【摘要】：乙烯是石油化工產(chǎn)品的基礎(chǔ)原料和合成藥物的前驅(qū)體,在全球工業(yè)快速發(fā)展的同時,對乙烯的消耗與日俱增。目前,乙烯的主要來源是石油裂解,但隨著石油資源的日益枯竭和價格的不斷攀升,以石油為原料的乙烯工業(yè)受到了巨大沖擊。乙醇脫水制取乙烯工藝能夠緩解乙烯生產(chǎn)的壓力,其工藝流程簡單、能耗低、環(huán)境友好等優(yōu)勢,被認為是最具有應(yīng)用前景的路線。因此,如何更有效的將低濃度乙醇在較低溫度下高效地用于乙烯生產(chǎn),已經(jīng)成為研究者關(guān)注的熱點。本文利用硫酸、聚合羥基鋁、雜多酸對蒙脫土進行多種方法的復(fù)合改性,修飾結(jié)構(gòu),優(yōu)化性能;研究改性蒙脫土在低溫下對低濃度乙醇脫水制乙烯反應(yīng)的催化性能,通過XRD、BET、FT-IR、TG-DTA、NH_3-TPD等技術(shù)對改性蒙脫土的結(jié)構(gòu)進行了表征,進一步優(yōu)化催化劑的合理構(gòu)筑,主要研究內(nèi)容及結(jié)論如下:以硫酸作為處理劑,對蒙脫土進行改性,在酸化溫度80℃,酸化時間7 h,硫酸濃度Φ=25%的條件下對蒙脫土進行酸化處理。研究表明酸化過程中,蒙脫土層間和孔道的雜質(zhì)溶出,層狀結(jié)構(gòu)呈剝離狀態(tài),狹縫孔轉(zhuǎn)變?yōu)槎逊e孔,比表面積從21 m2/g增大到357 m2/g,孔容從0.0436 cm3/g增加至0.561 cm3/g。將不同量的磷鉬酸和磷鎢酸負載到酸改性的蒙脫土上,不僅克服了雜多酸活性組分易流失、分布不均勻等缺點,而且獲得了高的乙烯選擇性和乙醇轉(zhuǎn)化率。當負載10%磷鎢酸時,在反應(yīng)溫度300℃、原料濃度ΦEthanol=30%、質(zhì)量空速0.65h-1的條件下,反應(yīng)進行12 h后,乙烯選擇性依舊保持在93%左右,乙醇轉(zhuǎn)化率為89%。以硫酸改性的蒙脫土作為基體,通過離子交換引入不同量的聚合羥基鋁,可以恢復(fù)蒙脫土的層狀結(jié)構(gòu),將其焙燒后,可轉(zhuǎn)變?yōu)榛钚灾行木鶆虻胤植荚诳椎乐?將其應(yīng)用于催化反應(yīng)時,表現(xiàn)出優(yōu)異的催化性能。研究結(jié)果表明:聚合物的交換量影響催化劑的穩(wěn)定性和耐受性;當引入聚合物的量為CEC的70%時,催化劑的活性較高。當反應(yīng)溫度300℃、原料濃度ΦEthanol=30%、質(zhì)量空速0.65h-1時,乙醇轉(zhuǎn)化率在97%左右,乙烯的選擇性接近100%。鑒于生物發(fā)酵乙醇濃度較低,需進一步降低原料濃度。以硫酸-聚合物復(fù)合改性后的蒙脫土作為載體,通過浸漬法負載不同種類、不同量的雜多酸,研究其在ΦEthanol=20%中的催化性能。研究結(jié)果表明:當負載磷鎢酸量為15%時,由于表面磷鎢酸的覆蓋,強弱酸含量和分布得到優(yōu)化,充分利用了載體的外表面,每個PW雜多酸分子能與更多的表面OH基團相作用,使得PW與載體之間的相互作用增強,耐水性提升,活性組分不易流失,因此降低反應(yīng)物濃度時,依然具有較好的催化活性。當反應(yīng)溫度300℃、原料濃度ΦEthanol=20%時,乙醇的轉(zhuǎn)化率為98%,乙烯選擇性接近100%;反應(yīng)12h,乙醇轉(zhuǎn)化率仍可保持在95.7%左右。
[Abstract]:Ethylene is the basic raw material of petrochemical products and precursor of synthetic drugs. With the rapid development of global industry, the consumption of ethylene is increasing day by day. At present, the main source of ethylene is oil cracking, but with the increasing depletion of petroleum resources and rising prices, the ethylene industry with petroleum as raw material has been greatly impacted. The process of producing ethylene by dehydration of ethanol can relieve the pressure of ethylene production. It has the advantages of simple process, low energy consumption and friendly environment. It is considered to be the most promising route for application. Therefore, how to use low-concentration ethanol more effectively in ethylene production at lower temperature has become the focus of researchers' attention. In this paper, sulfuric acid, poly (hydroxyaluminum) and heteropolyacid were used to modify montmorillonite, modify the structure and optimize the properties of montmorillonite. The catalytic properties of modified montmorillonite for dehydration of low concentration ethanol to ethylene at low temperature were studied. The structure of modified montmorillonite was characterized by XRD,BET,FT-IR,TG-DTA,NH_3-TPD and other techniques. The main research contents and conclusions are as follows: using sulfuric acid as the treatment agent, the montmorillonite was modified at 80 鈩，

本文編號：2438682