本文選題：乙醇　切入點(diǎn)：制氫　出處：《天津大學(xué)》2015年博士論文

【摘要】：乙醇水蒸氣重整制氫的技術(shù)核心是催化劑的研發(fā),文獻(xiàn)報(bào)道的催化劑具有很好的活性和氫氣選擇性,近幾年來(lái)研究重點(diǎn)主要集中在提高催化劑穩(wěn)定性上。低溫下反應(yīng)后積碳沉積和高溫下活性組分燒結(jié)是導(dǎo)致催化劑失活的主要原因。針對(duì)乙醇重整的積碳和燒結(jié)問(wèn)題,本論文提出了兩種催化劑的設(shè)計(jì)思路以期改善催化劑的穩(wěn)定性:一種是選擇具有氧空位的氧化物作為催化劑載體;另一種制備成負(fù)載型雙金屬催化劑,考察了催化劑結(jié)構(gòu)與性能之間的關(guān)系。首先分別利用檸檬酸絡(luò)合法和改性浸漬法制備Ni-La-Ce三元氧化物。制備方法對(duì)催化劑結(jié)構(gòu)影響很大。兩種方法制備的催化劑用于乙醇水蒸氣重整反應(yīng)都能表現(xiàn)出很好的活性和氫氣選擇性,檸檬酸絡(luò)合法制備的催化劑在反應(yīng)溫度為650°C,水醇比為3和空速為180,000 ml·gcat-1·h條件下反應(yīng)8h后催化劑沒(méi)有出現(xiàn)失活,該催化劑能表現(xiàn)出更好的穩(wěn)定性是由于其具有更豐富的氧空位,提高了催化劑抗積炭性能。然后利用LaCoxNi1-xO_3作為前驅(qū)物,由于鈣鈦礦LaCoxNi1-xO_3中鈷離子和鎳離子還原性質(zhì)相近,能同時(shí)從鈣鈦礦結(jié)構(gòu)中還原成金屬,XRD、TPR和TEM等表征結(jié)果表明還原后形成了Ni-Co合金顆粒。由于大部分金屬離子都能形成鈣鈦礦結(jié)構(gòu),通過(guò)調(diào)控金屬離子還原可以制備其他多種負(fù)載型納米雙金屬或多金屬催化劑。與文獻(xiàn)中報(bào)道的催化劑性能相比較,La CoxNi1-xO_3用于乙醇水蒸氣重整反應(yīng)中表現(xiàn)出較好的活性和穩(wěn)定性。550°C反應(yīng)10h后催化劑表征結(jié)果顯示富Ni催化劑反應(yīng)后以纖維狀積碳為主,金屬顆粒位于纖維狀積碳末端,可以暴露出活性位,不會(huì)造成催化劑快速失活;而富Co催化劑反應(yīng)后主要生成無(wú)定型積碳,該種類型積碳會(huì)包裹住金屬顆粒,導(dǎo)致催化劑嚴(yán)重失活。在700°C反應(yīng)30h,所制得的催化劑都能表現(xiàn)出很好的穩(wěn)定性,且雙金屬催化劑的抗燒結(jié)性能優(yōu)于單金屬催化劑。最后以CuO/LaNiO_3和CuO/LaCoO_3為前驅(qū)物制備了負(fù)載型的Cu-Ni和Cu-Co催化劑。在前驅(qū)物中CuO能高分散在鈣鈦礦表面,且其在較低溫度下就能還原成金屬銅,鈣鈦礦結(jié)構(gòu)抑制了金屬離子的還原,鈣鈦礦中鎳離子或鈷離子需要在較高溫度下才能還原成金屬單質(zhì),生成的金屬Ni或Co聚集在優(yōu)先還原生成的金屬Cu表面,構(gòu)筑成類似核殼結(jié)構(gòu)的雙金屬顆粒。所制得的催化劑用于乙醇水蒸氣重整反應(yīng)能表現(xiàn)出較好的催化性能。
[Abstract]:The key technology of ethanol steam reforming to produce hydrogen is the research and development of catalyst. The catalyst reported in the literature has good activity and hydrogen selectivity. In recent years, the main research focus is on improving the stability of the catalyst. The carbon deposition after reaction at low temperature and the sintering of active components at high temperature are the main reasons leading to the deactivation of the catalyst. In this paper, two kinds of catalysts are proposed to improve the stability of the catalyst: one is to select oxide with oxygen vacancy as the catalyst carrier, the other is to prepare the supported bimetallic catalyst. The relationship between catalyst structure and performance was investigated. Firstly, Ni-La-Ce ternary oxide was prepared by citric acid complexation method and modified impregnation method respectively. The preparation method has great influence on the structure of the catalyst. In the steam reforming of ethanol, both of them showed good activity and hydrogen selectivity. The catalyst prepared by citric acid complexation method showed no deactivation after 8 h reaction under the conditions of reaction temperature of 650 擄C, ratio of water to alcohol of 3 and space velocity of 180000 ml gcat-1 h. The catalyst showed better stability because of its abundant oxygen vacancy. LaCoxNi1-xO_3 was used as precursor because the reduction properties of cobalt ion and nickel ion in perovskite LaCoxNi1-xO_3 were similar. The characterizations of XRDX TPR and TEM from perovskite structure show that Ni-Co alloy particles are formed after reduction. Because most metal ions can form perovskite structure, Various other supported nanometer bimetallic or polymetallic catalysts can be prepared by regulating metal ion reduction. Compared with the reported catalysts reported in the literature, La CoxNi1-xO_3 shows better activity in ethanol steam reforming reaction. The results of catalytic characterization of Ni rich catalyst after 10 h reaction showed that fibrous carbon deposition was dominant in Ni rich catalyst. Metal particles are located at the end of fibrous carbon deposition, which can expose the active sites and do not cause rapid deactivation of the catalyst. However, Co-rich catalysts mainly form amorphous carbon deposits, which cover the metal particles. The catalyst was deactivated seriously. At 700 擄C for 30 h, the prepared catalyst showed good stability. Finally, supported Cu-Ni and Cu-Co catalysts were prepared by using CuO/LaNiO_3 and CuO/LaCoO_3 as precursors. In the precursor, CuO can be highly dispersed on perovskite surface. The structure of perovskite inhibits the reduction of metal ions, and the nickel or cobalt ions in perovskite can be reduced to metal elements at a higher temperature. The metal Ni or Co was formed on the surface of Cu which was preferentially reduced to form bimetallic particles similar to the core-shell structure. The catalysts obtained showed good catalytic performance for the steam reforming of ethanol.
【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】：2015
【分類號(hào)】：O643.36;TQ116.2

【相似文獻(xiàn)】

相關(guān)期刊論文 前10條

1 劉少文,李永丹;甲烷重整制氫氣的研究進(jìn)展[J];武漢化工學(xué)院學(xué)報(bào);2005年01期

2 宋凌s，

本文編號(hào)：1690647