Catalytic dehydration of glycerol in sub- and supercritical water: a new chemical process for acrolein production
Catalytic dehydration of glycerol in sub- and supercritical water: a new chemical process for acrolein production
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DOI：
10.1039/b506285c
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发表时间：
2006-02-01
期刊：
影响因子：
9.8
通讯作者：
Vogel, H
中科院分区：
文献类型：
--
作者：
Ott, L;Bicker, M;Vogel, H
随着原油和天然气资源在几十年内的枯竭，利用可再生能源作为中间体替代原料的研究变得越来越重要。丙烯醛是化学工业的重要且多用途的中间体，例如用于生产丙烯酸酯、超吸收剂聚合物或洗涤剂。到目前为止，生产路线是用Bi/Mo-混合氧化物催化剂气相氧化丙烯。作为替代方案，丙烯醛可以通过甘油的脱水来生产，甘油作为天然脂肪的基本组分出现，并且在脂肪皂化和生物柴油生产过程中在很大程度上作为副产物积累。在此，使用亚超临界水和超临界水作为反应介质已经显示出甘油脱水的一定潜力，尽管迄今为止已经实现的转化率和丙烯醛选择性对于经济的方法来说并不令人满意。只有加入无机酸才能得到足够的丙烯醛产率。为了避免加剧腐蚀的缺点，研究了添加电解质如硫酸锌对该反应的影响。实验在300-390 ℃、25-34 MPa、10-60 s停留时间和不同量的硫酸锌下在高压活塞流反应器中进行。结果表明，在近亚临界温度下，增加盐的量可以提高甘油的转化率。在360 ℃、25 MPa、470 ppm（g g（-1））硫酸锌和50%转化率下，丙烯醛的最大选择性为75 mol%。活化体积测定为-（274 +/- 65）cm（3）Mol（-1）（在360 ℃、25-34 MPa和790 ppm（g g（-1））硫酸锌下），并且结果表明，硫酸锌的添加导致活化能从150 kJ mol（-1）降低至（140 +/- 12）kJ mol（-1）。
Investigations on using renewables as alternative raw materials for intermediates are becoming more and more important as the crude oil and natural gas resources will be exhausted in a few decades. Acrolein is an important and versatile intermediate for the chemical industry, e.g. for the production of acrylic acid esters, superabsorber polymers or detergents. Up to now, the production route is the gas phase oxidation of propylene with a Bi/Mo-mixed oxide catalyst. As an alternative, acrolein can be produced by the dehydration of glycerol, which appears as a basic component of natural fats and is accumulated to a great extent as a by-product during fat saponification and biodiesel production. Here, the usage of sub- and supercritical water as the reaction media has shown a certain potential for the dehydration of glycerol, although the conversion and acrolein selectivities which have been achieved so far, are not satisfying for an economical process. Only the addition of mineral acid leads to sufficient acrolein yields. To evade the disadvantage of intensifying corrosion, the influence of the addition of electrolytes such as zinc sulfate on this reaction has been investigated. Experiments were conducted in a high pressure plug flow reactor from 300-390 degrees C, 25-34 MPa, 10-60 s residence time and varying amounts of zinc sulfate. It was shown that in the near subcritical temperature, increasing the amount of salt enhances the glycerol conversion. The maximum acrolein selectivity is 75 mol% at 360 degrees C, 25 MPa, 470 ppm (g g(-1)) zinc sulfate and a conversion of 50%. The activation volume was determined to be -(274 +/- 65) cm(3) Mol(-1) (at 360 degrees C, 25-34 MPa and 790 ppm (g g(-1)) zinc sulfate) and it turned out that the addition of zinc sulfate causes a decrease of the activation energy from 150 kJ mol(-1) to (140 +/- 12) kJ mol(-1).