A set of vanadium phosphorous oxide (VPO) catalysts, mainly consisting of (VO)₂P₂O₇, VO(PO₃)₂ or VOPO₄·2H₂O bulk crystalline phases, has been investigated for the oxidative dehydrogenation (ODH) of ethane to ethylene, a key potential reaction for a sustainable industrial and socioeconomic development. The catalytic performance on these VPO catalysts has been explained on the basis of the main crystalline phases and the corresponding surface features found by XPS and LEISS at 400 °C, i.e. within the temperature range used for ODH reaction. The catalysts based on (VO)₂P₂O₇ phase presented the highest catalytic activity and productivity to ethylene. Nevertheless, the catalysts consisting of VO(PO₃)₂ structure showed higher selectivity to ethylene, reaching 90% selectivity at ca. 10% ethane conversion. To the best of our knowledge, this is the highest selectivity reported on a vanadium phosphorous oxide at similar conversions for the ethane ODH. In general, catalysts consisting of crystalline phases with vanadium present as V⁴⁺, i.e. (VO)₂P₂O₇ and VO(PO₃)_2, were found to be significantly more selective to ethylene than those containing V⁵⁺ phases. The surface analysis by XPS showed an inverse correlation between the mean oxidation state of vanadium near surface and the selectivity to ethylene. The lower averaged oxidation states of vanadium appear to be favoured by the presence of V³⁺ species near the surface, which was only found in the catalysts containing V⁴⁺ phases. Among those catalysts the one based on VO(PO₃)₂ phase shows the highest selectivity, which could be related to the most isolated scenario of V species (the lowest V content relative to P) found at the outermost surface by low energy ion scattering spectroscopy (LEISS), a “true” surface technique only sensitive to the outermost atomic layer.

已经研究了一组主要由（VO）₂ P ₂ O ₇，VO（PO ₃）₂或VOPO ₄ ·2H ₂ O本体结晶相组成的钒磷氧化物（VPO）催化剂用于氧化脱氢（ODH）乙烷转化为乙烯，这是可持续的工业和社会经济发展的关键潜在反应。已基于XPS和LEISS在400°C（即用于ODH反应的温度范围内）发现的主要晶相和相应的表面特征，说明了这些VPO催化剂的催化性能。基于（VO）₂ P ₂ O的催化剂_7相对乙烯具有最高的催化活性和生产率。然而，由VO（PO ₃）₂结构组成的催化剂显示出对乙烯的更高选择性，在约90℃下达到90％的选择性。10％的乙烷转化率。据我们所知，这是钒氧化磷在乙烷ODH的相似转化率下报道的最高选择性。通常，发现由以V ^4+形式存在的钒（即（VO）₂ P ₂ O ₇和VO（PO ₃）₂）形式的钒组成的催化剂比含有V ^5+的催化剂对乙烯的选择性更高。阶段。XPS的表面分析表明，钒在表面附近的平均氧化态与对乙烯的选择性成反比。钒的较低平均氧化态似乎是由于表面附近存在V ³⁺物种而受到促进的，这仅在含有V ⁴⁺相的催化剂中才发现。在这些催化剂中，一种基于VO（PO ₃）_2的催化剂显示出最高的选择性，这可能与通过低能离子散射在最外层表面发现的V物种最孤立的情况（相对于P的V含量最低）有关。光谱法（LEISS），一种仅对最外层原子层敏感的“真实”表面技术。