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Magneto-catalytic effects in the hydrogenation of ethylene reaction Morgan, John Paul

Abstract

The hydrogenation of ethylene reaction was studied over small catalyst beds of powdered nickel, nickel spheres, alumina supported nickel, powdered copper, and platinum wire. The reactor was positioned between the pole faces of an electromagnet, so that a magnetic field of strengths up to 10⁴ gauss could be applied across the catalyst bed. The reaction was studied at conditions of constant flow over the temperature range of 25° C to 550°C. The reaction rate was measured by means of a gas chromatograph, which had the sampling port installed in the system. Two magneto-catalytic effects were studied in this work: (i) the change in catalytic activity of a ferromagnetic catalyst as it is heated through its Curie temperature (internal magneto-catalytic effect); (ii) the change in catalytic activity of either a ferromagnetic or non-ferromagnetic catalyst, due to the presence of an external magnetic field (external magneto-catalytic effect). A clearly observable internal magneto-catalytic effect was found for the runs done on the ferromagnetic catalyst, nickel, which has an approximate Curie temperature of 360°C. In order to confirm this effect, runs were done over the temperature range of 300°C to 500°C on the non-ferromagnetic catalysts, copper and platinum. No change in reaction rate was found near 360°C, as was found using a nickel catalyst. No external magneto-catalytic effect was observed at any temperature. The hydrogenation of ethylene was found to be a rapidly self-poisoning reaction at temperatures above 100°C. Published literature indicates that at moderately high temperatures, desorption of reacting ethylene complexes off the catalyst surface causes the decrease in reaction rate. In this work a significant mole fraction of methane was detected in the reactor effluent gas, at temperatures above 300°C, and an accompanying carbon deposit was observed to form on the catalyst surface. The rapid decrease in catalytic activity at high temperatures was believed to be due to this carbon deposit.

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