Hierarchical Y-modified FAU zeolites for hydrogen transfer deoxygenation and coke resistance in co-conversion of guaiacol and tetralin

Severe coking caused by the strong adsorption of oxygenates and diffusion limitations within the micropores of acid zeolites remains a critical bottleneck to efficient hydrogen transfer deoxygenation during the co-processing of bio-oil and petroleum fractions. Here, hierarchical FAU zeolites were constructed through sequential steaming and acid leaching, followed by yttrium modification to regulate the acid environment, and were evaluated in guaiacol and tetralin co-conversion. Moderate steaming provided the best compromise between deoxygenation and coke suppression, whereas nitric acid leaching further enhanced oxygen removal but simultaneously intensified coke formation, demonstrating that pore reopening alone is insufficient to control secondary condensation. Yttrium modification restored this balance. At an optimized Y loading of 1 wt%, Y/NHY1 achieved an organic liquid yield of 56.10%, a deoxygenation efficiency of 82.9%, and a ring-opening selectivity of 74.29%, while limiting coke yield to 4.93%. DFT calculations further showed that Y modification strengthened tetralin adsorption and decreased the free energy barrier of the key phenolic C–O cleavage step from 2.87 to 2.32 eV. These results demonstrate that efficient hydrogen transfer deoxygenation over FAU requires coordinated regulation of molecular transport and acid properties to suppress coke formation while maintaining efficient oxygen removal.