Abstract
Background: less value and more environmentally pollutant behavior of toluene in comparison with xylenes makes Toluene methylation to para-xylene is highly environmental, and economical interested reaction in petrochemical industry.
Methods: The present contribution aimed to synthesise Al-HMS with different Si/Al ratios and H-ZSM-11 industrial catalysts with surface modification (SM-H-ZSM-11). The properties of the catalysts were characterized by X-ray crystallography (XRD), Scanning electron microscope (SEM), Thermogravimetric Analysis (TGA), Fourier-transform infrared spectroscopy (FTIR) of pyridine adsorption, and NH3 TPD and its catalytic performance were evaluated for the toluene methylation with methanol by assessing the effects of temperature, pore size, acidic strength, and residence time of reactants on the shape-selectivity of the product.
Significant finding: The results show that whilst an increase in pore size has an unfavorable impact on the shape selectivity of p-xylene, an increase in the strength of the acid site enhances the shape selectivity of p-xylene, hence counterbalancing the effect of pore size. In particular, Al-HMS-5 has a larger pore size than that of H-ZSM-11 but the stronger acidity of Al-HMS-5 is more effective on the shape selectivity of the catalyst. Beside the experimental measurements, a computational process modelling was carried out to estimate percentage of toluene conversion as a function of the reaction temperature (K), WHSV (h-1), toluene/MeOH molar ratio, acidity of catalyst (mmol/g), and surface area(m2/g) using adaptive neuro-fuzzy inference system optimized by particle swarm optimization algorithm. Excellent agreement between measured and predicted toluene conversion confirmed the satisfactory performance of our model with R2 values of 0.9963. The final results show that by suitable tuning of catalyst acidity it is possible to retain high selectivity whilst increasing pore size, hence alleviating potential problems due to diffusion limitation in small pores. Relevancy factor calculated for reaction temperature, WHSV, acidity of catalysts, and BET surface area of catalysts are 1.35, 0.096, 0.0071, and 10.42, respectively which shows that highest sensitivity of toluene methylation relates to BET surface area.
Methods: The present contribution aimed to synthesise Al-HMS with different Si/Al ratios and H-ZSM-11 industrial catalysts with surface modification (SM-H-ZSM-11). The properties of the catalysts were characterized by X-ray crystallography (XRD), Scanning electron microscope (SEM), Thermogravimetric Analysis (TGA), Fourier-transform infrared spectroscopy (FTIR) of pyridine adsorption, and NH3 TPD and its catalytic performance were evaluated for the toluene methylation with methanol by assessing the effects of temperature, pore size, acidic strength, and residence time of reactants on the shape-selectivity of the product.
Significant finding: The results show that whilst an increase in pore size has an unfavorable impact on the shape selectivity of p-xylene, an increase in the strength of the acid site enhances the shape selectivity of p-xylene, hence counterbalancing the effect of pore size. In particular, Al-HMS-5 has a larger pore size than that of H-ZSM-11 but the stronger acidity of Al-HMS-5 is more effective on the shape selectivity of the catalyst. Beside the experimental measurements, a computational process modelling was carried out to estimate percentage of toluene conversion as a function of the reaction temperature (K), WHSV (h-1), toluene/MeOH molar ratio, acidity of catalyst (mmol/g), and surface area(m2/g) using adaptive neuro-fuzzy inference system optimized by particle swarm optimization algorithm. Excellent agreement between measured and predicted toluene conversion confirmed the satisfactory performance of our model with R2 values of 0.9963. The final results show that by suitable tuning of catalyst acidity it is possible to retain high selectivity whilst increasing pore size, hence alleviating potential problems due to diffusion limitation in small pores. Relevancy factor calculated for reaction temperature, WHSV, acidity of catalysts, and BET surface area of catalysts are 1.35, 0.096, 0.0071, and 10.42, respectively which shows that highest sensitivity of toluene methylation relates to BET surface area.
| Original language | English |
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| Journal | Journal of the Taiwan Institute of Chemical Engineers |
| Publication status | Published - 2023 |