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采用原位Raman光谱技术,在原料气中的O2未完全耗尽的条件下,对CH4部分氧化制合成气反应的Rh/SiO2催化剂床层前部贵金属物种的化学态以及由CH4解离所生成的碳物种进行了表征.在此基础上采用脉冲反应和同位素示踪技术,比较了CH4的部分氧化及其与H2O和CO2的重整等反应对催化剂床层氧化区内CO和H2生成的相对贡献,并将实验结果与Ra-man光谱表征结果进行了关联.结果表明,在600°C下将还原后的4%Rh/SiO2催化剂切入CH4:O2:Ar=2:1:45原料气,催化剂床层前部未检测到铑氧化物的Raman谱峰,但可清晰检测到源于CH4解离的碳物种;在700°C和接触时间小于1ms的条件下,催化剂床层的氧化区内已有大量CO和H2生成,在相同的实验条件下,CH4与H2O或CO2重整反应对氧化区内合成气生成的贡献则很小;以CH4:16O2:H218O:He=2:1:2:95为原料气的同位素示踪实验结果表明,在原料气中16O2未完全耗尽的情况下,反应产物中C16O的含量占CO生成总量的92.3%,表明CO主要来自CH4的部分氧化反应.上述结果均表明,在O2存在下Rh/SiO2催化剂上CO和H2可以通过CH4直接解离和部分氧化机理生成.
The in situ Raman spectroscopy is used to study the chemical state of the noble metal species in front of the Rh / SiO2 catalyst bed reacting with partial oxidation of CH4 to syngas and the dissociation of CH4 under the condition of incomplete depletion of O2 in the feed gas Of carbon species were characterized by means of pulse reaction and isotope tracing techniques.The relative partial oxidation of CH4 and its reaction with H2O and CO2 for the formation of CO and H2 in the oxidation zone of the catalyst bed were compared And the experimental results were correlated with the Ra-man spectral characterization results.The results showed that the 4% Rh / SiO2 catalyst was cut into the CH4: O2: Ar = 2: 1: 45 feed gas at 600 ° C, The Raman peak of the rhodium oxide was not detected in the front of the catalyst bed, but the carbon species from the CH4 dissociation could be clearly detected. Under the conditions of 700 ° C and the contact time of less than 1ms, the oxidation of the catalyst bed A large amount of CO and H2 have been generated. Under the same experimental conditions, the contribution of CH4 and H2O or CO2 reforming reaction to the formation of syngas in the oxidation zone is very small. Taking CH4: 16O2: H218O: He = 2: 1: 2 : 95 as the raw material gas isotope tracer experiments show that in the raw material gas 16O2 not completely depleted circumstances, The content of C16O in the product should account for 92.3% of the total CO formation, indicating that the CO mainly comes from the partial oxidation of CH4.The above results indicate that both CO and H2 can be directly dissociated by CH4 and part of Oxidation mechanism generated.