مطالعه آزمايشگاهي اثر عوامل موثر بر توليد بنزين با عدد اكتان بالا به روش متافرمينگ و طراحي فرآيند مربوطه

An experimental study on the effect of influential factors on the production of high octane number gasoline by methaforming method an‎d design of the relevant process

مهندسي شيمي

The production of high-octane gasoline through the Methaforming process represents an innovative approach to meeting the growing global deman‎d for gasoline. In this process, in addition to the naphtha feed, methanol is also utilized as a supplementary feedstock, while the by-products include liquefied petroleum gas (LPG), hydrogen-rich gas, an‎d water. The catalyst employed in this process is the H-ZSM-5 zeolite catalyst. In this study, the design of experiments was conducted using the Response Surface Methodology (RSM) to investigate the effects of temperature, pressure, liquid hourly space velocity (LHSV), an‎d methanol feed composition on the aromatic content of the gasoline product an‎d the overall gasoline yield. The results indicated that increasing the reaction temperature from 380°C to 420°C led to an increase in the aromatic weight fraction from 51.3% to 55%, while the gasoline yield decreased from 67.3% to 58.7%. Increasing the pressure from 5 to 15 bar resulted in a slight rise in the aromatic content from 52.5% to 52.7%, whereas the gasoline yield decreased from 76.3% to 64%. With an increase in LHSV from 0.8 to 1.3 h⁻¹, the aromatic content first increased from 51.8% to 53.2% an‎d then decreased to 47.6% as LHSV reached 2 h⁻¹; meanwhile, the gasoline yield increased from 64% to 70.6%. Furthermore, increasing the methanol feed weight fraction from 0.2 to 0.4 led to an increase in both the aromatic content an‎d gasoline yield from 51.5% to 54% an‎d from 65% to 73%, respectively. Since the hydrocarbon feed used in this study was a mixture of four hydrocarbon cuts comprising approximately six hundred individual components, a lumped-species kinetic model was applied for kinetic investigations. The lumped species were categorized based on hydrocarbon structure (including normal paraffins, isoparaffins, olefins, naphthenes, an‎d aromatics) an‎d molecular weight. After defining forty lumped species, thirty-three dominant reaction pathways were proposed to describe the consumption of normal paraffins, naphthenes, an‎d methanol, as well as the formation of aromatics. Kinetic modeling of the reaction network was then performed, an‎d the Arrhenius pre-exponential factors an‎d activation energies were estimated using MATLAB. The strong agreement between the model predictions an‎d experimental data demonstrated the high accuracy of the developed kinetic model. Using the obtained kinetic parameters, process simulations were carried out, an‎d validation plots were generated for five experimental data points that were not included in the model fitting. The validation results confirmed good agreement between the simulated an‎d experimental values. The simulated weight percentage deviations for normal paraffins, isoparaffins, naphthenes, an‎d aromatics were within ±10%, ±10%, ±15%, an‎d +18%, respectively, compared with experimental data. Finally, using Aspen HYSYS with the design specification tool, the reactor volume required for producing 30 barrels per day of gasoline on a pilot-scale was estimated to be 100 liters (length = 1.415 m, diameter = 30 cm).

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