一步法制备硼氢化钠水解制氢Co-基催化剂的研究

发布时间：2018-01-31 15:06

本文关键词： 一步法玉米秸秆活性炭催化剂动力学氢气　出处：《青岛科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：随着化石能源的日益枯竭和环境污染的不断加重,可持续清洁能源-氢气的开发受到世界各国的高度关注。氢能是未来的理想能源,可以通过燃烧得到热能,同时也可作为燃料电池原料转化为电能。然而氢气在储存和运输方面的不便,使其在燃料电池方面的应用受到很大的限制。硼氢化钠水解制氢技术由于其供给速率快、生产纯度高、释放条件温和、产物对环境无污染等优点引起国内外研究者的广泛关注。催化剂的制备是硼氢化钠溶液发生水解制氢反应的核心技术。相比于贵金属催化剂的价格昂贵、储量有限等缺点,非贵金属Co-基催化剂以其优良的性能,成为近几年来研究的热点。催化剂的催化性能不仅与催化剂的基本组成有关,还与催化剂的形态结构紧密相关,而催化剂的制备方法正是造成其结构差异的主要原因之一。因此,针对国内外Co-基催化剂的制备需求,寻求制备方法简单、价格低廉且性能高效的Co-基催化剂是当前需要解决的关键问题。本文采用一步法简单、高效制备了玉米秸秆活性炭Co-基制氢催化剂。玉米秸秆活性炭的活化过程与催化剂的高温焙烧过程相结合,一方面减少单元操作,节省焙烧过程能耗；另一方面增强了载体与活性组分之间的相互作用,使催化剂的催化活性得以改善。主要研究内容和研究结果如下：1、通过一步法制备了玉米秸秆活性炭Co-基制氢催化剂,考察了其催化硼氢化钠溶液水解反应的产氢性能,优化了一步法制备工艺条件(炭化温度、炭化时间、活化温度、活化时间),并考察了催化剂的稳定性。研究结果表明,炭化-活化相结合的制备工艺使得Co-基催化剂催化硼氢化钠的产氢性能改善。所述催化剂的最佳制备工艺为：400℃炭化1h,800℃活化2 h,平均产氢速率为1715.2mL·min-1·g-1,瞬时产氢速率最高达2952 mL·min-1·g-1。经11次循环使用后,催化活性仍保持初始活性的51%,具有较高的循环稳定性,可循环用于硼氢化钠水解制氢。2、通过一步法引入助剂Fe和Mn元素制备成双组分催化剂,并对引入其助剂的作用方式进行了探讨分析。结果表明：(1)添加Fe、Mn后,催化剂的平均产氢速率均增至1784 mL·min-1·g-1,尤其是Co-Mn/AC催化剂,其瞬时产氢速率高达3040 mL·min-1·g-1.(2)助剂Fe、Mn的加入使活性组分在载体表面的团聚现象明显减少,活性组分镶嵌到活性炭的孔道内,抑制了活性相的流失。(3)助剂Fe的引入使得在20=44.2°处的特征峰向低角度略有偏移,Fe固溶于Co,晶格发生畸变,引起晶格常数的变化,活性点位增多。(4)助剂Mn的引入使得催化剂中活性组分的晶粒尺寸相比于Co、Co-Fe更小,活性组分的尺寸越小,越具有较大的表面原子比和较高的比表面积,从而提高其催化性能。3、对玉米秸秆活性炭Co/AC催化剂催化硼氢化钠水解体系下的反应动力学进行详细的分析,得到此催化剂的反应活化能为50.2 KJ·mmol-1,其表观水解产氢速率动力学方程的表达式为：r=Ae-50200/(RT)[catalyst]0.48[NaOH]0.49[NaBH4]1.16当NaBH4的浓度小于10wt.%；而当NaBH4的浓度大于10wt.%时,则有r=Ae-50200/(RT)[catalyst]0.48[NaOH]0.49[NaBH4]1.16。
[Abstract]:With the increasing depletion of fossil energy and the worsening of environmental pollution and sustainable development of the clean energy hydrogen is highly concerned by all countries in the world. Hydrogen is an ideal energy in the future, through the combustion heat, but also can be used as fuel cell materials into electricity. However, hydrogen storage and transportation in the inconvenience. The application in fuel cells is limited. Hydrolysis of sodium borohydride due to the supply rate, the production of high purity, the release of mild conditions, attention product without pollution to the environment caused by domestic and foreign researchers. The preparation of catalyst is the core technology of sodium borohydride solution by hydrolysis reaction. Compared to the noble metal catalysts are expensive, disadvantages of limited reserves, non noble metal Co- catalyst for its excellent performance, has become a hot research topic in recent years. Catalytic The catalytic performance of the agent not only basic composition and catalyst, are closely related with the morphological structure of the catalyst, and the catalyst preparation method is one of the main causes of structural differences. Therefore, in view of the domestic and foreign Co- based catalyst preparation requirements for the preparation method is simple, inexpensive and Co- based catalyst high performance is the key problem to be solved. This paper uses a simple step, corn stalk activated carbon Co- based catalysts were prepared. High efficiency corn stalk active carbon activation process and catalyst calcination process combined with a reduction of unit operation, save the energy consumption in the process of roasting; enhances the interaction between the carrier and the the active components on the other hand, the catalytic activity of the catalyst was improved. The main research contents and results are as follows: 1, through one step preparation activity of maize straw Carbon Co- based catalyst for hydrogen production, hydrogen production performance of the catalytic hydrolysis of sodium borohydride solution was investigated, the preparation condition optimization (one-step carbonization temperature, carbonization time, activation temperature, activation time), and the stability of the catalyst was investigated. The results show that the carbon - activated preparation process combination the performance of Hydrogen Production Catalyzed by Co- catalyst boron sodium hydride. The best preparation process for the catalyst: 400 C 800 C 2 1H carbonization, activation of H, the average hydrogen production rate of 1715.2mL - min-1 - g-1, the instantaneous hydrogen production rate of up to 2952 mL - min-1 - g-1. after recycling 11 times after the catalytic activity remains the initial activity cycle 51%, high stability, can be recycled for hydrolysis of sodium borohydride.2, additive Fe and Mn elements for preparing two-component catalyst by one-step method is introduced, and the introduction of the additives was analyzed by the way Analysis. The results showed that: (1) add Fe, Mn, the average hydrogen production rate of catalyst was increased to 1784 mL - min-1 - g-1, especially Co-Mn/AC catalyst, the instantaneous hydrogen production rate of up to 3040 mL - min-1 - g-1. (2) Mn agent Fe, adding the active component was significantly reduced at the reunion the phenomenon of the surface of the carrier, active component embedded into the activated carbon pore, inhibited the loss of active phase. (3) the introduction of additives of Fe makes the characteristic peak at 20=44.2 DEG to the low angle slightly offset, Fe dissolved in the Co lattice distortion caused by the variation of lattice constants, active sites increased. (4) the introduction of additives of Mn makes the grain size of the active component in the catalyst compared to Co, Co-Fe is smaller, the smaller the size of the active component, has the larger surface atomic ratio and high surface area, so as to improve the catalytic performance of.3 catalytic boron corn stalk activated carbon Co /AC hydrogenation catalyst sodium and water The disintegration reaction kinetics system. A detailed analysis, the catalyst reaction activation energy is 50.2 KJ - mmol-1, the apparent expression of hydrolysis hydrogen production rate kinetics equation is: r=Ae-50200/ (RT) [catalyst]0.48[NaOH]0.49[NaBH4]1.16 when NaBH4 was less than 10wt.%; and when the concentration of NaBH4 is higher than 10wt.%, while r=Ae-50200/ (RT) [catalyst]0.48[NaOH]0.49[NaBH4]1.16.

【学位授予单位】：青岛科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ116.2;TQ426

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