Constructing Y 2 B 2 O 7 (B = Ti, Sn, Zr, Ce) Compounds to Disclose the Effect of Surface Acidity-Basicity on Product Selectivity for Oxidative Coupling of Methane (OCM).

To investigate the influence of surface acidity and basicity on the OCM reaction, four pure-phase Y 2 B 2 O 7 (B = Ti, Sn, Zr, Ce) compounds have been purposely constructed. The exquisite phase structure change results in the generation of different amounts of surface active O 2 - and O - sites, which affects CH 4 molecule activation. Furthermore, both Lewis acidic sites and basic sites are formed on the catalysts in different amounts, which are related to the lattice disorder extent and the choice of A- and B-site elements. It is elucidated with strong evidence that the surface basic sites are favorable to C 2 product selectivity, but the surface acidic sites lead to deep oxidation of CH 4 and the coupling products to form CO x . To design and fabricate Y 2 B 2 O 7 catalysts with better C 2 product selectivity for the reaction, a disordered defect fluorite structure should be engineered with A- and B- site elements having appropriate basicity.