GB1104843A - Process for producing hydrogen - Google Patents

Abstract

A porous polytetrafluoroethylene diffusion membrane is made by mixing finely divided polytetrafluoroethylene with ammonium oxalate or ammonium carbonate, pressing into the desired shape and heating up to about 190 DEG FALSO:H2 is prepared by passing a liquid or vaporized mixture of hydrocarbon and water into contact with a catalyst of a Ni content of 10 to 75 weight per cent at a temperature of 110 DEG to 750 DEG F. and at a rate sufficient to convert 5 to 85% of the hydrocarbon per pass and recovering H2 from a contiguous gas collection zone maintained free of catalyst. When the feed is a vaporized mixture of hydrocarbon and water, the reactants can contact the catalyst at a pressure of 5 to 100 p.s.i.a., preferably at a temperature of 250 DEG to 750 DEG F. When the feed is a liquid emulsion the temperature may be 110 DEG to 400 DEG F. and the pressure may be above atmosphere. Saturated or unsaturated straight chain paraffinic hydrocarbons having 1 to 20 carbon atoms can be used. The preferred water to hydrocarbon ratio is 1:3 to 6:1. The catalyst may be nickel-alumina, e.g. Ni: Al with an atomic ratio of up to 4.0 or nickel-silica, and these may be promoted by 0.5 to 12 weight per cent of the oxides or carbonates, or mixtures of these, or nitrates of the elements La, Ba, Sr, Ce, Cs, K, Fe, Y, and Cu. The use of Ni-ZnCrO4-Al2O3-Ba as catalyst is mentioned. The catalyst may be granulated, e.g. 1 to 5 mm. particles, or pelletized or extruded. The H2 may be recovered from the reaction zone by using diffusion membranes, e.g. of Pd, Pd/Ag or porous polytetrafluoroethylene. The catalyst bed may be contained inside a diffusion membrane, or diffusion membranes can be alternate in series with a plurality of reaction zones. A plurality of reaction zones is preferably used together with a low, e.g. 5-50%, conversion of the hydrocarbon so that the gas produced contains a high proportion of H2, e.g. a less than 25% conversion gives a product consisting essentially of CO2 + H2. The unconverted feed may be recycled from the end reaction zone to the first via a heat exchanger and water separator. The product gases, e.g. CO2, H2 and some CH4, can be separated by liquefaction. CH4 may be recycled.ALSO:H2 is prepared by passing a liquid or vaporized mixture of hydrocarbon and water into contact with a catalyst of a Ni content of 10 to 75 weight per cent at a temperature of 110 DEG to 750 DEG F. and at a rate sufficient to convert 5 to 85% of the hydrocarbon per pass and recovering H2 from a contiguous gas collection zone maintained free of catalyst. When the feed i a vaporized mixture of hydrocarbon and water, the reactants can contact the catalyst at a pressure of 5 to 100 p.s.i.a., preferably at a temperature of 250 DEG to 750 DEG F. When the feed is a liquid emulsion the temperature may be 110 DEG to 400 DEG F. and the pressure may be above atmosphere. Saturated or unsaturated straight chain paraffinic hydrocarbons having 1 to 20 carbon atoms can be used. The preferred water to hydrocarbon ratio is 1.3 to 6 : 1. The catalyst may be nickel-alumina, e.g. Ni : Al with an atomic ratio of up to 40 or nickel-silica and these may be promoted by 0.5 to 12 weight per cent of the oxides or carbonates, or mixtures of these, or nitrates of the elements La, Ba, Sr, Ce, Cs, K, Fe, Y, and Cu. The use of Ni-ZnCrO4-Al2O3-Ba as catalyst is mentioned. The catalyst may be granulated, e.g. 1 to 5 mm. particles, or pelletized or extruded. The H2 may be recovered from the reaction zone by using diffusion membranes, e.g. of Pd, Pd/Ag or porous polytetrafluoroethylene. The catalyst bed may be contained inside a diffusion membrane, or diffusion membranes can be alternate in series with a plurality of reaction zones. A plurality of reaction zones is preferably used together with a low, e.g. 5-50%, conversion of the hydrocarbon so that the gas produced contains a high proportion of H2, e.g. a less than 25% conversion gives a product consisting essentially of CO2+H2. The unconverted feed may be recycled from the end reaction zone to the first via a heat exchanger and water separator. The product gases, e.g. CO2, H2 and some CH4, can be separated by liquefaction. CH4 may be recycled.