Catalytic Combustion of Chlorobenzene in a Fixed-Bed Reactor

The performance of catalytic combustion for chlorobenzene was evaluated in a fixed-bed reactor consisting of a quartz tube (i.d. = 4 mm) under standard atmospheric pressure. In each experiment, 100 mg of catalysts (40–60 mesh) was immobilized using quartz wool, resulting in a gas hourly space velocity (GHSV) of 20,000 mL·g⁻¹ h⁻¹ and a total flow rate of 33.33 mL·min⁻¹. The liquid reactant (chlorobenzene) was introduced into the feed stream by passing dried air through a saturator maintained at a temperature of 6 °C. The feed stream was then diluted with dried air generating a feeding flow containing 1000 ppm reactant and 21% O₂/79% N₂. Flow rates were regulated using online mass flowmeters. Concentrations of CB and chlorinated byproducts were determined via analysis on an online gas chromatograph (GC3420A, Beifen Ruili Co., Ltd., Beijing, China) equipped with both flame ionization detector (FID) and electron capture detector (ECD) for quantitative assessment of organic compounds. Furthermore, the outlet CO₂ underwent reduction by hydrogen within a methanation furnace before being detected by the same chromatograph system. A K-type thermocouple was inserted into the catalyst to monitor its temperature during the catalytic performance test. Data of catalytic oxidation tests were collected after achieving steady state conditions for at least thirty minutes. The detailed structure of the catalytic test system is shown in Figure 1.
The CB conversion rate ( $X_{CB}$ , %), CO₂yield ( ${CO}_{2}yield$ , %) and organic byproduct yield ( $Y_b$ , %) were calculated as follows: $$X_{CB}=\frac{{\left(\mathrm{C}\mathrm{B}\right)}_{in}-{\left(\mathrm{C}\mathrm{B}\right)}_{out}}{{\left(\mathrm{C}\mathrm{B}\right)}_{in}}\times 100\mathrm{\%},$$
$${CO}_{2}yield=\frac{({{\mathrm{C}\mathrm{O}}_2)}_{out}}{6\times {\left(\mathrm{C}\mathrm{B}\right)}_{in}}\times 100\mathrm{\%},$$
$$Y_b=X_{CB}-{CO}_{2}yield,$$
where ${\left(\mathrm{C}\mathrm{B}\right)}_{in}$ and ${\left(\mathrm{C}\mathrm{B}\right)}_{out}$ are the inlet and outlet concentrations of chlorobenzene, respectively. $({{\mathrm{C}\mathrm{O}}_2)}_{out}$ is the outlet concentrations of CO₂.
The reaction rate of 1,2-dichloroethane was calculated as follows: $$\mathrm{r}=\frac{Q\times X_{CB}}{m}$$
where r is the reaction rate (mol·g⁻¹·s⁻¹), Q is the molar flow of chlorobenzene (mol·s⁻¹), and m is the mass of the catalyst (g).
The stability test for chlorobenzene was performed continuously at 290–320 °C for 100 h under the same conditions as the catalytic combustion test, unless otherwise indicated.