Heavy Water Technologies Branch, Chalk River Laboratories, Atomic Energy of Canada Limited, Chalk River, ON KOJ lJ0, Canada novel process developed by Atomic Energy of Canada Limited for the production of heavy water uses a proprietary catalyst for the A deuterium-hydrogen isotope exchange between the natural water and industrially produced hydrogen which contains a small amount of deuterium. The industrially reformed hydrogen contains trace quantities (0.2 to 10 ppm) of carbon monoxide, which poisons the isotope exchange catalyst and, therefore, must be removed to a level less than 1 ppb. Various methods have been reported in the literature for the removal of CO from hydrogen. A methanation unit operating at 300°C followed by a Ag-Pd membrane purifier has been suggested for removal of CO and CO, (Hsiung et al., 1999) to obtain carbon-free hydrogen for the electronics industry. A selective methanation of CO on Ru/AI,O, catalyst in the temperature range of 100°C to 200°C has also been suggested (Terasawa, 1991). However, with substantial amounts of CO (>I 00 ppm) in the hydrogen stream, CO removal by methanation could produce uneconomic losses of deuterium in the form of deuterated methane. A cyclic temperature-swing-adsorption system using Pt/Al,O, (Sadhankar et al., 1999) was found to be a viable approach. This study examines the adsorption of CO on Pt/AI,O, catalyst pellets and the regeneration of the exhausted catalyst. The adsorption column dynamics have been modelled considering both gas-film diffusion and intraparticle diffusion processes. Experimental EquipmentThe experimental equipment consisted of a stainless-steel tubular reactor with 33.4-mm internal diameter. The reactor was filled with 44 g of cylindrical pellets (3 mm x 3 mm) of a commercial catalyst containing 0.5 wt% platinum on y-AI,O, support. The catalyst was egg-shell type in which the platinum is deposited in a thin outer layer. The reactor and the inlet gas line were equipped with electrical heat tracing. The reactor temperature was controlled by a Yokogawa temperature controller and monitored by two resistance temperature detectors. The reactor temperature was always maintained a t 40°C during adsorption experiments and was maintained between 200°C and 270°C during regeneration depending on the method of regeneration. The experimental facility was designed for a pressure of 3500 kPa. The feed to the reactor consisted of a pure hydrogen stream and a mixture of 2% CO in hydrogen, both of which were fed through individual Matheson mass flow controllers. The feed was passed through a mixer before entering the reactor. The superficial velocities through the reactor were in the range of 0.09 to 0.35 rn.s-' (STP). The inlet and outlet gases to and from the reactor were "Author to whom correspondence may be addressed. E-mail address: sadhankaMi aecl.caA method for the removal of trace quantities (0.2 to 10 ppm) of carbon monoxide in commercial hydrogen using a temperature-swing-adsorption system with 0.5 wt% Pt/AI,O, adsorbent has been investigated...

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Commercial activated alumina and titanium dioxide catalysts were treated with Teflon to reduce the negative effects of water vapour on the oxidation of hydrogen sulphide by sulphur dioxide (Claus Reaction) near the sulphur dew point. The tests were conducted at 200°C and 130°C (108 kPa), with and without 30% water vapour in the feed gas. An alumina/Teflon composite catalyst was found to be superior to both untreated commercial catalysts at 130°C. This improvement was probably due to an increase in macroporosity rather than to a wetproofing effect. At 200°C, the performance of the composite was similar to that of the untreated titanium dioxide which in turn was superior to the untreated activated alumina.

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