TWI668051B - Nano-nickel catalystand method for hydrogenation of carbon oxides - Google Patents

Abstract

The invention provides a method for hydrogenating a nano nickel catalyst and a carbon oxide. The method of hydrogenating a carbon oxide is to use the nano nickel catalyst as a catalyst for hydrogenating a carbon oxide to a lower hydrocarbon. The nano nickel catalyst comprises a nickel metal body portion and a plurality of microstructures connected to at least one surface of the nickel metal body portion, and the microstructure is pointed and has a length to diameter ratio of 2 Between 5

Description

 Nano nickel catalyst and carbon oxide hydrogenation method  

The present invention relates to a method for hydrogenating nano nickel catalysts and carbon oxides, and more particularly to a method for hydrogenating a nano nickel catalyst having a pointed microstructure and a carbon oxide using the nano nickel catalyst.

As environmental issues are receiving more and more attention, especially the greenhouse effect caused mainly by carbon dioxide, it is particularly necessary to improve. It is also helpful to improve the environmental protection problem by providing a gas that can contain carbon dioxide, such as exhaust gas or flue gas emitted from factories, directly into economically valuable substances.

Traditionally, in order to increase the chance of collision between the catalyst and the reactants, the catalyst particles are miniaturized to increase their surface area, and the micronized catalyst can be applied to some industrial processes (such as catalytic cracking reaction systems in the petroleum industry). However, in general, since the catalyst particles are too small, there is inconvenience in use, and therefore, for industrial processes, they are granulated into larger catalyst particles, and a spherical or cylindrical catalyst is common. There is also a way to fill the catalyst in a circular tube to form a fixed bed reactor, but when the fluid passes, it will cause a considerable pressure drop, especially when the catalyst particles are smaller and the flow rate is increased, this phenomenon is more significant, so Pressurization must be carried out to allow the reaction gas to pass through the catalyst bed, so that industrial fixed bed reactors are not suitable for use in treating large exhaust gases.

Therefore, it is necessary to provide a method and a device for hydrogenating a nano nickel catalyst and a carbon oxide, which can effectively treat carbon dioxide in a gas to solve the problems in the conventional technology.

The main object of the present invention is to provide a nano nickel catalyst having a special microstructure on the surface thereof, which can increase the specific surface area of the catalyst, and maintain a specific distance between the catalyst and the catalyst, when several nano nickel contacts When the media is stacked, the channels for allowing the reactants to flow can be retained between the catalysts, so that the contact area between the reactants and the catalyst can be further increased, and the reaction efficiency and conversion rate can be improved. Furthermore, the nanonickel catalyst of the present invention is particularly advantageous for forming a catalytic bed for the catalytic reaction of gaseous reactants.

Another object of the present invention is to provide a hydrogenation device for carbon oxide, which is filled with a nano nickel catalyst as described above as a catalyst for hydrogenation of carbon oxides, which can convert carbon dioxide or carbon monoxide into methane, Lower hydrocarbons such as ethane or propane, in addition, multiple reactors may be connected in series to increase the conversion of the hydrogenation reaction, or different reaction conditions may be carried out in different reactors to obtain the desired product.

A further object of the present invention is to provide a method for hydrogenating carbon oxides by using a catalyst bed formed by the above-mentioned nano nickel catalyst to carry out hydrogenation of carbon dioxide/carbon monoxide to produce carbon monoxide, methane, ethane, propane, etc. The economical gas, the hydrogenation method of the carbon oxide has the advantages of high conversion rate and high yield, and can also be carried out under normal pressure, and has an advantage in processing carbon dioxide in a large amount.

In order to achieve the above object, an embodiment of the present invention provides a nano nickel catalyst comprising: a nickel metal body portion; and a plurality of microstructures connected to at least one surface of the nickel metal body portion, wherein the The microstructure is pointed and the aspect ratio of the microstructure is between 2 and 5.

In an embodiment of the invention, the microstructure comprises nickel metal.

In an embodiment of the invention, the microstructure is comprised of nickel metal.

In an embodiment of the invention, the nickel metal body portion is spherical.

In an embodiment of the invention, the nickel metal body portion is porous, solid or hollow.

In an embodiment of the invention, the nickel metal body portion has an adsorption pore volume of between 0.0024 and 0.0062 cubic centimeters per gram.

In an embodiment of the invention, the nanonickel catalyst has a specific surface area between 1.5 and 2.0 square meters per gram.

In an embodiment of the invention, the nanonickel catalyst has the ability to reduce carbon dioxide and/or carbon monoxide to lower hydrocarbons.

In an embodiment of the invention, the lower hydrocarbon is selected from the group consisting of methane, ethane, propane, and combinations thereof.

In order to achieve the above object, another embodiment of the present invention provides a carbon oxide hydrogenation apparatus comprising: a first reactor internally filled with a first catalyst bed; and a second reactor, and the first A reactor is connected by a passage, and the second reactor is internally filled with a second catalyst bed; wherein the first catalyst bed and the second catalyst bed both contain a nano nickel catalyst as described above.

In an embodiment of the invention, the first catalyst bed has a minimum value of a first catalyst filling rate of 0.3 gram/ml, and the second catalyst bed has a minimum value of a second catalyst filling rate. It is 0.15 g/ml.

In order to achieve the above object, still another embodiment of the present invention provides a method for hydrogenating a carbon oxide, comprising the steps of: (1) subjecting a carbon oxide and hydrogen to a catalysis of a first catalyst bed; A hydrogenation reaction produces a first mixed gas stream wherein the first catalyst bed comprises a nanonickel catalyst as described above.

In an embodiment of the invention, a first reaction temperature T1 of the first hydrogenation reaction is 180-250 °C.

In an embodiment of the invention, in the step (1), the flow rate of the carbon dioxide is 7.2 ml/min; and the flow rate of the hydrogen gas is 30 ml/min.

In an embodiment of the invention, the method for hydrogenating a carbon oxide further comprises the steps of: (2) subjecting the first mixed gas stream and hydrogen to a second hydrogenation reaction under the catalysis of a second catalyst bed to produce A low carbon hydrocarbon mixed gas stream, wherein the second catalyst bed comprises a nano nickel catalyst as described above.

In an embodiment of the invention, a second reaction temperature T2 of the second hydrogenation reaction is 600-800 °C.

In an embodiment of the invention, in the step (2), the flow rate of the carbon dioxide is 7.2 ml/min; and the flow rate of the hydrogen gas is 30 ml/min.

In an embodiment of the present invention, before the step (1), the method further comprises the step of: heating the first catalyst bed and the second catalyst bed to 250 ° C in hydrogen to make the first catalyst bed A reduction reaction is carried out with the second catalyst bed.

In an embodiment of the invention, in the step (1), the method further comprises: forming an inert gas and the carbon dioxide together with the hydrogen to form a reaction gas stream.

In an embodiment of the invention, the inert gas is nitrogen or argon.

In an embodiment of the invention, the first mixed gas stream comprises methane and carbon monoxide.

In an embodiment of the invention, the low carbon hydrocarbon mixed gas stream comprises a group selected from the group consisting of methane, ethane, propane, or any combination thereof.

100‧‧‧CO2 hydrogenation unit

10‧‧‧First reactor

11‧‧‧First Catalyst Bed

20‧‧‧Second reactor

21‧‧‧Second Catalyst Bed

30‧‧‧ channel

1A and 1B are photographs of a nano nickel catalyst according to an embodiment of the present invention observed by a scanning electron microscope (SEM).

Fig. 2 is a schematic view showing a carbon dioxide hydrogenation apparatus according to an embodiment of the present invention.

3A to 3B are photographs of the nano nickel catalyst of Experiment 1 of the present invention observed by a scanning electron microscope.

The above and other objects, features and advantages of the present invention will become more <RTIgt; Furthermore, the directional terms mentioned in the present invention, such as upper, lower, top, bottom, front, rear, left, right, inner, outer, side, surrounding, central, horizontal, horizontal, vertical, longitudinal, axial, Radial, uppermost or lowermost, etc., only refer to the direction of the additional schema. In addition, the singular forms "a", "the" The range of values (such as 10% to 11% of A) includes upper and lower limits (ie, 10% ≦A ≦ 11%) unless otherwise specified; if the value range does not define a lower limit (such as less than 0.2% B) , or B) below 0.2%, the lower limit may be 0 (ie 0% ≦ B ≦ 0.2%). The above terms are used to The invention is illustrated and understood, and is not intended to limit the invention.

First, an embodiment of the present invention provides a nano nickel catalyst which can be used to catalyze a hydrogenation reaction of carbon oxides. The structure of the nano nickel catalyst mainly comprises a nickel metal body portion and a plurality of microstructures on at least one surface of the nickel metal body portion. The plurality of microstructures have a pointed shape and may be, for example, a needle shape, a ratchet shape, or a tapered shape, but are not limited thereto. The microstructure has an aspect ratio of between 2 and 5, which may be, for example, 2.5, 3.0 or 4.5, but is not limited thereto. As shown in FIGS. 1A and 1B, the nano nickel catalyst has different sharp microstructures, the nano nickel catalyst of FIG. 1A is formed by magnetic field induction, and the first layer BB is not subjected to magnetic field. Induced formation.

In an embodiment of the invention, the composition of the microstructure mainly comprises nickel metal, that is, the microstructure may be formed at the same time as the nickel metal body portion is formed, but the nickel metal body portion may be formed after the nickel metal body portion is formed. Connected to the surface of the nickel metal body portion. Alternatively, the microstructure may contain other components, such as precious metals, which may be modified as needed to achieve the desired catalytic reaction. The main function of the microstructure is to increase the total surface area of the nano nickel catalyst, and to maintain the distance between the nickel metal body portions when filled in a container, so that the nano nickel catalysts are mutually The formation of a pore or a channel allows the area of the reactant contact with the nano nickel catalyst to increase in the reaction, thereby improving the efficiency of the catalytic reaction. Preferably, the nanonickel catalyst has a packing density of 3.0 to 8.0 g/cm 3 , more preferably 3.33 to 7.59 g/cm 3 .

Furthermore, in an embodiment of the invention, the nickel metal body portion is substantially spherical. Preferably, the nickel metal body portion may be porous, solid or hollow. Preferably, the nickel metal body portion has an adsorption pore volume of between 0.0024 and 0.0062 cubic centimeters per gram, which allows most of the reactants to contact the surface of the nano nickel catalyst instead of entering the nickel metal body. The part is subjected to a catalytic reaction. Preferably, the nano nickel catalyst has a specific surface area between 1.5 and 2.0 square meters per gram. In addition, the nanonickel catalyst has the ability to reduce carbon dioxide to lower hydrocarbons. The lower hydrocarbons are selected from the group consisting of methane, ethane, propane and combinations thereof.

Referring to FIG. 2, another embodiment of the present invention provides a carbon oxide hydrogenation apparatus 100, which mainly includes a first reactor 10 internally filled with a first catalyst bed 11 and a second reactor 20 Connected to the first reactor through a passage 30, the second reactor 20 is internally filled with a second catalyst bed 21; wherein the first catalyst bed 11 and the second catalyst bed 21 both contain the above The nano nickel catalyst is described. In an embodiment of the invention, the first catalyst bed has a minimum value of a first catalyst filling rate of 0.3 gram/ml, and the second catalyst bed has a minimum value of a second catalyst filling rate. It is 0.15 g/ml. Therefore, the first catalyst bed and the second catalyst bed can be reacted with a very small amount of catalyst.

Furthermore, still another embodiment of the present invention provides a method for hydrogenating a carbon oxide, comprising the steps of: (S1) subjecting a carbon oxide and hydrogen to a first hydrogenation reaction under the catalysis of a first catalyst bed, Generating a first mixed gas stream; and (S2) subjecting the first mixed gas stream and hydrogen to a second hydrogenation reaction under the catalysis of a second catalyst bed to produce a low carbon hydrocarbon mixed gas stream; wherein the first contact Both the media bed and the second catalyst bed comprise a nano nickel catalyst as described above.

Referring to FIG. 2, the hydrogenation method of the carbon oxide according to an embodiment of the present invention firstly: (S1) subjecting a carbon oxide and hydrogen to a first hydrogenation reaction under the catalysis of the first catalyst bed 11, A first mixed gas stream is produced. In this step, the carbon oxide may be, for example, carbon dioxide, carbon monoxide, or a mixture of the two. The first hydrogenation reaction can be carried out, for example, in the first reactor 10, and a first reaction temperature T1 of the first hydrogenation reaction is 180-250 ° C, which can be, for example, 180, 200, 210, 220, 230, 240 or 250 ° C, but not limited to this. The carbon oxide has a flow rate of 2 to 7.2 ml/min; and the flow rate of the hydrogen gas is 30 to 33 ml/min. Preferably, in this step, an inert gas and the carbon oxide are combined with the hydrogen to form a reaction gas stream. The inert gas can be, for example, nitrogen or argon. The first mixed gas stream may comprise methane, or may additionally comprise water vapor or unreacted hydrogen and carbon dioxide or carbon monoxide.

The method for hydrogenating a carbon oxide according to an embodiment of the present invention is followed by: (S2) subjecting the first mixed gas stream and hydrogen to a second hydrogenation reaction under the catalysis of a second catalyst bed to produce a low-carbon hydrocarbon mixture. airflow. In this step, a second reaction temperature T2 of the second hydrogenation reaction is 600-800 °C. The carbon oxide has a flow rate of 2 to 7.2 ml/min; and the flow rate of the hydrogen gas is 30 to 33 ml/min. Preferably, since the first reactor 10 and the second reactor 20 can be directly communicated by the passage 30, the gas flow rate in the first reactor 10 and the second reactor 20 is substantially the same. However, the hydrogenation apparatus and method of the carbon oxide of the present invention are not limited to the foregoing, and other means such as a condenser tube, a flow valve or other means for facilitating monitoring and controlling the reaction may be additionally used between the two reactors. Therefore, the first reactor 10 and the hydrogen in the second reactor 20 and the carbon oxide may have different flow rates. In an embodiment of the invention, the low carbon hydrocarbon mixed gas stream may comprise a mixed gas of methane, ethane, propane or any combination thereof.

Further, although the method of hydrogenating a carbon oxide of the present invention may not require additionally providing a new hydrogen stream in the step (S2), the present invention does not limit the supply of an additional hydrogen stream, depending on the reaction.

Preferably, in an embodiment of the present invention, before the step (S1), the method further comprises the step of: heating the first catalyst bed 11 and the second catalyst bed 12 to 250 ° C, The first catalyst bed 11 and the nano nickel catalyst of the second catalyst bed 12 undergo a reduction reaction. After the reduction reaction, the nano nickel catalyst can have better catalytic activity.

In order to verify the reaction efficiency of the nanonickel catalyst of the present invention, an experiment was conducted as follows.

Experiment 1: Preparation of nano nickel catalyst

(1) preparing a nickel ion aqueous solution; (2) adding a reducing agent to the nickel ion aqueous solution to form a reaction solution, the reducing agent may be hydrazine; (3) applying a magnetic field to the reaction solution, performing a The reaction of the first preset time obtains a nano nickel catalyst. In this step (1), the aqueous nickel ion solution is prepared by using nickel chloride and deionized water. The aqueous nickel ion solution may further comprise an adjuvant selected from the group consisting of acid methyl cellulose, sodium citrate, sodium hydroxide or a mixture thereof. The weight percentage of the methyl cellulose to the aqueous nickel ion solution is preferably from 0.1 to 1%. In the step (1), a further step (1a) may be further included: heating and stirring until the auxiliary agent is completely dissolved in the aqueous nickel ion solution. The various components and reaction conditions used are shown in Table 1 below.

Then, under the action of the applied magnetic field, the position of the magnet is changed, that is, the arrangement of the magnetic lines is changed, the nickel chloride is used as the precursor and the nucleating agent is introduced, and the reducing agent is added for the chemical reduction reaction, and the nickel nanocrystal can be self-assembled into a spherical shape. Structure and form a specific microstructure on the surface of the spherical structure. For example, eight magnets can be placed in a group of four layers, and the upper layer and the lower layer are placed around the reaction container. When the reaction is completed, a microstructure having a microstructure as shown in FIG. 3A-3B can be formed. Nickel catalyst.

Experiment 2: Hydrogenation of carbon dioxide

The nano nickel catalyst obtained in Experiment 1 is filled in the first reactor 10 and the second reactor 20 shown in FIG. 2, and the first hydrogenation reaction and the second hydrogenation reaction are carried out at different temperatures. The experimental conditions are as follows.

Experimental group 2-1:

The main reaction formula of the first hydrogenation reaction is as follows: CO ₂ +4H ₂ → CH ₄ +2H ₂ O

The reaction conditions for carrying out the first hydrogenation reaction are: H ₂ = 30 cc / min; CO ₂ = 7.2 cc / min; N ₂ = 5 cc / min; H ₂ / CO ₂ = 4.2; first catalyst bed volume = 50 ml; 35g nano nickel catalyst. The results of the conversion of the first hydrogenation reaction are shown in Table 2.

As can be seen from Table 2, the higher the reaction temperature for the first hydrogenation reaction, the higher the conversion of carbon dioxide and hydrogen, which means that the first hydrogenation reaction proceeds very completely.

Experimental group 2-2: Preparation of methane

The reaction conditions of the first hydrogenation reaction were changed: H ₂ = 32 cc / min; CO ₂ = 5 cc / min; H ₂ / CO ₂ = 6.4; first catalyst bed volume = 75 ml; 90 g of nano nickel catalyst. The conversion rate of this first hydrogenation reaction is shown in Table 3.

It can be seen from Table 3 that the higher the reaction temperature, the higher the conversion rate of carbon dioxide and hydrogen, and the lower the proportion of hydrogen consumed, which can reduce the cost and increase the reaction efficiency, and at the same time produce a large amount of methane and a small amount of ethane. From the results of Tables 2 and 3, it is understood that the temperature at which carbon dioxide is hydrogenated to form methane or propane is preferably 180 ° C or higher.

Experimental group 2-3: Preparation of carbon monoxide

CH ₄ +H ₂ O → CO+3H ₂

In order to test the effect of continuously performing the first hydrogenation reaction and the second hydrogenation reaction, in the first reactor 10 having a diameter of 1 cm and a height of 100 cm, 45 g of the nano nickel catalyst obtained in Experiment 1 was filled; at a diameter of 2.54 cm, In the second reactor having a height of 120 cm, 180 g of the nano nickel catalyst obtained in Experiment 1 was filled. Hydrogen was first introduced, and both reactors were heated to 250 degrees for catalyst reduction and held for 1 hour. Next, hydrogen, carbon dioxide, and nitrogen were introduced for 2 hours to make the gas atmosphere in the reactor and the piping uniform. Next, the first reactor 10 is heated to 225 ° C and a continuous gas chromatograph (GC) at the outlet end of the second reactor 20 is continuously sampled to ensure complete conversion of carbon dioxide. Then, the second reactor 20 was heated to 600-800 ° C while observing the reaction. The results are shown in Table 4.

It can be seen from Table 4 that as the reaction temperature in the second reactor rises, the smaller the residual ratio of carbon dioxide, the lower the proportion of methane produced, but the carbon monoxide yield increases. It can be seen that the methane produced by the first reactor has been consumed and a large amount of carbon monoxide is produced. In addition, although the lower temperature reaction of the first reactor (225 ° C) and the higher temperature reaction of the second reactor (600-800 ° C) use the same nano nickel catalyst, the temperature can be obtained by adjusting the appropriate temperature. The required carbon monoxide or methane content.

Experimental group 2-4: Preparation of low carbon hydrocarbon ethane, propane

In order to demonstrate that the nano nickel catalyst of the present invention has the ability to convert carbon monoxide to methane, ethane or propane, the nano nickel catalyst obtained in Experiment 1 is filled in a reactor (for example, FIG. 2 The first reactor 10 or the second reactor 20) is shown, and the reaction gases H ₂ , CO and N ₂ are directly introduced, and the product mixed gas is collected at the outlet of the reactor for analysis. The experimental conditions and results are shown in Table 5 below. Shown.

As can be understood from Table 5, the nanonickel catalyst of the present invention, as a catalyst for hydrogenation of carbon dioxide or carbon monoxide, can effectively hydrogenate carbon oxides such as carbon dioxide or carbon monoxide directly into methane, ethane or propane. Depending on the purpose, different reaction conditions may be selected for adjustment, such as flow rate, temperature, ratio between reactant gases, or multiple reactors may be used in series to carry out a continuous hydrogenation reaction to obtain the desired product. In addition, the nanocatalyst of the present invention can achieve a relatively good methane conversion rate under normal pressure, and does not need to carry out the reaction under a high temperature environment, thereby not only saving energy but also reducing the requirements on the reaction environment. It is also safer to process in large quantities and improve its feasibility.

While the present invention has been disclosed in its preferred embodiments, the present invention is not intended to be limited thereto, and the present invention may be modified and modified without departing from the spirit and scope of the invention. The scope of protection is subject to the definition of the scope of the patent application.

Claims (17)

A nano nickel catalyst comprising: a nickel metal body portion, the nickel metal body portion is spherical; and a plurality of microstructures integrally formed on at least one surface of the nickel metal body portion, and the microstructure is made of nickel The metal is constructed in which the microstructure is pointed and the aspect ratio of the microstructure is between 2 and 5. The nano nickel catalyst according to claim 1, wherein the nickel metal body portion is porous, solid or hollow. The nano nickel catalyst according to claim 2, wherein the nickel metal body portion has an adsorption pore volume of between 0.0024 and 0.0062 cubic centimeters per gram. The nano nickel catalyst according to claim 1, wherein the nano nickel catalyst has a specific surface area of between 1.5 and 2.0 square meters per gram. The nano nickel catalyst according to claim 1, wherein the nano nickel catalyst has the ability to reduce carbon dioxide to lower hydrocarbons. The nano nickel catalyst according to claim 5, wherein the low carbon hydrocarbon is selected from the group consisting of methane, ethane, propane and combinations thereof. A method for hydrogenating a carbon oxide, comprising the steps of: (1) subjecting carbon dioxide and hydrogen to a first hydrogenation reaction under the catalysis of a first catalyst bed to produce a first mixed gas stream, wherein the first catalyst The bed contains a nano nickel catalyst as described in claim 1 of the patent application. a method for hydrogenating a carbon oxide according to claim 7 of the patent application, wherein A first reaction temperature T1 of the first hydrogenation reaction is from 180 to 250 °C. The method for hydrogenating a carbon oxide according to claim 7, wherein in the step (1), the flow rate of the carbon dioxide is 2 to 7.2 ml/min; and the flow rate of the hydrogen is 30 to 33 ml/min. The method for hydrogenating a carbon oxide according to claim 7, wherein the hydrogenation method further comprises a step of: (2) subjecting the first mixed gas stream to a second hydrogenation under the catalysis of a second catalyst bed; The reaction produces a low carbon hydrocarbon mixed gas stream, wherein the second catalyst bed comprises a nano nickel catalyst as described in claim 1 of the patent application. The method for hydrogenating a carbon oxide according to claim 10, wherein in the step (2), the flow rate of the carbon dioxide is 2 to 7.2 ml/min; and the flow rate of the hydrogen is 30 to 33 ml/min. The method for hydrogenating a carbon oxide according to claim 10, wherein in the step (2), a second reaction temperature T2 of the second hydrogenation reaction is 600-800 °C. The method for hydrogenating a carbon oxide according to claim 7, wherein before the step (1), the method further comprises the step of heating the first catalyst bed and the second catalyst bed to 250 in hydrogen gas. °C, the first catalyst bed and the second catalyst bed are subjected to a reduction reaction. The method for hydrogenating a carbon oxide according to claim 7, wherein the step (1) further comprises: forming an inert gas and the carbon dioxide together with the hydrogen to form a reaction gas stream. The method of hydrogenating a carbon oxide according to claim 14, wherein the inert gas is nitrogen. The method of hydrogenating a carbon oxide according to claim 7, wherein the first mixed gas stream comprises methane and carbon monoxide. The method of hydrogenating a carbon oxide according to claim 10, wherein the low carbon hydrocarbon mixed gas stream comprises methane, ethane, propane or any combination thereof.