【摘要】 利用程序升温脱附、程序升温还原、程序升温表面反应、程序升温反应和化学捕获反应等手段 ,对Rh/SiO2 催化剂上甲烷部分氧化制合成气反应进行了研究 .结果表明 ,Rh/SiO2 催化剂上甲烷部分氧化制合成气机理属于热解 氧化反应机理 .甲烷首先在催化剂上发生解离吸附 ,产生具有不同H/C比的化学吸附物种CHx(x =1～ 3) .其中 ,具有较高H/C比的CHx 可能是甲烷部分氧化反应的活性物种 ,而具有较低H/C比的CHx 可能是催化剂上积碳并导致催化剂失活的来源 .活性物种CHx在活性氧物种的作用下 ,生成含氧中间体物种CHxO或继续脱氢 .含氧中间体物种进一步分解 ,即生成CO和H2 ;CO2 也可由CHx 或CHxO物种进一步氧化生成更多还原

【Abstract】 Partial oxidation of methane (POM) over Rh/SiO 2 catalyst was investigated by using several techniques, such as TPD, TPR, TPSR and trapping agent, combined with MS. At the beginning of POM reaction, only gaseous CO 2 can be detected over the catalyst. With the increase in space velocity, the conversion of CH 4 and the selectivity for CO and H 2 increase, while the selectivity for CO 2 decreases. During the pulse reaction with CH 4 as reactant, over the catalyst prereduced at 700 ℃, CO and H 2 can be detected as main products with trace C 2H 6 and C 2H 4. When the catalyst is exposed to CH 4 He, there are two kinds of carbonaceous species formed, and they are designated CH α and CH β , as identified by their hydrogenation temperature of 210～260 ℃ and 450～800 ℃, respectively. The CH α is assigned to H rich form and the CH β is assigned to H deficient form. When the catalyst is exposed to CH 4 O 2 He, the carbonaceous species are mainly CH α with trace CH β . The two kinds of carbonaceous species may play different roles in POM reaction. The CH β accumulated during CH 4 activation is the possible cause for catalyst deactivation, and the CH α may be responsible for CO formation. The CH x may be the intermediate of POM reaction. In the trapping reaction, a series of ions with M r/z =2～46 have been detected at 300～600 ℃. The CH x O ( x =1～3) may be the O containing intermediate of POM reaction. Based on the above results, the POM mechanism has been proposed. Over the reduced catalyst, CH 4 is firstly dissociated, forming the surface species CH x . By reacting with the active species OH -, the CH α is oxidized to O containing intermediate, CH x O, which can be dehydrogenated to give the adsorbed and gaseous CO.更多还原