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Method for preparing nano-catalyst copper chromite and copper ferrite

A nano-catalyst, copper salt technology, applied in chemical instruments and methods, physical/chemical process catalysts, metal/metal oxide/metal hydroxide catalysts, etc., can solve the problem of uneven powder particles, high catalytic activity, hard Less agglomeration and other problems, to achieve the effect of long service life, high catalytic activity, and less hard agglomeration

Inactive Publication Date: 2009-02-18
TSINGHUA UNIV
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, the preparation method limits its application
Co-precipitation or solid-phase methods are mostly used in traditional preparation, and these methods have some disadvantages: uneven powder particles, severe hard agglomeration, high sintering temperature, low activity, etc.
[0004] Aiming at the disadvantages of hard agglomeration, inhomogeneous particles, and low activity in the preparation of copper chromite and copper ferrite catalysts by traditional methods, the present invention adopts sol-gel and vacuum freeze-drying methods to prepare a catalyst with high purity, small particle size, and dispersed CuFe with spinel structure with good performance, less hard agglomeration and high catalytic activity 2 o 4 and CuCr 2 o 4 catalyst

Method used

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  • Method for preparing nano-catalyst copper chromite and copper ferrite
  • Method for preparing nano-catalyst copper chromite and copper ferrite
  • Method for preparing nano-catalyst copper chromite and copper ferrite

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preparation example Construction

[0033] (1) Preparation of sol:

[0034] a. Prepare a mixed solution of soluble copper salt and soluble chromium salt with a molar ratio of 1:2, wherein the concentration of copper salt is 0.1-0.5mol / L; add a surfactant with a mass percentage of 0.1%-5%, and stir evenly; Wherein soluble copper salt and soluble chromium salt adopt nitrate, sulfate or hydrochloride. The surfactant adopts polyethylene glycol, sodium tripolyphosphate, sodium hexametaphosphate or cetyltrimethylammonium bromide;

[0035] b. Add the precipitant aqueous solution to the mixed solution at a rate of 20-180ml / h until the pH of the system is 6.8-9.5, leave it for aging, centrifuge or filter and wash to obtain a precipitate; the precipitant used is ammonia water, ammonium carbonate, ammonium bicarbonate, sodium carbonate, sodium bicarbonate, or sodium hydroxide;

[0036] c. Add deionized water with a mass percentage of 8% to 40% to the obtained precipitate, and melt the gel in a constant temperature water ...

Embodiment 1

[0055] Prepare a mixed solution with a copper salt concentration of 0.1 mol / L according to the molar ratio of copper nitrate and chromium nitrate as 1:2, add 0.1% polyethylene glycol surfactant by mass percentage, and stir evenly. Ammonium bicarbonate aqueous solution was added to the mixed solution at a rate of 20ml / h until the pH of the system was 6.8, left to age for 8 hours, and washed by centrifugation. The obtained precipitate was added with 8% deionized water by mass, stirred evenly, and melted in a constant temperature water bath at 70° C. for 2 hours to obtain a sol. The sol is freeze-dried at -45° C. and a vacuum degree of 1 Pa by a vacuum freeze-drying method to obtain a precursor xerogel. Finally, the precursor xerogel was placed in a tube furnace, heated from room temperature to 350 °C at a rate of 3 °C / min, and kept for 1 h to obtain CuCr 2 o 4 Nano catalyst powder.

[0056] Depend on figure 1 From the TEM picture, we can see that the particle size of the cat...

Embodiment 2

[0058] Prepare a mixed solution with a copper salt concentration of 0.5 mol / L according to the molar ratio of copper sulfate to chromium sulfate of 1:2, add 0.1% by mass of sodium tripolyphosphate surfactant, and stir evenly. Add ammonia solution to the mixed solution at a rate of 180ml / h until the pH of the system is 9.5, let it stand for aging for 24 hours, and filter and wash. The obtained precipitate was added with 40% deionized water and stirred evenly, and the gel was melted in a constant temperature water bath at 95° C. for 8 hours to obtain a sol. The sol is freeze-dried at -80° C. under a vacuum degree of 30 Pa by a vacuum freeze-drying method to obtain a precursor xerogel. Finally, place the precursor xerogel in a muffle furnace, heat it from room temperature to 850°C at a rate of 15°C / min, and keep it for 8 hours to obtain CuCr 2 o 4 Nano catalyst powder.

[0059] Depend on figure 2 From the XRD pattern, we can see that the peak shape of the catalyst prepared ...

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Abstract

The invention discloses a method for preparing a nano-size catalyst of copper chromite and copper ferrite, and belongs to the technical field of nano-size catalyst preparation. The method of the invention comprises a sol-gel process and a vacuum freezing drying (VFD) process. Firstly, a mixed solution is prepared from a soluble copper salt and a soluble chromium salt or iron salt, added with a surface active agent, and mixed uniformly, and then the system is added with a precipitating agent to carry out precipitation reaction under the condition that the pH value is between 6.8 and 9.5, then is kept stand, aged, washed and melted in a water bath for 2 to 8 hours at a temperature of between 70 and 95 DEG C, thus sol is obtained; then the sol is subjected to freezing drying in a vacuum freezing dryer to obtain dried gel which is a precursor of the catalyst; finally, the dried gel is roasted to obtain the nano-size catalyst of copper chromite (CuCr2O4) or copper ferrite (CuFe2O4). The catalyst prepared by the method has the advantages of high purity, small grain diameter, good dispersivity, high catalytic activity, and the like.

Description

technical field [0001] The invention relates to a method for preparing CuCr 2 o 4 and CuFe 2 o 4 The nanometer catalyst method belongs to the field of catalyst preparation. The preparation method involves sol-gel and vacuum freeze-drying. Background technique [0002] Nano CuCr 2 o 4 and CuFe 2 o 4 It is an important class of catalysts and exhibits good catalytic activity in many catalytic reactions. For example: catalytic hydrogenation of carbon monoxide (Yureva TM, et al. Kine Catal,), automobile exhaust purification (Morgan W.J.Cat), selective catalytic hydrogenation of edible oils and fats (Jakansson L E.J.Amer.oil Chem.Soc). However, the preparation method limits its application. Co-precipitation method or solid-phase method is mostly used in traditional preparation. These methods have some disadvantages: uneven powder particles, severe hard agglomeration, high sintering temperature, and low activity. [0003] Sol-gel and vacuum freeze-drying are new technolo...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B01J23/86B01J23/745
Inventor 苏涛张平王来军陈崧哲王志超姚桃英徐景明
Owner TSINGHUA UNIV
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