Development of Phototalytic Process for Selective Oxidation of Alkansor

在V_2O_5/SiO_2中加入碱金属离子，不仅提高了催化活性，而且改变了λ>400 nm光激发的有效波长。研究了异丁烷光氧化反应中表面物种与Rb离子相互作用的反应性，以阐明烷烃光氧化反应的机理。生成丙酮和C_4-化合物。最引人注目的是在Rb^+改性的催化剂上叔丁醇的形成。用^ O_2作示踪剂的研究<18>表明，叔丁醇中的氧原子来自气态氧，而丙酮中的^<16>O则来自催化剂中的晶格氧。对活性组分进行了量子化学计算，发现碱金属离子掺杂和未掺杂样品中激发态空穴的位置不同，这与激发能的不同有关。对连续流动反应器进行氧化系统测试。转化率为1.2%，丙酮的选择性为70%。催化剂失活持续8小时。

The addition of alkali ions to V_2O_5/SiO_2 enhances catalytic activity as well as changes the effective wavelengh ; excited by irradiation with the light lambda>400 nm. The reactivity of the surface species interacting with Rb ions in the photo-oxidation of isobutane has been investigated to clarify the mechanism of photooxidation of alkanes. Acetone and C_4-compounds were formed. The most striking point is the formation of tert-butyl alcohol over the Rb^+-modified catalyst. A tracer study with ^<18>O_2 showed that oxygen atoms incorporated into tert-butyl alcohol were from gaseous oxygen, whereas acetone contained ^<16>O which originated from the lattice oxygen in the catalyst. The quantum chemical calculations of the active species were carried out and we found that the position of the excited positive hole is different between alkali-ion-doped and undoped samples, which corresponds to the difference of excitation energy. The continuous flow reactor was tested for the oxidation system. The conversion was 1.2% and the selectivity to acetone was found to be 70%. The catalyst deactivation could not be seen for 8-hours duration.