Alkaline Earth Metal Modified NaY for Lactic Acid Dehydration to Acrylic Acid: Effect of Basic Sites on the Catalytic Performance

Various NaY zeolites modified by alkaline earth metals (Mg, Ca, Sr, and Ba) were synthesized and used as catalysts for the dehydration of lactic acid to acrylic acid to investigate the effects of cationic species on the structure and surface acid/base distribution of the NaY zeolites. The important factors that affect their catalytic performance were also identified. The catalysts were characterized by N-2 physical adsorption/desorption, X-ray diffraction, temperature-programmed desorption of NH3, and temperature-programmed desorption of CO2. The results show that the basic sites that are induced by modified metallic species, particularly the medium basic sites, are mainly responsible for the formation of acrylic acid. The generation of acetaldehyde was affected by the acidic sites. Among the catalysts, 2%Ba/NaY showed the highest yield of acrylic acid at up to 44.6% (38% solution, LHSV = 3 h(-1), 325 degrees C) because it contained the most medium basic sites and a suitable Ba2+ cluster character.