The use of magnetic techniques in the development of a hydrogenation process

Finely divided Raney Nickel is widely used as a hydrogenation catalyst in the chemical industry and in the refining or hardening of oils and fats. Catalyst removal from process streams is usually carried out by filtration or by centrifugation. Catalyst recycle is difficult owing to the abrasive and pyrophoric nature of the catalyst, general solids handling problems and the propensity of the catalyst to form blockages in linework and in processing equipment. This paper describes the development of a novel design of reactor using magnetic techniques to overcome these problems. An electromagnetic coil is used at the end of a batch to induce sufficient magnetism within the Nickel particles suspended in the process liquor to cause flocculation or agglomeration of the catalyst particles into clusters. These agglomerates settle much faster than the original finely divided material and within minutes most of the catalyst settles out on the base of the vessel. The slight haze of catalyst which remains is removed using an external HGMS unit which is backflushed into the reactor by the following charge. Settled catalyst is easily resuspended by an agitator. Alternative ways of applying the magnetic flocculation technique are described and ways of improving the HGMS unit are discussed.