费托合成铁基催化剂的性能研究
发布时间：2019-05-30 10:38
【摘要】：原油资源的减少和环境问题引起了全世界的关注,寻找生产日用化学品的可替代过程已成为目前的一个研究热点。费托合成可以将由煤、天然气、生物质制得的合成气转化为优质清洁能源和化工原料(低碳烯烃)来缓解石油危机以及减少环境污染。费托合成的核心是催化剂,主要分为铁基催化剂和钴基催化剂。相比于钴基催化剂,铁基催化剂更便宜且应用范围更广。对铁基催化剂的催化活性、选择性以及失活的基础性研究具有一定的科学性和重要性。本文主要研究了载体和助剂(K、Na和S)对铁基催化剂性能的共同作用,阐述了影响反应性能的关键因素。为了制备高活性、高稳定性以及高低碳烯烃选择性的催化剂,本文主要采用浸渍法制备了铁基催化剂。利用SiC负载的铁基催化剂研究了碱金属对费托合成催化剂性能的影响,并通过改变还原气氛、反应温度以及反应压力进一步考察了评价条件对催化剂性能的影响。研究结果发现,适量的K能够提高催化剂的活性,抑制甲烷的生成,提高低碳烯烃的选择性。通过改变评价条件发现,H2活化的催化剂活性最高。反应温度升高,催化剂活性升高,烷烃的选择性升高,但是低碳烯烃的选择性并没有随着温度的升高而升高。反应压力升高,催化剂活性升高,低碳烯烃的选择性降低,但是CO2和低碳烷烃的选择性变化不明显。通过使用不同的载体研究了载体对K修饰的铁基催化剂性能的影响。结合实验数据和表征结果(BET、XRD、TEM、XPS、TMS、TG、FTIR和H2-TPR),结果发现SiC负载的催化剂的活性以及烯烷比(O/(O+P))有了明显的提升,而γ-Al2O3和SiO2负载的催化剂在加入K助剂之后活性没有明显的变化。AC和TiO2负载的铁基催化剂由于K的加入抑制了催化剂的还原,活性反而下降。K修饰的非负载型催化剂CO的转化率最高但是失活很严重。催化剂的失活主要是由于K助剂诱导的碳沉积以及相态的转移。通过水热法制备了碳硅复合材料,然后利用其作载体制备了一系列的铁基催化剂。不同于传统的SiO2负载的催化剂,该催化剂中Fe和SiO2之间没有明显的相互作用。与SiO2相比,该碳硅复合材料负载的铁基催化剂的活性更高。为了得到高选择性的低碳烯烃,仅仅使用K或Na助剂是不够的,因为K和Na在提高低碳烯烃的选择性的同时还促进了链增长从而形成长链烃。实验证明S助剂在不升高甲烷选择性的同时可以有效增加短链烃(C2-C4)的选择性。所以将碱金属K和Na与S助剂结合,在一定的反应条件下可以有效的提高低碳烯烃的选择性。
[Abstract]:The reduction of crude oil resources and environmental problems have attracted worldwide attention, and the search for alternative processes for the production of daily chemicals has become a hot research topic at present. Fischer synthesis can convert syngas made from coal, natural gas and biomass into high quality clean energy and chemical raw materials (low alkenes) to alleviate the oil crisis and reduce environmental pollution. The core of Fischer's synthesis is catalyst, which is mainly divided into iron-based catalyst and cobalt-based catalyst. Compared with cobalt-based catalysts, iron-based catalysts are cheaper and more widely used. It is scientific and important to study the catalytic activity, selectivity and deactivation of iron-based catalysts. In this paper, the interaction of supports and auxiliaries (K, Na and S) on the performance of iron-based catalysts was studied, and the key factors affecting the reaction performance were described. In order to prepare catalysts with high activity, high stability and high and low olefine selectivity, iron-based catalysts were prepared by impregnation method. The effect of alkali metal on the performance of Fischer synthesis catalyst was studied by using SiC supported iron-based catalyst, and the effects of evaluation conditions on the performance of Fischer synthesis catalyst were further investigated by changing the reduction atmosphere, reaction temperature and reaction pressure. The results show that proper amount of K can improve the activity of the catalyst, inhibit the formation of methane and improve the selectivity of low alkenes. By changing the evaluation conditions, it was found that the activity of H _ 2 activated catalyst was the highest. With the increase of reaction temperature, the activity of catalyst increased and the selectivity of alkane increased, but the selectivity of low alkene did not increase with the increase of temperature. With the increase of reaction pressure, the activity of catalyst increased and the selectivity of low alkene decreased, but the selectivity of CO2 and low alkane did not change obviously. The effect of support on the performance of K modified iron based catalyst was studied by using different supports. Combined with the experimental data and characterization results (BET,XRD,TEM,XPS,TMS,TG,FTIR and H2-TPR), it was found that the activity of SiC supported catalyst and the ratio of alkene to alkane (O / (O P) were significantly improved. However, the activity of 纬-Al2O3 and SiO2 supported catalysts did not change obviously after the addition of K promoter. Ac and TiO2 supported iron-based catalysts inhibited the reduction of catalysts due to the addition of K. On the contrary, the activity of K modified unsupported catalyst CO was the highest, but the deactivation was very serious. The deactivation of the catalyst is mainly due to the carbon deposition induced by K promoter and the transfer of phase state. Carbon-silicon composites were prepared by hydrothermal method, and then a series of iron-based catalysts were prepared by using them as supports. Different from the traditional SiO2 supported catalyst, there is no obvious interaction between Fe and SiO2 in this catalyst. Compared with SiO2, the iron-based catalyst supported on the carbon-silicon composite has higher activity. In order to obtain highly selective low olefins, it is not enough to use K or Na auxiliaries, because K and Na not only improve the selectivity of low alkenes, but also promote the chain growth to form long chain hydrocarbons. The experimental results show that S promoter can effectively increase the selectivity of short chain hydrocarbons (C2-C4) without increasing the selectivity of methane. Therefore, the combination of alkali metal K and Na with S auxiliaries can effectively improve the selectivity of low alkenes under certain reaction conditions.
【学位授予单位】：江南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36
[Abstract]:The reduction of crude oil resources and environmental problems have attracted worldwide attention, and the search for alternative processes for the production of daily chemicals has become a hot research topic at present. Fischer synthesis can convert syngas made from coal, natural gas and biomass into high quality clean energy and chemical raw materials (low alkenes) to alleviate the oil crisis and reduce environmental pollution. The core of Fischer's synthesis is catalyst, which is mainly divided into iron-based catalyst and cobalt-based catalyst. Compared with cobalt-based catalysts, iron-based catalysts are cheaper and more widely used. It is scientific and important to study the catalytic activity, selectivity and deactivation of iron-based catalysts. In this paper, the interaction of supports and auxiliaries (K, Na and S) on the performance of iron-based catalysts was studied, and the key factors affecting the reaction performance were described. In order to prepare catalysts with high activity, high stability and high and low olefine selectivity, iron-based catalysts were prepared by impregnation method. The effect of alkali metal on the performance of Fischer synthesis catalyst was studied by using SiC supported iron-based catalyst, and the effects of evaluation conditions on the performance of Fischer synthesis catalyst were further investigated by changing the reduction atmosphere, reaction temperature and reaction pressure. The results show that proper amount of K can improve the activity of the catalyst, inhibit the formation of methane and improve the selectivity of low alkenes. By changing the evaluation conditions, it was found that the activity of H _ 2 activated catalyst was the highest. With the increase of reaction temperature, the activity of catalyst increased and the selectivity of alkane increased, but the selectivity of low alkene did not increase with the increase of temperature. With the increase of reaction pressure, the activity of catalyst increased and the selectivity of low alkene decreased, but the selectivity of CO2 and low alkane did not change obviously. The effect of support on the performance of K modified iron based catalyst was studied by using different supports. Combined with the experimental data and characterization results (BET,XRD,TEM,XPS,TMS,TG,FTIR and H2-TPR), it was found that the activity of SiC supported catalyst and the ratio of alkene to alkane (O / (O P) were significantly improved. However, the activity of 纬-Al2O3 and SiO2 supported catalysts did not change obviously after the addition of K promoter. Ac and TiO2 supported iron-based catalysts inhibited the reduction of catalysts due to the addition of K. On the contrary, the activity of K modified unsupported catalyst CO was the highest, but the deactivation was very serious. The deactivation of the catalyst is mainly due to the carbon deposition induced by K promoter and the transfer of phase state. Carbon-silicon composites were prepared by hydrothermal method, and then a series of iron-based catalysts were prepared by using them as supports. Different from the traditional SiO2 supported catalyst, there is no obvious interaction between Fe and SiO2 in this catalyst. Compared with SiO2, the iron-based catalyst supported on the carbon-silicon composite has higher activity. In order to obtain highly selective low olefins, it is not enough to use K or Na auxiliaries, because K and Na not only improve the selectivity of low alkenes, but also promote the chain growth to form long chain hydrocarbons. The experimental results show that S promoter can effectively increase the selectivity of short chain hydrocarbons (C2-C4) without increasing the selectivity of methane. Therefore, the combination of alkali metal K and Na with S auxiliaries can effectively improve the selectivity of low alkenes under certain reaction conditions.
【学位授予单位】：江南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36
【参考文献】
相关期刊论文 前10条
1 李烁;姚楠;;掺氮碳基材料在费托合成反应中的应用[J];化工进展;2015年11期
2 刘意;刘勇;陈建峰;张q，
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