JP6082914B2 - Ammonia purification method - Google Patents

Description

  The present invention relates to a method for purifying ammonia used as a raw material for a gallium nitride-based compound semiconductor, and relates to a method for purifying crude ammonia containing oil as an impurity, such as crude ammonia commercially available for industrial use.

  Gallium nitride compound semiconductors are widely used as elements such as light emitting diodes and laser diodes. This gallium nitride compound semiconductor manufacturing process (gallium nitride compound semiconductor process) is usually performed by vapor-phase growth of a gallium nitride compound on a substrate such as sapphire by MOCVD, and a raw material used for this As the gas, for example, Group III trimethylgallium, trimethylindium, trimethylaluminum, and Group V ammonia are used.

  Generally, crude ammonia (industrial crude ammonia) commercially available for industrial use contains hydrogen, nitrogen, oxygen, carbon dioxide, water and the like. In addition, relatively high-purity ammonia is commercially available in a form obtained by further distillation or rectification, or in a form diluted with a high-purity inert gas. However, since the gallium nitride compound semiconductor processes that have been used in the past require extremely high purity ammonia as a raw material, relatively high purity ammonia obtained by distillation or rectification of industrial ammonia. Is used after further purification.

Conventionally, a method for purifying ammonia using a nickel catalyst or the like has been developed. For example, as a method of continuously purifying crude ammonia, there is a method of removing impurities by bringing the crude ammonia into contact with a catalyst mainly composed of nickel. Further, as a method for continuously purifying industrial ammonia and supplying it to a gallium nitride-based compound semiconductor process, a catalyst containing nickel as an active ingredient is used as a method for continuously purifying industrial ammonia and supplying it to a gallium nitride-based compound semiconductor process (Japanese Patent Laid-Open No. 5-124813). There is a method (JP-A-2002-37624) of removing impurities contained in crude ammonia by contacting with synthetic zeolite having a pore diameter of 4 to 10 Å after contact.
Japanese Patent Laid-Open No. 5-124813 Japanese Patent Laid-Open No. 6-107412 JP 2002-37624 A

  The method for purifying ammonia described in Patent Document 3 can continuously supply inexpensive crude ammonia commercially available for industrial use to a gallium nitride compound semiconductor process without distillation or rectification. is there. However, when purifying ammonia and supplying it to the gallium nitride compound semiconductor process, when the crude ammonia for industrial use was purified only by the ammonia purification method described in Patent Document 3, the ammonia was rectified to an extremely high purity. It has been found that the vapor phase growth rate of the gallium nitride compound growing on the surface of the substrate tends to be slightly lower than the case.

  In the ammonia purification method described in Patent Document 3, the cause of the decrease in the vapor growth rate of the gallium nitride compound is clarified, and a method capable of efficiently growing the gallium nitride compound on the surface of the substrate is developed. It is desirable. Therefore, the problem to be solved by the present invention is to remove impurities that cause adverse effects on the vapor phase growth rate, etc., without distilling or rectifying the cheap crude ammonia commercially available for industrial use, An object of the present invention is to provide a method for purifying ammonia which can be continuously supplied to a gallium nitride compound semiconductor process.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have (1) a process for producing industrial ammonia synthesized from hydrogen and nitrogen, which includes a gas compression process, which is used for a compressor in the process. Oil (oil for improving lubricity, rust prevention, etc.) can be mixed in ammonia. (2) Even if the amount of oil is small, it may adversely affect the vapor growth rate of gallium nitride compounds. (3) Oil content in the crude ammonia is removed by bringing it into contact with an oil removal means, and continuous or periodic oil content measurement is performed using an oil content measuring device, etc. It has been found that purified ammonia can be continuously supplied to a gallium nitride-based compound semiconductor process without adverse effects, and has reached the ammonia purification method of the present invention.

  That is, the present invention is a method for purifying crude ammonia containing an oil and one or more impurities selected from oxygen, carbon dioxide, and water, which is used as a raw material for a gallium nitride-based compound semiconductor, A step of removing oil contained in the crude ammonia in contact with a removing means, a step of measuring the presence or absence of oil in the crude ammonia after the oil removal step, or a concentration of the oil, and crude ammonia after the measurement step And a catalyst containing nickel as an active ingredient and a synthetic zeolite to remove the impurities other than oil.

  According to the method for purifying ammonia of the present invention, oil can be efficiently removed from crude ammonia containing oil without distillation or rectification. In addition, since the presence or absence of oil or the concentration of oil is measured, it is possible to prevent ammonia containing oil from being supplied to the gallium nitride compound semiconductor process. As a result, inexpensive industrial crude ammonia can be continuously purified and supplied to the gallium nitride compound semiconductor process without adversely affecting the vapor phase growth of the gallium nitride compound.

  The present invention is a method for refining ammonia used as a raw material for a gallium nitride compound semiconductor, and is applied to a method for refining crude ammonia containing oil as an impurity. In the present invention, as crude ammonia containing oil as impurities, in addition to industrial crude ammonia, exhaust gas containing ammonia discharged from the manufacturing process of gallium nitride compound semiconductor is subjected to pressure treatment and cooling treatment, Ammonia recovered by liquefying and recovering ammonia contained in the exhaust gas is included.

Hereinafter, although the purification method of ammonia of this invention is demonstrated in detail based on FIGS. 1-4, this invention is not limited by these.
1 to 3 are configuration diagrams showing an example of a set of apparatuses (ammonia purification apparatus) used in the present invention. FIG. 4 is a block diagram showing an example of a vapor phase growth apparatus that can apply ammonia obtained by the present invention as a raw material.
In addition, the manufacturing process of the gallium nitride compound semiconductor in the present invention is a manufacturing process for crystal growth of a nitride semiconductor composed of a compound of nitrogen and one or more metals selected from gallium, indium, and aluminum. It is a process.

  The method for purifying ammonia according to the present invention is a method for purifying crude ammonia, which is used as a raw material for a gallium nitride-based compound semiconductor, and contains one or more impurities selected from oil, oxygen, carbon dioxide, and water. Ammonia is brought into contact with (1) oil removing means to remove oil contained in the crude ammonia, and (2) the presence or absence of oil in the crude ammonia after the oil removing step or the concentration of oil is measured. And (3) a method for purifying ammonia comprising the step of bringing crude ammonia after the measurement step into contact with a catalyst containing nickel as an active ingredient and synthetic zeolite to remove the impurities other than oil.

  Specifically, the method for purifying ammonia according to the present invention includes, as shown in FIG. 1, an oil component supplied from a crude ammonia supply source 1, and one or more impurities selected from oxygen, carbon dioxide, and water. (1) After the oil content is removed by contacting the crude ammonia with the oil content removing means 2, (2) the presence or absence of the oil content or the concentration of the oil content is measured by the oil content measuring device 5, and (3) nickel as the active ingredient This is a method for purifying ammonia by contacting the catalyst 6 and the synthetic zeolite 7 to remove the impurities other than oil (one or more impurities selected from oxygen, carbon dioxide, and water).

The crude ammonia to be purified in the present invention is, for example, industrial ammonia, which is synthesized by a high-pressure reaction between hydrogen and nitrogen, and packed in a cylinder or the like as liquid ammonia and is commercially available. Such crude ammonia is guaranteed to have a purity of 99.9% or 99.99%, but as an impurity other than oxygen, carbon dioxide, and water, the oil component used in the compressor in the gas compression process during production is used. (Oil for improving lubricity, rust prevention, etc.). The oil component is long in crude ammonia gas in the form of mist (mainly oil mist having a diameter of about 0.01 to 100 μm) and gaseous form even after vaporizing liquid ammonia filled in a cylinder or the like. Floating for a period. The content of oil contained in the crude ammonia is usually 5 to 50 mg / m ³ .

  The oil removing means 2 used in the present invention is not particularly limited as long as it can efficiently remove the oil contained in the crude ammonia. However, as shown in FIG. It is preferable to use a filter 3 ′ and a filler 4 ′ filled in the filling cylinder 4. In such an oil removing means 2, crude ammonia comes into contact (passes) with the filter 3 ′ accommodated in the filter cylinder 3, whereby mist-like oil contained in the crude ammonia is removed, The gaseous oil contained in the crude ammonia is removed by contacting (passing) with the filled filler 4 ′.

  The filter 3 ′ used in the present invention has corrosion resistance against ammonia and is not particularly limited as long as it can remove mist-like oil. For example, the filter 3 ′ is made of ceramic fiber, glass fiber, metal fiber, or the like. Can be used. The form of the filter cylinder is not particularly limited, but for example, a filter cylinder in which a cylindrical filter is accommodated can be used. Moreover, it is preferable that the filter cylinder has a configuration in which a plurality of filters having different meshes are provided, and a mist-like oil component having a large particle diameter is sequentially removed.

The filler 4 ′ used in the present invention is not particularly limited as long as it has corrosion resistance to ammonia and can remove gaseous oil, and examples thereof include activated carbon, alumina, and diatomaceous earth. it can. Among these fillers, activated carbon is preferable because it is inexpensive and can be regenerated after use. In the case of using activated carbon, coconut shell charcoal, wood powder charcoal, peat charcoal or the like can be used, and among these activated carbons, those having a BET specific surface area of 500 m ² / g or more are more preferable. The filling length of the filler filled in the filling cylinder is usually 5 to 150 cm.

  As shown in FIG. 2, the filling cylinder is provided with a plurality of filling cylinders to purify ammonia in one of the filling cylinders, and at the same time exchange the filler in the other filling cylinder, By switching, ammonia can be purified continuously. In addition, the filler such as activated carbon used in the present invention is mainly for the purpose of removing moisture etc. contained in the filler in advance, and normally, before use, the filler such as nitrogen is heated while being heated at a temperature of 200 ° C. or less. A process of flowing an active gas or a process of flowing an inert gas heated to a temperature of 200 ° C. or lower is performed.

  Although the contact temperature between the crude ammonia and the filter and the contact temperature between the crude ammonia and the filler are 100 ° C. or lower, both of them may be at ordinary temperature (0 to 50 ° C.), and heating or cooling is not particularly required. The pressure is not particularly limited, and the treatment can be performed at normal pressure, reduced pressure, or increased pressure. Usually, the treatment is performed under normal pressure or 0.3 MPa. Moreover, the empty cylinder linear velocity (LV) of the crude ammonia in the filling cylinder at the time of refining is usually 100 cm / sec or less, preferably 30 cm / sec or less.

  Note that any impurities selected from oxygen, carbon dioxide, and water contained in the crude ammonia pass through the filter without being removed from the crude ammonia even when in contact with the filter, and even if activated carbon is used as a filler, It is hardly removed from the crude ammonia to such an extent that it can be retained in a small amount by activated carbon. (Ease of adsorption by activated carbon at normal temperature: gaseous oil> ammonia> carbon dioxide, etc.) If crude ammonia is not contacted with the filter in advance, mist-like oil will adhere to the surface of the filler such as activated carbon. As time passes, the adsorption of gaseous oil is prevented.

  The oil content measuring device 5 used in the present invention is not particularly limited as long as it can measure the oil content contained in the crude ammonia or the oil content contained in the gas sampled from the crude ammonia. Flame ionization detectors, infrared absorption analyzers, quadrupole gas analyzers, gas chromatograph mass spectrometers and the like can be mentioned. As shown in FIG. 3, the oil content measuring device 5 removes the oil content in one of the lines in the oil content removing means having two or more lines composed of the filter cylinder 3 and the filling cylinder 4, and at the other line, This is particularly effective when ammonia is continuously purified by changing the filter and / or filler and switching the line as soon as the oil content is detected by the oil content measuring device. In order to remove the oil that has passed from the detection of the oil until the line is switched, a preliminary oil removal means can be provided upstream of the catalyst 6 containing nickel as an active ingredient. The oil content measuring device may be provided permanently, but it may be provided only when measuring the oil content, or only the sampling gas outlet may be provided.

  The catalyst containing nickel as an active ingredient used in the present invention is mainly composed of a nickel compound which is easily reduced, such as metallic nickel or nickel oxide. Further, a metal component other than nickel may contain a small amount of metal such as chromium, iron, cobalt, or copper. These nickels may be used alone or in a form supported on a catalyst carrier, but are usually supported on a catalyst carrier for the purpose of increasing the contact efficiency between the nickel surface and gas. It is preferable to use it in the form.

As a method for supporting nickel on a carrier, for example, carrier powders such as diatomaceous earth, alumina, silica alumina, aluminosilicate, and calcium silicate are dispersed in an aqueous solution of nickel salt, and an alkali is further added to add nickel on the carrier powder. The cake obtained by precipitating the components and then filtering and washing with water as necessary is dried at 120 to 150 ° C. and then baked at 300 ° C. or higher, and the baked product is pulverized, or NiCO ₃ , Ni (OH) ₂ Inorganic salts such as Ni (NO ₃ ) ₂ and organic salts such as NiC ₂ O ₄ and Ni (CH ₃ COO) ₂ are fired and pulverized, and then heat-resistant cement is mixed and fired. .

  These are usually formed into a molded body by extrusion molding, tableting molding or the like, and are used as they are or after being crushed to an appropriate size as required. As a molding method, a dry method or a wet method can be used, and a small amount of water, a lubricant, or the like may be used. Moreover, since there exists what is marketed as a nickel-type catalyst, you may use what was selected from them. The point is that reduced nickel, nickel oxide or the like is finely dispersed and has a large surface area and high contact efficiency with the gas.

The BET specific surface area of the catalyst containing nickel as an active ingredient is usually 10 to 300 m ² / g, preferably 30 to 250 m ² / g. Moreover, the content rate of nickel with respect to the whole catalyst is 5 to 95 wt% normally, Preferably it is 20 to 95 wt%. If the nickel content is less than 5 wt%, the ability to remove oxygen will be low, and if it is higher than 95 wt%, sintering may occur during hydrogen reduction and the activity may be reduced. (Catalysts containing nickel as an active ingredient are usually subjected to hydrogen reduction to activate them before use. For hydrogen reduction, for example, a mixed gas of hydrogen and nitrogen is emptied at about 350 ° C. or less. (This can be done by passing the tube at a linear velocity (LV) of about 5 cm / sec.)

  The synthetic zeolite used in the present invention is a synthetic zeolite obtained by chemically substituting a part of sodium of a synthetic crystalline aluminosilicate hydrous sodium salt with potassium. This synthetic zeolite crystal has a large number of pores inside and is characterized by substantially uniform pore diameters. These synthetic zeolites are usually used after being molded into a spherical product having a diameter of 4 to 20 mesh, a columnar product having a diameter of 1.5 to 4 mm, and a height of 5 to 20 mm so that it can be used efficiently. In the present invention, preferably, synthetic zeolite having a pore diameter corresponding to 4 to 10 mm is used. Synthetic zeolite is usually activated while aerated with an inert gas at a temperature of about 200 to 350 ° C. before use.

  In the present invention, mainly oxygen and carbon dioxide are removed from crude ammonia by contact with a catalyst containing nickel as an active ingredient, and mainly carbon dioxide and water are removed from crude ammonia by contact with synthetic zeolite. . The concentrations of oxygen, carbon dioxide, and water contained in the crude ammonia applied to the present invention are usually 100 ppm or less. If the concentration of these impurities is higher than this, the amount of heat generated may increase, so a heat removal means is required depending on the conditions.

  The packing length of the catalyst containing nickel as an active ingredient and the synthetic zeolite is usually 5 to 150 cm in practice. The hollow linear velocity (LV) of the crude ammonia at the time of purification varies depending on the concentration of impurities in the supplied crude ammonia and the operating conditions, and cannot be specified unconditionally, but is usually 100 cm / sec or less, preferably 30 cm / sec or less. is there. The contact temperature between the crude ammonia and the catalyst containing nickel as an active ingredient, and the contact temperature between the crude ammonia and the synthetic zeolite are 100 ° C. or less, but both of them may be at ordinary temperature, and heating or cooling is not particularly required. The pressure is not particularly limited, and the treatment can be performed at normal pressure, reduced pressure, or increased pressure. Usually, the treatment is performed under normal pressure or 0.3 MPa.

  EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not limited by these.

[Example 1]
(Production of ammonia purification equipment)
An ammonia purification apparatus having the same configuration as shown in FIG. 1 was manufactured except that the nickel catalyst and the synthetic zeolite were separated into separate processing cylinders. A hydrogen flame ionization detector was used as the oil content measuring device. The filter cylinder is made of three filters with different grain sizes (manufactured by Domnique Hunter, AO grade (oil mist having a diameter of about 1 μm is removed), AA grade (oil mist having a diameter of about 0.01 μm) AX grade (removal of oil mist having a diameter of 0.01 μm or less)) is provided, and the mist-like oil component having a larger particle diameter is removed in order.

Further, activated carbon (BET specific surface area of about 800 m ² / g) was filled into a stainless steel filling cylinder having an inner diameter of 20 mm and a length of 200 mm so that the filling length was 150 mm. Furthermore, a commercially available nickel catalyst was filled into a stainless steel catalyst cylinder having an inner diameter of 45.2 mm and a length of 200 mm so as to have a filling length of 150 mm, and a commercially available synthetic zeolite equivalent to 4 mm was disposed downstream of the catalyst cylinder. A stainless steel adsorption cylinder having an inner diameter of 45.2 mm and a length of 200 mm was filled to a filling length of 150 mm.

  Next, the activated carbon was dried by flowing 150 ° C. nitrogen through the filling cylinder at a flow rate of 3 L / min for 1 hour. Further, the nickel catalyst was heated to 300 ° C., and the nickel catalyst was reduced by flowing a mixed gas of hydrogen and nitrogen (hydrogen 5 vol%, nitrogen 95 vol%) at a flow rate of 3 L / min for 5 hours. In addition, the synthetic zeolite was heated to 300 ° C., and the synthetic zeolite was activated by flowing nitrogen at a flow rate of 3 L / min for 5 hours.

(Ammonia purification experiment)
In order to shorten the time of the purification experiment, the purification experiment was performed using crude ammonia containing a mist-like oil in a larger amount than crude ammonia commercially available for industrial use. This crude ammonia was analyzed in advance with a thermal conductivity detector (GC-TCD), a flame ionization detector (GC-FID), and a Fourier transform infrared spectrophotometer (FT-IR). , Carbon dioxide, and water were contained at 5 ppm, 6 ppm, and 35 ppm, respectively. The crude ammonia contained about 50 mg / m ^{3 of} mist-like oil and about 0.9 g / m ^{3 of} gaseous oil. (Under these conditions, the activated carbon needs to be replaced sooner than the filter.)

  This industrial crude ammonia was circulated under conditions of normal temperature, normal pressure, and a flow rate of 10 L / min to conduct a purification experiment. Oxygen in the outlet gas of the catalyst cylinder filled with synthetic zeolite using GC-TCD, GC-FID, and FT-IR (all detection limit concentrations are 0.01 ppm) at intervals of 1 hour after the start of the purification experiment. , Carbon dioxide, and water concentrations were measured. Similarly, the oil content in the outlet gas of the filled cylinder filled with activated carbon was measured at intervals of 1 hour. As a result, when 12 hours had passed since the start of the experiment, oil was detected from the outlet gas of the filling cylinder, and the experiment was terminated. During this time, none of oxygen, carbon dioxide and water was detected from the outlet gas of the catalyst cylinder.

[Example 2]
In the production of the ammonia refining apparatus of Example 1, an ammonia refining apparatus was produced in the same manner as in Example 1 except that a powder mainly composed of alumina was used instead of activated carbon as a filler for removing oil. .
Ammonia purification experiment was conducted in the same manner as in Example 1 except that this ammonia purification apparatus was used. As a result, when 6 hours passed from the start of the experiment, an oil component was detected from the outlet gas of the filling cylinder, so the experiment was terminated. During this time, none of oxygen, carbon dioxide and water was detected from the outlet gas of the catalyst cylinder.

[Example 3]
In the production of the ammonia purification apparatus of Example 1, an ammonia purification apparatus was produced in the same manner as in Example 1 except that powder made of diatomaceous earth was used instead of activated carbon as a filler for removing oil.
Ammonia purification experiment was conducted in the same manner as in Example 1 except that this ammonia purification apparatus was used. As a result, when 5 hours had elapsed since the start of the experiment, an oil component was detected from the outlet gas of the filling cylinder, so the experiment was terminated. During this time, none of oxygen, carbon dioxide and water was detected from the outlet gas of the catalyst cylinder.

[Example 4]
(Production of vapor phase growth equipment)
Inside the stainless steel reaction vessel, a disk-shaped susceptor (SiC coated carbon, 600 mm diameter, 20 mm thickness, can hold five 3 inch substrates), facing the susceptor with a structure for circulating a refrigerant ( A vapor phase growth apparatus as shown in FIG. 4 was manufactured by providing a carbon), a heater, a source gas introduction part (made of carbon), a reaction gas discharge part, and the like. Five substrates made of 3 inch sapphire were set in a vapor phase growth apparatus. In addition, as a structure which distribute | circulates a refrigerant | coolant, one piping was arrange | positioned spirally toward the peripheral part from the center part.

The introduction part of the source gas forms three gas jets partitioned in the vertical direction by two disk-shaped partitions (made of carbon) having a diameter of 200 mm and a thickness of 2 mm. From the upper jets, ammonia and the middle layer are formed. The gas containing TMG can be supplied from the nozzle and the nitrogen can be supplied from the lower nozzle.
The distance between the front end of the gas ejection port and the substrate was 32.4 mm. Furthermore, piping was connected to each gas flow path of the raw material gas introduction section through a mass flow controller or the like so that each gas having a desired flow rate and concentration could be supplied.

(Vapor phase growth experiment)
Ammonia for industrial use (impurity content: oxygen 5 ppm, carbon dioxide 6 ppm, water 35 ppm, mist oil content approximately 10 mg / m ³ , gaseous oil content approximately 3 mg / m ³ ) It set so that it could supply to the above-mentioned vapor phase growth apparatus via a refiner. In addition, other source gases were also set so that they could be supplied from the source of each source via the respective purifiers to the vapor phase growth apparatus. Thereafter, gallium nitride (GaN) was grown on the surface of the substrate as follows.

  In the vapor phase growth of gallium nitride, after the buffer layer growth, the substrate temperature is increased to 1050 ° C., ammonia (flow rate: 30 L / min) from the upper jet port, and TMG (flow rate: 60 cc / min) from the middle jet port. Hydrogen (flow rate: 30 L / min) and nitrogen (flow rate: 40 L / min) were supplied from the lower outlet, and a gallium nitride film was grown for 1 hour. After completion of the vapor phase growth experiment, the temperature was lowered and the substrate was taken out of the reaction vessel. Furthermore, such a vapor phase growth experiment was repeated 5 times in total. As a result, the average value of the GaN film thickness of the 25 substrates was 4.2 μm.

[Comparative Example 1]
In the production of the ammonia refining apparatus of Example 1, an ammonia refining apparatus was produced in the same manner as in Example 1 except that the oil removing means was not used.
In the vapor phase growth experiment of Example 4, the vapor phase growth experiment was performed in the same manner as in Example 4 except that this ammonia purifier was used. As a result, the average value of the GaN film thickness of 50 substrates obtained by repeating the vapor phase growth experiment 5 times in total was 3.5 μm. The decrease in the growth rate of the GaN film thickness is thought to be due to the oil component having an adverse effect on the vapor phase growth.

  As described above, the method for purifying ammonia of the present invention can efficiently remove oil from crude ammonia containing oil. In addition, inexpensive industrial ammonia can be continuously purified and supplied to the gallium nitride compound semiconductor process while removing oil that adversely affects the vapor phase growth rate of the gallium nitride compound.

The block diagram which shows an example of the apparatus set (ammonia purification apparatus) used for this invention Configuration diagram showing an example of an ammonia purification apparatus other than FIG. 1 used in the present invention. 1 is a block diagram showing an example of an ammonia purifier other than those shown in FIGS. 1 and 2 used in the present invention. The block diagram which shows an example of the vapor phase growth apparatus which can apply the ammonia obtained by this invention as a raw material

DESCRIPTION OF SYMBOLS 1 Supply source of crude ammonia 2 Oil content removal means 3 Filter cylinder 3 'filter 4 Filled cylinder 4' filler 5 Oil content measuring device 6 Nickel-containing catalyst 7 Synthetic zeolite 8 Purified ammonia outlet 9 Substrate holder 10 Susceptor 11 Face of susceptor 12 Heater 13 Reactor 14 Source gas introduction part 15 Reaction gas discharge part 16 Source gas pipe 17 Flow path for circulating refrigerant 18 Susceptor rotating plate

Claims (5)

A method for purifying crude ammonia containing an oil and one or more impurities selected from oxygen, carbon dioxide, and water, which is used as a raw material for a gallium nitride-based compound semiconductor, wherein the crude ammonia is brought into contact with an oil removing means. A step of removing oil contained in the crude ammonia , a step of measuring the presence or absence of oil in a portion of the crude ammonia from the crude ammonia after the oil removal step , and a step of removing the oil. of coarse ammonia after, the crude ammonia remaining portion, in contact with the catalyst and synthetic zeolites as an active ingredient nickel, viewed including the step of removing the impurities other than oil, said oil removing means, the crude ammonia In contact with multiple filters with different grain sizes, removing mist-like oils in order of larger particle size, and then contacting with filler Method of purifying ammonia, characterized in that it.   The method for purifying ammonia according to claim 1, wherein the crude ammonia containing oil is crude ammonia commercially available for industrial use. By contact with crude ammonia and filter, according to claim 1 mist of oil contained in the crude ammonia is removed from the crude ammonia by contact with crude ammonia and the filler, to remove gaseous oil component contained in the crude ammonia Or the method for purifying ammonia according to 2 . The method for purifying ammonia according to any one of claims 1 to 3, wherein the filler is activated carbon. The method for measuring the presence or absence of oil or the concentration of oil in crude ammonia is a method using a flame ionization detector, an infrared absorption analyzer, a quadrupole gas analyzer, or a gas chromatograph mass spectrometer. The method for purifying ammonia according to any one of -4 .

Images