载体性质对Pt催化剂H2选择催化还原NOx活性和选择性的影响

摘要

The selective catalytic reduction of NOx by H2 (H2‐SCR) was studied over Pt/MgO, Pt/γ‐Al2O3, Pt/ZrO2, and Pt/HZSM‐5 catalysts. The H2‐SCR activities and N2 selectivities of the catalysts were strongly influenced by the amounts of Pt metal in the catalysts and the NOx adsorption capacities of the supports. The acidic surface of HZSM‐5 increased the amount of metallic Pt on the support, de‐creasing the NOx adsorption capacity, resulting in much higher H2‐SCR activity and N2 selectivity. The inferior activities of Pt/MgO and Pt/γ‐Al2O3 are ascribed to the low amounts of metallic Pt and large NOx adsorption capacities of the supports as a result of their basic surfaces. Based on these results and in situ Fourier transform infrared spectroscopic studies of the reaction, it is proposed that the reduction products of nitriteitrate species at the Pt/support interface are N2 or N2O, de‐pending on the relative amounts of active hydrogen and nitrous species involved in the reduction.%研究了Pt/MgO, Pt/γ-Al2O3, Pt/ZrO2和Pt/HZSM-5催化剂上H2选择催化还原消除NOx(H2-SCR)反应。结果发现, H2-SCR活性和N2生成选择性受催化剂中Pt的金属性以及载体的氮氧化物吸附能力影响很大。 HZSM-5的表面酸性使载体对NOx吸附能力较小,使担载Pt以较高的金属性存在,从而导致Pt/HZSM-5催化剂的高活性和高选择性。相反, Pt/MgO和Pt/γ-Al2O3催化剂较差的活性和选择性可归因于其载体的碱性表面、催化剂中Pt较低的金属性以及载体对氮氧化物较大的吸附能力。结合反应的原位红外光谱结果可以认为,在Pt/载体界面处亚硝酸根/硝酸根物种被还原为N2或N2O,取决于该处参与反应的活性H与这些含氮物种的相对数目。