碱土金属氧化物改性ZrO2催化1,4-丁二醇选择性脱水合成3-丁烯-1-醇

采用浸渍法制备了碱土金属氧化物CaO,SrO或BaO改性的ZrO₂酸碱双功能催化剂,借助X射线衍射、低温N₂物理吸附、NH₃和CO₂程序升温脱附等手段表征了催化剂的结构、织构以及表面酸碱性质,并考察了其催化1,4-丁二醇选择性脱水合成3-丁烯-1-醇的反应性能.结果表明,碱土金属氧化物的引入显著调变了催化剂表面的酸性和碱性中心,进而对1,4-丁二醇转化率和3-丁烯-1-醇选择性产生重要影响.其中,CaO改性的ZrO₂样品中形成了大量的Ca-O-Zr结构,在ZrO₂表面形成大量碱性位点的同时,保持了较高的酸密度;而SrO和BaO改性的样品中生成了相应的锆酸盐,ZrO₂表面的酸密度呈现不同程度的下降.因此,CaO/ZrO₂催化剂表现出最优的催化活性和3-丁烯-1-醇选择性,350℃时,3-丁烯-1-醇收率最高,达60.5%.催化剂表面的酸碱协同作用是选择性合成3-丁烯-1-醇的关键因素.

Vapor-phase selective dehydration of 1,4-butanediol to 3-buten-1-ol over ZrO2 catalysts modified with alkaline earth metal oxides

Modified ZrO₂ catalysts were prepared by doping with alkaline earth metal oxides (CaO, SrO, or BaO) in a wet impregnation method. The catalysts were characterized by N₂ physisorption, X-ray diffraction, and temperature-programmed desorption (TPD) with NH₃ and CO₂. Their catalytic performance in the vapor-phase selective dehydration of 1,4-butanediol (BDO) to 3-buten-1-ol (BTO) was investigated. The results showed that the alkaline earth metal can change the acid-base properties on the catalyst surface and thus affect BDO conversion and BTO product selectivity. For ZrO₂ catalyst modified by CaO, Ca²⁺ entered the ZrO₂ crystal lattice and formed Ca?O?Zr hetero-linkages. These allowed the CaO/ZrO₂ catalyst to maintain a high acid density and generate a large number of basic sites when compared with unmodified ZrO₂. In contrast, SrO and BaO reacted with ZrO₂ to generate the corresponding zirconates, which resulted in decreased acid density on the catalyst surface. Of the catalysts tested, CaO/ZrO₂ showed the best catalytic performance. The highest yield of BTO was 60.5% and was achieved at 350℃ over CaO/ZrO₂ catalyst. The key point for highly selective dehydration of BDO to BTO resided in the synergistic effect between acid and base sites on the catalyst surface.