ZnZr/HZSM-5双功能催化剂在合成气与苯烷基化反应中的催化性能

doi:10.16085/j.issn.1000-6613.2020-2582

摘要/Abstract

摘要：

将系列锌锆金属氧化物与HZSM-5分子筛耦合制备成双功能复合催化剂，并将其应用于合成气与苯烷基化反应。研究结果表明，ZnO是合成甲醇的主要活性组分，ZrO₂的加入能够促进ZnO分散，同时其表面具有的氧空位可促进CO的活化，二者结合方式显著影响反应活性。SEM、XPS、CO-TPD等表征结果表明，ZnO与ZrO₂相结合不仅能够提高ZnO的分散度，而且能调控氧化物表面的氧空位浓度，当二者形成固溶体时，锌在氧化锆中的分散度最大，表面氧空位浓度最高，CO吸附量最大，催化活性最高。锌锆结合方式一定时，锌含量是影响催化活性的另一重要因素，n(Zr)/n(Zn)=2的锌锆固溶体与HZSM-5以质量比1∶2耦合表现出最高的催化活性，CO和苯的转化率为34.65%和35.82%时，甲苯和二甲苯的总选择性高达85.24%。

关键词: 苯, 合成气, 烷基化, 双功能催化剂, 氧空位, 甲苯, 二甲苯

Abstract:

Alkylation of benzene with syngas was studied using a bi-functional ZnZr/HZSM-5 catalyst containing zinc oxide (ZnO), zirconium oxide (ZrO₂) and HZSM-5 zeolite. The catalyst was carefully characterized and the results showed that ZnO was the main active component for the synthesis of methanol while the addition of ZrO₂ not only helped the dispersion of ZnO but also generated large amount of oxygen vacancy that was beneficial to the adsorption and activation of CO. The combination of ZnO and ZrO₂significantly affected the catalytic activity, and the highest ZnO dispersion and oxygen vacancy concentration were obtained when the solid solution (ZnZr_yO_x) was formed. The ZnZr₂O_x coupling with HZSM-5 zeolite with the mass ratio of 1∶2 exhibited the best catalytic performance, resulting in benzene conversion of 35.82%, CO conversion of 34.65%, and the total toluene and xylene selectivity of 85.24%.

Key words: benzene, syngas, alkylation, bi-functional catalyst, oxygen vacancy, toluene, xylene

中图分类号:

TQ426

刘海华, 李艳春, 丁传敏, 葛晖, 李学宽, 张玮. ZnZr/HZSM-5双功能催化剂在合成气与苯烷基化反应中的催化性能[J]. 化工进展, 2021, 40(12): 6696-6704.

LIU Haihua, LI Yanchun, DING Chuanmin, GE Hui, LI Xuekuan, ZHANG Wei. Catalytic performance of ZnZr/HZSM-5 bifunctional catalyst for the alkylation of syngas with benzene[J]. Chemical Industry and Engineering Progress, 2021, 40(12): 6696-6704.

图/表 9

图1 锌锆金属氧化物的XRD图

图2 锌锆金属氧化物的SEM和EDS图

图3 不同方法制备锌锆金属氧化物的XPS图

表1 锌锆金属氧化物表面氧物种浓度

催化剂	O_defect结合能/eV	O_lattice结合能/eV	$O d e f e c t O d e f e c t + O l a t t i c e$ 浓度/%
ZrO₂	529~533	528~531	24.46
ZnO-ZrO₂	529~533	528~531	25.32
ZnO/ZrO₂	529~533	528~531	30.46
ZnZr₄O_x	529~533	528~531	38.95

表1 锌锆金属氧化物表面氧物种浓度

催化剂	O_defect结合能/eV	O_lattice结合能/eV	$O d e f e c t O d e f e c t + O l a t t i c e$ 浓度/%
ZrO₂	529~533	528~531	24.46
ZnO-ZrO₂	529~533	528~531	25.32
ZnO/ZrO₂	529~533	528~531	30.46
ZnZr₄O_x	529~533	528~531	38.95

图4 锌锆金属氧化物的CO-TPD

表2 不同双功能催化剂催化合成气与苯烷基化反应的反应物转化率和产物分布

催化剂	X_B	X_CO	S_产物/%								碳平衡
催化剂	X_B	X_CO	T	X	EB	HA	Q₁	Q₂	Q₃	Q₄	C_（CO）	C_（B）
ZrO₂/HZSM-5	4.81	6.21	71.52	6.33	14.04	8.12	34.35	61.56	1.45	3.65	93.23	98.02
ZnO/HZSM-5	15.38	16.06	68.94	14.15	7.07	9.83	42.62	45.18	4.73	7.36	92.49	97.43
ZnO-ZrO₂/HZSM-5	19.43	21.90	62.17	22.36	7.66	7.81	41.29	37.93	8.79	11.99	92.04	97.25
ZnO/ZrO₂/HZSM-5	23.35	23.06	62.61	25.15	6.45	5.83	46.62	35.18	4.93	13.26	91.82	97.32
ZnZr₄O_x/HZSM-5	29.65	30.52	57.98	28.51	7.15	6.36	47.37	34.53	6.24	11.85	92.13	96.38

图5 反应物转化率和产物选择性随反应时间的变化关系图

[T=400℃，PT=3.5MPa，nH2∶CO=2∶1，n(B∶CO)=1∶2，GHSV(S)=2400h-1，GHSV(B)=1.2h-1]

表3 不同Zn含量双功能催化剂催化合成气与苯烷基化的反应物转化率和产物分布

催化剂	X_B	X_CO	S_产物/%								碳平衡
催化剂	X_B	X_CO	T	X	EB	HA	Q₁	Q₂	Q₃	Q₄	C_（CO）	C_（B）
ZnZr₄O_x/HZSM-5	29.65	30.52	57.98	28.51	7.15	6.36	47.37	34.53	6.24	11.85	92.13	96.38
ZnZr₂O_x/HZSM-5	35.82	35.67	58.80	26.44	6.07	8.69	51.71	29.31	6.89	11.08	92.10	97.21
ZnZr₁O_x/HZSM-5	34.02	33.46	58.27	27.13	6.45	8.15	49.89	30.83	9.24	10.57	91.18	96.45

表4 不同比例及装填方式的双功能催化剂催化合成气与苯烷基化的反应物转化率和产物分布

催化剂	X_B	X_CO	S_产物/%								碳平衡
催化剂	X_B	X_CO	T	X	EB	HA	Q₁	Q₂	Q₃	Q₄	C_（CO）	C_（B）
ZnZr₂O_x/HZSM-5（1∶1）	30.1355	36.69	55.65	26.57	7.31	10.47	46.69	33.40	11.01	8.90	93.31	97.24
ZnZr₂O_x/HZSM-5（1∶2）	35.82	35.67	58.80	26.44	6.07	8.69	51.71	29.31	6.89	11.08	92.10	97.21
ZnZr₂O_x/HZSM-5（1∶4）	21.69	26.52	62.33	18.51	10.94	8.22	55.36	23.24	8.72	12.68	93.81	96.58
ZnZr₂O_x-HZSM-5（1∶2）	5.29	22.83	70.75	11.17	11.77	6.31	17.08	57.35	6.58	18.99	92.16	98.77

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