WO<sub>3-<i>x</i></sub>/CFs三相催化剂的制备及其可见光催化转化甲烷制甲醇

荣丽青; 杨娟; 戴俊; 王大钊

doi:10.13801/j.cnki.fhclxb.20220627.001

WO_3-x/CFs三相催化剂的制备及其可见光催化转化甲烷制甲醇

doi: 10.13801/j.cnki.fhclxb.20220627.001

荣丽青¹,
杨娟^{1, 2, 3, ,},
戴俊^{1, 2},
王大钊¹

1.
河南理工大学　安全科学与工程学院，焦作 454003
2.
煤炭安全生产与清洁高效利用省部共建协同创新中心，焦作 454003
3.
河南理工大学　化学化工学院，焦作 454003

基金项目: 国家自然科学基金(52074103；U2004194)；河南省自然科学基金(202300410181)；河南省科技攻关重点项目(222102320095)；河南省教育厅重点科研项目(21 A440008)National Natural Science Foundation of China (52074103; U2004194); Natural Science Foundation of Henan Province (202300410181); Key Science and Technology Project of Henan Province (222102320095); Key Scientific Research Project of Henan Province Education Department (21 A440008)

详细信息

通讯作者:
杨娟，博士，教授，研究方向为光催化与能源化学　E-mail: yangjuan@hpu.edu.cn

中图分类号: TB333
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出版历程
- 收稿日期: 2022-05-09
- 修回日期: 2022-06-12
- 录用日期: 2022-06-18
- 网络出版日期: 2022-06-27
- 刊出日期: 2023-05-15

Preparation of WO_3-x/CFs triphase catalyst and visible-light photocatalytic conversion of methane to methanol

RONG Liqing¹,
YANG Juan^{1, 2, 3
, ,},
DAI Jun^{1, 2},
WANG Dazhao¹

1.
School of Safety Science and Engineering, Henan Polytechnic University, Jiaozuo 454003, China
2.
State Collaborative Innovation Center of Coal Work Safety and Clean-efficiency Utilization, Jiaozuo 454003, China
3.
School of Chemistry and Chemical Engineering, Henan Polytechnic University, Jiaozuo 454003, China

摘要

摘要: 将甲烷选择性转化为平台分子甲醇是有效利用天然气资源的理想途径之一，低碳排放的光催化技术可在室温常压下活化与转化甲烷，但水相光催化体系的甲烷转化性能仍较低。采用水热法首先合成富含氧缺陷的氧化钨(WO_3-x)，借助聚四氟乙烯浓缩液(PTFE)将WO_3-x负载至碳纤维(CFs)表面制备WO_3-x/CFs三相光催化剂，改变PTFE添加量可调控WO_3-x/CFs的表面浸润性，通过XRD、SEM、水接触角、电子顺磁共振波谱仪(EPR)和低温氮吸脱附等测试技术对催化剂的形貌、结构与表面特性进行系统表征。可见光催化实验结果表明：WO_3-x/CFs三相体系可显著提升甲烷至甲醇的转化性能，最优催化剂WO_3-x/CFs-0.3的甲烷转化量为2522.20 μmol·g⁻¹，分别为WO_3-x/氧化铟锡导电玻璃(Glas)与粉末WO_3-x两相体系的1.76倍和2.48倍；相应的甲醇产生量为1918.83 μmol·g⁻¹，分别为WO_3-x/Glas与粉末WO_3-x体系的2.81倍和4.69倍，同时三相体系的甲醇选择性高达76.76%。WO_3-x/CFs光催化性能增强主要源于疏水性催化剂形成的气-液-固三相界面，消耗的甲烷可经CFs气体传输通道直接传质至催化界面，促进甲烷分子活化与转化。此外，三相光催化体系循环稳定性优异，WO_3-x/CFs-0.3经6次循环后甲醇产生量仍可达1506.98 μmol·g⁻¹。
- 甲烷 /
- 甲醇 /
- 可见光催化 /
- WO_3-x /
- 三相界面 /
- 碳纤维
Abstract: Selective conversion of methane into platform molecule methanol is one of the ideal ways to effectively utilize natural gas resources. Photocatalytic technology with low carbon emission can activate and transform methane at room temperature and atmospheric pressure, whereas the methane conversion performance of aqueous photocatalytic system is still low. Oxygen defects-rich WO_3-x was firstly synthesized through hydrothermal method and then triphase photocatalyst WO_3-x/CFs was constructed by loading WO_3-x on carbon fiber (CFs) with polytetrafluoroethylene concentrate (PTFE). Changing the addition amount of PTFE, the surface wettability of WO_3-x/CFs can be regulated. The morphology, structure and surface properties of triphase catalysts were systematically characterized by XRD, SEM, water contact angle, electron paramagnetic resonance (EPR) and low temperature nitrogen adsorption-desorption. The results of visible-light photocatalytic experiments show that WO_3-x/CFs triphase system can significantly improve the conversion performance of methane into methanol. Methane conversion amount of the optimal WO_3-x/CFs-0.3 catalyst is 2522.20 μmol·g⁻¹, which is 1.76 times and 2.48 times of WO_3-x/Indium tin oxide conducting glass (Glas) and powder WO_3-x diphase systems, respectively. Methanol yield of WO_3-x/CFs-0.3 triphase system is 1918.83 μmol·g⁻¹, which is 2.81 times and 4.69 times of WO_3-x/Glas and powder WO_3-x systems respectively, and meanwhile methanol selectivity of triphase WO_3-x/CFs system is up to 76.76%. The enhanced photocatalytic performance of WO_3-x/CFs is primarily due to the gas-liquid-solid triphase interface formed by the hydrophobic catalyst. The consumed methane can be directly transferred to the catalytic interface through gas transport channel in CFs, promoting the activation and conversion of methane molecules. Additionally, the triphase photocatalytic system shows excellent cyclic stability and the methanol yield of WO_3-x/CFs-0.3 can still reach 1506.98 μmol·g⁻¹ after 6 cycles.
- methane /
- methanol /
- visible-light photocatalysis /
- WO_3-x /
- triphase interface /
- carbon fiber

HTML全文

图 1 粉末WO_3-x (a)和WO_3-x/碳纤维(CFs)三相催化剂(b)的制备示意图

PTFE—Polytetrafluoroethylene

Figure 1. Schematic diagram of the synthesis for WO_3-x powder (a) and WO_3-x/carbon fiber (CFs) triphase catalyst (b)

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图 2 甲烷光催化转化实验装置示意图

Figure 2. Schematic diagram of the experimental setup for photocatalytic conversion of methane

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图 3 WO_3-x(a)、空白CFs (b)、WO_3-x/CFs-0 (c)、WO_3-x/CFs-0.1 (d)、WO_3-x/CFs-0.3 (e)和WO_3-x/CFs-0.5 (f)的低倍SEM图像(图3(b)~3(f))的插图表示相应样品表面的水滴接触角)；((g)~(i)) WO_3-x/CFs-0.3的高倍SEM图像

CA—Contact angle

Figure 3. Low magnification SEM images of WO_3-x(a), blank CFs (b), WO_3-x/CFs-0 (c), WO_3-x/CFs-0.1 (d), WO_3-x/CFs-0.3 (e) and WO_3-x/CFs-0.5 (f) samples respectively (The insets of Fig.3(b)-3(f) represent water contact angle of the corresponding samples surface); ((g)-(i)) High magnification SEM images of WO_3-x/CFs-0.3

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图 4 WO_3-x/Glas-0.3的SEM图像(图4(a)中插图为催化层表面的水滴接触角)

Figure 4. SEM images of WO_3-x/Glas-0.3 (The inset in Fig. 4(a) is water contact angle on the surface of catalytic layer)

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图 5 (a) WO_3-x粉末、空白CFs、PTFE/CFs和不同WO_3-x/CFs样品的XRD图谱；(b) WO_3-x和WO_3-x/CFs-0.3的紫外-可见吸收光谱图(插图为CFs的紫外-可见吸收光谱)

Figure 5. (a) XRD patterns of WO_3-x powder, blank CFs, PTFE/CFs and different WO_3-x/CFs samples; (b) UV-visible DRS of WO_3-x and WO_3-x/CFs-0.3 (The inset is UV-visible DRS of CFs)

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图 6 WO_3-x/CFs-0、WO_3-x/CFs-0.1、WO_3-x/CFs-0.3和WO_3-x/CFs-0.5的N₂吸附-脱附等温线(a)和孔径分布曲线(b)

Figure 6. N₂ adsorption-desorption isotherms (a) and pore size distribution curves (b) of WO_3-x/CFs-0, WO_3-x/CFs-0.1, WO_3-x/CFs-0.3 and WO_3-x/CFs-0.5

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图 7 WO_3-x和WO₃粉末样品的室温电子顺磁共振(EPR)光谱

g—A factor of a free radical or unpaired electron

Figure 7. Room-temperature electron paramagnetic resonance (EPR) spectra of WO_3-x and WO₃ powder samples

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图 8 (a) WO_3-x/Glas两相体系 (i)、WO_3-x/CFs两相体系(通过将WO_3-x/CFs完全浸入水中获得)(ii)和WO_3-x/CFs三相体系示意图(iii)；(b)粉末WO_3-x与3种不同固载体系的甲烷转化量和甲醇产生量

Figure 8. (a) Schematic illustration of WO_3-x/Glas diphase system (i), WO_3-x/CFs diphase system (which was obtained by completely immersing WO_3-x/CFs in the water) (ii) and WO_3-x/CFs triphase system (iii); (b) Methane conversion and methanol production in WO_3-x powder and three different supporting systems

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图 9 (a) WO_3-x/CFs体系甲烷转化产物生成量及甲醇选择性；(b) H₂O₂浓度对甲烷转化产物生成量与甲醇选择性的影响

Figure 9. (a) Products yield of methane conversion and methanol selectivity in WO_3-x/CFs systems; (b) Effect of H₂O₂ concentration on the production of methane conversion products and methanol selectivity

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图 10 (a) WO_3-x负载量对甲烷转化量、甲醇产生量及其选择性的影响；(b) WO_3-x/CFs三相与WO_3-x/Glas两相体系在不同光照强度下的甲醇产生量

Figure 10. (a) Effects of WO_3-x loading on methane conversion, methanol production and its selectivity; (b) Methanol production of WO_3-x/CFs triphase and WO_3-x/Glas diphase systems under different light intensity

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图 11 (a) WO_3-x/CFs-0.3三相体系的光催化循环稳定性；循环实验前后WO_3-x/CFs-0.3的XRD图谱(b)、SEM图像和水接触角(c)

Figure 11. (a) Photocatalytic cycling stability of WO_3-x/CFs-0.3 triphase system; XRD pattern (b), SEM images and water contact angle (c) of WO_3-x/CFs-0.3 before and after 6 cycles

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图 12 WO_3-x/CFs、WO_3-x/Glas与粉末WO_3-x的瞬态光电流响应谱(a)和室温荧光发射谱(b)

Figure 12. Transient photocurrent response spectra (a) and room temperature fluorescence emission spectra (b) of WO_3-x/CFs, WO_3-x/Glas and powder WO_3-x

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图 13 (a) WO_3-x/CFs、WO_3-x/Glas与粉末WO_3-x体系DMPO/•CH₃和DMPO/•OH加合物的EPR信号；(b) WO_3-x/CFs光催化体系三相反应界面微环境示意图

DMPO—5, 5-dimethyl-1-pyrroline nitrogen oxide

Figure 13. (a) EPR signals of DMPO/•CH₃ and DMPO/•OH adducts in WO_3-x/CFs, WO_3-x/Glas and powder WO_3-x systems; (b) Schematic diagram of triphase reaction interface microenvironment in WO_3-x/CFs photocatalytic system

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表 1 WO_3-x/CFs样品名及其成分配比

Table 1. WO_3-x/CFs sample name and composition ratio

Sample	PTFE dosage/µL	WO_3-x dosage/mg
WO_3-x/CFs-0	0	15
WO_3-x/CFs-0.1	2.5	15
WO_3-x/CFs-0.3	7.5	15
WO_3-x/CFs-0.5	12.5	15
WO_3-x/Glas-0.3	7.5	15
Note: Glas—Indium tin oxide conducting glass.

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表 2 不同WO_3-x/CFs样品的孔结构参数

Table 2. Pore structure parameters of different WO_3-x/CFs samples

Sample	S_BET/(m²·g⁻¹)	V_pore/(cm³·g⁻¹)	Pore size/nm
WO_3-x/CFs-0	8.715	0.023	10.68
WO_3-x/CFs-0.1	10.020	0.035	13.95
WO_3-x/CFs-0.3	12.173	0.042	13.72
WO_3-x/CFs-0.5	8.837	0.019	8.78
Notes: S_BET—BET specific surface area; V_pore—Pore volume.

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表 3 光催化转化甲烷制甲醇的性能比较

Table 3. Performance comparison of photocatalytic conversion of methane to methanol

Photocatalyst	Light irradiation condition	CH₃OH yield/ (μmol·g⁻¹)	Selectivity of CH₃OH/%	Ref.
0.33wt%FeO_x/TiO₂	300 W xenon lamp	1056	90	[7]
Quantum-sized BiVO₄	High-pressure mercury lamp	1100	96.6	[9]
La-doped mesoporous WO₃	Medium-pressure mercury lamp	63	46	[13]
Mesoporous WO₃	Mercury vapor lamp	111	37.4	[14]
0.1wt%Au/ZnO	300 W xenon lamp	4120	63	[18]
BiVO₄/NaNO₂	450 W medium-pressure mercury lamp	18	90	[28]
BiVO₄ microcrystals	300 W xenon lamp	268	85	[29]
BiVO₄	450 W immersion medium-pressure mercury lamp	41.6	51	[30]
WO_3-x/CFs-0.3	300 W xenon lamp	1918.83	76.76	This work

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