Capture of CO₂ on γ-Al₂O₃ materials prepared by solution-combustion and ball-milling processes

Figures & data

Figure 1. Mechanical high-energy ball mill Spex 8000 type for an experimental setup to make the particles.

Table 1. Experimental ball milling conditions.

Samples	Nominal composition	Solution combustion	Milling time (h)	Ball to powder mass ratio	Number of balls	Ball mass (g)
γ-Al2O3	γ-Al2O3	800ºC/5 min	—	—	—	—
Al2O3	γ-Al2O3	800ºC/5 min	10	6:1	17	18.08
γ-Al2O3/Ni	γ-Al2O3-2 wt.% Ni	800ºC/5 min	7.5	6:1	17	18.04
γ-Al2O3/Fe	γ-Al2O3-2 wt.% Fe	800ºC/5 min	7.5	6:1	17	18.01

Figure 2. Schematic diagram of the CO₂ adsorption on as-prepared porous γ-Al₂O₃ samples over a Parr 4592 stainless-steel pressure reactor.

Table 2. Textural properties by nitrogen physisorption of porous γ-Al₂O₃ samples prepared by solution-combustion and ball-milling processes.

Samples	Method	SBET (m^2/g)	Vt (cm^3/g)^a	Rp (nm)^b
γ-Al2O3	Solution combustion	189.32 ± 2.21	0.1735 ± 0.08	1.64 ± 0.03
Al2O3	10 hr of ball milling	120.21 ± 3.67	0.2009 ± 0.02	1.21 ± 0.05
Al2O3-Ni	7.5 hr of ball milling	14.10 ± 1.78	0.0181 ± 0.01	1.21 ± 0.02
Al2O3-Fe	7.5 hr of ball milling	6.93 ± 1.02	0.0507 ± 0.01	4.61 ± 0.01

Notes: ^aTotal pore volume by N₂ adsorption at p/p_o = 0.99.

^bAverage pore size estimated from the desorption branch of the isotherms based on the BJH (Barrett–Joyner–Halenda) model.

Figure 3. XRD patterns of porous γ-Al₂O₃ samples prepared by (a) solution combustion, (b) solution combustion after 10 hr of ball milling, (c) γ-Al₂O₃/Ni, and (d) γ-Al₂O₃/Fe after 7.5 hr of ball-milling.

Figure 4. SEM micrographs of porous γ-Al₂O₃ samples prepared by (a) solution combustion, (b) solution combustion after 10 hr of ball-milling, (c) γ-Al₂O₃/Ni, and (d) γ-Al₂O₃/Fe after 7.5 hr of ball-milling.

Table 3. γ-Al₂O₃ prepared by solution combustion; textural properties and adsorption capacity (q_ads) as a function of ball milling time.

Sample	Ball-milling time	SBET (m^2/g)	Vt (cm^3/g)^a	Rp (nm)^b	qads (mmol/g)
γ-Al2O3	0 hr	189.32 ± 2.21	0.1735 ± 0.08	1.64 ± 0.03	1.70 ± 0.23
γ-Al2O3	5 hr	134.51 ± 2.27	0.1239 ± 0.06	1.86 ± 0.01	0.48 ± 0.01
γ-Al2O3	10 hr	120.21 ± 3.67	0.2009 ± 0.02	1.21 ± 0.02	1.94 ± 0.05
γ-Al2O3	15 hr	84.37 ± 1.22	0.1770 ± 0.01	1.21 ± 0.01	0.58 ± 0.02

Notes: ^aTotal pore volume by N₂ adsorption at p/p_o = 0.99.

^bAverage pore size estimated from the desorption branch of the isotherms based on the BJH (Barrett–Joyner–Halenda) model.

Figure 5. Nitrogen adsorption–desorption isotherms curves for the porous γ-Al₂O₃ samples prepared by (a) solution combustion, (b) solution combustion after 10 hr of ball milling, (c) γ-Al₂O₃/Ni, and (d) γ-Al₂O₃/Fe after 7.5 hr of ball milling.

Figure 6. Pore size distribution curves obtained using the BJH method for the porous γ-Al₂O₃ samples prepared by (a) solution combustion, (b) solution combustion after 10 hr of ball milling, (c) γ-Al₂O₃/Ni, and (d) γ-Al₂O₃/Fe after 7.5 hr of ball milling.

Figure 7. TGA curves and its MS profiles of the evolved gas: CO₂ (m/e = 44) during the decomposition of porous γ-Al₂O₃ samples prepared by (a) solution combustion, (b) solution combustion and ball milling, (c) γ-Al₂O₃/Ni-CO₂, and (d) γ-Al₂O₃/Fe-CO₂ in helium.