費托合成鐵基催化劑的性能研究
發(fā)布時間：2019-05-30 10:38
【摘要】：原油資源的減少和環(huán)境問題引起了全世界的關注,尋找生產日用化學品的可替代過程已成為目前的一個研究熱點。費托合成可以將由煤、天然氣、生物質制得的合成氣轉化為優(yōu)質清潔能源和化工原料(低碳烯烴)來緩解石油危機以及減少環(huán)境污染。費托合成的核心是催化劑,主要分為鐵基催化劑和鈷基催化劑。相比于鈷基催化劑,鐵基催化劑更便宜且應用范圍更廣。對鐵基催化劑的催化活性、選擇性以及失活的基礎性研究具有一定的科學性和重要性。本文主要研究了載體和助劑(K、Na和S)對鐵基催化劑性能的共同作用,闡述了影響反應性能的關鍵因素。為了制備高活性、高穩(wěn)定性以及高低碳烯烴選擇性的催化劑,本文主要采用浸漬法制備了鐵基催化劑。利用SiC負載的鐵基催化劑研究了堿金屬對費托合成催化劑性能的影響,并通過改變還原氣氛、反應溫度以及反應壓力進一步考察了評價條件對催化劑性能的影響。研究結果發(fā)現,適量的K能夠提高催化劑的活性,抑制甲烷的生成,提高低碳烯烴的選擇性。通過改變評價條件發(fā)現,H2活化的催化劑活性最高。反應溫度升高,催化劑活性升高,烷烴的選擇性升高,但是低碳烯烴的選擇性并沒有隨著溫度的升高而升高。反應壓力升高,催化劑活性升高,低碳烯烴的選擇性降低,但是CO2和低碳烷烴的選擇性變化不明顯。通過使用不同的載體研究了載體對K修飾的鐵基催化劑性能的影響。結合實驗數據和表征結果(BET、XRD、TEM、XPS、TMS、TG、FTIR和H2-TPR),結果發(fā)現SiC負載的催化劑的活性以及烯烷比(O/(O+P))有了明顯的提升,而γ-Al2O3和SiO2負載的催化劑在加入K助劑之后活性沒有明顯的變化。AC和TiO2負載的鐵基催化劑由于K的加入抑制了催化劑的還原,活性反而下降。K修飾的非負載型催化劑CO的轉化率最高但是失活很嚴重。催化劑的失活主要是由于K助劑誘導的碳沉積以及相態(tài)的轉移。通過水熱法制備了碳硅復合材料,然后利用其作載體制備了一系列的鐵基催化劑。不同于傳統(tǒng)的SiO2負載的催化劑,該催化劑中Fe和SiO2之間沒有明顯的相互作用。與SiO2相比,該碳硅復合材料負載的鐵基催化劑的活性更高。為了得到高選擇性的低碳烯烴,僅僅使用K或Na助劑是不夠的,因為K和Na在提高低碳烯烴的選擇性的同時還促進了鏈增長從而形成長鏈烴。實驗證明S助劑在不升高甲烷選擇性的同時可以有效增加短鏈烴(C2-C4)的選擇性。所以將堿金屬K和Na與S助劑結合,在一定的反應條件下可以有效的提高低碳烯烴的選擇性。
[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 緯-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.
【學位授予單位】：江南大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：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 緯-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.
【學位授予單位】：江南大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：O643.36
【參考文獻】
相關期刊論文 前10條
1 李爍;姚楠;;摻氮碳基材料在費托合成反應中的應用[J];化工進展;2015年11期
2 劉意;劉勇;陳建峰;張q，
本文編號：2488773
本文鏈接：http://sikaile.net/kejilunwen/huaxue/2488773.html
教材專著
