Silica membrane reactors for hydrogen processing S. E. Battersby 1 , D. Miller 2 , M. Zed 3 , J. Patch 4 , V. Rudolph 1 , M. C. Duke 1 and J. C. Diniz da Costa* 1 This paper presents an analysis of membrane reactor operation and design for enhanced hydrogen production. Silica derived membranes were used for gas permeation studies and a membrane reactor for the water gas shift reaction. A model of the equilibrium reaction is developed and analysed with respect to operational factors such as temperature and pressure analysed in consideration for production of a 99% pure H 2 stream. These factors influence the optimisation of the reaction and permeation rate as well as the equilibrium conversion. It was found that using H 2 permeation membranes, the H 2 equilibrium could be shifted towards the products. In turn, this provided better conversion at higher temperatures. The cost of H 2 production using membrane reactors is dependent upon several engineering process parameters such as reaction rates, permeation, selectivities, temperature and pressure. Silica membranes assembled in membrane reactors out performed conventional reactor systems. Silica membranes were synthesised showing permeations of 5610 28 mol m 22 s 21 Pa 21 and H 2 /CO selectivities .10. The silica membrane capital cost per kg H 2 produced ranged from US$0 . 25 to 3 . 00 for 10 to 80%H 2 separation respectively. Keywords: H 2 separation, CO conversion, Membrane cost analysis Introduction Hydrogen is the smallest, lightest and most abundant element on Earth. While present in large amounts bound in the forms of water and hydrocarbons, hydrogen is not available in its desirable gas state. 1 Today hydrogen gas is used in many industries as a chemical raw material such as for the production of ammonia and rubbers, the dehydrogenation of fats and oils and in its liquid form as rocket propellant. 2 However, it is in the fuel and energy industry that hydrogen has generated the most current interest. The steady rise in the price of oil and gas on the international market, interest has directed the search for new energy processes. 3 Hydrogen has some unique properties that make it an ideal energy carrier: it has the ability to be produced and converted into electricity at already high and ever increasing efficiencies, it can be produced from abundant resources both non-renewable and renewable and it has the ability to be efficiently stored. 1 As other renewable resources such as solar, wind and water are limited in their potential energy supply for the immediate future, the use of biomass or fossil fuels remain the primary source of H 2 production. 4 A variety of methods are available to produce H 2 from its different sources. These include electrolysis, steam reforming, gasification, dehydrogenation and selective oxidation. 3,5 Gasification is the most widely used process, involving the reaction of a hydrocarbon with water to produce H 2 , CO and CO 2 in the following reactions 3 C n H 2nz2 znH 2 O?nCOz(2nz1)H 2 (1) COzH 2 O?CO 2 zH 2 (2) By utilising the H 2 in both the hydrocarbon and the water molecule, gasification provides the highest pro- duction per carbon molecule. As the H 2 sourced from the water molecule represents an increase in the overall hydrogen balance of the system, any increase in the second reaction represents an important improvement in the systems efficiency. Consequently this process is the preferred choice in hydrogen production for fossil fuels. An alternative to steam reforming is the dehydro- genation of hydrocarbons. Within refineries traditional sources of H 2 are byproduct of dehydrogenation reac- tions used to improve the octane rating of fuel. 6 In addi- tion, hydrogenated species may be used as ideal chemical hydrogen carriers. 7,8 Dehydrogenation reactions there- fore represent a process step in the efficient production and storage of hydrogen energy for future use. 1 ARC Centre for Functional Nanomaterials, Division of Chemical Engineering, School of Engineering, The University of Queensland, Brisbane, QLD 4072, Australia 2 Caltex Refineries, Lytton Refinery, South St, Lytton, QLD 4178, Australia 3 Santos Ltd, Santos House, 91 King William St, Adelaide, SA 5000, Australia 4 Halliburton, 555 Coronation Drive, Toowong, QLD 4066, Australia *Corresponding author, email joedac@cheque.uq.edu.au ß 2007 Institute of Materials, Minerals and Mining Published by Maney on behalf of the Institute Received 15 August 2005; accepted 9 February 2006 DOI 10.1179/174367607X152399 Advances in Applied Ceramics 2007 VOL 106 NO 1–2 29