Nickel Catalysts

The substance containing nickel and having catalytic function is called nickel catalyst. Nickel is a silver-white metal. Nickel is more reactive chemically but more stable than iron. It is difficult to oxidize in air at room temperature. When heated, nickel can be oxidized to form nickel oxide, which has excellent catalytic activity and is one of the nickel catalysts. Nickel is widely distributed in the earth's crust, so the variety of nickel catalysts is abundant and the price is low.

Figure 1. Nickel catalysts

Applications:

Nickel catalysts are widely used in chemical industry and environmental protection field because of their advantages of high mechanical strength, good catalytic activity, simple preparation and low price.

• Hydrogenation reaction: Nickel catalyst has good hydrogenation activity. Due to its good catalytic activity, high mechanical strength, insensitivity to toxicants, good thermal conductivity and other advantages, nickel catalyst is often used for catalytic methanation of CO_x and hydrogenation of organic compounds. The reaction of CO_x hydrogenation to CH₄ under the action of catalyst is called methanation. Nickel catalyst has the advantages of high methanation activity and good CH₄ selectivity.
• Reforming reaction: Hydrogen is a widely recognized clean energy source. One of the ways to produce hydrogen is to use the catalytic reforming reaction of oxygen-containing hydrocarbon or hydrocarbon. It is increasingly common to use nickel catalyst in catalytic reforming reaction. For example, mesoporous Ni/MgO catalysts prepared by hydrothermal coprecipitation can be used to catalyze steam reforming of phenol to produce hydrogen. CeO₂·9Ni/McM-22 catalyst was prepared by sol-gel method, which can be used for catalytic reforming of CO₂ to prepare hydrogen. Ni/MMT catalyst prepared by dipping method can be used to catalyze glycerol reforming to produce hydrogen.
• Oxidation reaction: Due to the advantages of low energy consumption, small reactor size, high airspeed, high selectivity and high conversion rate, partial oxidation of methane (POM) to prepare syngas is currently the most important way to use methane to prepare chemical products. Nickel catalyst not only has high catalytic activity, but also has strong stability and excellent anti-carbonation ability, so it shows good catalytic effect in partial oxidation of methane. In addition, Ni/SiO₂, Ni/Al₂O₃ and other supported nickel catalysts have better performance in all aspects than non-supported nickel catalysts. In terms of technology, supported nickel catalysts are usually used to catalyze partial oxidation of methane to prepare syngas.
• Hydrocyanation reaction: The catalytic system formed by the nickel catalyst and the phosphorus ligand has a wide application range in the hydrocyanation reaction of the olefin, and can catalyze the hydrocyanation reaction of various olefins. Typically, the nickel cyanide catalyzed hydrocyanation reaction occurs in the organic phase. For example, when benzene is a solvent, Ni(CO)₄/PPh₃ can be used as a catalyst to catalyze hydrocyanation of butadiene to obtain 3-pentenenitrile. When carbonitrile is used as a solvent, Ni[P(O-o-tolyl)₃]₄ can be used as a catalyst to catalyze hydrocyanation of styrene to obtain a main product branched-chain nitrile. The nickel catalyst catalyzes the hydrocyanation reaction with good selectivity and high yield.

Figure 2. Nickel catalyst catalyzed hydrocyanation reaction

• Environmental protection: Coking wastewater is a kind of typical toxic and refractory complex industrial wastewater. The ferrites of Ni series showed strong stability. In addition, nickel oxide has diamagnetism, easy recovery and low toxicity. Therefore, NiO, as an excellent nickel catalyst, can be used in the treatment of coking wastewater. The catalytic activity of NiO is positively correlated with the specific surface area. Nickel oxide prepared by hydrothermal synthesis has high specific surface area and high catalytic activity and is widely used in the treatment of coking wastewater.

References

1. Atzori, Luciano. (2019). "CO and CO₂ co-methanation on Ni/CeO₂-ZrO₂ soft-templated catalysts." Catalysts 9(5), 415.
2. Moura-Nickel. (2019), "Syngas production by dry reforming of methane using lyophilized nickel catalysts." Chemical Engineering Science 205, 74-82.
3. Toshtay, K. (2017), "Comparative hydrogenation of the sunflower oil on platinum and nickel catalysts." Chemical Bulletin of Kazakh National University (3), 4-13.