Performance of Thermal-catalytic Oxidization Technology for Formaldehyde Removal at Typical Indoor Environment. Xu Han Tianjin University 2013-05-14. Sample characterization. Materials: Impregnated carbon Metal oxidation. pore diameter distribution. SEM. Characterization: SEM/BET.
pore diameter distribution
Testing condition :
Temperature:24.5±1℃, RH:50±3 %，Flow rate：10.59 L/min，Concentration：1.0±0.1ppm，Residence time：0.01s
Figure 1. Formaldehyde outlet concentration for cases with different media
CuO/MnO2 shows best performance;
 ANSI/ASHRAE STANDARD 145.1-2008:Laboratory Test Method for Assessing the Performance of Gas-Phase Air-Cleaning System: Loose Granular Media  ANSI/ASHRAE STANDARD 2854,  V-Sorb 2800P
Objectives: make reaction reach stabilization ASAP, meanwhile, own proper conversion rate and bed depth.
Figure 1. Formaldehyde conversion at different GHSV
(equivalent to residence times of 0.0072, 0.0036 and 0.0018 s)
GHSV: gas hourly space velocity, h-1
Affection: residence time, conversion rate, stabilization time, mass transfer coefficient of external diffusion (through affect face velocity).
Note: testing condition: temperature 25±1 ℃; relative humidity 50±1% RH; inlet formaldehyde concentration 320±15 ppb.
Mass diffusion was eliminated when Vface≥ 1.2m/s
Figure 1. Reaction rates at different face velocities in the reactor
Method: keep operation condition and GHSV constant, change face velocity in the reactor;
Note: testing condition: 850±30 ppb inlet concentration, 25±1 ℃, 50±1% RH and GHSV 1,000,000 h-1
The formaldehyde one-through conversion decreases as the inlet concentration increases especially when the temperature is low.
Figure 1. Formaldehyde conversion at different inlet concentrations in the range of 180-1300 ppb at different temperatures
Method: tests of various inlet concentration (180 to 1300 ppb) were performed at four temperatures;
Note: testing condition: water vapor concentration 15,000 ppm, equivalent to 50±1% RH at 25±1 ℃; GHSV 1,000,000 h-1.
The results showed significant influence of relative humidity on the performance of CuO/MnO2 catalyst for formaldehyde conversion
Figure 1. Formaldehyde conversion at different relative humidities
Method: formaldehyde one-through conversions was tested with the same inlet concentration at three different relative humidity levels;
Note: testing condition: reaction temperature 25±1 ℃, inlet formaldehyde concentration 320±15 ppb, GHSV 1,000,000 h-1
Table 1. Kinetic Fitting Results Utilizing Different Models
a(Zhang, Y.P. et al. 2003). b(Hurtado, P. et al. 2004 and Liotta, L.F. 2010)
Figure 2. Parity plot comparing experimentally measured reaction rate with the predicted reaction rate of the L-H model.
Figure 1. Reaction rate at different surface formaldehyde concentration under different temperatures
Method: applying and L-H model Arrhenius law to experimental data in the catalytic oxidation of formaldehyde by CuO/MnO2.;
The performance of catalytic oxidation of formaldehyde by CuO/MnO2 at typical indoor environmental condition and concentration level (30-75% conversion).
The humidity shows significant influence on the catalytic oxidition of formaldehyde by CuO/MnO2 at room temperature.
The efficiency increased with increased temperature and decreased challenge concentration, and became independent of concentration when the temperature was increased to 180 ℃.
The catalytic oxidation of formaldehyde by CuO/MnO2 follows the L-H model best.
Further study was ongoing to study the mechanism of humidity effect and long term performance.