Au/TS-1选择性催化氧化NO性能研究

制备了负载型Au/TS-1催化剂,采用XRD、SEM、TEM等方法进行了表征,并将其应用于选择性催化氧化NO反应,考察了各工艺条件对NO催化氧化效率的影响。结果表明,Au/TS-1催化剂具有良好的结晶度,Au粒子成功地负载在TS-1上。该催化剂在选择性催化氧化NO反应中具有优异的低温催化氧化活性,在NO体积分数为1×10-3,O2含量为10%,空速为5 000 h-1,Au的负载量为1.0%,180℃时,NO的氧化率高于55%(此时最适宜吸收处理);260℃时,氧化率可达到78%。     

整体式堇青石负载的Cu-SSZ-13分子筛催化剂的制备及其氨选择性催化还原脱硝性能

以聚乙烯醇（PVA）或拟薄水铝石（SB粉）为涂覆助剂，采用超声波辅助分散法将Cu-SSZ-13分子筛涂覆于蜂窝状堇青石（Cordierite）上，制备了整体式堇青石负载的Cu-SSZ-13分子筛催化剂（Cu-SSZ-13/Cordierite），用于氨选择性催化还原（NH₃-SCR）脱硝，并结合XRD、氮气吸附、SEM及H₂-TPR等表征手段，研究了涂覆助剂对该催化剂的Cu-SSZ-13涂层稳定性、NH₃-SCR脱硝活性、水热稳定性和抗SO₂毒化能力的影响。结果表明，以PVA为涂覆助剂制备的整体式Cu-SSZ-13（PVA）/Cordierite催化剂，其Cu-SSZ-13涂层稳定、脱落率低，选择性催化还原脱硝活性与Cu-SSZ-13原粉基本相当；同时，该Cu-SSZ-13（PVA）/Cordierite催化剂也具有较好的耐高温水热稳定性和抗硫中毒能力，在移动源和固定源脱硝方面有较好应用前景。     

制备方法对氧化锰八面体分子筛的NH_3选择性催化还原NO_x性能的影响

采用不同方法制备了一系列氧化锰八面体分子筛(OMS-2)催化剂,考察了制备方法对其低温NH3-SCR催化性能的影响,并采用BET、XRD、Raman、H2-TPR、XPS和TEM等手段对催化剂的物化性质进行表征。结果表明,OMS-2催化剂在50~150℃时其低温SCR活性明显优于MnOx催化剂,OMS-2催化剂在120℃时NOx转化率接近100%。此外,不同的制备方法对OMS-2催化剂的SCR脱硝活性影响明显。其中,固相法制备的OMS-2催化剂的SCR活性最佳。H2-TPR测试结果表明,OMS-2更容易发生氧化还原反应,MnOx还原峰对应的温度较高。XRD、TEM和XPS分析结果表明,低结晶度和高分散性的无定形催化剂有利于低温SCR反应,较高的表面晶格氧和无定形MnO2物种是OMS-2催化剂具有优异低温SCR活性的主要原因。     

Selective catalytic reduction of NO over metal oxides incorporated zeolites

Selective catalytic reduction (SCR) of nitric oxide in an oxygen-rich atmosphere with propylene as a reductant has been investigated over supported La-Co-oxide (mixed metal oxide) catalysts prepared by the modified citrate method. Loading on ZSM-5 support gave greatly enhanced activity in the reduction of NO at relatively low temperatures. This SCR activity could be ascribed to incorporation of the mixed metal oxide into ZSM-5 as an amorphous perovskite phase via preparation.     

SO_2和H_2O对CeO_2/TiO_2/堇青石催化剂选择催化还原NO_x性能的影响

采用浸渍法制备了以堇青石为基底、氧化铈为活性组分的整体式脱硝催化剂CeO2/TiO2/堇青石催化剂。通过与商业钒基催化剂(V2O5-WO3/TiO2/堇青石)的对比研究发现,CeO2/TiO2/堇青石催化剂表现出了优良的抗硫抗水性能,经过30 h抗硫抗水实验,CeO2/TiO2/堇青石催化剂的氮氧化物转化率仍能保持在70%以上,仅下降了5%。BET、XRD、FT-IR和TG表征结果表明,在含硫含水气氛中反应时,CeO2/TiO2/堇青石和V2O5-WO3/TiO2/堇青石催化剂表面均有硫酸铵盐的生成,且前者的生成量明显低于后者。NH3-DRIFT分析结果表明,在含硫含水气氛中两种催化剂表面Brnsted酸性都被增强,而Lewis酸性有所减弱。进一步的XPS分析结果表明,烟气中的SO2+H2O会使催化剂表面Ce4+向Ce3+发生转化,从而导致化学吸附氧含量增加,这是CeO2/TiO2/堇青石催化剂具有优良抗硫抗水性能的重要原因。     

Co/Fe/Al2O3/cordierite催化C3H6选择性还原NO的实验研究

采用溶胶凝胶法和浸渍法制备了负载于蜂窝陶瓷上的Co/Fe/Al₂O₃/cordierite催化剂,在陶瓷管流动反应器上对其催化C₃H₆选择性还原NO的性能进行了测试。结果表明,该催化剂表现出最优脱硝性能,在模拟烟气条件下,当反应温度为550 ℃时可实现97%的脱硝效率。Co的引入可显著增强Fe/Al₂O₃/cordierite催化剂抗SO₂和H₂O的能力。在模拟烟气中同时引入0.02% SO₂和3% H₂O后,1.5Co/Fe/Al₂O₃/cordierite的脱硝性能受影响甚微,当反应温度高于500 ℃时1.5Co/Fe/Al₂O₃/cordierite催化C₃H₆还原NO的效率均可达到90%以上;相比之下,未经Co修饰的催化剂Fe/Al₂O₃/cordierite脱硝性能受到了严重的抑制,在整个反应温度区间（200-700 ℃）内,其催化C₃H₆还原NO的效率最高不足50%。XRD和SEM表征结果表明,经过适量的Co修饰后的1.5Co/Fe/Al₂O₃/cordierite表面变得更疏松,且形成了以钴铁和钴铝双金属氧化物为主要成分的球状晶粒。H₂-TPR结果表明,相比于Fe/Al₂O₃/cordierite,1.5Co/Fe/Al₂O₃/cordierite有更好的低温还原性能。Py-FTIR结果表明,Co的引入可使催化剂表面的Lewis酸明显增加,且生成了Brønsted酸。N₂吸附-脱附表征结果表明,Co可增大催化剂的比表面积。     

Simultaneous soot combustion and NOx reduction over a vanadia-based selective catalytic reduction catalyst

Simultaneous NO_x reduction and soot combustion over a commercial vanadia-based selective catalytic reduction (SCR) catalyst were investigated. Carbon black was used as model soot. The impact of the contact intensity between carbon and catalyst was studied. The experiments appeared as promising results for the utilization of vanadia-based SCR catalysts in SCR on filter system as, in the SCR operating temperature range (250–400 °C), no significant impact of the presence of carbon black on NO_x reduction was observed. However, a decrease in the specific carbon oxidation rate was highlighted. This latter increases with the contact between carbon and catalyst and is attributed to a lack of NO₂, consumed by the fast SCR reaction. At temperatures greater than 400 °C, the contact between carbon particles and the SCR catalyst partially inhibits the NO_x reduction, whereas it exhibits a catalytic effect on the carbon oxidation rate. The tighter the contact between the two materials, the more significant is this behavior. A redox mechanism, which competes with the redox cycle of the SCR mechanism, was proposed. The impregnation of a V-based SCR catalyst with 2 wt % of calcium was also performed. A drastic loss of DeNO_x activity was observed, whereas the effect of the contact between carbon and catalyst was reduced.     

丙烷在Ce-Fe/Al2O3/cordierite上选择性催化还原NO

利用凝胶溶胶法和浸渍法制备了Ce-Fe/Al₂O₃/cordierite催化剂,实验研究了其催化丙烷选择性还原NO的特性。结果表明,当铈的负载量从1%增加至5%时,Ce-Fe/Al₂O₃/cordierite的C₃H₈-SCR性能先增强后减弱,3.5Ce-Fe/Al₂O₃/cordierite具有最佳的脱硝性能,在有氧条件下,600℃时可实现96.5%的脱硝效率。Ce的加入能够提升Fe/Al₂O₃/cordierite催化剂的抗硫性能。烟气中通入0.02%的SO₂后,3.5Ce-Fe/Al₂O₃/cordierite催化丙烷还原NO的转化率始终维持在93%,而没有经过Ce修饰的Fe/Al₂O₃/cordierite的NO转化率从88%下降为80%左右。利用XRD、N₂吸附-脱附、SEM、H₂-TPR、吡啶吸附红外光谱等手段研究了催化剂的物理化学性质。结果表明,加入助剂铈能与Fe形成了固溶体,增加催化剂表面Lewis酸浓度和氧化还原能力,从而提高了催化丙烷还原NO的性能。过多的铈引入会减少Fe₂O₃结晶体的形成,不利于在C₃H₈-SCR反应中形成NO₂/NO₃^-物种,从而导致NO还原效率下降。     

V2O5-WO3/TiO2催化剂氨法SCR脱硝反应动力学研究

In this work, a kinetic study of the selective catalytic reduction of NO with NH3 has been carried out. After proving the operating condition that the effect of intraphase diffusion and interphase mass-transfer processes can be ignored, the selective catalytic reduction of NO with NH3 on the catalytic activity of V2O5-WO3/TiO2 has been carried out with fixing the feed gas flow rate and composition （ NO, NH3, O2 ） while varying the catalyst loading. Based on the experimental results of NO removal efficiency, the empirical catalytic reaction rate equation of NO with NH3 has been obtained using differential analysis. The experimental result is further proved by the graphic integral method at the temperature from 320℃to 400 ℃ The reaction order is 1 to NO and zero to NH3. The reaction follows the Eley-Rideal mechanism model.     

catalytic activity of comgal, coal and mgal of mixed oxides derived from hydrotalcites in the selective catalytic reduction of no with ammonia

Summary Calcined CoMgAl LDHs and a Co-impregnated LDH were characterized by XRD, N₂ physisorption, TPR and ICP elemental analysis, then tested in the selective catalytic reduction (SCR) of NO with ammonia. Cobalt deposited by impregnation on LDH leads to the more active and selective catalyst. On this type of catalyst nearly 80% of conversion and selectivity to N₂ were reached at 578 K with a volume space velocity of 2200 h^-1.     

Development of the bifunctional catalyst Mn-Fe-Beta for selective catalytic reduction of nitrogen oxides

The catalytic properties of the Mn-Fe-Beta system with Mn contents in the range 0.1–16 wt.% were studied in the selective catalytic reduction (SCR) of NO _x with ammonia. The catalyst structure was investigated using IR spectra of adsorbed NO, temperature-programmed reduction with hydrogen (H₂-TPR), X-ray diffraction analysis, and ESR. The use of manganese as a promoter substantially increases the activity of iron-containing catalysts in the SCR of NO _x with ammonia. At low contents (<2 wt.%), Mn exists in the cation form and the catalytic activity of the Mn-Fe-Beta system does not increase. At a higher content of Mn, clusters MnO _x begin to form, which are highly active in the oxidation of NO to NO₂ and the low-temperature catalytic activity of the Mn-Fe-Beta system increases. The observed increase in the low-temperature catalytic activity in the process of SCR of NO _x with ammonia is related to a change in the reaction route. The MnO _x clusters favor the oxidation of NO and the iron cations facilitate the reaction of “fast” SCR.     

New insight into selective catalytic reduction of nitrogen oxides by ammonia over H-form zeolites: a theoretical study

Density functional theory calculations were carried out to investigate the reaction mechanism of selective catalytic reduction of nitrogen oxides by ammonia in the presence of oxygen at the Br?nsted acid sites of H-form zeolites. The Br?nsted acid site of H-form zeolites was modeled by an aluminosilicate cluster containing five tetrahedral (Al, Si) atoms. A low-activation-energy pathway for the catalytic reduction of NO was proposed. It consists of two successive stages: first NH(2)NO is formed in gas phase, and then is decomposed into N(2) and H(2)O over H-form zeolites. In the first stage, the formation of NH(2)NO may occur via two routes: (1) NO is directly oxidized by O(2) to NO(2), and then NO(2) combines with NO to form N(2)O(3), which reacts with NH(3) to produce NH(2)NO; (2) when NO(2) exceeds NO in the content, NO(2) associates with itself to form N(2)O(4), and then N(2)O(4) reacts with NH(3) to produce NH(2)NO. The second stage was suggested to proceed with low activation energy via a series of synergic proton transfer steps catalyzed by H-form zeolites. The rate-determining step for the whole reduction of NO(x) is identified as the oxidation of NO to NO(2) with an activation barrier of 15.6 kcal mol(-1). This mechanism was found to account for many known experimental facts related to selective catalytic reduction of nitrogen oxides by ammonia over H-form zeolites.     

TS-1/H2O2催化模拟汽油中噻吩的选择氧化研究

随着环境法规的日益严格,世界各国对于燃料中硫质量分数做了新的规定,要求车用燃料的硫控制在10×10-6~50×10-6,燃料电池硫的质量分数控制为(1×10-6。要达到这样高的脱硫深度,传统的脱硫方法面临着极大的挑战[1]。因此,其他非HDS脱硫方法受到研究者关注,其中氧化萃取深度脱硫     

铁铈复合氧化物催化剂SCR脱硝的改性研究

利用共沉淀法制备了铁铈催化剂,考察添加钛、锆、钨和钼对其SCR脱硝的改性规律。结果表明,钨和钼的添加提高了铁铈催化剂高温脱硝性能,却使其低温活性有所降低;钛的添加对铁铈催化剂脱硝性能具有促进作用,尤其提高了其低温活性,并拓宽了其完全转化温度窗口,为最佳改性物。当钛的物质的量比逐渐由0.10增至0.40,铁铈钛催化剂低温脱硝效率先增大后减小,但其高温脱硝效率逐渐增大至100%,钛的最佳物质的量比为0.15。XRD和N₂吸附分析结果表明,钛能优化铁铈催化剂的孔隙结构,增大其比表面积和比孔容,细化其孔径,并与催化剂中铁、铈氧化物形成良好的固溶体,从而提高了铁铈催化剂的SCR脱硝性能。Fe_0.8Ce_0.05Ti_0.15O_z催化剂在150～400℃取得了高于90%的NO_x转化率。     

铁铈复合氧化物催化剂SCR脱硝反应动力学研究

利用共沉淀法制备了铁铈复合氧化物催化剂,在积分实验系统上考察了NO初始浓度、NH₃/NO比及O₂浓度对其SCR脱硝活性的影响;并借助微分系统探讨了其SCR脱硝的催化反应动力学,构建了铁铈复合氧化物催化剂的催化脱硝反应动力学模型.实验结果表明,NO初始浓度越高,每克催化剂的NO转化率越高;随着NH₃/NO比的增加,NO转化率先迅速增加后趋势减缓,最终趋于稳定;O₂在NH₃-SCR反应中起着重要的作用;在175~225 ℃下,Fe_0.95Ce_0.05O_z催化剂的NO和NH₃反应级数分别为1级和0级,O₂的反应级数接近0.5级,该反应的表观活化能为42.6 kJ/mol.     

Selective catalytic reduction of nitrogen monoxide with propene over CuCl/MCM-41 catalysts

Selective catalytic reduction of nitrogen monoxide with propene over two kinds of CuCl/MCM-41 catalysts prepared by a dispersion method has been studied. It was found that CuCl/AlMCM-41 exhibits substantially higher activity over CuCl/SiMCM-41. Characterization of these samples by H₂-TPR, IR and XRD showed that the active copper species were mainly related to Cu²⁺ and Cu⁺ ions in CuCl/AlMCM-41 catalyst.     

Fe-V/TiO_2催化剂NH_3选择性催化还原柴油车尾气NO_x

采用浸渍法制备了一系列不同Fe/V比例的Fe-V/TiO2催化剂,考察了催化剂在模拟柴油车尾气中催化还原NOx的催化性能,采用TG、XRD、H2-TPR、NH3-TPD和Raman光谱对催化剂进行了表征。结果表明,当Fe引入后,能显著降低V2O5在高温下的挥发,减轻了钒系催化剂在移动源的生物毒性危害。其中,Fe/V比为1∶1(Fe1-V1/TiO2)的催化剂形成了FeVO4活性中心,表现出最好的催化活性,在220~420℃NOx转化率可达到90%以上。此外,Fe1-V1/TiO2催化剂高温热稳定性较好,并且具有较强的抗硫性能。     

改性Cu-Mn/SAPO-34催化剂在SCR脱硝反应中的特性研究

采用浸渍法制备了系列铜锰复合氧化物分子筛催化剂(Cu-Mn/SAPO-34),在固定床反应器上考察不同Cu/Mn质量比对分子筛催化剂选择催化还原NO的影响,利用XRD、NH_3-TPD、H_2-TPR、XPS等手段对催化剂进行了表征分析。结果表明,双金属改性的Cu-Mn/SAPO-34催化剂在NH_3-SCR反应中表现出较为优异的催化活性,具有较宽的活性温度窗口。当Cu/Mn质量比为1∶4时,催化剂具有最宽的活性温度窗口,NO_x转化率在250℃已达到85.39%,在300-400℃转化率均达到96%以上,450℃时仍能达到90%。铜和锰物种高度分散于催化剂表面,未改变SAPO-34的晶体结构,且构成协同作用。Cu-Mn共同负载促进了Cu~(2+)向Cu~+的转变,增加了高价态Mn~(4+)和Mn~(3+)的比例,有利于提高低温活性,促进催化反应的进行。Cu-Mn/SAPO-34/1∶4具备丰富的酸性位、良好的氧化还原性能和抗SO_2/H_2O性能,该配比有助于催化剂的催化活性和稳定性的提高。     

原位漫反射傅里叶变换红外光谱研究锰铁基催化剂上低温选择性催化还原反应机理简

采用自蔓延燃烧法制备了Ti_0.9Mn_0.05Fe_0.05O_2-δ催化剂,运用原位漫反射傅里叶变换红外光谱对该催化剂的NO和NH₃稳态吸附以及NO和NH₃瞬态反应进行了详细地分析与讨论. 结果表明,相比于Lewis酸性位,150℃时Brönsted酸性位吸附的NH₃更具有SCR活性;与双齿硝酸盐和桥式硝酸盐相比,NO吸附产生的单齿硝酸盐是主要的中间物种;该SCR反应遵循Eley-Rideal和Langmuir-Hinshelwood机理,但以后者为主. 另外,O₂的存在有利于NO的氧化和配位态NH₃的活化.