JPH11228507A - Production of dimethylamine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing dimethylamine in good productivity by reacting methanol with ammonia in the presence of a catalyst to provide mono- and di-methylamines and converting the monomethylamine to the dimethylamine by a disproportionation in the presence of the catalyst. SOLUTION: Raw materials consisting essentially of methanol and ammonia are reacted in the presence of a catalyst at 200 400 deg.C, preferably 250-350 deg.C to provide methylamines including monomethylamine and dimethylamine, and the monomethylamine is disproportionated in the presence of the catalyst to convert the monomethylamine to the dimethylamine in the method for producing the dimethylamine. Silica-modified crystalline silicoaluminophosphate molecular sieves consisting essentially of at least one kind selected from a group of SAPO-11, 17, 18, 26, 31, 33, 34, 35, 42, 43, 44, 47 and 56 are used as the catalyst for at least one of or both of the before two steps.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a process for producing dimethylamine. Dimethylamine is important as a raw material for solvents such as dimethylformamide, rubber products, pharmaceuticals and surfactants.

[0002]

2. Description of the Related Art As a method for industrially producing dimethylamine, a method for producing dimethylamine from methanol and ammonia is typical. Usually, a temperature of about 400.degree. C. using an amorphous solid acid catalyst such as silica-alumina is used. It is manufactured by a gas phase reaction. As is well known, when an amorphous solid acid catalyst is used, a mixture of three thermodynamic equilibrium compositions of monomethylamine, dimethylamine and trimethylamine is obtained. Since the demand for methylamines is mostly biased toward dimethylamine, methylamines other than dimethylamine are usually circulated and disproportionate. However, if trimethylamine is generated as described above, the formation of a complicated azeotrope with ammonia, monomethylamine, or dimethylamine leads to an increase in the amount of process circulation and an increase in the size of equipment, resulting in large energy consumption. There are drawbacks such as increased costs. In order to solve such disadvantages, various attempts have been made to selectively obtain dimethylamine.

In recent years, a method for producing dimethylamine exceeding a thermodynamic equilibrium composition using a zeolite catalyst has been proposed. For example, zeolite A (JP-A-56-684)
No. 6), FU-1 (JP-A-54-48708), ZSM-5 (US Pat. No. 4,082,805), ferrierite and erionite (JP-A-56-1137).
No. 47), ZK-5, Rho, shabasite and erionite (JP-A-61-254256), mordenite (JP-A-56-46846, JP-A-58).
JP-A-49340, JP-A-59-21050, JP-A-59-227841), silylation of zeolite (JP-A-3-262540), and liquid-phase silylation treatment (JP-A-8-193957). Japanese Patent Application Laid-Open No. H8 (1996)) or zeolite modified with a chelating agent
No. 225498).
However, these methods have not been practically sufficient.
In addition, as a method for producing dimethylamine, a method based on a disproportionation reaction between monomethylamine and methanol or monomethylamine is known, but in any case, production of trimethylamine is inevitable. A method for disproportionation of monomethylamine which selectively obtains dimethylamine which has solved this problem has been proposed. For example, a method using zeolites such as mordenite, ferrierite and clinoptilolite (JP-A-56-46846).
However, although this method can increase the selectivity of dimethylamine, the conversion of monomethylamine is low and the yield of dimethylamine is low at a temperature around 300 ° C. where a practical catalyst life can be expected. It was difficult to apply to the process. The selective production of dimethylamine from methanol and ammonia is very significant from a technical and economic point of view, and it is desired to solve this problem.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a process for producing dimethylamine from methanol and ammonia which overcomes the disadvantages of the prior art.

[0005]

SUMMARY OF THE INVENTION The present inventors have intensively studied to develop an industrially feasible method for selectively producing dimethylamine. As a result, a silica-modified molecular sieve catalyst that selectively produces monomethylamine and dimethylamine by suppressing the formation of trimethylamine in the reaction of methanol and ammonia has surprisingly surprisingly been used in the disproportionation reaction of monomethylamine. It has been found that dimethylamine has high activity and selectivity, and that dimethylamine can be produced more advantageously than in the past.

That is, the present invention relates to a process for producing methylamines containing monomethylamine and dimethylamine from a raw material containing methanol and ammonia as main components in the presence of a catalyst, and the monomethylamine obtained in the process 2 Disproportionating to dimethylamine in the presence of a catalyst, and using a silica-modified crystalline silicoaluminophosphate molecular sieve as a catalyst in at least one of step 1 and step 2. It is a manufacturing method.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION As a catalyst that can be used in Steps 1 and 2 of the present invention, the effective pore diameter is from 0.3 to 0.6 nm.
Can be listed. For example, in the structural code of zeolite of IUPAC and its analogous compounds, ABW, AEI, A having an 8-membered ring structure
FX, APC, ATN, ATT, ATV, AWW, CH
A, DDR, EAB, ERI, GIS, JBW, KF
I, LEV, LTA, MER, MON, PAU, PH
I, RHO, RTE, RTH, VNI, CHI, LOV, RSN, VSV as a 9-membered ring structure, and D as a 10-membered ring structure
AC, EPI, FER, LAU, MEL, MFI, MF
S, MTT, NES, TON, WEI, AFS, AFY, ATO, CAN, GME, MAZ, M with 12-membered ring structure
EI, MTW, OFF, RON, VET, etc.
A crystalline aluminosilicate molecular sieve and a crystalline silicoaluminophosphate molecular sieve corresponding to such a structure are preferable.

Specifically, as crystalline aluminosilicate molecular sieve, shabasite, mordenite,
Elionite, Ferrierite, Epistilite,
Clinoptilolite, Paulingite, Philippite, Levinite, Zeolite-A, rho, ZK-
5, FU-1, and ZSM-5. In addition, the crystalline aluminosilicate may be subjected to ion exchange or metal substitution for the purpose of increasing acid strength and activity, such as Li,
Na, K, Rb, Cs, Be, Mg, Ca, Sr, B
a, Be, Mg, Ca, Sr, Ba, Ga, Zn, F
It is appropriate to use atoms such as e, Co, B, P, and Ge.

In the present invention, the crystalline silicoaluminophosphate molecular sieve refers to a crystalline aluminum phosphate compound in which a part of the P or Al-P bond is isomorphously substituted with silicon, and is usually called SAPO. Is done. Specifically, for example, SAPO-5, 11, 17, 18,
31, 34, 35, 37, 40, 41, 42, 44, 4
7, or 56, and the like.
i, Zr, V, Cr, Mn, Fe, Co, Zn, Be,
Compounds isomorphously substituted with Mg, Ca, B, Ga, Ge, or the like can be given. Among them, SAPO-11, 17, 1
8, 26, 31, 33, 34, 35, 42, 43, 4
4, 47 and 56 are particularly preferred.

[0010] Such a crystalline molecular sieve is prepared by adding an aluminum compound, a silica source and, if necessary, a phosphoric acid aqueous solution.
The desired product can be obtained relatively easily by hydrothermal synthesis using an amine or a quaternary ammonium compound as a template agent. In order to obtain a suitable crystalline molecular sieve as a dimethylamine catalyst, it is particularly preferable to use an amine or organic ammonium salt aqueous solution used as a template agent for 20 minutes.
And then hydrolyzed by adding aluminum alkoxide to obtain a homogeneous aluminum hydroxide colloid or aqueous solution, silica or silicon source, and phosphoric acid or phosphorus source as needed, Li, Ti, Zr, V, C
r, Mn, Fe, Co, Zn, Be, Mg, Ca, B,
This is to follow the procedure of hydrothermally treating the mixture to which the Ga and Ge sources have been added.

The above-mentioned crystalline aluminosilicates and crystalline silicoaluminophosphates can be used as catalysts in the steps 1 and 2 of the present invention, but they are often insufficient to suppress the formation of trimethylamine. In order to selectively obtain dimethylamine, catalyst modification is preferable, and S
Modification by group III and group IV elements such as i, Ge, B, Ga, etc. is preferred. Among them, it is particularly preferable to carry out silica modification. As the silica modification method, for example, a process of adding a Si source to a catalyst before silica modification and depositing, precipitating or coating silicon atoms on the surface thereof, gas-phase silylation by CVD using silicon tetrachloride, or an organic silicon compound There is a silane treatment to be used. Examples of the organic silicon compound used for the silane treatment include, for example, alkyl such as triethylsilane, methylphenylsilane, phenylsilane, diphenylsilane and triethylsilane, or aralkylsilanes, methyldichlorosilane, ethylmethylchlorosilane, dimethyldichlorosilane and phenylmethylchlorosilane. Such as chlorosilanes, trimethoxysilane, tetramethoxysilane, triethoxysilane, tetraethoxysilane, alkoxysilanes such as diethoxymethylsilane and allyloxytrimethylsilane, dimethylaminotrimethylsilane, N,
Silylamines such as N-dimethylaminodimethylsilane and tris (N, N-dimethylamino) methylsilane, N, O
And silylamides such as -bis (trimethylsilyl) acetamide, N-trimethylsilylacetamide and bistrimethylsilylurea. Of these, inexpensive chlorosilanes and alkoxysilanes are preferred, and alkoxysilanes are particularly preferred.

At the time of the above-mentioned silica modification with the silane treatment agent, a steam heat treatment is performed in advance at a temperature of 250 to 750 ° C., an immersion treatment with an acid, an amine, a chelating agent or the like, or an appropriate humidity control treatment is selected. It is more effective to perform it appropriately. Although it is difficult to stipulate the treatment conditions by the silane treatment agent, for example, from room temperature to 700 ° C.
Immersion time of less than 48 hours at a temperature in the range
It can be carried out in a gas phase, liquid phase of 1 MPa or less, or 30 MPa or less, or in a supercritical state. Silane treatment,
In order to make it more effective, it is preferable to appropriately perform immersion treatment, heat shaking, ultrasonic dispersion, and the like using an appropriate solvent such as alcohols, esters, and hydrocarbons. The concentration of the silane treatment agent is usually sufficient if it is in the range of 1 to 30% by weight, but is not particularly limited. After the silane treatment, filtration, washing, and drying treatments are performed, preferably in an oxidizing atmosphere, at a temperature of 400 to 750 ° C,
Firing under conditions of 2 to 24 hours imparts high catalytic activity and selectivity to dimethylamine.

[0013] Among the silica-modified crystalline aluminosilicates and silica-modified crystalline silicoaluminophosphates thus obtained, the catalyst used in Steps 1 and 2 of the present invention includes silica-modified crystalline silicoaluminophosphates. Particularly preferred. Therefore, in the present invention, silica-modified crystalline silicoaluminophosphates are used in at least one of Step 1 and Step 2. The most preferred embodiment uses silica-modified crystalline silicoaluminophosphates in both Step 1 and Step 2. The silica-modified catalyst can be suitably used for the production of dimethylamine as it is, or by subjecting it to a molding treatment by adding an appropriate binder.

The apparatus used for carrying out the present invention is mainly composed of step 1
And a sub-reactor used to perform Step 2. In step 1, methylamines containing monomethylamine and dimethylamine are produced from a raw material mainly containing methanol and ammonia in the presence of a catalyst. After the reaction in Step 1, recover ammonia containing monomethylamine,
Trimethylamine recovery and dehydration, followed by recovery of monomethylamine and dimethylamine. Recovery is usually performed by distillation. The recovered ammonia and trimethylamine are recycled to the main reactor of Step 1. The recovered monomethylamine is converted to dimethylamine by a disproportionation reaction in the side reactor of Step 2. The recovered monomethylamine can be circulated to the main reactor to disproportionate the monomethylamine, but in order to convert the recovered monomethylamine to dimethylamine efficiently, It is preferred to provide a reactor. The dimethylamine produced in Step 1 and Step 2 is obtained as the target substance. Step 1
The reaction mode in step 2 is particularly preferably carried out in a flow system in a fixed-phase gas phase bed or a fluidized bed, but is not limited thereto. These main and sub-reactors may be implemented singly or as required with a plurality of reactors.

The raw materials in step 1 are methanol and ammonia, which may contain dimethyl ether and methylamines. The starting material in step 2 is monomethylamine, which may include methanol and dimethyl ether, or other methylamines. In both cases of Step 1 and Step 2, it is preferable to carry out the reaction at a temperature in the range of 200 to 400 ° C., and particularly preferably in the range of 250 to 350 ° C. in consideration of the selectivity of dimethylamine and the catalytic activity.
There is no particular problem whether the catalysts charged in the main reactor and the sub-reactor are the same or different. The catalyst is preferably used in a single layer or in a plurality of layers and used in a packed manner.For the purpose of removing the reaction heat or suppressing the side reaction caused by the increase in the temperature of the catalyst layer and avoiding a reduction in the catalyst life, a plurality of catalysts are used. It is particularly preferable to provide a catalyst packed layer or to divide the raw material and supply it to a plurality of catalyst layers.

The reaction pressure in step 1 and step 2 is usually preferably from 0.1 to 10 MPa, particularly preferably from 0.5 to 2 MPa. The higher the raw material supply rate (GHSV 1 / h) in Steps 1 and 2, the better in terms of productivity. However, if it is too high, it is not preferable because the raw material conversion rate decreases. In the present invention, it is preferable that the GHSV is usually 100 to 10,000 per hour. Due to the above reaction conditions, almost no trimethylamine is contained at the outlet of the main reactor due to the monomethylamine content of 2
0 to 40% by weight, dimethylamine content 60 to 8
Methylamine having a composition of about 0% by weight is obtained. Therefore, the yield of dimethylamine can be further improved by combining step 2 in which monomethylamine can be effectively converted to dimethylamine.

In the present invention, it is possible to use the same catalyst as in Step 1 for disproportionation, and moreover, about 8% of monomethylamine is used.
Since 0% can be converted to dimethylamine, the combined overall yield of the two steps reaches a maximum of about 90%. The yield per stage using the existing method, that is, using an equilibrium type catalyst, is about 25.
%, And even when a zeolite catalyst is used,
Only 0%. Therefore, the present invention provides a very advantageous means for producing dimethylamine. According to the present invention, it is not necessary to circulate a large amount of a process fluid mainly composed of ammonia or trimethylamine as in the related art, and a higher dimethylamine yield can be obtained as compared with the related art.

[0018]

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. In the following Examples and Comparative Examples, the reaction to dimethylamine was carried out using a raw material tank, a raw material supply pump, a mass flow controller for introducing an inert gas, a reaction tube (inner diameter 13φ, length 300 mm, SUS316L), a sample collecting tank, The test was performed using a pressurized circulation circulation reactor equipped with a pressure valve, a device for separating and purifying methylamines, and the like. A sub-reactor arranged in parallel with a main reactor for reacting methanol and ammonia was used as necessary. After 2 to 4 hours after the reaction reaches a steady state, a sample is taken over about 1 hour and analyzed by gas chromatography with FID detection method using Pora PLOT Amines as a capillary column to determine the composition distribution of methylamines. Was. Further, the material balance of the process fluid was determined as required.

Catalyst Preparation Example 1 Silica-modified SAPO-34: 35% -A mixture of tetraethylammonium hydroxide (151.47 g) and pure water (84.2 g) was mixed with 0
After cooling to 0 ° C., aluminum isopropoxide (81.7 g) was added over 3 minutes, and high-speed stirring was performed for 15 minutes. next,
Silica sol (12 g) was added, and the mixture was stirred at a high speed for 5 minutes to be uniform. Further, 85% phosphoric acid (46.1 g) was added, and the mixture was similarly stirred for 5 minutes, followed by crushing for 1 hour. The resulting mixture was heated in an autoclave at 200 ° C. for 4 hours. The product is centrifuged and washed four times.
Dry at 110 ° C. overnight. The mixture was further calcined at 600 ° C. for 4 hours in the air to obtain a white crystalline powder (40 g). This powder is XR
The result of D analysis was consistent with the diffraction pattern of SAPO-34. Also, the crystallinity was high, and the particles were uniform and well aligned. The crystals were adjusted to a water content of 10% by weight. Then, 13% tetraethoxysilane (TEO)
It was immersed in a dry toluene solution of S) for 16 hours. After immersion, the crystals were separated by filtration and dried under reduced pressure at 120 ° C. for 4 hours. Thereafter, the mixture was further calcined at 600 ° C. for 3 hours in the air to obtain 37.9 g of silica-modified SAPO-34 (catalyst 1).

Catalyst Preparation Example 2 Silica-Modified CoSAPO-34: A cobalt-containing SAPO-34 was obtained in the same manner as in Catalyst Preparation Example 1, except that cobalt acetate (2.5 g) was added as a metal source. Thus, a silica-modified catalyst 2 was obtained.

Catalyst Preparation Example 3 Silica-Modified TiSAPO-34: TiSAPO-34 was obtained in the same manner as in Catalyst Preparation Example 2 except that Ti isopropoxide was used as a Ti source, and further subjected to silane treatment to be modified with silica. Catalyst 3 was obtained.

Catalyst Preparation Example 4 5 weight% of silica gel as silicon was added to SAPO-34, dried, calcined at 50 ° C., and tableted to obtain Catalyst 4.

Catalyst Preparation Example 5 Mordenite (Tosoh, HSZ-630HOA, Si / Al2 = 16)
Dipped in 7% by weight of TEOS dry ethanol solution,
Ultrasonic dispersion treatment was performed at 4 ° C. for 4 hours. Next, after performing centrifugation and washing four times, it was dried under reduced pressure at 120 ° C. for 2 hours, and further calcined in air at 600 ° C. for 3 hours to obtain silica-modified mordenite (catalyst 5).

Catalyst Preparation Example 6 A steam-treated Na mordenite catalyst was prepared according to a method described in a known document (Japanese Patent Laid-Open No. 59-227841, etc.) (catalyst 6).

Example 1 (Main reaction: reaction between methanol and ammonia) A reaction tube was charged with 7.5 g (volume: 13.5 ml) of a catalyst, and a raw material (methanol: ammonia = 1: 1) mixture was charged at an hourly space velocity of 20 g. (GHSV: 1 / h) Supply at 1500, pressure 2M
The reaction was performed at a Pa temperature of 320 ° C. The reaction results were as follows: methanol conversion was 99.4%, and selectivities of mono, di and trimethylamine were 35, 63 and 2% by weight, respectively. (Disproportionation: disproportionation reaction of monomethylamine) Using 2.8 g (volume 5 ml) of catalyst 1 and supplying monomethylamine as a raw material at a space velocity (GHSV: 1 / h) of 500, pressure 2 MPa, temperature The reaction was performed at 320 ° C. The reaction results were as follows: methanol conversion was 80%, and selectivities of di and trimethylamine were 99 and 1% by weight, respectively.

Example 2 The reaction was carried out in the same manner as in Example 1 except that the catalyst 2 was used. The reaction results are shown in Table 1.

Example 3 A reaction was carried out in the same manner as in Example 1 except that the catalyst 3 was used. The reaction results are shown in Table 1.

Example 4 The reaction was carried out in the same manner as in Example 1 except that the catalyst 4 was used. The reaction results are shown in Table 1.

Example 5 The main reactor was filled with 20 ml of the catalyst 1 and the sub-reactor was similarly filled with 4 ml of the catalyst 1.
The reaction was carried out at a pressure of 320 ° C. at a pressure of MPa. The outline of the reaction process is shown in FIG. Methanol and ammonia, and ammonia containing methylamines circulated from the distillation system were supplied to the main reactor at a space velocity (GHSV: 1 / h) of 1580. Monomethylamine separated and recovered by distillation
At 470, it was fed to the side reactor. Table 2 summarizes the material balance of the process fluid. The amount of dimethylamine produced at this time was 9.1 g / hour.

Comparative Example 1 According to Catalyst Preparation Example 1, SAPO without silica modification
-34 was prepared and reacted in the same manner as in Example 1 except that this was used as a catalyst. The reaction results are shown in Table 1.

Comparative Example 2 CoSAPO-34 without silica modification was prepared and reacted in the same manner as in Example 1 except that this was used as a catalyst. The reaction results are shown in Table 1.

Comparative Example 3 A reaction was carried out in the same manner as in Example 1 except that TiSAPO-34 not subjected to silica modification was prepared and used as a catalyst. The reaction results are shown in Table 1.

Comparative Example 4 The main reaction was carried out using the catalyst 5 at a temperature of 320 ° C., a pressure of 2 MPa and a space velocity (GHSV: 1 / h) 900. Similarly, a disproportionation reaction was performed using the catalyst 4 at a space velocity (GHSV: 1 / h) of 500. The reaction results are shown in Table 1.

Comparative Example 5 20 ml of catalyst 6 was used in the main reactor, and 4 silica-alumina catalysts (NH-H3N manufactured by Nitto Chemical Co., Ltd.) were used in the sub-reactor.
ml, and in any reactor, pressure 2MP
a) The reaction was carried out at a temperature of 320 ° C. The outline of the reaction process is shown in FIG. Methanol and ammonia, and ammonia containing methylamines circulated from the distillation system were supplied to the main reactor at a space velocity (GHSV: 1 / h) of 1550. Monomethylamine and trimethylamine separated and recovered in the distillation system were supplied to the sub-reactor by SV800. Table 2 summarizes the material balance of the process fluid. At this time, the amount of dimethylamine produced was 6.0 g / hour.

[0035]

[Table 1] List of reaction results of Examples and Comparative Examples Conversion selectivity Catalyst temperature GHSV MeOH / Monomeramine MMA DMA TMA ° C 1 / h% (wt%) Example 1 Main reaction Catalyst 1 320 1500 99.4 35 63 2 Disproportionation catalyst 1 320 500 80.0 99 1 Example 2 main reaction catalyst 2 320 1500 98.6 38 60 2 disproportionation catalyst 2 320 500 78.8 97 3 Example 3 main reaction catalyst 3 320 1500 99.6 37 62 1 disproportionation catalyst 3 320 500 79.2 98 2 Example 4 Main Reaction Catalyst 4 320 1500 98.5 35 60 5 Disproportionation Catalyst 4 320 500 80.0 98 2 Comparative Example 1 Main Reaction SAPO-34 320 1500 83.0 30 30 40 Disproportionation SAPO-34 320 500 71.0 91 9 Comparative Example 2 Main reaction CoSAPO-34 320 1500 88.0 33 30 34 Disproportionation CoSAPO-34 320 500 67.5 92 8 Comparative Example 3 Main reaction TiSAPO-34 320 1500 76.5 32 28 40 Disproportionation TioSAPO-34 320 500 67.5 92 8 Comparative Example 4 Main reaction Catalyst 5 320 900 97.0 35 63 2 Disproportionation Catalyst 5 320 500 67.2 69 31 Main reaction: Reaction of methanol with ammonia Disproportionation: Disproportionation of monomethylamine reaction

[0036]

[Table 2] As shown in Table 1, it is understood that dimethylamine can be produced more advantageously according to the present invention than in the conventional production method. Furthermore, when Example 1 and Comparative Example 5 described in Table 2 are compared with each other, a remarkable effect is obtained on an increase in the production amount of dimethylamine as compared with the conventional process and a reduction in the process circulation amount when compared with the same production amount. It is clear that there is.

[0037]

As described above, the productivity of dimethylamine can be greatly improved, and the selectivity and activity of the catalyst are high, so that there is no need to recover the unreacted raw material and the load of distillation is greatly reduced. Occurs. As a result, it is possible to simplify the manufacturing process, reduce the number of devices, reduce the size of devices and improve productivity. Therefore, the present invention is a process for producing dimethylamine which is industrially excellent and has high price competitiveness, and its significance is extremely large.

[Brief description of the drawings]

FIG. 1 is an outline of the reaction steps used in Example 5 and Comparative Example 5.

[Explanation of symbols]

 1; flow path (supply of raw material to main reactor) 2: flow path 3; flow path (supply of raw material to sub-reactor) 4: flow path 5; flow path (trimethylamine) 6; flow path (dimethylamine)

Claims (7)

[Claims] 1. A method for producing dimethylamine from methanol and ammonia, the method comprising the step of producing methylamines containing monomethylamine and dimethylamine from a raw material mainly comprising methanol and ammonia in the presence of a catalyst. And step 2 of disproportionating monomethylamine obtained in step 1 to dimethylamine by disproportionation in the presence of a catalyst, and in at least one of step 1 and step 2, a silica-modified crystalline silicoaluminophosphate as a catalyst A method for producing dimethylamine, comprising using a molecular sieve. 2. The process according to claim 1, wherein a silica-modified crystalline silicoaluminophosphate molecular sieve is used as a catalyst in both Step 1 and Step 2. 3. The method according to claim 1, wherein the effective pore size of the silica-modified crystalline silicoaluminophosphate molecular sieve as a catalyst is in the range of 0.3 to 0.6 nm. 4. A silica-modified crystalline silicoaluminophosphate molecular sieve as a catalyst is SAPO-1
1, 17, 18, 26, 31, 33, 34, 35, 4
3. At least one selected from 2, 43, 44, 47 and 56 is a main component.
Production method as described. 5. The silica-modified crystalline silicoaluminophosphate molecular sieve is H-type or a part of H-type is Li, Ti, Zr, V, Cr, Mn, Fe, Co, Z
The method according to claim 1, wherein the method is substituted with an atom selected from n, Be, Mg, Ca, B, Ga, and Ge. 6. The method according to claim 1, wherein the silica-modified crystalline silicoaluminophosphate molecular sieve has been silica-modified by depositing, precipitating or coating silicon atoms on the surface before silica-modification. 7. The method according to claim 1, wherein the silica-modified crystalline silicoaluminophosphate molecular sieve has been silica-modified using at least one selected from alkoxysilane and halogenated silane.