Abstract <p>A series of RHO zeolites were synthesized by steam-assisted dry gel conversion (SAC). The effects of autoclave water volume, crystallization time, crystallization temperature, and ultrasonic treatment on the phase composition and particle size of RHO zeolites were investigated for the first time. Using X-ray diffraction analysis, scanning electron microscopy, and energy dispersive spectroscopy, the SAC method was found to synthesize high-purity and high-crystallinity RHO zeolites. The optimum synthesis conditions include a temperature of 140°C, a reaction time of 48 h, and 0.5 mL of water per 1 g of dry gel.</p>