Dry reforming

The experimental apparatus is consists of reformed gas feeding sections, CO PrOx reaction section in the reactor, and the analysis section with a gas chromatograph system. Simulated reformed gas composition was 75 vol.% H2, 24 vol.% CO2 and 1.0 vol.% CO. The dry reformed feed stream was fed with O2 (A.=l) into the microchannel reactor by MFC (Brooks 5850E). Water vapor (10vol.% of reformed gas) was also fed into the reactor by a s)ninge pump. 

The product stream was separated using a cold trap maintained at 5°C and the the composition of dry reformed gas was analyzed by a gas chromatograph (Agilent 6890N). 

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. 

The direct reaction of methane partial oxidation always competes with total oxidation reactions, which are also responsible for O2 consumption, whereas steam and dry reforming and C-forming reactions are also to be considered. All reactions are catalyzed by the materials which are active in partial oxidation, but different scales of reactivity for the catalysts can be estimated from the experimental data. Total oxidation prevails at the light-off of the fuel-rich stream over most catalysts, but precious metals are more active than transition metals. 

For steam and dry reforming, the following scale of reactivity exists over precious metals [142,143] Ru, Rh>Ni> Pd, Pt. It has been observed that there is a substantial similarity between the orders of activity of the metals for partial oxidation of methane... 

The dry-reforming of methane is a technology that may pressurize the gas-to-liquid (GTL) approach by converting methane and C02 into liquid fuels at the liquefied natural gas (LNG) extraction well. 

Figure 2.79 Composition of dry reformate as a function of reaction temperature. Liquid feed flow rate 6 Ncm3 h-1. Circles, S/C 1.1 squares, S/C 1.5 triangles, S/C 2.0 [124] (by courtesy of ACS).

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. 

Courson, C., Makaga, E., Petit, C., and Kiennemann, A., Development of Ni catalysts for gas production from biomass gasification. Reactivity in steam- and dry-reforming. Catalysis Today 2000, 63 (2 4), 427-437. 

The so-called dry reforming of methane occurs at 600-800°C according to the reaction... 

Abashar, M. (2004). Coupling of steam and dry reforming of methane in catalytic fluidized bed membrane reactors, hit. ]. Hydrogen Energy 29, 799-808. 

Concerning the variations of the H2, CO, CO2, CH, CjHp and H2O contents in the flue gas because of the tar elimination reactions, not only the kinetics of the reactions involved (eqns. 2 and 3) are not known but even their stochiometry. For instance both H2O and CO2 are reactants, which disappear by reaction with tarl, tar2 and tar3 by steam and dry reforming reactions, and products too in the tar-elimination reactions. Their overall variation by reactions given by eqns. 2 and 3 are other unknowns. 

The kinetics of partial oxidation, ATR, and dry reforming of liquid hydrocarbons have also been reported recently.103,155 Pacheco et al.155 developed and validated a pseudo-homogeneous mathematical model for the ATR of isooctane and the subsequent WGS reaction, based on the reaction kinetics and intraparticle mass transfer resistance. They regressed the kinetic expressions from the literature for partial oxidation and steam reforming reactions to determine the kinetics parameters for the ATR of isooctane on Pt/ceria catalyst. The rate expressions used in the reformer modeling and the parameters of these rate expressions are given in Tables 2.19 and 2.20, respectively. 

Brungs, A.J., York, A.P.E., Claridge, J.B., Marquez-Alvarez, C., and Green, M.L.H. Dry reforming of methane to synthesis gas over supported molybdenum carbide catalysts. Catalysis Letters, 2000, 70 (3), 117. 

Laosiripojana, N. and Assabumrungrat, S. Catalytic dry reforming of methane over high surface area ceria. Applied Catalysis. B, Environmental, 2005, 60 (1-2), 107. 

Claridge, J.B., Green, M.L.H., and Tsang, S.C. Methane conversion to synthesis gas by partial oxidation and dry reforming over rhenium catalysts. Catalysis Today, 1994, 21, 455. 

Figure 4. Catalytic activity and stability for steam and dry reforming of methane.

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