CN111790391A - Synthesis of a Ni/Zn Double Metal Oxide Catalyst and Its Application in the Oxidative Dehydrogenation of n-Butane - Google Patents

Abstract

The invention discloses the synthesis of a Ni/Zn double metal oxide catalyst and its application in n-butane oxidative dehydrogenation reaction, belonging to the technical field of n-butane oxidative dehydrogenation reaction catalyst. The Ni/Zn double metal oxide material is prepared by a sol-gel method. The catalyst catalyzes the oxidative dehydrogenation of n-butane under the conditions of no water vapor protection and low oxygen alkane feed ratio to generate dehydrogenation products such as butene butadiene. More specifically, nickel salt, zinc salt and deionized water are used to configure according to a certain molar ratio, citric acid is used as a complexing agent, and spongy green powder is obtained after thorough stirring, solvent evaporation, ageing and drying, and then roasting to obtain the green powder. Ni/Zn bimetallic oxide catalyst. Different from the single-composition NiO catalyst, the Ni/Zn double metal oxide catalyst of the present invention can effectively catalyze the conversion of butane into olefins. Moreover, the catalyst has good stability, is not easy to burn and deactivate during the reaction process, and is not easy to deposit carbon at the same time.

Description

Synthesis of a Ni/Zn bimetallic oxide catalyst and its application in the oxidative dehydration of n-butane Application of hydrogen reaction

technical field

The invention belongs to the field of catalysts, in particular to the synthesis of a Ni/Zn double metal oxide catalyst and its application in the oxidative dehydrogenation reaction of n-butane.

Background technique

The components of _C4 hydrocarbons have attracted widespread attention due to their applications in both fuel and chemical industries. Butane is widely present in the by-products of petrochemical and coal chemical industries, and it is no longer suitable as a fuel. The corresponding dehydroolefins Products such as butene and butadiene are chemical intermediates in great demand. The development and utilization of n-butane dehydrogenation technology to produce butadiene is of great significance to the efficient utilization of carbon tetraalkane resources. Compared with the butane catalytic dehydrogenation process, the n-butane oxidative dehydrogenation reaction has significant advantages: no thermodynamic limitations; relatively low temperature; the presence of oxygen in the reaction medium, and less coke deposition. Therefore, the development of n-butane oxidative dehydrogenation to produce butadiene technology can not only effectively adjust the supply and demand balance of butadiene, alleviate the shortage of olefin resources on the market, but also realize the high value-added utilization of n-butane.

The catalysts used in the oxidative dehydrogenation of n-butane were mostly concentrated on supported catalysts such as V-MgO, Ni-Bi, Mo, etc., which showed high olefin selectivity for the oxidative dehydrogenation of butane, but due to the difficulty in mobilizing The reactive oxygen species in the bulk phase have insufficient reactivity and require harsh reaction conditions. In recent years, Ni-based catalysts have been widely used in the oxidative dehydrogenation of low-carbon hydrocarbons (C ₂ , C ₃ ), especially by modifying Ni with other elements to form composite metal oxides, such as Ni-Zr-O, Ni-Ce -O etc. It is of great significance to develop Ni/Zn bimetallic oxide catalysts with excellent activity.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a kind of synthesis of Ni/Zn double metal oxide catalyst and its application in n-butane oxidative dehydrogenation reaction. Catalytic oxidative dehydrogenation of n-butane under protected conditions to generate C ₄ olefins.

The purpose of this invention is to realize through the following technical solutions:

The prepared bimetallic oxide catalyst is placed in the reactor, and the mixed gas is introduced into the reactor to maintain a certain space velocity and the temperature of the catalyst bed for the reaction to obtain dehydrogenation products such as butene butadiene.

The mixed gas includes n-butane, air and nitrogen, and the mixed volume ratio is 1:(5-10):(1-6). The preferred ratio of mixing volumes is 1:5:6.

The certain space velocity is 14400-16200 mL/(g·h), and the temperature of the catalyst bed is set at 400-500°C.

The two-component oxide catalyst component includes Ni and Zn, wherein the molar ratio of nickel to zinc is 1:0.01-5.

In the catalyst, the molar ratio of nickel to zinc is preferably 1:0.1-0.5:.

In the catalyst, zinc is derived from a zinc salt, which is zinc nitrate; nickel is derived from a nickel salt, and the nickel salt is nickel nitrate.

The preparation process of the double metal oxide catalyst comprises the following steps:

Step (1), a certain quality of nickel salt, zinc salt and deionized water are configured in a container, citric acid monohydrate and deionized water are configured in another container, and the citric acid solution is slowly added dropwise to the nickel-containing zinc salt. in the mixed solution, and fully stirred, so that the molar ratio of nickel and zinc is 1:0.01～5, and the molar ratio of citric acid monohydrate and metal ions in the solution is 1.5:1;

The molar ratio of the zinc salt and deionized water is 0.01-5:1000;

The mol ratio of described nickel salt and deionized water is 1:1000;

The mass fraction of the monohydrate citric acid solution is 3.0% to 16.0%.

Step (2), the above solution is placed in a water bath at 70°C;

In step (3), the solution in step (2) is stirred until it is viscous, and then transferred to an oven for drying;

The drying oven temperature was 120°C.

In step (4), the obtained spongy green powder is calcined and cooled, then ground and sieved to obtain a two-component catalyst of 40-60 meshes.

The roasting temperature is 550-900 DEG C, and the roasting time is 2-5h.

Beneficial effects of the present invention:

The present invention adopts a sol-gel method, and the catalyst is prepared by using (Ni(NO ₃ ) ₂ ·6H ₂ O) and (Zn(NO ₃ ) ₂ ·6H ₂ O) as precursors, and citric acid as complexing agent. The introduction of Zn element helps the catalyst to form a crystalline Ni-Zn-O solid solution that is favorable for alkane activation, thereby having a greater impact on the oxygen mobility and oxygen capacity of the catalyst (the amount of oxygen in the catalyst participating in the reaction), The catalyst has good activity and stability, and can catalyze the oxidative dehydrogenation of n-butane to generate C ₄ olefins under the conditions of below 500° C. and low oxygen alkane feed ratio.

Description of drawings

FIG. 1 is the XRD patterns of the catalysts of Examples 3-6 and the NiO catalyst without Zn addition.

FIG. 2 is a temperature-programmed reduction oxidation (TPRO) diagram of the catalyst of Example 3 and the NiO catalyst without Zn addition according to the present invention.

Detailed ways

The present invention will be further described below in conjunction with the embodiments, but the present invention is not limited to these specific embodiments.

Example 1

Process for preparing catalyst

Dissolve 1.4540g Ni(NO ₃ ) ₂ ·6H ₂ O and 0.0149g Zn(NO ₃ ) ₂ ·6H ₂ O in 90 mL of distilled water, this solution is denoted as solution A, and then transfer solution A to a water bath at 70°C, 1.5917 g of citric acid monohydrate (C ₆ H ₈ O ₇ ·H ₂ O) was dissolved in 50 mL of distilled water, and this solution was designated as solution B. Slowly add solution B to solution A, continue to stir the mixed solution in a 70°C water bath until it becomes viscous, and transfer the viscous material to a 120°C oven for overnight drying. A spongy green powder was obtained. The dried samples were calcined at 800°C for 3 hours in a tube furnace with an oxygen atmosphere, cooled, ground, and _sieved to obtain a 40-60 mesh nickel oxide catalyst.

Oxidative Dehydrogenation Process

0.2 g of the above catalyst was filled into a stainless steel reactor with an inner diameter of 8 mm, and n-butane was used as the raw material gas, and its percentage content was 99.9%. Feed air and nitrogen simultaneously, the composition is set to n-butane: air: nitrogen molar ratio of 1:10:1, the mixed gas is introduced into the reactor, the space velocity is 14400mL/(g h), the catalyst The bed temperature was 400°C to carry out the reaction, and the reaction results of the products after 1h and 4h were analyzed by gas chromatography as follows:

Example 2

Process for preparing catalyst

Dissolve 1.4540g Ni(NO ₃ ) ₂ ·6H ₂ O and 0.1487g Zn(NO ₃ ) ₂ ·6H ₂ O in 90 mL of distilled water, this solution is denoted as A solution, and then transfer A solution to a 70 ℃ water bath, 1.7336 g of citric acid monohydrate (C ₆ H ₈ O ₇ ·H ₂ O) was dissolved in 50 mL of distilled water, and the solution was designated as B solution. Slowly add solution B to solution A, continue to stir the mixed solution in a 70°C water bath until it becomes viscous, and transfer the viscous material to a 120°C oven for overnight drying. A spongy green powder was obtained. The dried sample was calcined at 550° C. for 5 hours in a tube furnace with an oxygen atmosphere, cooled, ground, and sieved to obtain a 40-60 mesh nickel-zinc composite oxide catalyst, which was denoted as NiZn _0.1 , and sealed for preservation.

Oxidative Dehydrogenation Process

0.2 g of the above catalyst was filled into a stainless steel reactor with an inner diameter of 8 mm, and n-butane was used as the raw material gas, and its percentage content was 99.9%. Simultaneously feed air and nitrogen, and its composition is set to n-butane: the molar ratio of air: nitrogen is 1:5:6, the mixed gas is introduced into the reactor, the space velocity is 16200mL/(g h), the catalyst The bed temperature was 500 °C to carry out the reaction, and the reaction results of the products after 1 h and 4 h were analyzed by gas chromatography as follows:

Example 3

Process for preparing catalyst

Dissolve 1.4540g Ni(NO ₃ ) ₂ ·6H ₂ O and 0.7437g Zn(NO ₃ ) ₂ ·6H ₂ O in 90 mL of distilled water, this solution is denoted as A solution, and then transfer A solution to a 70°C water bath, 2.3640 g of citric acid monohydrate (C ₆ H ₈ O ₇ ·H ₂ O) was dissolved in 50 mL of distilled water, and the solution was designated as solution B. Slowly add solution B to solution A, continue to stir the mixed solution in a 70°C water bath until it becomes viscous, and transfer the viscous material to a 120°C oven for overnight drying. A spongy green powder was obtained. The dried sample was calcined at 800° C. for 3 hours in a tube furnace with an oxygen atmosphere, cooled, ground, and _sieved to obtain a 40-60 mesh nickel-zinc composite oxide catalyst.

Oxidative Dehydrogenation Process

0.2 g of the above catalyst was filled into a stainless steel reactor with an inner diameter of 8 mm, and n-butane was used as the raw material gas, and its percentage content was 99.9%. Feed air and nitrogen simultaneously, the composition is set to n-butane: air: nitrogen molar ratio of 1:5:6, the mixed gas is introduced into the reactor, the space velocity is 14400mL/(g h), the catalyst The bed temperature was 440°C to carry out the reaction, and the reaction results of the products after 1h and 4h were analyzed by gas chromatography as follows:

Example 4

Process for preparing catalyst

Dissolve 1.4540g Ni(NO ₃ ) ₂ ·6H ₂ O and 1.4874g Zn(NO ₃ ) ₂ ·6H ₂ O in 90 mL of distilled water, this solution is denoted as solution A, and then transfer solution A to a water bath at 70°C, 3.1520 g of citric acid monohydrate (C ₆ H ₈ O ₇ ·H ₂ O) was dissolved in 50 mL of distilled water, and the solution was designated as solution B. Slowly add solution B to solution A, continue to stir the mixed solution in a 70°C water bath until it becomes viscous, and transfer the viscous material to a 120°C oven for overnight drying. A spongy green powder was obtained. The dried sample was calcined at 900° C. for 2 hours in a tube furnace with oxygen atmosphere, cooled, ground, and sieved to obtain a 40-60 mesh nickel-zinc composite oxide catalyst, which was denoted as NiZn ₁ , and sealed for preservation.

Oxidative Dehydrogenation Process

0.2 g of the above catalyst was filled into a stainless steel reactor with an inner diameter of 8 mm, and n-butane was used as the raw material gas, and its percentage content was 99.9%. Feed air and nitrogen simultaneously, the composition is set to n-butane: air: nitrogen molar ratio of 1:5:6, the mixed gas is introduced into the reactor, the space velocity is 14400mL/(g h), the catalyst The bed temperature was 440°C to carry out the reaction, and the reaction results of the products after 1h and 4h were analyzed by gas chromatography as follows:

Example 5

Process for preparing catalyst

Dissolve 1.4540g Ni(NO ₃ ) ₂ ·6H ₂ O and 4.4622g Zn(NO ₃ ) ₂ ·6H ₂ O in 90 mL of distilled water, this solution is denoted as A solution, and then transfer A solution to a water bath at 70°C, 6.3039 g of citric acid monohydrate (C ₆ H ₈ O ₇ ·H ₂ O) was dissolved in 50 mL of distilled water, and the solution was designated as B solution. Slowly add solution B to solution A, continue to stir the mixed solution in a 70°C water bath until it becomes viscous, and transfer the viscous material to a 120°C oven for overnight drying. A spongy green powder was obtained. The dried samples were calcined at 800° C. for ₃ hours in a tube furnace with an oxygen atmosphere, cooled, ground, and screened to obtain a 40-60 mesh nickel-zinc composite oxide catalyst.

Oxidative Dehydrogenation Process

0.2 g of the above catalyst was filled into a stainless steel reactor with an inner diameter of 8 mm, and n-butane was used as the raw material gas, and its percentage content was 99.9%. Feed air and nitrogen simultaneously, the composition is set to n-butane: air: nitrogen molar ratio of 1:5:6, the mixed gas is introduced into the reactor, the space velocity is 14400mL/(g h), the catalyst The bed temperature was 440°C to carry out the reaction, and the reaction results of the products after 1h and 4h were analyzed by gas chromatography as follows:

Example 6

Process for preparing catalyst

Dissolve 1.4540g Ni(NO ₃ ) ₂ ·6H ₂ O and 7.4370g Zn(NO ₃ ) ₂ ·6H ₂ O in 90 mL of distilled water, this solution is denoted as solution A, and then transfer solution A to a water bath at 70°C, 9.4558 g of citric acid monohydrate (C ₆ H ₈ O ₇ ·H ₂ O) was dissolved in 50 mL of distilled water, and the solution was designated as solution B. Slowly add solution B to solution A, continue to stir the mixed solution in a 70°C water bath until it becomes viscous, and transfer the viscous material to a 120°C oven for overnight drying. A spongy green powder was obtained. The dried samples were calcined at 800°C for 4 hours in a tube furnace with an oxygen atmosphere, cooled, ground, and sieved to obtain a 40-60 mesh nickel-zinc composite oxide catalyst, which was denoted as NiZn ₅ , and sealed for preservation.

Oxidative Dehydrogenation Process

0.2 g of the above catalyst was filled into a stainless steel reactor with an inner diameter of 8 mm, and n-butane was used as the raw material gas, and its percentage content was 99.9%. Feed air and nitrogen simultaneously, the composition is set to n-butane: air: nitrogen molar ratio of 1:5:6, the mixed gas is introduced into the reactor, the space velocity is 14400mL/(g h), the catalyst The bed temperature was 500 °C to carry out the reaction, and the reaction results of the products after 1 h and 4 h were analyzed by gas chromatography as follows:

The XRD characterization shown in Figure 1 shows that the introduction of Zn element forms a Ni _0.9 Zn _0.1 O solid solution, and the NiZn _0.5 catalyst has a larger content of this type of phase. As shown in Figure 2, the temperature-programmed reduction oxidation (TPRO) comparison of NiZn _0.5 catalyst and NiO catalyst without Zn addition shows that the introduction of Zn element affects the oxygen mobility and oxygen capacity of the catalyst (the oxygen in the catalyst participating in the reaction). quantity) have a greater impact. Combining Figures 1 and 2, it can be seen that the introduction of Zn element forms a solid solution that is favorable for the activation of alkanes, which is conducive to promoting the fluidity of oxygen, so that the catalyst has better activity and stability.

The above content is a further detailed description of the present invention in conjunction with the specific preferred embodiments, and it cannot be considered that the specific embodiments of the present invention are limited to this. , some simple deductions and substitutions can also be made, all of which should be regarded as belonging to the protection scope of the invention determined by the submitted claims.

Claims (7)

1. The Ni/Zn bimetallic oxide catalyst is characterized in that the Ni/Zn bimetallic oxide catalyst comprises Ni and Zn, wherein the molar ratio of the nickel to the zinc is 1 (0.01-5).

2. The Ni/Zn bimetallic oxide catalyst of claim 1, wherein the molar ratio of nickel to zinc in the catalyst is 1 (0.1-0.5); and the zinc is derived from zinc salt, and the zinc salt is zinc nitrate; the nickel is derived from a nickel salt, which is nickel nitrate.

3. A method of synthesizing a Ni/Zn bimetallic oxide catalyst as in claim 1 or 2, characterized by comprising the steps of:

the method comprises the following steps of (1) arranging nickel salt, zinc salt and deionized water with certain mass in a container, arranging citric acid monohydrate and deionized water in another container, slowly dropwise adding citric acid monohydrate solution into a mixed solution containing the nickel salt and the zinc salt, and fully stirring to ensure that the molar ratio of nickel to zinc is 1 (0.01-5); the molar ratio of citric acid monohydrate to metal ions in the solution is 1.5: 1;

step (2), placing the solution in a water bath at 70 ℃;

step (3) stirring the solution obtained in the step (2) to be viscous, and transferring the solution to an oven for drying;

roasting and cooling the spongy green powder obtained in the step (4), and grinding and screening to obtain the 40-60-mesh two-component catalyst.

4. The method for synthesizing Ni/Zn bimetal oxide catalyst as claimed in claim 3, wherein the molar ratio of the zinc salt, the nickel salt and the deionized water is (0.01-5) 1: 1000; the mass fraction of the citric acid monohydrate solution is 3.0-16.0%.

5. The method for synthesizing a Ni/Zn bimetallic oxide catalyst as in claim 3 or 4, characterized in that the oven temperature for drying in step (3) is 120 ℃.

6. The synthesis of Ni/Zn bimetal oxide catalyst and the application thereof in the oxidative dehydrogenation of n-butane as claimed in claim 5, wherein the calcination temperature in the step (4) is 550-900 ℃ and the calcination time is 2-5 h.

7. Use of a Ni/Zn bimetallic oxide catalyst in an n-butane oxidative dehydrogenation reaction according to claim 1 or 6, characterized in that:

placing the prepared Ni/Zn bimetallic oxide catalyst in a reactor, introducing mixed gas into the reactor, and keeping a certain airspeed and the temperature of a catalyst bed layer for reaction to obtain a dehydrogenation product of butylene butadiene;

the mixed gas comprises n-butane, air and nitrogen, and the mixing volume ratio is 1 (5-10) to 1-6;

the certain airspeed is 14400-16200 mL/(g.h), and the temperature of the catalyst bed is set to be 400-500 ℃.

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