Pd/HZ5催化剂金属-酸位点匹配机制及萘加氢性能

doi:10.11949/0438-1157.20251094

摘要/Abstract

摘要：

萘油作为煤焦油在210-230 ^oC区间的馏出物，富含萘及甲基萘等双环芳烃，经催化加氢提质可制备密度＞0.85 g/cm³的煤基多环烷烃高密度燃料。通过调控HZSM-5分子筛的硅铝比与Pd负载策略，系统研究了金属分散度、电子态与酸性位点的协同机制对萘加氢路径的影响。采用直接还原法成功制备出高分散Pd/HZ5催化剂，表征结果表明其Pd平均粒径为3.58 nm，显著小于传统焙烧-还原法制备的催化剂（8.24 nm），且形成了具有缺电子特性的Pd物种。适中的载体酸性不仅促进反应物吸附活化，还通过金属-载体相互作用优化Pd电子结构。在240°C、2 MPa的温和条件下，Pd/HZ5-50催化剂萘加氢转化率达94.5%。动力学研究显示其表观活化能为105 kJ/mol，表现出优异的反应活性。

关键词: 萘, 加氢, Pd贵金属, 分子筛, 催化剂, 金属-酸匹配机制

Abstract:

As a coal tar distillate fraction collected at 210-230 °C, naphthalene oil is rich in bicyclic aromatics such as naphthalene and methylnaphthalene. It can be upgraded via catalytic hydrogenation to produce coal-based polycycloalkane high-density fuels with a density > 0.85 g/cm³. This study designed a series of Pd/HZ5 catalysts by modulating the SiO₂/Al₂O₃ ratio of HZSM-5 and Pd loading strategies to elucidate the metal-acid synergy in naphthalene hydrogenation. A direct reduction method was employed to prepare highly dispersed Pd nanoparticles (average size: 3.58 nm), significantly smaller than those in conventional calcination-reduction catalysts (8.24 nm). Combined characterization revealed that the direct reduction method facilitated the formation of electron-deficient Pd species, enhancing metal-support interactions. The moderate acidity of HZSM-5 not only promoted reactant adsorption but also acted as an electron acceptor to optimize Pd's electronic structure, thereby improving H₂ dissociation and aromatic activation. Under optimized conditions (240°C, 2 MPa), Pd/HZ5-50 achieved the naphthalene conversion to 94.5%. Kinetic studies indicated a lower apparent activation energy (105 kJ/mol) for Pd/HZ5-50, underscoring its superior reactivity.

Key words: naphthalene, hydrogenation, Pd noble metal, molecular sieve, catalyst, metal-acid mechanism

中图分类号:

TQ524

王鸿燕, 王心如, 谭长锐, 乔晓宇, 曹景沛. Pd/HZ5催化剂金属-酸位点匹配机制及萘加氢性能[J]. 化工学报, DOI: 10.11949/0438-1157.20251094.

Hongyan WANG, Xinru WANG, Changrui TAN, Xiaoyu QIAO, Jingpei CAO. Metal-acid site matching mechanism and catalytic performance of naphthalene hydrogenation in Pd/HZ5[J]. CIESC Journal, DOI: 10.11949/0438-1157.20251094.

图/表 16

图1 HZ5-50、0.5 Pd/HZ5-50-C和0.5 Pd/HZ5-50催化剂的XRD谱图

Figure 1 XRD patterns of HZ5-50, 0.5 Pd/HZ5-50-C and 0.5 Pd/HZ5-50 catalysts

图2 不同硅铝比的HZ5催化剂（a）N2吸附-脱附等温线及（b）孔径分布图

Figure 2 (a) N2 adsorption-desorption isotherms and (b) pore size distribution of HZ5 catalysts with different SiO2/Al2O3 ratios

表1 不同硅铝比的HZ5催化剂的孔结构特性

Table 1 Pore textural properties of HZ5 catalysts with different SiO2/Al2O3 ratios

样品	S_BET (m²/g)	S_ext (m²/g)	S_mic (m²/g)	V_total (cm³/g)	V_mic (cm³/g)	D_ava (nm)	Pd^a (wt%)
HZ5-50	353	63	290	0.223	0.131	2.53	-
0.5 Pd/HZ5-25-C	384	58	327	0.227	0.146	2.37	-
0.5 Pd/HZ5-25	360	53	307	0.223	0.137	2.48	0.43
0.5 Pd/HZ5-50-C	336	54	282	0.206	0.128	2.45	0.40
0.5 Pd/HZ5-50	334	59	275	0.223	0.125	2.68	0.45
0.5 Pd/HZ5-80-C	325	59	266	0.388	0.137	4.77	-
0.5 Pd/HZ5-80	334	49	286	0.289	0.142	3.45	0.58

图3 （a）0.5 Pd/HZ5-50-C和（b）0.5 Pd/HZ5-50催化剂的SEM图

Figure 3 SEM images of (a) 0.5 Pd/HZ5-50-C and (b) 0.5 Pd/HZ5-50 catalysts

图4 0.1 Pd/HZ5-50催化剂的TEM图（a）0.1 Pd/HZ5-50-C、（b）0.1 Pd/HZ5-50

Figure 4 TEM of two 0.1 Pd/HZ5-50 catalysts: (a) 0.1Pd/HZ5-50-C and (b) 0.1 Pd/HZ5-50

图5 负载量为0.5-1.0 Pd/HZ5-50催化剂的TEM及粒径分布图（a-a1）1.0 Pd/HZ5-50-C、（b-b1）0.5 Pd/HZ5-50、（c-c1）1.0 Pd/HZ5-50和（d-d1）1.0 Pd/HZ5-50

Figure 5 TEM and particle size distribution of a series of Pd/HZ5-50 catalysts with loadings of 0.5-1.0 wt%: (a-a1) 0.5Pd/HZ5-50-C, (b-b1) 0.5 Pd/HZ5-50, (c-c1) 1.0Pd/HZ5-50-C and (d-d1) 1.0 Pd/HZ5-50

图6 不同硅铝比的Pd/HZ5-50催化剂NH3-TPD图

Figure 6 NH3-TPD curves of a series of Pd/HZ5-50 catalysts with different SiO2/Al2O3 ratios

表2 不同硅铝比Pd/HZ5-50催化剂的酸性质

Table 2 Acidity properties of a series of Pd/HZ5-50 catalysts with different SiO2/Al2O3 ratios

样品	NH₃-TPD 酸量/ (mmol g^-1)			Py-FTIR B/L酸比值
	NH₃-TPD 酸量/ (mmol g^-1)			200 °C	350 °C
	L酸量	B酸量	总酸量	B/L	B/L
0.5 Pd/HZ5-25	5.34	1.97	7.31	7.98	7.46
0.5 Pd/HZ5-50-C	0.91	0.75	1.66	5.64	6.51
0.5 Pd/HZ5-50	1.70	2.39	4.09	5.61	6.36
0.5 Pd/HZ5-80	0.08	0.02	0.10	1.55	2.62

图7 不同硅铝比Pd/HZ5-50催化剂的Py-FTIR图：（a）200 °C；（b）350 °C

Figure 7 Py-FTIR patterns of a series of Pd/HZ5-50 catalysts with different SiO2/Al2O3 ratios: (a) 200 °C; (b) 350 °C

图8 不同负载量的Pd/HZ5-50催化剂的Pd 3d XPS能谱：（a）0.1 Pd/HZ5-50、（b）0.5 Pd/HZ5-50、（c）1.0 Pd/HZ5-50、注:(d)0.5 Pd/HZ5-50-C(c) 1.0 Pd/HZ5-50 and (d) 0.5 Pd/HZ5-50-C

Figure 8 Pd 3d spectra of a series of Pd/HZ5-50 catalysts with different loadings: (a) 0.1 Pd/HZ5-50, (b) 0.5 Pd/HZ5-50,

图9 0.5 Pd/HZ5-50和0.5 Pd/HZ5-50-C催化剂的CO-IR谱图

Figure 9 CO-IR curves of the 0.5 Pd/HZ5-50 and 0.5 Pd/HZ5-50-C catalysts

图10 萘加氢反应活性对比：a）不同硅铝比的HZ5-x、0.5 Pd/HZ5-x-C和0.5 Pd/HZ5-x催化剂；b）不同金属负载量的Pd/HZ5-x-C和Pd/HZ5-x催化剂。反应条件：100 mg萘，50 mg催化剂，20 mL溶剂，1 h，200 oC，2 MPa H2（初始）

Figure 10 Comparison of naphthalene hydrogenation activity: (a) HZ5-x supports with different SiO2/Al2O3 ratios, 0.5 Pd/HZ5-x-C, and 0.5 Pd/HZ5-x catalysts; (b) Pd/HZ5-x-C and Pd/HZ5-x catalysts with different metal loadings. Reaction conditions: 100 mg naphthalene, 50 mg catalyst, 20 mL solvent, 1 h, 200 °C, 2 MPa H2 (initial pressure).

图11 反应温度为160-240 oC下萘加氢反应活性对比：a）0.5 Pd/HZ5-50-C；b）0.5 Pd/HZ5-50。反应条件：100 mg萘，50 mg催化剂，20 mL溶剂，1 h，2 MPa H2（初始）

Figure 11 Comparison of naphthalene hydrogenation activity at a reaction temperature range of 160-240 oC: (a) 0.5 Pd/HZ5-50-C; (b) 0.5 Pd/HZ5-50. Reaction conditions: 100 mg naphthalene, 50 mg catalyst, 20 mL solvent, 1 h, 2 MPa H2 (initial pressure).

图12 氢气反应初始压力为1.0-2.5 MPa下萘加氢反应活性对比：a）0.5 Pd/HZ5-50-C；b）0.5 Pd/HZ5-50。反应条件：100 mg萘，50 mg催化剂，20 mL溶剂，1 h，200 oC。

Figure 12 Comparison of naphthalene hydrogenation activity at a initial H2 pressure range of 1.0-2.5 MPa: (a) 0.5 Pd/HZ5-50-C; (b) 0.5 Pd/HZ5-50. Reaction conditions: 100 mg naphthalene, 50 mg catalyst, 20 mL solvent, 1 h, 200 oC.

图13 （a）Pd/HZ5-50-C和（b）Pd/HZ5-50催化剂在不同温度下萘转化率随时间变化；（c）反应活化能。反应条件:50 mg催化剂,100 mg萘,20 mL溶剂,0.5-2.5 h,2 MPa H2

Figure 13 Naphthalene hydrogenation activity curves of (a) Pd/HZ5-50-C and (b) Pd/HZ5-50 at different temperatures with a reaction time range of 0.5-2.5 h; (c) activation energy. Reaction conditions: 50 mg catalyst, 100 mg naphthalene, 20 mL solvent, 0.5-2.5 h, 2 MPa H2

图14 Pd/HZ5-50催化萘加氢反应机制图

Figure 14 Mechanism of naphthalene hydrogenation catalyzed by Pd/HZ5-50

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