發(fā)布時間：2018-04-02 21:31

  本文選題：生物柴油　切入點：酯交換　出處：《吉林大學(xué)》2011年博士論文

【摘要】：近些年來,隨著能源危機的日益加劇以及環(huán)境問題的日益嚴重,迫使人們?nèi)ふ乙恍┛稍偕⑶鍧崱h(huán)境友好的能源。生物柴油作為一種可再生的能源,不僅有著與礦物柴油相似的燃燒與動力性能,而且還具有對環(huán)境友好的特性,因此正逐漸吸引著越來越多的能源工作者及環(huán)境工作者的注意。合成生物柴油主要有四種方法,即直接混合法、微乳化法、高溫裂解法和酯交換反應(yīng)法。其中前兩者屬于物理方法,后兩者屬于化學(xué)方法。使用物理方法雖然能降低油脂的粘度,但燃燒中產(chǎn)生的積炭及潤滑油污染等問題仍然難以解決,而高溫裂解法會產(chǎn)生大量小分子化合物,主要產(chǎn)物是生物汽油而非生物柴油。相比之下,采用動植物油和甲醇為原料、經(jīng)酯交換反應(yīng)制取生物柴油的方法是一條簡單有效、可操作性強的工藝路線。 該反應(yīng)可用酸或堿作為催化劑,其中常用的均相酸、堿催化劑包括硫酸、鹽酸、磷酸、氫氧化鈉、氫氧化鉀以及鈉和鉀的醇鹽。使用均相酸、堿催化劑不僅會對儀器設(shè)備造成腐蝕,反應(yīng)后催化劑無法回收還會產(chǎn)生一定量的中和廢棄物,導(dǎo)致生產(chǎn)成本增加的同時還易造成環(huán)境污染。用多相催化劑代替均相催化劑就可以解決上述問題。目前已報道的多相酸性催化劑有固體超強酸、雜多酸、離子交換樹脂等：堿性催化劑有：分子篩、負載型堿金屬及堿土金屬催化劑,負載型有機堿、復(fù)合金屬氧化物以及水滑石等。但上述催化劑大多存在活性較低或是活性組分易流失等問題,因此制備一種高效、穩(wěn)定的催化劑是十分有意義的。 基于上述情況,本論文主要開展了固體酸、堿催化材料的制備及表征工作,并嘗試將這些材料作為多相催化劑用于合成生物柴油的酯交換反應(yīng)中。同時結(jié)合各種表征手段,研究了各種酸、堿材料的結(jié)構(gòu)及表面性質(zhì),著重探討了載體表面性質(zhì)對負載的活性中心(物種)的結(jié)構(gòu)、酸堿性質(zhì)的影響,并與催化劑的反應(yīng)性能進行了關(guān)聯(lián)。此外,還針對性能優(yōu)異的多相催化劑體系進行了催化反應(yīng)動力學(xué)方面的研究,確定了反應(yīng)動力學(xué)的主要參數(shù)(包括反應(yīng)速率常數(shù)、表觀活化能以及指前因子等)。論文主要研究內(nèi)容和結(jié)果如下： 一.介孔鈦硅復(fù)合材料在三乙酸甘油酯與甲醇的酯交換反應(yīng)中的應(yīng)用 采用檸檬酸路線制備了具有高鈦含量的鈦硅復(fù)合材料,通過制備生物柴油的模型反應(yīng)一三乙酸甘油酯與甲醇的酯交換反應(yīng)評價了其催化性能,并與采用傳統(tǒng)的溶膠-凝膠法制備的鈦硅材料進行了對比分析。發(fā)現(xiàn)采用檸檬酸路線制備的鈦硅復(fù)合材料在相同的反應(yīng)條件下對該反應(yīng)具有較好的催化活性及穩(wěn)定性,循環(huán)使用三次后反應(yīng)活性基本保持不變。 通過X射線衍射、紫外、程序升溫脫附以及吡啶吸附紅外光譜等表征手段證明了鈦硅復(fù)合材料中的鈦物種不是以Ti02晶相或孤立的鈦物種形態(tài)存在的,而主要是以低聚的TiO、形態(tài)存在且高分散在二氧化硅表面上的。為了弄清鈦物種的存在狀態(tài)對材料的催化性能的影響,分別采用硫酸以及硫酸銨對鈦硅復(fù)合材料進行處理,使材料表面的Ti02物種發(fā)生聚集形成大的顆粒(晶體)。催化反應(yīng)評價結(jié)果表明處理后的催化劑反應(yīng)活性明顯降低。綜合各種因素,可以認為在二氧化硅表面存在的高分散的鈦物種應(yīng)該是酯交換反應(yīng)中的主要活性中心。 二.多孔炭負載CaO催化劑的制備、表征及在三乙酸甘油酯與甲醇的酯交換反應(yīng)中的應(yīng)用 采用浸漬法分別以四種炭材料(介孔炭NC-2、活性炭AC、碳分子篩CMS以及介孔炭CMK-3)為載體制備了負載型CaO催化劑,考察了它們在三乙酸甘油酯與甲醇的酯交換反應(yīng)中的催化活性。結(jié)果表明：以表面含氧基團相對較少的碳分子篩(CMS)和介孔炭(CMK-3)為載體制備的負載型CaO催化劑雖然初始活性較高,但穩(wěn)定性很差；而以表面含氧基團較豐富的介孔炭(NC-2)和活性炭(AC)為載體制備的負載型CaO催化劑則對該反應(yīng)表現(xiàn)出非常高的反應(yīng)活性和穩(wěn)定性,且催化劑可多次循環(huán)使用。 針對CaO/NC-2體系,系統(tǒng)考察了CaO的負載量、催化劑的用量、催化劑的焙燒溫度以及反應(yīng)溫度等參數(shù)對催化反應(yīng)性能的影響。優(yōu)化了反應(yīng)工藝條件,同時確定了一些反應(yīng)動力學(xué)參數(shù)。實驗結(jié)果表明,在通常的反應(yīng)條件下,反應(yīng)速率常數(shù)不受傳質(zhì)過程的影響,反應(yīng)遵循一級動力學(xué)模式,催化反應(yīng)的表觀活化能為44.9 kJ/mol。 結(jié)合各種表征結(jié)果,我們認為炭負載氧化鈣催化劑具有相對較高的催化活性應(yīng)主要歸結(jié)于大量的具有強堿中心性質(zhì)的CaO物種的存在；載體表面的性質(zhì),特別是含氧基團的存在則對CaO物種的分散形態(tài)及結(jié)構(gòu)穩(wěn)定性起到了關(guān)鍵作用,是催化劑具有高穩(wěn)定性的主要原因。由此我們推測,在具有高活性、高穩(wěn)定性的炭負載氧化鈣催化劑上至少存在兩種形式的CaO物種。第一種形式的CaO是不完全堆積的,它與炭載體表面的含氧基團通過強相互作用鍵合(會導(dǎo)致其堿性變?nèi)?,從而使氧化鈣粒子與載體之間能夠形成有效的鏈接。第二種形式的CaO是高度堆積的,存在于第一種CaO物種之上,與炭載體之間的相互作用較弱,但具有較強的堿性和較高的催化活性。這兩種形式的CaO可以看作一個整體(例如一個小的CaO簇或粒子)高分散在炭載體的表面。 三.氧化石墨負載CaO催化劑的制備及在大豆油與甲醇酯交換制備生物柴油反應(yīng)中的應(yīng)用 分別以氧化石墨(GO)以及熱處理后的氧化石墨(GO-T)為載體制備了負載型CaO催化劑,并通過大豆油與甲醇的酯交換反應(yīng)評價了其催化性能。結(jié)果表明：CaO/GO催化劑對該反應(yīng)表現(xiàn)出較好的催化活性以及穩(wěn)定性,而CaO/GO-T催化劑雖然也具有較高的初始活性,但穩(wěn)定性相對較差,在循環(huán)反應(yīng)中,催化劑的活性明顯下降。 催化反應(yīng)以及表征結(jié)果進一步證實了我們之前的推測：即炭載體表面的含氧基團對活性物種(CaO)起到錨定的作用,從而使高分散在炭載體表面的CaO粒子與載體之間形成一個穩(wěn)定的連接,最終形成了具有高活性和高穩(wěn)定性的負載型CaO催化劑。 此外,通過對比研究發(fā)現(xiàn)CaO/GO催化劑的酯交換反應(yīng)活性與CaO/NC-2催化劑的活性基本相當(dāng)。二者的主要差別在于CaO/GO催化劑的初始活化溫度或再生處理所需的溫度均明顯低于CaO/NC-2催化劑。初步表征結(jié)果證明,載體GO與NC-2相比,在相同條件下,其表面的含氧基團更易與活性物種發(fā)生相互作用,形成最終的負載型CaO催化劑。 綜上所述,本論文主要針對制備生物柴油的酯交換反應(yīng)開展了幾種固體酸、堿催化劑即鈦硅復(fù)合氧化物、多孔炭負載CaO催化劑以及氧化石墨負載CaO催化劑的制備、表征及催化性能研究工作。得到了幾種性能優(yōu)異的固體催化劑,對催化劑的活性中心性質(zhì)、反應(yīng)機理和催化反應(yīng)動力學(xué)等方面有了較為深刻的認識,希望能為今后生物柴油的制備研制出新型高效的固體酸、堿催化劑提供參考依據(jù)。
[Abstract]:In recent years , with the increasing of the energy crisis and the growing environmental problems , it has forced people to look for some renewable , clean and environmentally friendly energy sources .


The reaction can be used as catalyst , wherein the common homogeneous acid and alkali catalyst include sulfuric acid , hydrochloric acid , phosphoric acid , sodium hydroxide , potassium hydroxide and alcohol salt of sodium and potassium .


Based on the above situation , the preparation and characterization of solid acid and alkali catalytic materials are mainly carried out . The structure and surface properties of various acid and alkali materials are studied . The structure and surface properties of various acid and alkali materials are studied . The main research contents and results are as follows :


Application of mesoporous titanium silicon composite material in ester exchange reaction between triacetin and methanol


A titanium - silicon composite with high titanium content was prepared by citric acid route . The catalytic performance was evaluated by transesterification of glycerol triacetin with methanol . It was found that the titanium - silicon composite prepared by citric acid route had better catalytic activity and stability under the same reaction conditions .


In order to understand the influence of the presence of titanium species on the catalytic properties of Ti - Si composites , titanium - silicon composites were treated with sulfuric acid and ammonium sulfate to form large particles ( crystals ) .


Preparation , Characterization and Application of Porous Carbon Supported CaO Catalyst in Ester Exchange Reaction of Triacetate and Methanol


Supported CaO catalysts were prepared by impregnation method with four carbon materials ( mesoporous carbon NC - 2 , activated carbon AC , carbon molecular sieve CMS and mesoporous carbon CMK - 3 ) as carriers . The catalytic activity of them in transesterification of triacetin and methanol was investigated .
and the supported CaO catalyst prepared by using mesoporous carbon ( NC - 2 ) and activated carbon ( AC ) rich in surface oxygen - containing group as a carrier shows very high reaction activity and stability to the reaction , and the catalyst can be recycled for many times .


According to the CaO / NC - 2 system , the influence of the loading amount of CaO , the amount of catalyst , the calcination temperature of the catalyst and the reaction temperature on the catalytic reaction performance were investigated . The reaction conditions were optimized , and some reaction kinetic parameters were determined . The experimental results show that the reaction rate constant is not affected by the mass transfer process under the general reaction conditions . The reaction follows the first order kinetic model , and the apparent activation energy of the catalytic reaction is 44.9 kJ / mol .


In combination with various characterization results , we believe that the carbon - supported calcium oxide catalyst has relatively high catalytic activity and is mainly attributed to the existence of a large amount of CaO species with strong alkali center properties ;
In the first form , CaO is highly accumulated , which is weakly interacting with the oxygen - containing group on the surface of the carbon carrier by strong interaction ( which causes its basicity to become weak ) , but has stronger basicity and higher catalytic activity .


Preparation of CaO catalyst loaded with graphite oxide and its application in preparing biodiesel by transesterification of soybean oil and methanol


The supported CaO catalyst was prepared by oxidation of graphite ( GO ) and oxidized graphite ( GO - T ) after heat treatment . The catalytic performance was evaluated by transesterification of soybean oil and methanol . The results show that the CaO / GO catalyst exhibits better catalytic activity and stability , while the CaO / GO - T catalyst has high initial activity , but the stability is relatively poor . In the recycle reaction , the activity of the catalyst is obviously decreased .


The catalytic reaction and the characterization results further confirm our previous assumption that the oxygen - containing group on the surface of the carbon support acts as an anchor to the active species ( CaO ) , thereby forming a stable connection between the CaO particles dispersed on the surface of the carbon carrier and the carrier , and finally forming a supported CaO catalyst having high activity and high stability .


The results show that the oxygen - containing groups on the surface of CaO / GO catalysts are more likely to interact with the active species under the same conditions to form the final supported CaO catalyst .


In conclusion , the preparation , characterization and catalytic performance of several solid acids , alkali catalysts , Ti - Si composite oxides , porous carbon supported CaO catalysts and oxidized graphite supported CaO catalysts were studied in this paper . Several excellent solid catalysts were obtained . The results showed that the catalysts could be used to prepare new high - efficient solid acids and alkali catalysts for the preparation of biodiesel .

【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2011
【分類號】：TE667

【引證文獻】

相關(guān)碩士學(xué)位論文 前1條

1 張婷;固體堿催化地溝油制備生物柴油的研究[D];陜西師范大學(xué);2012年

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本文編號：1702186