KR100564358B1 - Solid acid catalyst for preparing dimethylether in high yield and method for preparing dimethylether using the same - Google Patents

Abstract

The present invention relates to a solid acid catalyst for preparing high yield dimethyl ether and a method for preparing dimethyl ether using the same. Specifically, K-SUZ-4 (K ₅ Al ₅ Si ₃₁ O ₇₂ ) zeolite is ion-exchanged several times with an aqueous solution of ammonium salt to obtain K. Dimethyl ether, characterized in that dimethyl ether is prepared by dehydrating methanol in the presence of a catalyst composed of HK-SUZ-4 having an amount of ions ranging from 0.1 to 0.9 in an atomic ratio with respect to Al present in the catalyst. It relates to a manufacturing method.

The solid acid catalyst for preparing dimethyl ether of the present invention exhibits reaction activity in a wide temperature range and is excellent in dimethyl ether selectivity. In addition, when the solid acid catalyst is used for the production of dimethyl ether by dehydration of methanol, it is possible to stably maintain a high methanol conversion rate even when the reaction is performed for a long time more than 10,000 hours from the beginning of the reaction while using a smaller amount of catalyst than a conventional catalyst. On the other hand dimethyl ether can be prepared with almost 100% selectivity.

Dimethyl ether, solid acid catalyst, methanol, dehydration reaction, zeolite.

Description

SOLID ACID CATALYST FOR PREPARING DIMETHYLETHER IN HIGH YIELD AND METHOD FOR PREPARING DIMETHYLETHER USING THE SAME}

It relates to a solid acid catalyst for producing high yield dimethyl ether and a method for producing dimethyl ether using the same.

Dimethyl ether is an oxygen-containing compound that has recently attracted attention because its physical and chemical properties are similar to, or rather superior to, LPG, and can be used as an aerosol propellant, a substitute for diesel fuel, and an intermediate of chemical reactions.

The typical method of preparing dimethyl ether is to react methanol with a concentrated sulfuric acid catalyst. This method is expensive to regenerate sulfuric acid, and due to the nature of sulfuric acid, there is a risk of explosion by reacting with water generated during the reaction. There is a problem.

While overcoming these shortcomings, the main method for producing dimethyl ether on an industrial scale is to dehydrate methanol using a solid acid dehydration catalyst in a fixed bed reactor and distill the product to the extent required by the aerosol field. It is a method of recovering high purity dimethyl ether.

Acid catalysts are mainly used for dehydration of methanol, and examples thereof include alumina, zeolite, silica / alumina, metal salts, ion exchange resins, mixed metal oxides, and the like. Many studies have been conducted to improve the performance of these acid catalysts. In most cases, strong acid sites that produce by-products are poisoned with alkali metals, or heat treatment methods are used to control the amount of acid sites to suppress side reactions as much as possible, or active elements It was attempted to improve the yield and selectivity of dimethyl ether by loading in gamma-alumina. As an example, US Pat. No. 4,595,785 discloses dehydration of methanol at 1034 kPa, 400 ° C. using a catalyst having 1% titania loaded on gamma-alumina to give 57.5% dimethyl ether, 20% methanol and A condensation product was obtained comprising 22.5% water.

Dubois (JL Dubois) and the like used a commercial HY zeolite as it is, but HY zeolite has a strong acid point (pKa -8.2) has a problem of generating hydrocarbon by-products such as methane, ethane, propane [ Chem. Lett. , 1115 (1992). Hydrocarbons produced as by-products, as a low molecular weight alkanes, have a low value as a product, and have a problem in that separation of carbon dioxide from the product after the reaction is difficult.

In Korean Patent Laid-Open Publication No. 1999-0031451, in order to solve these problems, Y-type zeolite treated with a suitable metal cation so that the strength of the strong acid point is approximately -6.0 to -3.0 as pKa value is used as a catalyst. There was a problem of lowering.

Currently gamma alumina (γ-alumina), which has excellent reaction activity and dimethyl ether selectivity, is used in a wide temperature range, but gamma alumina has a characteristic of rapidly decreasing reaction activity by water. And other metal ions such as Si have been studied [ Bull. Korean Chem. Soc. , 23, 803 (2002). On the other hand, H-ZSM-5 has a higher reaction activity than gamma alumina, and even though water is present, water inhibits the formation of by-products such as hydrocarbons. Since the activity was so strong, the reaction proceeded further in dimethyl ether, which prevented the formation of by-products such as hydrocarbons. For this reason and to increase the resistance at the reaction temperature, research has been reported to properly control the acidity of the solid acid by poisoning H-ZSM-5 with ammonia [ Appl. Catal. A , 149, 289 (1997).

An object of the present invention is to solve the above problems, and in particular, to provide a solid acid catalyst excellent in reaction activity and dimethyl ether selectivity in a wide temperature range.

It is also an object of the present invention to provide a method for producing dimethyl ether using the solid acid catalyst.

In order to achieve the above object, the present invention ion-exchanged K-SUZ-4 (K ₅ Al ₅ Si ₃₁ O ₇₂ ) zeolite several times with an aqueous solution of ammonium salt so that the amount of K ions in atomic ratio to Al present in the catalyst The present invention provides a catalyst for preparing dimethyl ether composed of HK-SUZ-4 ranging from 0.1 to 0.9.

The present invention also provides a process for preparing dimethyl ether from methanol in the presence of the catalyst.

Hereinafter, the present invention will be described in detail.

First, the present invention provides a solid acid catalyst for preparing dimethyl ether having excellent new dimethyl ether selectivity. Specifically, the K-SUZ-4 (K ₅ Al ₅ Si ₃₁ O ₇₂ ) zeolite is ion-exchanged several times with an aqueous ammonium salt solution, whereby the amount of K ions is in the range of 0.1 to 0.9 in atomic ratio with respect to Al present in the catalyst. Provided is a catalyst for preparing dimethyl ether composed of SUZ-4.

The K-SUZ-4 (K ₅ Al ₅ Si ₃₁ O ₇₂ ) zeolite used a catalyst patented by the British Petroleum Company (US Pat. No. 5,118,483).

The aqueous ammonium salt solution is used to properly raise the acid point, which is a function of the dehydration reaction of the catalyst through ion exchange treatment. At this time, available ammonium salts are tetraalkylammonium hydroxide {(C _n H _{2n + 1} ) ₄ NOH, 1≤n≤6}, tetraalkylammonium salt {(C _n H _{2n + 1} ) ₄ NX, X = F , Cl, Br, and 1 ≦ n ≦ 6} are preferred, most preferably tetraethylammonium hydroxide.

The HK-SUZ-4 zeolite of the present invention performs the ion exchange process of drying and calcining the K-SUZ-4 zeolite using an aqueous ammonium salt solution, followed by several times, and thus obtained HK-SUZ-4 zeolite K ranges from 0.1 to 0.9 in atomic ratio with respect to Al present in the catalyst. Since the dehydration activity of methanol depends on the amount of acid point, if the ratio is less than 0.1, there is some strong solid acid point, so the activity is strong, so that the dehydration reaction proceeds further in dimethyl ether to produce by-products such as hydrocarbons or coke. There is a problem that can not be suppressed, if the ratio exceeds 0.9 there is a disadvantage that the dehydration activity is too low to perform a function as a catalyst. Since HK-SUZ-4 has an appropriate solid acid point, it can exhibit reaction activity in a wide temperature range and has excellent dimethyl ether selectivity.

The present invention also provides a method for preparing dimethyl ether by dehydrating methanol in the presence of the catalyst of HK-SUZ-4 zeolite.

The production method is usually carried out using a reactor for the production of dimethyl ether. Specifically, the HK-SUZ-4 zeolite catalyst is uniformly mixed and then charged into the reactor, and the catalyst is activated at a constant temperature while flowing nitrogen gas. The dimethyl ether production reaction is then reacted with nitrogen gas and methanol gas given the reaction temperature and space velocity.

At this time, the reaction temperature is preferably 200 ~ 350 ℃, when the temperature is less than 200 ℃ there is a problem that the conversion of methanol is lowered, when the temperature exceeds 350 ℃ tends to slightly decrease the dimethyl ether selectivity.

The space velocity is preferably 4 to 100 h ^{−1, but} when it is less than the above range, the reaction productivity is too low, and when it exceeds the above range, there is a problem that the conversion rate is lowered because the contact time with the catalyst is shortened.

In addition, the reactor may be a gas phase fixed bed reactor, a fluidized bed reactor, or a reactor in the form of a slurry in a liquid phase, and any of these may be used to obtain the same effect.

By using the catalyst of the present invention, the method for producing dimethyl ether of the present invention, while using a small amount of the catalyst compared to the existing catalyst, while reacting for a long time from the beginning of the reaction to maintain a high methanol conversion rate while maintaining a nearly 100% selectivity of dimethyl Ethers can be prepared.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the scope of the present invention is not limited thereto.

Preparation Example 1 Preparation of K-SUZ-4 Zeolite

After dissolving 3.29 g of KOH in 50 ml of water, 0.4 g of aluminum foil was added and stirred for 12 hours until a clear solution was obtained at 60 ° C. 7.93 g of tetraethylammonium hydroxide (TEAOH) was added to the solution and stirred for 1 hour. 18.2 g silica sol containing 40 wt% SiO ₂ was added to the solution and stirred for 1 hour. The solution was hydrothermally reacted for 48 hours while stirring at 500 rpm in a 165 ° C. oven. The product obtained after filtration was washed with distilled water until the pH was neutral, and dried at 120 ° C. for 12 hours. The dried product was calcined at 550 ° C. to obtain K-SUZ-4 (K ₅ Al ₅ Si ₃₁ O ₇₂ ) having excellent crystals.

Example 1 Preparation of HK-SUZ-4 Zeolite of the Present Invention

10 g of K-SUZ-4 (K ₅ Al ₅ Si ₃₁ O ₇₂ ) zeolite was added to 100 ml of a 1N NH ₄ NO ₃ aqueous solution, and stirred at 80 ° C. for 24 hours. After filtration and washing with distilled water, it was dried at 120 ° C. and calcined at 500 ° C. three times to obtain HK-SUZ-4 (H _3.8 K _1.2 Al ₅ Si ₃₁ O ₇₂ ) zeolite.

Example 2 Preparation of Dimethyl Ether 1

0.2 g of HK-SUZ-4 zeolite of Example 1 was taken, mixed uniformly, and charged to a fixed bed reactor. In this state, while flowing nitrogen gas at a flow rate of 50 ml / min, the solid acid catalyst was activated at a temperature of 500 ° C.

The dimethyl ether production reaction was passed through the catalyst layer while injecting methanol with a nitrogen carrier gas of 360 ml / h at a space velocity of 4 h ⁻¹ at 250 ° C., and the reaction results obtained are shown in Table 1 below. .

Example 3 Preparation of Dimethyl Ether 2

The reaction was carried out in the same manner as in Example 2 except that the reaction temperature was 300 ° C. when methanol was passed through the catalyst layer for reaction. The obtained reaction results are shown in Table 1 below.

Example 4 Preparation of Dimethyl Ether 3

The reaction was carried out in the same manner as in Example 2 except that the reaction temperature when the reaction was carried out by passing methanol through the catalyst layer was performed at 200 ° C. The obtained reaction results are shown in Table 1 below.

Example 5 Preparation of Dimethyl Ether 4

In the same manner as in Example 2, methanol was passed through the catalyst layer while being injected with a nitrogen carrier gas of 360 ml / h at a space velocity of 32 h ⁻¹ , and the reaction results obtained are shown in Table 1 below. .

Example 6 Preparation of Dimethyl Ether 5

The catalyst was prepared in the same manner as in Example 2, except that 300 ml of water was used during the hydrothermal reaction during preparation of K-SUZ-4 in Preparation Example 1. The obtained reaction results are shown in Table 1 below.

Example 7 Preparation of Dimethyl Ether 6

The catalyst was prepared in the same manner as in Example 2, but using a catalyst obtained at 250 rpm during the K-SUZ-4 preparation heavy hydrothermal reaction of Preparation Example 1. The obtained reaction results are shown in Table 1 below.

Example 8 Preparation of Dimethyl Ether 7

In the same manner as in Example 2, HK-SUZ-4 (H ₃ K ₂ Al ₅ Si ₃₁ O ₇₂ ) zeolite obtained by repeating the ion exchange process twice was used. The obtained reaction results are shown in Table 1 below.

Comparative Example 1

KH-ZSM-5 type zeolite obtained by performing ion exchange with 10 g of H-ZSM-5 zeolite (Si / Al = 30) as a catalyst in 100 ml of 1N KNO ₃ aqueous solution once K / Al atomic ratio = 0.4) was used, the reaction results are shown in Table 1 below.

Comparative Example 2

In the same manner as in Example 2, but using a non-ion exchanged H-ZSM-5 zeolite (Si / Al = 30) as a catalyst, the reaction results are shown in Table 1 below.

Comparative Example 3

In the same manner as in Example 2, but H-ZSM-5 zeolite (Si / Al = 30) poisoned with nitrogen-containing basic as a catalyst was used, the reaction results are shown in Table 1 below.

<Comparative Example 4>

The same method as in Example 2 was carried out, but K-SUZ-4 (K ₅ Al ₅ Si ₃₁ O ₇₂ ) zeolite which was not ion-exchanged was used as a catalyst, and the obtained reaction results are shown in Table 1 below.

division 10 hours response 100 hours reaction 1000 hours reaction % Conversion Selectivity (%) % Conversion Selectivity (%) % Conversion Selectivity (%) Example 2 86.2 100 86.8 100 85.5 100 Example 3 83.4 100 82.4 100 79.1 100 Example 4 88.2 100 89.6 100 89.2 100 Example 5 86.3 100 86.6 100 83.4 100 Example 6 86.3 100 86.6 100 85.4 100 Example 7 81.1 100 82.3 100 78.0 100 Example 8 77.3 100 79.3 100 78.2 100 Comparative Example 1 45.1 100 45.9 98.3 45.4 90.2 Comparative Example 2 85.8 98.2 27.5 99.5 0 - Comparative Example 3 78.2 100 82.2 98.4 67.2 100 Comparative Example 4 1.4 100 1.4 100 1.4 100

Table 1 shows the reaction results of Examples 2-8 and Comparative Examples 1-4.

According to an embodiment of the present invention, the HK-SUZ-4 zeolite catalyst prepared from K-SUZ-4 (K ₅ Al ₅ Si ₃₁ O ₇₂ ) zeolite by a conventional ion exchange method is used to prepare dimethyl ether from methanol under given reaction conditions. When prepared, as shown in Comparative Example 1, it is possible to prepare dimethyl ether with high methanol conversion and 100% selective as compared with the conventional KH-ZSM-5 zeolite catalyst poisoned with H-ZSM-5 zeolite. This is due to the high methanol conversion and 100% selective dimethyl conversion of K-SUZ-4 (K ₅ Al ₅ Si ₃₁ O ₇₂ ) zeolites, through the proper control of the acid point by the K ions contained in the small 6-holes of pores. Ether is prepared.

Meanwhile, the KH-ZSM-5 zeolite catalyst poisoned with H-ZSM-5 zeolite shows low methanol conversion and low selectivity to dimethyl ether despite the presence of K ions as shown in Comparative Example 1. On the other hand, as shown in Comparative Example 2, when using the non-poisoned solid acid catalyst, it shows a relatively high methanol conversion initially compared to the poisoning treatment, but the conversion rate decreases rapidly with time. In addition, when using a solid acid catalyst poisoned with nitrogen-containing basic as shown in Comparative Example 3, the initial conversion of methanol shows a 78% methanol conversion rate, but gradually increases and decreases gradually with time.

In addition, as shown in Comparative Example 1, when a large amount of poisoning treatment to the solid acid catalyst, there is a problem that the methanol conversion is greatly reduced.

As described above, the solid acid catalyst for preparing dimethyl ether of the present invention is ion-exchanged K-SUZ-4 (K ₅ Al ₅ Si ₃₁ O ₇₂ ) zeolite several times with an aqueous solution of ammonium salt so that the amount of K ions is present in the catalyst. By composition with HK-SUZ-4 in the range of 0.1 to 0.9 in atomic ratio, the reaction activity is exhibited in a wide temperature range compared to the solid acid catalyst for producing dimethyl ether, and the dimethyl ether selectivity is excellent. In addition, when the solid acid catalyst is used for the production of dimethyl ether by dehydration of methanol, it is possible to stably maintain a high methanol conversion rate even when the reaction is performed for a long time more than 10,000 hours from the beginning of the reaction while using a smaller amount of catalyst than a conventional catalyst. On the other hand dimethyl ether can be prepared with almost 100% selectivity.

Claims (5)

K-SUZ-4 (K ₅ Al ₅ Si ₃₁ O ₇₂ ) The zeolite is ion-exchanged two or more times with an aqueous ammonium salt solution, where the amount of K ions is in the range of 0.1 to 0.9 in atomic ratio with respect to Al present in the catalyst. A catalyst for the production of dimethyl ether, characterized in that composed of 4. The ammonium salt in the aqueous ammonium salt solution is tetraalkylammonium hydroxide {(C _n H _{2n + 1} ) ₄ NOH, 1≤n≤6} and tetraalkylammonium salt {((C _n H _{2n + 1} ) ₄ NX, X = F, Cl, Br, and 1≤n≤6} catalyst for the production of dimethyl ether, characterized in that selected from the group consisting of. Method for producing dimethyl ether, characterized in that to produce dimethyl ether by dehydration of methanol in the presence of the catalyst of claim 1. The method for producing dimethyl ether according to claim 3, wherein the reaction temperature is 200 to 350 ° C. The method for producing dimethyl ether according to claim 3, wherein the methanol has a space velocity of 4 to 100 h ⁻¹ .