为提高SO_4^(2-)/TiO_2固体超强酸的稳定性,向TiO_2载体中引入Ba制备成SO_4^(2-)/Ba-TiO_2复合固体超强酸,并采用X-射线粉末衍射(XRD)、比表面积分析(BET)、傅里叶变换红外光谱(FT-IR)、程序升温吸附氨脱附(NH3-TPD)等表征方法对其比表面积、晶相、硫质量分数、酸强度等进行分析。结果表明,Ba与TiO_2间会形成Ba Ti O3相,导致SO_4^(2-)/Ba-TiO_2固体超强酸的孔结构发生一定程度的坍塌;另外,FT-IR分析结果显示,在SO_4^(2-)/Ba-TiO_2固体超强酸中出现新的SO基团振动,说明形成了新的酸中心结构;而NH3-TPD结果表明,引入Ba并没有改变固体超强酸的酸强度和酸量。乙酸-正丁醇酯化反应结果显示,在103℃、酸醇摩尔比1∶1、催化剂用量0.5 g条件下,SO_4^(2-)/Ba-TiO_2的正丁醇转化率略低于SO_4^(2-)/TiO_2;但经过水预处理后,SO_4^(2-)/Ba-TiO_2呈现较高的正丁醇转化率,说明引入Ba在一定程度上提高了固体超强酸的稳定性。研究结果可为固体超强酸的工业化应用提供技术基础。
Black TiO2（B）/anatase bicrystalline TiO2-x nanofibers were synthesized from a porous titanate derivative by calcination in H2, and were characterized using field-emission scanning electron microscopy, Raman spectroscopy, N2 adsorption-desorption analysis, X-ray photoelectron spectroscopy, thermogravimetric analysis, ultraviolet-visible diffuse reflection spectroscopy and photoluminescence measurements. Characterization results showed that no Ti3＋ was present on the surface of black bicrystalline TiO2-x and oxygen vacancies were distributed in the bulk of both TiO2（B） and anatase phases. The O/Ti atom stoichiometric ratio of black bicrystalline TiO2-x was estimated to be 1.97 from the difference of mass loss between black bicrystalline TiO2-x and white bicrystalline TiO2 without oxygen vacancies. The photocatalytic activity of black bicrystalline TiO2-x was 4.2 times higher than that of white bicrystalline TiO2 and 10.5 times higher than that of anatase TiOz. The high photocatalytic activity of black bicrystalline TiO2-x was attributed to its effective separation of electrons and holes, which may be related to the effects of both bicrystalline structure and oxygen vacancies. Black bicrystalline TiO2-x also exhibited good photocatalytic activity after recycling ten times. The black bicrystalline TiO2-x nanofibers show potential for use in environmental and energy applications.
