Differences between Urushibara nickel and Raney nickel

Question

The Wikipedia article about Urushibara nickel catalyst is rather short and vague. What is the mechanism for its preparation, and furthermore, in what sense does it differ from Raney nickel (i.e. when should you prefer the one over the other)?

Answer 1

You can find information about the preparation of Urushibara nickel (U-Ni) in the original paper by Urushibara^[1].

Regarding the differences with Raney nickel (R-Ni), surface characterization by means of XPS^[2] had shown that R-Ni catalysts contain metallic aluminium in the activated phase as well as oxidized aluminium, while U-Ni catalysts contain metallic zinc in the activated phase in addition to oxidized zinc. Also, U-Ni catalysts can be described as supported nickel catalysts, while R-Ni catalysts are shown to have the well known skeletal structure.

The activity of U-Ni catalysts is very similar to R-Ni catalysts, both in nature of the reaction catalysed and in the rate of catalysis. One of the advantage of U-Ni is their simplicity of preparation, while R-Ni catalytic synthesis requires a long time. Despite this, U-Ni catalysts are also not very sensitive to impurities, so they can be prepared from commercial chemicals of ordinary grade, and they can be stored for a long time without decreasing the activity. Another advantage is the safer handling, since U-Ni catalysts are not inflammable upon contact with air, in contrast to Raney catalysts which are pyrophoric. This allows the catalyst to be recovered and regenerated. However, it should be noted that U-Ni catalyst durability is not satisfactory during the reaction, but this is also the case of R-Ni catalysts, so there is not really a big difference when it comes to practical use, maybe slightly supporting the use of U-Ni vs R-Ni as the former is less expensive and easy to produce and regenerate. The only real disadvantage of U-Ni catalysts is that for some particular reductions, they show less activity than R-Ni catalysts, favouring one reaction over another, for example U-Ni catalysts particularly favours the partial hydrogenation of acetylenic compounds to ethylenes^[3].

     _{¹ Urushibara, Yoshiyuki. "A New Method of Catalytic Hydrogenation". Bulletin of the Chemical Society of Japan 25 (4): 280–280
     ² Y. Okamoto, Y. Nitta, T. Imanaka and S. Teranishi, J. Chem. Soc., Faraday Trans. 1, 1979, 75, 2027
     ³ Kazuo Hata, “New Hydrogenation Catalysts: Urushibara Catalysts” (1971), pp 235-237}