Abstract:The central composite design in the modeling and optimization of catalytic dehydration of ethanol to ethylene was performed to improve the ethylene yield. A total of 20 experiments at random were conducted to investigate the effect of reaction temperature, Si/Al ratios of H-ZSM-5 catalyst and liquid hourly space velocity (LHSV) on the ethylene yield. The results show that the relationship between ethylene yield and the three significant independent variables can be approximated by a nonlinear polynomial model, with R-squared of 99.9% and adjusted R-squared of 99.8%. The maximal response for ethylene yield is 93.4% under the optimal condition of 328 ℃, Si/Al ratio 85, and LHSV 3.8 h -1 . Keywords:central composite design;catalytic dehydration of ethanol;ethylene yield;modeling; optimization Ethylene is commercially produced by the thermal cracking of liquefied petroleum gas (LPG) or naphtha [1] . The process is an endothermic reaction requiring high temperature of 600-1 000 ℃. Compared with the conventional route, the catalytic dehydration of ethanol to ethylene is attractive since it requires lower temperature and offers higher ethylene yield. Moreover, ethanol can be produced from renewable sources, independent of the petroleum source. The dehydration of ethanol to ethylene can be catalyzed using different catalysts, such as γ-alumina [2] , titanium oxides [3] , magnesium oxides [4] , cobalt oxides [5] and H-ZSM-5 zeolite (a type of zeolites) [6] . Earlier researches revealed that H-ZSM-5 catalyst is an efficient catalyst and the reaction temperature, Si/Al ratios and liquid hourly space velocity (LHSV) have a great effect on the ethylene yield [7][8][9] . The experimental design is efficient to estimate the effects of several variables simultaneously [10,11] . Recently, it has been successfully applied to a different process for achieving its optimization [12][13][14] . The main purpose of this paper is to perform the central composite design in order to investigate the effect of Si/Al ratios, reaction temperature, and LHSV on the ethylene yield.
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