Acid site densities and reactivity of oxygen-modified transition metal carbide catalysts
Acid site densities and reactivity of oxygen-modified transition metal carbide catalysts
复制标题
氧改性过渡金属碳化物催化剂的酸位密度和反应活性
DOI：
10.1016/j.jcat.2016.09.012
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发表时间：
2016
影响因子：
7.3
通讯作者：
A. Bhan
中科院分区：
文献类型：
--
作者：
Mark M. Sullivan;A. Bhan
通过评估异丙醇（IPA）在415 K下（i）在惰性He/Ar气氛下或（ii）在13 kPa O2共进料下脱水的动力学来量化β-Mo 2C、α-Mo 2C、W2 C和WC的酸性。脱水动力学是零级相对于IPA的所有催化剂和在所有的反应条件下。所有催化剂的固有活化能相似（89-104 kJ mol−1）。通过原位2，6-二叔丁基吡啶（DTBP）滴定计算的酸位点密度用于归一化脱水转换频率（TOF）。O2共同饲料增加脱水率每克由一个数量级的所有催化剂测试，但TOF保持不变的一个因素的0.02。Mo和W基碳化物表现出类似的脱水动力学，无论O2共同饲料，和O2共同饲料没有改变散装碳化物结构所指出的X-射线衍射。布朗斯特酸位来源于Mo和W碳化物的亲氧性。
Acidic properties of β-Mo2C, α-Mo2C, W2C, and WC were quantified by assessing the kinetics of isopropanol (IPA) dehydration at 415 K either (i) under inert He/Ar atmosphere or (ii) with 13 kPa O2co-feed. Dehydration kinetics were zero-order with respect to IPA for all catalysts and under all reaction conditions. Intrinsic activation energies were similar across all catalysts (89–104 kJ mol−1). Acid site densities calculated via in situ 2,6-di-tert-butylpyridine (DTBP) titration were used to normalize dehydration turnover frequencies (TOF). O2co-feed increased dehydration rates per gram by an order of magnitude for all catalysts tested, but TOF remained invariant within a factor of ∼2. Mo- and W-based carbides showed similar dehydration kinetics regardless of O2co-feed, and O2co-feed did not alter bulk carbidic structure as noted by X-ray diffraction. Brønsted acid site provenance results from the oxophilicity of Mo and W carbides.