Activity improvement of xylylenediamine as a base catalyst by incorporation in SBA-15 mesoporous material

• Xylylenediamine (XD) can be easily incorporated in SBA-15 mesoporous material.
• XD-SBA catalysts have higher activity than XD in the Knoevenagel condensation.
• The XD-SBA catalysts with secondary amine showed improved catalytic performance.

Meta- and para-xylylenediamine (mXD and pXD, totally XD) were incorporated on SBA-15, MCM-41, and amorphous silica supports using 3-glycidoxypropyltrimethoxy silane (GP) as a connecting material. The amounts and states of GP and XD incorporated in silica supports were examined by thermogravimetry, X-ray diffraction, N2 adsorption, SEM, and FT-IR. The catalytic activities of XD catalysts incorporated on the supports were investigated in the Knoevenagel condensation of benzaldehyde and ethyl cyanoacetate. The maximum amount of GP incorporated in SBA-15 was 0.73 mmol/g, and that of mXD was 0.38 mmol/g on GP(0.73)-SBA, indicating that one mXD molecule was combined with two GP molecules. The incorporation of mXD on the silica supports through GP enhanced the catalytic activity of mXD in the condensation from TOF = 0.0072 s−1 on liquid-state mXD to 0.0258 s−1 on mXD(0.38)-GP(0.73)-SBA. The improvement of the catalytic activities of XD by the incorporation was explained by the increase of the basicity according to the conversion of primary amine to secondary amine. The effects of the size and shape of pores on the catalytic performance of the XD catalysts incorporated in the silica supports in the condensation are discussed.

TOF values over mXD and pXD in the Knoevenagel condensation of BA and ECA significantly increased by the incorporation of them in SBA-15.Figure optionsDownload high-quality image (161 K)Download as PowerPoint slide