磁性碳基固体酸催化剂的制备及其应用研究

发布时间：2018-03-18 07:54

  本文选题：生物质　切入点：木质纤维素　出处：《中国科学技术大学》2017年硕士论文　论文类型：学位论文

【摘要】：由于化石燃料的枯竭和对燃料需求的增加,开发可再生资源用于生产替代能源和化学品显得日益重要。木质纤维素类生物质以其来源广、储量大、不与人类争粮食等优点,受到人们的关注。木质纤维素类生物质通过化学或生物手段可以转化为许多产品,例如生物燃料(生物柴油、生物乙醇和沼气)和化学品(醋酸、丙酮和乳酸),而现在部分产品可以替代石油的应用。目前,通过酸水解或直接由两级间接转化等预处理手段将木质纤维素中的碳水化合物转化为可溶性单糖,再进一步转化为乙醇等生物燃料和高附加值化学品成为主要的处理过程。固体酸催化剂具有活性高、选择性好、腐蚀性小、催化剂寿命长和易于回收再利用等优点,能够将木质纤维素生物质很好地转化为生物燃料,在水解和预处理过程中替代了许多常规的液体酸。磁性固体酸作为一种复合型的催化剂,不仅具有固体酸的高活性,而且还具有磁分离特性,在水解过程中简化了分离步骤,节约了成本。在本文的研究中,采用共沉淀法合成出Fe3O4粒子,然后通过碳化磺化步骤对磁性粒子进行包裹合成出磁性固体酸Fe3O4/C-SO3H,以催化水解只经简单处理后生物质玉米芯生成的木糖得率为考察目标优化制备条件,通过响应面法对磁性固体酸Fe3O4/C-SO3H的四个制备条件进行模拟优化。利用FT-IR、XRD、VSM、TG/DTG、BET等手段对以上最优制备条件的磁性固体酸Fe3O4/C-SO3H(Fe3O4、Fe3O4/C)进行分析,另对催化剂的循环回收及使用作了初步探讨。并对磁性固体酸催化玉米芯水解进行优化研究及探讨催化机理和过程,提出磁性固体酸催化水解纤维素及半纤维素的机理,为磁性固体酸水解木质纤维素类生物质提供理论基础。(1)首先以NaOH溶液为沉淀剂、在80℃下反应8h的条件下合成出Fe3O4粒子;并以Fe3O4粒子为磁性载体合成出磁性固体酸Fe3O4/C-SO3H,得到的最优条件是碳化温度为450 ℃、碳化时间为3 h、磺化温度为100 ℃、磺化时间为9 h。利用响应面法对磁性固体酸Fe3O4/C-SO3H的四个制备条件进行模拟优化得到的最佳工艺是:碳化温度455 ℃、碳化时间4.8 h、磺化温度107 ℃、磺化时间10.0 h,影响磁性催化剂活性的主次因素为:磺化时间碳化时间碳化温度磺化温度。(2)通过多种分析测试手段对最优制备条件的磁性固体酸催化剂Fe304/C-SO3H(Fe3O4、Fe3O4/C)进行分析得出:饱和磁化强度为7.78Am2/kg、比表面积为4.26 m2/g、粒径约为20 nm、总酸量为1.66 mmol/g及化学式为CH0.689O0.443S0.021Fe0.124。固体酸催化剂能稳定分散在反应体系中,在外部磁场的作用能从反应体系中快速分离,并重复使用多次。(3)催化水解玉米芯得到的最佳反应条件为反应时间应10 h、反应温度140 ℃、催化剂用量1.5g、固液比2:50g/mL(玉米芯含量为0.5g)、木糖得率为51.01%。并总结了磁性固体酸催化木质纤维素的水解过程和机理,对木质纤维素选择性水解产生单糖及催化剂的合成应用提供指导。
[Abstract]:Because of the depletion of fossil fuels and the increasing demand for fuels, the development of renewable resources for the production of alternative energy sources and chemicals has become increasingly important. Lignocellulosic biomass can be converted into many products by chemical or biological means, such as biofuels (biodiesel, bio-ethanol and biogas) and chemicals (acetic acid, acetic acid). Acetone and lactic acid, and now some products can replace the application of petroleum. At present, the carbohydrates in lignocellulose are converted into soluble monosaccharides by acid hydrolysis or direct and indirect conversion. The solid acid catalyst has the advantages of high activity, good selectivity, low corrosion, long catalyst life and easy to recycle and reuse. The lignocellulosic biomass can be converted to biofuel very well. In the process of hydrolysis and pretreatment, many conventional liquid acids have been replaced. Magnetic solid acids, as a composite catalyst, not only have the high activity of solid acids. It also has magnetic separation characteristics, simplifies separation steps and saves cost during hydrolysis. In this paper, Fe3O4 particles are synthesized by coprecipitation method. The magnetic solid acid Fe _ 3O _ 4 / C-SO _ 3H was synthesized by carbonation and sulfonation. The optimum preparation conditions were as follows: the xylose yield of biomass corncob after catalytic hydrolysis was simply treated. Four preparation conditions of magnetic solid acid (Fe3O4/C-SO3H) were simulated and optimized by response surface method. The magnetic solid acid Fe3O4 / C-SO3HNFe3O4Fe3O4Fe3O4Fe3O4 / C was analyzed by means of FT-IR, XRDX, TG- / DTGET, etc. In addition, the recycling and utilization of the catalyst were discussed. The mechanism of magnetic solid acid catalyzed hydrolysis of corn cob was studied, and the mechanism of magnetic solid acid catalyzed hydrolysis of cellulose and hemicellulose was put forward. To provide a theoretical basis for magnetic solid acid hydrolysis of lignocellulosic biomass. (1) firstly, Fe3O4 particles were synthesized by using NaOH solution as precipitant and reacting at 80 鈩，

本文编号：1628648