Studies On Alkali Resistance Of Internel Reforming Catalysts For DIR-MCFC

Direct internal reforming molten carbonate fuel cell(DIR-MCFC) offers futher advantages of thermal benefits compared with external reforming by using exothermic heat of electrochemical reaction on anode for endothermic heat of reforming reaction. However, the nickel catalyst for internal reforming deteriorates by volatilization of the alkali metals (Li2CO3 and K2CO3) in the electrolyte of the DIR-MCFC. It has provided a challenge to internal reforming catalyst for developers. In the DIR-MCFC there is a belief that it may be possible to extend the lifetime of existing catalysts by protecting the catalyst from alkali attack. Hence, protecing the reforming catalyst from alkali poisoning becomes the key act to extend DIR-MCFC working life, reduce capital cost and maintain efficiency of the system.Silicalite-1 zeolite membrane possesses uniform and well-defined micropores system with pores of nearly molecular size, and good chemical stability, intense mechanical strength and capability of working at high temperature. It can be exist stably in the alkali environment and high temperature (650℃) of the DIR-MCFC. In ths work, two types of Silicalite-1 membrane were prepared to protect the reforming catalysts from alkali poisoning.(1) Alkali-resistant collector plates for DIR-MCFC were designed by synthesis of silicalite-1 zeolite membrane in the holes (400μm) of the collector plates. The silicalite-1 zeolite membrane in these alkaili-resistant collector plates can repel alkali vapor but can be made porous to the product of internal reforming (H2 and CO). Synthesis parameters such as starch concentration, starch/Silicalite-1 ratio, precursor composition, crystallization time were investigated by SEM and gas permeance.Alkali-resistant collector plates P1-P6 were prepared according to different hydrothernal synthesis conditions. The alkali resistance of these plates was measured by out of cell test and steam reforming of methane. The alkali-resistant plates P4 not only expresses high alkali-resistant rate (91.4%), but also show great H2 permeance (1.47×10-6mol/s·m2·Pa) so that they could fit for the requirements of the DIR-MCFC.(2) Core-shell internal reforming catalysts were prepared by synthesis a Silicalite-1 zeolite membrane out of the reforming catalysts. Silicalite-1/Ni/Al2O3-A and Silicalite-1/Ni/Al2O3-B were prepared according to two different preparation paths. Silicalite-1/Ni/Al2O3-A can repel the alkali metals, and its alkali-resistant rate can reach as high as 91.4%. The Silicalite-1 membrane was synthesis on the outer surface of theγ-Al2O3 support, and then Silicalite-1/ Ni/Al2O3-B1,B2 and B3 were prepared by different impregnation methods. Silicalite-1/ Ni/Al2O3-B2 expresses great alkali resistance a catalysis activity due to resolving the problem of decrease of Ni contents and dispers: caused in the first preparation path.