本文選題：核殼結(jié)構(gòu) + 分子篩膜�。� 參考：《浙江大學(xué)》2017年碩士論文

【摘要】：低碳烴是現(xiàn)代化學(xué)工業(yè)中最重要的基礎(chǔ)原料之一,工業(yè)上主要通過(guò)石腦油蒸汽裂解過(guò)程獲得。但隨著石油短缺問(wèn)題日益嚴(yán)重,開(kāi)發(fā)以煤、天然氣及生物質(zhì)為原料的非石油生產(chǎn)低碳烴工藝路線已經(jīng)迫在眉睫。而以煤、天然氣及生物質(zhì)為原料,經(jīng)合成氣通過(guò)費(fèi)-托合成反應(yīng)直接生產(chǎn)低碳烴是目前最具應(yīng)用前景的工藝路線之一。但受費(fèi)-托合成產(chǎn)物分布規(guī)律限制,工業(yè)上費(fèi)-托合成流程主要生產(chǎn)汽油、柴油、潤(rùn)滑油等產(chǎn)品。為了解決費(fèi)-托合成反應(yīng)對(duì)低碳烴選擇性低的問(wèn)題,研究者分別從工藝流程及催化劑角度出發(fā),提出了反應(yīng)段-裂解段串聯(lián)方法、費(fèi)-托合成催化劑與分子篩物理混裝方法及將費(fèi)-托合成活性組分浸漬到分子篩制成雙功能催化劑等方法。但上述方法存在以下問(wèn)題:一、流程長(zhǎng)、投資成本高;二、費(fèi)-托合成產(chǎn)物并不是完全進(jìn)入分子篩進(jìn)行裂解;三、費(fèi)-托合成活性組分與分子篩酸性位強(qiáng)結(jié)合,導(dǎo)致催化劑活性較低。而如果在費(fèi)-托合成催化劑(核)外包覆一層分子篩膜(殼),形成核殼結(jié)構(gòu)型催化劑。那么可以利用殼層分子篩(如SAPO-34)上的質(zhì)子酸,將重質(zhì)烴進(jìn)一步裂解為低碳烴,從而達(dá)到提高合成氣直接轉(zhuǎn)化對(duì)低碳烴的產(chǎn)物選擇性。為了實(shí)現(xiàn)上述要求的催化劑,本文提出構(gòu)建一種新型的核殼型催化劑。首先采用共沉淀-焙燒-浸漬-焙燒法制備傳統(tǒng)的FeMnK催化劑,然后采用噴涂法在其表面涂覆混有SAPO-34分子篩粉末的硅溶膠,經(jīng)干燥焙燒后制成FeMnK@SAPO-34核殼催化劑。對(duì)所制備催化劑,采用表面積-孔隙度測(cè)試、X射線粉末衍射測(cè)試、掃描電子顯微鏡、H_2-TPR等表征方法進(jìn)行分析,并在高壓微型固定床反應(yīng)器中經(jīng)還原后進(jìn)行費(fèi)托合成反應(yīng)考評(píng)。結(jié)果表明,制備得到的核殼型催化劑的比表面積及孔容有明顯上升,核心FeMnK催化劑的活性不受外層分子篩的影響;新型FeMnK@SAPO-34核殼催化劑實(shí)現(xiàn)了費(fèi)-托合成反應(yīng)與烴類分子篩裂解的反應(yīng)耦合,明顯改善了合成氣制備低碳烴的產(chǎn)物選擇性。其中二次涂覆核殼催化劑在氫碳比為3.5、反應(yīng)壓力為1.0 MPa、反應(yīng)溫度為325 ℃和反應(yīng)空速為1500h-1的較優(yōu)條件下,其催化的CO轉(zhuǎn)化率為74.8%,全產(chǎn)物組成中低碳烯烴選擇性為42.4%,低碳烴(C_2~=～C_4~=和C_2～C_4)總選擇性為51.5%(若不計(jì)CO_2,僅碳?xì)浠衔镏械吞枷N選擇性則達(dá)到57.0%,低碳烴選擇性達(dá)到69.2%)。
[Abstract]:Low carbon hydrocarbon is one of the most important basic raw materials in modern chemical industry. But with the problem of oil shortage becoming more and more serious, it is urgent to develop non-oil production process of low carbon hydrocarbon using coal, natural gas and biomass as raw materials. Using coal, natural gas and biomass as raw materials, the direct production of low carbon hydrocarbons through the synthesis reaction of syngas is one of the most promising technological routes. However, limited by the distribution law of Fischer-Tort synthetic products, the industrial Fischer-Tort synthesis process mainly produces gasoline, diesel oil, lubricating oil and other products. In order to solve the problem of low selectivity for low carbon hydrocarbons in Fischer-Tropsch synthesis reaction, the researchers put forward a series method from the point of view of process flow and catalyst, respectively. The physical mixing method of Fischer-Tort synthesis catalyst and molecular sieve and dipping the active component of Fischer-Tropsch synthesis into molecular sieve to make bifunctional catalyst. However, the above methods have the following problems: first, the process is long and the investment cost is high; second, the products of Fischer-Tort synthesis are not completely entered into the molecular sieve for pyrolysis; third, the active components of the Fischer-Tropsch synthesis are strongly bound to the acidic sites of the molecular sieve. As a result, the activity of the catalyst is low. If a layer of molecular sieve membrane (shell) is coated on the surface of Fischer-Tropsch synthesis catalyst (nucleus), a core-shell structure catalyst is formed. The proton acid on the shell molecular sieve (such as SAPO-34) can be used to further decompose the heavy hydrocarbon into low carbon hydrocarbon so as to improve the product selectivity of direct conversion of syngas to low carbon hydrocarbon. In order to achieve the above requirements, a new type of core-shell catalyst is proposed in this paper. The traditional FeMnK catalyst was prepared by coprecipitation calcination impregnation roasting method. Then the FeMnK@SAPO-34 core-shell catalyst was prepared by spraying the silica sol mixed with SAPO-34 molecular sieve powder. The catalysts were characterized by surface area and porosity measurements by X-ray powder diffraction, scanning electron microscopy (SEM) and H _ (2-TPR), respectively. Fischer synthesis reaction was evaluated after reduction in a high-pressure micro-fixed-bed reactor. The results showed that the specific surface area and pore volume of the core-shell catalyst increased obviously, and the activity of the core FeMnK catalyst was not affected by the outer molecular sieve. The new FeMnK@SAPO-34 core-shell catalyst has realized the coupling of Fischer-Tropsch synthesis reaction with the cracking of hydrocarbon molecular sieve, which has improved the selectivity of synthesis gas for the preparation of low carbon hydrocarbons. When the ratio of hydrogen to carbon is 3.5, the reaction pressure is 1.0 MPA, the reaction temperature is 325 鈩，

本文編號(hào)：1814661