Characterization for Li3PO4 catalysts toward elucidation of crystalline form and performance relationship

Abstract

Alkaline lithium phosphates were prepared at different calcination temperatures and their catalytic properties were evaluated. The results showed that the 320 °C‐calcined lithium phosphate had the highest selectivity to allyl alcohol (AA) and higher propylene oxide (PO) conversion among those catalysts calcined from 320 °C to 800 °C. There were two forms of lithium phosphates, β‐form and γ‐form, and the transition temperature was 670 °C. The Brunauer‐Emmet‐Teller (BET) surface area and alkalinity of the β‐Li3PO4 was larger than that of the γ‐Li3PO4, and the change of the crystal forms affected catalytic activity a lot. Infrared spectra (IR) and X‐ray powder diffraction (XRD) results showed that the reason of catalyst deactivation might be related to the carbon deposits and the arrangement of the atoms in the two forms of lithium phosphates. Based on structural analysis for Li3PO4, a new mechanism of PO isomerization was proposed.