Incorporating Aluminum Into the Structure of SBA-15 by Adjusting the pH and Adding NaF

Abstract

The Al incorporation on SBA-15 type material and the effects of pH adjusting and presence of NaF were studied. The direct synthesis method was performed for comparison. The following parameters were evaluated: the Si/Al ratio, pH increase, and amount of NaF added. These parameters have a great influence on the synthesis of the mesoporous Al/SBA-15 type, but the pH the most influential parameter for the incorporation of Al into the SBA-15 structure. The formation of the SBA-15 structure was observed through the direct synthesis method. However, aluminum is not present in the material. The increase in pH contributed to the formation of a disorganized material. By EDX, it was observed that synthesis with a Si/Al = 5 ratio and pH approximately 4 provides materials containing aluminum. When the amount of aluminum during the synthesis is lower, a pH of approximately 8 is required to incorporate aluminum into the final material. The Al-NMR analysis showed that it was possible to insert aluminum in the structure of SBA-15, but with the presence of aluminum hexa and pentacoordinated. In the catalytic test of the dehydration reaction of ethanol, the samples with higher aluminum contents showed better catalytic performance due to its higher acidity.

Keywords

• Al/SBA-15
• direct synthesis
• pH adjustment