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Supported noble metal catalyst with coating structure and its preparation method and application in liquid-phase catalytic reduction of cr(ⅵ)

A technology of precious metal catalysts and coating structures, applied in catalyst protection, chemical instruments and methods, physical/chemical process catalysts, etc., can solve the problems that impurity ions cannot be directly reused, the expected effect cannot be achieved, and the resin is easily polluted , to achieve good economic and environmental benefits, good catalytic performance, and a wide range of applications

Active Publication Date: 2020-04-28
NANJING UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The commonly used adsorbent for treating Cr(VI) by adsorption method is activated carbon. This method has been developed earlier, and there have been reports of practical application. However, after the adsorbent reaches saturation, it needs to be regenerated and replaced, and the cost is high.
The chemical precipitation method refers to the use of a reducing agent to reduce Cr(Ⅵ) to Cr(Ⅲ) under acidic conditions, and then add lime or sodium hydroxide to form a precipitate and remove it. However, the solubility of the precipitate generated by this method is small and it is not easy to Anti-melting, easy to form secondary pollution
The ion exchange method to treat Cr(VI) in water mainly uses the exchange ions in the ion exchange resin to exchange with Cr(VI) ions, and further elutes to remove Cr(VI). The disadvantage is that the resin used in this method is susceptible to Ineffective due to pollution, and has strict requirements on operation and management. If the management is improper during the treatment process, the expected effect will not be achieved, and the impurity ions such as sodium and iron in the regeneration waste liquid cannot be directly reused, and discharge into the environment will cause secondary pollution.

Method used

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  • Supported noble metal catalyst with coating structure and its preparation method and application in liquid-phase catalytic reduction of cr(ⅵ)
  • Supported noble metal catalyst with coating structure and its preparation method and application in liquid-phase catalytic reduction of cr(ⅵ)
  • Supported noble metal catalyst with coating structure and its preparation method and application in liquid-phase catalytic reduction of cr(ⅵ)

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0044] A supported Pd metal catalyst with a coating structure and preparation thereof. The catalyst includes Pd-supported multi-walled carbon nanotubes Pd / MWCNT, the Pd loading is 1% (mass percentage), and the surface is coated with nitrogen doping Carbon coating.

[0045] The catalyst with coated structure was prepared according to the following steps:

[0046] (1) First, the multi-walled carbon nanotubes (MWCNT) and the Pd salt solution are mixed and stirred, and supported by the dipping method to obtain supported Pd / MWCNT, wherein the Pd loading amount is 1% wt. The transmission electron microscope image of Pd / MWCNT is as follows figure 1 As shown in (A), it can be seen that the precious metal particles are uniformly dispersed on the surface of the multi-walled carbon nanotubes. According to statistics, the average particle size of the precious metal is about 3.73 nm.

[0047] (2) Then, disperse the Pd / MWCNT into a Tris (Tris(Trishydroxymethylaminomethane)) buffer solution with a...

Embodiment 2

[0055] In addition, the above-prepared Pd / MWCNT and Pd / MWCNT@CN series catalysts are used to carry out liquid phase catalytic reduction of Cr(Ⅵ) in water in a cyclic reaction (specifically as Image 6 Shown). The catalyst concentration is 0.325g / L, the initial concentration of Cr(Ⅵ) is 0.5mM, the pH of the reaction system is 2.0, the flow rate of hydrogen is 200ml / min, the reaction is under normal temperature and pressure for 2h, and the cycle reaction is four times. The deactivation rate is all within Below 5%, and with the increase of the coating amount, the stability is also significantly improved. The activity of the source material after four cycles is significantly reduced, and the initial activity inactivation rate is 92.5%. The comparison shows that the stability of the catalyst with the coated structure is obviously improved.

Embodiment 3

[0057] The preparation method of the supported Pd metal catalyst with the coating structure is the same as that of Example 1, and the catalyst prepared in this example is used for the liquid phase catalytic reduction reaction of Cr(VI). The catalyst adopts Pd / MWCNT@2CN, and its concentration is 0.125g / L, 0.225g / L, 0.325g / L, 0.375g / L, the initial concentration of Cr(Ⅵ) is 0.5mM, the reaction pH is 2.0, and the hydrogen flow rate 200ml / min, react for 2h at room temperature and pressure, such as Figure 7 Shown are the initial activity curves of Pd / MWCNT@2CN with different catalyst dosages. The initial activity of the catalyst is basically maintained at 8mM / (gcat.h), indicating that there is no mass transfer resistance in the reaction system.

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Abstract

The invention belongs to the field of liquid catalysis and industrial wastewater treatment, and relates to a supported noble metal catalyst with a coating structure, a preparation method thereof and application of the supported noble metal catalyst in Cr(VI) liquid catalytic reduction. The catalyst comprises a supported noble metal multi-wall carbon nano-tube, and the surface of the supported noble metal multi-wall carbon nano-tube is coated with a nitrogen doped carbon coating layer; the noble metal is Pd or Pt and is 0.5-5 percent of total mass of the supported noble metal multi-wall carbon nano-tube. The invention further provides a preparation method of the catalyst and application of the catalyst in Cr(VI) liquid catalytic reduction. The catalyst containing a nitrogen carbon coating layer shows remarkable stability in a liquid catalytic hydrogenation reduction reaction, and can be used for effectively prolonging the service life of the catalyst; and the synthesizing method is simple, and is easy to operate; and the synthesized material applied to Cr(VI) liquid catalytic reduction can be used for effectively removing or reducing toxin of Cr(VI).

Description

Technical field [0001] The invention belongs to the field of liquid phase catalysis and industrial wastewater treatment, and specifically relates to a supported noble metal catalyst with a coating structure, a preparation method of the catalyst and the application of the catalyst in the liquid phase catalytic reduction of Cr(VI). Background technique [0002] Chromium is widely present in nature, it exists in different forms in different environments, most of which exist in the form of hexavalent chromium and trivalent chromium. At present, it is widely believed that chromium pollution mainly comes from the discharge of waste water and waste gas from industries such as tanning, electroplating and textile; the chromium in industrial waste water mainly exists in the form of Cr(VI). [0003] Among the various forms of chromium, the toxicity of Cr(Ⅵ) is 100 times greater than that of Cr(Ⅲ), and it is easier to be absorbed by the human body, which is more harmful to the human body; Cr(Ⅵ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): B01J27/24B01J33/00C02F1/70C02F101/22
CPCB01J27/24B01J33/00C02F1/70C02F2101/22
Inventor 郑寿荣李明会许昭怡吴可孙静雅宁欣刘慧武安邦仇昊
Owner NANJING UNIV
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