An insufficient amount of NH_(3) (ammonia)will reduce the conversion efficiency of NO_(x),which may lead to excess NO_(x) emissions,resulting in NH3SCR failure.In this article,SCR failure caused by a low NH_(3)NO_(x) ...An insufficient amount of NH_(3) (ammonia)will reduce the conversion efficiency of NO_(x),which may lead to excess NO_(x) emissions,resulting in NH3SCR failure.In this article,SCR failure caused by a low NH_(3)NO_(x) ratio is studied systematically by experiments.The main reasons for a low NH_(3)NO_(x) ratio in SCR include insufficient urea injection,hydrothermal aging of catalysts and urea crystallization.It was found from an insufficient urea injection experiment that with the increase of NH_(3)NO_(x) ratio,the NO_(x) conversion efficiency of the SCR system increased,but the ammonia leakage also increased.The main influencing factors of NO_(x) conversion efficiency are different under different NH3NOx ratios.A flow reactor system was used in the catalyst hydrothermal aging experiment to investigate the effect of hydrothermal aging on catalyst activity.After a 24 h hydrothermal aging experiment at 800℃,the NO_(x) conversion efficiency of the copperbased zeolite catalysts decreased significantly at the boundary of medium and low temperature regions.And the NO_(2)-NO_(x) ratio in the mixture had a significant effect on the catalytic performance.Thermogravimetry coupled to Fourier transform infrared spectroscopy(TGFTIR)was used to analyze the composition of urea deposits in a urea deposits analysis experiment.It was found that the main components of urea deposits were urea and isocyanic acid(HNCO).Preventing HNCO polymerization,especially the formation of CYA,can decrease the formation of urea deposits.展开更多
The title compound N-（（2,6-difluorophenyl）carbamoyl）-1,3-dimethyl-1 H-pyrazole-4-carboxamide（C13H12F2N4O2） was synthesized, and its structure was confirmed by ^1H NMR,HRMS and X-ray diffraction. It crystallizes ...The title compound N-（（2,6-difluorophenyl）carbamoyl）-1,3-dimethyl-1 H-pyrazole-4-carboxamide（C13H12F2N4O2） was synthesized, and its structure was confirmed by ^1H NMR,HRMS and X-ray diffraction. It crystallizes in the monoclinic system, space group P21/c with a = 9.50（2）, b = 10.11（2）, c = 14.07（3） A^°, β = 102.15（3）°, Dc = 1.480 g/cm^3, Z = 4, V = 1320（5） A^°3, the final R = 0.0789 and wR = 0.1860 for 1054 observed reflections with I 〉 2σ（I）. The preliminary biological test shows that the title compound has weak antifungal activities.展开更多
基金the National Key Research&Development Program of China(No.2017YFC0211202).Authors would like to thank editors and anonymous reviewers for their suggestions to improve the paper.
文摘An insufficient amount of NH_(3) (ammonia)will reduce the conversion efficiency of NO_(x),which may lead to excess NO_(x) emissions,resulting in NH3SCR failure.In this article,SCR failure caused by a low NH_(3)NO_(x) ratio is studied systematically by experiments.The main reasons for a low NH_(3)NO_(x) ratio in SCR include insufficient urea injection,hydrothermal aging of catalysts and urea crystallization.It was found from an insufficient urea injection experiment that with the increase of NH_(3)NO_(x) ratio,the NO_(x) conversion efficiency of the SCR system increased,but the ammonia leakage also increased.The main influencing factors of NO_(x) conversion efficiency are different under different NH3NOx ratios.A flow reactor system was used in the catalyst hydrothermal aging experiment to investigate the effect of hydrothermal aging on catalyst activity.After a 24 h hydrothermal aging experiment at 800℃,the NO_(x) conversion efficiency of the copperbased zeolite catalysts decreased significantly at the boundary of medium and low temperature regions.And the NO_(2)-NO_(x) ratio in the mixture had a significant effect on the catalytic performance.Thermogravimetry coupled to Fourier transform infrared spectroscopy(TGFTIR)was used to analyze the composition of urea deposits in a urea deposits analysis experiment.It was found that the main components of urea deposits were urea and isocyanic acid(HNCO).Preventing HNCO polymerization,especially the formation of CYA,can decrease the formation of urea deposits.
基金funded by Natural Science Foundation of Zhejiang Province(No.LY16C140007)National Natural Science Foundation of China(No.31401691)
文摘The title compound N-（（2,6-difluorophenyl）carbamoyl）-1,3-dimethyl-1 H-pyrazole-4-carboxamide（C13H12F2N4O2） was synthesized, and its structure was confirmed by ^1H NMR,HRMS and X-ray diffraction. It crystallizes in the monoclinic system, space group P21/c with a = 9.50（2）, b = 10.11（2）, c = 14.07（3） A^°, β = 102.15（3）°, Dc = 1.480 g/cm^3, Z = 4, V = 1320（5） A^°3, the final R = 0.0789 and wR = 0.1860 for 1054 observed reflections with I 〉 2σ（I）. The preliminary biological test shows that the title compound has weak antifungal activities.
