Mo modified Mo-Fe composite catalysts and their catalytic performance in direct coal liquefaction

doi:10.11949/0438-1157.20210237

Abstract

Abstract:

Five kinds of Mo modified Mo-Fe composite catalysts were synthesized by introducing Mo into the precipitation, oxidation and drying stages of Fe catalyst preparation, by which the binding forms of Mo and Fe could be regulated. The catalysts were characterized by XRD, SEM, TEM, BET, XRF, XPS and H₂-TPR. The Shenhua Shangwan coal hydroliquefaction experiment was carried out in a 500 ml autoclave. The results show that the synergistic effect of Mo and Fe promoted the activation of hydrogen and the decomposition of coal, and the activities of Mo modified composite catalysts for direct coal liquefaction were significantly improved. The high distribution of Mo on the surface is beneficial to the transfer of active hydrogen from solvents to asphaltenes, and promotes the conversion of asphalt into oil. Mo co-precipitation with Fe affected the crystal growth of iron-oxygen compounds, with the decrease of the grain size, and the increase of the specific surface area and reducibility. Mo-Fe compound synthesis by introducing Mo into ammonia solution, with uniform distribution of Mo, showed high catalytic activity and the yield of liquefaction oil increased by 4.4%. The impregnation of Mo into Fe-based catalyst did not change the structure of iron-oxygen compound, but the enrichment of Mo on the catalyst surface increased the collision probability with reactants, and the yield of liquefaction oil increased by 5.0%.

Key words: direct coal liquefaction, Mo-Fe composite catalyst, synergetic catalysis, surface distribution, active hydrogen, oil yield

摘要：

分别在Fe催化剂制备的沉淀、氧化和干燥阶段引入Mo合成了五种Mo修饰的钼铁复合催化剂，调控了Mo和Fe的结合形式。利用XRD、SEM、TEM、BET、XRF、XPS和H₂-TPR对催化剂进行表征，在500 ml高压釜内进行神华上湾煤的直接液化实验。结果表明，钼铁协同催化作用促进了氢的活化和煤的分解，Mo修饰的复合催化剂的煤直接液化活性明显提高。Mo在催化剂表层分布有利于活性氢在工业循环溶剂和沥青类物质中的传递，促进沥青转化为油。Mo与Fe共沉淀会影响铁氧化物晶体形成和生长，使晶粒尺寸下降，比表面积和可还原度升高。Mo从氨水中引入形成均匀分散的小晶粒Mo-Fe复合化合物，液化油产率提高4.4%。浸渍引入Mo不改变铁氧化物结构，但Mo富集于催化剂表面提高了与反应物的碰撞概率，液化油产率提高5.0%。

关键词: 煤直接液化, 钼铁复合催化剂, 协同催化, 表层分布, 活性氢, 油产率

CLC Number:

TQ 529.1

Jing XIE, Geping SHU, Geling YANG, Shansong GAO, Hongxue WANG, Hanfeng LU, Yinfei CHEN. Mo modified Mo-Fe composite catalysts and their catalytic performance in direct coal liquefaction[J]. CIESC Journal, 2021, 72(9): 4675-4684.

谢晶, 舒歌平, 杨葛灵, 高山松, 王洪学, 卢晗锋, 陈银飞. Mo修饰的钼铁复合催化剂及其煤直接液化催化性能[J]. 化工学报, 2021, 72(9): 4675-4684.

Figures/Tables 14

Fig.1 Synthesis process of Fe-based catalysts and Mo-Fe composite catalysts

Table 1 Proximate， ultimate and petrographical analyses of Shenhua Shangwan coal

工业分析(质量分数) /%			岩相分析φ/%			元素分析(质量分数)/%
M_ad	A_d	V_daf	Vitrinite	Inertinite	Exinite	C	H	O	N	S
3.89	5.76	36.30	48.8	49.2	0.0	80.70	4.78	13.19	0.95	0.38

Table 2 The properties and ultimate analysis of the recycle solvent

密度/(g/cm³)	芳碳率	供氢指数/(mg/g)	元素分析(质量分数)/%
密度/(g/cm³)	芳碳率	供氢指数/(mg/g)	C	H	S	N	O
0.9905	0.49	18.88	89.490	9.718	0.003	0.021	0.768

Fig.2 SEM images of Fe catalyst and Mo-Fe composite catalysts

Fig.3 TEM images of Fe catalyst and Mo-Fe composite catalysts

Fig.4 XRD patterns of Fe catalyst and Mo-Fe composite catalysts

Table 3 Texture properties， Mo content of catalysts

催化剂	平均晶粒/nm	比表面积/(m2/g)	孔容/(cm3/g)	平均孔径/nm	(Mo/Fe)(XRF)/%	(Mo/Fe)(EDX)/%
Fe-0	14.9	76.0	0.29	15.2	—	—
Mo-Fe-1	12.3	141.6	0.48	13.4	4.94	5.05
Mo-Fe-2	12.1	150.6	0.46	12.1	5.11	1.70
Mo-Fe-3	11.3	133.4	0.43	13.0	5.02	3.86
Mo-Fe-4	15.3	79.5	0.26	12.9	1.51	0.88
Mo-Fe-5	14.9	81.6	0.26	12.6	4.88	10.94

Fig.5 Pore distribution of Fe catalyst and Mo-Fe composite catalysts

Fig.6 Structure diagram of Fe catalyst and Mo-Fe composite catalysts

Fig.7 XPS patterns of Fe and Mo-Fe composite catalysts

Fig.8 H2-TPR patterns of Fe catalyst and Mo-Fe composite catalysts

Table 4 Results of direct coal liquefaction on catalysts

催化剂	转化率(质量分数)/%	氢耗(质量分数)/%	产率(质量分数) /%
催化剂	转化率(质量分数)/%	氢耗(质量分数)/%	气体	水	沥青	油
Fe-0	86.7	4.1	14.9	12.7	7.9	55.3
MoO₃	85.1	3.9	14.4	12.8	6.4	55.4
Mo-Fe-1	87.9	4.5	14.0	13.4	5.3	59.7
Mo-Fe-2	88.0	4.4	13.8	13.1	8.0	57.5
Mo-Fe-3	88.2	4.5	13.9	13.2	7.2	58.4
Mo-Fe-4	87.9	4.4	14.2	13.1	7.7	57.3
Mo-Fe-5	88.2	4.5	13.8	13.3	5.3	60.3

Fig.9 The reaction pathway of direct coal liquefaction

Fig.10 The relationship between oil yield and surface area and surface Mo/Fe ratio of Mo-Fe composite catalysts

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