Pd-alloy membrane reactors

Marigliano, G., Barbieri, G. and Drioli, E. (2003) Equilibrium conversion for a Pd-alloy membrane reactor. Dependence on the temperature and pressure. Chemical Engineering and Processing, 42 (3), 231-236. 

Thermodynamic Equilibrium in Pd-Alloy Membrane Reactor 301 Conclusions 303 References 306... 

Miyamoto, M., Hayakawa, C., Kamata, K. et al. (2011) Influence of the pre-reformer in steam reforming of dodecane using a Pd alloy membrane reactor. International Journal of Hydrogen Energy, 36, 7771-7775. 

Because Pd-alloy membranes operate at high temperatures in the range of WGS reaction and on the lower end of methane reforming reaction, they can be used in a membrane reactor configuration for the simultaneous separation of hydrogen. As discussed earlier,... 

An integrated proof-of-concept (POC) size fluidized-bed methane reformer with embedded palladium membrane modules for simultaneous hydrogen separation is being developed for demonstration (Tamhankar et al., 2007). The membrane modules will use two 6 in. X 11 in. Pd-alloy membrane foils, 25-pm thick, supported on a porous support. The developmental fluidized-bed reactor will house a total of five (5) membrane modules with a total membrane area of about 0.43 m2 and is scheduled for demonstration by September 2007. 

Dense palladium-based membranes. Shown in Table 10.1 are modeling studies of packed-bed dense membrane shell-and-tube reactors. All utilized Pd or Pd-alloy membranes except one [Itoh et al., 19931 which used yttria-stabilized zirconia membranes. As mentioned earlier, the permeation term used in Ihe governing equations for the tube and shell sides of the membrane is expressed by Equation (10-51b) with n equal to 0.5 [c.g., Itoh, 1987] or 0.76 [e.g., Uemiya et al., 1991]. 

In the first configuration (Figure 11.44), a Pd or Pd-alloy membrane is made of a spiral plate and forms two compartments on the opposite sides of the membrane with double spirals. The edges of the double spiral coiled plate are fixed to the walls of the reactor shell. The number of spirals can be as high as 200. 

For the long-term durability of PEMFC, the acceptable CO concentration appears to be 10-100 ppm. To meet the requirement, three possible reactions can be considered preferential (or selective) oxidation, methanation, and Pd (or Pd alloy) membrane processes. Preferential oxidation (PrOx) of CO can convert CO to CO2, without excessive hydrogen oxidation (to water), to acceptable levels of CO using multi-stage reactors... 

Zhang X, Xiong G, and Yang W, Hydrogen separation from the mixtures in a thin Pd-Cu alloy membrane reactor. Stud. Surf. Sci. Catal. 2007 167(Natural Gas Conversion VIII) 219-224. 

The feed is sent to a convective steam reformer where it is partially converted into hydrogen then hydrogen is recovered through a Pd alloy membrane separation module, while the retentate is sent to the next step or recycled to the first module. By means of a heat recovery system, the operating temperature can be reduced to about 450°C before the membrane unit and again increased before the second reactor. It is possible to replicate the RMM until the desired natural gas conversion is achieved. 

As described above, the principle of an extractor-type membrane reactor has been extensively demonstrated, most often with mbular membranes of 5-10 mm diameter and catalysts having a particle size of around 1 mm in small laboratory reactors where the catalyst is placed as a packed bed inside or around the membrane tube. For Pd-alloy membranes... 

Abstract In this chapter, recent progress on palladium (Pd)-based membrane reactors (MRs) is outUned concentrating, in particular, on the production of pure hydrogen. Aspects of many reactions, as well as analysis of both the Pd-based and the amorphous membranes under study, and the governing equations are presented. Some critical aspects of non-Pd-based membranes are also discussed. All the preparation techniques for pure, alloyed, amorphous, non-Pd-based membranes used in MRs are briefly summarized and compared. Moreover, some problems related to the effect of contamination of the Pd-based membranes on the H2 flux are discussed. 

In addition, the filament reactor can contain a membrane-separation function by grouping threads of filaments around an inner empty reactor core, that guides the permeate and may also increase permeation by reaction. Thus, the tube reactor constructed in such a way comprises two concentric zones, separated by a permeable Pd/Ag alloy membrane in the form of a tube. The reaction takes place in the filament zone. One product such as hydrogen is removed via the membrane and... 

---