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CNTs show promise as a filter and a catalyst support

By Scott Jenkins |

Carbon nanotube (CNT) membranes developed by researchers at Rice University (Houston; www.rice.edu) could have applications as nanoparticulate filters, and as nanoscale scaffolds for catalysts. The devices are silicon dioxide wafers with laser-bored holes (~500-µm dia.). The holed wafers are subjected to a chemical-vapor-deposition (CVD) process, during which a “forest” of CNTs grows inside the holes (photo). The CNTs inside the holes create a matrix through which only nanoscale particles can pass. In testing, the research team, led by Rice engineer Robert Vajtai, was able to remove greater than 99% of sub-micron particles from air. The filters’ permeability is affected strongly by the duration of nanotube growth, Vajtai explains. In a recent paper in the journal ACS Nano, the researchers reported functionalizing the nanotubes with catalytic palladium metal to achieve gas-phase heterogeneous catalysis. Using the dehydrogenation reaction of propene to propane as a test system, the activated membranes showed “excellent and durable activity” as a catalytic support, enabling a low activation energy for the propene dehydrogenation reaction of ~27.8 kJ/mol and a turnover rate of 1.1 molecules per Pd site…
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