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Query: UMLS:C0276640 (TEM)
 20,729 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A series of Co-V-O (meta-CoV2O6, pyro-Co2 V2 O7, and ortho-Co3 V2 O8) catalysts were prepared by microwave oxalate co-precipitation method and characterized by (XRD), TEM, BET, FTIR, XPS, H2-TPR and conductivity measurement. The catalytic characters of the catalysts for propane oxidative dehydrogenation were investigated. The FTIR spectra of catalysts were obtained in the range of 400-1 100 cm(-1) and their major bands were assigned. The peak separation fitting of O(1s) XPS spectra was carried out and the quantity of oxygen species was calculated. The results of XRD characterization showed that pure meta-CoV2O6, pyro-Co2 V2O7, and ortho-Co3 V2O8 with nice structure were obtained. The TEM images demonstrated that the catalysts showed uniform particle with the mean particle size of 20-30 nm. The diagram of the relationship between electrical conductivity and oxygen partial pressure of Co3V2O8 and Co2 V2O7 showed dsigma/dPo2 > 0, which implied that these were p-type semiconductor, and CoV2O6 reverse showed dsigma/dPo2 < 0, which implied n-type semiconductor. 48.12%, 47.82% and 35.24% of C3 H6 selectivities were obtained for p-type semiconductor Co3 V2O8, CO2 V2O7 and n-type CoV2O6 catalysts respectively at 10% C3H6 conversion, and the results showed that p-type semiconductor catalysts Co3 V2O8 and Co2 V2O7 showed higher activity than n-type catalyst CoV2O6. The results of FTIR, XPS, H2-TPR and conductivity measurement indicated that transferring between non-stoichiometric and lattice oxygen that easily happened in Co3 V2O8 and Co2 V2O7 catalysts might promote the oxidation-reduction reaction between different valence vanadium species, and promoted the oxygen vacancy formation. Furthermore, the forming of Co-O-V bridge bond that was easy to shift between Co and V increased the mobile oxygen species of O2-, O2(2-) and O- and made the redox reaction among different valence V be realized. It is concluded that high catalytic properties of p-type semiconductor Co3 V2O8 and Co2 V2O7 can be attributed to the abundant oxygen species O- that existed in these catalysts.
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PMID:[Active oxygen species of Co-V-O catalysts in propane oxidative dehydrogenation analyzed by FTIR and XPS spectra]. 1944

Pt supported on mesoporous silica SBA-15 was investigated as a catalyst for low temperature selective catalytic reduction (SCR) of NO by C3H6 in the presence of excess oxygen. The prepared catalysts were characterized by means of XRD, BET surface area, TEM, NO-TPD, NO/C3H6-TPO, NH3-TPD, XPS and 27Al MAS NMR. The effects of Pt loading amount, O2/C3H6 concentration, and incorporation of Al into SBA-15 have been studied. It was found that the removal efficiency increased significantly after Pt loading, but an optimal loading amount was observed. In particular, under an atmosphere of 150 ppm NO, 150 ppm C3H6, and 18 vol.% O2, 0.5% Pt/SBA-15 showed remarkably high catalytic performance giving 80.1% NOx reduction and 87.04% C3H6 conversion simultaneously at 140 degrees C. The enhanced SCR activity of Pt/SBA-15 is associated with its outstanding oxidation activities of NO to NO2 and C3H6 to CO2 in low temperature range. The research results also suggested that higher concentration of O2 and higher concentration of C3H6 favored NO removal. The incorporation of Al into SBA-15 improved catalytic performance, which could be ascribed to the enhancement of catalyst surface acidity caused by tetrahedrally coordinated AlO4. Moreover, the catalysts could be easily reused and possessed good stability.
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PMID:Characterization and performance of Pt/SBA-15 for low-temperature SCR of NO by C3H6. 2421 34