活化过程对Ni-Fe催化剂的结构及二硝基甲苯催化加氢性能的影响

doi:10.7503/cjcu20140091

摘要/Abstract

摘要：

采用Fe粉替代Zn粉制备了Ni-Fe催化剂, 探讨了醋酸活化过程对催化剂微观结构及催化二硝基甲苯(DNT)加氢制备甲苯二胺(TDA)催化性能的影响. 实验结果表明, 醋酸溶液的活化脱除了催化剂制备过程中生成的Fe₂(OH)₃Cl和未反应的Fe单质. 活化时间的延长导致催化剂中Fe元素和活性组分Ni的含量逐渐增大, 催化剂中Fe元素的存在导致Ni呈现富电子状态. 随着活化时间(0.5~2 h)的延长, Ni-Fe催化剂中金属Ni的分散度和化学氢吸附量逐渐增大, 原料DNT的转化率变化不大, 而产品TDA的选择性逐渐升高; 随着活化时间的进一步延长, 金属Ni的分散度和化学氢吸附量逐渐减小, 产品TDA的选择性逐渐降低. 活化时间为2 h时制备的Ni-Fe催化剂加氢活性最高, DNT的转化率和TDA的选择性分别达到了99.9%和99.8%. 通过对产物组成的分析可知, 在二硝基甲苯加氢过程中生成了4种中间体, 通过逐步加氢生成甲苯二胺.

关键词: 二硝基甲苯, 甲苯二胺, Ni-Fe, 催化剂, 液相加氢

Abstract:

Ni-Fe catalysts were prepared via Fe substitution in a NiCl₂ solution and used in the liquid phase hydrogenation of dinitrotoluene(DNT) to toluenediamine(TDA). The influences of activation time of treatment by acid solution on the catalytic performance and the microstructure of Ni-Fe catalysts were investigated. The results showed that during acid activation treatment, Fe₂(OH)₃Cl formed in the substitution process and part of iron component are removed on the solid catalyst. With increasing of activation time, the content of Fe element decrease gradually and the content of Ni element increased gradually on the catalysts. With the activation time increased from 0 to 2 h, the dispersion of Ni active species and the H₂ chemical absorption increase, and the catalytic activity is enhanced gradually. The 2 h-activated Ni-Fe catalyst exhibited the highest performance with the DNT conversion of 99.9% and the TDA selectivity of 99.8%. Further increasing activation time from 2 h to 4 h, the catalytic activity began to decrease. In addition, it is found that TDA is formed step by step from four kinds of intermediates which are found during the progress of dinitrotoluene hydrogenations.

Key words: Dnitrotoluene, Toluenediamine, Ni-Fe, Catalyst, Liquid phase hydrogenation

中图分类号:

O643.38

TrendMD:

于智慧, 闫泽, 范辉, 李忠. 活化过程对Ni-Fe催化剂的结构及二硝基甲苯催化加氢性能的影响. 高等学校化学学报, 2014, 35(10): 2227.

YU Zhihui, YAN Ze, FAN Hui, LI Zhong. Activation Process on Ni-Fe Catalyst and the Hydrogenation of Dinitrotoluene^†. Chem. J. Chinese Universities, 2014, 35(10): 2227.

图/表 9

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Catalyst	2θ/(°)	FWHM/(°)	Particle size/nm
Ni-Fe-0.5	44.23	0.668	12.70
Ni-Fe-1	44.19	0.639	13.31
Ni-Fe-2	44.30	0.817	11.38
Ni-Fe-3	44.23	0.603	14.06
Ni-Fe-4	44.06	0.564	15.04

Catalyst	2θ/(°)	FWHM/(°)	Particle size/nm
Ni-Fe-0.5	44.23	0.668	12.70
Ni-Fe-1	44.19	0.639	13.31
Ni-Fe-2	44.30	0.817	11.38
Ni-Fe-3	44.23	0.603	14.06
Ni-Fe-4	44.06	0.564	15.04

Catalyst	Content of Fe(%, mass fraction)	Content of Ni(%, mass fraction)	Total content(%, mass fraction)	Molar ratio of Ni/Fe
Ni-Fe-0.5	10.02	47.11	57.13	4.47
Ni-Fe-1	5.62	50.62	56.24	8.57
Ni-Fe-2	5.86	56.85	62.71	9.23
Ni-Fe-3	5.96	65.48	71.44	10.45
Ni-Fe-4	6.08	69.72	75.80	10.91

Catalyst	Content of Fe(%, mass fraction)	Content of Ni(%, mass fraction)	Total content(%, mass fraction)	Molar ratio of Ni/Fe
Ni-Fe-0.5	10.02	47.11	57.13	4.47
Ni-Fe-1	5.62	50.62	56.24	8.57
Ni-Fe-2	5.86	56.85	62.71	9.23
Ni-Fe-3	5.96	65.48	71.44	10.45
Ni-Fe-4	6.08	69.72	75.80	10.91

Catalyst	Chemical-absorption/ (mmol·g^-1)	Dispersion degree of Ni(%)	Chemical-desorption temperature/℃		Relative content(%)
Catalyst	Chemical-absorption/ (mmol·g^-1)	Dispersion degree of Ni(%)	Peak 2	Peak 3	Peak 2	Peak 3
Ni-Fe-0.5	0.0530	15.2	250.21	308.81	52.7	47.3
Ni-Fe-1	0.0938	27.2	258.71	316.32	48.8	51.2
Ni-Fe-2	0.2277	66.0	281.78	328.00	66.9	33.1
Ni-Fe-3	0.1080	31.4	270.75	310.57	50.7	49.3
Ni-Fe-4	0.1051	30.4	275.70	326.96	56.9	43.1