C-C coupling of 1-butanol over Mg- and Li-doped L-zeolite

In chemical technologies, the formation of carbon-carbon bonds has gained an increasing importance in recent years. In this work, we studied L-zeolite as a catalyst support for the gas-phase Guerbet coupling of 1-butanol at atmospheric pressure and 400 °C. Low-loaded monometallic (Mg and Li) catalysts were synthesized by incipient wetness impregnation and their physicochemical properties were characterized by N₂ and Ar adsorption-desorption isotherms, XRD, FT-IR, temperature-programmed desorption of NH₃ and CO₂, ²⁹Si and ²⁷Al MAS NMR, and XPS. XRD and FTIR results showed no major change in the crystal structure of the doped zeolite. Impregnation of the zeolite by Mg and Li decreased the surface area and significantly reduced the micropore volume, but crystallinity was preserved. ²⁹Si MAS NMR indicated that desilication had occurred to some extent during catalyst impregnation, which led to the formation of mesopores. The Li/L catalyst showed more basic sites of intermediate strength due to surface Li-O pairs on the surface, which, together with mesoporosity, contribute to enhancing 1-butanol conversion by C-C coupling. The Li/L catalyst was more selective to C₈ oxygenate products than the reference aldol condensation catalyst.