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91.
On-line infrared spectroscopy has been used to show that isocyanic acid, HNCO, is a substantial primary product of the reaction between NO, CO and H2 over a Pt/SiO2 catalyst. At 230°C it accounts for more than 40% of the CO converted. No isocyanic acid is seen when Al2O3 is placed downstream of Pt/SiO2, or when using a Pt/Al2O3 catalyst under the same conditions, due to rapid hydrolysis of HNCO on the alumina. Isocyanic acid may exist as a trace intermediate in automobile catalytic converters during their warm-up phase but it is unlikely to emerge from the pore system of aluminabased catalysts.  相似文献   
92.
Fourier transform IR spectroscopy of CO and N2, adsorbed at liquid nitrogen temperature, was used to characterize an MFI-type H-FeZSM-5 ferrisilicate which was synthesized with a Si/Fe ratio of 50. Thermal treatment of this material at 773 and 973 K was performed in order to follow formation of extraframework species. On samples fired at 773 K Brønsted acid sites were present which gave an O-H stretching band at 3630 cm–1. These hydroxyl groups formed adducts with both probe molecules, which were monitored by the corresponding bathochromic shift, . Corresponding values for adsorbed CO and N2 were = –270 and = – 100, respectively. Increasing the firing temperature up to 973 K led to complete removal of iron from the zeolite framework, and consequent disappearance of Brønsted acidity. In this process, extraframework iron oxide species were formed which were also characterized by IR spectroscopy of the adsorbed probe molecules. Both CO and N2 gave Lewis-type adducts with coordinatively unsaturated Fe3+ ions present in the extraframework material. A comparison is made with results of a previous study on the H-GaZSM-5 isomorph.  相似文献   
93.
采用溶剂热法在增透的多孔玻璃表面制备负载非晶态有机锆聚合物。通过SEM,XRD,BET,FTIR,UV-Vis,ICP,有机元素分析,荧光光谱(PL)及紫外光电子能谱(UPS )等手段对催化剂进行了测试分析。非晶态有机锆聚合物(2.64 eV)具有比NH2-UiO-66(Zr)(2.74 eV)更窄的禁带宽度,更稳定的光生电子。在光催化反应器中放入2片负载非晶态有机锆的玻璃(总面积50.4 cm2),在300 W的氙灯照射下催化还原CO2合成甲醇,反应4 h后甲醇的产量为443.0 μmol,转换频率(TOF)为8.9 h-1。当0.1 g NH2-UiO-66(Zr)为催化剂时,甲醇的产量为244.3 μmol,TOF仅为0.17 h-1。非晶有机锆聚合物的光催化性能明显优于NH2-UiO-66(Zr)粉末,且循环稳定性良好。  相似文献   
94.
Ammonium-based ionic liquid monomers and their corresponding polymers [poly(ionic liquid)s] are synthesized and characterized for CO2 sorption. The polymers have much higher CO2 sorption capacities than the room-temperature ionic liquids and imidazolium-based poly(ionic liquid)s. For example, P[VBTMA][PF6] with polystyrene backbone has a CO2 sorption capacity of 10.67 mol%. The CO2 sorption is selective over N2 and O2. The effects of cation, backbone, substituent, anion and crosslinking on CO2 sorption are discussed. The sorption mechanism study indicates that CO2 sorption by the poly(ionic liquid)s is a bulk and surface phenomenon.  相似文献   
95.
以Na2CO3为沉淀剂,初步研究了多组分氯盐混合体系(0.6 mol MgCl2+1.1 mol LiCl+3.2 mol NaCl)中选择性沉镁的工艺规律。结果表明:在25~80 ℃,总C与总Mg物质的量比[n(CT)/n(MgT)]为 0.8~1.1时,25 ℃形成针状MgCO3·3H2O,40 ℃以上形成Mg5CO34(OH)2·4H2O不规则片状团聚微球,其中40~50 ℃形成的片状物较为分散且粒径较小,导致固液分离困难。40 ℃时沉镁率最低。温度越高,Li2CO3越易形成,沉锂率越大。n(CT)/n(MgT)越大沉镁率和沉锂率越高。室温(25 ℃)、n(CT)/n(MgT)=1.0时,沉镁率达98%以上,且沉锂率<0.1%,镁锂分离效果最好。  相似文献   
96.
Park  Jong Soo  Doh  Dong Sup  Lee  Kwan‐Young 《Topics in Catalysis》2000,10(1-2):127-131
PdOx/MnO2 has been examined as a catalyst for CO oxidation using a conventional flow reactor at reaction temperatures between 50 and 150°C. In the reaction conditions of GHSV (gashourlyspacevelocity) of 1.22 × 105/h and CO concentration of 2000 ppm, PdOx/MnO2 showed higher catalytic activity compared with PdOx/Mn2O3, which had been previously reported as an effective catalyst due to the cooperative action of Pd and Mn2O3 for this reaction. The reason for higher activity of PdOx/MnO2 than PdOx/Mn2O3 has been investigated using TPR (temperatureprogrammed reduction) and XPS studies. TPR showed that PdOx/MnO2 could be reduced by CO at much lower temperature than PdOx/Mn2O3. During the experiment of reduction and oxidation, XPS showed that the valence of Mn in the PdOx/MnO2 was between 4+ and 3+, which is higher than that of Mn in the PdOx/Mn2O3 catalyst of which the valence has been reported to be between 3+ and 2+. It is known that in this catalyst system the support supplies oxygen onto Pd, where the oxidation occurs with adsorbed CO, and the ability of the support to provide oxygen improves the performance of the catalyst. Therefore, it was concluded that the readiness of MnO2 to be reduced with maintaining a higher oxidation state showed higher CO oxidation activity than Mn2O3 as support for PdOx.  相似文献   
97.
98.
为开发高活性、高收率的合成气制低碳烯烃(STO)双功能催化剂,通过共沉淀法制备非化学计量尖晶石Zn-Cr-Al氧化物,对其织构性质、晶体结构、形貌特征以及表面电荷性质等进行研究。结果表明添加过量锌能够促进晶体粒径减小,表面氧空位增多。其中Zn/(Cr+Al)摩尔比为1.25时锌含量较为适宜,将其与SAPO-34沸石分子筛结合为双功能催化剂用于STO性能研究。在进气n(H2):n(CO)=2:1,3000 mL/(gcat·h),3.2 MPa,400 ℃反应条件下,实现46.9% CO转化率,C2-4烯烃收率高达15.9%,高于大部分已有文献报道(8~14%),特别是副产物CO2选择性仅29.2%,低于普遍报道的40~50% CO2选择性。并且催化剂运行100 h后活性良好,稳定的催化性能使其具有工业应用价值。  相似文献   
99.
通过水解缩聚法制备含有不同苯基含量的超支化聚硅氧烷,探究苯基的引入对超支化聚合物在CO2中溶解性能的影响。浊点压力测试得出苯基的引入在超支化结构中对聚合物在CO2中的溶解度影响不大,超支化聚合物中苯基含量的增加没有导致浊点压力的明显升高,有望实现作为CO2增稠剂兼具较好的溶解度和增稠性能。分子模拟计算分析了超支化聚硅氧烷和直链聚硅氧烷与CO2分子间的相互作用以及超支化聚硅氧烷分子间的相互作用,发现含苯基的超支化聚硅氧烷具有更低的内聚能密度(CED)和溶解度参数(δ),表现出更弱的聚合物分子间相互作用,有利于超支化有机硅氧烷在CO2体系中的溶解。  相似文献   
100.
The influence of the addition of 1–10 vol.% of hydrogen or carbon dioxide to the feed during the partial oxidation of methane was studied over a NiO/γ-Al2O3 catalyst. The addition of H2 decreases the conversion and syngas selectivity. This decrease of performance seems to be related to a higher reduction of the catalyst due to the H2 co-feeding. The addition of CO2 also appears unfavorable to the production of hydrogen but increases the CO yield. A combination of the dry reforming and the reverse water gas shift reactions is suggested to explain the observed modifications in the product yields.  相似文献   
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