JPH04363141A - Catalyst for catalytic reduction of carbon dioxide and production of methanol using the same - Google Patents

Abstract

PURPOSE:To obtain a catalyst for catalytic reduction of carbon dioxide and to produce methanol with the catalyst. CONSTITUTION:Copper, zinc oxide and magnesium oxide are supported on titanium dioxide as a carrier. The amt. of the magnesium oxide added is increased, formation of carbon monoxide is selectively inhibited and the selectivity of methanol is enhanced.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst for catalytic reduction of carbon dioxide and a method for efficiently producing methanol from carbon dioxide using the catalyst.

More specifically, the present invention comprises a titanium dioxide carrier, a novel solid catalyst in which a copper component, a zinc oxide component, and a magnesium oxide component are supported, and in the presence of this catalyst, a titanium dioxide carrier as shown in the following formula. The present invention relates to a method for efficiently producing methanol from a mixed gas of carbon and hydrogen. CO2+3H2→CH3OH+H2O

0003

[Prior art] Methanol is an important basic chemical;
There is a worldwide demand of approximately 20 million tons per year. Its synthesis uses a mixed gas (synthesis gas) of carbon monoxide and hydrogen, which can be obtained by steam reforming or partial oxidation of natural gas, oil, or coal, as a raw material, using a catalyst under high temperature and high pressure as shown in the following formula. It is synthesized through a reaction, making it a highly complete process for practical use. CO+2H2→CH3OH

[0004] On the other hand, as for methods of synthesizing methanol from sources other than synthesis gas, synthesis from carbon dioxide and hydrogen, for example, has only been studied at the basic research level from an academic standpoint.

[0005]

[Problem to be Solved by the Invention] With the recent expansion of the scale of global industrial and economic activities, environmental destruction on a global level has become an important problem, and countermeasures have begun to be considered worldwide. In particular, the problem of global warming is estimated to have a significant negative impact not only on humanity but also on the earth itself, and efforts are being made to prevent the emission of carbon dioxide into the atmosphere, which is considered the main cause of global warming. There is a strong need to establish countermeasures.

The purpose of the present invention is to establish a new catalyst and process for recycling exhaust carbon dioxide and efficiently converting it into methanol in order to prevent global warming caused by carbon dioxide. It provides a new method for reducing catalysts and efficient methanol synthesis.

[0007]

[Means for Solving the Problems] The catalyst of the present invention that achieves the above object is made of titanium dioxide as a carrier, on which copper, zinc oxide, and magnesium oxide are supported, and the methanol of the present invention. The production method is to catalytically hydrogenate carbon dioxide with hydrogen gas in the presence of such a catalyst to produce methanol. In particular, by using a novel solid catalyst in which copper, zinc oxide, and magnesium oxide are supported on titanium dioxide as a carrier, it is possible to efficiently convert carbon dioxide into methanol through catalytic hydrogenation. The most problematic by-product of this reaction is carbon monoxide, and the key to improving methanol selectivity is how to suppress its formation. In the catalyst of the present invention, the production of carbon monoxide can be suppressed and the methanol selectivity can be improved by adding magnesium oxide to the copper-zinc oxide catalyst supporting titanium dioxide.

The present invention will be explained in detail below. First, the titanium dioxide of the present invention and the copper supported on it,
The catalyst consisting of zinc oxide and magnesium oxide may have any physical form. That is, the form thereof may be arbitrary, such as fine powder, coarse particles, pellets, etc. Further, the surface area may be about 0.1 to 1000 m2/g, and even if pores are present, any size and distribution of pores can be used. Preferably, it is formed into particles with a diameter of about 1.5 mm.

[0009] The amount of copper and zinc oxide supported is arbitrary, but the preferred amount of copper supported is 1 to 30 wt%. Further, the molar ratio of copper/zinc oxide is from 100/1 to 1/100, preferably from 3/1 to 1/3. Magnesium oxide is used in an amount of 10 wt% or less.

In order to produce the catalyst of the present invention, copper, zinc compounds and magnesium compounds are first supported on titanium dioxide. Although a commercially available titanium dioxide carrier may be used as it is, it is preferable to heat the titanium dioxide in advance at a temperature of 150 to 500° C. in order to remove water and impurities.

As the zinc compound and magnesium compound, inorganic acid salts of these metals such as nitrates, sulfates, and chlorides, and organic acid salts such as acetates can be used as appropriate. is preferred. Although nitrates, sulfates, chlorides, and organic acid salts can be used as raw materials for copper, it is similarly preferable to use nitrates and acetates.

[0012] As a method for supporting copper, zinc compounds, and magnesium compounds on titanium oxide, any method such as an impregnation method, a precipitation method, or a physical mixing method can be adopted. Preferably, an impregnation method is used in which a solution containing a zinc compound and a magnesium compound in the ranges described above in terms of zinc oxide and magnesium oxide is used as an impregnation liquid.

Next, the titanium oxide on which copper, zinc compounds and magnesium compounds are supported is fired in an oxygen stream or an air stream. The firing temperature is between 200 and 800C, preferably between 400 and 600C. A catalyst in which supported copper and zinc oxide precursors are decomposed under a hydrogen stream does not necessarily require calcination treatment.

[0014] Regarding the order in which copper, zinc oxide, and magnesium oxide are supported, it is preferable that copper and zinc oxide are first supported at the same time, and then fired, and then the magnesium compound is supported and fired.

The calcined catalyst is subjected to a reduction treatment in a hydrogen stream. The reduction temperature is between 100 and 1000<0>C, preferably between 200 and 600<0>C. Through this reduction treatment, copper metal, which is an active site for the reaction, can be generated.

Next, the production of methanol using the catalyst of the present invention described above will be described. The reaction for producing methanol from a mixed gas of carbon dioxide and hydrogen can be carried out in any manner, and may be a gas phase fixed bed flow system, a gas phase fluidized bed, or a liquid phase suspended bed. It is preferable that the catalyst used is subjected to a hydrogen reduction treatment prior to the reaction, for example after being filled into a reaction tube, but this treatment may be omitted. The conditions for carrying out the present invention, that is, the reaction conditions for synthesizing methanol from a mixed gas of carbon dioxide and hydrogen, are a pressure of normal pressure to 300 kg/cm2, preferably 10 to 100 kg/cm2, and a reaction temperature of 10 kg/cm2.
The temperature is 0 to 400°C, preferably 180 to 300°C. C
The O2/H2 molar ratio is from 1/10 to 3/1, preferably from 1/4 to 1/1. In addition, although the flow rate of the reaction gas is arbitrary, the space velocity of GHSV is 50 to 200.
00h-1 is preferred.

[0017]

[Examples] Examples of the present invention will be described below.

Example 1 Commercially available titanium dioxide was heated and evacuated at 200°C for 1 hour (
This operation is to remove water and impurities from titanium dioxide). After cooling to room temperature, a mixed aqueous solution of copper nitrate and zinc nitrate (the amount of water was half the weight of titanium dioxide) was dropped little by little. This operation was carried out in such a way that titanium dioxide and the aqueous solution were not exposed to the atmosphere. After being left for 1 hour after dropping, the mixture was slowly heated to 120° C. and evacuated to evaporate water.

Next, this was fired under air circulation to decompose the copper and zinc precursors into oxides. Firing at 100℃
The temperature was raised stepwise to 200°C, 300°C, and 400°C for 1 hour each, and then allowed to cool to room temperature. This catalyst was subsequently impregnated with magnesium. That is, after uniformly dropping an aqueous magnesium nitrate solution, it was dried at 100°C (magnesium nitrate is decomposed by the hydrogen reduction performed later and becomes magnesium oxide). As described above, this catalyst was filled into a reaction tube and used for the reaction after hydrogen reduction treatment.

Example 2 CO2 methanol was added to the reaction tube of a fixed bed pressurized flow reactor.
The titania produced in Example 1 as a catalyst for conversion to
TiO2), copper, zinc oxide (copper loading 5wt%, copper/zinc oxide molar ratio 1:1) and magnesium oxide 1wt%
1 g of the catalyst supporting the above was charged. Prior to the reaction, the catalyst was subjected to hydrogen reduction treatment at 350°C for 30 minutes. After cooling in a hydrogen stream, the reaction gas (CO2/H2/Ar=30
/60/10, Ar is an internal standard), and the reaction was carried out at a reaction pressure of 30 kg/cm2 and a flow rate of 100 ml/min. The methanol production rate at a reaction temperature of 220°C is 11
90μmol/g. h, selectivity was 82%. As a by-product, CO is 270 μmol/g. h (selectivity 18
%), and a very small amount of methane. Reaction temperature 24
The methanol production rate at 0°C is 1870 μmol/g.
h, selectivity is 73%, CO production rate is 690 μmo
l/g. h, selectivity was 26%. Reaction temperature 260℃
The methanol production rate was 2430 μmol/g. h,
Selectivity is 58%, CO production rate is 1760 μmol
/g. h, selectivity was 41%. The methanol production rate at a reaction temperature of 280°C is 2410 μmol/g. h, the selectivity is 39%, and the CO production rate is 3760 μmol/
g. h, selectivity was 61%.

Example 3 CO2 methanol was added to the reaction tube of a fixed bed pressurized flow reactor.
Copper and zinc oxide (copper loading amount 5 wt%, copper/zinc oxide molar ratio 1:1) are used as a catalyst for conversion to titania (TiO2).
) and a catalyst supporting 2 wt% of magnesium oxide.
g filled. Prior to the reaction, the catalyst was subjected to hydrogen reduction treatment at 350°C for 30 minutes. After cooling in a hydrogen stream, the reaction gas (CO2/H2/Ar=30/60/10, Ar
(internal standard), reaction pressure 30 kg/cm2,
The reaction was carried out at a flow rate of 100 ml/min. Reaction temperature 22
The methanol production rate at 0°C is 1120 μmol/g.
h, selectivity was 83%. As a by-product, CO is 2
30μmol/g. h (selectivity 17%), and a very small amount of methane. The methanol production rate at a reaction temperature of 240°C is 1600 μmol/g. h, the selectivity is 75%, and the CO production rate is 540 μmol/g. h, selectivity was 25%. The methanol production rate at a reaction temperature of 260°C is 2200 μmol/g. h, the selectivity is 60%, and the CO production rate is 1440 μmol/g. h, selection rate 4
It was 0%. The methanol production rate at a reaction temperature of 280°C is 2390 μmol/g. h, the selection rate is 42%,
The CO production rate is 3320 μmol/g. h, selectivity 58
%Met.

Example 4 CO2 methanol was added to the reaction tube of a fixed bed pressurized flow reactor.
Copper and zinc oxide (copper loading amount 5 wt%, copper/zinc oxide molar ratio 1:1) are used as a catalyst for conversion to titania (TiO2).
) and a catalyst supporting 3 wt% of magnesium oxide.
g filled. Prior to the reaction, the catalyst was subjected to hydrogen reduction treatment at 350°C for 30 minutes. After cooling in a hydrogen stream, the reaction gas (CO2/H2/Ar=30/60/10, Ar
(internal standard), reaction pressure 30 kg/cm2,
The reaction was carried out at a flow rate of 100 ml/min. Reaction temperature 22
The methanol production rate at 0°C is 910 μmol/g. h
, the selectivity was 85%. As a by-product, CO is 16
0 μmol/g. h (selectivity 15%), and a very small amount of methane. The methanol production rate at a reaction temperature of 240°C is 1540 μmol/g. h, the selectivity was 77%, and the CO production rate was 460 μmol/g. h, selection rate 2
It was 3%. The methanol production rate at a reaction temperature of 260°C is 2110 μmol/g. h, selectivity is 63%,
The CO production rate is 1240 μmol/g. h, selection rate 37
%Met. The methanol production rate at a reaction temperature of 280°C is 2220 μmol/g. h, selectivity is 45%, C
The O production rate was 2710 μmol/g. h, selection rate 55%
Met.

Example 5 CO2 methanol was added to the reaction tube of a fixed bed pressurized flow reactor.
Copper and zinc oxide (copper supported amount: 5 wt%, copper/zinc oxide molar ratio 1:1) are used as a catalyst for conversion to titania (TiO2).
) and a catalyst supporting 5 wt% of magnesium oxide.
g filled. Prior to the reaction, the catalyst was subjected to hydrogen reduction treatment at 350°C for 30 minutes. After cooling in a hydrogen stream, the reaction gas (CO2/H2/Ar=30/60/10, Ar
(internal standard), reaction pressure 30 kg/cm2,
The reaction was carried out at a flow rate of 100 ml/min. Reaction temperature 22
The methanol production rate at 0°C is 810 μmol/g. h
, the selectivity was 93%. As a by-product, CO is 60
μmol/g. h (selectivity 7%), and a very small amount of methane. The methanol production rate at a reaction temperature of 240°C is 1230 μmol/g. h, the selectivity is 79%,
The CO production rate is 340 μmol/g. h, selection rate 21%
Met. The methanol production rate at a reaction temperature of 260°C was 1710 μmol/g. h, selectivity is 69%, CO
The production rate is 780 μmol/g. h, selectivity was 31%. The methanol production rate at a reaction temperature of 280°C is 21
00 μmol/g. h, the selectivity was 53%, and the CO production rate was 1840 μmol/g. h, selectivity was 47%.

Comparative Example 1 CO2 methanol was added to the reaction tube of a fixed bed pressurized flow reactor.
Copper and zinc oxide (copper loading amount 5 wt%, copper/zinc oxide molar ratio 1:1) are used as a catalyst for conversion to titania (TiO2).
) was charged in an amount of 1 g. Prior to the reaction, the catalyst was subjected to hydrogen reduction treatment at 350°C for 30 minutes. After cooling in a hydrogen stream, the reaction gas (CO2/H2/Ar=3
(0/60/10, Ar is an internal standard), and the reaction was carried out at a reaction pressure of 30 kg/cm2 and a flow rate of 100 ml/min. The methanol production rate at a reaction temperature of 220°C is 1
280μmol/g. h, selectivity was 78%. As a by-product, CO is 360 μmol/g. h(selection rate 2
2%) and a very small amount of methane. Reaction temperature 2
Methanol production rate at 40℃ is 1800 μmol/g
．． h, selectivity is 69%, CO production rate is 820 μm
ol/g. h, selectivity was 31%. Reaction temperature 260
The methanol production rate at ℃ is 2270 μmol/g. h
, the selectivity is 52%, and the CO production rate is 2080 μmo
l/g. h, selectivity was 48%. Reaction temperature 280℃
The methanol production rate was 2250 μmol/g. h,
The selectivity is 35% and the CO production rate is 4215 μmol
/g. h, selectivity was 65%.

The results of Examples 1 to 4 and Comparative Example 1 are summarized in Table 1 below. As is clear from Table 1, as the amount of MgO added increases, the methanol selectivity increases and the CO selectivity decreases. Further, when the amount of MgO added is constant, methanol selectivity decreases and CO selectivity increases as the reaction temperature increases. However, compared to Comparative Example 1 (no MgO added), methanol selectivity is high in all cases and CO selectivity is low.

[0026]

[Table 1]

Claims (2)

[Claims] Claim 1: Titanium dioxide is used as a carrier, and copper,
A catalyst for catalytic hydrogenation characterized by supporting zinc oxide and magnesium oxide. Claim 2: Titanium dioxide is used as a carrier, and copper,
A method for producing methanol by catalytically hydrogenating carbon dioxide with hydrogen gas in the presence of a catalyst supporting zinc oxide and magnesium oxide.