Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below in connection with the embodiments of the present invention. It will be apparent that the described embodiments are some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention provides a preparation method of a cerium-zirconium oxide supported palladium-gold catalyst in a first aspect, which comprises the following steps:
(1) Mixing cerium nitrate hexahydrate and zirconyl nitrate hydrate with water uniformly to obtain a mixed solution, adding sodium hydroxide solution into the mixed solution to perform hydrothermal reaction to obtain an oxide, and calcining the oxide to obtain cerium zirconium oxide Ce x Zr y O 2 Wherein x+y=1, and 0 < y < 1; in the invention, cerium nitrate hexahydrate is used as a cerium source, zirconium oxynitrate hydrate is used as a zirconium source, and the cerium zirconium oxide Ce is obtained through hydrothermal reaction and calcination x Zr y O 2 By adjusting the molar ratio of the cerium source and the zirconium source, the cerium-zirconium oxide Ce with different values of x and y can be obtained x Zr y O 2 In the present invention, it is preferable that 0.25.ltoreq.y.ltoreq.0.75; in some specific embodiments, cerium nitrate hexahydrate and zirconium oxynitrate hydrate are uniformly mixed with water to obtain a mixed solution, then a sodium hydroxide solution is added into the mixed solution, stirring is carried out for 20-40 min at the room temperature of 15-35 ℃ and the rotating speed of 300-800 r/min to obtain an emulsion, the emulsion is subjected to hydrothermal reaction to obtain an oxide, and the oxide is calcined to obtain cerium zirconium oxide Ce x Zr y O 2 In the invention, after emulsion is formed, hydrothermal reaction is carried out, so that the effect of nucleation and crystal growth is achieved; in the present invention, for example, after the completion of the hydrothermal reaction, the obtained oxide is washed and dried and then calcined, preferably, before the calcination, the oxide is centrifugally washed and then dried in vacuum at 40 to 80℃for 8 to 18 hours, and the centrifugal washing may be, for example, deionized waterCentrifugal washing for 4-8 times;
(2) Dispersing a palladium salt solution into a palladium salt dispersion liquid by using water, adding cerium-zirconium oxide into the palladium salt dispersion liquid, stirring, and adding a reducing agent for reduction to obtain a cerium-zirconium oxide supported palladium composite material; the invention does not limit the dosage of each component in the step (2), and can be adjusted according to the loading capacity of the palladium nano particles; in the invention, after reduction is finished, the cerium-zirconium oxide supported palladium composite material is obtained through centrifugal washing and drying (for example, drying at 40-80 ℃); in the step (2) of the present invention, the stirring and/or the reduction may be performed, for example, at a room temperature of 15 to 35 ℃ and a rotation speed of 300 to 800r/min, the stirring time may be, for example, 6 to 15 hours, and the reduction time may be, for example, 0.5 to 2 hours;
(3) Adding a cerium-zirconium oxide supported palladium composite material and a precipitant into the gold salt solution for reaction to obtain the cerium-zirconium oxide supported palladium-gold composite material;
(4) Placing the cerium-zirconium oxide supported palladium-gold composite material into an etching solution to etch (gold etching) to prepare a cerium-zirconium oxide supported palladium-gold catalyst; in the invention, the etching temperature and time are adjustable; in the invention, the cerium-zirconium oxide loaded palladium-gold composite material is placed in an etching solution to etch gold, and gold attached to the surface of the cerium-zirconium oxide is etched, so that gold nanoclusters can be generated, more catalytic active sites can be provided, the catalytic activity can be effectively improved, and the control of the reaction selectivity can be realized, so that the catalyst shows good hydrogen selectivity; in addition, the high-energy sites on the surface of the gold nanoclusters have higher electron affinity, and can better adsorb and stabilize toxic substances, so that the antitoxic performance of the catalyst is effectively improved, and the stability and the service life of the formic acid hydrogen production catalyst are improved.
The invention firstly utilizes a synthesized zirconium-doped cerium oxide material (cerium zirconium oxide Ce) x Zr y O 2 ) The oxygen vacancy ability and corrosion resistance of the carrier material can be simultaneously improved, and the activity and stability of the carrier are improved; secondly, by loading gold and palladium, double is generatedThe functional composite sites enable a large amount of palladium ions to be adsorbed on the surface of the catalyst through palladium salt solution, the palladium ions are reduced into palladium particles through reducing agents, then the palladium particles are treated in dispersed gold salt solution by using precipitating agents, and finally gold etching reaction is carried out in etching solution, so that the cerium-zirconium oxide supported palladium-gold catalyst is prepared, the catalytic performance of the catalyst is greatly improved, the selectivity of the catalyst in formic acid dehydrogenation reaction is improved, the carbon monoxide (CO) poisoning resistance is improved, and the stability and the service life of the formic acid hydrogen production catalyst are improved; by adopting a double-functional site design, a gold (Au) nano heterojunction material is introduced, and meanwhile, the activity and carbon monoxide poisoning resistance of the catalyst are improved.
According to some preferred embodiments, in step (1): the molar ratio of the cerium nitrate hexahydrate to the amount of the zirconyl nitrate hydrate is (1-3): (1-3) (e.g., 1:1, 1:2, 1:3, 2:1, or 3:1), preferably (1-3): 1, more preferably 3:1; in the present invention, the molar ratio of the cerium nitrate hexahydrate to the amount of zirconyl nitrate hydrate is preferably (1 to 3): (1-3), if the amount of cerium nitrate hexahydrate or zirconium oxynitrate hydrate is too much or too little, the activity and stability of the obtained cerium zirconium oxide as a carrier can be affected, so that the catalytic activity and stability of the prepared cerium zirconium oxide supported palladium gold catalyst are affected; the mixed solution contains 20-40 percent (for example, 20%, 25%, 30%, 35% or 40%) of the sum of the mass percentages of cerium nitrate hexahydrate and zirconyl nitrate hydrate; the concentration of the sodium hydroxide solution is 8-12 mol/L (for example 8, 9, 10, 11 or 12 mol/L); in the present invention, the sodium hydroxide solution refers to an aqueous sodium hydroxide solution unless otherwise specified; the volume ratio of the mixed solution to the sodium hydroxide solution is 1: (1-2) (e.g., 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, or 1:2); the temperature of the hydrothermal reaction is 150-200 ℃ (e.g. 150 ℃, 160 ℃, 180 ℃, 190 ℃ or 200 ℃), and the time of the hydrothermal reaction is 12-24 hours (e.g. 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23 or 24 hours); the calcination is performed in an air atmosphere; and/or the calcination temperature is 400-800 ℃ (e.g. 400 ℃, 450 ℃, 500 ℃, 550 ℃, 600 ℃, 650 ℃, 700 ℃, 750 ℃ or 800 ℃), and the calcination time is 4-8 hours (e.g. 4, 5, 6, 7 or 8 hours).
According to some preferred embodiments, in step (2): the palladium salt solution is a palladium chloride acid solution, the palladium chloride acid solution is prepared by hydrochloric acid with the pH value of 0-2 and palladium dichloride, and the concentration of the palladium dichloride contained in the palladium chloride acid solution is 0.05-0.15 mol/L (for example, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14 or 0.15 mol/L); and/or the volume ratio of the water to the palladium salt solution is (50-80): 1 (e.g., 50:1, 55:1, 60:1, 65:1, 70:1, 75:1, or 80:1).
According to some preferred embodiments, in step (2): the mass ratio of the cerium zirconium oxide to the reducing agent is (130-150): 1 (e.g., 130:1, 135:1, 140:1, 145:1, or 150:1); the molar ratio of palladium contained in the palladium salt solution to the reducing agent is 1: (3-12) (e.g., 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, 1:8.5, 1:9, 1:9.5, 1:10, 1:10.5, 1:11, 1:11.5, or 1:12); the reducing agent is one or more of sodium borohydride, potassium borohydride and hydrazine hydrate; the stirring time is 6-15 h (such as 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15 h), and the stirring rotating speed is 300-800 r/min (such as 300, 400, 500, 600, 700 or 800 r/min); and/or the time of the reduction is 0.5 to 2 hours (e.g., 0.5, 1, 1.5 or 2 hours).
According to some preferred embodiments, in step (3): the gold salt solution is chloroauric acid aqueous solution, and the concentration of the chloroauric acid aqueous solution is 0.00002-0.00004 mol/L (for example, 0.00002, 0.00003 or 0.00004 mol/L); and/or the precipitant is one or more of urea, glucose and ascorbic acid; and/or the reaction is first heat treated at 80-100 ℃ (e.g., 80 ℃, 85 ℃, 90 ℃, 95 ℃, or 100 ℃) for 6-10 hours (e.g., 6, 7, 8, 9, or 10 hours), and then aged at 15-35 ℃ (e.g., 15 ℃, 20 ℃, 25 ℃, 30 ℃, or 35 ℃) for 10-15 hours (e.g., 10, 11, 12, 13, 14, or 15 hours).
According to some preferred embodiments, the molar ratio of palladium contained in the palladium salt solution to gold contained in the gold salt solution is (10 to 35): 1 (e.g., 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1, 25:1, 30:1, or 35:1); in the present invention, the molar ratio of palladium contained in the palladium salt solution to gold contained in the gold salt solution is preferably (10 to 35): and 1, the cerium-zirconium oxide supported palladium-gold catalyst with better palladium-gold double-functional site composite effect can be obtained, so that the catalytic activity, the catalytic stability and the like of the cerium-zirconium oxide supported palladium-gold catalyst are improved.
According to some preferred embodiments, the molar ratio of gold contained in the gold salt solution to the precipitant is 1: (110-140) (e.g., 1:110, 1:115, 1:120, 1:125, 1:130, 1:135, or 1:140), preferably 1:125.
According to some preferred embodiments, in step (4): the etching solution is an etchant aqueous solution with pH value of 11-13; the etchant contained in the etchant aqueous solution is sodium cyanide and/or sodium cyanate; the etchant aqueous solution contains 1-3% of etchant (such as 1%, 1.5%, 2%, 2.5% or 3%); in the present invention, for example, an alkaline regulator (e.g., sodium hydroxide and/or potassium hydroxide) may be used to adjust the pH of the aqueous etchant solution to 11 to 13, preferably to 12, and the alkaline regulator may be added directly to the aqueous etchant solution or added to the aqueous etchant solution in the form of an aqueous solution, and the concentration of the aqueous alkaline regulator is, for example, 0.05 to 0.2mol/L, and the amount of the alkaline regulator or the aqueous alkaline regulator is not particularly limited, so that the pH of the aqueous etchant solution may be 11 to 13; the invention does not limit the dosage of the etching solution, and can ensure that the cerium-zirconium oxide loaded palladium-gold composite material is completely immersed in the etching solution.
According to some preferred embodiments, in step (4): the etching temperature is 15-35 ℃, and the etching time is 5-120 min; in the present invention, the etching time may be adjusted according to the concentration of the etchant solution, the gold loading amount, etc., preferably the etching time is 5 to 120min, more preferably the etching time is 5 to 20min.
According to some specific embodiments, the preparation of the cerium zirconium oxide supported palladium gold catalyst comprises the following steps:
(1) mixing cerium nitrate hexahydrate and zirconium oxynitrate hydrate uniformly by deionized water to obtain a mixed solution, dissolving flaky sodium hydroxide in deionized water to obtain a sodium hydroxide aqueous solution, adding the sodium hydroxide solution into the mixed solution, stirring for 20-40 min at the temperature of 15-35 ℃ and the rotating speed of 300-800 r/min to obtain an emulsion, transferring the emulsion into a hydrothermal reaction kettle for hydrothermal reaction, and centrifugally washing and drying after the reaction is finished to obtain an oxide, wherein the centrifugal washing is carried out for 6 times by deionized water, the drying is carried out for example, vacuum drying is carried out for 8-18 h at the temperature of 60-80 ℃, and then calcining treatment is carried out in air atmosphere to obtain cerium zirconium oxide Ce x Zr y O 2 。
(2) Dispersing palladium salt solution into palladium salt dispersion liquid by using water, adding cerium-zirconium oxide into the palladium salt dispersion liquid, stirring, adding a reducing agent for reduction, centrifugally washing, and vacuum drying to obtain the cerium-zirconium oxide supported palladium composite material.
(3) Adding the cerium-zirconium oxide supported palladium composite material into the gold salt solution, stirring for 0.5-2 h, adding a precipitant, heating at 80-100 ℃ for 6-10 h, aging at 15-35 ℃ for 10-15 h, and centrifugally washing and drying to obtain the cerium-zirconium oxide supported palladium-gold composite material.
(4) Placing the cerium-zirconium oxide supported palladium-gold composite material into an etching solution for etching, and after etching, centrifugally washing and drying to obtain the cerium-zirconium oxide supported palladium-gold catalyst; the etching solution is formed by mixing sodium cyanide aqueous solution with the mass fraction of 2% and sodium hydroxide aqueous solution with the concentration of 0.1mol/L, and the sodium hydroxide aqueous solution is used for adjusting the pH of the etching solution to 11-13. The conditions for centrifugal washing and drying are not particularly limited in the present invention, and those skilled in the art can select the conditions as required, and the drying is, for example, 40 to 80℃for 8 to 18 hours.
The present invention provides in a second aspect a cerium zirconium oxide supported palladium gold catalyst prepared by the preparation method of the present invention described in the first aspect.
The invention provides in a third aspect the use of a cerium zirconium oxide supported palladium gold catalyst prepared by the preparation method of the invention in the first aspect in hydrogen production from formic acid.
In the invention, when the cerium-zirconium oxide supported palladium-gold catalyst is adopted to carry out formic acid hydrogen production, the cerium-zirconium oxide supported palladium-gold catalyst and hydrogen production stock solution are uniformly mixed to carry out hydrogen production reaction; specifically, deionized water is used for carrying out ultrasonic treatment on a cerium-zirconium oxide supported palladium-gold catalyst for 5-15 min, and then the cerium-zirconium oxide supported palladium-gold catalyst is added into hydrogen production stock solution to be uniformly mixed for hydrogen production reaction; in the invention, for example, the hydrogen production stock solution contains formic acid and/or sodium formate, the hydrogen production stock solution takes water as a solvent, the concentration of the formic acid in the hydrogen production stock solution is 1-3 mol/L, and/or the concentration of the sodium formate in the hydrogen production stock solution is 3-7 mol/L, and the consumption of the cerium-zirconium oxide supported palladium-gold catalyst is as follows: adding 0.01-0.03 g of cerium-zirconium oxide supported palladium-gold catalyst into each 20mL hydrogen production stock solution; the temperature of the hydrogen production reaction is 40-80 ℃.
The invention will be further illustrated by way of example, but the scope of the invention is not limited to these examples. The present invention is capable of other and further embodiments and its several details are capable of modification and variation in accordance with the present invention, as will be apparent to those skilled in the art, without departing from the spirit and scope of the invention as defined in the appended claims.
Example 1
(1) Uniformly mixing cerium nitrate hexahydrate and zirconyl nitrate hydrate by using 25mL of deionized water to obtain a mixed solution, dissolving 15g of sodium hydroxide in 35mL of deionized water to obtain a sodium hydroxide aqueous solution, wherein the molar ratio of the cerium nitrate hexahydrate to the zirconyl nitrate hydrate is 3:1, and the mixed solution contains the cerium nitrate hexahydrate and the zirconyl nitrate hydrate, wherein the sum of the mass percentages of the cerium nitrate hexahydrate and the zirconyl nitrate hydrate is 30%; then adding the sodium hydroxide aqueous solution into the mixed solution, stirring for 30min at the room temperature of 25 ℃ and the rotating speed of 400r/min to obtain emulsion, then transferring the emulsion into a hydrothermal reaction kettle, performing hydrothermal reaction for 24h at the rotating speed of 180 ℃ and the rotating speed of 400r/min, after the reaction is finished, performing centrifugal washing and drying to obtain oxide, and calcining the oxide in the air atmosphere at the temperature of 500 ℃ for 5h to obtain cerium-zirconium oxide.
(2) Dispersing 0.6mL of a chloropalladite solution (palladium salt solution) containing 0.1mol/L of palladium dichloride with 40mL of deionized water to obtain a chloropalladite dispersion (palladium salt dispersion), wherein the pH of the chloropalladite solution is 1; then adding 2g of cerium zirconium oxide into the chloropalladac acid dispersion liquid, stirring for 12 hours at the room temperature of 25 ℃ and the rotating speed of 400r/min, adding 13.78mg of sodium borohydride, reducing for 0.5 hour at the room temperature of 25 ℃ and the rotating speed of 400r/min, and centrifugally washing and drying to obtain the cerium zirconium oxide supported palladium composite material.
(3) Preparing chloroauric acid into a chloroauric acid solution with the concentration of 0.000032mol/L by using 100mL of deionized water; then adding the cerium-zirconium oxide supported palladium composite material obtained in the step (2) into chloroauric acid solution, stirring for 1h at the room temperature of 25 ℃ and the rotating speed of 400r/min, adding 24mg of urea, heating for 8h at the temperature of 90 ℃ and the rotating speed of 400r/min, aging and standing for 12h at the temperature of 25 ℃, and centrifugally washing and drying to obtain the cerium-zirconium oxide supported palladium-gold composite material.
(4) Placing the cerium-zirconium oxide supported palladium-gold composite material in 100mL of etching solution, etching for 10min at the room temperature of 25 ℃, and after etching, centrifugally washing and drying to obtain the cerium-zirconium oxide supported palladium-gold catalyst; the preparation of the etching solution comprises the following steps: adding sodium hydroxide aqueous solution with the concentration of 0.1mol/L into sodium cyanide aqueous solution with the mass fraction of 2%, and regulating the pH value of the sodium cyanide aqueous solution to be 12 to obtain the etching solution.
Example 2
(1) Uniformly mixing cerium nitrate hexahydrate and zirconyl nitrate hydrate by using 25mL of deionized water to obtain a mixed solution, dissolving 15g of sodium hydroxide in 35mL of deionized water to obtain a sodium hydroxide aqueous solution, wherein the molar ratio of the cerium nitrate hexahydrate to the zirconyl nitrate hydrate is 1:3, and the mixed solution contains the cerium nitrate hexahydrate and the zirconyl nitrate hydrate, and the sum of the mass percentages of the cerium nitrate hexahydrate and the zirconyl nitrate hydrate is 30%; then adding the sodium hydroxide aqueous solution into the mixed solution, stirring for 30min at the room temperature of 25 ℃ and the rotating speed of 400r/min to obtain emulsion, then transferring the emulsion into a hydrothermal reaction kettle, performing hydrothermal reaction for 24h at the rotating speed of 180 ℃ and the rotating speed of 400r/min, after the reaction is finished, performing centrifugal washing and drying to obtain oxide, and calcining the oxide in the air atmosphere at the temperature of 500 ℃ for 5h to obtain cerium-zirconium oxide.
(2) Dispersing 0.32mL of a chloropalladite solution (palladium salt solution) containing 0.1mol/L of palladium dichloride with 40mL of deionized water to obtain a chloropalladite dispersion (palladium salt dispersion), wherein the pH of the chloropalladite solution is 1; then adding 1.07g of cerium zirconium oxide into the chloropalladac acid dispersion liquid, stirring for 12 hours at the room temperature of 25 ℃ and the rotating speed of 400r/min, adding 7.35mg of sodium borohydride, reducing for 0.5 hour at the room temperature of 25 ℃ and the rotating speed of 400r/min, and centrifugally washing and drying to obtain the cerium zirconium oxide supported palladium composite material.
(3) The procedure is as in step (3) of example 1.
(4) The procedure is as in step (4) of example 1.
Example 3
(1) Uniformly mixing cerium nitrate hexahydrate and zirconyl nitrate hydrate by using 25mL of deionized water to obtain a mixed solution, dissolving 15g of sodium hydroxide in 35mL of deionized water to obtain a sodium hydroxide aqueous solution, wherein the molar ratio of the cerium nitrate hexahydrate to the zirconyl nitrate hydrate is 1:1, and the mixed solution contains 30 percent of the sum of the mass percentages of the cerium nitrate hexahydrate and the zirconyl nitrate hydrate; then adding the sodium hydroxide aqueous solution into the mixed solution, stirring for 30min at the room temperature of 25 ℃ and the rotating speed of 400r/min to obtain emulsion, then transferring the emulsion into a hydrothermal reaction kettle, performing hydrothermal reaction for 24h at the rotating speed of 180 ℃ and the rotating speed of 400r/min, after the reaction is finished, performing centrifugal washing and drying to obtain oxide, and calcining the oxide in the air atmosphere at the temperature of 500 ℃ for 5h to obtain cerium-zirconium oxide.
(2) Dispersing 1.12mL of a chloropalladite solution (palladium salt solution) containing 0.1mol/L of palladium dichloride with 40mL of deionized water to obtain a chloropalladite dispersion (palladium salt dispersion), wherein the pH of the chloropalladite solution is 1; then adding 3.733g of cerium zirconium oxide into the chloropalladac acid dispersion liquid, stirring for 12 hours at the room temperature of 25 ℃ and the rotating speed of 400r/min, adding 25.72mg of sodium borohydride, reducing for 0.5 hour at the room temperature of 25 ℃ and the rotating speed of 400r/min, and centrifugally washing and drying to obtain the cerium zirconium oxide supported palladium composite material.
(3) The procedure is as in step (3) of example 1.
(4) The procedure is as in step (4) of example 1.
Example 4
Example 4 is substantially the same as example 1 except that:
the step (1) is as follows: uniformly mixing cerium nitrate hexahydrate and zirconyl nitrate hydrate by using 25mL of deionized water to obtain a mixed solution, dissolving 15g of sodium hydroxide in 35mL of deionized water to obtain a sodium hydroxide aqueous solution, wherein the molar ratio of the cerium nitrate hexahydrate to the zirconyl nitrate hydrate is 0.5:3, and the mixed solution contains 30% of the sum of the mass percentages of the cerium nitrate hexahydrate and the zirconyl nitrate hydrate; then adding the sodium hydroxide aqueous solution into the mixed solution, stirring for 30min at the room temperature of 25 ℃ and the rotating speed of 400r/min to obtain emulsion, then transferring the emulsion into a hydrothermal reaction kettle, performing hydrothermal reaction for 24h at the rotating speed of 180 ℃ and the rotating speed of 400r/min, after the reaction is finished, performing centrifugal washing and drying to obtain oxide, and calcining the oxide in the air atmosphere at the temperature of 500 ℃ for 5h to obtain cerium-zirconium oxide.
Example 5
Example 5 is substantially the same as example 1 except that:
the step (1) is as follows: uniformly mixing cerium nitrate hexahydrate and zirconyl nitrate hydrate by using 25mL of deionized water to obtain a mixed solution, dissolving 15g of sodium hydroxide in 35mL of deionized water to obtain a sodium hydroxide aqueous solution, wherein the molar ratio of the cerium nitrate hexahydrate to the zirconyl nitrate hydrate is 3:0.5, and the mixed solution contains 30% of the sum of the mass percentages of the cerium nitrate hexahydrate and the zirconyl nitrate hydrate; then adding the sodium hydroxide aqueous solution into the mixed solution, stirring for 30min at the room temperature of 25 ℃ and the rotating speed of 400r/min to obtain emulsion, then transferring the emulsion into a hydrothermal reaction kettle, performing hydrothermal reaction for 24h at the rotating speed of 180 ℃ and the rotating speed of 400r/min, after the reaction is finished, performing centrifugal washing and drying to obtain oxide, and calcining the oxide in the air atmosphere at the temperature of 500 ℃ for 5h to obtain cerium-zirconium oxide.
Example 6
Example 6 is substantially the same as example 1 except that:
the step (2) is as follows: dispersing 0.16mL of a chloropalladite solution (palladium salt solution) containing 0.1mol/L of palladium dichloride with 40mL of deionized water to obtain a chloropalladite dispersion (palladium salt dispersion), wherein the pH of the chloropalladite solution is 1; then adding 0.53g of cerium zirconium oxide into the chloropalladac acid dispersion liquid, stirring for 12 hours at the room temperature of 25 ℃ and the rotating speed of 400r/min, adding 3.675mg of sodium borohydride, reducing for 0.5 hour at the room temperature of 25 ℃ and the rotating speed of 400r/min, and centrifugally washing and drying to obtain the cerium zirconium oxide supported palladium composite material.
Example 7
Example 7 is substantially the same as example 1 except that:
the step (2) is as follows: dispersing 1.28mL of a chloropalladite solution (palladium acid solution) containing 0.1mol/L of palladium dichloride with 40mL of deionized water to obtain a chloropalladite dispersion (palladium acid dispersion), wherein the pH of the chloropalladite solution is 1; then adding 4.27g of cerium zirconium oxide into the chloropalladac acid dispersion liquid, stirring for 12 hours at the room temperature of 25 ℃ and the rotating speed of 400r/min, adding 29.4mg of sodium borohydride, reducing for 0.5 hour at the room temperature of 25 ℃ and the rotating speed of 400r/min, and centrifugally washing and drying to obtain the cerium zirconium oxide supported palladium composite material.
Comparative example 1
(1) Uniformly mixing cerium dioxide powder and zirconium dioxide powder to obtain composite powder; in the composite powder, the molar ratio of the cerium oxide powder to the zirconium dioxide powder is 3:1.
(2) Dispersing 0.6mL of a chloropalladite solution (palladium salt solution) containing 0.1mol/L of palladium dichloride with 40mL of deionized water to obtain a chloropalladite dispersion (palladium salt dispersion), wherein the pH of the chloropalladite solution is 1; then adding 2g of composite powder into the chloropalladac acid dispersion liquid, stirring for 12 hours at the room temperature of 25 ℃ and the rotating speed of 400r/min, adding 13.78mg of sodium borohydride, reducing for 0.5 hour at the room temperature of 25 ℃ and the rotating speed of 400r/min, and centrifugally washing and drying to obtain the oxide-loaded palladium composite material.
(3) Preparing chloroauric acid into a chloroauric acid solution with the concentration of 0.000032mol/L by using 100mL of deionized water; then adding the oxide load palladium composite material obtained in the step (2) into chloroauric acid solution, stirring for 1h at the room temperature of 25 ℃ and the rotating speed of 400r/min, then adding 24mg of urea, heating for 8h at the temperature of 90 ℃ and the rotating speed of 400r/min, aging and standing for 12h at the temperature of 25 ℃, and centrifugally washing and drying to obtain the oxide load palladium-gold composite material.
(4) Placing the oxide supported palladium-gold composite material in 100mL of etching solution, etching for 10min at the room temperature of 25 ℃, and after etching, centrifugally washing and drying to obtain the oxide supported palladium-gold catalyst; the preparation of the etching solution comprises the following steps: adding sodium hydroxide aqueous solution with the concentration of 0.1mol/L into sodium cyanide aqueous solution with the mass fraction of 2%, and regulating the pH value of the sodium cyanide aqueous solution to be 12 to obtain the etching solution.
Comparative example 2
(1) Uniformly mixing cerium nitrate hexahydrate and zirconyl nitrate hydrate by using 25mL of deionized water to obtain a mixed solution, dissolving 15g of sodium hydroxide in 35mL of deionized water to obtain a sodium hydroxide aqueous solution, wherein the molar ratio of the cerium nitrate hexahydrate to the zirconyl nitrate hydrate is 3:1, and the mixed solution contains the cerium nitrate hexahydrate and the zirconyl nitrate hydrate, wherein the sum of the mass percentages of the cerium nitrate hexahydrate and the zirconyl nitrate hydrate is 30%; then adding the sodium hydroxide aqueous solution into the mixed solution, stirring for 30min at the room temperature of 25 ℃ and the rotating speed of 400r/min to obtain emulsion, then transferring the emulsion into a hydrothermal reaction kettle, performing hydrothermal reaction for 24h at the rotating speed of 180 ℃ and the rotating speed of 400r/min, after the reaction is finished, performing centrifugal washing and drying to obtain oxide, and calcining the oxide in the air atmosphere at the temperature of 500 ℃ for 5h to obtain cerium-zirconium oxide.
(2) Dispersing 0.632mL of a chloropalladite solution (palladium salt solution) containing 0.1mol/L of palladium dichloride with 40mL of deionized water to obtain a chloropalladite dispersion (palladium salt dispersion), wherein the pH of the chloropalladite solution is 1; then adding 2g of cerium zirconium oxide into the chloropalladac acid dispersion liquid, stirring for 12 hours at the room temperature of 25 ℃ at the rotating speed of 400r/min, adding 13.78mg of sodium borohydride, reducing for 0.5 hour at the room temperature of 25 ℃ at the rotating speed of 400r/min, and centrifugally washing and drying to obtain the cerium zirconium oxide supported palladium catalyst.
Comparative example 3
(1) Uniformly mixing cerium nitrate hexahydrate and zirconyl nitrate hydrate by using 25mL of deionized water to obtain a mixed solution, dissolving 15g of sodium hydroxide in 35mL of deionized water to obtain a sodium hydroxide aqueous solution, wherein the molar ratio of the cerium nitrate hexahydrate to the zirconyl nitrate hydrate is 3:1, and the mixed solution contains the cerium nitrate hexahydrate and the zirconyl nitrate hydrate, wherein the sum of the mass percentages of the cerium nitrate hexahydrate and the zirconyl nitrate hydrate is 30%; then adding the sodium hydroxide aqueous solution into the mixed solution, stirring for 30min at the room temperature of 25 ℃ and the rotating speed of 400r/min to obtain emulsion, then transferring the emulsion into a hydrothermal reaction kettle, performing hydrothermal reaction for 24h at the rotating speed of 180 ℃ and the rotating speed of 400r/min, after the reaction is finished, performing centrifugal washing and drying to obtain oxide, and calcining the oxide in the air atmosphere at the temperature of 500 ℃ for 5h to obtain cerium-zirconium oxide.
(2) Dispersing 0.6mL of a chloropalladite solution (palladium salt solution) containing 0.1mol/L of palladium dichloride with 40mL of deionized water to obtain a chloropalladite dispersion (palladium salt dispersion), wherein the pH of the chloropalladite solution is 1; then adding 2g of cerium zirconium oxide into the chloropalladac acid dispersion liquid, stirring for 12 hours at the room temperature of 25 ℃ and the rotating speed of 400r/min, adding 13.78mg of sodium borohydride, reducing for 0.5 hour at the room temperature of 25 ℃ and the rotating speed of 400r/min, and centrifugally washing and drying to obtain the cerium zirconium oxide supported palladium composite material.
(3) Preparing chloroauric acid into a chloroauric acid solution with the concentration of 0.000032mol/L by using 100mL of deionized water; then adding the cerium-zirconium oxide supported palladium composite material obtained in the step (2) into chloroauric acid solution, stirring for 1h at the room temperature of 25 ℃ and the rotating speed of 400r/min, adding 24mg of urea, heating for 8h at the temperature of 90 ℃ and the rotating speed of 400r/min, aging and standing for 12h at the temperature of 25 ℃, and centrifugally washing and drying to obtain the cerium-zirconium oxide supported palladium-gold catalyst.
In the above examples and comparative examples, if the amount of cerium-zirconium oxide is relatively large, the respective corresponding steps (1) may be repeated a plurality of times until the desired amount of cerium-zirconium oxide is obtained and the subsequent steps are performed.
The invention tests the catalytic effect of the hydrogen production reaction of formic acid on the catalysts finally prepared in each example and each comparative example, and the hydrogen production test method of formic acid comprises the following steps:
preparing a mixed solution of formic acid and sodium formate by using water as a solvent, wherein 200mL of a hydrogen production stock solution contains 1mol/L formic acid, and 3mol/L sodium formate; ultrasonic dispersing 0.1g of catalyst with 5mL of deionized water for 10min to obtain catalyst dispersion; then adding a catalyst dispersion liquid into 200mL of the hydrogen production stock solution to carry out hydrogen production reaction; after hydrogen production reaction is carried out at 80 ℃ for 10min, a conversion frequency value (TOF value) is obtained, the result is shown in table 1, and the result of measuring the content of CO in the gas product in the first 10min is shown in table 1, wherein the content of CO in the gas product is detected by a gas chromatograph equipped with a hydrogen flame detector.
TABLE 1
Examples
|
TOF(h -1 )
|
CO content (ppm)
|
Example 1
|
4870
|
3.1
|
Example 2
|
3069
|
6.5
|
Example 3
|
5067
|
12.5
|
Example 4
|
2125
|
4.8
|
Example 5
|
3913
|
4.5
|
Example 6
|
4568
|
2.5
|
Example 7
|
4650
|
18.5
|
Comparative example 1
|
1550
|
98.3
|
Comparative example 2
|
4450
|
22.5
|
Comparative example 3
|
4535
|
19.5 |
The catalyst prepared in each example and each comparative example is also used for 3-cycle catalytic formic acid hydrogen production, after each reaction for 10min according to the formic acid hydrogen production test method of the invention, the catalyst is centrifuged and washed with water, and the formic acid hydrogen production test is repeatedly carried out for 3 times, so that the 3 rd cycle conversion frequency value (TOF value) result is obtained, and the first formic acid hydrogen production test is recorded as the 1 st cycle in Table 2 as shown in Table 2.
TABLE 2
As can be seen from the data in tables 1 and 2, the cerium-zirconium oxide supported palladium-gold catalyst prepared by the invention has the advantages of high catalytic efficiency, good catalytic stability and effective carbon monoxide poisoning resistance in hydrogen production by formic acid; the conversion frequency value (TOF value) of the cerium-zirconium oxide supported palladium-gold catalyst prepared in some preferred embodiments of the invention can reach 4500h -1 The carbon monoxide poisoning resistance is high, the carbon monoxide content in the gas product is not higher than 20ppm and even can be lower than 5ppm, the catalytic stability of the cerium-zirconium oxide supported palladium-gold catalyst is good, and after 3 times of circulating catalytic formic acid hydrogen production, the TOF value retention rate can still reach more than 58% and even can reach as high as 81.1%, so that the catalyst has quite high catalytic stability for the formic acid hydrogen production catalyst.
The invention is not described in detail in a manner known to those skilled in the art.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.