<p>The catalytic performance of phosphotungstic acid (WPA) hydrates and derived mixed oxide catalysts (0-WPA, D-WPA, Bronze) for vapor-phase dehydration of ethylene glycol to acetaldehyde was systematically investigated through controlled pyrolysis in the 300–700&#xa0;°C temperature range. Experimental results demonstrated that the 0-WPA catalyst, a low-temperature pyrolyzed product with a Keggin structure, exhibited optimal catalytic performance under reaction conditions of 380&#xa0;°C, a space velocity of 7.5&#xa0;h⁻¹, and atmospheric pressure. The reaction achieved a glycol conversion rate of 91.2% and an acetaldehyde selectivity of 88.9%, with stability tests lasting 80&#xa0;h. This performance significantly surpassed both the D-WPA catalyst featuring an exposed phosphotungstic acid structure and the Bronze catalyst characterized by an amorphous metal oxide structure. Multiple characterizations (XRD, Raman, XPS) revealed that the unique polyoxometalate cluster topology in the Keggin structure effectively optimized both surface oxygen vacancy concentration and electron mobility. The distinctive Brønsted–Lewis acid synergy facilitates preferential C–O bond cleavage through optimized dehydration pathways, thereby enhancing catalytic efficiency. This study provides fundamental insights into the structure-activity relationships of polyoxometalate catalysts in alcohol dehydration reactions, establishing a theoretical framework for rational design of high-performance catalytic systems for conversion of ethylene glycol to acetaldehyde.</p> Graphical Abstract <p></p>