| Ethylene and acetylene coming from oil are important raw materials of chemical industry. Oil is getting less and less. Natural gas is abundant in the world and its main ingredient is methane. Converting methane into ethylene and acetylene is a prospective way of methane conversion. The traditional method of methane conversion into acetylene needs high temperature (1200~1400K) and high energy expense, so it is not beneficial for industry production. Today, methane conversion into C2 hydrocarbons under plasma is widely studied all over the world. Because of obvious superiority of microwave plasma, so it will give a new way of natural gas utilization.This paper has two parts: (1) methane coupling under microwave plasma catalysis, (2) acetylene conversion into ethylene under conventional method.1. methane coupling under microwave plasma catalysismethane coupling under microwave plasma has been studied in a multi-mode resonator with unadjustable power and a single-mode resonator with adjustable power. The multi-mode resonator is reequipped with 600 domestic microwave oven. The single-mode resonator is made by national key laboratory of millimeter waves of Southeast University, in pure methane, plasma only can be induced at very low pressure under microwave field. The reaction volume of feed gas is small and the additional dynamic expense is needed, so it has no industry prospect. Therefore, enhancing the pressure of plasma inducing and realizing methane coupling at normal pressure is our aim. So catalyst and initiator are used to enhancing reaction pressure, and H2 is also added to make reaction pressure up to normal pressure, the reaction property of methane coupling has been studied at low pressure and normal pressure. And at the same time, reaction conditions(example for catalyst kinds and component, microwave irradiation time, system pressure, feed gas volume and component, et al) have been studied and sifted. The results show, in multi-mode resonator, at low pressure, when the feed gas pure methane, Fe-Ni is the better catalyst in methane coupling at non-oxidativeAbstractatmosphere, but the action on inducing plasma is limited. Inserting a initiator can increase at least 10 times in discharge pressure. But the high energy induced by initiator may lead to deeply pyrolysis of methane and carbon deposition is serious, all this prevents continuous reaction. Adding H2 into methane system not only can enhance reaction pressure up to normal pressure, but also can prohibit carbon deposition efficiently. In addition, that should be pointed out is at high power multi-mode resonator, acetylene is the only product of methane coupling in Ci hydrocarbons. At normal pressure, when the feed gas is the mixture of H2/CH4, the result under the optimal condition is: methane conversion 83.9% and acetylene yield 65.9%.In single-mode resonator, using similar reaction condition in multi-mode resonator at normal pressure, the plasma can maintain (that also means the reaction can maintain) above 30min. this has significance to the industrialization of methane coupling. Moreover, in single-mode resonator, carbon deposition is little, the products include acetylene and ethylene. The result under the optimal condition is: methane conversion 64.0%, acetylene yield 52.0% and ethylene yield 12.0%. the best results in single-mode resonator multi-mode resonator are better than the best result in papers so far (methane conversion 59.2%, C2 yield 52.0%).2. acetylene conversion into ethylene under conventional methodthe product or main product of methane coupling under plasma is acetylene and our ultimate purpose is converting methane into ethylene, so making the products of methane coupling convert into ethylene is also to be studied in this paper. In the follow, the reaction property of acetylene hydrogenation has been studied over 12%Ni/CNTs, 5 %oPd/y-Al2O3 and 5%oPd/CNTs. And at the same time, reaction conditions (example for temperature, the feed gas component at normal pressure reaction) have been studied and sifted. The results... |
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