Abstract:Catalytic methane decomposition is studied in a fixed bed reactor. Two sets of bimetallic catalysts are employed, namely: 30%Fe-X%Ce/Al 2 O 3 and 30%Fe-X%Co/Al 2 O 3 , and compared with monometallic 30%Fe/Al 2 O 3 catalyst. The effect of promoting Fe with Ce and Co and reduction temperature are investigated. The results reveal that Ce addition has shown a negative impact on H 2 yield while a positive effect on H 2 yield and catalyst stability are observed with Co addition. In terms of number of moles of produced hydrogen per active sites, Fe/Al 2 O 3 has shown a higher number of moles of hydrogen compared to bimetallic catalysts. The catalyst reduced at 500˝C exhibits better activity as compared to the catalyst reduced at 950˝C. Carbon nano-tubes are deposited on the catalyst within the range of 14-73 nm diameter. Two types of carbon nanotubes are detected: Cα and Cγ.

Dry reforming of methane (DRM) is considered a high endothermic reaction with operating temperatures between 700 and 1000°C to achieve high equilibrium conversion of CH 4 and CO 2 to the syngas (H 2 and CO). The conventional catalysts used for DRM are Ni-based catalysts. However, many of these catalysts suffer from the short longevity due to carbon deposition. This study aims to evaluate the effect of La and Ca as promoters for Nibased catalysts supported on two different zeolite supports, ZL (A) (BET surface area = 925 m 2 /g, SiO 2 /Al 2 O 3 mol ratio = 5.1), and ZL (B) (BET surface area = 730 m 2 /g, SiO 2 /Al 2 O 3 mol ratio = 12), for DRM. The physicochemical properties of the prepared catalysts were characterized with XRD, BET, TEM and TGA. These catalysts were tested for DRM in a microtubular reactor at reaction conditions of 700°C. The catalyst activity results show that the catalysts Ni/ZL (B) and Ca-Ni/ZL (B) give the highest methane conversion (60 %) with less time on stream stability compared with promoted Ni on ZL (A). In contrast, La-containing catalysts, La-Ni/ZL (B), show more time on stream stability with minimum carbon content for the spent catalyst indicating the enhancement of the promoters to the Ni/ZL (A) and (B), but with less catalytic activity performance in terms of methane and carbon dioxide conversions due to rapid catalyst deactivation.

The direct synthesis of hydrogen peroxide (H2O2) from molecular hydrogen and oxygen could represent a green and economically attractive alternative to the current indirect anthraquinone process used for the industrial production of hydrogen peroxide. This reaction has been investigated using palladium supported on the Cs-containing heteropolyacid Cs2.5H0.5PW12O40. In addition, the effect of adding copper as a potential activity promoter was investigated. These catalysts were also evaluated for the subsequent degradation of hydrogen peroxide. The catalytic activity of the 0.5 wt.%Pd/Cs2.5H0.5PW12O40 catalyst towards hydrogen peroxide synthesis was greater than that of both the mono-metallic Cu or bi-metallic Pd-Cu analogues with the incorporation of Cu to Pd resulting in a significant decrease in catalytic selectivity for the formation of hydrogen peroxide. Moreover, 0.5 wt.%Pd/Cs2.5H0.5PW12O40 also showed low activity towards the degradation of hydrogen peroxide. Hence the use of the Cs-containing heteropolyacid as a support for Pd gives higher rates of hydrogen peroxide formation when compared with different supported Pd catalysts prepared using supports used in previous studies.

No abstract

Methane steam reforming experiments were carried out at atmospheric pressure for temperatures between 873 and 1073 K and by varying the partial pressure of methane and steam to achieve S:C between 0.5 and 2.5. Mechanistic considerations for Methane steam reforming (MSR) were derived on the basis of Langmuir-Hinshelwood and Eley-Rideal reaction mechanisms based on single-and dual-site associative and dissociative adsorption of one or both reactants. However, discrimination of these models on statistical and thermodynamic grounds revealed that the model representing a single-site dissociative adsorption of methane and steam most adequately explained the data. However, the product formation rates from these experiments were reasonably captured by power-law model. The parameter estimates from the power-law model revealed an order of 0.94 with respect to methane and -0.16 for steam with activation energy of 49.8 kJ mol -1 for MSR. The negative order with respect to steam for methane consumption was likely due to steam inhibition.