Selective catalytic reduction of nitric oxide with propylene over one-step synthesized Cu-SAPO-44 catalysts
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摘要: 以环己胺(CHA)和铜胺络合物(Cu-TEPA)为共模板剂，一步水热合成Cu-SAPO-44分子筛催化剂，用于贫燃条件下选择性催化丙烯还原NO（C3H6-SCR）。采用N2吸附-脱附、X射线衍射（XRD）、透射电子显微镜（TEM）、紫外可见光谱（UV-vis）、NH3程序升温脱附（NH3-TPD）和H2程序升温还原（H2-TPR）等方法对催化剂进行表征。与纯SAPO-44相比，Cu-TEPA的引入显著增强了分子筛的C3H6-SCR催化活性。当Cu/Al=0.25时，Cu-SAPO-44催化剂有着最大的比表面积、丰富的酸性位和较多的孤立Cu2+物种，具有最佳的脱硝性能。随着Cu-TEPA引入量的增加，铜物种会在分子筛表面聚集，生成相对较多无活性的CuO，从而降低了脱硝活性。原位红外光谱（In situ DRIFTS）研究表明，孤立的Cu2+有助于NO和 C3H6的吸附和活化，促进反应关键中间产物−NCO形成。50 h的持久性反应测试表明，Cu-SAPO-44催化剂始终保持>60%的NOx转化率和>90%的N2选择性，表现出良好的反应稳定性。
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关键词:
- Cu-SAPO-44 /
- 选择性催化还原 /
- NO /
- C3H6-SCR
Abstract: Cu-SAPO-44 zeolite catalysts were synthesized by one-step hydrothermal method using cyclohexylamine (CHA) and Cu-amine complex (Cu-TEPA) as co-template. They were used for selective catalytic reduction of nitric oxide with propylene (C3H6-SCR) under lean burning condition. These catalysts were characterized by N2 adsorption-desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-vis spectroscopy (UV-vis), NH3 temperature-programmed desorption (NH3-TPD) and H2 temperature-programmed reduction (H2-TPR). Compared with pure SAPO-44, the introduction of Cu-TEPA significantly enhanced the catalytic activity of C3H6-SCR. When Cu/Al was 0.25, Cu-SAPO-44 catalyst had the largest specific surface area, abundant acidic sites and moderate isolated Cu2+ species, thus it had the best deNOx performance. With the increase of Cu-TEPA introduction, copper species would aggregate on the surface of the zeolite and form more inactive CuO, thus reducing the denitrification activity. In situ study by DRIFTS indicated that isolated Cu2+ could contribute to the adsorption and activation of NO and C3H6, thus enhancing in the formation of −NCO, which was a key intermediate of the reaction. The Cu-SAPO-44 catalyst maintained more than 60% NOx conversion and more than 90% N2 selectivity in long term test of 50 h, showing appropriate reaction stability.-
Key words:
- Cu-SAPO-44 /
- selective catalytic reduction /
- NO /
- C3H6-SCR
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图 1 Cu-SAPO-44催化剂C3H6-SCR活性测试反应示意图
Figure 1 Reaction diagram of catalyst C3H6-SCR test
图 2 不同Cu含量的Cu-SAPO-44催化剂的XRD谱图
Figure 2 XRD patterns of Cu-SAPO-44 catalyst samples with different Cu content and PDF cards of SAPO-44
图 3 不同Cu含量的Cu-SAPO-44催化剂N2吸附-脱附等温曲线（a）和孔径分布（b）
Figure 3 N2 adsorption-desorption isotherm (a) and pore size distribution curves (b) of Cu-SAPO-44 catalyst samples with different Cu contents
图 4 Cu0.25-SAPO-44催化剂的TEM照片（（a）: (1)−(4)）和HR-TEM照片（（a）: (5), (6)）； Cu0.25-SAPO-44催化剂的元素能谱分布（b）
Figure 4 TEM images ((a): (1)−(4)) and High-resolution TEM images ((a): (5), (6)) of Cu0.25-SAPO-44 catalyst sample; EDS mapping results (b) of Cu, Al, Si and P elements of Cu0.25-SAPO-44 catalyst sample
图 5 不同Cu含量的Cu-SAPO-44催化剂的NH3-TPD谱图
Figure 5 NH3-TPD spectra of Cu-SAPO-44 catalyst samples with different Cu contents
图 6 不同Cu含量的Cu-SAPO-44催化剂的UV-vis谱图
Figure 6 UV-vis spectra of Cu-SAPO-44 catalyst samples with different Cu contents
图 7 不同Cu含量的Cu-SAPO-44催化剂的H2-TPR谱图
Figure 7 H2-TPR profiles of Cu-SAPO-44 catalyst samples with different Cu contents
图 8 不同Cu含量Cu-SAPO-44催化剂的NOx、C3H6转化率和N2选择性
Figure 8 NOx, C3H6 conversion and N2 selectivity of Cu-SAPO-44 catalyst samples with different Cu contents （Test conditions: NO 0.05%, C3H6 0.05%, O2 10%, H2O 5%）
图 9 Cu0.25-SAPO-44催化剂样品的脱硝持久性测试
Figure 9 Long term DeNOx test over Cu0.25-SAPO-44 catalyst
图 10 SAPO-44(a)、Cu0.25-SAPO-44(b) 催化剂样品上吸附NO + O2 + C3H6的原位红外谱图
Figure 10 In situ DRIFTS spectra of NO + O2 + C3H6 adsorbed on SAPO-44(a), Cu0.25-SAPO-44(b) catalyst samples for 45 min and then adding C3H6
图 11 Cu0.25-SAPO-44催化剂上NO + C3H6 + O2反应的原位红外光谱谱图
Figure 11 In situ DRIFTS spectra of NO + C3H6 + O2 over Cu0.25-SAPO-44 catalyst sample
表 1 实验过程中使用的试剂
Table 1 Reagents are used during the experiment
Reagent Purity Manufacturer Al2O3 >70% Shandong Guanghui New Material Company CuSO4·5H2O AR, >99% Sinopharm Chemical Reagent Co. LTD H3PO4 AR, >85% Sinopharm Chemical Reagent Co. LTD SiO2 >40% Aldrich H2O AR Lab-produced TEPA CP, >90% Sinopharm Chemical Reagent Co. LTD CHA CP, >90% Sinopharm Chemical Reagent Co. LTD NO 0.50%NO + 99.5%N2 Changzhou Wujin Huayang gas C3H6 5.01%C3H6 + 94.99%N2 Changzhou Wujin Huayang gas O2 ≥99.999% Changzhou Wujin Huayang gas N2 ≥99.999% Changzhou Wujin Huayang gas 
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表 2 Cu-SAPO-44系列催化剂各种元素的成分
Table 2 Content of each component of series Cu-SAPO-44 catalysts
Sample Element content w/% Cu Al P Si Cu0.05-SAPO-44 1.149 16.425 16.403 5.617 Cu0.15-SAPO-44 3.351 16.317 15.529 5.699 Cu0.25-SAPO-44 5.016 15.021 13.463 6.654 Cu0.35-SAPO-44 6.592 14.925 13.746 6.579 Cu0.45-SAPO-44 7.975 14.502 13.134 6.380
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表 3 Cu-SAPO-44系列催化剂的孔隙结构
Table 3 Texture properties of series Cu-SAPO-34 catalysts
Sample SBET / (m2·g−1) Pore volume / (cm3·g−1) Pore size / nm Cu0.05-SAPO-44 394 0.146 1.853 Cu0.15-SAPO-44 429 0.158 1.789 Cu0.25-SAPO-44 488 0.182 1.498 Cu0.35-SAPO-44 452 0.166 1.650 Cu0.45-SAPO-44 443 0.165 1.689
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