首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到19条相似文献,搜索用时 258 毫秒
1.
考察了不同碱土金属(Mg、Ca、Ba)改性对PdO/γ-Al_2O_3催化剂甲烷催化燃烧性能的影响。结果表明,碱土金属改性后,PdO/γ-Al_2O_3催化剂的甲烷催化燃烧起燃活性均有不同程度的提高,活性顺序为CaMgBa。采用X射线衍射、H_2程序升温还原和CH_4程序升温还原等方法对催化剂进行了表征。碱土金属改性后,其与Al_2O_3载体间的相互作用有助于促进PdO微粒团聚,形成晶相PdO,晶相PdO物种对甲烷的活化氧化能力更强,是影响催化剂起燃活性的主要活性位。  相似文献   

2.
采用浸渍法制备Pd-Pt-Ce/Al_2O_3催化剂,考察贵金属Pd和Pt负载量、助剂种类及负载量、空速对催化甲苯燃烧活性的影响。结果表明,适宜的贵金属负载量和助剂可极大提高Pd-Pt/Al_2O_3催化剂活性,当Pd和Pt质量分数分别为0.05%和0.005%、助剂Ce质量分数为1%时,Pd-Pt-Ce/Al_2O_3催化剂在低温条件下表现出较好的催化性能。空速对催化剂的催化活性影响较为明显,适宜的空速低于20 000 h-1。  相似文献   

3.
考察过渡金属Ni对Pd/Al_2O_3催化剂甲烷催化燃烧活性的影响以及过渡金属负载量及循环条件对甲烷降解性能的影响,采用扫描电镜、N_2吸附-脱附以及H_2程序升温还原技术对催化剂进行表征。结果表明,过渡金属Ni的添加对催化剂在(375~475)℃下的甲烷催化燃烧活性产生影响。催化剂经多次重复使用后,催化燃烧活性提高。分析原因为经过渡金属Ni改性后,可与载体形成NiAl_2O_4尖晶石,促进活性组分形成较小晶粒,并改善活性组分分散度,提高催化剂催化活性。  相似文献   

4.
以Al_2O_3为载体,RuCl_3·xH_2O和FeCl_3·6H_2O为活性组分前驱体,采用吸附-沉淀法制备了Ru-Fe/Al_2O_3和Ru/Al_2O_3催化剂,以马来酸二甲酯加氢合成丁二酸二甲酯为探针反应,结合H_2-TPR和XRD表征技术,考察Fe改性Ru基催化剂的氧化-还原性能及催化活性。经氧化-还原循环处理后,催化剂Ru-Fe/Al_2O_3上马来酸二甲酯加氢活性高于Ru/Al_2O_3。XRD结果显示,经处理的Ru-Fe/Al_2O_3上未见金属Ru的特征衍射峰,而Ru/Al_2O_3上出现了金属Ru的特征衍射峰。结合H_2-TPR结果推断,Ru与Fe之间发生了相互作用,这种协同作用可以改善Ru/Al_2O_3催化剂的热稳定性。  相似文献   

5.
段霖  陈莉  丁明  张小伟  王磊 《工业催化》2016,24(7):32-36
采用吸附-沉淀法制备负载Ru质量分数为1.0%的Ru/Al_2O_3催化剂,以马来酸二甲酯催化加氢合成丁二酸二甲酯为探针反应,详细考察预处理条件对Ru/Al_2O_3催化剂加氢性能的影响,并对其进行XRD、TEM和H2-TPR表征。结果表明,焙烧温度越高,催化剂催化活性越低;直接还原活化所得催化剂活性高于空气中焙烧后还原活化所得催化剂。以甲醇为溶剂,在70℃和1.0 MPa条件下,直接还原活化所得Ru/Al_2O_3催化剂上马来酸二甲酯转化率达100%,丁二酸二甲酯选择性约100%。相同时间内,空气焙烧后还原活化所得Ru/Al_2O_3催化剂上马来酸二甲酯转化率接近25%,继续延长反应时间,马来酸二甲酯转化率几乎不变。经高温焙烧还原后,活性组分Ru烧结;直接还原活化后,活性组分Ru高度分散。  相似文献   

6.
以碱共沉淀法制备Mg-Al水滑石,然后采用浸渍法负载活性组分Pt,经焙烧、氢气还原得到Pt/Al_2O_3与Pt/Mg O-Al_2O_3催化剂,采用XRD、N2吸附-脱附、FT-IR、H2-TPR和Py-IR等分析Mg O的加入对Pt/Al_2O_3催化剂结构性能的影响,并在甲基环己烷连续脱氢反应中对比两种催化剂活性。结果表明,Pt/Mg O-Al_2O_3催化剂比表面积小于Pt/Al_2O_3催化剂,且表面基本无酸性活性中心,但表现出与Pt/Al_2O_3催化剂相同的脱氢活性。在Pt负载质量分数2%、催化剂用量0.5 g、甲基环己烷0.1 m L·min-1纯样进料和325℃反应10 h后,原料平均转化率79.9%,脱氢产物只有甲苯,对应的产氢速率192.8 mmol·(g-metal·min)-1,表现出优良的脱氢活性。  相似文献   

7.
通过X射线衍射(XRD)、透射电镜(TEM)和物理吸附(N_2吸附)等手段测定了不同合成条件下制备的Al_2O_3物性参数如比表面积,孔容和孔径等,并以合成的Al_2O_3为载体制备了单Pt/Al_2O_3催化剂,在固定床微型催化反应装置上考察了其在丙烷脱氢过程中催化氢气选择氧化性能。由相同条件下催化剂对混合气中氢气选择性氧化催化结果可知,在铝和葡萄糖物质的量比为1和弱碱条件下制备的Al_2O_3为载体,负载Pt质量分率0.5%的催化剂对烃损耗较小。NH_3的程序升温脱附(NH_3-TPD)表明,该催化剂表面碱性较强,活性较好。  相似文献   

8.
采用溶胶-凝胶法制备了介孔Al_2O_3载体,采用浸渍法制备了系列介孔Co_3O_4/Al_2O_3催化剂,考察了活性组分Co_3O_4的质量百分含量(2%、8%、16%和32%)对催化氧化甲醛性能的影响。研究表明,当Co_3O_4的质量百分含量为16%时,介孔催化剂16%Co_3O_4/Al_2O_3对甲醛的完全氧化反应具有最佳的催化活性,在80℃可将甲醛完全氧化。BET和H_2-TPR表征揭示,催化剂的比表面积和孔容,促进了催化剂中Co_3O_4的高度分散;催化剂拥有低温还原能力,可以提高催化剂催化氧化甲醛的性能。  相似文献   

9.
最近的研究表明,非贵金属的掺杂不仅可以通过改善贵金属Pd催化剂的织构、结构、氧化还原等性能来提高其HC-SCR的催化活性、选择性、稳定性,同时还可以降低贵金属用量从而降低催化剂成本,为其商业化应用做出贡献。基于提高Pd催化活性及降低其用量的目的,通过添加廉价的造孔剂对商业化Al_2O_3进行改性,制备出孔隙率高的Al_2O_3基底,然后通过浸渍法成功制备出Mo改性的Pd/Al_2O_3催化剂,并通过XRD,BET,NH_3-TPD,H_2-TPR,XPS对催化剂进行表征,系统研究了Mo掺杂对Pd催化剂的HC-SCR催化性能的影响,研究表明适当的Mo掺杂可以提高催化剂的催化活性,且当Mo掺杂为5%的时候催化效果最佳。  相似文献   

10.
制备了不同载体、不同金属助剂及不同贵金属Pt含量的蜂窝催化氧化催化剂,并评价了催化剂催化氧化含丙烷有机废气的活性:通过表面结构表征和活性评价实验,发现r-氧化铝作为载体时催化剂活性比分子筛和二氧化钛好;随着Pt含量的增加,催化剂的活性先升高后降低,Pt质量分数为0.2%时催化剂的活性最高;分别制备Pt/MO_x/Al_2O_3(M为铜、锰、钨、铈、锆、镧中的一种),在催化剂表面发现Pt聚集的颗粒,CeO_x的加入可改善贵金属的分布,Pt/CeO_x/Al_2O_3活性最佳,在400℃条件下,丙烷转化率达到95%以上,此时CeO_x的质量分数为1.0%。  相似文献   

11.
Hong He  Changbin Zhang  Yunbo Yu 《Catalysis Today》2004,90(3-4):191-materials
The selective catalytic reduction (SCR) of NO by C3H6 in excess oxygen was evaluated and compared over Ag/Al2O3 and Cu/Al2O3 catalysts. Ag/Al2O3 showed a high activity for NO reduction. However, Cu/Al2O3 showed a high activity for C3H6 oxidation. The partial oxidation of C3H6 gave surface enolic species and acetate species on the Ag/Al2O3, but only an acetate species was clearly observed on the Cu/Al2O3. The enolic species is a more active intermediate towards NO + O2 to yield—NCO species than the acetate species on the Ag/Al2O3 catalyst. The Ag and Cu metal loadings and phase changes on Al2O3 support can affect the activity and selectivity of Ag/Al2O3 and Cu/Al2O3 catalysts, but the formation of enolic species is the main reason why the activity of the Ag/Al2O3 catalyst for NO reduction is higher than that of the Cu/Al2O3 catalyst.  相似文献   

12.
A systematic mechanistic study of NO storage and reduction over Pt/Al2O3 and Pt/BaO/Al2O3 is carried out using Temporal Analysis of Products (TAP). NO pulse and NO/H2 pump-probe experiments at 350 °C on pre-reduced, pre-oxidized, and pre-nitrated catalysts reveal the complex interplay between storage and reduction chemistries and the importance of the Pt/Ba coupling. NO pulsing experiments on both catalysts show that NO decomposes to major product N2 on clean Pt but the rate declines as oxygen accumulates on the Pt. The storage of NO over Pt/BaO/Al2O3 is an order of magnitude higher than on Pt/Al2O3 showing participation of Ba in the storage even in the absence of gas phase O2. Either oxygen spillover or transient NO oxidation to NO2 is postulated as the first steps for NO storage on Pt/BaO/Al2O3. The storage on Pt/Ba/Al2O3 commences as soon as Pt–O species are formed. Post-storage H2 reduction provides evidence that a fraction of NO is not stored in close proximity to Pt and is more difficult to reduce. A closely coupled Pt/Ba interfacial process is corroborated by NO/H2 pump-probe experiments. NO conversion to N2 by decomposition is sustained on clean Pt using excess H2 pump-probe feeds. With excess NO pump-probe feeds NO is converted to N2 and N2O via the sequence of barium nitrate and NO decomposition. Pump-probe experiments with pre-oxidized or pre-nitrated catalyst show that N2 production occurs by the decomposition of NO supplied in a NO pulse or from the decomposition of NOx stored on the Ba. The transient evolution of the two pathways depends on the extent of pre-nitration and the NO/H2 feed ratio.  相似文献   

13.
The NOx storage-reduction catalysis under oxidizing conditions in the presence of SO2 has been investigated on Pt/Ba/Fe/Al2O3, Pt/Ba/Co/Al2O3, Pt/Ba/Ni/Al2O3, and Pt/Ba/Cu/Al2O3 catalysts compared with Pt/Ba/Al2O3, Pt/Fe/Al2O3, Pt/Co/Al2O3, Pt/Ni/Al2O3, Pt/Cu/Al2O3 and Pt/Al2O3 catalysts. The NOx purification activity of Pt/Ba/Fe/Al2O3 catalyst was the highest of all the catalysts investigated in this paper after an aging treatment. That of the aged Pt/Ba/Co/Al2O3 and Pt/Ba/Ni/Al2O3 catalysts was essentially the same as that of the aged Pt/Ba/Al2O3 catalyst, while that of the aged Pt/Ba/Cu/Al2O3 and Pt/Cu/Al2O3 catalysts was substantially lower than the others.

The Fe-compound on the aged Pt/Ba/Fe/Al2O3 catalyst has played a role in decreasing the sulfur content on the catalyst after exposure to simulated reducing gas compared with the Pt/Ba/Al2O3 catalyst without the Fe-compound. XRD and EDX show that the Fe-compound inhibits the growth in the size of BaSO4 particles formed on the Pt/Ba/Fe/Al2O3 catalyst under oxidizing conditions in the presence of SO2 and promotes the decomposition of BaSO4 and desorption of the sulfur compound under reducing conditions.  相似文献   


14.
The reduction of NO under cyclic “lean”/“rich” conditions was examined over two model 1 wt.% Pt/20 wt.% BaO/Al2O3 and 1 wt.% Pd/20 wt.% BaO/Al2O3 NOx storage reduction (NSR) catalysts. At temperatures between 250 and 350 °C, the Pd/BaO/Al2O3 catalyst exhibits higher overall NOx reduction activity. Limited amounts of N2O were formed over both catalysts. Identical cyclic studies conducted with non-BaO-containing 1 wt.% Pt/Al2O3 and Pd/Al2O3 catalysts demonstrate that under these conditions Pd exhibits a higher activity for the oxidation of both propylene and NO. Furthermore, in situ FTIR studies conducted under identical conditions suggest the formation of higher amounts of surface nitrite species on Pd/BaO/Al2O3. The IR results indicate that this species is substantially more active towards reaction with propylene. Moreover, its formation and reduction appear to represent the main pathway for the storage and reduction of NO under the conditions examined. Consequently, the higher activity of Pd can be attributed to its higher oxidation activity, leading both to a higher storage capacity (i.e., higher concentration of surface nitrites under “lean” conditions) and a higher reduction activity (i.e., higher concentration of partially oxidized active propylene species under “rich” conditions). The performance of Pt and Pd is nearly identical at temperatures above 375 °C.  相似文献   

15.
制备不同负载量的Pd基和Pt基催化剂,建立催化剂活性评价装置,考察贵金属Pd和Pt负载量对甲烷转化率的影响,结果表明,甲烷转化率最高的Pd和Pt负载质量分数分别为1.25%和2%,相同负载质量分数0.1%时,Pd基催化剂的甲烷转化率优于Pt基催化剂。催化剂的BET比表面积大小不能反映催化剂的催化活性,二者之间无线性关系。  相似文献   

16.
Pt/Al2O3 catalysts with smaller size of Pt nanoparticles were prepared by ethylene glycol reduction method in two different way and their oxidation activities for three typical VOCs (volatile organic compounds) were evaluated. The catalyst prepared by first adsorption and then reduction procedure is denoted as L-Pt/Al2O3 while the catalyst prepared by first reduction and then loading procedure is defined as R-Pt/Al2O3. The results show that L-Pt/Al2O3 with the stronger interaction between Pt species and Al2O3 exhibit smaller size of Pt nanoparticles and favorable thermal stability compared with R-Pt/Al2O3. L-Pt/Al2O3 is favor of the formation of more adsorbed oxygen species and more Pt2+ species, resulting in high catalytic activity for benzene and ethyl acetate oxidation. However, R-Pt/Al2O3 catalysts with higher proportion of Pt0/Pt2+ and bigger size of Pt particles exhibits higher catalytic activity for n-hexane oxidation. Pt particles in R-Pt/Al2O3 were aggregated much more serious than that in L-Pt/Al2O3 at the same calcination temperature. The Pt particles supported on Al2O3 with~10 nm show the best catalytic activity for n-hexane oxidation.  相似文献   

17.
采用等体积浸渍法和还原法结合制备了Pd/Al2 O3催化剂,通过N2吸附-脱附、SEM、TEM、X射线衍射、X射线光电子能谱和CO原位漫反射傅里叶变换红外光谱等表征手段对制备的样品微观结构进行了系统分析,考察了不同Pd负载量和测试条件下CO催化氧化性能.实验结果表明,水合肼还原法实现了Pd在Al2 O3载体上的均匀分散...  相似文献   

18.
The effect of the Pd addition method into the fresh Pd/(OSC + Al2O3) and (Pd + OSC)/Al2O3 catalysts (OSC material = CexZr1−xO2 mixed oxides) was investigated in this study. The CO + NO and CO + NO + O2 model reactions were studied over fresh and aged catalysts. The differences in the fresh catalysts were insignificant compared to the aged catalysts. During the CO + NO reaction, only small differences were observed in the behaviour of the fresh catalysts. The light-off temperature of CO was about 20 °C lower for the fresh Pd/(OSC + Al2O3) catalyst than for the fresh (Pd + OSC)/Al2O3 catalyst during the CO + NO + O2 reaction. For the aged catalysts lower NO reduction and CO oxidation activities were observed, as expected. Pd on OSC-containing alumina was more active than Pd on OSC material after the agings. The activity decline is due to a decrease in the number of active sites on the surface, which was observed as a larger Pd particle size for aged catalysts than for fresh catalysts. In addition, the oxygen storage capacity of the aged Pd/(OSC + Al2O3) catalyst was higher than that of the (Pd + OSC)/Al2O3 catalyst.  相似文献   

19.
The role of vanadium oxide and palladium on the benzene oxidation reaction over Pd/V2O5/Al2O3 catalysts was investigated. The Pd/V2O5/Al2O3 catalysts were more active than V2O5/Al2O3 and Pd/Al2O3 catalysts. The increase of vanadium oxide content decreased the Pd dispersion and increased the benzene conversion. A strong Pd particle size effect on benzene oxidation reaction was observed. Although the catalysts containing high amount of V4+ species were more active, the Pd particle size effect was responsible for the higher activity.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号