Membrane reactors methane reforming

The hydrothermal stability of the materials is more important as far as the use of membranes in methane reforming reactor is concerned. In general, improving the hydrothermal stability of membranes is difficult owing to the metastable nature of porous, particularly microporous structures and their tendency to change in the way of surface area reduction. Yet, recent reports [33, 34] show that improvements have been made in the hydrothermal stability of membranes based on silica, a material... 

Tong, J. et al., Experimental studies of steam reforming of methane in a thin Pd-based membrane reactor, Ind. Eng. Chem. Res., 44, 1454, 2005. 

Steam methane reforming with membrane WGS reactor for hydrogen production. 

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. 

Shu, ]., B.P.A. Grandjean, and S. Kaliaguine, Methane steam reforming in asymmetric Pd- and Pd-Ag/porous SS membrane reactors, Appl. Catal. A General, 119, 305-325,1994. 

Tsuru, T., K. Yamaguchi, T. Yoshioka, and M. Asaeda, Methane steam reforming by microporous catalytic membrane reactors, AIChE., 50(11), 2794-2805, 2004. 

Uemiya, S., N. Sato, H. Ando, T. Matsuda, and E. Kikuchi, Steam reforming of methane in a hydrogen permeable membrane reactor, Appl. Catal., 67,223-230,1991c. 

Fig. 4. Configuration of a ceramic membrane reactor for partial oxidation of methane. The membrane tube, with an outside diameter of about 6.5 mm and a length of up to about 30 cm and a wall thickness of 0.25-1.20 mm, was prepared from an electronic/ionic conductor powder (Sr-Fe-Co-O) by a plastic extrusion technique. The quartz reactor supports the ceramic membrane tube through hot Pyrex seals. A Rh-containing reforming catalyst was located adjacent to the tube (57).

One of the possible problems in a steam reforming membrane reactor is the formation of carbon, either by cracking of methane (Reaction 4) or the Bou-douard reaction (Reaction 5). 

For dry reforming, carbon formation is very likely, especially when carried out in a membrane reactor [24]. For this application noble metals are used, which are intrinsically less prone to carbon formation because, unlike nickel, they do not dissolve carbon. Irusta et al. [24] have shown above-equilibrium methane conversion in a reactor equipped with a self-supported Pd-Ag tube. Small amounts of coke were formed on their Rh/La203/Si02 catalyst, but this is reported not to have any effect on activity. 

There is a need for low-cost methane steam reforming catalysts that are active at low temperature and resistant to coke formation under membrane reactor conditions. Low-cost (Ni-based) catalysts are also needed that can withstand regeneration conditions in a sorption-enhanced reformer. 

Catalytic membrane reactors are not yet commercial. In fact, this is not surprising. When catalysis is coupled with separation in one vessel, compared to separate pieces of equipment, degrees of freedom are lost. The MECR is in that respect more promising for the short term. Examples are the dehydrogenation of alkanes in order to shift the equilibrium and the methane steam reforming for hydrogen production (29,30). An enzyme-based example is the hydrolysis of fats described in the following. 

Hydrocarbon Reforming 4 [HCR 4] Compact Membrane Reactor for Autothermal Methane Reforming... 

Kurungot et al. [48] developed a novel membrane material and a catalytic membrane reactor for the partial oxidation of methane. The driver of the development was the fact that rates of reforming reactions are much higher compared with the low permeability of conventional palladium membranes [49], Silica was previously recognized as a low-cost alternative to palladium [50], Additionally, the conventional... 

Methane and air were fed to the reactor with an O/C ratio of 1.0 and additional steam at different S/C ratios. The reaction was performed under atmospheric pressure and a nitrogen flow was maintained on the permeate side. The results obtained with the membrane were compared with others generated with the same reactor type without a catalytic membrane in the temperature range 400-575 °C, which is low for methane reforming [51]. 

A simulative comparison of dense and microporous membrane reactors for the steam reforming of methane,... 

Onstot, W.J., Minet, R.G. and Tsotsis, T.T. (2001) Design aspects of membrane reactors for dry reforming of methane for the production of hydrogen. Industrial e[ Engineering Chemistry Research, 40, 242-251. 

Assaf, E.M., Jesus, C.D.F. and Assaf, J.M. (1998) Mathematical modelling of methane steam reforming in a membrane reactor An isothermic model. Brazilian Journal of Chemical Engineering, 15 (2), 160-166. 

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. 

Reforming reactions have been studied in membrane reactors as well. Most well-known is the steam-reforming of various hydrocarbons [10-13], especially methane steam-reforming which is the major source of hydrogen in the world [14], Some research has been performed on CO2 reforming of methane [15] and also a considerable amount of effort has been put in performing the water-gas shift reaction in a membrane reactor [16,18],... 

The goal of the present study is the development of a high temperature membrane reactor for steam reforming of natural gas (methane), which occurs by the following reaction ... 

S.L. Jorgensen, P.E.H. Nielsen and P. Lehrmann, Steam Reforming of Methane in a Membrane Reactor ,... 

M. Chai, M. Machida, K. Eguchi and H. Arai, Promotion of Hydrogen Permeation on Metal-Dispersed Alumina Membranes and its Application to a Membrane Reactor for Methane Steam Reforming , Appl. Catal. A, 110 239-50 (1994). 

E. Kikuchi and Y. Chen, Low-Temperature Syngas Formation by C02 Reforming of Methane in a Hydrogen Permselective Membrane Reactor , Stud. Surf. Sci. Catal. 107 547-53 (1997). 

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