Thermal inactivation curves for peroxidase in potato extracts were determined in the range of 100 to 140°C for 10 to 100 sec. The capillary tube method was used to obtain isothermal conditions. The come-up time for the capillary tubes was accurately calculated by analysis method by which thermal inactivation kinetics of enzymes in relation to high temperature processing would be more easily detected. Heat inactivation of potato peroxidase followed first-order reaction kinetics and yielded a curved Arrhenius plot for the temperature dependence at high temperatures. Kinetics parameters, k and Ea, were calculated for potato peroxidase. At temperature range of 100-140°C, the activation energy of peroxidase was lower than that in the range of 78-84°C. It could be elucidated by the scheme of thermal inactivation pathway.

The modification of commercial ultra-stable Y zeolites using citric acid and phosphoric acid was investigated systematically via a L 18 (3 8) orthogonal experiment. The pore structure, acid property and crystal structural of modified USY zeolites were characterized by a variety of means such as N 2 adsorption-desorption, Fourier transform infrared spectroscopy, NH 3-temperature programmed desorption and X-ray diffraction. The optimal modification condition is found to be that the volume ratio of citric acid (0.3 mol/L) and phosphoric acid (0.3 mol/L) is 1.0, and the operation is performed at 100°C for 6 h. The as-synthesized sample presents an increased secondary pore volume up to 0.207 cm 3 /g which accounts for 42.9 % of the total pore volume, and appropriate acidity distribution as well as good crystallinity. In addition, the USY obtained by 1.0 L scale-up modification possesses a secondary pore volume of 0.210 cm 3 /g which accounts for 42.4 % of the total pore volume, showing no obvious scale-up effects. Furthermore, the hydrothermal stability of the modified samples meets the requirements of commercial catalysts for hydrocracking. Performance evaluation was carried out on a 200 mL fixedbed single stage hydrogenation unit using Daqing VGO as feedstock. The 140-370°C middle distillate yield is 66.09 %, and middle distillate selectivity can reach up to 80.45 %. Compared with commercial catalyst, the yield and selectivity are increased by 5.67 and 4.07 %, respectively.

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The modification of commercial ultra-stable Y (USY) zeolite using citric acid (CA) and ammonium fluosilicate (AFS) was investigated. A series of factors including the concentration of CA and AFS, the volume ratio of CA and AFS, adding rate of AFS, reaction time and temperature were studied to get the optimum operation condition. The pore structure, acid property and crystal structural of modified USY zeolite were characterized by a variety of means such as N 2 adsorption, Fourier transform infrared spectroscopy, NH 3 -temperature programmed desorption and X-ray diffraction. The as-synthesized sample presents an increased secondary pore volume up to 0.20 cm 3 /g which accounts for 46.5 % of the total pore volume, and appropriate acidity distribution as well as good crystallinity. In addition, the modified USY zeolite possesses a superhigh Si/Al ratio of 25.7 which is more than twice higher than that of commercial USY zeolite. Furthermore, the hydrothermal stability of the modified samples meet the requirements of commercial catalysts for hydrocracking. Performance evaluation was carried out on a 200 mL fixed-bed single stage hydrogenation unit using Daqing VGO as feedstock. The 140-370°C middle distillate yield is 67.78 %, and middle distillate selectivity can reach up to 80.76 %. Compared with commercial catalyst, the yield and selectivity are increased by 7.36 and 4.38 %, respectively.