本文選題：硅酸鋰 + 二氧化碳��； 參考：《中國(guó)礦業(yè)大學(xué)》2017年碩士論文

【摘要】：燃煤電站是CO_2的主要排放源,捕集和回收燃煤煙氣中的CO_2是緩解CO_2排放危機(jī)最直接有效的手段。硅酸鋰作為一種高溫CO_2吸附劑,具有吸附容量大、循環(huán)性能穩(wěn)定以及成本合理等優(yōu)點(diǎn),被認(rèn)為是目前能夠高溫脫除燃煤煙氣CO_2的有潛力捕集材料。本文主要針對(duì)常規(guī)固態(tài)制備方法合成的硅酸鋰吸附劑捕獲CO_2活性較弱、反應(yīng)速率較慢,難以達(dá)到實(shí)際應(yīng)用需求的缺點(diǎn),開展優(yōu)良吸附劑的制備研究,并使用X-射線粉末衍射儀(XRD)、掃描電子顯微鏡(SEM)、N2吸附儀和熱重分析儀(TG)等手段對(duì)合成樣品的物相組成、結(jié)構(gòu)特征及吸附性能進(jìn)行表征,系統(tǒng)研究吸附劑的高溫CO_2吸附性能。研究的主要內(nèi)容如下:(1)利用碳包裹的原理,在溶膠-凝膠法的基礎(chǔ)上合成得到一種高效的高溫CO_2吸附劑(CSG-Li_4Si O_4)。檸檬酸在整個(gè)合成過(guò)程中既作為螯合劑使硅與鋰的前驅(qū)體得到充分的混合,也作為碳包裹中的碳源,可以有效的抑制硅酸鋰晶體結(jié)構(gòu)的增大。分別與固固反應(yīng)和溶膠-凝膠法合成的硅酸鋰進(jìn)行對(duì)比,發(fā)現(xiàn)利用碳包裹法能夠合成純度高、晶粒尺寸小、比表面積較大的硅酸鋰吸附劑,其擁有更高的吸附量,更快的吸附速率和更好的吸附穩(wěn)定性,其最大吸附量可以達(dá)到34.2wt.%。(2)采用溶膠-凝膠法制備分別摻雜有K、Mg、Cr和Ce金屬元素的Li_4Si O_4吸附劑。結(jié)果表明,所有摻雜金屬元素(K、Mg、Cr、Ce)都能夠融入硅酸鋰的晶格中,但對(duì)Ce而言,其摻雜難度更大。Ce的摻雜能夠有效抑制晶體團(tuán)聚,同時(shí)摻雜后形成的Ce O_2能夠有效改善硅酸鋰吸附劑顆粒形貌,提高吸附劑吸附性能。Ce2-Li_4Si O_4在純CO_2、690℃條件下,10min內(nèi)最大吸附量可達(dá)34.57wt.%,對(duì)其進(jìn)行循環(huán)吸附性能測(cè)試,在10次吸附/解吸循環(huán)后,其吸附容量并未出現(xiàn)明顯衰減,樣品具有良好的可再生能力。(3)采用一種“簡(jiǎn)單”的水合-摻雜NaCl方法制備硅酸鋰吸附劑,以提高其在低濃度CO_2下的吸附性能。Li_4Si O_4材料的水合產(chǎn)物主要是Li OH和Li2Si O3,水合后再生得到的HC樣品顆粒粒徑有所減小,這將有助于CO_2的吸附,其對(duì)應(yīng)的CO_2吸附量為13.7wt.%,是SS樣品的兩倍多。摻雜Na Cl后,一方面,有利于制備得到小粒徑和大比表面積的硅酸鋰顆粒,顯著地促進(jìn)了化學(xué)吸附過(guò)程。另一方面,在吸收CO_2過(guò)程中,共摻雜的Na Cl誘導(dǎo)形成熔融相,能夠顯著降低CO_2擴(kuò)散阻力。水合和Na Cl摻雜均能有效提高吸附劑性能。通過(guò)對(duì)水合Na Cl摻雜量的研究發(fā)現(xiàn),摻雜量越大,吸附劑的吸收速率越快,但過(guò)量的Na Cl(5wt.%)會(huì)導(dǎo)致雜質(zhì)的形成,從而降低吸附容量。綜合判斷最佳添加劑比例為3wt.%,HC-3Na最大吸附量高達(dá)34.2wt.%。對(duì)HC-3Na進(jìn)行循環(huán)吸附性能測(cè)試,在10次吸附/解吸循環(huán)后,其吸附容量并未出現(xiàn)衰減,維持著32wt.%左右,樣品具有良好的可再生能力。
[Abstract]:Coal-fired power station is the main emission source of CO_2. Collecting and recovering CO_2 from coal-fired flue gas is the most direct and effective means to alleviate the CO_2 emission crisis.As a high temperature CO_2 adsorbent, lithium silicate has the advantages of large adsorption capacity, stable cycling performance and reasonable cost. It is considered to be a potential trapping material for removing CO_2 from coal-fired flue gas at high temperature.In this paper, the preparation of lithium silicate adsorbent, which was synthesized by conventional solid-state preparation method, was mainly aimed at the disadvantages of weak CO_2 activity and slow reaction rate, which was difficult to meet the practical application requirements, so the research on the preparation of excellent adsorbent was carried out.The phase composition, structure and adsorption properties of the synthesized samples were characterized by means of X-ray powder diffractometer (XRD), scanning electron microscope (SEM) and thermogravimetric analyzer (TG). The adsorption properties of the adsorbent at high temperature were studied systematically.The main contents of this study are as follows: (1) based on the sol-gel method, a high temperature CO_2 adsorbent, CSG-Li _ 4Si _ 2O _ 4, has been synthesized by using the principle of carbon encapsulation.Citric acid can be used as a chelating agent to make the precursor of silicon and lithium fully mixed and as a carbon source in carbon encapsulation, which can effectively inhibit the increase of crystal structure of lithium silicate.Compared with solid reaction and sol-gel method, lithium silicate adsorbents with high purity, small grain size and large specific surface area can be synthesized by carbon encapsulation method.With faster adsorption rate and better adsorption stability, the maximum adsorption capacity can reach 34.2wt.0.The Li_4Si O _ 4 adsorbent doped with K _ (mg) Cr and ce metal elements was prepared by sol-gel method.The results show that all the doped metal elements (K _ 2O _ 3) can be incorporated into the lattice of lithium silicate, but for ce, the doping of 路ce can effectively restrain the crystal agglomeration.At the same time, ce _ O _ 2 formed by doping can effectively improve the morphology of lithium silicate adsorbent particles and improve the adsorbability of the adsorbent. Ce2-Li4SiO _ 4 can reach the maximum adsorption capacity of 34.57 wt.In 10 minutes at pure CO_2690 鈩，

本文編號(hào)：1759737