Optimisation of SBA-15 properties using Soxhlet solvent extraction for template removal

• Ethanol, acetone and methanol promoted the high template extraction efficiency.
• Methanol extraction promoted the increasing of pores diameter in 60%.
• Methanol extraction promoted the increasing of surface area in 48%.

Surfactants are utilised as templates in the synthesis of mesoporous materials. Normally, they are removed using a calcination process, however, careful removal is necessary to conserve the properties of the material. This work proposed surfactant removal from SBA-15 mesoporous silica using a Soxhlet extractor and different solvents. The thermal decomposition of the template was studied in order to understand the process of calcination of SBA-15. The results show that the calcination process influences the properties of the material. All of the utilised solvents enabled the removal of template. Some solvents such as water, acetonitrile and dichloromethane promoted template removal primarily from the surface of the material and others such as ethanol, acetone and methanol promoted the removal of template from within the porous silica. All samples were calcined after the extraction process, however the properties of the resulting materials were different. The greater the template removal, the greater was the surface area and pore size of the materials. Increased pore size caused decreased wall thickness. Methanol was the best of the studied solvents in terms of template removal. The extraction time required was studied and 6 h was necessary to complete the process. Soxhlet extraction is not efficient for the complete removal of template from mesoporous materials. However, the reduced quantity of template in the matrix means that less aggressive calcination is required, and therefore the properties of the mesoporous material can be preserved.

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