Preparation, characterization of zeolite supported metal nanoparticles and investigation of catalitic behaviors in toluene methylation

Advances in the synthesis and characterization of nanomaterials and modern Chemical Engineering have begun to combine large-scale reactions with molecular/atomic level processes in recent years. Nanoparticles (NPs), which have gained importance especially in recent years, form the basis of nanotechnology. Metal NPs can show high catalytic activity due to the large surface area, volume ratio, and presence of more active sites on the surface. Having abundant channels and pore spaces, zeolites are widely used for the support of metal NPs due to their porous structure, high surface areas, shape/size selectivity and excellent catalytic activity. In this thesis, Cu, Ag, Ni metal and Cu/Ag, Ni/Ag bimetal NPs synthesized by wet chemicals method on ZSM-5, FER and SAPO-11 zeolite supports with medium pore size were modified. The wet chemicals method is the preferred method for the preparation of metallic NPs due to its simplicity, economy, efficiency and controllability. Nitrate salts of Cu, Ag, Ni metals, NaBH4 as reducing agent and L-threonine as capping agent were used to synthesize NPs. TEM, SEM, BET, XRD, XRF, UV-Vis, FT-IR and TGA analyzes of the catalysts prepared by this method were performed. The synthesized catalysts were tested for the methylation reaction of toluene at 3 different temperatures (300ºC, 400ºC, 500ºC) and 4 different feed flow rates (WHSV1, WHSV2, WHSV3, WHSV4). It is important to meet the increasing demand for p-xylene by converting toluene, which has a low market demand, into more valuable chemicals such as para-xylene. For this reason, toluene conversion, the selectivity of xylene isomers and xylene yield, p-xylene/m-xylene ratios that peak very close to each other in GC-MS results were calculated according to the products formed as a result of the reaction, and the effects of temperature, flow rate and metal NP modification on the structure were investigated. According to the results, although the modification of metal NPs to the zeolite structure decreased toluene conversion in some cases, the converted toluene was predominantly converted to p-xylene and o-xylene. After NP modification on the zeolite, Ag/SZM-5, Cu/FER and Cu/SAPO-11 catalysts showed high p-xylene selectivity. These activities were found at medium temperatures (400ºC) for ZSM-5 and at high temperatures (500ºC) for FER and SAPO-11. As a result of the reaction, the increase in p-xylene selectivity shows that successful results are obtained with the modification of metal NPs to the zeolite structure. Keywords: Bimetal nanoparticle, Ferrierite, Metal nanoparticle, Methylation, SAPO-11, Toluene, Zeolites, ZSM-5.