The transformation of ethanol over AlPO₄ and SAPO molecular sieves with AEL and API topology. Kinetic and thermodynamic approach

The transformation of ethanol into ether and ethylene was studied over a series of aluminophosphates and silicoaluminophosphates with AFI and AEL topology, at 593 K. It was found that the data followed a simple parallel kinetic scheme. The formation of ether, the less demanding reaction, can be strongly limited by thermodynamics. Based on both the kinetic model and the equilibrium curve for the system considered, a series of parameters were defined in order to determine the relative strength and concentration of the active centres participating in both reactions. Differences in the average specific-activity for the ethanol transformation into ethylene (turnover-like number) were rationalised in terms of differences in the average hydrogen-atoms partial-charge. Structural influence on product distribution due to the shape-selective phenomenon was not observed under the reaction conditions employed.