Palladium-based membranes steam reforming

Marigliano, G., Barbieri, G. and Drioli, E. (2001) Effect of energy transport in a palladium based membrane reactor for methane steam reforming process. Catalysis Today, 67 (1-3), 85-99. 

A concept for a methanol (or ethanol) fuel processor based upon steam reforming and membrane separation was presented by Gepert et td. [400]. As shown in Figure 5.33, the alcohol/water mixture was evaporated and converted by steam reforming in a fixed-bed catalyst, into which palladium capillary membranes were inserted. The retenate then entered the combustion zone, which was positioned concentrically around the reformer bed at the reactor wall. Air was fed into the combustion zone and residual hydrogen, carbon monoxide and unconverted methanol combusted therein. The sealing of the membranes at the reactor top was an issue solved by air-cooled elastomers. 

Barbieri, G, Violante, V. DiMaio, F. Criscuoli, A. Drioli, E. Methane Steam reforming Analysis in a Palladium-Based Catalytic Membrane Reactor Ind. Eng. Chem. Res. 36 (1997) 3369-3374. 

Barbieri G, Violante V, Di Maio FP, Criscuoh A, and Drioh E, Methane steam reforming analysis in a palladium-based catalytic membrane reactor, Ind. Eng. Chem. Res. 1997 36 3369. 

Palladium or its alloys are the most practical membrane materials, due to their high hydrogen permeability and stability at high temperatures. The membrane reformer is composed of a steam reformer equipped with palladium-based alloy modules in its catalyst bed, and can perform steam reforming reaction and hydrogen separation processes concurrently with no help from shift converter and PSA, as shown in Fig. 12.1. 

Figure 8.16 shows a methanol/water vaporiser, followed by a catalytic steam reformer operating at about 250°C, in which the catalyst is a thin film of Cu/ZnO coated onto the silica reactor, and finally a membrane shift reactor consisting of a palladium diffusion layer mounted on top of a perforated copper-based shift catalyst. Built onto the chip are integrated resistive heaters for getting the reformer and vaporiser up to temperature, together with micro-scale sensors and control electronics. Whilst such systems are a long... 

In recent years, new concepts to produce hydrogen by methane SR have been proposed to improve the performance in terms of capital costs reducing with respect to the conventional process. In particular, different forms of in situ hydrogen separation, coupled to reaction system, have been studied to improve reactant conversion and/or product selectivity by shifting of thermodynamic positions of reversible reactions towards a more favourable equilibrium of the overall reaction under conventional conditions, even at lower temperatures. Several membrane reactors have been investigated for methane SR in particular based on thin palladium membranes [14]. More recently, the sorption-enhanced steam methane reforming (Se-SMR) has been proposed as innovative method able to separate CO2 in situ by addition of selective sorbents and simultaneously enhance the reforming reaction [15]. 

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