Highly selective and recyclable vanadium‑promoted Mg-Sr-Al oxide catalyst for n‑butanol ethoxylation

2-Butoxyethanol is an important glycol ether widely used as a solvent, wetting agent, emulsifier, and chemical intermediate, and is commonly produced via the ethoxylation of n-butanol with ethylene oxide. The selection of an appropriate catalyst plays a crucial role in controlling product distribution and facilitating downstream purification. In this study, mixed metal oxide catalysts were evaluated for the selective ethoxylation of n-butanol, and a vanadium-promoted Mg-Sr-Al mixed metal oxide (AMSV) was developed as a highly efficient and recyclable heterogeneous catalyst. Under mild reaction conditions (125 °C and 0.3 MPa), the AMSV catalyst achieved 71.27% n-butanol conversion with 67.93% selectivity toward 2-butoxyethanol, significantly outperforming the unmodified Mg-Sr-Al oxide (AMS; 54.26% conversion and 62.67% selectivity) as well as the conventional homogeneous KOH catalyst. The catalysts were synthesized via a controlled co-precipitation method, calcined at 550 °C, and comprehensively characterized using FESEM, XRD, FTIR, CO_2-TPD, and BET analyses. Quantitative product analysis was performed by GC-FID (Agilent 7890 A, HP-INNOWAX column, split ratio 50:1, n-hexanol internal standard), yielding calibration coefficients with R² values exceeding 0.999. The superior catalytic performance of AMSV is attributed to its enhanced textural and surface properties, including a 7.2-fold increase in BET surface area (92.88 m² g^-1), a higher density of moderate-strength basic sites (≈ 900 µmol g^-1, desorption at 400-600 °C), and the presence of Lewis basic V⁵⁺=O surface species, as evidenced by an FTIR band at approximately 995 cm^-1. Reusability tests demonstrated that the AMSV catalyst retained its initial activity and selectivity over consecutive reaction cycles, confirming its excellent structural stability and recyclability. These findings highlight the potential of vanadium-promoted mixed metal oxides as sustainable heterogeneous catalysts for narrow-range alcohol ethoxylation.