Revealing the unexpected promotion effect of EuO_x on Pt/CeO_2 catalysts for catalytic combustion of toluene

Pt/Eu2O3-CeO2 materials with different Eu concentrations were prepared and applied to toluene destruction,and the remarkable promotion impact of EuOx on Pt/CeO2 can be observed.The characterization results reveal that the presence of EuOx significantly enhances the redox property,lattice O concentration,and Ce3+ ratio of the Pt/CeO2 material,which facilitates the dispersion and activity of Pt active sites and thus accelerates the decomposition process of toluene.Among all catalysts,a sample with an Eu content of 2.5 at.%(Pt/EC-2.5)possesses the best catalytic activity with 0.09 vol% of toluene completely destructed at 200 ℃ under a relatively high GHSV of 50000 h^-1.The possible reaction pathway and mechanism of toluene combustion over Pt/Eu2O3-CeO2 samples are presented according to in-situ DRIFTS,which confirms that the toluene oxidation process obeys the Mars-van Krevelen mechanism with aldehydes and ketones as primary organic intermediates.

Influence of Dechlorination Temperature on Propane Dehydrogenation over Pt-θ-Al2O3

Several Pt-θ-Al_2O_3 catalysts with similar ultra-low Cl contents were used to investigate the influence of dechlorination temperature on propane dehydrogenation reaction. The Pt-θ-Al_2O_3 catalyst treated at a highest dechlorination temperature showed a lowest propane rate and propylene selectivity. The scanning transmission electron microscopy showed that the dispersions of Pt nanoparticles decreased with an increasing dechlorination temperature. The temperature-programmed reduction analysis showed that higher dechlorination temperature could lead to strong interactions between the metal and support, making it difficult to reduce Pt nanoparticles. The temperature-programmed oxidation analysis implied that more coke was deposited on the metal for catalyst treated at higher dechlorination temperature. The Raman spectra and the H/C ratio showed that more side-reactions, such as cracking and severe deep dehydrogenation reactions, occurred on catalysts treated at higher dechlorination temperatures. Therefore, the lower the dispersion of Pt nanoparticles was, the stronger the metal-support interactions and increased side-reactions would be, resulting in lower catalytic activity for Pt-θ-Al_2O_3 treated with higher dechlorination temperature.

Effect of Precursor Mechanism on CO-NO Catalytic Reaction on Body-Centred Cubic Structure： Monte Carlo Simulation

The CO-NO catalytic reaction on body-centred cubic （bcc） lattice is studied by Monte Carlo simulation. The simple Langmuir-Hinshelwood （LH） mechanism yields a steady reactive window, which is separated by continuous and discontinuous irreversible phase transitions. The effect of precursor mechanism on the phase diagram of the system is also studied. According to this mechanism, the precursor motion of CO molecules is considered only on the surface of bcc lattice. Some interesting observations are reported.

非恒温CO表面催化氧化体系双随机共振

当考虑化学反应热、热传导和热辐射的影响时,Pt(110)/CO+O2表面催化氧化体系温度出现时空变化.以衬底温度为控制参数,通过计算机模拟,研究了衬底温度噪声对该非恒温表面反应体系振荡动力学行为的影响.研究发现,温度噪声可以诱导体系双随机共振现象,而且增大衬底温度可以使体系共振行为由双随机共振变为单随机共振.这表明体系可以利用温度噪声加强其反应振荡,并对其具有双重选择性,人们可以通过改变衬底温度大小来控制体系的共振行为.

三种用于水氢交换的Pt/疏水陶瓷催化剂

研究选用了三种不同的疏水陶瓷载体(其主要原料分别为ZrO2、SiO2及SiC),采用浸渍还原法,制得了用于水氢同位素交换分离的Pt/疏水陶瓷催化剂。研究通过XRD、SEM、压汞仪及化学吸附仪等对载体及制得的催化剂进行表征,采用气汽并流方式测得催化剂交换效率,考察此三种由不同原料烧制的陶瓷载体对制得催化剂的影响。研究结果表明,以ZrO2为原料制得的陶瓷载体,载体结构适宜且稳定性好,最适宜作为载体制备催化剂。制得的催化剂在0.1 m/s气速下其催化交换效率可达31.2%,冲淋4周后催化剂活性几乎无变化。

载体预处理对用于水氢交换Pt/疏水陶瓷催化剂的性能影响

研究分别采用HNO3及HCl对载体进行预处理,而后通过浸渍及气相还原后,获得铂(Pt)/疏水陶瓷催化剂。通过SEM、压汞仪、XRD、IR及化学吸附仪等对预处理前后载体及制得催化剂的性能进行表征,通过气汽并流测试催化活性,考察载体预处理对制得催化剂的影响。研究结果表明,载体经HNO3及HCl预处理后,比表面积均有所提升,利于制得催化剂铂粒子分散度及其催化活性的提高。此外,采用HNO3预处理可在载体表面引入-NO3基团,可破坏铂结晶完善度,进一步提升铂粒子分散度,使得制得的催化剂性能优于采用HCl预处理载体制得的催化剂。HNO3预处理载体制得催化剂的催化交换效率在0.1 m/s气速下可达到33.1%,较未处理前的26.2%有明显提升。

Stochastic resonance in surface catalytic oxidation of carbon monoxide induced by colored noise

The dynamical behavior of surface catalytic oxidation reaction of Pt(110)/CO+O2 modulated by colored noise, under the condition of specific temperature, has been investigated when the partial pressure of CO gas is near the supercritical Hopf bifurcation point. By computer simulation the oscillation and stochastic resonance induced by colored noise are observed. The influences of the intensity and correlation time of colored noise on stochastic resonance are discussed. The range of sensitivity of the system to the environmental fluctuation is analyzed.

色噪声作用下一氧化碳表面催化氧化反应体系的随机共振

研究了Pt(110)/CO+O_2表面催化氧化反应体系在一定温度条件下,当CO气体偏压P_u在超临界Hopf分岔点附近被色噪声调制后的动力学行为。通过计算机模拟观察到色噪声诱导的振荡和随机共振(stochastic resonance)现象,探讨了色噪声强度和相关时间对随机共振行为的影响,分析了体系对环境涨落的敏感性范围。