将微晶和纳晶HZSM-5分子筛作为催化剂载体应用于富氧条件下氢气选择催化还原氮氧化物（H₂-SCR）反应。研究发现，微晶HZSM-5载Pt催化剂表现出较好的H₂-SCR反应活性，100℃时NO_x转化率高达90%，N₂选择性也明显高于纳晶HZSM-5载Pt催化剂。利用XRD、SEM、NH₃-TPD、XPS和IR对纳晶和微晶HZSM-5及其载Pt催化剂晶型结构、表面形态、表面酸性以及原位反应表面物种进行表征。结果表明，Pt在纳晶和微晶HZSM-5载体上均高度分散，微晶HZSM-5载体上的总酸量多、酸强度强，有利于催化剂上Pt保持活性金属位，使得催化剂上活性金属Pt位数目较多，进而促进了还原剂H₂的活化及重要活性中间物种氨物种的生成和稳定，从而提高了NO_x转化率和N₂选择性。

Microcrystalline and nanocrystalline HZSM-5 molecular sieves are used as support in study of selective catalytic reduction of nitrogen oxides by hydrogen in presence of excess oxygen (H₂-SCR).The catalytic performances of microcrystalline HZSM-5 supported Pt catalyst (Pt/HZSM-5-M) and nanocrystalline supported Pt catalyst (Pt/HZSM-5-N) are studied under the conditions of 910 ppm NO,90 ppm NO₂,5 000 ppm H₂,10% O₂,N₂ as balance gas and GHSV=36 000 h^-1.The results show that the activity of Pt/HZSM-5-M for H₂-SCR is higher than that of Pt/HZSM-5-N,the maximum NO_x conversion and the maximum N₂ selectivity over Pt/HZSM-5-M reach 90% and 81%,respectively.X-ray powder diffraction (XRD),scanning electron microscopy (SEM),ammonia-temperature programed reduction (NH₃-TPD),X-ray photoelectron spectroscopy (XPS) and Infrared spectroscopy (FT-IR) are employed to characterize the catalysts.The results indicate that Pt is highly dispersed on the support,both the total acid sites and acidity strength of microcrystalline HZSM-5 are more and higher than those of nanocrystalline HZSM-5,thus more active Pt⁰ sites exist on microcrystalline HZSM-5.The activation of H₂ is accelerated,and the formation and storage of active intermediate NH_x species are promoted on Pt/HZSM-5-M catalyst,which may be the origin of the higher activity of Pt/HZSM-5-M in H₂-SCR.