Removal of CO from Hydrogen Fuel by Using Platinum-Loaded Zeolite Catalytic Membranes

在多孔α-Al_2O_3载体管上形成Y型分子筛膜，然后与铂进行离子交换。将负载铂的Y型分子筛膜用作催化膜，用于10000 ppm的氢气中CO的氧化。CO和O_2通过无缺陷膜的平均停留时间估计至少是H_2的10倍。这导致了CO在渗透过程中的选择性氧化。当氧气流量为CO流量的1.2倍时，在反应温度为523K时，渗透侧的CO浓度可降至检出限(8ppm)以下。在另一项实验中，在多孔γ-Al_2O_3支撑管上制备了负载Rh的α-Al_2O_3膜，并进一步在其上涂覆了一层高选择性H_2的二氧化硅膜。当加入H_2、CO和O_2的混合气时(CO浓度)。=50000 ppm)时，CO渗透通量随O2进料速率的增加而减小，在523K时CO浓度降至48ppm以下。在很短的接触时间内，CO的高氧化产率可以归因于独特的速率表达式，该速率表达式在CO阈值浓度处具有最大值。因此，为了获得非常高的CO转化率，需要较长的反应时间。然而，当用膜粗略地分离CO时，所需的反应时间大大缩短，因为通过膜的渗透，CO浓度几乎降低到阈值。

A Y-type zeolite membrane was formed on a porous α-alumina support tube, and then ion-exchanged with Pt. The Pt-loaded Y-type zeolite membrane was used as a catalytic membrane for use in the oxidation of CO, which was mixed in hydrogen at a concentration of 10000 ppm. The mean residence time of CO and O_2 for crossing the defect-free membrane was estimated to be at least 10 times longer than that of H_2. This resulted in the selective oxidation of CO during its permeation through the membrane. When the flow rate of O_2 was 1.2 times that of CO, the CO concentration on the permeate side at a reaction temperature of 523 K was decreased below the limit of detection (8 ppm). In a separate experiment, a Rh-loaded γ-Al_2O_3 membrane was prepared on a porous α-alumina support tube, and was further coated with a highly H_2-selective silica membrane. When a mixture of H_2, CO and O_2 was feed (CO conc. = 50000 ppm), the CO permeation flux decreased with increasing O_2 feed rate, and the CO concentration to less than 48 ppm at 523 K.These high CO oxidation yields in very short contact times can be attributed to the unique rate expression which has a maximum at the threshold CO concentration. Thus, a long reaction times is required in order to attain a very high CO conversion. When CO is roughly separated using a membrane, however, the necessary reaction time is shortened drastically because the CO concentration is decreased nearly to the threshold values by permeation through the membrane.