CuFe (100)及(110)上合成气制低碳醇碳链增长机理研究

王康明; 张海涛; 李涛

doi:10.14135/j.cnki.1006-3080.20210127003

CuFe (100)及(110)上合成气制低碳醇碳链增长机理研究

doi: 10.14135/j.cnki.1006-3080.20210127003

华东理工大学大型工业反应器工程教育部工程研究中心，上海 200237

详细信息

作者简介:
王康明（1996—），男，安徽淮南人，硕士生，主要研究方向为催化反应工程。E-mail：1561409713@qq.com

通讯作者:
李　涛，E-mail：tli@ecust.edu.cn

中图分类号: TQ032.4
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出版历程
- 收稿日期: 2021-01-27
- 网络出版日期: 2021-04-12

Carbon Chain Growth Mechanism of Higher Alcohols Formation from Syngas on CuFe (100) and (110)

Engineering Research Center of the Large Scale Reactor Engineering and Technology, Ministry of Education, East China University of Science and Technology, Shanghai 200237, China

摘要

摘要: CuFe混合催化剂是一种重要的合成气制低碳醇用催化剂。为深入了解合成气制低碳醇的反应机理，从量子尺度研究了其两个主要表面(100)及(110)上的碳链增长机理。计算发现Cu在Fe(100)及(110)面上倾向于单层聚集分布，CuFe(100)面上CO活化机理为H辅助CO生成CHO，随后逐步加氢生成CH₂O和CH₃O，CH₃O更倾向于生成CH₃OH，其碳链增长方式为CHO插入；CuFe(110)面上CO活化机理与CuFe(100)相同，H辅助CO加氢生成的CHO不断加氢依次生成CH₂O和CH₃O，但CH₃O更倾向于生成CH₃，并进一步与CO耦合完成碳链的增长。
- CuFe /
- 合成气 /
- 低碳醇 /
- 碳链增长 /
- DFT
Abstract: CuFe catalyst is an important catalyst for higher alcohols formation from syngas. In order to gain insight to the reaction mechanism, spin-polarized density functional theory calculations were performed to investigate the growth mechanism of carbon chains on CuFe (100) and (110) surfaces. The calculated results show that Cu atoms prefer to aggregate rather than homogeneously distribute on the Fe(100) and (110) surfaces. With the increase of Cu atoms, the surface energy decreases gradually, indicating that the surface is more stable. The dominant activation mechanism of CO on CuFe(100) surfaces is that H-assisted CO dissociation via CHO intermediate, then the intermediate CHO is progressively hydrogenated to form CH₂O and CH₃O. and CH₃O is dominantly hydrogenated to CH₃OH.The pathway of carbon chain growth is CHO rather than CO insertion. The activation mechanism of CO on CuFe(110) surface is the same as CuFe(100) surface. The pathway of CH₃O formation is that CO+3H→CHO+2H→CH₂O+H→CH₃O. On the contrary of CuFe (100) surface, CH₃ formation is more favorable thermodynamically than CH₃OH formation, which leads to more CH₃ available for CO insertion to form C₂₊ higher alcohols. It provides an idea for improving the production of higher alcohols on CuFe catalyst. If an ingenious structure, such as the step surface, can be designed to have the two advantages of CH₃O on CuFe(110) surface being more inclined to generate CH₃ and the low CHO insertion reaction energy barrier on CuFe(100) surface, the higher alcohols selectivity of CuFe catalyst will be greatly improved.
- CuFe /
- syngas /
- higher alcohol /
- carbon chain growth /
- DFT

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图 1 (a) Fe(100)及(b) Fe(110)表面Cu原子排布

Figure 1. Distribution of Cu atom on (a) Fe (100) and (b) Fe (110) surfaces

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图 2 (a) CuFe(100)与(b) CuFe(110)表面模型及其吸附位

Figure 2. Surface models of (a) CuFe (100) and (b) CuFe (110) and their adsorption sites

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图 3 (a)CuFe(100)及(b)CuFe(110)上所有物种最稳定吸附构型

Figure 3. Most stable adsorption configuration of species on (a) CuFe (100) and (b) CuFe (110) surfaces

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图 4 (a) CuFe (100)与(b) CuFe (110)面上CO活化解离过程涉及反应的势能图与过渡态构型

Figure 4. Potential energy diagram and transition state configuration of the reaction are involved in the CO dissociation process on (a) CuFe (100) and (b) CuFe (110) surfaces

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图 5 (a)CuFe (110)及(b)CuFe(110)面上CH_x, CH_xO, CH_xOH物种形成过程涉及反应的势能图与过渡态构型

Figure 5. Potential energy diagram and transition state configuration of the reaction involved in CH_x, CH_xO, CH_xOH speciation on (a) CuFe (100) and (b) CuFe (110) surfaces

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图 6 (a) CuFe (100)与(b) CuFe (110)面上碳链增长过程涉及反应的势能图与过渡态构型

Figure 6. Potential energy diagram and transition state configuration of the reaction involved in the carbon chain growth process on (a) CuFe (100) and (b) CuFe (110) surfaces

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表 1 不同Cu原子排布的模型表面能

Table 1. Surface energy of model with different Cu atom distribution methods

(100)	E_surf/（J·m⁻²）	(110)	E_surf/（J·m⁻²）
Cu0	6.32	Cu0	7.60
Cu4	5.91	Cu3	7.14
Cu4(2)	5.98	Cu3(2)	7.39
Cu8	5.61	Cu6	6.76
Cu8(2)	5.66	Cu6(2)	6.95
Cu12	5.18	Cu9	6.36
Cu12(2)	5.32	Cu9(2)	6.41
Cu16	4.98	Cu12	5.94

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表 2 CuFe(100)及(110)上所有物种的最稳定吸附位及吸附能

Table 2. Most stable adsorption sites and adsorption energies of species on CuFe (100) and CuFe (110) surfaces

Species	CuFe (100)			CuFe (110)
Species	Adsorption site	E_ads/eV	Bonding atom	Adsorption site	E_ads/eV	Bonding atom
C	Hollow	−7.50	C	LB	−9.07	C
O	Hollow	−6.10	O	LB	−6.23	O
H	Hollow	−2.88	H	TF	−5.28	H
CO	Hollow	−1.61	C	TF	−2.52	C
CHO	b-h-b	−2.28	C;O	TF-LB-TF	−3.93	C;O
CH₂O	Hollow	−3.61	C;O	SB-TF-SB	−4.67	C; O
CH₃O	Hollow	−2.37	O	LB	−4.37	O
COH	Hollow	−3.82	C	LB	−5.09	C
CHOH	Bridge	−3.10	C	LB-TF	−4.06	C
CH₂OH	t-b-t	−2.41	C;O	T-SB-T	−2.72	C;O
CH₃OH	t-h	−1.24	O	T-TF	−2.66	C
CH	Hollow	−6.58	C	LB	−6.78	C
CH₂	Hollow	−4.50	C	LB	−5.23	C
CH₃	Bridge	−2.20	C	TF	−3.72	C
CH₄	Top	−0.38	-	T	-	-
C₂H₆	b-t-b	−0.13	-	TF-T-TF	-	-
CH₃CO	t-b-t	−3.85	C;O	T-SB	−3.48	C;O
CH₃CHO	t-b	−3.58	O	T-SB	−4.16	O

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