Mesoporous Material Co/SBA-15 as Catalyst for the Decomposition of Cyclohexyl Hydroperoxide

doi:10.15541/jim20160449

Abstract

Abstract:

A series of mesoporous material Co/SBA-15 with Co loading of 2wt%, 4wt%, 8wt%, 10wt%, and 20wt% were prepared through incipient wetness impregnation method using SBA-15 as support and cobalt acetate as Co source. The structures of obtained samples were characterized by FT-IR, X-ray diffraction (XRD), N₂ adsorption-desorption, Diffuse reflectance UV-Vis, SEM, TEM, and hydrogen temperature programmed reduction (H₂-TPR) techniques. Their catalytic performance in decomposition of cyclohexyl hydroperoxide were also studied. Results show that the mesoporous structure of support remains intact after loading with Co. The specific surface area, pore volume and pore diameter of Co/SBA-15 are gradually decreased with the increase of loading amount. All the samples showed excellent catalytic activity in the decomposition of cyclohexyl hydroperoxide. The 8%Co/SBA-15 showed the highest catalytic performance with a conversion of 98.1% and selectivity of cyclohexanone 70.9% and cyclohexanol 27.9%. However, the loss of Co from the lower loading amount samples resulted in catalytic performance decreased significantly after reuse. Only when the loading of Co increases to 20% mainly in the form of Co₃O₄, the loss rate of Co can be inhibited and the catalytic activity and selectivity of recovered catalyst remain constant after using for five times.

Key words: Co/SBA-15, cyclohexyl hydroperoxide, decomposition

GUO Lu-Lu, LI Li-Xia, HE Peng-Cheng, YUAN Xia. Mesoporous Material Co/SBA-15 as Catalyst for the Decomposition of Cyclohexyl Hydroperoxide[J]. Journal of Inorganic Materials, 2017, 32(5): 543-549.

Figures/Tables 11

Fig. 1 FT-IR spectra of Co/SBA-15 Catalyst

Fig. 2 DR UV-Vis spectra of Co/SBA-15 calalyst

Fig. 3 XRD patterns of Co-SBA-15 Catalyst

Table 1 Physicochemical properties of synthesized Co/SBA-15 Catalyst

Sample	A_BET/(m²•g^-1)	V_pore/(cm³•g^-1)	D_pore/nm
SBA-15	582	1.64	6.64
2wt%Co/SBA-15	426	1.42	6.64
4wt%Co/SBA-15	372	1.40	6.59
8wt%Co/SBA-15	493	1.50	6.63
10wt%Co/SBA-15	378	0.65	5.69
20wt%Co/SBA-15	368	0.51	3.82

Fig. 4 N2 adsorption-desorption isotherms (A) and pore diameter distributions (B) for Co/SBA-15

Fig. 5 SEM and TEM images of (a, d) SBA-15; (b, e) 8wt%Co/SBA-15;(c, f) 20wt%Co/SBA-15

Fig. 6 H2-TPR spectra of Co/SBA-15

Table 2 Catalytic decomposition of CHHP over Co/SBA-15

Catalysts	Co/wt%^a	Conversion/%	Selectivity/%				Selectivity/%
Catalysts	Co/wt%^a	Conversion/%	A	K	Acids	Others	A+K
2wt%Co-SBA-15	0.82	96.4	68.8	29.6	0.7	0.9	98.4
4wt%/Co-SBA-15	3.37	97.0	70.1	29.5	0.3	0.1	99.6
8wt%/Co-SBA-15	7.86	98.1	70.9	27.9	0.9	0.3	98.8
10wt%/Co-SBA-15	8.97	97.4	57.0	27.8	1.7	13.4	84.8
20wt%/Co-SBA-15	15.40	97.0	66.4	30.0	2.3	2.7	96.4

Table 3 Catalytic performance of the recycled Co/SBA-15 in decomposition of CHHP

Catalysts	Co/wt%^a	Conversion/%	Selectivity/%				Selectivity/%
Catalysts	Co/wt%^a	Conversion/%	A	K	Acids	Others	A+K
2wt%Co-SBA-15-r-1	0.06	70.0	67.2	28.2	1.8	2.8	95.4
4wt%/Co-SBA-15-r-1	—	96.9	65.7	34.3	0	0	100.0
4wt%/Co-SBA-15-r-2	0.98	91.3	64.9	35.1	0	0	100.0
8wt%/Co-SBA-15-r-1	—	97.5	69.9	28.5	1.6	0.0	98.4
8wt%/Co-SBA-15-r-2	1.86	92.9	62.2	24.4	2.8	10.6	86.6

Fig. 7 Recycling performance of 10wt%Co/SBA-15 and 20wt%Co/SBA-15 catalysts Reactions conditions: 10 mL cyclohexane oxidation liquid (containing CHHP 7.72%), 0.1 g catalyst, T = 70℃, time = 90 min A-cyclohexanol, K-cyclohexanone

Fig. 8 XRD patterns (A) and DR UV-Vis spectra (B) of (a) 20wt%Co/SBA-15 and (b) 20%Co/SBA-15 after 4 runs

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