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CN-121972222-A - Amino-functionalized palladium-silver alloy catalyst regulated and controlled by citric acid coordination, and preparation method and application thereof

CN121972222ACN 121972222 ACN121972222 ACN 121972222ACN-121972222-A

Abstract

The invention discloses an amino-functional palladium-silver alloy catalyst for coordination regulation and control of citric acid, and a preparation method and application thereof. According to the invention, nitrogen-doped carbon is used as a carrier, and the palladium-silver alloy catalyst is constructed through coordination-limited-area in-situ reduction of citric acid. According to the invention, citric acid is introduced to realize the synergy of sub-nano-scale dispersion and efficient interfacial mass transfer through the double synergistic regulation and control of the size and the interface, the coordination effect of the citric acid enables palladium-silver alloy to realize sub-nano-scale superfine dispersion, and the polycarboxylic acid is used as a competitive hydrogen bond acceptor/donor, so that an interface hydrogen bond network can be effectively broken, and compact air film formation is inhibited from the source. The mechanism ensures that the catalyst is always and fully contacted with a mixed aqueous solution containing formic acid and formate and quickly releases hydrogen in the hydrogen production reaction of the formic acid dehydrogenation, so that the catalyst has excellent anti-poisoning cycle stability while maintaining high intrinsic activity, and solves the technical problem that the high activity and long-term stability are difficult to be compatible.

Inventors

  • ZHANG YU
  • CHEN YIBIN
  • LIU YA

Assignees

  • 华东理工大学

Dates

Publication Date
20260505
Application Date
20260204

Claims (10)

  1. 1. The amino-functionalized palladium-silver alloy catalyst regulated and controlled by citric acid coordination is characterized by comprising a nitrogen-doped carbon carrier and citric acid-modified PdAG alloy nano particles anchored on the surface of the nitrogen-doped carbon carrier, wherein the catalyst is prepared by a citric acid-assisted coordination-limited-area in-situ reduction strategy and is obtained by forming a metal palladium-silver-citric acid coordination complex from a palladium precursor, a silver precursor and citric acid in a liquid phase, and then reducing the metal palladium-silver-citric acid coordination complex into a citric acid coordination structure in situ under the action of a reducing agent and anchoring the citric acid coordination structure on the surface of the nitrogen-doped carbon carrier.
  2. 2. A method for preparing the amino-functionalized palladium-silver alloy catalyst coordinated and controlled by citric acid as claimed in claim 1, which comprises the following steps: S1, adding a carbon material and a nitrogen source into deionized water, stirring and mixing, and then placing the mixture in an inert atmosphere for high-temperature calcination to obtain a nitrogen-doped carbon carrier; S2, dissolving a palladium precursor and a silver precursor in a citric acid solution, and stirring for reaction to obtain a metal palladium-silver-citric acid complex solution; S3, dispersing a nitrogen-doped carbon carrier in a solvent to obtain a carrier suspension, mixing the carrier suspension with the metal palladium-silver-citric acid complex solution, and stirring to enable the metal palladium-silver-citric acid complex to be adsorbed on the surface of the nitrogen-doped carrier to obtain a mixed solution; S4, adding a reducing agent into the mixed solution to react, and obtaining the target catalyst.
  3. 3. The preparation method of the amino-functionalized palladium-silver alloy catalyst regulated and controlled by citric acid coordination according to claim 2 is characterized in that in the step S1, the high-temperature calcination temperature is 700-900 ℃, the calcination time is 2-4 hours, the mass ratio of the carbon material to the nitrogen source is 1-2 g:5-40 g, the carbon material is any one or more of XC-72R carbon black, commercial mesoporous carbon, carbon nano tubes, C 3 N 4 or graphene oxide, and the nitrogen source is any one or more of urea, melamine or dicyandiamide.
  4. 4. The preparation method of the amino-functionalized palladium-silver alloy catalyst with coordination control of citric acid is characterized in that in the step S2, the molar ratio of the palladium precursor to the silver precursor is 1 (0.5-2), the molar ratio of the total molar amount of metal palladium and metal silver to citric acid is 1 (1-4), the palladium precursor is any one or a combination of more than two of Na 2 PdCl 4 、Pd(NO 3 ) 2 、K 2 PdCl 4 、PdCl 2 or Pd (OAc) 2 , and the silver precursor is any one or a combination of more than two of AgNO 3 、Ag 2 SO 4 or Ag (OAc).
  5. 5. The preparation method of the amino-functionalized palladium-silver alloy catalyst regulated and controlled by citric acid coordination according to claim 2 is characterized in that in the step S3, 3-aminopropyl triethoxysilane is further added in the process of dispersing a nitrogen-doped carbon carrier in a solvent for surface modification, so that the 3-aminopropyl triethoxysilane is uniformly grafted on the surface of the nitrogen-doped carbon carrier to obtain an amino-functionalized carrier suspension, and the dosage ratio of the nitrogen-doped carbon carrier to the 3-aminopropyl triethoxysilane is 0.1~0.5 g:0.1~1.0 mL.
  6. 6. The preparation method of the amino-functionalized palladium-silver alloy catalyst regulated and controlled by citric acid coordination according to claim 2, wherein in the step S4, the reducing agent is NaBH 4 , the reducing agent is added in a mode of reducing agent aqueous solution, the concentration is 0.5-2.0 mol/L, the reaction is carried out at room temperature, and the stirring rotation speed is 400-800 rpm.
  7. 7. Use of an amino-functionalized palladium-silver alloy catalyst coordinated and controlled by citric acid according to any one of claims 1-6 for hydrogen production by dehydrogenation of formic acid.
  8. 8. The method of using the amino-functionalized palladium-silver alloy catalyst coordinated and controlled by citric acid in hydrogen production by formic acid according to claim 7, comprising the steps of placing the catalyst and a mixed aqueous solution containing formic acid and formate in a reactor, stirring and carrying out dehydrogenation reaction.
  9. 9. The use according to claim 8, wherein the concentration of formic acid in the aqueous mixture of formic acid and formate is 0.5-3 mol/L and the molar ratio of formic acid to formate is 1 (1-4).
  10. 10. The use according to claim 8, wherein the dehydrogenation reaction is carried out at a temperature of 25-80 ℃ and the stirring speed is 100-350 rpm.

Description

Amino-functionalized palladium-silver alloy catalyst regulated and controlled by citric acid coordination, and preparation method and application thereof Technical Field The invention relates to the technical field of hydrogen energy and nano catalytic materials, in particular to an amino-functionalized palladium-silver alloy catalyst with coordination regulation and control of citric acid, and a preparation method and application thereof. Background The hydrogen energy is used as a key carrier of a clean energy system, and the large-scale application of the hydrogen energy needs to solve the problem of storage and transportation. Formic acid (HCOOH) is regarded as an ideal Liquid Organic Hydrogen Carrier (LOHCs) because of its high hydrogen storage capacity, wide sources and mild dehydrogenation conditions. At present, the development of efficient and stable heterogeneous catalysts is a key to the practical trend of the technology. However, the existing palladium-on-carbon catalysts still face multiple challenges in practical applications: on one hand, the active components are easy to agglomerate, and the metal nano particles with high surface energy are easy to migrate and agglomerate, so that the sub-nano level dispersion is difficult to maintain, and the atom utilization rate is reduced; On the other hand, the existing catalyst system also faces the difficult problem of 'interface mass transfer failure', which is usually ignored but extremely destructive, under the working condition of pursuing high reaction rate, and particularly, the formic acid dehydrogenation process is accompanied by rapid release of gas, so that serious interface bubbling phenomenon is easy to induce. The research shows that the rigid strong hydrogen bond network constructed by a large amount of formate ions and water molecules in the reaction medium can obviously enhance the structural strength of the gas-liquid interface film, so that bubbles generated by the reaction are difficult to spontaneously break, a compact-structure catalyst-bubble composite foam layer (Pickering-like foam) is formed by stacking on the surface of the catalyst, the stable foam layer can not only prevent hydrogen from escaping, but also cause serious solid-liquid phase physical isolation, namely, catalyst particles are easily wrapped and lifted by the rigid bubble film, so that the catalyst breaks away from a liquid phase reaction substrate to fail, and the deactivation of the catalyst is further accelerated by the accompanying local microenvironment deterioration (such as pH value rapid change and formate poisoning). The modification technology for the carbon-supported palladium-based catalyst focuses on reducing the metal particle size or simply modifying the carrier, and the difficult problem of interface mass transfer failure is difficult to solve. In addition, the rigid structure maintained by the microcosmic rigid strong hydrogen bond network cannot be broken down from the source by simple physical stirring. Therefore, development of a novel catalyst capable of realizing metal sub-nano-scale dispersion and interface hydrogen bond network active regulation and control simultaneously is needed to eliminate a gas film forming basis on a micro-level and ensure solid-liquid two-phase efficient contact on a macro-level, so that the bottleneck of hydrogen production efficiency and stability of formic acid is broken through. Disclosure of Invention The invention aims to provide an amino-functionalized palladium-silver alloy catalyst regulated and controlled by citric acid coordination, and a preparation method and application thereof, and aims to solve the technical problems that metal particles are easy to agglomerate, the atom utilization rate is low, bubbles are accumulated due to strong hydrogen bond action at an interface, the catalyst is wrapped and floated, solid-liquid physical isolation is generated, gas production is blocked and the like in the existing carbon-supported palladium-based catalyst in a formic acid dehydrogenation reaction. In order to achieve the above purpose, the present invention adopts the following technical scheme: The first aspect of the invention provides an amino-functionalized palladium-silver alloy catalyst regulated and controlled by citric acid coordination, which comprises a nitrogen-doped carbon carrier and citric acid-modified palladium-silver alloy nano particles anchored on the surface of the nitrogen-doped carbon carrier, wherein the catalyst comprises the nitrogen-doped carbon carrier and the citric acid-modified palladium-silver alloy nano particles anchored on the surface of the nitrogen-doped carbon carrier, and the catalyst is prepared by a citric acid-assisted coordination-limited-area in-situ reduction strategy and comprises the steps of forming a metal palladium-silver-citric acid coordination complex from a palladium precursor, a silver precursor and citric acid in a liquid phase, and then reducing the me