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5. Amorphous alumina B698D-24 and the acid-treated natural clay Grade F-1 were received as generous gifts from Engelhard De Meern B.V., The Netherlands. The catalysts used, were pressed (3 tons) and sieved to the desired particle size (150–425 μm). Catalysts were used after a pre-treatment: an amount of catalyst was placed on a quartz porous filter in the middle of a quartz FVT-tube. Using the catalytic FVT set-up, the catalyst was equilibrated at a temperature of 400°C and a vacuum of 0.05 mbar during 15–20 min to remove physisorbed water.