Study On The Catalytic Reforming Of Ethane In Short Contact Time

The chemical raw materials such as Hydrogen (H₂), ethylene (C₂H₄), synthesis gas (CO and H₂ mixture), and ect play an important role in industrial production and energy area. Catalytic reforming of hydrocarbons is one of the important ways to obtain hydrogen, synthesis gas and ethylene important. Except methane, natural gas also contains ethane, propane and other hydrocarbon compounds mixed gas, therefore, catalytic reforming of ethane is an important supplement in catalytic reforming of natural gas technology.This thesis make deep research on catalytic reforming of ethane with Short-Contact-Time-Reforming technology, the mian results and conclusions are as followed:1 The Pt-SCTR was studied. By controlling the C₂H₆/O₂, N₂ dilution and the total flow rate (residual time), the effect of Pt-SCTR was studied.The result proved that: C₂H₆/O₂ was the key point and when the rate of C₂H₆/O₂ was low, the selectivity of synthesis gas increased, and otherwise, the selectivity decreased. N₂ dilution is mostly affect the temperature of the reactor and indirectly made influence on the Homogeneous and Heterogeneous Contributions. When the N₂-dilution increased, the selectivity of C₂H₄ increased.Temperature showed its power by two means: firstly on catalytic partial oxidation; secondly on catalytic stream-reforming and CO2-reforming.But as both of the stream-reforming and CO2 reformings are endothermic reaction. So they are more sensitive on the change of temperature. Changing flow rate means different contact time and temperature. When the C₂H₆/O₂=2 and 60%N₂ dilution, the selectivity of synthesis gas get the climax at 4SLPM (CO: 70%; H₂: 40%). And another simple way to change the temperature is preheating, which can promote the oxidation of C₂H₄ and produce C₂H₂, CH₄, H₂ and CO. To sum it up, Pt-SCTR can be applied to an indirect reaction model of which in the first zone C₂H₆ was totally or partially oxidized ; in the second zone more stream-reforming or CO2-reforming can be seen.2 The Rh-SCTR was studied. To do the deep research on Rh-SCTR, we have more clear understanding on the character and mechanics of SCTR.Homogeneous reaction cannot be ignored in the SCTR, and the two main Homogeneous reactions are C₂H₆ dehydrogenation to produce synthesis gas and C₂H₆ partial oxidation to produce C₂H₄. The degree of these two reactions mainly related to C₂H₆/O₂ and temperature. At different C₂H₆/O₂, N₂ dilution and flow rate, Rh and Pt have the similar tendency because both of them are precious metal and the production of C₂H₄, C₂H₂ and synthesis gas mainly come from Homogeneous reaction. But it is obvious that Rh has higher selectivity of CO and H₂, lower convention of C₂H₆ and O2, lower selectivity of C₂H₄, C₂H₂ and CH₄.So we can produce more synthesis gas using less CH and O2. The most important difference of Rh and Pt is lied on the surface of the catalyst .Rh is not likely to eliminateβ-H, so the active particles can easily be oxidized to synthesis gas.what's more, because the energy and temperature are very high. These active particles and some other CH can react with stream on the surface of catalyst to produce more synthesis gas.3 The LaMnO₃-SCTR was studied. As the effect of Homogeneous reaction is very important, LaMnO₃-SCTR is also some kind of similar as the precious metal (Pt /Rh). But LaMnO₃ is more active in the ignition and produced more CH₄. So the selectivity of CH₄ is more stable when the temperature changed .And the climax of temperature of LaMnO₃-SCTR was detected at the back of the catalytic bed(>20mm), comparing with the middle(10mm²0mm) of the catalyst in precious metal. That means apart from ignition, precious metal catalyst offered more Heterogeneous Contributions than LaMnO₃ in SCTR. And LaMnO₃ is weak in Heterogeneous dehydrogenation but active at ignition. And if we increase the loading of the catalyst, the temperature can be higher. To sum it up, LaMnO₃ is relatively active because the convention of C₂H₆ is more than 70% percent. And it must be pointed out that although under long-time high temperature environment, LaMnO₃ can still be active. So it's reasonable to believe LaMnO₃ has a great future.Under all of these experiment and statistics, we have deeper understanding about the character and mechanics of SCTR, which can provide important theoretic basis for this technology.