本文選題：催化劑 + 甲烷　； 參考：《中國(guó)石油大學(xué)(華東)》2015年碩士論文

【摘要】：伴隨著世界性能源危機(jī)的日益加劇,原油的重質(zhì)化和劣質(zhì)化問題日益凸顯,并且對(duì)環(huán)境保護(hù)的要求也日趨嚴(yán)格,尋找可再生的替代能源并提高對(duì)重劣質(zhì)原油的加工能力,已成為當(dāng)務(wù)之急。氫氣作為一種高效清潔的能源,不僅可以直接使用,而且是作為煉廠重質(zhì)、劣質(zhì)原料加工重要手段的加氫過程的基礎(chǔ)原料。因此,如何穩(wěn)定高效的制取氫氣便成為亟待解決的問題。本論文基于一種兩步法甲烷裂解制氫過程,采用鎳作為活性金屬,考察常規(guī)載體氧化鋁擔(dān)載的氧化鎳催化劑的反應(yīng)活性,對(duì)引入鎂和鑭元素對(duì)催化劑活性的影響進(jìn)行了探究,并對(duì)催化劑的反應(yīng)-再生循環(huán)性能進(jìn)行了考察。同時(shí),采用水熱合成的方法制備了一種以分子篩為載體的鎳基催化劑,對(duì)其催化甲烷裂解性能進(jìn)行了評(píng)價(jià),并與采用浸漬法制備的分子篩催化劑進(jìn)行了反應(yīng)活性對(duì)比。采用溶膠凝膠法制備了不同負(fù)載量的NiO/Al2O3催化劑,氧化鎳負(fù)載量的不同會(huì)導(dǎo)致鎳物種在催化劑上的存在狀態(tài)不同,隨著氧化鎳負(fù)載量的增加,甲烷轉(zhuǎn)化率逐漸增加,而氫氣選擇性逐漸降低,當(dāng)氧化鎳負(fù)載量為40wt%時(shí)可以獲得較好的甲烷轉(zhuǎn)化率和氫氣選擇性。鎂和稀土元素鈰、鑭、鋯的引入可以提高催化劑的甲烷轉(zhuǎn)化率,鎂的加入與Al2O3載體形成MgAl2O4,從而抑制NiAl2O4的形成,減弱活性組分與載體之間的相互作用,使得催化劑中鎳物種更易被還原。但是過量氧化鎂會(huì)與鎳形成NiMgO2結(jié)構(gòu),使得氧化鎳的還原變難。適量鑭的引入不僅可以減弱催化劑與載體的相互作用,同時(shí)有利于提高活性組分鎳在催化劑表面的分散程度。實(shí)驗(yàn)發(fā)現(xiàn)氧化鎂、氧化鑭添加量分別為5wt%、3wt%時(shí)可以獲得最高的甲烷轉(zhuǎn)化率。采用水熱合成的方法制備了一種鎳基ZSM-5分子篩催化劑。氧化鎳加入量不大于10wt%時(shí)可以形成較好的ZSM-5分子篩晶相,通過紫外可見近紅外光譜儀表征發(fā)現(xiàn),部分鎳物種以骨架鎳原子的形式存在于分子篩的骨架當(dāng)中。與浸漬法制備的催化劑相比,鎳物種在催化劑表面可以得到更好的分散。水熱合成分子篩催化劑的甲烷轉(zhuǎn)化率高于采用浸漬法制備具有相同氧化鎳負(fù)載量的催化劑。對(duì)制備的40wt%NiO-5wt%MgO-3wt%La2O3/Al2O3催化劑進(jìn)行了反再循環(huán)實(shí)驗(yàn)。再生時(shí)間延長(zhǎng)使催化劑的甲烷轉(zhuǎn)化率升高,而氫氣選擇性降低。催化劑經(jīng)歷部分再生后,表面仍將殘留一部分積碳,這部分積碳具有還原性,將消耗表面晶格氧,從而提高氫氣選擇性,但甲烷轉(zhuǎn)化率逐漸降低。提高再生溫度有利于積碳的燃燒,使得催化劑的甲烷轉(zhuǎn)化率升高,但是氫氣選擇性降低。
[Abstract]:With the worsening of the world energy crisis, the problem of heavy and inferior crude oil is becoming more and more serious, and the requirement of environmental protection is becoming more and more strict, so as to find renewable alternative energy and improve the processing capacity of heavy and poor crude oil. It has become a top priority. As a kind of efficient and clean energy, hydrogen is not only used directly, but also as the basic raw material of hydrogenation process, which is an important means of processing heavy and inferior raw materials in refineries. Therefore, how to produce hydrogen stably and efficiently becomes an urgent problem. In this paper, based on a two-step process of methane pyrolysis to produce hydrogen, nickel was used as active metal to investigate the reaction activity of nickel oxide catalyst supported on conventional support alumina, and the effect of introducing magnesium and lanthanum elements on catalyst activity was investigated. The reaction-regeneration cycle performance of the catalyst was also investigated. At the same time, a nickel based catalyst supported on molecular sieve was prepared by hydrothermal synthesis. The catalytic activity of the catalyst was evaluated and compared with that prepared by impregnation method. NiO/Al2O3 catalysts with different loading amounts were prepared by sol-gel method. The different supported amounts of nickel oxide lead to the different states of nickel species on the catalyst. With the increase of the amount of nickel oxide loading, methane conversion increases gradually. The hydrogen selectivity decreases gradually and the methane conversion and hydrogen selectivity can be obtained when the amount of nickel oxide is 40 wt%. The addition of magnesium and rare earth elements cerium, lanthanum and zirconium can increase the methane conversion of the catalyst, and the addition of magnesium can form MgAl _ 2O _ 4 with the support of Al2O3, which inhibits the formation of NiAl2O4 and weakens the interaction between the active components and the support. The nickel species in the catalyst can be reduced more easily. However, excessive magnesium oxide can form NiMgO2 structure with nickel, which makes the reduction of nickel oxide difficult. The addition of proper amount of lanthanum not only weakens the interaction between the catalyst and the support, but also improves the dispersion of nickel on the surface of the catalyst. It is found that the highest methane conversion can be obtained when the addition amount of magnesium oxide and lanthanum oxide is 5 wtwt% and 3 wt% respectively. A nickel-based ZSM-5 molecular sieve catalyst was prepared by hydrothermal synthesis. A good crystalline phase of ZSM-5 molecular sieve can be formed when the amount of nickel oxide is less than 10 wt%. It is found by UV-Vis near infrared spectrometer that some nickel species exist in the framework of molecular sieve in the form of skeleton nickel atom. Compared with the catalyst prepared by impregnation, nickel species can be dispersed better on the surface of the catalyst. The methane conversion of hydrothermal molecular sieve catalyst is higher than that of catalyst with the same amount of nickel oxide supported by impregnation method. The reverse recirculation experiment of the prepared 40wt%NiO-5wt%MgO-3wt%La2O3/Al2O3 catalyst was carried out. The longer the regeneration time, the higher the methane conversion and the lower the hydrogen selectivity. After partial regeneration of the catalyst, a part of carbon will remain on the surface, which is reductive, which will consume lattice oxygen on the surface and improve the selectivity of hydrogen, but the conversion rate of methane will decrease gradually. The increase of regeneration temperature is beneficial to the combustion of carbon deposition, which increases the methane conversion of the catalyst, but decreases the selectivity of hydrogen.
【學(xué)位授予單位】：中國(guó)石油大學(xué)(華東)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：O643.36;TQ116.2

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