Nitrogen oxide membrane reactor

Some dense inorganic membranes made of metals and metal oxides are oxygen specific. Notable ones include silver, zirconia stabilized by yttria or calcia, lead oxide, perovskite-type oxides and some mixed oxides such as yttria stabilized titania-zirconia. Their usage as a membrane reactor is profiled in Table 8.4 for a number of reactions decomposition of carbon dioxide to form carbon monoxide and oxygen, oxidation of ammonia to nitrogen and nitrous oxide, oxidation of methane to syngas and oxidative coupling of methane to form C2 hydrocarbons, and oxidation of other hydrocarbons such as ethylene, methanol, ethanol, propylene and butene. 

It is proposed to replace the conventional PER with a membrane reactor in order to impro e the selectivity. As a rule of thumb, a 19f increase in the selectivity to ethylene oxide translates to an increase in profit of about S2 mii-lion/yr. The feed consists of 12% (mole) oxygen. 69f ethylene, and the remainder nitrogen at a temperature of 250 C and a pressure of 2 atm. The total molar How rate is 0.0093 mol/s and to a reactor containing 2 kg of catalyst. 

The electrochemical membrane reactor utilizes platinized Nafion 117 as the PEM. It functions both as the electrolyte and separator. Hicks and Fedkiw [2.454] present results for the oxidation, at atmospheric pressures, of acetic acid (in the vapor phase with a nitrogen diluent) to ethane and carbon dioxide, accompanied with hydrogen evolution at the counter electrode. For cell voltages ranging from 4 to 10 V, current densities from 0.06 to... 

Kalimeri K K, Athanasiou C I and Marnellos G E (2010), Electro-reduction of nitrogen oxides using steam electrolysis in a proton conducting solid electrolyte membrane reactor (H+-SEMR) , Solid State Ionics, 181,223-229. 

Marin et al. (2010) smdied butane oxidation to maleic anhydride in a fixed-bed membrane reactor and compared the results with a fixed-bed reactor with the same production capacity. The results showed that with an increase in the length of the reactor, the temperature of the inlet gas, and the rate of air gas flow, and a decrease in the butane/nitrogen flow rate and the butane concentration, the butane concentration would enhance. Although in the membrane reactor, the selectivity was only slightly higher than that of a conventional one, it could be a good choice for butane oxidation because it allows higher butane inlet concentration. 

The preparation of a novel catalytic membrane system to be used in multiphase H2O2 production has also been discussed in detail by Tennison et al. in 2007. In their review, it was shown that it is possible to produce a membrane system that is potentially suitable for use in both multiphase and gas phase membrane reactor systems based on a 2-layer ceramic substrate. Moreover, the performance is sensitive to the degree of perfection of the support. The carbon membrane deposited within the nanoporous layer of the substrate has the structure and surface area to enable high dispersions of catalyst metals to be achieved when oxidized in carbon dioxide that have shown good performance in the direct synthesis of H2O2. When prepared under nitrogen, despite the simple production route, the carbon membrane shows excellent gas separation characteristics. 

Nonporous silver membrane tube (99.99 wt.% Ag), (in double pipe configurationX thickness 100/im. Feed enters the reactor at shell side, oxygen at tube side. Oxidation of ammonia. Silver catalyst in membrane form (see previous column). Oxidation of ethanol to acetaldehyde. Silver catalyst in membrane form (see previous column). r- 250-380°C. The yield of nitrogen was 40%, the yield of nitrogen monoxide was 25%. r- 250-380°C. The yield of acetaldehyde was 83%. The yield with bulk powdered silver catalyst was 56%. Gryaznov, Vedernikov and Guryanova (1986)... 

Propene oxidation was carried out by using an electrochemical reactor constructed from a Sm doped ceria electrolyte coated with YSZ (YSZ 1 SDC) as a membrane. In a blank test where nitrogen gas alone was passed over the Au anode instead of the reaction gas at 450 C, it was confirmed that the oxygen pumping was well controlled by the applied current, i.e., the amount of oxygen gas evolved at the anode coincided well the value calculated from the electric current by using Faraday s law. 

When used as a dense membrane in a reactor system the MIEC acts as a barrier between two isolated chambers allowing only the ionically conducted species to pass through the membrane under a chemical potential gradient. Air can be used as a freely available oxidant that is supplied to one chamber with no mixing of nitrogen with the product stream from an oxidation reaction as depicted in Figure 3.7,... 

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