Raney nickel

Raney nickel is a solid catalyst composed of fine grains of a nickel-aluminum alloy, used in many industrial processes. It was developed in the 1920s by American engineer Murray Raney as an alternative to powdered nickel for the hydrogenation of vegetable oils in industrial processes. Since its introduction, Raney nickel has found extensive use in the chemical industry due to its effectiveness in catalyzing a variety of chemical reactions, including hydrogenation, isomerization, and desulfurization.

Composition and Properties

Raney nickel is typically prepared by treating an alloy of nickel and aluminum with concentrated sodium hydroxide (NaOH). This process, known as "leaching," removes most of the aluminum from the alloy, leaving behind a highly porous structure of nickel. The resulting material has a large surface area, which is key to its effectiveness as a catalyst. The specific composition of Raney nickel can vary, but it generally contains around 85% nickel by weight, with the remainder consisting of small amounts of aluminum and other trace metals.

Applications

Raney nickel is widely used in the chemical industry for a variety of applications. Its primary use is in the hydrogenation of organic compounds, where it serves to add hydrogen atoms to molecules. This is critical in the production of saturated fats from unsaturated fats, a process important in the food industry, as well as in the manufacture of chemicals where unsaturated compounds need to be reduced.

In addition to hydrogenation, Raney nickel is also used in:

• The isomerization of alkenes and alkynes
• The reductive amination of aldehydes and ketones
• The desulfurization of organic compounds, which is particularly important in the processing of fossil fuels

Safety and Handling

Raney nickel, while useful, must be handled with care due to its pyrophoric nature, especially when dry. It can ignite spontaneously in air, necessitating strict safety protocols during storage and use. Typically, Raney nickel is stored under an inert atmosphere or in a solvent that excludes air. Safety data sheets (SDS) provide detailed handling instructions to prevent accidental ignition.

Environmental and Health Concerns

The use of Raney nickel in industrial processes raises several environmental and health concerns. Nickel compounds are known to be toxic and can cause allergic reactions in some individuals. The disposal of spent Raney nickel must be managed carefully to avoid environmental contamination. Recycling and proper waste management practices are essential to mitigate the impact of Raney nickel on the environment and human health.

See Also

• Catalysis
• Hydrogenation
• Nickel
• Chemical industry

References

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  Raney nickel container

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  Raney nickel phase diagram

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  Raney nickel

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  Close-up of Raney nickel

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  Hydrogenation Raney nickel

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  Desulfurization of thioacetal using Raney Ni

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  Ra-Ni Thiophene Scheme

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  Hazard F