Study of the catalytic activities of activated carbon-supported catalysts and manganese oxide catalysts for complete oxidation of xylene

• Main Author: Mariquit, Eden Gan
• Format: text
• Language: English
• Published: Animo Repository 2009
• Online Access: https://animorepository.dlsu.edu.ph/etd_masteral/3804
• Institution: De La Salle University

The catalytic activities of activated carbon-supported catalysts and manganese oxide materials for the complete oxidation of xylene, a volatile organic compound were investigated in this research. Two types of activated carbon supported catalysts were prepared using the incipient wetness method; 15 wt.% cerium oxide was impregnated on the activated carbon (CeO2/AC) and 0.3 wt.% platinum was supported on activated carbon (Pt/AC). The activated carbon used as the catalyst support was made from coconut shells and was manufactured using the improved novel process that was developed by the Industrial Technology Development Institute (ITDI) of the Department of Science and Technology (DOST). Likewise, synthetic manganese oxide materials in the form of octahedral layer (OL-1) and octahedral molecular sieve (OMS-1) were tested for xylene oxidation. OL-1 is the synthetic counterpart of the mineral birnessite and has layered structure of edge-shared MnO6 octahedra while OMS-1 is the synthetic counterpart of the mineral todorokite that have a 3x3 edge-shared MnO6 octahedra structure which are corner connected to form one dimensional tunnels having pore diameter of 6.9Å. The catalysts were characterized using SEM-EDX to determine their surface morphologies and elemental analysis; BET method to obtain surface area and pore size distribution measurements and TGA to determine the ignition/critical temperatures of the catalysts. The activities of CeO2/AC, Pt/AC, Ol-1 and OMS-1 for complete xylene oxidation were measured in terms of percent reduction of xylene and yield of carbon dioxide (CO2) per amount of xylene fed. The oxidation reactions were conducted using a flow reactor system equipped with GC-TCD and Poropak Q and Molecular Sieve 5A packed columns. Time course studies were done before proceeding to the determination of the effect of temperature on the activities of all of the catalysts. Using the same experimental conditions for all the catalysts, (catalyst wt. = 0.25 g; W/F = 382.31 g-cat min/ g mol; viii O2/C8H10 (v/v) = 146.77), results showed that the catalytic activity is dependent on the structure and the type of the active material used. Noble metal catalyst supported on activated carbon (Pt/AC) showed the highest catalytic activity, reducing xylene concentration in the feed by 92.4% at 300 ºC. The activities of the manganese oxide catalysts followed with OMS-1 being able to oxidize 60.0% of xylene in the feed at 550 ºC and OL-1 reducing the xylene by 48.4% at 450 ºC. Base metal oxide catalyst supported on activated carbon (CeO2/AC) showed the lowest activity with reduction of 32.2% of xylene in the feed stream at 300 ºC. However if the amount of xylene converted per weight of the active component is to be considered, Pt/AC would still be the best catalyst for the complete oxidation of xylene followed by CeO2/AC, OMS-1 and lastly OL-1.