KR20040017491A - Method for preparing synthesis gas from dimethyl ether - Google Patents

Abstract

PURPOSE: A method for preparing synthetic gas through steam reforming of dimethyl ether by using commercial reforming catalyst containing a principal constituent of nickel is provided. CONSTITUTION: The method for preparing synthetic gas from dimethyl ether comprises the process of preparing synthetic gas by steam reforming dimethyl ether or dimethyl ether mixed raw material at a reaction temperature of 200 to 900 deg.C under a reforming catalyst containing 5 to 40 wt.% of a principal constituent of nickel and subsidiary constituents of alkali metal and alkali earth metal, wherein a mole ration of carbon in dimethyl ether for steam is 1:0.5 to 6, wherein a principal constituent of the obtained synthetic gas is hydrogen, and wherein the dimethyl ether mixed raw material comprises at least one raw material selected from the group consisting of naphtha containing 1% or more of dimethyl ether, LPG (liquefied petroleum gas), LNG (liquefied natural gas), methane, ethane, propane, butane, methanol, and ethanol.

Description

Method for preparing synthesis gas from dimethyl ether

The present invention relates to a method for preparing a synthesis gas from dimethyl ether (DME), and more particularly, steam reforming or carbon dioxide-vapor reforming of dimethyl ether using a reforming catalyst based on nickel. The present invention relates to a method for producing a synthesis gas having a high hydrogen content by reforming (CO ₂ -steam reforming).

Syngas is a C1 chemical raw material, carbon monoxide and hydrogen, or various mixtures of nitrogen and hydrogen, mainly derived from natural gas and naphtha, but in fact a city containing coal, peat, wood, biomass, agricultural debris, and by-product gases from various industries. It can be made from almost any carbon-containing material, including waste.

In addition, dimethyl ether, which is the main compound of C1 chemistry, has been studied for a long time with methanol, but its main uses have been olefin production, MTG (Methanol to Gasoline), spray propulsion of spray, and methyl acetate synthesis. .

However, when used as a fuel for diesel engines, dimethyl ether is noticed as a new automobile fuel that can replace diesel fuel due to the fact that the amount of smoke generated is significantly reduced and NO _x is not generated, and LPG and gas characteristics are similar. Therefore, it can be spread through the infrastructure of LPG, attracting attention as a fuel for household or power generation that can replace LPG. In addition, recently, various applications such as dimethyl ether to be used as a raw material of petrochemical process and fuel of fuel cell have been developed.

As mentioned above, dimethyl ether is an eco-friendly clean energy that converts natural gas from small-scale undeveloped natural gas fields that are economically disadvantageous to develop into LNG, or low-cost coal, into a form that can be stored and easily transported. Methanol production process and production processes of NKK and Halder Topsoe A / S (US Pat. Nos. 5,466,720, 5,389,689, 5,218,003). Production was possible at a price point that could compete with other energy sources.

On the other hand, a technique for producing a synthesis gas or hydrogen through a steam reforming reaction of hydrocarbons is a widely used technique, including methane, ethane, propane, butane, low molecular weight alkanes, methanol, ethanol, petrochemical process Naphtha is used as a feedstock, and it is widely used in small-scale fuel cells that generate electricity from hydrogen as fuel.

Accordingly, a technology for preparing dimethyl ether, an economical and environmentally friendly energy source as described above, in the form of syngas through steam or carbon dioxide-steam reforming, and separating and using hydrogen and carbon monoxide generated, has been newly developed. As an early stage, patents and documents are very rare.

The related art is as follows.

In US Patent No. 5,626,794 to Amoko Corporation, a synthesis gas is prepared by hydrolysis of dimethyl ether using a copper / zinc-based catalyst that does not contain alkali metals, followed by aqueous reaction in a series of reactors. A method of using syngas as a raw material of a combustor is disclosed for the first time in a hydroshifting process connected to a water-gas shift.

Later, U.S. Patent No. 5,837,217 to Nielsen et al., Haldor Topsoe A / S, used a H-type ZSM-5 catalyst to react water with dimethyl ether. After the production of methanol, a process of preparing a synthesis gas by physically mixing two steam reforming catalysts in a general methanol reforming catalyst, a copper / zinc / alumina catalyst (Cu / Zn / Al ₂ O ₃ ), was introduced. Galvita et al. Reported a method for producing syngas using a similar method, followed by methanol production through hydration of dimethyl ether followed by copper-based methanol reforming catalysts.

As described above, the conventional method for producing synthesis gas or hydrogen by dimethyl ether steam reforming is a method of mixing dimethyl ether with methanol and a catalyst having a different mechanism for methanol reforming. When the two catalysts are packed in one reactor, the temperature difference according to the characteristics of each catalyst can be brought about, which can reduce the lifetime of the reactor. In order to remove the adverse effect of the mixing, the catalysts must be separated into separate reactors. Therefore, there is a disadvantage such as an increase in device cost.

Meanwhile, in the steam reforming reaction of hydrocarbons such as naphtha, LPG and methane, nickel catalysts containing alkali metals such as sodium and potassium, alkaline earth metals such as calcium, or silica as cocatalysts are generally used to prevent carbon generation. Although it is used, a method of producing a synthesis gas or hydrogen by steam reforming dimethyl ether using such a nickel catalyst, or a method using another series of catalysts has not been introduced.

Therefore, in the present invention, conventional reforming catalysts, that is, nickel, are used as a main component, and a catalyst containing a trace amount of alkali earth metals such as calcium and sodium as a cocatalyst to prevent carbon formation is used. By using dimethyl ether as a raw material without changing the reforming process it was confirmed that the synthesis gas or hydrogen can be obtained with a high conversion and selectivity, the present invention was completed based on this.

Accordingly, it is an object of the present invention to provide a method for producing syngas through steam reforming of dimethyl ether using a commercially available reforming catalyst based on nickel.

In order to achieve the above object, the method for producing a synthesis gas from the dimethyl ether of the present invention is 200 to 900 under a reforming catalyst containing 5 to 40% by weight of nickel as a main component, and an alkali metal and alkaline earth metal as an auxiliary component Steam reforming of dimethyl ether or dimethyl ether mixed raw materials at a reaction temperature of < RTI ID = 0.0 >

1 is a schematic flowchart of preparing a synthesis gas from dimethyl ether according to an embodiment of the present invention.

◎ Explanation of symbols for main part of drawing

One … Dimethyl ether 2... Other raw materials

3…. Water vapor 4.. carbon dioxide

5... Pre-reforming unit 6... Main reformer

7. Water-gas shifting unit

8 … Synthesis gas 9.. Gas Purifier (PSA unit)

10... Purified hydrogen or carbon dioxide 11... Waste gas after purification

Hereinafter, the present invention will be described in more detail.

As described above, the present invention relates to a method for preparing a synthesis gas through a reforming reaction of dimethyl ether, and more specifically, to a conventional steam reforming commercial catalyst, ie, nickel as a main component, and to prevent carbon generation. A method for producing syngas or hydrogen using a catalyst containing an alkali metal such as sodium and potassium and an alkaline earth metal such as calcium as a cocatalyst and dimethyl ether as a raw material without changing the structure of an existing reforming reaction process. will be.

In the syngas production method of the present invention, the catalyst is a catalyst containing 5 to 40% by weight of nickel as the main component, and alkali metal and alkaline earth metal as the auxiliary component, in the presence of the catalyst, dimethyl ether and water (steam) Or by contacting water with carbon dioxide (CO ₂ ). In this case, the temperature of the dimethyl ether steam reforming reaction is 200 to 900 ° C, preferably 500 to 900 ° C, more preferably 750 to 850 ° C.

In the steam reforming reaction of the present invention, the molar ratio of water vapor to 1 mole of dimethyl ether is 1 to 12, which is expressed in terms of the steam to carbon ratio of steam to conventionally used 1: 0.5 to 6, preferably Preferably 1: 2.5 to 5. If the molar ratio is less than 0.5, the conversion rate is reduced, and carbon may be generated in the catalyst, thereby degrading catalytic activity. If the molar ratio is greater than 6, the amount of heat for evaporating water into water vapor is more economical than the aspect of improving reactivity. Is disadvantageous.

Meanwhile, in the present invention, the dimethyl ether is mixed with naphtha, LPG, LNG, methane, ethane, propane, butane, methanol, ethanol, and the like, which are used as feedstocks of a conventional hydrogen plant, and the nickel is used as a main component. Hydrogen may be obtained by reaction under a reforming catalyst containing an earth metal as an auxiliary component. In this case, 1% or more of dimethyl ether is contained in the mixed raw material. At this time, one embodiment of the steam reforming reactor used is as shown in FIG.

Referring to Figure 1 in more detail, the dimethyl ether (1), other fuels such as naphtha (2), water vapor (3), and carbon dioxide (4) is supplied to the developing device (5), main reforming device (6) ), And then through the water gas conversion device (7) in order to obtain a synthesis gas (8), and then passed through the gas purification device (9) to obtain purified hydrogen or carbon dioxide (10), and the remaining waste gas (11) after purification ) Is discharged. The main reforming unit 6 is in particular a main reforming reactor comprising the catalyst mentioned in the present invention, in which the main reforming unit can be any combination possible with the developing unit, the water gas shifter and the gas purification unit. It includes.

In the present invention, naphtha, propane, butane, LPG, and the like, which are used as feedstocks of the hydrogen plant in the petrochemical process, are generally decomposed into a mixture of methane and hydrogen, carbon monoxide, carbon dioxide, and the like in the developing apparatus to the main reformer (6). For comparison with respect to the point of introduction, the heat of reaction required for steam reforming and methane steam reforming of the dimethyl ether of the present invention and the heat of reaction required per hydrogen unit were calculated, and the results are shown in Table 1 below.

Raw material Steam reforming scheme Reaction heat methane CH ₄ + 2H ₂ O ↔ CO ₂ + 4H ₂ ΔH ^o = 165.12 kJ / mol Dimethyl ether CH ₃ OCH ₃ + 3H ₂ O ↔ 2CO ₂ + 6H ₂ ΔH ^o = 122.66 kJ / mol Required heat ratio (dimethyl ether 1 mole reaction heat / methane 1 mole reaction heat) 0.74 Reaction heat ratio required for the production of equivalent hydrogen ^* 0.49

*: The heat of reaction required to prepare 1 mole of hydrogen from dimethyl ether

As can be seen from Table 1, dimethyl ether steam reforming is lower than the heat of reaction required for steam reforming of the shortest alkanes methane, it is possible to reduce the load of the heater and burner of the reforming reactor.

In addition, when dimethyl ether was steam-modified to apply a feedstock for a hydrogen plant in a petrochemical process, unit hydrogen cost was evaluated and compared, and the results are shown in Table 2 below.

$ / MSCF H ₂ Won / NM3 H ₂ Heavy naphtha 1.91 87.8 Hard naphtha 2.18 99.9 Propane 2.94 135.2 butane 2.99 137.4 Dimethyl ether 1.18 54.0

Based on 2000 winter hydrogen plant raw material price, dimethyl ether: 27.3 MM BTU / Ton, 4 $ / MMBTU

As can be seen from Table 2, dimethyl ether was evaluated to be more economical than other raw materials in a hydrogen production plant.

In addition, according to the present invention, it is possible to obtain a synthesis gas having a high hydrogen content, which is suitable for ammonia production process requiring a high hydrogen content or a synthesis gas process for producing a high concentration of hydrogen.

As described above, dimethyl ether steam reforming or carbon dioxide-steam reforming reaction using a commercial nickel-based catalyst according to the present invention showed high conversion of dimethyl ether to syngas, and also had high hydrogen selectivity. Compared to methane reforming, the heat of reaction consumption required for the production of the same amount of hydrogen is about half the level, which is excellent in terms of energy efficiency.

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

Example

Throughout the examples, a reformer reactor filled with a steam reforming catalyst, a pump for supplying water and a steam generator, a condenser for removing unreacted steam, and an analysis device for analyzing the reactant were used.

The water is heated to the presence of steam at the reaction pressure and fed to the reforming reactor together with the dimethyl ether gas heated above the steam temperature to prevent condensation of the steam. Synthetic gas containing hydrogen, carbon dioxide, carbon monoxide, trace methane, etc. generated in the reforming reactor passes through a heat exchanger for preheating dimethyl ether, and after separating the liquid containing unreacted water vapor through a condenser kept at low temperature, It was introduced into the gas analyzer which is analyzed by.

Example 1

Under a magnesia / alumina modified catalyst containing 12% by weight of nickel and a silica as a cocatalyst (hereinafter referred to as catalyst A), the water vapor to carbon ratio (S: C) was fixed at 1.5, followed by the conversion and selection according to the reaction temperature. Figures were measured and the results are shown in Table 3 below.

S: C (steam to carbon ratio) 1.5 1.5 1.5 1.5 1.5 Temperature (℃) 500 600 700 800 830 % Conversion 100.0 100.0 100.0 100.0 100.0 Selectivity (%) CO 3.4 25.9 63.8 86.1 81.2 CO ₂ 38.0 33.5 16.5 8.0 11.1 CH ₄ 58.6 40.6 19.7 5.9 7.6 H ₂ 29.0 56.1 82.1 94.4 94.1 Product (mol%) on dry base CO 2.3 12.7 22.8 28.6 23.7 CO ₂ 25.7 16.5 5.9 2.6 3.2 H ₂ 32.4 50.9 64.3 66.7 70.8 CH ₄ 39.6 19.9 7.0 2.0 2.2

As can be seen from Table 3, the dimethyl ether is completely converted to the synthesis gas at a temperature of less than 500 ℃, more preferably at a temperature of 400 ℃ or more in the previous experiment, the content of methane increases as the reaction temperature increases Decreased, and the hydrogen content and selectivity increased.

Example 2

Under catalyst A of Example 1, the reaction temperature was fixed at 800/830 ° C., and the conversion and selectivity according to the water vapor to carbon ratio were measured, and the results are shown in Table 4 below.

S: C 1.5 2 2.5 3 1.5 2 2.5 3 Temperature (℃) 800 800 800 800 830 830 830 830 % Conversion 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 Selectivity (%) CO 86.1 79.3 70.8 70.7 81.2 82.4 68.6 64.4 CO ₂ 8.0 17.0 28.1 28.1 11.1 14.7 30.2 35.2 CH ₄ 5.9 3.8 1.2 1.2 7.6 2.9 1.2 0.4 H ₂ 94.4 96.8 99.2 99.2 94.1 97.8 99.2 99.7 Product (mol%) dry matter basis CO 28.6 24.4 18.1 17.8 23.7 22.5 17.6 16.8 CO ₂ 2.6 5.2 7.2 7.1 3.2 4.0 7.8 9.2 H ₂ 66.7 69.2 74.4 74.8 70.8 72.7 74.3 74.0 CH ₄ 2.0 1.2 0.3 0.3 2.2 0.8 0.3 0.1

As can be seen from Table 4, dimethyl ether was completely converted to syngas under the above conditions, and dimethyl ether was reacted by increasing methane content and increasing hydrogen content and selectivity with increasing steam to carbon ratio. I could confirm that it happened. In addition, the carbon monoxide content and selectivity decreased, since the water vapor-to-carbon ratio was increased, which is converted to carbon dioxide through a water gas conversion reaction, and thus, the content and selectivity of carbon dioxide were relatively increased.

Example 3

Under a modified catalyst containing 15% by weight of nickel as a promoter as calcium (hereinafter referred to as catalyst B), the reaction temperature was fixed at 800/830 ° C, and the conversion and selectivity according to the water vapor to carbon ratio were measured. It is shown in Table 5 below.

S: C 1.5 2 2.5 3 1.5 2 2.5 3 Temperature (℃) 800 800 800 800 830 830 830 830 % Conversion 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 Selectivity (%) CO 87.3 88.0 83.0 63.2 90.7 89.9 73.4 60.9 CO ₂ 4.0 5.3 14.8 36.2 4.3 7.2 26.2 38.9 CH ₄ 8.7 6.7 2.2 0.5 5.0 2.9 0.4 0.2 H ₂ 92.0 94.6 98.3 99.6 96.3 97.8 99.7 99.8 Product (mol%) dry matter basis CO 29.0 26.3 23.5 16.6 25.5 25.0 20.8 16.0 CO ₂ 1.3 1.6 4.2 9.5 1.2 2.0 7.4 10.2 H ₂ 66.8 70.1 71.7 73.7 71.9 72.2 71.6 73.7 CH ₄ 2.9 2.0 0.6 0.1 1.4 0.8 0.1 0.1

As can be seen from Table 5, the dimethyl ether was completely converted to the synthesis gas, it could be confirmed that almost no methane content. The effect of water vapor to carbon ratio was the same as that of Example 2, and as the water vapor to carbon ratio increased, the methane content decreased, the hydrogen content and selectivity increased, and the reaction occurred actively.

As described above, according to the present invention, a conventional commercial reforming catalyst, that is, a reforming catalyst containing nickel as a main component and an alkali metal and an alkaline earth metal as a promoter, can be used to completely convert from dimethyl ether to syngas. It uses dimethyl ether as a raw material without any major changes in steam reforming reactor equipment under commercial nickel catalysts, and reduces the heat required for steam reforming reactions compared to conventional raw materials such as naphtha, thus reducing operating costs, extending reactor life, and improving productivity. Can improve.

Claims (4)

Synthesis gas was prepared by steam reforming dimethyl ether or dimethyl ether mixed raw materials at a reaction temperature of 200 to 900 ° C. under a reforming catalyst containing 5 to 40 wt% nickel as a main component and alkali metal and alkaline earth metal as auxiliary components. How to. The method of claim 1 wherein the molar ratio of carbon in dimethyl ether to water vapor is 1: 0.5 to 6. The method according to claim 1, wherein the main component of the obtained synthesis gas is hydrogen. The method of claim 1, wherein the dimethyl ether mixed raw material comprises at least one selected from the group consisting of naphtha, LPG, LNG, methane, ethane, propane, butane, methanol, and ethanol containing 1% or more of dimethyl ether. How to.