TiO2 preparation by improved homogeneous precipitation and application in SCR catalyst

Ultrasonic treatment and hydrothermal method were applied in the traditional homogeneous precipitation for nano-TiO_2 preparation, which was used as carrier material for the production of honeycomb selective catalytic reduction(SCR) catalyst. The influence rules of the two improved methods on characterization of TiO_2 samples, denitration activity and mechanical strength of honeycomb SCR catalyst samples were mainly focused on. The results indicate that the specific surface area, particle size and uniformity of TiO_2 samples are significantly improved by both of the ultrasonic and hydrothermal treatments compared with the traditional homogeneous precipitation. Also, the denitration activities of catalyst samples are enhanced by the two improved methods(the NO_x reduction ratio increases from 88.89% to 95.45% by ultrasonic homogeneous precipitation process, and to 94.12% by hydrothermal homogeneous precipitation process). On the other hand, because of good spherical shape and high particle distribution of TiO_2 sample from hydrothermal homogeneous precipitation process, the corresponding honeycomb catalyst samples get the best mechanical strength, which is even higher than that of the reference sample from commercial nano-TiO_2. So, it is concluded that the hydrothermal homogeneous precipitation can be a feasible and effective preparation method of TiO_2 carrier for the honeycomb SCR catalyst production.

Novel development of VO_(x)-CeO_(x)-WO_(x)/TiO_(2) catalyst for low-temperature catalytic oxidation of chloroaromatic organics

A novel selective catalytic reduction(SCR)catalyst with high catalytic activity on chloroaromatic organics at lower temperatures(160-180℃)is critical for municipal solid waste incineration(MSWI)plants.This study prepares a series of honeycomb-type VO_(x)/TiO_(2) catalysts and finally develops a new low-temperature catalyst with high catalytic activity in eliminating chloroaromatic organics.Based on the conversion efficiency(CE)of 1,2-dichlorobenzene(1,2-DCB)and CO_(2) selectivity,the optimal VO_(x) content of 4.06%(in weight)in VO_(x)/TiO_(2) catalyst is first confirmed.By modifying CeO_(x) and WO_(x),a novel honeycomb-type catalyst of VO_(x)-CeO_(x)-WO_(x)/TiO_(2) achieves the highest CE(93.1%-93.6%)and CO_(2) selectivity(40.9%-60.7%)at 150-200℃.It was found that the CeO_(x) and WO_(x) can improve the catalytic activity by enriching the surface content of V and O,increasing the proportion of V5+and Osurf,enlarging the supply source of reactive oxygen species and their storage capacity,and accelerating the redox cycle of VO_(x),CeO_(x),WO_(x),and reactive oxygen species.This study can guide the development of monolithic low-temperature catalysts with high catalytic activity in eliminating chloroaromatic organics in MSWI flue gas.