Modification of USY zeolites with malic–nitric acid for hydrocracking

The modification of commercial ultra-stable Y zeolite using malic acid (MA) and nitric acid (NA) was investigated. A series of factors including the amount of MA and NA solutions, the pH of the solutions, the treatment time, and the reaction temperature were investigated and optimized. The pore structure, acid properties, and crystal structure of modified USY zeolite were characterized by N2-adsorption, temperature-programmed desorption of ammonia (NH3-TPD), pyridine adsorbed Fourier transform infrared spectroscopy, and X-ray diffraction techniques. The as-obtained sample under the optimum conditions presents an increased secondary pore volume up to 0.202 cm3 g−1, which accounts for 45.3 % of the total pore volume, and appropriate acid properties as well as good crystallinity. Furthermore, the USY zeolite modified with different methods was also investigated, indicating that malic–nitric combined acid is an effective modifier for USY zeolite. The modified USY zeolite was used as support to prepare hydrocracking catalysts. The 140–370 °C middle distillate yield of the catalyst is 68.59 %, and middle distillate selectivity can reach up to 81.52 %. Compared with commercial catalyst, the yield and selectivity increased by 8.17 and 5.14 %, respectively.