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生物催化生物质衍生的糠醛合成糠醇和糠胺

作者:完美论文网  来源:www.wmlunwen.com  发布时间:2020/11/18 14:58:53  

摘要:糠醛是属于杂环类有机化合物,被广泛应用于各种行业(例如化学工业、食品工业和医药工业)。生物质可作为生产糠醛的原料,因为生物质富含有大量的木质纤维素,并且是可再生资源,在自然界中十分丰富,可以称得上是取之不尽,用之不竭。糠胺是一种非常重要的糠醛衍生物。工业上,糠醛的胺化通常用气态氨在二恶烷或醇中作为溶剂在氢化催化剂(主要是镍或钴)以及添加剂上进行。该方法的缺点之一是使催化剂失活。此外已有报道称用电化学还原法可将糠基肟还原成糠胺,但收率相对较低。糠醇是另外一种呋喃基化合物,它可作为生产一些化学成分的中间体以及火箭中的一种自燃物质。目前工业规模生产糠醇通过以糠醛的液相或气相氢化为主,即糠醛在高温和高压下与氢气进行催化加氢。因此,在温和的反应条件下催化生物质衍生的糠醛合成糠醇和糠胺的方法值得挑战。在-。研究结果如下:

首先,采用孔隙结构的石墨(GP)作为载体合成锡基固体酸SO42-/SnO2-GP催化剂。通过利用电镜、XRD、红外、BET吸附的表征方法对制备的SO42-/SnO2-GP和GP进行表征。发现Sn元素负载后并没有改变GP关键化学键,只是增加了结晶度,而且孔体积和孔径扩大为0.039 cm3/g和30.4 nm,从而使得催化剂与底物的接触面积变大,这样可以有效地催化玉米芯和冬笋皮生成糠醛,接着,利用酸化的固体酸催化剂SO42-/SnO2-GP (3.6 wt%)于170 oC、20 min条件下可有效地转化玉米芯为糠醛,其产率可达到48.6%。因此,该固体酸催化剂在催化生物质合成糠醛上是十分的高效。

然后,利用E. coli AT和E. coli CCZU-A13全细胞分别催化制备的糠醛溶液合成糠胺和糠醇。为了有效合成糠胺,对影响生物催化活性的各种参数进行了探究,从而得到了本研究中最适的反应条件为:异丙胺与底物浓度比为4:1 (mol : mol),反应温度为35 oC,反应pH为7.5。除此之外,也发现出金属离子Al3+ (1.5 mM)和表面活性剂TW-80 (10 mM)对生物催化活性有很大的促进作用。在最优条件下,E. coli AT全细胞能在24 h之内将65.0 mM 糠醛转化成糠胺,其分析产率达到75.3%。同时,通过使用SO42-/SnO2-GP和重组E. coli CCZU-A13串联催化的方法实现了生物质到糠醇的合成,并对影响生物催化反应的各种因素进行了探究。最适反应温度、反应pH、Zn2+离子浓度分别为30 oC、6.5和10 mM。在最优条件下,重组E. coli CCZU-A13催化冬笋皮的糠醛溶液(66.0 mM)在2 h内转化为糠醇。可见,在水相体系可利用化学生物法转化生物质合成呋喃基产品。

最后,尝试在水-有机溶剂两相体系催化玉米芯合成糠胺。旨在能更加高效的合成糠胺,在研究中也考察了对于实验具有影响的各种参数,发现最适合的反应体系为水-γ-戊内酯两相体系,γ-戊内酯和水的体积比为1:4 (v:v)。糠醛的制备是在两相体系中通过酸化的(3.6 wt%)催化剂转化玉米芯来得到,以75g/L的玉米芯为原料获得90.0mM的糠醛。在170 oC反应20 min的条件下制备糠醛溶液,随后在两相体系中将制备的糠醛溶液通过E. coli AT全细胞生物转化为糠胺。为了有效合成糠胺,研究了在水-γ-戊内酯双相介质中影响生物催化活性的各种参数。最佳生物反应温度、生物反应pH、Al3+离子和PEG-4000浓度分别为35 oC、7.5、0.5 mM和10 mM。在72 h后,糠胺产率为60.3%。可见,在水-γ-戊内酯两相体系中玉米芯通过化学-酶法高效的转化为糠胺。

总之,本研究利用SO42-/SnO2-GP作为固体酸催化剂将生物质转化为糠醛,进一步利用生物催化剂E. coli AT或E. coli CCZU-A13细胞将糠醛有效转化为糠胺或糠醇。可见,本研究成功地转化生物质高效合成呋喃基产品。

关键词:SO42-/SnO2-GP;糠醛;E. coli AT;E. coli CCZU-A13; 糠醇;糠胺

Abstract: Furfural is a heterocyclic organic compound that is widely used in various industries (e.g., chemical industry, food industry, and pharmaceutical industry). Biomass can bee used as the raw material for furfural production, because biomass is rich in a large amount of lignocellulose. It is a renewable and inexhaustible resource. Furfurylamine is a very important derivative of furfural. Industrially, the amination of furfural is usually carried out using gaseous ammonia in dioxane or alcohol as solvent on the hydrogenation catalyst (mainly nickel or cobalt) and additives. One of the disadvantages of this method is the deactivation of the catalyst. In addition, there have been reports that electrochemical reduction can reduce furfural oxime to furfurylamine, but the yield is relatively low. Furfurylalcohol is also furan-based chemical. It can be used as an intermediate in the production of some chemicals and a spontaneous combustion substance in rockets. At present, industrial-scale production of furfurylalcohol is mainly based on the liquid or gas phase hydrogenation of furfural, that is, furfural is catalytically hydrogenated with hydrogen at high temperature and high pressure. Therefore, the methods of converting biomass-derived furfural to furfurylalcohol and furfurylamine deserve the challenge under mild reaction conditions. In this study, it was the first attempt to use SO42-/SnO2-GP as solid acid for converting biomass into furfural, and the prepared furfural was effectively transformed into furfurylalcohol an furfurylamine by recombinant E. coli CCZU A13 harboring reductase and E. coli AT whole cells, respectively. The research results were obtained as follows:

Firstly, the graphite (GP) with pore structure was used as a new carrier to synthesize tin-based solid acid SO42-/SnO2-GP catalyst. The prepared SO42-/SnO2-GP and GP were characterized by electron microscopy, XRD, FTIR, and BET adsorption characterization methods. It was found that Sn element loading did not change the key chemical bonds of GP, but only increased the crystallinity. The pore volume and pore diameter expanded to 0.039 cm3/g and 30.4 nm, so that the contact area between the catalyst and the substrate became larger, which could effectively catalyze corncob and bamboo shoot shell into furfural. In addition, the acidified solid acid catalyst SO42-/SnO2-GP (3.6 wt%) could effectively convert corncob to furfural at 170 oC for 20 min. The furfural yield could reach 52.0%. Therefore, the solid acid catalyst could be very efficient in catalyzing the synthesis of furfural from biomass.

Secondly, the prepared furfural solution was biologically converted into furfurylamine and furfurylalcohol using E. coli AT and E. coli CCZU-A13 whole-cells, respectively. To effectively synthesize furfurylamine, various parameters that had significant influence on the biocatalytic activity were also explored, so that the optimum reaction conditions in this study were: the concentration ratio of isopropylamine to substrate was 4:1 (mol : mol), and the reaction temperature was 35 oC, the reaction pH was 7.5. Moreover, metal ion Al3+ (1.5 mM) and surfactant TW-80 (10 mM) could greatly promote the biocatalytic activity of whole cells. Under optimal conditions, E. coli AT whole cells could convert 65.0 mM biomass-derived furfural to furfurylamine within 24 h, and its yield reached 75.3%. In addition, tandem catalysis with SO42-/SnO2-GP and recombinant E. coli CCZU-A13 was used to convert biomass into furfurylalcohol, and various factors affecting the biocatalytic activity were investigated. The optimal bioreaction temperature, bioreaction pH, and Zn2+ ion concentration were 30 oC, 6.5, and 10 mM, respectively. Under optimal conditions, the recombinant E. coli CCZU-A13 could completely catalyze bamboo shoot shell-derived furfural (66.0 mM) to furfurylalcohol within 2 h.

Finally, corncob was attempted to synthesize furfurylamine in the organic solvent-water biphasic system.

Key words: SO42-/SnO2-GP; Furfural; E. coli AT; E. coli CCZU-A13; Furfuryl alcohol; Furfurylamine

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