JPS6324491B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing methyl chloride and methylamines by reacting methanol and ammonium chloride in the gas phase. Conventionally, well-known methods for producing methyl chloride include chlorination of methane with chlorine, oxychlorination using hydrogen chloride and oxygen, and a reaction between methanol and hydrogen chloride. Among these,
In particular, when only methyl chloride is to be produced, methanol is esterified with hydrogen chloride, but the hydrogen chloride source used in this reaction is not only synthetic hydrochloric acid synthesized from hydrogen and chlorine, but also hydrocarbon chlorine. Although hydrochloric acid produced as a by-product in various organic synthesis reactions such as chemical reactions (hereinafter referred to as by-product hydrochloric acid) can be used, a method using inexpensive by-product hydrochloric acid is generally practiced industrially. However, since securing a quantity of by-product hydrochloric acid at low cost depends on locational conditions, a new, more economical production method is desired. On the other hand, apart from by-product hydrochloric acid, large amounts of ammonium chloride are produced using the ammonia-soda method, but this is constrained by demand for fertilizers, etc., forcing a reduction in production, which in turn hinders the rationalization of the ammonia-soda method. is causing Against this background, various methods have been proposed for recovering chlorine or hydrochloric acid from ammonium chloride, but none of them are satisfactory because the reactions or operations are complicated. Various methods have been proposed in which ammonium chloride is used as a chlorinating agent instead of hydrogen chloride in the oxychlorination reaction of hydrocarbons. It is necessary to increase the amount of water, which is not satisfactory under such conditions, which leads to combustion of ammonia and decomposition of chlorinated hydrocarbons. The present inventors have conducted intensive studies to provide an industrially advantageous method for utilizing ammonium chloride, which has various drawbacks as described above. We have discovered a method for producing methyl chloride and methylamine in high yield by effectively utilizing chlorine and ammonia components through reaction. Regarding the method for producing methyl chloride from ammonium chloride and methanol by a catalytic reaction, U.S. Pat.
No. 2755316 describes the production of methylamines, the amount thereof, etc., and the separation of the products from the reaction product gas is carried out by washing the gas with water and treating it as an insoluble gas component. It only describes a method for separating and obtaining methyl chloride. However, according to the research of the present inventors, the gas phase catalytic reaction between ammonium chloride and methanol causes
Methylamines are produced together with methyl chloride, but the production ratio can be varied over a wide range by changing reaction conditions such as the supply ratio of ammonium chloride and methanol. When attempting to separate and obtain effective products, when the method of washing the reaction product gas with water as described in the above-mentioned U.S. patent specification is carried out, methylamines are also separated as unreacted chlorides as water-soluble components. It became clear that it was difficult to obtain free methylamines because they reacted quickly with ammonium to easily produce methylamine hydrochloride, and as a result of further research, we arrived at the present invention. be. Therefore, the present invention allows methanol and ammonium chloride to undergo a gas phase contact reaction, and selectively separates and collects unreacted ammonium chloride from the resulting reaction product gas containing methyl chloride and methylamines using a dry collection method. After that, the residual gas is washed with water, and methylamines are separated and collected as water-soluble components and methyl chloride as insoluble gas components. In the present invention, there are no particular restrictions on the ammonium chloride used, and various kinds of ammonium chloride can be used, such as naturally occurring ones, those obtained by the ammonia-soda method, and those obtained by metathesis of ammonium sulfate and common salt. Further, ammonium chloride can be supplied as a solid, or in the form of an aqueous solution or slurry. In the method of the present invention, either a fixed bed method or a fluidized bed method may be used to bring the raw material gas into contact with the catalyst, but the fluidized bed method is advantageous when considering the method of supplying ammonium chloride or the method of sublimation. be. As catalysts, various solid acid catalysts such as activated alumina and silica/alumina, which are conventionally used as catalysts for synthesizing methyl chloride from methanol and hydrogen chloride and methylamine from methanol and ammonia, can be used. It can also be used by impregnating it with metal chlorides, metal sulfates, alkali metal oxides, etc. Regarding the supply ratio of raw material ammonium chloride and methanol, as the molar ratio of ammonium chloride to methanol increases, the proportion of methyl chloride produced increases, and on the other hand, as the molar ratio decreases, the proportion of methylamines produced increases; If the molar ratio is too small, the conversion rate of ammonium chloride or methanol will decrease and it will become uneconomical in terms of recovering and recycling unreacted materials. Preferably. It is also possible to increase the production ratio of methylamines by recycling by-product ammonia to the reaction system, in which case the total molar ratio of chlorine and ammonia to methanol in the raw material (ammonium chloride mole) It is preferable to select a range of 0.8 to 2.0 (number×2+number of moles of ammonia/number of moles of methanol). In the process of the invention, the space velocity of the reactants fed to the reactor can vary over a fairly wide range, but typically
100 to 3000 hr ^-1 , preferably 200 to 2000 hr ^-1 . When the reactor is a fixed tank type, ammonium chloride is supplied to the reactor using a methanol evaporator or a non-reactive fluidized bed such as silica sand to gasify the reactant. However, if the reactor is of a fluidized bed type, it is possible to directly feed methanol in a liquid state or ammonium chloride in a solid state to the reactor. It is known that a considerable proportion of vaporized ammonium chloride dissociates into hydrogen chloride and ammonium under such conditions, but as the reaction progresses, the dissociation is accelerated. In the method of the present invention, the reaction temperature is 200
A temperature range of 600° C. to 600° C., preferably 300 to 500° C. is suitable; temperatures below this range do not provide a substantial reaction rate, and temperatures above this range result in increased decomposition reactions. The reaction pressure is not particularly limited and may be normal pressure, increased pressure, or reduced pressure, but it is usually convenient to operate under normal pressure or slightly increased pressure. Thus, by keeping the ammonium chloride partial pressure in the reaction system below its saturated vapor pressure, it is possible to effectively prevent ammonium chloride from solidifying. Note that the raw material gas in this reaction usually consists of methanol and ammonium chloride, but it may be diluted with an inert gas or water vapor may be present as necessary. Furthermore, as described above, the recovered by-product ammonia can be recycled in order to increase the production rate of methylamines. The reaction product gas obtained by reacting ammonium chloride and methanol under the above conditions is:
In addition to methylene chloride and methylamines, it contains unreacted ammonium chloride, unreacted methanol, by-product ammonia, by-product water, etc. First, this reaction product gas is cooled in a dry collector to remove unreacted ammonium chloride. Selectively collect. As the dry collection method referred to in the present invention, techniques known in this field can be widely applied, such as a method for dry collection of sublimable substances such as phthalic anhydride. For example, the reaction product gas is passed through several air cooling chambers to precipitate ammonium chloride as a solid, and then collected using a cyclone or back filter, or cooled by flowing a cooling medium, such as using a switch condenser. The ammonium chloride is precipitated as a solid on a number of cooled surfaces such as a finch tube, and then a switching operation is performed, and a heating medium is flowed inside the finch tube to sublimate the precipitated ammonium chloride, or a solvent such as water is sprayed or rinsed off to remove it. This method is effective. It is also possible to use a method in which the reaction product gas is blown into a fluidized bed, deposited on the cooled surfaces of fluidized particles, and recovered. In this case, in addition to ammonium chloride particles, inert particles such as glass, silica, ceramics, alumina, and stainless steel are used as fluidized particles. ammonium chloride recovery;
A range of 20μ to 3mm is appropriate. Particles coated with ammonium chloride are extracted from the fluidized bed, and the ammonium chloride is recovered by injection into a fixed wall or by heating, and the particles are circulated within the fluidized bed. The ammonium chloride collection efficiency in this dry collection method is influenced by the collection conditions such as gas residence time, gas linear velocity, collection temperature, and partial pressure of ammonium chloride, as well as the internal structure of the collector. However, it is also effective to use various collection methods in combination. The lower the cooling temperature of the reaction product gas in dry collection, the better from the point of view of collection efficiency.
Since there is a risk that methylamines will dissolve and produce hydrochloride, the temperature is preferably at least the dew point of the methylamines. The collected ammonium chloride may be recycled as a reaction raw material. After ammonium chloride has been separated and collected by the dry collection method, the gas is washed with water using a scrubber or the like using a conventional method. By doing so, methylamines, unreacted methanol, by-product ammonia, etc. in the gas are removed as water-soluble components, and a gas mainly containing methyl chloride remains as an insoluble component. The water-soluble components are separated into each component by means such as distillation, and unreacted methanol, by-product ammonia, etc. are recycled to the reaction system as necessary. It goes without saying that if methyl chloride as an insoluble component also contains trace amounts of impurities, it may be further purified by means such as distillation. According to the present invention, chlorine components and ammonia components can be effectively used as methyl chloride and methylamines from ammonium chloride and methanol without complicated operations, and this has great industrial significance. Example 1 A reactor with an inner diameter of 18 mmφ heated in an electric furnace was filled with 40 ml of MS-γ-alumina fluidized catalyst with an average particle size of 50 μ, and a mixed gas of methanol and ammonium chloride was mixed at a molar ratio of ammonium chloride to methanol of 1.4. , SV500hr ^-1 and reaction temperature 350°C. The high-temperature reaction product gas is introduced into a cylindrical glass air-cooled collector equipped with a filter, slowly cooled to about 100°C, and the entire amount of unreacted ammonium chloride is collected as a solid.Then, methylamine, Ammonia was separated and collected from the methyl chloride-containing gas. As a result, the methanol reaction rate was 98 mol%, the methyl chloride yield was 73% based on the methyl group of methanol (the same applies hereinafter), the methylamines (monomethylamine + dimethylamine + trimethylamine) yield was 20%, and the ammonium chloride conversion rate was 52%. It was hot. Of the ammonia content of the converted ammonium chloride, all of the ammonia content other than that consumed by methylamines was recovered as ammonia. (The same was true in the following Examples and Comparative Examples.) Comparative Example 1 After carrying out the reaction under the same conditions as in Example 1, the unreacted ammonium chloride, methylamine, and ammonia were immediately absorbed into the methyl chloride-containing mixture by water absorption. When separated and collected from the gas, a methanol reaction rate of 98%, a methyl chloride yield of 73%, a methylamine yield of 3%, and a methylamine hydrochloride yield of 17% were obtained. Example 2 A reaction was carried out under the same reaction conditions as in Example 1 except that the molar ratio of ammonium chloride to methanol was 0.6, and the methanol conversion rate was 98%.
Methyl chloride yield 50%, methylamine yield 43%,
An ammonium chloride conversion rate of 83% was obtained. In addition,
In all of the following Examples (Examples 2 to 5), the product collection method was the same as in Example 1. Example 3 When methanol, ammonia, and ammonium chloride were passed through the reactor used in Example 1 at an ammonium chloride/methanol molar ratio of 0.4, an ammonia/methanol molar ratio of 0.9, an SV of 500 hr ^-1 , and a reaction temperature of 350°C, no methyl chloride was obtained. rate 35%, methylamine yield
A success rate of 58% was obtained. Example 4 Table 1 shows the results obtained by carrying out the experiment in exactly the same manner as in Example 1, except that the following various catalysts were used in place of the catalyst used in Example 1.

[Table] Example 5 Example 1, reaction temperature 450℃, SV1500hr ^-1
As a result, a methanol conversion rate of 99%, a methyl chloride yield of 70%, and a methylamine yield of 24% were obtained.

Claims (1)

[Claims] 1. Methanol is subjected to a gas phase contact reaction with ammonium chloride, and unreacted ammonium chloride is selectively separated and collected from the resulting reaction product gas containing methyl chloride and methylamines using a dry collection method, and then the remaining gas is removed. A method for producing methyl chloride and methylamines, which comprises washing with water to separate and collect methylamines as a water-soluble component and methyl chloride as an insoluble gas component.