柠檬酸复合改性对多环芳烃选择性开环铂/Beta催化剂性能的影响

doi:10.19964/j.issn.1006-4990.2020-0647

摘要/Abstract

摘要：

通过水热处理、柠檬酸处理及其复合处理对Beta分子筛进行后改性,并以改性后的载体制得铂/Beta催化剂。采用X射线衍射（XRD）、X射线荧光光谱仪（XRF）、程序升温脱附（NH₃-TPD）、红外吡啶吸附（Py-IR）、骨架铝核磁共振技术（²⁷Al MAS NMR）及骨架硅核磁共振技术（²⁹Si MAS NMR）等表征了改性前后Beta分子筛的物化性质,并考察了改性前后铂/Beta的多环芳烃选择性开环性能。结果表明,Beta分子筛在柠檬酸处理过程中可同时发生络合脱铝与骨架补铝,实现骨架铝的再分布;Beta分子筛在水热处理过程中优先脱除稳定性相对较低的Si（2 Al）处骨架铝,产生骨架缺陷的同时生成一定比例的二次介孔结构;水热-柠檬酸复合处理影响Beta分子筛骨架补铝及骨架铝再分布的效果,水热处理后Beta分子筛中存在更多的骨架缺陷,促进活性Al（OH）₂⁺物种的骨架补铝作用。当Beta分子筛采用水热-柠檬酸复合处理顺序时,骨架补铝及骨架铝再分布效果显著,样品以中强酸为主,且具有较高的B酸量与L酸量的比值,所制备催化剂的多环芳烃选择性开环活性及稳定性最优。

关键词: Beta分子筛, 柠檬酸处理, 水热处理, 多环芳烃, 选择性开环

Abstract:

Beta zeolites were post modified by hydrothermal treatment,citric acid treatment and duplex treatment,and the Pt/beta catalyst was prepared with the modified support.The physicochemical properties of the the modified and unmodified beta zeolites were characterized by X-ray diffraction（XRD）,X-ray fluorescence spectrometry（XRF）,temperature programmed desorption（NH₃-TPD）,infrared pyridine adsorption（Py-IR）,framework aluminum nuclear magnetic resonance（²⁷Al MAS NMR） and framework silicon nuclear magnetic resonance（²⁹Si MAS NMR）,and the performance of the modified and unmod-ified Pt/beta on selective ring opening of polycyclic aromatic were investigated.The results showed that dealumination and re-alumination of Beta zeolite performed in citric acid treatment,leading to framework Al redistribution.In the process of hydro-thermal treatment,beta zeolite preferentially removed the framework aluminum at Si（2Al）,which had relatively low stability,and produced framework defects and a certain proportion of secondary mesoporous structure.The hydrothermal-citric acid du-plex treatment made a difference to framework aluminum addition and redistribution of beta zeolite.After hydrothermal treat-ment,there were more framework defects in beta molecular sieves,which could promote the framework supplement of active Al（OH）₂⁺ species.When the hydrothermal-citric acid duplex treatment sequence was used for beta zeolite,the effect of frame-work aluminum supplement and framework aluminum redistribution was significant.The sample was mainly medium strong acid with a high ratio of B acid content to L acid content.The as-prepared catalyst had the best selective ring opening activity and stability for polycyclic aromatic hydrocarbons.

Key words: beta zeolite, citric acid treatment, hydrothermal treatment, polycyclic aromatic hydrocarbons, selective ring opening

中图分类号:

O643.36

臧甲忠,马明超,于海斌,范景新,郭春垒,靳凤英. 柠檬酸复合改性对多环芳烃选择性开环铂/Beta催化剂性能的影响[J]. 无机盐工业, 2021, 53(6): 205-211.

Zang Jiazhong,Ma Mingchao,Yu Haibin,Fan Jingxin,Guo Chunlei,Jin Fengying. Effect of citric acid assisted hydrothermal dealumination on performance of Pt/Beta catalysts for selective ring opening of polycyclic aromatic hydrocarbons[J]. Inorganic Chemicals Industry, 2021, 53(6): 205-211.

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Beta分子筛	相对结晶度/%	d₃₀₂/10^-1 nm	n（SiO₂）/n（Al₂O₃）
Beta	100.0	3.941	26.0
At-Beta-1	103.1	3.952	35.6
At-Beta-2	106.5	3.962	44.0
At-Beta-3	105.6	3.962	49.6
At-Beta-4	99.8	3.940	48.2
St-Beta-1	96.4	3.941	26.0
St-Beta-2	94.4	3.940	26.0
St-Beta-3	90.7	3.941	26.0

Beta 分子筛	S_BET/ （m²·g^-1）	S_micro/ （m²·g^-1）	V_total/ （cm³·g^-1）	V_micro/ （cm³·g^-1）	V_meso/ （cm³·g^-1）
Beta	442	344	0.425	0.182	0.243
At-Beta-1	451	347	0.431	0.183	0.248
At-Beta-2	460	351	0.446	0.187	0.259
At-Beta-3	459	351	0.444	0.186	0.258
At-Beta-4	457	348	0.441	0.182	0.259
St-Beta-1	432	331	0.421	0.176	0.245
St-Beta-2	415	314	0.413	0.166	0.247
St-Beta-3	394	302	0.395	0.151	0.244

Beta 分子筛	酸量（NH₃）/ （mmol·g^-1）			酸类型及酸量（Py）/（μmol·g^-1）		B与L 酸量比
Beta 分子筛	总酸量	低温酸量	高温酸量	B	L	B与L 酸量比
Beta	0.568	0.234	0.334	128.7	77.1	1.67
At-Beta-1	0.554	0.197	0.357	132.8	54.2	2.45
At-Beta-2	0.544	0.175	0.369	144.4	33.6	4.30
At-Beta-3	0.541	0.172	0.369	148.1	34.1	4.34
At-Beta-4	0.522	0.173	0.349	130.7	32.8	3.98
St-Beta-1	0.542	0.242	0.300	106.3	134.3	0.79
St-Beta-2	0.523	0.256	0.267	78.9	139.2	0.57
St-Beta-3	0.513	0.262	0.251	67.8	126.3	0.54

Beta 分子筛	S_BET/ （m²·g^-1）	S_micro/ （m²·g^-1）	V_total / （cm³·g^-1）	V_micro / （cm³·g^-1）	V_meso / （cm³·g^-1）
Beta	442	344	0.425	0.182	0.243
At-Beta-2	460	351	0.446	0.187	0.259
St-Beta-2	415	314	0.413	0.166	0.247
At-St-Beta	425	324	0.399	0.164	0.235
St-At-Beta	449	337	0.468	0.171	0.297

Beta 分子筛	酸量（NH₃）/ （mmol·g^-1）			酸类型及酸量（Py）/（μmol·g^-1）		B与L 酸量比
Beta 分子筛	总酸量	低温酸量	高温酸量	B	L	B与L 酸量比
Beta	0.568	0.234	0.334	128.7	77.1	1.67
At-Beta-2	0.544	0.175	0.369	144.4	33.6	4.30
St-Beta-2	0.523	0.256	0.267	78.9	139.2	0.57
At-St-Beta	0.527	0.226	0.301	83.4	89.2	0.80
St-At-Beta	0.532	0.179	0.353	128.7	57.7	2.23

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