ZrO2催化无溶剂条件下醇的液相氧化反应

采用一种环境友好的方法,以分子氧为氧化剂,以ZrO2为催化剂,在无溶剂的条件下实现了醇的选择性氧化.苯甲醛、环己酮和辛醛等是相应醇的主要氧化产物.考察了不同反应条件(搅拌速度、反应时间和温度)、催化剂制备参数(焙烧温度和负载量)及氧分压等的影响.结果发现,对于醇氧化生成相应羰基化合物,1 223 K焙烧的ZrO2比723 K焙烧的ZrO2显示出更高的催化活性.催化剂在反应混合物中不溶解,可以通过简单的过滤使其分离并重复使用.当搅拌速度大于900 r/min时,对醇的转化速率无明显的影响.     

The propagation of travelling waves in an open cubic autocatalytic chemical system

The reaction-diffusion travelling waves that can be initiatedin an open isothermal chemical system governed by cubic autocatalytickinetics are discussed. The system is shown to be capable ofsustaining up to three spatially uniform steady states, the(trivial) unreacted state, which is always stable (a node),and two nontrivial states, one of which is always unstable (asaddle point). The third state can change its stability throughHopf bifurcation (both subcritical and supercritical). Thisallows the possibility of two sorts of travelling wave beingestablished; there are wave profiles which connect the unreactedstate ahead to the nontrivial state at the rear, and wave profiles(pulse waves) which have the unreacted state at both the frontand rear. The conditions under which a particular wave is initiatedare considered by both a discussion of the (ordinary) differentialequations governing the travelling waves and by numerical integrationsof an initial-value problem. This treatment also reveals thepossibility of a stable travelling wave propagating throughthe system, leaving behind a temporally unstable stationarystate. Under these conditions, spatiotemporal chaotic behaviouris seen to develop after the passage of the wave.     

Kinetics of Heterogeneous Solvent‐free Liquid Phase Oxidation of Alcohol Using ZrO2 Catalyst with Molecular Oxygen

Clean liquid phase solvent‐free oxidation of alcohol to aldehyde/ketone using ZrO₂ catalyst with molecular oxygen has been studied. Monoclinic phase ZrO₂ has been synthesized and characterized by XRD, SEM, EDX and surface and pore size analyses. Oxidation of alcohol was carried out in a typical batch reactor at different speed of agitation (150–1200 r/min), temperature (373–413 K), catalyst loading (50–300 mg) and partial pressure of oxygen (12–101 kPa). These parameters influence alcohol conversion as well as selectivity. A handy touch of kinetics was given to the experimental data and apparent activation energy was calculated.