Application of MIL-101(Cr) for biofuel dehydration and process optimization using the central composite design method

Abstract

Nowadays, researchers from various fields are aiming to replace petro-based and other fossil fuels with green and renewable alternatives. One of the potential candidates, requiring a highly pure reactant, is biofuel. The use of alcohol-containing water as a reactant can lead to different types of problems including the generation of side reactions, hydrolysis, equilibrium shifts, catalyst deactivation and process complexity. A metal–organic framework, MIL-101(Cr), was successfully synthesized using the hydrothermal method and subsequently employed for the dehydration of a standard biofuel. With this goal in mind, we aimed to optimize the effects of operational parameters—specifically, initial water concentration, adsorbent dosage, and temperature—using the central composite design (CCD) method, while also analyzing their behaviors by applying variance analysis. To predict the process behavior, we propose a refined quadratic equation under various conditions, achieving an R² value of 95.26. The results showed that the process was more influenced by temperature variations than the other two parameters. The optimal conditions were predicted with an initial concentration of 1.41, catalyst dosage of 0.14, and a temperature of 302.5 K, resulting in a capacity of 1349.72 and a desirability value of 0.95. Additionally, the synthesized MIL-101(Cr) was characterized using XRD, SEM, DSC/TGA, and N₂ physisorption techniques. The results indicated that the particles possessed microporous windows and mesoporous cages, exhibiting a uniform octahedral shape with an average size ranging between 200 and 500 nm.