發(fā)布時(shí)間：2018-05-22 09:21

  本文選題：相似相分散 + SnO_2/TiO_2��； 參考：《南昌大學(xué)》2017年碩士論文

【摘要】：單層分散理論認(rèn)為,鹽類和金屬氧化物等可在載體表面自發(fā)分散形成亞單層或單層結(jié)構(gòu),具有單層分散閾值。這一理論已被普遍接受,并為有效設(shè)計(jì)高性能催化劑提供了重要依據(jù)。本文基于單層分散理論,探究了同一金屬氧化物負(fù)載在化學(xué)組成相同、晶體結(jié)構(gòu)不同的金紅石型(r-TiO_2)和銳鈦礦型(a-TiO_2)TiO_2上的分散性能及催化性能差異。SnO_2為金紅石型結(jié)構(gòu),與金紅石型TiO_2晶型相同。采用物理混合法制備了一系列不同SnO_2負(fù)載量的n%SnO_2/r-TiO_2、n%SnO_2/a-TiO_2和n%SnO_2/P25催化劑,通過(guò)XRD外推法測(cè)定了SnO_2在r-TiO_2、a-TiO_2和P25上的單層分散閾值分別為0.559 mmol/(100 m~2 r-TiO_2)、0.229 mmol/(100 m~2 a-TiO_2)和0.305 mmol/(100m~2 P25)。這表明被負(fù)載的金屬氧化物與載體金屬氧化物晶體結(jié)構(gòu)相同時(shí)更有利于被負(fù)載組分的分散。類似于“相似相溶”原理,我們首次發(fā)現(xiàn)了“相似相分散”現(xiàn)象。為驗(yàn)證“相似相分散”現(xiàn)象,采用沉積沉淀法制備一系列不同SnO_2負(fù)載量的n%SnO_2/r-TiO_2和n%SnO_2/a-TiO_2催化劑,利用XRD外推法測(cè)定了SnO_2在r-TiO_2和a-TiO_2上的單層分散閾值分別為0.610 mmol/(100 m~2 r-Ti O_2)和0.232mmol/(100 m~2 a-TiO_2)。顯然,通過(guò)不同制備方法所測(cè)得的分散閾值在誤差范圍內(nèi)一致,進(jìn)一步驗(yàn)證了“相似相分散”現(xiàn)象的存在。由H_2-TPR結(jié)果可知SnO_2在兩種晶型載體上還原性能不同,SnO_2負(fù)載在r-TiO_2上一步還原,在a-TiO_2上卻分兩步還原;且SnO_2負(fù)載在r-TiO_2上時(shí)具有更高的CO催化氧化活性。表明TiO_2載體晶型不同,與被負(fù)載的SnO_2相互作用不同,可影響所得催化劑的結(jié)構(gòu)和催化活性。為了進(jìn)一步探究相似相分散的普遍性,考察了金紅石型結(jié)構(gòu)的RuO_2在r-TiO_2和a-TiO_2載體上的分散性能。采用浸漬法制備出一系列不同RuO_2負(fù)載量的n%RuO_2/a-TiO_2和n%RuO_2/r-TiO_2催化劑,分別通過(guò)XRD和Raman測(cè)定了RuO_2在a-TiO_2和r-Ti O_2上的單層分散閾值,為0.112 mmol/(100 m~2 a-TiO_2)和0.557 mmol/(100 m~2 r-TiO_2)。這一結(jié)果進(jìn)一步表明被負(fù)載的金屬氧化物與載體金屬氧化物具有相同晶型時(shí)更有利于其分散,證實(shí)了“相似相分散”現(xiàn)象存在的普遍性。這一現(xiàn)象的發(fā)現(xiàn)對(duì)有效設(shè)計(jì)高性能催化劑提供了新的思路�；谙嗨葡喾稚⒃�,設(shè)計(jì)制備了2 wt%Ru含量的RuO_2/a-TiO_2和RuO_2/r-TiO_2催化劑。發(fā)現(xiàn)RuO_2負(fù)載在相同晶型的r-TiO_2載體上所得催化劑其CO活性遠(yuǎn)遠(yuǎn)高于RuO_2/a-TiO_2催化劑。H_2-TPD、H_2-TPR、XPS和Raman等表征結(jié)果表明,因金紅石型RuO_2與載體r-TiO_2晶型相同,RuO_2/r-TiO_2催化劑中RuO_2有更高的分散度,二者間相互作用更強(qiáng),且表面存在更多活潑氧物種,導(dǎo)致其活性遠(yuǎn)遠(yuǎn)高于RuO_2/a-TiO_2催化劑。
[Abstract]:Monolayer dispersion theory suggests that salts and metal oxides can spontaneously disperse into submonolayer or monolayer structure on the surface of the carrier and have monolayer dispersion threshold. This theory has been widely accepted and provides an important basis for the effective design of high performance catalysts. Based on the monolayer dispersion theory, the dispersion and catalytic properties of the same metal oxide loaded on the same metal oxide in the same rutile type r-TiO2 with the same chemical composition, different crystal structure and anatase type a-TiO2TiO2 have been investigated. It is the same as rutile TiO_2 crystal. A series of nSnOs with different SnO_2 loads were prepared by physical mixing method. A series of nSnOs / s / 2r-TiOs / 2nSnOs / 2nTiO2and n%SnO_2/P25 catalysts were prepared. By XRD extrapolation, the monolayer dispersion thresholds of SnO_2 on r-TiO2tia-TiO2 and P25 were determined to be 0.559 mmol/(100 m2r-TiO2o0.229 mmol/(100 m2a-TiO2 and 0.305 mmol/(100m~2 P25O2, respectively. The results show that the supported metal oxide is more favorable to the dispersion of the loaded component when the crystal structure of the supported metal oxide is the same as that of the carrier metal oxide. Similar to the principle of "similar phase dissolving", we have discovered the phenomenon of "similar phase dispersion" for the first time. In order to verify the phenomenon of "similar phase dispersion", a series of n%SnO_2/r-TiO_2 and n%SnO_2/a-TiO_2 catalysts with different SnO_2 loading amounts were prepared by means of deposition precipitation method. The monolayer dispersion thresholds of SnO_2 on r-TiO_2 and a-TiO_2 were determined to be 0.610 mmol/(100 mt2r-Ti O 2 and 0.232mmol/(100 mc2a-TiO2T respectively by XRD extrapolation. It is obvious that the dispersion threshold measured by different preparation methods is consistent within the error range, which further verifies the existence of the phenomenon of "similar phase dispersion". The results of H_2-TPR show that the reduction performance of SnO_2 on two kinds of crystal supports is different. Sno _ 2 supports are reduced in one step on r-TiO_2, but they are reduced in two steps on a-TiO_2, and SnO_2 supports on r-TiO_2 have higher catalytic activity for CO oxidation. The results showed that the structure and catalytic activity of the catalyst were affected by the different crystal type of TiO_2 support and the interaction with the supported SnO_2. In order to further explore the universality of similar phase dispersion, the dispersion properties of rutile RuO_2 on r-TiO_2 and a-TiO_2 carriers were investigated. A series of n%RuO_2/a-TiO_2 and n%RuO_2/r-TiO_2 catalysts with different RuO_2 loading amounts were prepared by impregnation method. The monolayer dispersion thresholds of RuO_2 on a-TiO_2 and r-Ti O _ 2 were determined by XRD and Raman, respectively. The thresholds of RuO_2 dispersion on a-TiO_2 and r-Ti O _ (2) were 0.112 mmol/(100 mf2a-TiO2) and 0.557 mmol/(100 mr-TiO2 respectively. The results further show that the supported metal oxides have the same crystal form as the carrier metal oxides are more favorable for their dispersion, which confirms the universality of the phenomenon of "similar phase dispersion". The discovery of this phenomenon provides a new idea for the effective design of high performance catalysts. Based on the principle of similar phase dispersion, RuO_2/a-TiO_2 and RuO_2/r-TiO_2 catalysts with 2 wt%Ru content were designed and prepared. It was found that the CO activity of the catalyst supported on the same crystal type of r-TiO_2 was much higher than that of RuO_2/a-TiO_2 catalyst. H2-TPD-H2-TPRO and Raman. The results showed that the dispersion of RuO_2 in the rutile RuO_2 was higher than that in the support r-TiO_2, because the rutile RuO_2 had the same crystal form as r-TiO_2. The interaction between them is stronger and there are more active oxygen species on the surface, which leads to their activity being much higher than that of RuO_2/a-TiO_2 catalyst.
【學(xué)位授予單位】：南昌大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：O643.36

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