介孔材料Co/SBA-15催化环己基过氧化氢分解的研究

doi:10.15541/jim20160449

摘要/Abstract

摘要：

以介孔分子筛SBA-15为载体, 乙酸钴为钴源, 采用浸渍法制备了2wt%、4wt%、8wt%、10wt%和20wt% Co负载量的Co/SBA-15介孔材料。采用FT-IR、XRD、N₂物理吸附、UV-Vis、SEM、TEM、H₂-TPR等技术对催化材料的结构进行表征, 并将其应用于环己基过氧化氢分解反应。结果表明: 负载金属钴后, 载体的介孔结构保持完好, 随着负载量的增加, Co/SBA-15的比表面积、总孔体积和平均孔径不断减小, Co由骨架内均匀分散状态向氧化物Co₃O₄的形式转变。不同负载量的 Co/SBA-15在环己基过氧化氢分解反应中均表现出较好的催化性能, 其中8wt%Co/SBA-15催化环己基过氧化氢的转化率达到98.1%, 环己醇和环己酮的选择性分别为70.9%和27.9%。当负载量相对较低时, 钴的流失使催化性能下降明显, 只有当钴负载量增加到20wt%, 主要以Co₃O₄形式存在时, 钴的流失速率得到抑制, 连续使用五次后仍能保持较高的活性和选择性。

关键词: Co/SBA-15, 环己基过氧化氢, 分解

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

郭露露, 李立霞, 何鹏程, 袁霞. 介孔材料Co/SBA-15催化环己基过氧化氢分解的研究[J]. 无机材料学报, 2017, 32(5): 543-549.

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.

图/表 11

图1 Co/SBA-15催化剂的红外光谱图

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

图2 Co/SBA-15催化剂的紫外光谱图

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

图3 Co/SBA-15催化剂的XRD图谱

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

表1 Co/SBA-15的物理结构性能

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

图4 SBA-15催化剂的氮气物理吸附-脱附曲线(A)和孔径分布图(B)

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

图5 (a, d) SBA-15,(b, e) 8wt%Co/SBA-15和 (c, f) 20wt%Co/SBA-15的SEM和TEM照片

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

图6 催化剂的H2-TPR图谱

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

表2 Co/SBA-15催化剂在CHHP分解反应中的催化性能

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

表3 回收催化剂Co/SBA-15在CHHP分解反应中的催化性能

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

图7 10wt%Co/SBA-15(A)和20wt%Co/SBA-15(B)回收后的催化性能

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

图8 20wt%Co/SBA-15和4次回收后催化剂的XRD谱图(A)和紫外图谱(B)

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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