纳微尺度层状MgAl固体碱催化解聚木质素磺酸钙制取含氧化合物的研究

doi:10.7503/cjcu20190318

摘要/Abstract

摘要：

在水热合成体系中引入羟基化合物制备纳微尺度层状镁铝水滑石前驱体(MgAl-LDHs), 通过正交实验优化合成工艺参数, 焙烧后得到固体碱氧化物(MgAlO_x); 采用X射线衍射(XRD)、扫描电子显微镜(SEM)和二氧化碳程序升温脱附(CO₂-TPD)对水滑石前驱体及固体碱氧化物进行晶相、形貌和碱度表征, 对MgAlO_x解聚木质素磺酸钙(CLS)的催化性能进行评价, 采用气相色谱(GC)、气相色谱-质谱联用(GC-MS)和凝胶渗透色谱(GPC)对反应后气、液和固三相产物组成规律进行分析. 结果表明, 在n(Mg)/n(Al)=3, pH=12, 180 ℃, 24 h条件下, 添加15%(体积分数)C₂H₅OH时, 可以制备晶粒尺寸140~230 nm的层状MgAl-LDHs, 在空气气氛下于600 ℃焙烧6 h得到MgAlO_x. 水热体系下固体碱氧化物对木质素磺酸钙解聚的优化条件为270 ℃, 4 h, 65% C₂H₅OH, m(MgAlO_x)/m(CLS)=1/2, 此时其气、液和固三相产物的产率分别为4.50%, 58.30%和37.20%, 其中液相产物收率比纯木质素磺酸钙解聚提高了13.30%, 液相产物主要组成为酚类、芳香类、酯类和其它化合物, 含氧化合物总选择性为79.05%(酚类66.06%, 酯类12.99%), 反应后的MgAlO_x经焙烧氧化再生后, 循环使用4次仍具有较高的活性和稳定性.

关键词: 正交实验, 镁铝水滑石, 木质素磺酸钙, 解聚, 含氧化合物

Abstract:

The MgAl layered hydrotalcites(MgAl-LDHs) precursors with submicron-scale were synthesized by introducing ethanol into hydrothermal synthesis method. The synthesis process parameters were optimized by orthogonal experiment, and then the composite metal oxide(MgAlO_x) was obtained after the calcination process. The crystal phase, morphology and alkalinity of both hydrotalcite precursors and solid base oxides were characterized by means of X-ray diffraction(XRD), scanning electron microscopy(SEM) and the temperature-programmed desorption of CO₂(CO₂-TPD), respecitively. Finally, the catalytic performance of MgAlO_x was evaluated by the depolymerization test of calcium lignosulfonate. The products including solid, liquid, gas three phases, were analyzed by gel permeation chromatography(GPC), gas chromatography/mass spectrometry(GC-MS) and gas chromatography(GC). The results indicated that 140—230 nm of MgAl-LDHs were regulated by adding 15%(volume fraction) C₂H₅OH to the hydrothermal system, the optimal synthesis condition considered from relative crystallinity was n(Mg)/n(Al)=3, pH=12 and the temperature of 80 ℃ for 24 h. the MgAlO_x obtained after the calcination of MgAl-LDHs at 600 ℃ for 6 h under air atmosphere. The optimal depolymerization of calcium lignosulfonate was 270 ℃, 4 h, the addition of 65%(volume fraction) C₂H₅OH and m(MgAlO_x)/m(CLS)=1/2. The gas-liquid-solid three-phase yield distribution was 4.50%, 58.30% and 37.20% under the above condition, the liquid yields increased by 13.30% with the addition of MgAlO_x, the main components of liquid products were phenolics, aromatics, esters and others. Moreover, the selectivity of oxy-containing compounds was 79.05%(phenolics of 66.06%, esters of 12.99%). Fortunately, MgAlO_x would also keep high reactivity and stability even after four cycles of reactions.

Key words: Orthogonal test, MgAl hydrotalcite, Calcium lignosulfonate, Depolymerization, Oxygen-containing compound

中图分类号:

O643

TrendMD:

韩洪晶,王怡真,李金鑫,薛峰,王海英,张亚男,葛芹,刘艳丽,张梅,陈彦广. 纳微尺度层状MgAl固体碱催化解聚木质素磺酸钙制取含氧化合物的研究. 高等学校化学学报, 2019, 40(11): 2322.

HAN Hongjing,WANG Yizhen,LI Jinxin,XUE Feng,WANG Haiying,ZHANG Yanan,GE Qin,LIU Yanli,ZHANG Mei,CHEN Yanguang. Production of Oxygen-containing Compounds Catalytic from Depolymerization of Calcium Lignosulphonate by Submicron-scale MgAl Solid Base ^†. Chem. J. Chinese Universities, 2019, 40(11): 2322.

图/表 15

Table 1 Factors and levels of orthogonal analyses

Level	n(Mg)/n(Al)	pH	Temperature/℃	Time/h
1	2	8	100	6
2	3	10	140	12
3	4	12	180	24

Fig.1 FTIR spectrum of CLS

Fig.2 SEM image of CLS

Fig.3 XRD spectra of MgAl-LDHs prepared under different conditions

Table 2 Orthogonal experiment results*

Item	n(Mg)/n(Al)	pH	Crystallization temperature/℃	Crystallization time/h	RC(%)
Sample 1	2	10	100	6	51.45
Sample 2	2	11	140	12	59.44
Sample 3	2	12	180	24	83.19
Sample 4	3	10	140	24	67.52
Sample 5	3	11	180	6	89.53
Sample 6	3	12	100	12	91.26
Sample 7	4	10	180	12	62.74
Sample 8	4	11	100	24	74.28
Sample 9	4	12	140	6	78.91
k1	64.69	60.57	72.33	73.30
k2	82.77	74.41	68.62	71.15
k3	71.98	84.45	78.48	75.00
R	18.08	23.88	9.86	3.85

Fig.4 TG-DTG curve of MgAl-LDHs

Fig.5 XRD spectra(A) and SEM images of MgAl(absence of 15% C2H5OH)(B), MgAl-ET(presence of 15% C2H5OH)(C) and MgAlOx(D)

Fig.6 Optimization of process parameters for the depolymerization of CLS

Fig.7 Composition analyses of gas phase products (A) Yield; (B) selectivity.

Table 3 Results of molecular mass distribution of three substances*

Sample	$M ? Z$	$M ? w$	$M ? n$	Polydispersity
1	29391	7917	1300	6.08
2	1127	1051	944	1.11
3	756	886	724	1.22

Table 3 Results of molecular mass distribution of three substances*

Sample	$M ? Z$	$M ? w$	$M ? n$	Polydispersity
1	29391	7917	1300	6.08
2	1127	1051	944	1.11
3	756	886	724	1.22

Fig.8 Yields of various liquid products

Table 4 Relative peak area of liquid products after the depolymerization of CLS

Retention time/min	Liquid product	Relative peak area(%)
Retention time/min	Liquid product	Absence of MgAlO_x	Presence of MgAlO_x
10.62	Phenol(H)	20.04	16.95
13.82	Guaiacol(G)	19.40	16.38
14.14	4-Methyltetrahydro-2H-pyran-2-one(O)	4.57	1.97
15.30	Glutaric acid dimethyl ester(E)	1.19	——
16.26	4-Ethylphenol(H)	4.16	2.99
16.62	Butanedioic acid,1-ethyl ester(E)	——	2.08
16.91	Phenol, 2-methoxy-4-methyl-(G)	4.63	4.14
18.87	Toluene, 2,5-dimethoxy-(A)	1.02	0.64
19.36	Phenol, 4-ethyl-2-methoxy-(G)	10.67	8.99
20.90	Cyclopentanecarboxylic acid, pentyl ester(E)	——	2.99
21.30	Phenol, 2,6-dimethoxy-(S)	12.26	11.85
21.73	Phenol, 2-methoxy-4-propyl-(G)	1.03	0.79
22.21	Succinoic acid, 2-hydroxy-3-methyl-, diethyl ester(E)	——	5.28
22.62	Ethylene glycol di-n-butyrate(E)	——	2.64
23.76	Benzene,1,2,3-trimethoxy-(A)	3.11	2.96
24.73	Ethanone, 1-(4-hydroxy-3-methoxyphenyl)-(E)	3.89	3.97
25.71	Toluene, 3,4,5-trimethoxy-(A)	6.21	5.09
28.44	Homovanillyl alcohol(O)	0	0.71
30.39	Ethanone, 1-(4-hydroxy-3,5-dimethoxyphenyl)-(A)	7.77	9.42

Fig.9 Catalytic performance for the cycling use of MgAlOx

Fig.10 SEM images of the spent MgAlOx(A) and the regenerated MgAlOx(B)

Fig.11 XRD spectra(A) and CO2-TPD curve(B) of different MgAlOx a. Fresh MgAlOx; b. regenerated MgAlOx; c. spent MgAlOx.

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