Raschig ring

Abstract: Total and static holdups have been measured for 1/2-, and 1-in. ceramic Berl saddles, 1/2-, 1-, and 1 1/2-in. ceramic Raschig rings, and 1-in. carbon Raschig rings with air rates from 100 to 1,000 1b./(hr.) (sq. ft.) and water rates from 1,000 to 10,000 1b./ (hr.) (sq. ft.). The holdup measurements and motion picture observations of the flow of dye solutions through packings provide an explanation for the great differences observed when gas-phase mass transfer rates are measured by absorption and vaporization methods. If the effective interfacial area for vaporization is assumed to be proportional to total holdup and the area for absorption is assumed proportional to operating holdup, the raio of the two mass transfer rates should be equal to the ratio of the two holdups. The departure from equality of the two ratios can be explained by the observation that the static holdup is displaced slowly, resulting in additional effective area for absorption over that expected from the operating holdup alone.

Abstract: Fe 2 O 3 on Raschig glass rings (Fe 2 O 3 /RR) was investigated as photocatalyst under simulated solar radiation during the degradation of 4-chlorophenol (4-CP) and the azo dye Orange II (Or II). Thin films of Fe 2 O 3 particles were coated on glass rings using polyethylene-graft-maleic anhydride (PEGMA) as a negative interfacial agent. The Fe 2 O 3 /RR photocatalyst presented absorption in the visible range up to 535 nm. The catalytic activity of Fe 2 O 3 /RR coated with preformed Fe 2 O 3 (11.4 m 2 /g) was found to be superior to that of Fe 2 O 3 /RR1 catalyst obtained by the precipitation of Fe-ions on the glass rings surface. The photoactivated degradation of 4-CP and Or II was possible at pH values of 5.5 using both catalysts. The Fe 2 O 3 /RR photocatalyst shows a stable catalytic performance during long-term operation under simulated sunlight radiation. The Fe 2 O 3 /RR and Fe 2 O 3 /RR1 photocatalysts were characterized by diffusion reflectance spectroscopy (DRS), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), atomic absorption spectroscopy (AAS) and gas adsorption measurements (BET). The Fe 2p binding energy (BE) in the Fe 2 O 3 /RR samples was 711.6 eV before the catalysis and 711.7 eV after the catalysis, indicating the stability of the Fe-oxidation state on the glass rings. The pore diameter did not decrease when going from Fe 2 O 3 powder to the Fe 2 O 3 attached on the Raschig glass rings but the Fe 2 O 3 BET area decreased considerably involving restructuring of the Fe 2 O 3 particles. The experimental data allows to formulate a mechanism of reaction for the degradation of 4-CP on the Fe 2 O 3 /RR catalyst.