SYNTHESIS AND CHARACTERIZATION OF ZEOLITE BETA SUPPORTED Fe AND Ni CATALYSTS FOR STEAM GASIFICATION OF PALM KERNEL SHELL FOR HYDROGEN PRODUCTION

• Main Author: MISI, SITI EDA ELIANA BINTI MISI
• Format: Thesis
• Language: English
• Published: 2011
• Online Access: http://utpedia.utp.edu.my/2823/1/Siti_Eda_Eliana-_Msc_in_Chemical_Engineering.pdf; http://utpedia.utp.edu.my/2823/

Production of hydrogen gas (H2) from biomass gasification usually comes with several problems such as the existence of unacceptable level of tars and also ineffectiveness of the catalysts’ performance due to coke deposition. In order to eliminate most of the inconvenience encountered, new types of catalysts have been developed. In this study, monometallic Fe and Ni supported on zeolite beta (BEA) have been prepared by incipient wetness impregnation method. Fe and Ni based bimetallic catalysts supported on BEA were also prepared using two different approach; sequential impregnation and co-impregnation method. The BEA support was impregnated with the solution containing the required amount of metal salts for 4 hours, dried at 120 oC for 16 hours and later calcined at temperatures between 500- 700 ºC for 16 hours. These catalysts were structurally characterized using BET, XRD, FESEM-EDX and TPR. A screening process was performed at temperatures between 600 – 900 oC in a fixed-bed quartz micro-reactor in the absence of a catalyst to determine the optimum temperature for the steam gasification of palm kernel shell (PKS) to H2. The gases produced were analyzed using two on-line gas chromatographs; to analyze sulphur compound in the product gases and to determine the composition of H2, CH4, CO and CO2. The catalysts were then tested for their ability to produce H2 in the steam gasification of PKS in a fixed-bed quartz microreactor with an on-line gas chromatograph at 700 ºC. BET analysis shows that the isotherms plots of the prepared catalysts are type IV which is mesoporous materials. Moreover, the Fe-Ni/BEA catalysts possess lower surface area, higher pore volume and larger pore diameter as compared to other prepared catalysts. Calcination temperature is found to contribute to the crystallization of the prepared catalysts where high crystallization of Fe and Ni was observed in Fe-Ni/BEA (700) catalyst with the formation of NiO and NiFe2O4 phase. The TPR profiles of the bimetallic catalysts show the combination of nickel and iron phases’ reduction which attributed to weak interaction with support (NiO and Fe2O3 phase) and strong interaction with the support (NiAl2O4 and FeAl2O4). From the screening process, the optimum viii temperature for steam gasification of PKS is 700 ºC. This is because maximum of H2 evolvement was achieved at 700 ºC without existence of H2S. The differences in the physicochemical properties of the catalysts affect the catalytic performance whereby it exhibit the PKS to undergo either steam reforming for higher in H2 evolvement or facilitates the oxidation of CO to produce more CO2. In terms of monometallic, both Ni/BEA (500) and Fe/BEA (600) catalysts show the highest concentration of H2 evolved where Ni/BEA (500) catalyst has higher reducibility and surface area while Fe/BEA (600) has larger pore diameter. For bimetallic catalysts, the highest concentration of H2 evolvement in the steam gasification of PKS achieved in the presence of FeNi/BEA (700) and NiFe/BEA (500). At a suitable calcination temperature, FeNi/BEA able to enhances the water gas shift reaction while NiFe/BEA facilitates the steam methane reforming. However, in co-impregnation catalyst, both Fe and Ni promote the active site of the catalyst to increase the crystallization of NiFe2O4 and exhibit the steam methane reforming as well as water gas shift reaction. Fe-Ni/BEA (700) shows the highest composition of H2 gas evolved with 76.32 vol% H2, 18.72 vol% CO2, 4.96 vol% CO and the absence of CH4. The outlet gas composition also shows that the steam gasification of PKS in the presence of Fe-Ni/BEA (700) has a potential to replace the commercial methane reforming for H2 production. Therefore, it can be concluded that various parameters in catalyst preparation resulted in deviation in the catalyst properties and interaction between the active metals with support as well as the catalytic activity.