ZnCrO<sub><i>x</i></sub>/HZSM-5催化合成气直接转化制异构烷烃

王圣; 黄镇; 方越; 秦枫; 徐华龙; 沈伟

ZnCrO_x/HZSM-5催化合成气直接转化制异构烷烃

复旦大学化学系上海市分子催化与功能材料重点实验室, 上海 200433

基金项目:

国家科技重大专项 2017YFB0602204

国家科技部项目 91645201

上海市科委项目 14DZ2273900

详细信息

中图分类号: O643.36
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出版历程
- 收稿日期: 2018-04-02
- 修回日期: 2018-07-06
- 网络出版日期: 2021-01-23
- 刊出日期: 2018-10-10

Direct synthesis of isoalkanes from syngas over ZnCrO_x/HZSM-5 catalyst

Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Department of Chemistry, Fudan University, Shanghai 200433, China

Funds:

the National Science and Technology Key Project of China 2017YFB0602204

the Ministry of Science and Technology of China 91645201

the Shanghai Science and Technology Committee 14DZ2273900

More Information

Corresponding author: SHEN Wei, E-mail:wshen@fudan.edu.cn

摘要

摘要: 分别采用共沉淀法和水热法制备了ZnCrO_x复合金属氧化物和HZSM-5沸石，通过物理混合得到双功能催化剂，实现了合成气一步高选择性制备异构烷烃。采用XRD、TEM、氮吸附和NH₃-TPD等技术对催化剂进行了表征，考察了双功能催化剂中HZSM-5沸石组分硅铝比以及ZnCrO_x/HZSM-5质量比（OX/ZEO mass ratio）对合成气催化转化反应性能的影响。结果表明，随着HZSM-5硅铝比的增加，催化剂酸密度下降，CO转化率略有下降，产物中C₅₊选择性显著提高，异构烷烃比例不断增加。此外，在保证CO转化率的前提下提高双功能催化剂中ZnCrO_x组分的比例，产物中C₅₊的选择性也显著上升。在400 ℃、2.0 MPa、进料空速（GHSV）为3600 mL/（h·g_cat）的条件下，合成气（H₂/CO（volume ratio）=2）转化率达到35%，C₅₊选择性超过44%，且C₅₊中异戊烷比例高达65%。
- 双功能催化剂 /
- 合成气 /
- 酸催化 /
- 异戊烷
Abstract: ZnCrO_x composite oxide and HZSM-5 zeolite were prepared by using the coprecipitation and hydrothermal methods, respectively; after that, a bi-functional ZnCrO_x/HZSM-5 catalyst was obtained through physical mixing of ZnCrO_x with HZSM-5 and used in the direct synthesis of isoalkanes from syngas. The ZnCrO_x/HZSM-5 catalyst was characterized by XRD, TEM, N₂ sorption, and NH₃-TPD and the effects of Si/Al ratio in HZSM-5 and the mass ratio of ZnCrO_x to HZSM-5 (OX/ZEO mass ratio) on the catalytic performance of ZnCrO_x/HZSM-5 in syngas conversion were investigated. The results indicated that with the increase of Si/Al ratio in HZSM-5, the catalyst acid density is decreased, resulting in a lower CO conversion but higher selectivity to C₅₊ products and higher isoparaffin fraction. Moreover, the selectivity to C₅₊ products is significantly increased by increasing the proportion of ZnCrO_x components in the bifunctional catalyst without losing CO conversion. For the syngas conversion over ZnCrO_x/HZSM-5 catalyst under the conditions of 400 ℃, 2.0 MPa, gas hourly space velocity (GHSV) of 3600 mL/(h·g_cat), the conversion of syngas reaches 35%, with a selectivity of 44% to C₅₊ products and an isopentane fraction up to 65% in the C₅₊ products.
- bifunctional catalyst /
- syngas /
- acid-catalyzed /
- isopentane

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图 1 ZnCrO_x(a)和HZSM-5(b)的X射线粉末衍射谱图

Figure 1 XRD patterns of ZnCrO_x(a) and HZSM-5(b)

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图 2 ZnCrO_x和HZSM-5的透射电子显微镜照片

Figure 2 TEM images of ZnCrO_x and HZSM-5

(a) and (b): ZnCrO_x; (c): HZSM-5(20); (d): HZSM-5(40); (e): HZSM-5(80); (f): HZSM-5(160)

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图 3 不同硅铝比HZSM-5的NH₃-TPD谱图

Figure 3 NH₃-TPD profiles of HZSM-5 with different Si/Al ratios

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图 4 不同温度下ZnCrO_x/ HZSM-5(160)的催化反应性能

Figure 4 Catalytic performance of ZnCrO_x/ HZSM-5(160) in syngas conversion at different temperatures reaction conditions: 0.5 g ZnCrO_x/HZSM-5

(mass ratio = 1:1), H₂/CO(volume ratio)=2, p=2.0 MPa, GHSV=3600 mL/(h·g_cat), TOS= 4 h, C_2-4⁼: C_2-4 olefins, C_2-4^o: C_2-4 alkanes, C₅₊: hydrocarbons with more than 5 carbons except aromatics, Ar: aromatics

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图 5 不同硅铝比ZnCrO_x / HZSM-5催化反应产物中的烃类分布

Figure 5 Hydrocarbon distribution for syngas conversion over ZnCrO_x / HZSM-5 with different Si/Al ratios

reaction conditions: 0.5 g ZnCrO_x/HZSM-5 (mass ratio=1:1), H₂/CO(volume ratio)=2, 400 ℃, 2.0 MPa, GHSV=3600 mL/(h·g_cat), TOS=8 h

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图 6 不同OX/ZEO质量比ZnCrO_x/HZSM-5催化反应产物中的烃类分布

Figure 6 Hydrocarbon distribution for syngas conversion over ZnCrO_x/ HZSM-5(160) with different OX/ZEO mass ratios

reaction conditions: 0.5 g ZnCrO_x/HZSM-5(160), H₂/CO = 2(volume ratio), 400 ℃, 2.0 MPa, GHSV= 3600 mL/(h·g_cat), TOS= 8 h

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表 1 ZnCrO_x和HZSM-5样品的物理化学性质

Table 1 Textural properties of the ZnCrO_x and HZSM-5 samples^a

Sample	A_BET/(m²·g^-1)	A_micro/(m²·g^-1)	A_meso/(m²·g^-1)	v_pore/(mL·g^-1)	v_micro/(mL·g^-1)
ZnCrO_x	88	0	88	0.407	0
HZSM-5(20)	342	289	53	0.223	0.135
HZSM-5(40)	356	303	53	0.312	0.135
HZSM-5(80)	375	296	79	0.233	0.126
HZSM-5(160)	363	283	80	0.226	0.121
^a: obtained by N₂ physisorption

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表 2 HZSM-5样品的表面酸性质

Table 2 Surface acidity of H-ZSM-5 samples^a

Sample	t₁/℃	Weak acidity/ (mmol·g^-1)	Weak acidity density /(μmol·m^-2)	t₂ /℃	Strong acidity/ (mmol·g^-1)	Strong acidity density/ (μmol·m^-2)
HZSM-5(20)	172	0.41	1.19	267	0.24	0.70
HZSM-5(40)	169	0.28	0.77	346	0.24	0.67
HZSM-5(80)	158	0.13	0.34	333	0.13	0.33
HZSM-5(160)	152	0.07	0.20	326	0.09	0.25
^a: obtained by NH₃-TPD

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表 3 不同硅铝比ZnCrO_x/HZSM-5的催化反应性能

Table 3 Catalytic performance of ZnCrO_x/ HZSM-5 with different Si/Al ratios

Catalyst	CO conversion x/%	CO₂ selectivity s/%
ZnCrO_x/HZSM-5(20)	39.9	42.0
ZnCrO_x/HZSM-5(40)	38.8	41.8
ZnCrO_x/HZSM-5(80)	37.3	40.6
ZnCrO_x/HZSM-5(160)	36.9	42.6
ZnCrO_x	5.6	42.9
reaction conditions: 0.5 g ZnCrO_x/HZSM-5(mass ratio=1:1), H₂/CO(volume ratio)=2, 400 ℃, 2.0 MPa, GHSV=3600 mL/(h·g_cat), TOS= 8 h

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表 4 不同硅铝比ZnCrO_x/HZSM-5催化反应产物中的C₅₊分布

Table 4 C₅₊ distribution of hybrid ZnCrO_x/HZSM-5 with different Si/Al ratios

Catalyst	C₅₊ distribution/%			i/n ratio
Catalyst	i-C₅	n-C₅	others	i/n ratio
ZnCrO_x/HZSM-5(20)	48.7	13.9	37.4	3.5
ZnCrO_x/HZSM-5(40)	50.2	10.1	39.7	5.0
ZnCrO_x/HZSM-5(80)	56.6	9.7	33.7	5.8
ZnCrO_x/HZSM-5(160)	63.8	6.8	29.4	9.3
reaction conditions: 0.5 g ZnCrO_x/HZSM-5(mass ratio=1:1), H₂/CO(volume ratio)=2, t=400 ℃, p=2.0 MPa, GHSV=3600 mL/(h·g_cat), TOS=8 h

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表 5 不同OX/ZEO质量比ZnCrO_x/HZSM-5的催化反应性能

Table 5 Catalytic performance of ZnCrO_x/HZSM-5(160) with different OX/ZEO mass ratios

OX/ZEO (mass ratio)	CO conversion x/%	CO₂ selectivity s/%
9:1	24.8	37.8
4:1	27.4	37.7
2:1	35.5	41.0
1:1	36.9	42.6
1:2	37.1	43.3
1:4	36.5	45.3
reaction conditions: 0.5 g ZnCrO_x/HZSM-5(160), H₂/CO(volume ratio)= 2, 400 ℃, 2.0 MPa, GHSV=3600 mL/(h·g_cat), TOS=8 h

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表 6 不同质量比ZnCrO_x/HZSM-5催化反应产物中的C₅₊分布

Table 6 C₅₊ distribution for syngas conversion over hybrid ZnCrO_x/HZSM-5 with different OX/ZEO mass ratios

OX/ZEO (mass ratio)	C₅₊ distribution/%			i/n ratio
OX/ZEO (mass ratio)	i-C₅	n-C₅	others	i/n ratio
9:1	47.1	1.8	51.1	25.8
4:1	62.0	10.4	27.6	6.0
2:1	65.4	6.9	27.7	9.4
1:1	63.8	6.8	29.4	9.3
1:2	55.9	3.5	40.6	15.9
1:4	52.9	5.1	42.1	10.5
reaction conditions: 0.5 g ZnCrO_x/HZSM-5(160), H₂/CO(volume ratio)=2, t=400 ℃, p=2.0 MPa, GHSV=3600 mL/(h·g_cat), TOS=8 h

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