Insight into the structure and molybdenum species in mesoporous molybdena-alumina catalysts for isobutane dehydrogenation
Insight into the structure and molybdenum species in mesoporous molybdena-alumina catalysts for isobutane dehydrogenation
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深入了解用于异丁烷脱氢的介孔钼-氧化铝催化剂的结构和钼种类
DOI：
10.1039/c7cy00975e
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发表时间：
2017
影响因子：
5
通讯作者：
Yan Liang
中科院分区：
文献类型：
--
作者：
Zhao Huahua;Song Huanling;Chou Lingjun;Zhao Jun;Yang Jian;Yan Liang
研究了介孔氧化铝-氧化铝催化剂的结构、钼物种与异丁烷脱氢反应性能的关系。XRD、HAADF-STEM、EDX、FT-IR和N2物理吸附等表征表明，有序介孔催化剂（OM-Al、MoAl（F）和MoAl（C））为无定形氧化铝相，无序介孔催化剂（M-Al和MoAl）为γ-Al 2 O3相。Mo物种高度分散在所有催化剂上，因为Mo表面密度约为1.0 Mo nm-2。XPS和ICP-OES结果表明，Mo物种均匀分布在MoAl（F）上，并被限制在有序的介孔结构中。H_2-TPR结果表明，与MoAl（C）和MoAl相比，MoAl（F）具有更强的金属-载体相互作用，具有更高的脱氢稳定性和更低的焦炭生成速率，但催化转化率较低。结果表明，γ-Al_2O_3相催化剂比非晶相催化剂具有更强的酸性和更高的活性。NH_3-TPD表征结果表明，Mo的加入大大提高了催化剂的酸性。然而，并不是所有的酸位点都是脱氢活性的活性位点。中等和强酸性的网站和钼物种，包括Mo 6+和低价钼物种，可能有助于脱氢反应。此外，失活的催化剂主要是由于焦炭形成的废催化剂。
The relationship between the structure and Mo species in mesoporous molybdena–alumina catalysts and their catalytic performance for isobutane dehydrogenation has been investigated in detail. Characterization by XRD, HAADF-STEM, EDX, FT-IR, and N2 physisorption illustrated that ordered mesoporous catalysts (OM-Al, MoAl(F), and MoAl(C)) possessed an amorphous alumina phase and non-ordered mesoporous catalysts (M-Al and MoAl) exhibited a γ-Al2O3 phase. Mo species were highly dispersed over all the catalysts because Mo surface densities were about 1.0 Mo nm−2. Moreover, XPS and ICP-OES showed that Mo species were uniformly distributed over MoAl(F) with the Mo species confined in the ordered mesoporous structure. Higher dehydrogenation stability and a lower coke formation rate, albeit lower catalytic conversion, was obtained over MoAl(F) in comparison with those of MoAl(C) and MoAl on account of its stronger metal–support interaction, as shown by H2-TPR technique. The catalyst with a γ-Al2O3 phase exhibited stronger acidity and higher activity than the corresponding catalyst with an amorphous phase. The acidity of the catalysts was greatly enhanced by the addition of Mo species, according to the NH3-TPD characterization. However, not all the acid sites were active sites for dehydrogenation activity. The moderately and strongly acidic sites and the Mo species, including Mo6+ and lower valence Mo species, probably contributed to the dehydrogenation reactivity. Moreover, deactivation of the catalysts was mainly due to coke formation over the spent catalysts.