本文選題：生物油輕質(zhì)組分 + 水相重整�。� 參考：《浙江大學(xué)》2017年博士論文

【摘要】：對能源需求的快速增長與能源儲備的日益枯竭,導(dǎo)致全球面臨著嚴(yán)重的能源危機。生物油作為可再生液體燃料,用于替代化石燃料具有十分重要的意義。生物油是一種成分復(fù)雜的混合物,含有醇,酸,酮,醛,酚類衍生物和水等。由于其具有熱不穩(wěn)定性,腐蝕性,高粘度和低熱值,進一步的提質(zhì)對其利用是至關(guān)重要的。通過減壓蒸餾生物原油可獲得低沸點組分(LBF)。LBF的含水量可高達(dá)70-85wt.%,其中的有機物主要由低沸點的酸,醛和酯等組成。這些組分可與水形成沸點甚至低于水的共沸物,因而難以完全除去LBF中大量的水分。然而,直接丟棄不僅降低了生物質(zhì)的利用效率,還造成了環(huán)境污染。我們課題組前期的研究表明,以LBF為原料通過水相重整(APR)反應(yīng)制取氫氣,可使其得到最充分的利用。此外,還發(fā)現(xiàn)Pt/Al_2O_3為該體系中最優(yōu)單金屬催化劑,在催化活性和選擇性方面均顯示出了優(yōu)異的結(jié)果。本文針對生物油輕質(zhì)組分水相重整制氫反應(yīng),從以下幾個方面進行了探索性研究:1.論文研究了 Pt/Al_2O_3催化劑金屬顆粒大小對LBF的APR反應(yīng)催化性能的影響。成功制備了一系列具有不同Pt顆粒尺寸的Pt/Al_2O_3催化劑,發(fā)現(xiàn)隨著鉑金屬顆粒粒徑的增大,其活性和對氫氣的選擇性明顯降低,即該反應(yīng)是結(jié)構(gòu)敏感的。通過理論計算得到了不同尺寸的鉑顆粒的原子總數(shù),以及面上、頂點和邊上原子的數(shù)量。發(fā)現(xiàn)催化劑的活性與顆粒邊上鉑原子的數(shù)量有順變關(guān)系,其標(biāo)準(zhǔn)轉(zhuǎn)換頻率為一常數(shù),說明顆粒邊上配位不飽和的原子為該反應(yīng)的活性位點。原因為這些位點有利于形成相對穩(wěn)定的Pt-C吸附鍵,進而促進了 C-C鍵的斷裂,提高了活性和對氫氣的選擇性。2.實驗發(fā)現(xiàn),雖然Pt/Al_2O_3催化劑的APR活性和對氫氣的選擇性較高,但失活嚴(yán)重,在直接重復(fù)使用過程中,第二次反應(yīng)時催化劑的活性只有新鮮催化劑的40%,因此有必要研究Pt/Al_2O_3催化劑的失活機理。對反應(yīng)后的催化劑進行的XRD、TEM、SEM和TG等一系列表征結(jié)果表明,在反應(yīng)條件下,γ-Al_2O_3由于水解轉(zhuǎn)化為AlOOH(勃姆石),促進了積碳的形成,伴隨著比表面積的下降,以及由于積碳和勃姆石對活性位點的覆蓋等因素導(dǎo)致了Pt活性表面積的下降,造成了催化劑的失活。經(jīng)煅燒再生后,載體晶體結(jié)構(gòu)有所恢復(fù),大部分積碳得以消除,但仍有部分積碳堵塞載體的孔結(jié)構(gòu)且Pt顆粒有所長大。隨著循環(huán)反應(yīng)次數(shù)的增加,催化劑的催化活性和對氫氣的選擇性仍持續(xù)下降,可見在APR反應(yīng)體系中,Pt/Al_2O_3的可重復(fù)利用性能較差。3.為了探究適用于生物油輕質(zhì)組分水相重整體系的,具有優(yōu)異催化活性、選擇性和穩(wěn)定性的鉑基催化劑,制備了一系列不同組成的CeO_2-TiO_2,CeO_2-ZrO_2和TiO_2-ZrO_2載體樣品。通過BET和XRD表征,比較了其在反應(yīng)條件下的乙酸溶液中的水熱穩(wěn)定性。結(jié)果表明,CeO_2-TiO_2和CeO_2-ZrO_2混合氧化物,特別是C1Z1(CeO_2與ZrO_2摩爾比為1:1)和C1T1(CeO_2與TiO_2摩爾比為1:1),在乙酸溶液中連續(xù)處理16h后,沒有觀察到結(jié)構(gòu)和組成的改變,比表面積略有降低,表現(xiàn)出優(yōu)異的水熱穩(wěn)定性。4.將這些載體負(fù)載鉑后,考察了催化劑的還原特性和催化性能。實驗觀察到Pt/C1Z1和Pt/C1T1分別在相應(yīng)的三組Pt/CZ和Pt/CT催化劑中,具有最低的還原溫度和最佳的催化性能,其原因可能是在還原催化劑過程中,通過"氫溢出"使高度分散在載體表面的CeO_2部分被還原,產(chǎn)生了氧空位,促進了 LBF中極性含氧分子的吸附和轉(zhuǎn)化,進而提高了反應(yīng)物的轉(zhuǎn)化率。反應(yīng)后的Pt/C1Z1和Pt/C1T1催化劑經(jīng)在500℃空氣氛中煅燒再生后,用于重復(fù)利用性的研究,其催化活性和對氫氣的選擇性基本得以維持。在重復(fù)三次反應(yīng)后,催化劑的顆粒略微長大,且只形成了微量的積碳。因此,與Pt/Al_2O_3相比,Pt/C1Z1和Pt/C1T1催化劑的催化活性和對氫氣的選擇性相當(dāng),但具有更優(yōu)異的水熱穩(wěn)定性和可重復(fù)利用性。5.以生物油的主要組分:乙酸、乙酸甲酯、羥基丙酮、糠醛和鄰甲氧基苯酚為模型化合物,通過單獨的模型反應(yīng)產(chǎn)物結(jié)果,推測了可能的反應(yīng)機理。模型混合物和LBF復(fù)雜體系的液相產(chǎn)物中均只檢測到了未完全轉(zhuǎn)化的反應(yīng)物,氣相產(chǎn)物的結(jié)果與理論值之間也有所不同。本文的實驗結(jié)果表明,單獨的模型反應(yīng)與實際的LBF復(fù)雜體系的反應(yīng)之間有一定的差距。因此,直接以LBF復(fù)雜體系為反應(yīng)物的研究是非常有意義的。
[Abstract]:The rapid growth of energy demand and the increasing depletion of energy reserves have led to a serious energy crisis in the world. Bio oil, as a renewable liquid fuel, is of great significance in replacing fossil fuels. Bio oil is a complex mixture containing alcohols, acids, ketones, aldehydes, phenolic derivatives and water. Thermal instability, corrosiveness, high viscosity and low heat value, further upgrading is essential to its utilization. The water content of low boiling point component (LBF).LBF can be as high as 70-85wt.% by vacuum distillation. The organic compounds are mainly composed of low boiling acids, aldehydes and esters. These components can form boiling points or even lower than water. The azeotrope of water is difficult to completely remove a large amount of water in LBF. However, direct discarding not only reduces the utilization efficiency of biomass, but also causes environmental pollution. Our previous research group showed that LBF was used as the raw material to make hydrogen through the reaction of water phase reforming (APR), which can make it get the most full use. In addition, it also found Pt/Al_2O_ 3 for the best single metal catalyst in the system, excellent results have been shown in catalytic activity and selectivity. In this paper, an exploratory study was carried out on the reaction of hydrogen production by phase reforming of bio oil light mass group from the following aspects: 1. this paper studied the catalytic performance of the Pt/Al_2O_3 catalyst on the APR reaction of LBF. A series of Pt/Al_2O_3 catalysts with different Pt particle sizes were successfully prepared. It was found that with the increase of the particle size of the platinum metal particles, the activity and the selectivity to hydrogen were obviously reduced. That is, the reaction is structural sensitive. The total number of atoms of platinum particles of different sizes, as well as the surface, vertex and edge are obtained by theoretical calculation. It is found that the activity of the catalyst has a paramagnetic relationship with the number of platinum atoms on the edge of the particle, and the standard conversion frequency is a constant, indicating that the unsaturated atoms on the edge of the particle are the active sites of the reaction. The reason is that these sites are beneficial to the formation of a relatively stable Pt-C adsorption bond, and thus promote the fracture of the C-C bond and improve the activity. The selective.2. experiments on hydrogen and hydrogen have found that, although the APR activity of the Pt/Al_2O_3 catalyst and the selectivity to hydrogen are higher, the deactivation is serious. In the process of direct reuse, the activity of the catalyst is only 40% of the fresh catalyst during the second reaction. Therefore, it is necessary to study the deactivation mechanism of the Pt /Al_2O_3 catalyst. A series of characterization results, such as XRD, TEM, SEM and TG, showed that, under the reaction conditions, the conversion of gamma -Al_2O_3 to AlOOH (boehmite) promoted the formation of carbon accumulation, decreased the specific surface area, and the reduction of the active surface area of Pt due to the carbon deposition and the coverage of the boulite to the active site, resulting in the catalyst. After calcining, the crystal structure of the carrier was recovered and most of the carbon was eliminated, but some carbon deposited the pore structure of the carrier and Pt particles grew up. The catalytic activity of the catalyst and the selectivity for hydrogen continued to decline with the increase of the number of cyclic reactions. In the APR reaction system, Pt/Al_2O_3 could be seen. A series of platinum based catalysts with excellent catalytic activity, selectivity and stability were used to prepare a series of CeO_2-TiO_2, CeO_2-ZrO_2 and TiO_2-ZrO_2 carrier samples with excellent catalytic activity, selectivity and stability in order to explore the poor performance of.3., which was suitable for the biologic oil light mass fraction water phase reforming system. The reaction conditions were compared by BET and XRD. The hydrothermal stability in the acid solution shows that the mixed oxides of CeO_2-TiO_2 and CeO_2-ZrO_2, especially C1Z1 (CeO_2 and ZrO_2 molar ratio 1:1) and C1T1 (CeO_2 and TiO_2 mole ratio of 1:1), are not observed to change the structure and composition after continuous treatment in the acetic acid solution, and the surface product is slightly lower than the surface product, showing excellent hydrothermal stability. After loading platinum by sex.4., the reduction and catalytic properties of the catalyst were investigated. It was observed that Pt/C1Z1 and Pt/C1T1 had the lowest reduction temperature and the best catalytic performance in the corresponding three groups of Pt/CZ and Pt/CT catalysts, which may be caused by the "hydrogen overflow" in the process of reducing the catalyst. The CeO_2 part of the carrier surface is reduced and the oxygen vacancy is produced, which promotes the adsorption and transformation of polar oxygen molecules in LBF, and thus improves the conversion rate of the reactant. After the reaction, the Pt/C1Z1 and Pt/C1T1 catalysts are calcined in the air of 500 degrees centigrade and are used for reutilization, and their catalytic activity and selectivity to hydrogen are basic. It was maintained. After repeated three reactions, the particles of the catalyst grew slightly and only formed a small amount of carbon deposition. Therefore, compared with Pt/Al_2O_3, the catalytic activity of the Pt/C1Z1 and Pt/C1T1 catalysts was equal to the selectivity for hydrogen, but it had better hydrothermal stability and heavy compound.5. as the main component of the bio oil: acetic acid, B Acid methyl ester, hydroxy acetone, furfural and O methoxy phenol are model compounds. The possible reaction mechanism is speculated by the result of a single model reaction product. The reactant in the liquid product of the model mixture and the LBF complex system is only detected, and the results of the gas phase are also different from the theoretical values. The experimental results show that there is a gap between the single model reaction and the reaction of the actual LBF complex system. Therefore, it is very meaningful to study the reactant directly with the complex system of LBF.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：O643.36;TQ116.2

【參考文獻】

相關(guān)期刊論文 前1條

1 章曉彤;周國偉;白光偉;;氮鈰共摻雜介孔TiO_2的制備及在造紙廢水處理中的應(yīng)用[J];中國造紙;2010年02期

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本文編號：2094150