不同醇类对磷钨酸催化超临界醇解液化木屑的影响

曾常伟; 吕建华; 郑怀玉; 陈学榕; 黄彪

不同醇类对磷钨酸催化超临界醇解液化木屑的影响

福建农林大学材料工程学院, 福建福州 350002

基金项目:

教育部高等学校博士学科点专项科研基金 20123515110015

福建省科技重大专项 2014NZ003

详细信息

通讯作者:
黄彪, E-mail: fjhuangbiao@hotmail.com

中图分类号: TQ037
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- 文章访问数: 114
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- PDF下载量: 9
- 被引次数: 0
出版历程
- 收稿日期: 2015-08-28
- 修回日期: 2015-11-18
- 网络出版日期: 2021-01-23
- 刊出日期: 2016-03-30

Effect of solvent on the solvolysis liquefaction of sawdust with phosphotungstic acid under supercritical condition

College of Material Engineering, Fujian Agriculture and Forestry University, Fuzhou 350002, China

Funds:

Specialized Research Fund for the Doctoral Program of Higher Education of China 20123515110015

and Fujian Provincial Science and Technology Major Project 2014NZ003

摘要

摘要: 以可溶解于醇类的磷钨酸为催化剂, 在超临界醇体系下液化木屑, 探讨甲醇、乙醇、正丙醇、异丙醇等不同醇类溶剂对木屑醇解液化的影响, 同时采用FT-IR和GC-MS等对液化产物进行了表征分析.结果表明, 反应压力和溶剂的极性大小对木屑的液化效率以及液化产物影响显著.甲醇、乙醇、正丙醇、异丙醇反应体系的液化率和主要液化产物酯类化合物的含量比率, 分别为54.75%和43.759%、90.29%和23.531%、85.90%和41.761%、89.15%和28.619%, 特别在甲醇体系中, 乙酰丙酸甲酯的含量高达33.374%;在异丙醇体系中酚类化合物可达到24.342%;醛类化合物只出现在甲醇体系中.在正丙醇体系中没有酚类产物, 表明极性最小的正丙醇, 提供很少的H^*, 更不容易将木质素降解.
- 磷钨酸 /
- 超临界 /
- 醇解 /
- 木屑 /
- 液化 /
- 影响
Abstract: Phosphotungstic acid is an efficient, green and highly acidic heterogeneous catalyst. Different from other solid heteropholy acids, phosphotungstic acid is dissoluble in alcohols. This research makes the best use of the physicochemical properties of phosphotungstic acid combining with high solubility of supercritical alcohols. Sawdust was liquefied in the supercritical solvent using phosphotungstic acid as catalyst. The effects of different solvents on the solvolysis liquefaction and the compositions of bio-oil were investigated. Each solvolysis experiment was conducted at 260℃ for 30min in a stainless-steel autoclave, in which 1g of fir sawdust, 0.5g of phosphotungsic acid, 150g of alcohol (such as methanol, ethanol, n-propanol or iso-propanol) were added. The liquefaction products were separated by filtration after quenching the reaction. Then, the filtrate was extracted with n-hexane and separated into light bio-oil and heavy bio-oil after removing the solvent. Simultaneously, the residue, heavy bio-oil and light bio-oil were characterized by Fourier transform infrared (FT-IR) and Agilent 7890A/5975C gas chromatography-mass spectrometry (GC-MS). The results show that the reaction pressure and polarity of alcoholic solvents significantly impact the liquefaction efficiency and liquefaction products. The liquefaction yield using methanol, ethanol, n-propanol and iso-propanol is 54.75%, 90.29%, 85.90% and 89.15%, respectively, while the relative content of main compound esters in liquefaction products is 43.759%, 23.531%, 41.761% and 28.619%, respectively. Especially, the relative content of methyl levulinate in methanol system is 33.374%. The main compounds in liquefaction products using methanol, ethanol, iso-propanol as solvent are esters and phenols, while n-propanol system are esters, ketones and alcohols. Meanwhile, levulinate erster, which is produced through the reaction of cellulose/hemicellulose and alcohols, is detected in the liquefaction products of all four solvents. Phenols is determined in the liquefaction products in iso-propanol system with relative content of 24.342%. The aldehyde compounds only exist in methanol system. The absence of phenols in n-propanol system indicates that its weakest polarity provides less hydrogen radical and may lead to difficult degradation of lignin.
- phosphotungstic acid /
- supercritical /
- alcoholysis /
- sawdust /
- liquefaction /
- effect

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图 1 高压液化实验设备示意图及液化产物分离流程示意图

Figure 1 Sketch of liquefaction and separation experiment

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图 2 不同溶剂在同一条件下的液化率

Figure 2 Yield contrast chart of liquefaction with different solvents under the same condition

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图 3 不同溶剂在同一条件下液化产物轻油和重油质量

Figure 3 Mass comparison of light bio-oil and heavy bio-oil obtained by liquefaction with different solvents

: bio-oil; : light oil; : heavy oil

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图 4 杉木屑(a)、甲醇的液化残渣(b)、乙醇的液化残渣(c)、正丙醇的液化残渣(d) 和异丙醇的液化残渣(e) 以及甲醇的产物重油(f)、乙醇的产物重油(g)、正丙醇的产物重油(h) 和异丙醇的产物重油(i) 的红外光谱谱图

Figure 4 Figure 4 FT-IR spectra of fir sawdust (a), the residue obtained from liquefaction with methanol (b), ethanol (c), n-propanol (d) and iso-isopropanol (e) the heavy oil obtained from liquefaction with methanol (f), ethanol (g), n-propanol (h) and isopropanol (i)

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图 5 碳水化合物转化为乙酰丙酸酯的反应路线

Figure 5 Reaction pathway of carbohydrate to levulinate ester

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表 1 不同溶剂的实际反应温度、压力和液化率

Table 1 Comparison of liquefaction yield with different solvents

Solvent	Methanol	Ethanol	n-propanol	Isopropanol
t /℃	258-260	260-268	258-262	258-262
p / MPa	11.2-11.9	11.2-11.9	5.8-8.6	17.0-17.6
η^a/%	54.75	90.29	85.90	89.15
^a: liquefaction yield determined by the average value of repeated experiments

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表 2 不同溶剂条件下液化产物的组分种类及其GC总含量

Table 2 Major compositions and total relative content in the liquefaction products obtained by different solvents

Reaction solvents	GC content w/%
Reaction solvents	alcohols	aldehydes	ketones	acids	phenols	ethers	esters	others
Methanol	1.041	2.605	1.539	0.961	15.780	0.571	43.759	25.93
Ethanol	0	0	23.398	0	19.873	0	23.531	13.708
n-propanol	13.177	0	14.105	6.445	0	4.031	41.761	11.340
Isopropanol	10.093	0	8.333	0	24.342	0	28.619	13.817

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