| With the increase of energy demand, and the deterioration of atmosphericenvironment, the energy and environmental problems are increasingly serious. As animportant resource, ventilation air methane (VAM) separation by pressure swingadsorption (PSA) process received great attention in recent years. While in the field ofatmospheric environment protection, researchers in industrial and scientificcommunity attach great importance to NOxselective catalytic reduction (SCR). In theapplication of PSA and SCR, the adsorbants (or catalysts) are the key factors to theprocesses. The thesis focuses on the preparation and performance evaluation ofventilation air methane separation adsorbents and SCR catalysts.Metal ions such as Sr2+, Ni2+doping microporous titanosilicate molecular sievesETS-4and ETS-10were prepared through hydrothermal method, and their adsorptionperformance of N2and CH4were evaluated. The results showed that for ETS-4, theN2and CH4adsorption capacities were enhanced to a certain extent after metal ionsSr2+and Ni2+doped, but the selectivity changes little; For ETS-10, the doping ofmetal ions, such as Sr2+, Ni2+makes the above two kinds of gas adsorption quantitydecreased a certain extent, while the CH4selectivity over N2increased by16%and22%, respectively.Microporous molecular sieve NH4-ETS-10was prepared using liquid ion exchangemethod, the alkali metal ion content of catalyst can be controlled by adjusting thenumber of NH+4ion exchange times. A series of Cu/ETS-10catalysts prepared byimpregnation method and the molecular sieve with different alkali metal content wereused as the carriers. For the catalysts, the influences of the chemical and physicalproperties affected by alkali metal content were discussed, and their NH3-SCRperformances were also analysised. The results showed that the alkali metal content inthe catalyst had a large effect on the activity, and Cu2+ions and nano CuO species inCu/ETS-10catalysts were active for NH3-SCR. Catalysts with less alkali ions hadbetter activity for SCR. In which the presence of alkali metal inhibited the formationof Cu2+ion in molecular sieve, and also due to the overloaded alkali metal ionsleading to part of the molecular sieve pore blocking, which causing the deterioration of its specific surface area. NO-TPD results showed that the alkali metal ion were notconducive to the NO adsorption, but good for NO oxidation to NO2, which wasbenefital for SCR process. Within the scope of the study, with the loss of the alkalimetal content, the catalysts present a tendency of increasing the activity.On the basis of the above work, the effect of Cu loading in Cu-ETS-10catalystprepared through ion exchange method was investicated. The characterization resultsfound that Cu species played a decisive role in NH3-SCR performance. Thetitanosilicate molecular sieve Cu-ETS-10catalyst with microporous structure andhigh specific surface area possessed high activity, N2selectivity and SO2resistancefor NOxselective catalytic reduction (SCR). Cu content in the catalyst could beregulated by changing the number of ion exchange times, and the Cu content could beup to about12.6wt%. Cu species in the catalysts with good dispersion and catalystactivity are closely related to the amount of Cu2+species. When Cu content was9.3wt%, the amount of Cu2+in the Cu-ETS-10catalyst reached the maximum, and boththe NOxconversion and N2selectivity over the catalyst were higher than90%in therange of200~350oC.Ti-Si-CeOxporous material is several common carrier compounds with porousstructure and large specific surface area. A PEG assited coprecipitation method wasadopted for preparing a series of different TiSiCeOxcomposite porous oxide (TSC)with various Ti/Si ratios using tetraethoxysilane (TEOS) and titanium tetrachloride asSi and Ti sources, respectively. The samples containing TiO2, SiO2components at thesame time, with a narrow pore size distribution (3~4nm), and the specific surfacearea decreased with increasing TiO2. The BET results showed that the specific surfacearea of the porous materials can be realized by adjusting the Ti/Si ratio of components.Each component in materials appeared even distribution which could be used as adesired carrier for catalyst preparation. A series V2O5/TSC catalysts using PEGassisted coprecipitation-impregnation mothed were prepared, and the influence of theTi/Si ratio, V2O5loading, calcination temperature and preparation methods of thecatalysts on the NH3-SCR activity were investigated respectively.Porous V2O5/TixSi1-xCe0.025O2.05catalysts were prepared by impregnation methodand the support was synthesized by PEG assistant coprecipitation. The Ti/Si ratioeffect on the surface area and crystallization was investigated. The results of X-raydiffraction (XRD), N2adsorption-desorption isotherm, Fourier transform infraredspectroscopy (FT-IR), and scanning electron microscopy (SEM) demonstrate that the catalysts with meso pores, and the pore size was in the range of3to5nm whenx=0.2~0.8. The results of NH3-SCR performance over the catalysts exhibited that NOxwas removed more than80%in the temperature range of280to450oC even whenx=0.2. Under the experimental conditions, most TiO2components in the V2O5/TSCcatalysts could be replaced by SiO2which was much cheaper, while its NH3-SCRactivity little decreased. The results provided the beneficial reference for the SCRcatalysts obtained with lower cost of production.For V2O5/TSC catalysts, the activity was improved in the low temperature rangewith adding V2O5loading. While at the same time, its NOxconversion over the samecatalyst reduced significantly at a higher temperature range. The corresponding V2O5loading could be adjusted according to the temperature range for applicable catalystwith high activity.Catalysts with a V2O5load of0.5%calcined at various temperatures wereinvestigated. XRD results showed that the main phase structure of V2O5/TSC-04andV2O5/TSC-10catalysts remained anatase phase after a calcination at a hightemperature up to700oC. But the intensity of all the diffraction peaks appearedobvious enhancement, and the half peak width of the peaks decreased, and the resultsshowed that the grain size increased with temperature increased gradually, the specificsurface area of the catalysts gradually decreased. For V2O5/TSC-04, when thetemperature increased, the number of–OH reduced. After calcinations at800oC, bothof catalysts appeared deactivation. The activity in the high temperature desreased waspartly caused by the N2O production increase.In order to examine the V2O5/TSC catalyst in the interaction between activecomponent and carrier more deeply, the catalysts with same chemical compositionprepared by different methods were compared. The results showed that thepreparation method had a great influence on the activity of the catalysts. The physicalmixing method, impregnation method were introduced to get the same composition ofV2O5/TSC-04catalysts. It was found higher NOxconversion at a lower temperaturerange over V2O5/TSC-04-DM with titanium dioxide (the main phase of anatase) asraw materials than others. When the temperature increased to400oC, the conversionof NOxdecreased sharply. |
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