基于鎳基催化劑的合成氣甲烷化研究
發(fā)布時間：2019-06-06 20:20
【摘要】：隨著經(jīng)濟的快速發(fā)展,我國對天然氣的需求逐年增加,而中國的能源結構特點是:"富煤、貧油、少氣"。我國的天然氣供不應求,需要大量進口,費用昂貴。但我國是煤炭大國,并含有豐富的可再生資源—生物質(zhì)。因此,利用相對豐富的煤或生物質(zhì)資源制取天然氣是緩解我國天然氣能源緊張的有效途徑之一。合成氣合成甲烷是天然氣合成工藝的一個關搖技術。本文對合成氣合成甲烷進行了系統(tǒng)研究。首先是CO甲烷化的研究,分別用沉積沉淀法和共沉淀法制備了催化劑Ni/Ti02,研究制備方法對催化劑甲烷化催化性能的影響。發(fā)現(xiàn)采用共沉淀法制備的催化劑Ni/Ti02的整體催化性能要明顯優(yōu)于沉積沉淀法所制備的催化劑,這主要是因為共沉淀法制備的催化劑具有更大的比表面積和更多的活性位數(shù)量,且活性組分Ni在載體上高分散度。然后采用上文所述的共沉淀法制備了催化劑:Ni/Al_2O_3、Ni/Zr02、Ni/Ce02,發(fā)現(xiàn)三種催化劑在低溫下的活性排序為:Ni/Al_2O_3Ni/Zr02Ni/Ce02,催化劑Ni/Al_2O_3表現(xiàn)了最佳的催化活性和良好穩(wěn)定性。在P=1MPa,GHSV=20000ml/g.h,H_2/CO=3,T=380℃的反應條件下,催化劑Ni/Al_2O_3的CO轉(zhuǎn)化率和CH4選擇性分別達到了 100%和94.5%。表征結果顯示活性組分Ni的分散度是影響不同載體Ni基催化劑甲烷化催化活性的主要因素,Ni的分散度越高,催化劑的催化活性越好。接著挑選CO甲烷化研究中催化性能最好的催化劑Ni/Al_2O_3進行H_2S對甲烷化的影響研究。在 P=1MPa,GHSV=20000ml/g.h,H_2/CO=3,T=440℃,不同 H_2S含量(0,100ppm和200ppm)的反應條件下,對比催化劑的穩(wěn)定性,研究發(fā)現(xiàn)H_2S的存在會大大降低催化劑的穩(wěn)定性,且H_2S的濃度越高,催化劑的穩(wěn)定性越差。當H_2S的濃度為200ppm時,催化劑Ni/Al_2O_3失活很快,僅反應了 5小時就完全失活。最后將分子篩MCM-41引入催化劑載體進行C02甲烷化的研究,采用沉積沉淀法制備催化劑Ni/MCM-41,發(fā)現(xiàn)催化劑Ni/MCM-41具有較好的CO_2催化效果,反應溫度為260-460℃的條件下,催化劑的CO_2轉(zhuǎn)化率和CH4選擇性都隨著TTT溫度的增加而增大,但隨著空速的增加而降低。壓力的增加可以大幅度提高催化劑Ni/MCM-41的催化性能,CO轉(zhuǎn)化率和CH4選擇性的最大值分別從常壓的73.3%、98.5%增大到1.5MPa壓力的91.2%、99.6%。同時發(fā)現(xiàn)助劑Ce02的添加也能改善催化劑Ni/MCM-41的催化活性,催化劑整體性能隨著助劑Ce02添加量的增加而不斷提高,且催化劑Ni/20%CeO_2-MCM-41表現(xiàn)出了最佳的催化劑活性,常壓下,C02轉(zhuǎn)化率和CH4選擇性分別達到85.6%和99.8%。但隨Ce02的繼續(xù)增加,催化活性反而降低。
[Abstract]:With the rapid development of economy, China's demand for natural gas is increasing year by year, and China's energy structure is characterized by: the "rich coal, lean oil and less gas". The supply of natural gas in our country is in short supply, which requires a large amount of import and is expensive. But China is a big coal country and contains rich renewable resources and biomass. Therefore, using relatively rich coal or biomass resource to make natural gas is one of the effective ways to relieve the energy of natural gas in China. Synthesis of methane from synthesis gas is an important technology for natural gas synthesis. This paper systematically studies the synthesis of methane from synthesis gas. The catalyst Ni/ Ti02 was prepared by the deposition and precipitation method, and the effect of the preparation method on the catalytic performance of the catalyst was studied. It is found that the overall catalytic performance of the catalyst Ni/ Ti02 prepared by the co-precipitation method is better than that of the catalyst prepared by the deposition precipitation method, which is mainly because the catalyst prepared by the coprecipitation method has a larger specific surface area and a larger number of active sites, and the active component Ni has a high degree of dispersion on the support. The catalyst: Ni/ Al _ 2O _ 3, Ni/ Zr02, Ni/ Ce02 was prepared by the co-precipitation method as described above. The activity of three catalysts at low temperature was found to be: Ni/ Al _ 2O _ 3Ni/ Zr02Ni/ Ce02, and the catalyst Ni/ Al _ 2O _ 3 exhibited the best catalytic activity and good stability. The CO conversion and CH4 selectivity of the catalyst Ni/ Al _ 2O _ 3 reached 100% and 94.5% respectively under the reaction conditions of P = 1 MPa, GHSV = 20000 ml/ g. h, H _ 2/ CO = 3, T = 380 鈩，
本文編號：2494570
[Abstract]:With the rapid development of economy, China's demand for natural gas is increasing year by year, and China's energy structure is characterized by: the "rich coal, lean oil and less gas". The supply of natural gas in our country is in short supply, which requires a large amount of import and is expensive. But China is a big coal country and contains rich renewable resources and biomass. Therefore, using relatively rich coal or biomass resource to make natural gas is one of the effective ways to relieve the energy of natural gas in China. Synthesis of methane from synthesis gas is an important technology for natural gas synthesis. This paper systematically studies the synthesis of methane from synthesis gas. The catalyst Ni/ Ti02 was prepared by the deposition and precipitation method, and the effect of the preparation method on the catalytic performance of the catalyst was studied. It is found that the overall catalytic performance of the catalyst Ni/ Ti02 prepared by the co-precipitation method is better than that of the catalyst prepared by the deposition precipitation method, which is mainly because the catalyst prepared by the coprecipitation method has a larger specific surface area and a larger number of active sites, and the active component Ni has a high degree of dispersion on the support. The catalyst: Ni/ Al _ 2O _ 3, Ni/ Zr02, Ni/ Ce02 was prepared by the co-precipitation method as described above. The activity of three catalysts at low temperature was found to be: Ni/ Al _ 2O _ 3Ni/ Zr02Ni/ Ce02, and the catalyst Ni/ Al _ 2O _ 3 exhibited the best catalytic activity and good stability. The CO conversion and CH4 selectivity of the catalyst Ni/ Al _ 2O _ 3 reached 100% and 94.5% respectively under the reaction conditions of P = 1 MPa, GHSV = 20000 ml/ g. h, H _ 2/ CO = 3, T = 380 鈩，
本文編號：2494570
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