions (6) to (8) are undesirable because they result in the production of nitric acid, a compound that must subsequently be removed from the alkyl night product. Additionally, these reactions consume nitric oxide to produce undesirable nitric acid.

In order to reduce the formation of dinitrogen tetroxide (N, O,) by reaction (6), the gas phase concentration of NOl should be lower compared to the gas phase concentration of NO. In this way, Nto.

is preferentially generated instead of N, O, and so on. Maintaining a relatively high No to NO2 ratio by initially supplying a molar excess compared to 0, indicated by the stoichiometry of reaction (1), i.e. more than 94 moles of NO per mole of O2. Can be done. That is, to enhance the formation of alkyl nitrites such as methyl nitrite or ethyl nitrite, a molar excess, preferably substantially all of the 0. It is generally preferred to supply No in such an amount that it consumes .

The gas-phase production of alkyl nitrite (nitride process) using the general method described above can be combined with a comprehensive gas-phase process (nitride-oxalate process) which is a circulation operation (see, for example, U.S. Pat. No. 4,629,806). It is combined and associated with the gas phase production of dialkyl oxalate (oxalate process) from alkyl nitrite and monodispersed carbon in a unified production cycle so that Such processes are advantageous with regard to limited by-product formation, ease of operation, and production efficiency. Gas phase production of dialkyl oxalates is carried out by contacting carbon monoxide with alkyl nitrite in a carbonylation reaction zone in the presence of a solid catalyst. The main reaction is expressed by the following formula.

(II) 2 CO+ 2 RONO--1→ (in the formula, R represents a methyl or ethyl group).

The production of dialkyl oxalates is of particular importance to the chemical industry due to the wide variety of uses of these compounds. These diesters are used to make alkylene glycols such as ethylene glycol, which are commercially valuable chemicals that have applications in deicing fluids, antifreeze and hydraulic fluids, as well as in the production of alkyd resins, solvents and polyester fibers. Can serve as starting material. These diesters are also effective as intermediates for producing dyes, pharmaceuticals, and the like.

As is clear from the equation representing reaction (II), for every 1 mol of alkyl nitrite consumed, 1 mol of nitrogen oxide is produced. Recirculating the produced nitric oxide,
It can be used as a starting material for the preparation of alkyl nitrites according to reaction CI). In this way, the nitride-oxalate reaction cycle is completed. The dialkyl oxalate produced in the carbonylation reaction zone can be purified and recovered as a product,
Alternatively, it can be further reacted to produce ethylene glycol, for example by contacting with hydrogen in a hydrogenation reaction zone.

A number of performance criteria must be considered and met in order to have an effective method of producing alkyl nitrite.

First, the oxygen conversion is preferably as high as 100% without significantly adversely affecting other reactor performance characteristics.
should be close to. (i.e., the amount of oxygen exiting the alkyl nitrite reactor is preferably minimal), so that substantially all higher nitrogen oxides, i.e., oxides of nitrogen other than nitric oxide, are present in the alkyl nitrite reactor. It is also preferable that it be consumed.

Second, the conversion efficiency of nitrogen oxide to alkyl nitrite, i.e., the percentage of nitrogen oxide converted to the desired product alkyl nitrite, is increased in the alkyl nitrite reactor, and the nitric acid The formation of undesirable products such as

Substantially all of the water and nitric acid produced in the alkyl nitrite reactor can be removed from the gaseous product stream into the liquid tail stream by providing a scraping agent that scrubs the water and nitric acid. Preferably, in this way the amount of water and nitric acid present in the gaseous product stream from the alkyl nitrite reactor is minimized. Conversely, the amount of alkyl nitrite, the preferred product, present in the liquid tail stream from the alkyl nitrite reactor is minimized.

It is preferable to minimize the amount of scraping agent required to perform the separation necessary to meet the requirements discussed above, since the use of excess scraping agent material is uneconomical.

Finally, Reaction I is highly exothermic and requires heat removal from the alkyl nitrite reactor. DESCRIPTION OF THE INVENTION The present invention relates to a process for producing alkyl nitrite, including a reaction vessel, the process comprising: substantially complying with the performance standards set forth above and comprising: (a) nitrogen oxides, lower alcohols, and oxygen in a reaction zone where at least a portion of said nitrogen oxides, lower alcohols, and oxygen have reacted; (b) contacting a liquid scraping agent under conditions to produce alkyl nitrite, wherein said reaction zone includes at least two compartments, a reactor compartment and a rectification compartment; (b) a liquid scraping agent in an upper portion of said rectification compartment; (c) withdrawing a gaseous reaction product stream comprising alkyl nitrite from said rectifying section; (d) withdrawing a liquid stream comprising a scraping agent and water from the lower portion of said reactor section; In this case, the reactor section provides sufficient intimate gas-liquid contact and cooling to increase the conversion of nitrogen oxides to alkyl nitrite, and the rectification section provides sufficient intimate gas-liquid contact and cooling to increase the conversion of oxygen. and sufficient rectifying capacity to reduce the amount of water and nitric acid in the gaseous reaction products and the amount of alkyl nitrite in the liquid stream.

The present invention also relates to a ninth preferred reaction vessel for producing alkyl nitrite by contacting nitrogen oxide, a lower alcohol, and oxygen.

The reaction vessel includes (a) a lower packed bed section, (b) an upper rectifying section, (c) means for supplying liquid scraping agent to the upper rectifying section, and (d) a flow of gas from the upper rectifying section. and (e) means for removing a stream of liquid bottoms from the lower packed bed section. The lower packed bed section provides intimate gas-liquid contact sufficient to increase the conversion of nitrogen oxides to alkyl nitrite;
Moreover, the upper rectifying section provides sufficient vapor residence time to increase the conversion of oxygen and reduce the amount of water and nitric acid in the gaseous reaction product stream and the amount of alkyl nitrite in the liquid bottoms stream. 1 and a sufficient rectification window.

The invention will be more easily understood by referring to the drawings. First, referring to FIG. 1, alkyl nitrite is produced in a dialkyl nitrite reactor or alkyl nitrite regeneration column 1o (ANRC) by contacting nitrogen oxide with oxygen in the presence of a lower alcohol. In the terminology of the present invention, lower alcohols include C8 to C4 alcohols, preferably selected from methanol, ethanol and mixtures thereof. Methanol is most preferred and the present invention will therefore be described using methanol as the lower alcohol and methyl nitrite as the product.

Typically supplemental nitric oxide (solid line 31 and/or dotted line 32)
Recycled nitric oxide supplemented by the nitric oxide is supplied to the ANRC via line 20. Oxygen is passed through line 21 to AN
Supply to RC. The flow of nitrogen oxide and the flow of oxygen are AN
Preferably, it is fed to the bottom of the RC. Liquid methanol is fed to the top of the -CANRC via line 22.

As detailed below, methanol advantageously acts as both a reactant and a scraping agent.

As mentioned above, the molar ratio of nitric oxide to nitrogen in the ANRC is preferably greater than or equal to 4:1, typically ranging from slightly above 4:1 to 5:1t. The actual flow rates of the various reactants to the ANRC vary widely depending on the design and size of the ANRC, with methanol to oxygen molar ratios typically ranging from about 4:1 to about 12:1 or more.

Preferably, the production of methyl nitrite is carried out in a continuous manner at a temperature high enough to keep substantially all of the nitrogen oxides and methyl nitrite and only some of the lower alcohol (methanol) in vapor form. ANR
The temperature within C typically ranges from about 10°C to about 150°C, preferably from about 20°C to about 130°C, and most preferably from about 30°C to about 110°C.

Pressure within the ANRC typically ranges from about atmospheric pressure to about 100p
siat, preferably from about 20 psia to about 60 psia
It is in the range up to sia. Subatmospheric pressures, ie, 14.7 psia or less, can be used if desired.

The gas hourly space velocity in ANRC is typically about 120
from 7 o'clock to about 36,000/hour, preferably about 180
It ranges from 0/hour to approximately 36,0007 hours. Lower or higher space velocities can be employed depending on the temperature, pressure, reactant molar ratio, gas diluent and feed rate employed, as long as sufficient reaction time is allowed. Additionally, the design and geometry of the reactor may also have an effect.

Methyl nitrite production methods generally do not require the use of catalysts. However, if desired a suitable catalyst and/or
Alternatively, a catalyst support can also be used.

Although mixing of the various feed streams fed to the reaction zone is generally achieved by perturbing conditions present at the point of introduction of the streams, mixing can be induced by other means as well.

The reactants supplied to ANRC have the following reaction formula (I): (D
2NO+'J//, 02+2ROH→2 RONO
Preference is given to reacting according to + H,0, where R is methyl.

Unfortunately, some of the nitrogen oxides are also converted to nitric acid via the aforementioned side reactions. Thus, the material exiting the ANRC typically consists of nitrogen oxides, carbon oxides, oxygen, and methyl nitrite, as well as small amounts of nitric acid, water, and methanol. Substantially all of the nitrogen oxides, unreacted oxygen and methyl nitrite products exiting the ANRC are removed in the gas phase from the top of the ANRC via line 23.

Although some of the methanol fed to the ANRC constitutes the reactant as mentioned above, some of it remains in the liquid phase as a scraping agent to clean up substantially all of the nitric acid and water in the ANRC. . That is, substantially all of the nitric acid and water exiting the ANRC is removed into the liquid methanol-containing light 24.

Preferably, the liquid methanol-containing stream is withdrawn from the bottom of the ANRC. AN via methanol-containing stream 24
All the water that does not flow out from RC is routed to A via pipe 23.
It is extracted from the top of the NRC in a gaseous state. A small portion of the methanol exiting the ANRC is also removed in gas phase from the top of the ANRC via W line 23.

The liquid stream removed from the ANRC via line 24 may be purified by distillation, extraction, etc. to reduce its water and nitric acid content. The purified product can then be recycled as lower alcohol (ie methanol).

In the integrated alkyl nitrite dialkyl oxalate process shown in FIG.
It is mixed, preferably in the gas phase, with carbon monoxide fed via line 26 and then fed to the carbonylation reaction zone or oxalate reactor 11. Preferably, all of the material entering the oxalate reactor is substantially entirely in the gas phase. Methyl nitrite and carbon monoxide are brought into contact with each other in the presence of a catalyst in the reactor 11, and the reaction formula (■): (n) 2 Co + 2 RONO-1→C0OR
+2N.

Dimethyl oxalate and nitric oxide are produced according to I 0OR where R is lower argyl, eg, methyl for the purposes of this description.

It may be preferable to carry out the carbonylation reaction in the presence of an inert gas diluent such as nitrogen or carbon dioxide.

Carbon dioxide is preferred as it provides a higher heat capacity compared to nitrogen.

Such gaseous diluents contain from about 0 to about 99% of the gaseous feed.
Capacity% can be configured. Typically the concentration of the gaseous diluent ranges from about 1 to about 90% by volume.

The appropriate concentration of carbon monoxide in the reaction mixture depends on the alkyl nitrite employed and its concentration, the catalyst used, the concentration of the inert gas diluent, if a diluent is used, and the process conditions selected. related to. Generally, the higher the concentration of alkyl nitrite, the faster the carbonylation reaction. The volume ratio of alkyl nitrite to carbon oxide is typically from about 0.05 to about 3.
．． 0, preferably in the range of about 0.2 to about 1.0. Usually a molar excess of carbon monoxide is used.

The carbonylation reaction is conducted under conditions that substantially avoid the formation of a liquid phase in the carbonylation reaction zone 11. These conditions may vary depending on the particular alkyl nitrite and its concentration. The carbonylation reaction is generally carried out at a temperature of about 50 to about 200°C, preferably about 75 to about 160°C, most preferably about 120 to about 15°C.
It is carried out at a temperature of 0°C. The carbonylation reaction pressure is generally from about atmospheric pressure to about 220 psia, more preferably from about atmospheric pressure to about 100 psia, and most preferably from about 15 psia to about 60 psia. Pressures below atmospheric pressure can be employed if desired.

The gas hourly space velocity for the carbonylation reactor is generally greater than about 120/hour, preferably from about 360/hour to about 72,000/hour.

Preferably, carbonylation reaction zone 11 does not contain water. Although very small amounts of water in the reaction zone are acceptable, it is preferred to remove substantially all of the water produced during ANRC before introducing the ANRC product stream into carbonylation reaction zone 11. Preferably, the amount of water in the oxalate production reaction zone is about 5% by volume or less.

Although it is preferred that the carbonylation reaction is carried out in a continuous manner in a series of elongated tubular zones, alternative zone geometries and designs may be employed. The materials of construction should be such that they are inert to the reactants and products, yet able to withstand the reaction temperatures and pressures. Due to the exothermic nature of the carbonylation reaction, carbonylation reaction zone 11 may be equipped with internal or external heat exchange equipment for temperature control. Mixing in carbonylation reaction zone 11 is generally achieved by perturbation at the point of entry for the various gaseous components. Other mixing mechanisms may be employed as well.

The carbonylation reaction zone 11 is preferably filled with a solid catalyst based on a platinum group metal. A preferred platinum group catalyst material is palladium. However, platinum, rhodium,
Ruthenium and iridium are also useful. It is also possible to use salts of these metals, such as nitrates, sulfates, phosphates, halides, acetates, oxalates, or benzoates. These materials can be supported on supports such as activated carbon, alumina, silica, silica-alumina, silica, pumice, magnesia, or zeolite. In general, the amount of platinum group metal will generally range from about 0.01 to about 10%, preferably from about 0.2 to about 2%, by weight of the carrier. Generally, the solid catalyst can be supplied as a fixed bed or as a fluidized bed.

It has been found that when a palladium catalyst is used, nitrite and nitric acid accelerate the rate of catalyst deactivation. It is therefore preferred that substantially all of the nitrite produced in or supplied to the ANRC is consumed in the ANRC. Furthermore, since oxygen has similar deleterious effects on catalysts such as those described above, it is important to minimize the amount of unconsumed oxygen in the alkyl nitrite product recovered from ANRC.

Carbonylation reaction effluent 28t containing dimethyl oxalate and nitrogen oxide is substantially completely removed from carbonylation reaction zone 11 in the gas phase and preferably fed to oxalate scrubber 12 . A liquid scraping agent fed to the oxalate scrubber 12 via line O 9 cleans substantially all of the dimethyl oxalate from the carbonylation reaction effluent.
The scraping agent is preferably the same substance as the scraping agent in ANRC, namely methanol. Substantially all, i.e., 95% or more, of the nitrogen oxides contained in the carbonylation reaction effluent 28, which removes liquid bottoms including the scraping agent and dimethyl oxalate from the oxalate scrubber 12;
Preferably 99% or more is removed from the oxalate scrubber 12 into gaseous overhead stream 20 and then preferably recycled to the ANRC, thereby completing the nitride-oxalate cycle.

Typically, the nitrogen oxides recovered from the oxalate scrubber are
It must be supplemented by make-up nitric oxide supplied to the ANRC as a separate stream via line 31 or introduced into the recycled nitric oxide stream 20 via dotted line 32.

The ANRC according to the invention may conveniently consist of an elongated tubular reaction zone, preferably a column, although other zone geometries may be employed. The column includes at least two sections: an upper rectification section and a lower reactor section. The lower reactor section preferably includes a packed bed and the upper rectification section preferably includes a series of spaced apart distillation trays. The materials of construction should be inert to the reactants and products under the reaction conditions and should be able to withstand the temperatures and pressures encountered.

Preferably, nitrogen oxide and oxygen in the gas phase have an ANR
C is fed into the lower reactor section, preferably below the packing. Oxygen is consumed by the oxidation of nitrogen oxide (reaction formula (I) above): (D 2NO+0□
2 Noz This reaction is relatively slow and appears to occur primarily in the gas phase, proceeding in what can be described as a vapor pocket within the ANRC. In the lower reactor section, the vapor pockets are disposed in a continuous liquid phase in the packed bed and consist primarily of gas bubbles that migrate upwardly through the liquid phase. In the upper rectification or distillation section, the vapor pocket is mainly between the trays, i.e. the liquid bubbles on the trays (1quid f
roth) and below the upper tray.

The 2fl reactions occurring in the vapor pocket are reactions (2) and (6) discussed above: (2) NO+ No, □N20° (6) 2
N(), Hill=9N,O.

The reaction between N, O, produced in reaction (2) and methanol in reaction (3) is very rapid, and
It appears to proceed in a liquid phase called a liquid pocket within the NRC. In the reactor section described below, the liquid pockets are disposed within a packed bed and generally consist primarily of a substantially continuous liquid phase moving downwardly through the packed bed.

In the upper rectification section, the liquid pocket consists primarily of liquid bubbles on each distillation tray.

It appears that the N,03 produced in reaction (2) can also react with oxygen in the gas phase. Such N, 0. The further reaction of nitric acid precursor (N,05
+H,O←2HNO3) Totally produced, t, converts the 9-catch nitrogen oxide to alkyl nitrite, reducing the efficiency of the system. Therefore, in order to increase the conversion efficiency of nitrogen oxide to alkyl nitrite, the NtO produced in reaction (2) should be converted to lower alcohol produced in reaction (3) relatively soon after. It is preferable to force the reaction. NtO.

The reaction between the gas and the lower alcohol appears to occur primarily when the gas and liquid come into contact.

Reaction (6) also reduces the efficiency of the system in converting nitrogen oxides to alkyl nitrite and generally reduces the efficiency of reaction (7).
and (8) resulting in the formation of undesirable nitric acid. Reaction (6) appears to occur in the gas phase. In order to minimize the production of nitric acid, the NO
Preferably, alkyl nitrite, ie methyl nitrite, is produced by reaction with O and then immediately in the liquid phase with a lower alcohol, such as methanol. It has been found that the above considerations can be met by a reactor section, such as a packed bed reactor, which provides intimate gas-liquid contact and a relatively low gas hold-up axis. In the absence of significant vapor pockets that may be present in packed bed designs, it is selective to use a molar excess of NO over oxygen associated with intimate contact between the gas and liquid alcohol phases. to promote reactions (1) to (4), and to promote reactions (5) to (8).
). The desired product, alkyl nitrite, is therefore produced in place of nitric acid. As an alternative to a packed bed design, the reactor compartment can also be a spray compartment.

With the above background, preferred ANRC container designs will now be described in further detail. ANRC design requirements vary significantly from the bottom of the column to the top.

Nitric acid and oxygen in a stoichiometric excess of nitrogen oxide,
i.e. fed to the bottom of the ANRC in a molar ratio such that the molar ratio of NO:0□ is present in an amount greater than or equal to 4:1. As long as a sufficient molar excess of nitric oxide is used, the oxygen concentration will be higher at the bottom of the ANRC compared to the rest of the ANRC, where oxygen has been at least partially depleted by reaction with the nitric oxide. be. In other words, if an initial excess of oxygen is used, the nitric oxide/oxygen molar ratio will generally be lower than the ANRC at the bottom of the ANRC.
It is lower than other places where Noiharu occurs. As a result, reaction (1)
The speed of A is generally faster than anywhere else in the ANRC.
High at the bottom of the NRC. Because of the high production rate of No., the rate of reaction (2) is also lower than that of A compared to the rest of the column.
Larger at the bottom of the NPC. To maximize the conversion efficiency of nitrogen oxide to alkyl nitrite, N2O3
The contact between NzO+ (formed via reaction (2)) and lower alcohols, such as methanol, should be maximized in the bottom compartment of the ANRC, where the formation of NzO+ is particularly rapid. This is done by bringing the vapor and liquid into intimate contact in the bottom compartment. Therefore, packing that generally results in intimate contact between vapor and liquid
takes place in the bottom compartment of the ANRC.

Generally some oxygen passes through the unconsumed fill compartment and then enters the upper compartment. As indicated above, it is desirable that there be substantially no oxygen in the methyl nitrite product delivered to the oxalate reactor. ANRC
In order to maximize the consumption of oxygen within the ANRC and achieve this goal, it is desirable to provide a means for consuming substantially all of the oxygen that enters the upper compartment of the ANRC. Generally, higher concentrations in the column are measured as the concentration of oxygen becomes progressively lower. For this reason, the speed of reaction (1) is required in the upper rectifying section of the column to complete the consumption of oxygen without significantly adversely affecting the overall conversion efficiency of nitrogen oxide to methyl nitrite in the ANRC. A relatively large gas phase residence time should be provided along with a relatively low degree of gas-liquid contact. By providing a relatively long gas phase residence time in the upper rectifying section of the ANRC, substantially all of the oxygen entering the upper rectifying section can be consumed, typically 99% or more. Sufficient gas phase residence time can easily be provided in the upper rectification section consisting of a trayed distillation section.

For the reasons discussed in the background section above, the ANRC
the amount of water and nitric acid contained in the steam product of A
Preferably, the amount of methyl nitrite in the NRC liquid bottoms stream is minimized. Temperature and pressure within the ANRC are maintained such that proper separation of the compounds occurs within the ANRC. To best achieve this result, a scraping agent is introduced in the upper part of the rectification compartment, preferably above the top tray, to aid in separation. Preferably, the methanol supplied as reactant also acts as a scraping agent. Generally, the more scraping agent used, the better the rectification obtained. The amount of scraping agent required to perform a separation of
It can be reduced by providing more trays. Therefore, there is an economic optimization behind using large amounts of scraping agent and having more trays in the ANRC.

Substantially all of the oxygen supplied to the ANRC, i.e., 99% or more, and substantially all of the nitrogen oxides other than nitrogen oxides, i.e., 99% or more, are supplied to the ANRC by providing a moderate gas phase residence time. consumed in

Finally, as discussed in the Background of the Invention section, the heat of reaction must be effectively removed from the ANRC. Generally, about 90% or more of the total heat generated within the ANRC is generated in the lower packed bed section, typically 95% or more. Heat removal is preferably achieved by recycling a side stream of liquid from the lower reaction section through a heat exchanger.

Preferably heat is also removed in the lower part of the upper rectification section of the ANRC, this can also be achieved by providing additional heat exchange means similar to those described above. It can be removed, passed through a cooler, and then returned to the higher trays of the ANRC.

A preferred ANRC according to the present invention will be explained with reference to FIG. In FIG. 2, the lower packed bed reactor section 40 has approximately 20
Vertical foot infills can be included. The upper rectification section 41 has a tray spacing of about 3 with a tray spacing of about 2 feet.
Contains 6 trays. Although it is possible to use a packing in the upper rectification section 41, there may be problems with the proper liquid distribution necessary to ensure sufficient rectification. However, even without such problems, the added cost of the filling is not justified. This is because the gas stagnation (hol) is quite large.
d-up) is not difficult to solve and is actually desirable to achieve oxygen consumption. A friendly tray is preferred.

In a preferred embodiment, the lower reactor section and the upper rectification section are provided as one segmented column grain.

In either case, a means is provided for directing gas/vapor from the packed bed reactor section directly into the upper rectification section and liquid from the rectification section directly into the packed bed reactor section.

Recirculating nitric oxide, make-up nitric oxide and oxygen are carried below the charge via lines 42, 43 and 44, respectively.
Feed the bottom of the ANRC at the bottom of the reactor section.

Liquid methanol is supplied via line 45 to a location on the top tray at the top of the rectification section. A liquid stream 46 containing methanol, nitrogen oxide and water is withdrawn from the lower part of the reactor section, below the packing. A portion of the liquid stream 46 is cooled in a heat exchanger 47 and then passed via line 48 to the AN at a location directly above the packed bed section.
Return to RC. In addition, the liquid stream withdrawn from the bottom tray in the ANRC is passed through a second heat exchanger 50 and returned to the AN via line 51 on the 23rd tray from the bottom of the upper rectifying section. . An overhead stream 52 containing the product methyl nitrite is removed from the top of the ANRC.

The present invention provides (1) substantially complete conversion of oxygen, i.e., at least 95%, preferably 99% or more, most preferably 99.5% or more; (2) higher nitrogen oxides; substantially complete conversion of and (
3) Methyl nitrite can be produced in an efficient manner with a high conversion efficiency of nitrogen oxide to methyl nitrite, i.e. at least 95%, preferably 99% or more. In addition, ANR
All nitric acid and water produced at C are removed via the liquid tail stream, while the gaseous overhead stream containing methyl nitrite substantially contains these materials. do not.

The present invention can be more easily understood by referring to the following examples. The examples are given by way of illustration and are not intended to limit the invention.

EXAMPLE This example describes a preferred AN designed in accordance with the present invention.
The results of computer simulation of RC are shown.

ANRC is'! Designed according to the design of J2 diagram,
A lower photonic bed reactor section with 20 vertical feet of packing and 8 theoretic equivalent separation stages.
l equilibrium 5eparation
an upper rectification section (69 feet high) with stages). Actually the lower part 43 of the upper rectifying section
Feet contribute only one equivalent step to the rectification. This is because, as shown in FIG. 2, the side cooling loop (1oop) summarizes this part of the ANRC.

In this simulation, the ANRC operated at approximately 5 atmospheres and 50°C. No and 0. was fed to the bottom of the packed bed section in an approximately 5:10 molar ratio while substantially pure methanol was introduced to the top of the rectification section. This procedure is supplied to ANRC & NO 99%
more than 20% is converted to methyl nitrite, less than 10 ppm of water, and only about 20 ppm of water, and 50 ppm of water.
An overhead distillate containing ppm of oxygen was produced. This indicates an oxygen conversion of about 99.7% in ANRC. The liquid flow withdrawn from the bottom of the reactor compartment is approximately 1
It contains 3 mole % methanol, about 1 mole % and only about 0.1 mole %, with the balance being water.

[Brief explanation of the drawing]

FIG. 1 is a flow diagram of the alkyl nitrite-dialkyl oxalate production cycle. FIG. 2 is a schematic diagram of a preferred alkyl nitrite reactor according to the present invention. FIG.2

Claims (1)

[Claims] 1. (a) bringing nitrogen oxide, a lower alcohol, and oxygen into contact in a reaction zone under conditions such that at least a portion of the nitrogen oxide, lower alcohol, and oxygen react to produce alkyl nitrite; wherein said reaction zone includes at least two sections, namely a reactor section and a rectification section; (b) a liquid scraping agent is provided to an upper portion of said rectification section; (c) an alkyl nitrite is included. (d) a stream of liquid containing a scraping agent and water is removed from the reactor section; the rectification section provides sufficient intimate gas-liquid contact and cooling to increase the conversion of oxygen, and the rectifying section has sufficient vapor residence time to increase the conversion of oxygen and and a rectifying capacity sufficient to reduce the amount of water and nitric acid in the liquid stream and the amount of alkyl nitrite in the liquid stream. 2. The method according to claim 1, wherein the alkyl nitrite is methyl nitrite, the lower alcohol is methanol, and the liquid scraping agent is methanol. 3. The method of claim 1, wherein the alkyl nitrite is ethyl nitrite, the lower alcohol is ethanol, and the liquid scraping agent is ethanol. 4. The method of claim 1, wherein heat is removed from the reaction zone by removing a liquid side stream from the reactor compartment, cooling the liquid side stream, and then returning the liquid side stream to the reaction zone. 5. a rectifying section including a series of spaced trays, removing a second liquid side stream from the lowest tray of said rectifying section, cooling said second liquid side stream, and then discharging said side stream; 5. The method of claim 4, wherein additional heat is removed from the reaction zone by returning to the rectification section at a location in the rectification section that is higher than the bottom tray. 6. The conversion rate of oxygen in the reaction vessel is at least 95%.
3. The method of claim 2, wherein the conversion of nitrogen oxide to methyl nitrite is at least 95%. 7. The method according to claim 2, wherein the conversion rate of oxygen in the reaction vessel is 99% or more, and the conversion rate of nitrogen oxide to methyl nitrite is 99% or more. 8. (a) a lower packed bed section; (b) an upper rectifying section; (c) means for supplying a liquid scraping agent to said upper rectifying section; (d) a flow of gaseous reaction products from said upper rectifying section. (e) means for removing a stream of liquid from said lower packed bed section, wherein said lower packed bed section is adapted to increase the conversion of nitrogen oxides to alkyl nitrite. The upper rectifying section provides sufficient intimate gas-liquid contact, yet the upper rectifying section has sufficient vapor residence time to increase the conversion of oxygen and the amount of water and nitric acid in the gaseous reaction product stream and in the liquid stream. A reaction vessel for producing alkyl nitrite by contacting nitrogen oxide, a lower alcohol, and oxygen, the reaction vessel comprising: providing a rectification capacity sufficient to reduce the amount of alkyl nitrite. 9. The reaction vessel of claim 8, wherein the reaction vessel further includes means for removing heat from said reaction vessel. 10. Claim 9, wherein the means for removing heat from the reaction vessel includes means for removing a liquid side stream from a lower packed bed section, cooling said liquid side stream, and then returning it to said reaction vessel.
Reaction vessel as described. 11. Claim 11, wherein the means for removing heat from the reaction vessel includes means for removing a liquid side stream from an upper rectifying section, cooling a second liquid side stream, and then returning it to an elevated location in said upper rectifying section. Item 10. Reaction container according to item 10. 12. The reaction vessel of claim 8, wherein the upper rectification section includes multiple spaced distillation trays. 13. The reaction vessel of claim 12, wherein the upper rectification section includes about 36 trays and the lower packed bed section includes about 20 vertical feet of packing. 14. contacting nitrogen oxide, methanol and oxygen in a reaction zone, said reaction zone comprising at least two sections, a lower packed bed section and an upper rectification section having spaced apart distillation trays; In this case; (1) the oxygen conversion rate is 99% or more, and (2) the efficiency of nitrogen oxide to alkyl nitrite is 99%.
% or more.