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Microwaves and sorption on oxides: Surface temperature and adsorption selectivity investigation.

机译：微波和氧化物吸附：表面温度和吸附选择性研究。

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Microwave heating is not the same as conventional heating, and it is believed that this difference, the "microwave effect," may be interpreted to be due to selective local heating. The temperature at the surface where sorption occurs is "effectively" greater than the measured solid or gas temperature. In these studies, measurements of the amount adsorbed as functions of the partial pressure of a specific adsorbate in the presence of microwave irradiation were related to conventional adsorption isotherms. Equating the adsorbate pressure required to achieve a specific coverage (an isostere) in the presence of microwave irradiation to the amount adsorbed for a conventional isotherm allowed for an estimate of the "effective" surface temperature in the presence of microwaves. It was found that the effective surface temperature increased when using adsorbates having a significantly higher permittivity or when increasing the microwave power. The implication of this change in the surface energy for specific species in the presence of microwaves is discussed.;It was hypothesized that the adsorption selectivity in the presence of microwaves is primarily dependent on the permittivity of the adsorbates, while selectivity is dependent on the heat of adsorption under conventional heating. Sorption experiments were carried out using a flow based dual-component adsorption system measuring changes in the amount adsorbed with conventional heating and using microwave heating at 2.45 and 5.8 GHz. The adsorption selectivity as a function of microwave frequency was examined for a case in which the adsorbates have an opposite dependence of permittivity with frequency (isopropanol had a greater permittivity than acetone at 2.45 GHz, and acetone had a greater permittivity than isopropanol at 5.8 GHz). It was found that microwave energy could influence sorption differently than conventional heating. Differences in the adsorption selectivity were not as great as expected based on the bulk liquid permittivities due to the miscibility of the components. The permittivities of the adsorbates in the adsorbed phase at low surface coverage may be different than that of their respective bulk liquids. The smaller than expected change in adsorption selectivity with microwave frequency might also be attributed to the miscibility of acetone and isopropanol.
机译：微波加热与常规加热不同，可以相信，这种差异（“微波效应”）可以解释为是由于选择性局部加热引起的。发生吸附的表面温度“有效地”高于测得的固体或气体温度。在这些研究中，在微波辐照下，吸附量随特定吸附物分压的变化而变化的测量与常规吸附等温线有关。将在微波辐照下达到特定覆盖率（等排物）所需的吸附物压力等于常规等温线的吸附量，从而可以估算在微波存在下的“有效”表面温度。已经发现，当使用具有显着更高的介电常数的吸附物时或当增加微波功率时，有效表面温度会增加。讨论了在微波存在下特定物种的表面能变化的含义。假设在微波存在下的吸附选择性主要取决于被吸附物的介电常数，而选择性则取决于热量常规加热下的吸附量。使用基于流动的双组分吸附系统进行吸附实验，该系统通过常规加热以及在2.45和5.8 GHz的微波加热来测量吸附量的变化。在以下情况下检查了吸附选择性与微波频率的关系：被吸附物的介电常数与频率的依赖性相反（异丙醇在2.45 GHz时的介电常数比丙酮大，而丙酮在5.8 GHz时的介电常数大于异丙醇） 。已经发现，微波能与常规加热不同地影响吸附。由于组分的可混溶性，吸附选择性的差异不如基于总液体电容率所预期的那样大。在低表面覆盖率下，吸附相中被吸附物的介电常数可能与其各自的本体液体的介电常数不同。吸附选择性随微波频率的变化小于预期的变化也可能归因于丙酮和异丙醇的混溶性。

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