本文關(guān)鍵詞： 乙醇 制氫 鈣鈦礦復(fù)合氧化物 合金 積碳 燒結(jié)　出處：《天津大學(xué)》2016年博士論文　論文類(lèi)型：學(xué)位論文

【摘要】：目前,文獻(xiàn)報(bào)道的乙醇水蒸氣重整制氫(SRE)催化劑普遍具有良好的反應(yīng)活性和氫氣選擇性,因此近幾年來(lái)的研究熱點(diǎn)以及亟需解決的核心問(wèn)題是如何提高催化劑的穩(wěn)定性以及降低催化劑成本。本論文選用了過(guò)渡金屬Ni和Co作為催化劑的活性組分,它們有著成本低的天然優(yōu)勢(shì)。在SRE反應(yīng)中,低溫下催化劑表面的碳沉積和高溫下活性組分的燒結(jié)是導(dǎo)致催化劑失活的主要原因。針對(duì)這兩種問(wèn)題,本論文提出了三種設(shè)計(jì)思路以期提高催化劑的穩(wěn)定性:1、向催化劑中添加堿性助劑;2、將催化劑制備成負(fù)載型雙金屬合金催化劑;3、制備高比表面的載體進(jìn)行活性組分的擔(dān)載,考察催化劑的孔道結(jié)構(gòu)與其性能之間的聯(lián)系。首先,通過(guò)檸檬酸一步絡(luò)合的方法制備不同含量鉀摻雜的鈣鈦礦型復(fù)合金屬氧化物L(fēng)a_(1-x)K_xFe_(0.7)Ni_(0.3)O_3(x=0,0.05,0.1)催化劑前驅(qū)體。將還原后的催化劑用于乙醇水蒸氣重整制氫反應(yīng)表現(xiàn)出很好的活性和氫氣選擇性,尤其是還原后的La_(0.9)K_(0.1)Fe_(0.7)Ni_(0.3)O_3催化劑在反應(yīng)溫度為650°C,水醇比為3:1和空速為264000mL?gcat-1?h-1的條件下反應(yīng)30小時(shí)沒(méi)有出現(xiàn)明顯失活。與不摻雜K的催化劑相比,摻雜K的催化劑有著更好的穩(wěn)定性,其原因是K的給電子作用提高了Ni表面的電子云,當(dāng)C2產(chǎn)物在催化劑表面金屬鎳活性位點(diǎn)上吸附時(shí),C-Ni鍵增強(qiáng)而C-C鍵減弱,從而促進(jìn)C-C鍵的斷裂。催化劑抗積碳性能增強(qiáng),提高了穩(wěn)定性。其次,以LaCo_xNi_(1-x)O_3/ZrO_2(x=0,0.3,1)為前驅(qū)體用于SRE反應(yīng)。LaCo_xNi_(1-x)O_3中鈷離子和鎳離子的還原性質(zhì)相近,能在同一個(gè)還原峰內(nèi)同時(shí)從鈣鈦礦結(jié)構(gòu)中還原成金屬態(tài),因此期望用此種方法制備出ZrO_2載體上擔(dān)載的Ni、Co和Ni-Co合金催化劑。這組催化劑在SRE反應(yīng)中表現(xiàn)出很好的活性和穩(wěn)定性。XRD、TPR和TEM等結(jié)果均表明還原后的LaCo_(0.3)Ni_(0.7)O_3/ZrO_2形成了Ni-Co合金顆粒分散在氧化鑭修飾的ZrO_2載體上的結(jié)構(gòu)。雙金屬催化劑由于Ni和Co的協(xié)同作用,在SRE反應(yīng)中有著最好的催化表現(xiàn),包括高活性、高氫氣選擇性及良好的穩(wěn)定性。這種設(shè)計(jì)思路在催化領(lǐng)域有著廣泛的應(yīng)用,這是因?yàn)檩d體的種類(lèi)是可調(diào)變的,同時(shí)鈣鈦礦中A、B位的金屬離子也是可調(diào)變的。最后,通過(guò)檸檬酸一步絡(luò)合法和PS模板法分別制備了Ce_(0.5)Zr_(0.5)O_2和大孔Ce_(1-x)Zr_xO_2(x=0,0.5)作為載體。將氧化鎳負(fù)載在不同孔結(jié)構(gòu)的載體上作為催化劑前驅(qū)體用于乙醇重整制氫反應(yīng)。大孔Ce_(0.5)Zr_(0.5)O_2負(fù)載的鎳催化劑在反應(yīng)中有著最好的催化表現(xiàn),與其他兩個(gè)催化劑相比,活性和穩(wěn)定性最好。
[Abstract]:At present, the reported SRE catalysts for hydrogen production from ethanol steam reforming generally have good reaction activity and hydrogen selectivity. Therefore, in recent years, the research focus and the core problem to be solved is how to improve the stability of the catalyst and reduce the catalyst cost. In this paper, the transition metals Ni and Co are selected as the active components of the catalyst. They have the natural advantage of low cost. In SRE reaction, carbon deposition on the catalyst surface at low temperature and sintering of active components at high temperature are the main reasons leading to the deactivation of the catalyst. In this paper, three kinds of design ideas are proposed to improve the stability of the catalyst: 1 and to add alkaline additives to the catalyst. (2) the catalyst is prepared into a supported bimetallic alloy catalyst; 3. The support with high specific surface was prepared to support the active component, and the relationship between the pore structure and the performance of the catalyst was investigated. Potassium doped perovskite-type composite metal oxide (La_(1-x)K_xFe_(0.7)Ni_(0.3)O_3(x=0) was prepared by citric acid one-step complexation method. The catalyst precursor showed good activity and hydrogen selectivity when the reduced catalyst was used in the steam reforming of ethanol to produce hydrogen. Especially, the reduced La_(0.9)K_(0.1)Fe_(0.7)Ni_(0.3)O_3 catalyst was prepared at 650 擄C. The ratio of water to alcohol is 3: 1 and the space velocity is 264000mL? Gcat-1? Under the condition of h-1, there was no obvious deactivation at 30 hours. Compared with the catalyst without doping K, the catalyst doped with K had better stability. The reason is that the electron cloud on Ni surface is enhanced by the electron transfer of K. When C2 product is adsorbed on the active site of nickel on the catalyst surface, the C-Ni bond increases and the C-C bond weakens. Thus, the fracture of C-C bond is promoted. The resistance to carbon deposition of the catalyst is enhanced, and the stability is improved. Secondly, the LaCoxNitix _ (1-x) / O _ (3 / ZrO _ (2)) / x _ (0) 0. 3 is used to improve the stability of the catalyst. 1) the reduction properties of cobalt ion and nickel ion in SRE reaction. It can be reduced to metal state from perovskite structure at the same time in the same reduction peak, so it is expected that Ni supported on ZrO_2 carrier can be prepared by this method. Co and Ni-Co alloy catalysts. This group of catalysts showed good activity and stability in SRE reaction. The results of TPR and TEM show that the reduced LaCoS 0.3NiS is 0.7). O _ 3 / ZrO _ 2 formed the structure of Ni-Co alloy particles dispersed on ZrO_2 support modified by lanthanum oxide. The bimetallic catalyst was coordinated by Ni and Co. It has the best catalytic performance in SRE reaction, including high activity, high hydrogen selectivity and good stability. This design idea has been widely used in the field of catalysis. This is because the type of carrier is tunable and the metal ions at the Agna B position in perovskite are also tunable. Ce_(0.5)Zr_(0.5)O_2 and macroporous Ce_(1-x)Zr_xO_2(x=0 were prepared by citric acid one-step method and PS template method, respectively. Using nickel oxide supported on different pore structure as catalyst precursor for ethanol reforming to produce hydrogen. O _ 2-supported nickel catalyst has the best catalytic performance in the reaction. Compared with the other two catalysts, the activity and stability are the best.
【學(xué)位授予單位】：天津大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類(lèi)號(hào)】：O643.36;TQ116.2

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