Modification of Biochar Catalyst Using Copper for Enhanced Catalytic Oxidation of VOCs

Abstract

Recently, research has increasingly focused on the introduction of non-precious metals and developing highly stable carriers to enhance catalyst performance. In this study, we successfully synthesized copper (Cu)-modified biochar catalysts utilizing a sequential approach involving enzymatic treatment, liquid impregnation, and activation processes, which effectively enhanced the dispersion and introduction efficiency of Cu onto the biochar, thereby reducing the requisite Cu loading while maintaining high catalytic activity. The experimental results showed that the toluene degradation of 10%Cu@BCL was three times higher than that of unmodified activated carbon (AC) at 290 °C. A more uniform distribution of Cu was obtained by the enzymatic and activation treatments, optimizing the catalyst's structural properties and reducing the amount of Cu on the biochar. Moreover, the transformation between various oxidation states of Cu (from Cu⁰/Cu(I) to Cu(II)) facilitated the electron transfer during the degradation of toluene. To further understand the catalytic mechanisms, density functional theory (DFT) calculations were employed to elucidate the interactions between toluene molecules and the Cu-modified biochar surface. These findings reveal that the strategic modification of biochar as a carrier not only enhances the dispersion and stability of active metal species but contributes to improved catalytic performance, thereby enhancing its degradation efficiency for VOCs in high-temperature conditions.

Keywords: VOCs; biochar; catalytic oxidation technology; copper.

Figure 1

Experimental setup 1. O₂ and N₂ gas cylinder. 2. Flow meter. 3. Wash bottle. 4. Gas mixing vessel. 5. Catalytic oxidation reactor. 6. Catalyst filler layer. 7. Insulation jacket. 8. Gas chromatography.

Figure 2

Influence of Cu loading on toluene degradation (activation temperature 700 °C, GHSV 60,000 h⁻¹).

Figure 3

Impact of enzymatic treatment on catalyst performance (10wt% Cu loading, GHSV 60,000 h⁻¹).

Figure 4

Influence of activation temperature on the degradation efficiency of toluene by different catalysts (GHSV 60,000 h⁻¹, temperature range: 30–500 °C, heating rate: 10 °C·min⁻¹, carrier gas: 10% O₂/90% N₂).

Figure 5

Thermogravimetry of catalytic materials at different reaction temperatures (GHSV 60,000 h⁻¹, temperature range: 30–500 °C, heating rate: 10 °C·min⁻¹, carrier gas: 10% O₂/90% N₂).

Figure 6

SEM images of catalysts prepared under different conditions: (a) BC-700; (b) Cu@BC-700; (c) BCL-700; (d) Cu@BCL-700; (e) Cu@BCL-800; (f) Cu@BCL-1000 (accelerating voltage: 10 kV, magnification: ×10,000 and ×20,000).

Figure 7

XRD patterns of catalysts prepared under different conditions. (a) XRD patterns of catalysts with varying Cu loadings. (b) XRD patterns of catalysts subjected to different activation temperatures (2θ range of 5–90°, scan rate of 2°/min).

Figure 8

XPS patterns of catalysts prepared under different conditions. (a) XPS patterns of catalysts with varying Cu loadings. (b) XPS patterns of catalysts with varying activation temperatures. (Scanning range: 0–1350 eV, step size: 1.0 eV.)

Figure 9

The chemical valence analysis of Cu@BCL catalyst. (a) C 1s before catalyst reaction; (b) C 1s after catalyst reaction; (c) O 1s before catalyst reaction; (d) O 1s after catalyst reaction; (e) Cu 2p before catalyst reaction; (f) Cu 2p after catalyst reaction. (Scanning range: 0–1350 eV, step size: 1.0 eV.)

Figure 10

The FT-IR spectra of catalysts prepared under different conditions. (a) The FT-IR spectra of BC and BCL; ■ BC; ■ BCL. (b) FT-IR spectra of BCL, Cu@BC, and Cu@BCL; ■ BCL; ■ Cu@BC; ■ Cu@BCL (64 scans in 400–4000 cm⁻¹, resolution of 4 cm⁻¹).

Figure 11

Visualizations of interactions between toluene and Cu@BCL. (a) Geometry optimizations of toluene. (b) Geometry optimizations of Cu (111). (c) Interactions between toluene and Cu (111). (d) Geometry optimizations of Cu₂O (111). (e) Interactions between toluene and Cu₂O (111).