Experimental study and kinetic model analysis on photothermal catalysis of formaldehyde by manganese and cerium based catalytic materials

Figures & data

Figure 1. Experimental system diagram for formaldehyde purification performance testing 1. Formaldehyde generator; 2. Three-way valve; 3. Solar simulator; 4. Experimental cabin; 5. Stirring fan; 6. Catalyst carrier; 7. Catalyst; 8. Glass wall surface; 9. Formaldehyde detector; 10. Temperature sensor; 11. Vacuum pump; 12. Detection.

Figure 2. ULTRA-VITALUX spectral radiant power distribution.

Figure 3. Absorption characteristics of MnO_x-CeO₂ catalyst.

Figure 4. H₂-TPR spectrum of MnO_x-CeO₂ catalyst.

Figure 5. Scanning electron micrographs of the MnO_x-CeO₂ catalyst at 20,000$\times$ and 50,000$\times$ magnification.

Figure 6. N₂ adsorption and desorption isotherm curve of MnO_x-CeO₂ catalyst.

Table 1. Specific surface area, pore volume, and average pore diameter of the MnO_x-CeO₂ catalyst.

Catalyst	Specific surface area ($m^2/g$)	Pore volume ($c{m}^3/g$)	Average pore size ($nm$)
MnOx-CeO2	34.007	0.093	10.93

Table 2. Experimental condition table.

Working condition	Experiment time (min)	Type of catalyst	The temperature in the experimental chamber (℃)	solar radiation intensity (w/m^2)	Formaldehyde initial concentration (ppb)	catalyst loading (g/m^2)
1	300	MnOx-CeO2	62.6 ± 0.2	550	1000 ± 5	20
2		MnOx-CeO2	62.6 ± 0.2	550	500 ± 5	20
3		MnOx-CeO2	62.6 ± 0.2	550	200 ± 5	20
4		MnOx-CeO2	56.7 ± 0.2	450	500 ± 5	20
5		MnOx-CeO2	68.2 ± 0.2	650	500 ± 5	20
6		MnOx-CeO2	62.6 ± 0.2	550	500 ± 5	10
7		MnOx-CeO2	62.6 ± 0.2	550	500 ± 5	40

Figure 7. Reaction rate of MnO_x-CeO_2-catalyzed formaldehyde at different temperatures, concentrations and loadings.

Figure 8. MVK model fitting of formaldehyde catalysis at different temperatures.

Figure 9. MVK model fitting of formaldehyde catalysis at different concentrations.

Figure 10. LH model fitting of formaldehyde catalysis at different temperatures.

Figure 11. LH model fitting of formaldehyde catalysis at different concentrations.

Figure 12. ER model fitting of formaldehyde catalysis at different temperatures.

Figure 13. ER model fitting of formaldehyde catalysis at different concentrations.

Figure 14. ER model fitting of formaldehyde catalysis at different concentrations.

Table 3. MVK kinetic model parameters of thermal catalytic oxidation of formaldehyde.

Temperature (°C)	Formaldehyde concentration ($ppb$)	$k_1$ ($m/s$)	$k_2^{\prime }$($ppb/s$)	$R^2$
56.7 ± 0.2	500 ± 10	0.009293	3.7064	0.9584
62.6 ± 0.2	500 ± 10	0.016178	3.231	0.3637
68.2 ± 0.2	500 ± 10	0.004524	2.8673	0.6245
62.6 ± 0.2	200 ± 4	0.002476	0.7427	0.7079
62.6 ± 0.2	500 ± 10	0.016178	3.231	0.3637
62.6 ± 0.2	1000 ± 20	0.011673	4.8375	0.7508

Table 4. LH kinetic model parameters of thermal catalytic oxidation of formaldehyde.

Temperature (°C)	Formaldehyde concentration ($ppb$)	$k{ }^{\mathrm{\prime }}$ ($ppb/s$)	$K_i^{\prime }$($pp{b}^{-1}$)	$R^2$
56.7 ± 0.5	500 ± 10	0.0044	6.7003E–4	0.8845
62.6 ± 0.5	500 ± 10	0.0164	1.6059 E-4	0.8942
68.2 ± 0.5	500 ± 10	1.71	2.2896 E-7	0.8760
62.6 ± 0.5	200 ± 4	0.299	6.1598 E-6	0.7798
62.6 ± 0.5	500 ± 10	0.01648	1.6063 E-4	0.8942
62.6 ± 0.5	1000 ± 20	0.01135	1.9133 E-4	0.8675

Table 5. ER kinetic model parameters of thermal catalytic oxidation of formaldehyde.

Temperature (°C)	Formaldehyde concentration ($ppb$)	|$k{ }^{\mathrm{\prime }}$| ($ppb/s$)	|$K_i$ ($pp{\mathrm{b}}^{-1}$)|	$k{ }^{\mathrm{\prime }}{K}_i$($m/s$)	$R^2$	$R^{2\prime }$
56.7 ± 0.2	500 ± 10	4.095	0.0021	0.0086	0.9747	0.9825
62.6 ± 0.2	500 ± 10	6.9759	8.8877E–5	0.0062	0.9092	0.9850
68.2 ± 0.2	500 ± 10	2.875	0.0016	0.0046	0.9410	0.9825
62.6 ± 0.2	200 ± 4	0.8125	0.0032	0.0026	0.9470	0.9815
62.6 ± 0.2	500 ± 10	6.9759	8.8877E–5	0.0062	0.9092	0.9850`
62.6 ± 0.2	1000 ± 20	11.6	0.0005	0.0058	0.8251	0.8907

Figure 15. Diagram of the formaldehyde purification system in the car.

Data availability statement

The authors confirm that the data supporting the findings of this study are available within the article.