Aerobic selective oxidation of allylic aldehydes offers an atom and energy efficient route to unsaturated carboxylic acids, however suitable heterogeneous catalysts offering high selectivity and productivity have to date proved elusive. Herein, we demonstrate the direct aerobic oxidation of cinnamaldehyde to cinnamic acid employing silica supported Pt nanoparticles under base-free, batch and continuous flow operation. Surface and bulk characterisation of four families of related Pt/silica catalysts by XRD, XPS, HRTEM, CO chemisorption and N₂ porosimetry evidence surface PtO₂ as the common active site for cinnamaldehyde oxidation, with a common turnover frequency of 49,000 ± 600 h⁻¹; competing cinnamaldehyde hydrogenolysis is favoured over metallic Pt. High area mesoporous (SBA-15 or KIT-6) and macroporous-mesoporous SBA-15 silicas confer significant rate and cinnamic acid yield enhancements versus low area fumed silica, due to superior platinum dispersion. High oxygen partial pressures and continuous flow operation stabilise PtO₂ active sites against in-situ reduction and concomitant deactivation, further enhancing cinnamic acid productivity.

烯丙基醛的有氧选择性氧化提供了一种不饱和羧酸的原子和能量有效途径，但是迄今为止，提供高选择性和高生产率的合适多相催化剂已被证明是可望而不可及的。在本文中，我们证明了在无碱，分批和连续流动操作下，采用二氧化硅负载的Pt纳米颗粒将肉桂醛直接好氧氧化为肉桂酸。表面，并通过XRD，XPS，HRTEM，CO化学吸附和N四个家族相关的Pt /二氧化硅催化剂中的散装表征₂孔隙率法证据表面的PtO ₂作为共同的活性位点为肉桂醛氧化，具有49000±600 h的共同周转频率^{- 1个}; 竞争性肉桂醛氢解比金属铂更受青睐。高面积的中孔（SBA-15或KIT-6）和大孔的中孔SBA-15二氧化硅由于具有优异的铂分散性，与低面积的气相法二氧化硅相比，具有显着的产率提高和肉桂酸收率的提高。高氧分压和连续流动操作可稳定PtO ₂活性位点，防止其原位还原和随之而来的失活，从而进一步提高了肉桂酸的生产率。