CN113368857B - Preparation method of bulk phase intermetallic compound supported catalyst - Google Patents

Abstract

The invention discloses a preparation method of a bulk phase intermetallic compound supported catalyst, which is characterized in that a cobalt compound is added into a nutrient solution for culturing scindapsus aureus, the scindapsus aureus absorbs cobalt elements, and then the scindapsus aureus is sintered to prepare porous biochar, copper ions in soluble copper chloride and nickel ions in nickel nitrate are adsorbed in pore channels of the biochar in a dipping mode and are pyrolyzed to form a copper-nickel intermetallic compound, and part of metal copper and metal cobalt loaded in the biochar form a cobalt-copper intermetallic compound to prepare the catalyst. The interaction between the two intermetallic compounds in the catalyst prepared by the method increases the migration capability of electrons, so that the prepared catalyst has high-efficiency catalytic performance, the two intermetallic compounds are coated or loaded in the biochar, the durability of the catalyst is improved, the removal rate of organic pollutants in water is improved, and a new thought is provided for the high-efficiency, stable and multifunctional intermetallic compound catalyst applied to the fields of environmental pollution control and energy conversion.

Description

Preparation method of bulk phase intermetallic compound supported catalyst

Technical Field

The invention belongs to the technical field of environmental preparation, and particularly relates to a preparation method of a bulk phase intermetallic compound supported catalyst.

Background

The rapid development of modern industry and agriculture causes a large amount of organic pollutants to remain in the environment, and related research reports show that the types of the organic pollutants found in the tap water bodies at the abroad are nearly 2000, and more than 200 organic pollutants are detected in most rivers at home. Therefore, the research on how to remove the organic pollutant pollution in the environment has important significance. The organic pollutants in the environment mainly include: halogenated hydrocarbon, polychlorinated biphenyl, polycyclic aromatic hydrocarbon, azo dye, pesticide, etc. Where persistent organic pollutants have a higher toxicity and are more environmentally hazardous because they can be present in the environment for extended periods of time and are difficult to degrade.

The catalytic technology as an effective method for treating the water pollution problem comprises photocatalysis, electrocatalysis and the like, has important application prospects in the fields of energy and environment, and is valued by numerous researchers in the world. Particularly, the discovery of the intermetallic compound is that the intermetallic compound has a crystal structure and electronic properties different from those of the original metal, and consists of two or more metal elements, and the particularity of the structure and the composition enables the intermetallic compound to have very good catalytic performance in the fields of catalyzing selective hydrogenation of alkyne, alkane dehydrogenation, electrocatalysis, photocatalysis and the like, and the discovery has attracted extensive attention of researchers.

However, since some of the components constituting the intermetallic compound (e.g., gallium) are relatively difficult to reduce, it is difficult to prepare a small-particle-size, highly dispersed intermetallic compound catalyst. This severely limits the effectiveness of the intermetallic compound catalyst.

In view of the above, there is a need to develop a catalyst having high loading, high dispersion and stable performance based on the bulk intermetallic compound.

Disclosure of Invention

In order to overcome the problems, the inventor of the invention makes a keen study on an intermetallic compound and a catalyst, and researches a preparation method of a bulk phase intermetallic compound supported catalyst, specifically, a cobalt compound is added into a nutrient solution for culturing scindapsus aureus, the scindapsus aureus absorbs cobalt elements, and then the scindapsus aureus is sintered to prepare porous biochar, copper ions in soluble copper chloride and nickel ions in nickel nitrate are adsorbed in pore channels of the biochar in an impregnation mode and are pyrolyzed to form a copper-nickel intermetallic compound, and partial metal copper and metal cobalt supported in the biochar form a cobalt-copper intermetallic compound to prepare the catalyst. The interaction between the two intermetallic compounds in the catalyst prepared by the method of the invention increases the migration capability of electrons, so that the prepared catalyst has high-efficiency catalytic performance, wherein the two intermetallic compounds are coated or loaded in the biochar, thereby improving the durability of the catalyst, improving the removal rate of organic pollutants in water, and providing a new thought for the high-efficiency, stable and multifunctional intermetallic compound catalyst applied to the fields of environmental pollution control and energy conversion, thereby completing the invention.

In particular, it is an object of the present invention to provide a process for the preparation of a bulk intermetallic compound supported catalyst, the process comprising: the soluble metal salt is soaked in the pore canal of the porous biochar and is prepared by pyrolysis.

The invention has the advantages that:

(1) according to the preparation method of the bulk phase intermetallic compound supported catalyst, the copper-nickel intermetallic compound and the cobalt-copper intermetallic compound are coated or supported in the charcoal, so that the catalytic performance and the thermal stability of the catalyst are effectively improved.

(2) According to the preparation method of the bulk phase intermetallic compound supported catalyst provided by the invention, the copper-nickel intermetallic compound and the cobalt-copper intermetallic compound in the prepared catalyst interact with each other, so that the migration capacity of electrons is increased, and the removal rate of organic pollutants in water is improved.

(3) According to the preparation method of the bulk phase intermetallic compound supported catalyst, the biochar loaded with metal ions is pyrolyzed in stages, and the prepared catalyst is large in pore size and good in durability.

(4) The preparation method of the bulk phase intermetallic compound supported catalyst provided by the invention realizes the preparation of the intermetallic compound catalyst with small particle size and high dispersion, and provides a new thought for the high-efficiency, stable and multifunctional carbon-based catalyst applied to the fields of environmental pollution control and energy conversion.

Drawings

FIG. 1 shows TEM characterization pictures of catalysts prepared in example 1 of the present invention;

FIG. 2 shows SEM-Mapping characterization photographs of different elements contained in the catalyst prepared in example 1 of the present invention;

figure 3 shows XRD characterization pictures of the catalyst prepared in example 1 of the present invention.

Detailed Description

The invention is explained in more detail below with reference to the figures and examples. The features and advantages of the present invention will become more apparent from the description.

The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. While the various aspects of the embodiments are presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

According to the preparation method of the bulk phase intermetallic compound supported catalyst provided by the invention, the soluble metal salt is impregnated in the pore canal of the porous biochar and is prepared by pyrolysis.

According to the invention, the porous biochar is enriched with cobalt, and is prepared by adding a cobalt compound in the plant growth process, absorbing cobalt elements by the roots of plants, transmitting the cobalt elements to tissues such as stems, leaves and the like, collecting the plants and sintering the plants.

In the present invention, the plant is a vine plant having a good effect of absorbing cobalt element, such as iris, parthenocissus tricuspidata, trumpet creeper, and scindapsus aureus, and preferably scindapsus aureus.

According to the invention, the vine plant has strong stress resistance and simple and convenient management, wherein the representative scindapsus aureus has developed root system and persistent vitality, can survive in the presence of water, and has excellent enrichment effect on cobalt most importantly.

According to the invention, the cobalt compound comprises ionic cobalt and/or cobalt in complex form, preferably ionic cobalt, such as cobalt chloride, cobalt sulphate, cobalt carbonate, etc., more preferably cobalt chloride.

According to the invention, the plant cultivation method is preferably to cultivate the plant in a nutrient solution, wherein the nutrient solution is a nutrient solution which can meet the normal growth of the plant, such as a morade nutrient solution.

In the invention, the cobalt ions are transported in the plant body more rapidly, can be combined with organic acid in the nutrient solution to exist in a complex state to form a stable chelate, solve the problems of precipitation or oxidation, low absorption efficiency and the like caused by the combination of trace elements in the nutrient solution and other ions such as sulfate radicals, and are beneficial to promoting the absorption, transportation and transfer of cobalt.

Furthermore, the concentration of the cobalt element in the cobalt compound in the nutrient solution is 100-300 mg/L, preferably 150-230 mg/L, and more preferably 180-200 mg/L.

According to the invention, the absorption of cobalt element by plants is limited, the cobalt with low concentration can promote the growth of plants, the concentration is too high, the plants can be poisoned to cause the death of the plants, and in order to ensure the normal growth of the plants and enrich more cobalt element in the plants, the concentration of the cobalt element in the nutrient solution is 100-300 mg/L.

According to the invention, plants grow in the nutrient solution, cobalt is adsorbed to tissues such as roots, stems and leaves, and in order to meet the growth requirements of the plants and the cobalt enrichment effect, the nutrient solution of the plants is preferably replaced according to a certain period, wherein the replacement period is 5-12 days/time, preferably 8-12 days/time, and more preferably 10 days/time.

In the invention, the enrichment amount of cobalt by plants is gradually increased along with the extension of the growth cycle of the plants, but the excessive cobalt element enriched in the plant body can cause the toxic phenomenon of the plants, so the too long growth cycle is unfavorable for the growth of the plants, and the planting cycle of the plants is 60-150 days, preferably 90-120 days, and more preferably 100 days.

According to the invention, because the cobalt element is distributed in each tissue of the root, the stem and the leaf of the plant, after the plant growth is finished, the whole plant is used as the biomass to carry out sintering reaction to prepare the porous biochar.

Further, the biomass needs to be dried and pulverized before sintering, so as to change or destroy the lignocellulose structure in the biomass, and improve the sintering efficiency.

Wherein the crushed particle size is less than 30mm, preferably 10-20 mm, and more preferably 15-16 mm.

In the invention, with the rise of sintering temperature, the specific surface area and the total pore volume of the biochar are increased, the micropore volume is also increased, and the cracking of the branched carbon atom structure in the biochar and the collapse of the biochar structure are caused by overhigh sintering temperature; the heating rate and the heat preservation time are important factors influencing the mechanical property and the pore diameter of the biochar, the carbon yield of the biochar is reduced due to the fact that the heating rate is too high or the heat preservation time is too long, the pore diameter is different, the mechanical property is low, and the same phenomenon can be caused due to the fact that the heating rate is too low or the heat preservation time is too short.

In the invention, during sintering, the biomass is carbonized to form the biochar with a porous structure, different morphological compounds of cobalt contained in the biomass such as complex state and ionic state are pyrolyzed into simple substance cobalt or cobalt oxide which is coated or loaded in the biochar, and different valence states of the cobalt element improve the electron transfer capability in the biochar, thereby improving the stability and durability of the biochar.

The biochar is used as a substrate material, not only is used for fixing intermetallic compounds, but also can improve the light absorption rate, the existence of cobalt element increases the specific surface area of the biochar to a certain extent, and the copper-nickel intermetallic compounds and the cobalt-copper intermetallic compounds are fused in the biochar, so that the electron transfer in the biochar is promoted, the effect between the active sites on the surface of the biochar is effectively enhanced, and the catalytic activity is improved.

According to a preferred embodiment, the sintering is carried out in an inert gas, preferably argon, the sintering temperature is 300-600 ℃, the sintering time is 0.5-5 h, and the temperature rise rate is 1-6 ℃/min, so that the porous biochar with good mechanical property, large pore diameter and uniformity can be obtained.

In a further preferred embodiment, the sintering temperature is 400-500 ℃, the sintering time is 1-4 h, and the temperature rise rate is 2-4 ℃/min.

In a further preferred embodiment, the sintering temperature is 450 ℃, the sintering time is 3h, and the heating rate is 3 ℃/min.

Optionally, the crushed biological acid is treated before sintering to improve the surface acidity and increase the pore structure of the biological carbon.

Further, the acid-modified sintered biochar needs to be washed to be neutral, dried and then mixed with soluble metal salt for reaction.

Wherein the acid is a strong acid, such as hydrochloric acid. The hydrochloric acid is more environmentally friendly than other strong acids, and more importantly, the hydrochloric acid can decompose lignocellulose, aliphatic and aromatic compounds in the biochar and hinder shrinkage in a pore-forming process.

According to the invention, the concentration of hydrogen ions in the phosphoric acid is 0.01-1 mol/L, preferably 0.05-0.3 mol/L, and more preferably 0.1 mol/L.

According to the invention, the influence of pH on the biochar is small, hydrochloric acids with different acid strengths can block the shrinkage of the biochar in the pore-forming process, and the high-concentration hydrochloric acid can shorten the acid modification time.

In the invention, the acid modification time is 5-60 min, preferably 10-30 min, for example 20 min.

According to the invention, the porous biochar internally contains a pore channel structure, soluble metal salt is adsorbed in the pore channel of the biochar in an impregnation mode, the metal salt is thermally decomposed to form copper metal and nickel metal in the pyrolysis process, and copper-nickel intermetallic compound and cobalt-copper intermetallic compound are formed between the metal salt and cobalt metal loaded in the biochar and coated or loaded in the biochar, so that abundant active defects are exposed on the surface of the prepared catalyst, the prepared catalyst has high-efficiency catalytic performance, meanwhile, the two intermetallic compounds increase the electron migration capacity, and the active sites and the stability of the catalyst are improved.

According to the invention, the metal salt comprises copper salt and nickel salt, the copper salt is selected from any one or more of copper nitrate, copper sulfate and copper chloride, and is preferably copper chloride; the nickel salt is selected from any one or more of nickel nitrate, nickel sulfate and nickel chloride, and is preferably nickel nitrate.

In the invention, the dipping time is 5-48 h, preferably 20-36 h, and more preferably 24 h.

According to the invention, along with the extension of the impregnation time, the more sufficient the contact between copper ions in the soluble copper salt and nickel ions in the nickel salt and the biochar is, the more copper ions and nickel ions are loaded on the pore canal or the surface of the biochar, the more copper-nickel intermetallic compounds are finally formed, the stronger the stability and the activeness of the catalyst are, and the overlong impregnation time can not cause the obvious increase of the copper ions and nickel ions loaded on the pore canal or the surface of the biochar.

According to the present invention, the protective atmosphere during pyrolysis is a reducing gas or a mixed gas of an inert gas and a reducing gas, preferably a mixed gas of an inert gas and a reducing gas, such as argon and hydrogen.

The present inventors have found that staged pyrolysis, including:

the first stage is as follows: the pyrolysis temperature is 200-350 ℃, the pyrolysis time is 0.1-2 h, and the heating rate is 0.5-3 ℃/min;

and a second stage: the pyrolysis temperature is 400-600 ℃, the pyrolysis time is 0.5-3 h, and the heating rate is 1-5 ℃/min;

and a third stage: the pyrolysis temperature is 650-900 ℃, the pyrolysis time is 0.1-1 h, and the heating rate is 5-9 ℃/min.

Further, the pyrolyzing comprises:

the first stage is as follows: the pyrolysis temperature is 250-300 ℃, the pyrolysis time is 0.5-1.5 h, and the heating rate is 1-2 ℃/min;

and a second stage: the pyrolysis temperature is 500-550 ℃, the pyrolysis time is 1-2 h, and the heating rate is 2-4 ℃/min;

and a third stage: the pyrolysis temperature is 750-800 ℃, the pyrolysis time is 0.8-1.5 h, and the heating rate is 6-8 ℃/min.

Still further, the pyrolyzing comprises:

the first stage is as follows: the pyrolysis temperature is 280 ℃, the pyrolysis time is 1h, and the heating rate is 1 ℃/min;

and a second stage: the pyrolysis temperature is 520 ℃, the pyrolysis time is 1.5h, and the heating rate is 3 ℃/min;

and a third stage: the pyrolysis temperature is 760 ℃, the pyrolysis time is 1h, and the heating rate is 7 ℃/min.

According to the invention, along with the rise of the pyrolysis temperature, the biochar loaded with the copper element and the nickel element loses a large amount of water, the content of the carbon element is obviously increased, the copper salt and the nickel salt are decomposed into the copper oxide and the nickel oxide at high temperature and are reduced into simple substances under the action of hydrogen, and as the metal copper, the metal nickel and the metal copper have stronger binding force with the metal cobalt loaded in the biochar before pyrolysis under the action of high-temperature reducing gas, the sintering and agglomeration of metal particles can be effectively inhibited, the copper-nickel intermetallic compound and the cobalt-copper intermetallic compound are formed and are coiled in the biochar, and the stability of the catalyst is improved.

The inventors have found that the rate of temperature rise has the greatest effect on the mechanical properties of the catalyst and also has some effect on pore size and porosity. With the acceleration of the heating rate, the spacing between the carbon layers is firstly reduced and then increased, the mechanical strength of the carbon material corresponding to the spacing is firstly increased and then reduced, the proper heating rate can improve the aperture size of the catalyst, decompose and heat and adjust the heating rate in different pyrolysis stages, and the catalyst can be endowed with excellent mechanical performance and larger aperture.

In the present invention, the heat generated during the reaction causes an increase in the porosity of the catalyst as the pyrolysis time is extended, but too long a time causes a collapse phenomenon of the pore diameter that has been formed.

According to the invention, the weight ratio of the soluble copper salt, the nickel salt and the biochar is 1: (1-20): (10 to 100), preferably 1: (3-10): (20-70), more preferably 1: (5-9): (20-40).

According to the invention, the biochar containing metal cobalt is used as an alkaline carrier, an electronic effect beneficial to improving selectivity can be generated, carbon deposition is reduced, a copper-nickel intermetallic compound and a cobalt-copper intermetallic compound are used as active components, the electron migration capacity is enhanced, the prepared catalyst has a large specific surface area within the dosage range, and the loading amount of the copper-nickel intermetallic compound and the cobalt-copper intermetallic compound is high.

Examples

The present invention is further described below by way of specific examples, which are merely exemplary and do not limit the scope of the present invention in any way.

Example 1

(1) Planting scindapsus aureus in an incubator with Moraded nutrient solution, dissolving cobalt chloride powder in distilled water after one week, adding the dissolved cobalt chloride powder into the nutrient solution, controlling the concentration of cobalt element in the finally obtained nutrient solution to be 180mg/L, culturing for 100 days, replacing the nutrient solution in the incubator in a 10-day period during the culture, keeping the pH value of the aqueous solution in the incubator to be 5.9-6.1 during the experiment, drying the scindapsus aureus in the incubator at 50 ℃ after the experiment is finished, and crushing to obtain biomass with the particle size of 15-16 mm.

Soaking the biomass in hydrochloric acid with the concentration of 0.1mol/L for 20min, then drying in an incubator at the temperature of 60 ℃ for 12h, sintering in a tubular muffle furnace according to the procedures of the sintering temperature of 450 ℃, the sintering time of 3h and the heating rate of 3 ℃/min, introducing argon gas into the tubular muffle furnace as protective gas in the sintering process, repeatedly washing the sintered product with distilled water until the pH value is 7 after the sintering reaction is finished, and drying in the incubator at the temperature of 100 ℃ for 8h to obtain the biochar.

(2) Mixing the biochar prepared in the step (1) with copper chloride and nickel nitrate according to a weight ratio of 1: 7: 30 the following operations are carried out:

putting the biochar in distilled water to form a suspension, dissolving copper chloride and nickel nitrate in deionized water, uniformly mixing the suspension containing the biochar with a solution containing metal salts of copper chloride and nickel nitrate, magnetically stirring for 24 hours at normal temperature, and drying at 80 ℃.

(3) The pyrolysis procedure for the tubular muffle furnace was set to:

the first stage is as follows: the pyrolysis temperature is 280 ℃, the pyrolysis time is 1h, and the heating rate is 1 ℃/min;

and a second stage: the pyrolysis temperature is 520 ℃, the pyrolysis time is 1.5h, and the heating rate is 3 ℃/min;

and a third stage: the pyrolysis temperature is 760 ℃, the pyrolysis time is 1h, and the heating rate is 7 ℃/min.

And (3) placing the sample dried in the step (2) in a set tubular muffle furnace, introducing a mixed gas of 90% (v%) argon and 10% (v%) hydrogen into the tubular muffle furnace in the pyrolysis process, and naturally cooling to room temperature after the reaction is finished to obtain the catalyst.

The TEM characterization of the obtained catalyst is shown in figure 1, SEM-Mapping of carbon (C), cobalt (Co), nickel (Ni), copper (Cu) and oxygen (O) in the obtained catalyst is shown in figure 2, the Co, Ni and Cu elements in the biochar are uniformly distributed, the C, Co, Ni, Cu and O elements are selected in an energy dispersive X-ray spectrometer (EDX) to analyze the content of the C, Co, Ni, Cu and O elements, and the obtained EDX data are shown as follows:

the XRD characterization of the obtained catalyst is shown in fig. 3, and has typical characteristics of intermetallic compounds, wherein, at 43.2 °, 51.5 °, 74.3 ° corresponds to cu-ni intermetallic compound, and at 44.2 °, 50.6 ° corresponds to co-cu intermetallic compound, indicating that cu-ni intermetallic compound and co-cu intermetallic compound are supported in the prepared catalyst.

Comparative example

Comparative example 1

A catalyst was prepared in a similar manner to example 1, except that: when the scindapsus aureus is cultivated, cobalt chloride is not added.

Comparative example 2

A catalyst was prepared in a similar manner to example 1, except that: copper chloride and nickel nitrate were not added.

Examples of the experiments

Experimental example 1

In three 250mL beakers, 100mL of a 50 mg/L2, 4-dichlorophenol solution was added 6mL of a 3g/L sodium persulfate solution, and the mixture was allowed to stand for 90min, 30mg of the catalyst prepared in example 1 and comparative example 1 was added thereto, and the reaction was carried out for 600min, and the change in the concentration of 2, 4-dichlorophenol was recorded.

Experimental example 2

100mL of 50mg/L rhodamine-B solution is respectively filled in three 250mL beakers, 6mL of 3g/L sodium persulfate solution is added, the mixture is kept still for 90min, 30mg of the catalysts prepared in example 1 and comparative example 1 are respectively added into the mixture, the reaction is carried out for 600min, and the concentration change of the rhodamine-B is recorded, and the result is shown in FIG. 2.

Experimental example 3

6mL of a sodium persulfate solution having a concentration of 3g/L was added to 100mL of sulfamethoxazole solution having a concentration of 50mg/L in three 250mL beakers, and the mixture was allowed to stand for 90min, 30mg of the catalysts prepared in example 1 and comparative example 1 were added thereto, respectively, and reacted for 600min, and the change in the concentration of sulfamethoxazole was recorded.

The results of the removal rates of organic contaminants by the catalysts prepared in example 1 and comparative examples 1 to 2 of experimental examples 1 to 3 are shown in table 1:

the invention has been described in detail with reference to the preferred embodiments and illustrative examples. It should be noted, however, that these specific embodiments are only illustrative of the present invention and do not limit the scope of the present invention in any way. Various modifications, equivalent substitutions and alterations can be made to the technical content and embodiments of the present invention without departing from the spirit and scope of the present invention, and these are within the scope of the present invention. The scope of the invention is defined by the appended claims.

Claims (10)

1. A method for preparing a bulk intermetallic supported catalyst, the method comprising: soaking soluble metal salt in the pore canal of the porous biochar, and performing pyrolysis to obtain the porous biochar;

the soluble metal salt comprises copper salt and nickel salt;

the porous biochar is enriched with cobalt, cobalt compounds are added in the plant growth process, plants absorb cobalt elements, the plants are collected and sintered to obtain the porous biochar, and the sintering is carried out in inert gas; the plant cultivation method is that plants are cultivated in a nutrient solution, and the concentration of cobalt element in the cobalt compound in the nutrient solution is 100-300 mg/L;

and the protective atmosphere during pyrolysis is reducing gas or mixed gas of inert gas and reducing gas.

2. The method according to claim 1, wherein the weight ratio of the copper salt, the nickel salt and the biochar is 1: (1-20): (10-100).

3. The method of claim 1, wherein the cobalt compound comprises ionic cobalt and/or complex cobalt.

4. A method according to claim 3, wherein the cobalt compound is ionic cobalt.

5. The method according to claim 1, wherein the sintering temperature is 300 to 600 ℃, the sintering time is 0.5 to 5 hours, and the temperature rise rate is 1 to 6 ℃/min.

6. The method of claim 1, wherein prior to sintering, the comminuted biological acid is treated to increase the surface acidity and pore structure of the biochar, the acid being a strong acid.

7. The method of claim 6, wherein the acid is hydrochloric acid.

8. The method according to claim 1, wherein the immersion time is 5 to 48 hours.

9. The method according to claim 6, wherein the acid treatment time is 5 to 60 min.

10. The method of claim 1, wherein the pyrolyzing comprises:

the first stage is as follows: the pyrolysis temperature is 200-350 ℃, the pyrolysis time is 0.1-2 h, and the heating rate is 0.5-3 ℃/min;

and a second stage: the pyrolysis temperature is 400-600 ℃, the pyrolysis time is 0.5-3 h, and the heating rate is 1-5 ℃/min;

and a third stage: the pyrolysis temperature is 650-900 ℃, the pyrolysis time is 0.1-1 h, and the heating rate is 5-9 ℃/min.

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