本文選題：鎳催化劑 + 碳化硅�。� 參考：《太原理工大學(xué)》2017年碩士論文

【摘要】：能源與環(huán)境是人類社會(huì)可持續(xù)發(fā)展所面臨的兩大挑戰(zhàn),長(zhǎng)期以煤為主的能源消費(fèi)結(jié)構(gòu)導(dǎo)致我國(guó)的環(huán)境問(wèn)題日益突出。發(fā)展煤制天然氣可以實(shí)現(xiàn)煤炭的清潔高效利用,緩解國(guó)內(nèi)市場(chǎng)天然氣供需矛盾。煤制天然氣的核心是甲烷化反應(yīng)器的設(shè)計(jì)及高效催化劑的研發(fā)。CO加氫甲烷化反應(yīng)屬于強(qiáng)放熱過(guò)程,會(huì)導(dǎo)致催化劑的活性組份燒結(jié)和產(chǎn)生積碳,嚴(yán)重影響工業(yè)裝置的安全穩(wěn)定運(yùn)行。SiC具有良好的熱穩(wěn)定性和化學(xué)惰性,而且導(dǎo)熱性能很強(qiáng),有助于反應(yīng)放熱的及時(shí)傳導(dǎo),抑制催化劑床層“熱點(diǎn)”的形成。本論文采用微波輔助碳熱還原法制備SiC載體,負(fù)載金屬鎳后用于CO甲烷化反應(yīng),與γ-Al_2O_3載體進(jìn)行了比較研究;此外,考察了添加Ce助劑對(duì)于改善Ni/SiC催化劑的抗積碳和抗燒結(jié)性能影響,主要研究結(jié)果總結(jié)如下:(1)采用納米二氧化硅和石墨作為原料,通過(guò)微波輔助碳熱還原法制備碳化硅粉體,優(yōu)化的制備條件為:Si/C原子比1:1.2,微波輸出功率2.5 kW,加熱溫度為1100~1400°C,恒溫時(shí)間30 min;制得的碳化硅粉體的晶相為3C-SiC,比表面積為8.8 m~2g~(-1);(2)采用SiC和γ-Al_2O_3負(fù)載金屬鎳后進(jìn)行CO甲烷化反應(yīng)性能評(píng)價(jià),結(jié)果顯示,10Ni/Al_2O_3的低溫反應(yīng)活性較高,CO轉(zhuǎn)化率在320°C時(shí)達(dá)到95.6%,到400°C時(shí)與10Ni/Si C接近;10Ni/SiC在500~600°C高溫段表現(xiàn)出明顯優(yōu)勢(shì),CO轉(zhuǎn)化率和CH_4選擇性分別為94.9%和82.3%,而10Ni/Al_2O_3上的CO轉(zhuǎn)化率和CH_4選擇性為91.9%和80.2%;(3)在10Ni/Si C中添加7 wt.%的CeO_2助劑催化性能達(dá)到最佳。選取10Ni/Al_2O_3、10Ni/SiC和7Ce-10Ni/SiC在600°C進(jìn)行CO甲烷化反應(yīng)活性評(píng)價(jià),當(dāng)空速由15 000 mL g-1 h-1增加至60 000 mL g-1 h-1,10Ni/Al_2O_3在前20 h活性保持不變,隨后CO轉(zhuǎn)化率和CH_4選擇性逐漸降低,反應(yīng)進(jìn)行至62 h時(shí)由于嚴(yán)重積碳導(dǎo)致反應(yīng)器堵塞被迫終止;當(dāng)10Ni/SiC反應(yīng)進(jìn)行到100h后,反應(yīng)器前壓略微升高,達(dá)到1.2 MPa,反應(yīng)活性及選擇性略微下降;7Ce-10Ni/SiC在100 h的反應(yīng)過(guò)程中表現(xiàn)出極高的穩(wěn)定性,CO轉(zhuǎn)化率和CH_4選擇性均保持同一水平;(4)對(duì)10Ni/SiC和10Ni/Al_2O_3的表征結(jié)果顯示,10Ni/SiC上Ni的晶粒尺寸更小、分散度更高,因此可以提供更多的反應(yīng)活性位點(diǎn);對(duì)反應(yīng)后催化劑的表征結(jié)果顯示,10Ni/Al_2O_3、10Ni/SiC和7Ce-10Ni/SiC上Ni晶粒出現(xiàn)了不同的增長(zhǎng),積碳速率分別為0.01935 g/h、0.00528 g/h、0.00465 g/h,10Ni/Al_2O_3上的積碳量最大,積碳以石墨碳或類石墨化碳居多,并且形成較多碳纖維,從而導(dǎo)致Ni被剝離的現(xiàn)象;分析認(rèn)為,SiC的表面惰性和良好的導(dǎo)熱性能可以將反應(yīng)放熱及時(shí)移出,因而表現(xiàn)出良好的抗燒結(jié)和抗積碳性能;(5)對(duì)7Ce-10Ni/SiC的表征結(jié)果顯示,CeO_2均勻分散在Ni顆粒周圍,有效阻止了Ni晶粒的團(tuán)聚,增加了Ni分散度,而且增強(qiáng)了金屬與載體之間的作用力;此外,Ce3+/Ce4+氧化還原電子對(duì)增加了Ni的電子云密度,促進(jìn)了CO的解離,因此加快了甲烷化反應(yīng)速率。
[Abstract]:Energy and environment are two major challenges faced by the sustainable development of human society. The energy consumption structure, which is dominated by coal for a long time, has caused the environmental problems of our country to become increasingly prominent. The clean and efficient utilization of coal can be realized by developing coal-made natural gas, and the contradiction between supply and demand of natural gas in domestic market can be alleviated. The core of coal to produce natural gas is the design of methanation reactor and the development of high efficient catalyst. The methanation of CO hydrogenation is a strong exothermic process, which will lead to the sintering of the active component of the catalyst and the formation of carbon. Sic has good thermal stability and chemical inertia, and has strong thermal conductivity, which is helpful to the timely conduction of reaction exothermic and restrain the formation of "hot spot" in catalyst bed. In this thesis, SiC carrier was prepared by microwave-assisted carbothermal reduction method, and then loaded with nickel metal for CO methanation reaction. The results were compared with 緯 -Al _ 2O _ 3 carrier. The effect of ce additive on carbon deposition and sintering resistance of Ni/SiC catalyst was investigated. The main results were summarized as follows: (1) Silicon carbide powder was prepared by microwave-assisted carbothermal reduction using nano-silica and graphite as raw materials. The optimized preparation conditions are as follows: 1: 1.2, microwave output power 2.5 kW, heating temperature 1100,1400 擄C, constant temperature time 30 min, the crystalline phase of the prepared silicon carbide powder is 3C-SiC, the specific surface area is 8.8 m ~ (2) g / C ~ (-1), the methanation reaction performance is evaluated by SiC and 緯 -Al _ 2O _ 3 loaded nickel metal. The results showed that 10Ni / Al _ 2O _ 3 had higher activity at low temperature and CO conversion reached 95.6C at 320 擄C, and close to 10Ni- / sic at 400 擄C showed obvious superior CO conversion and CH_4 selectivity of 94.9% and 82.3% for 10Ni/Al_2O_3 at 500-600 擄C, respectively, while the CO conversion on 10Ni/Al_2O_3 and CH_4 were 82.3%. The selectivity is 91.9% and 80.2% respectively. The best catalytic performance is achieved by adding 7wt.% CeO_2 promoter to 10Ni/Si C. 10Ni- / Al2O3Ni- / sic and 7Ce-10Ni/SiC were selected to evaluate the methanation activity of CO at 600 擄C. The activity of CO methanation was increased from 15 000 mL g -1 h-1 to 60 000 mL g-1 h-110Ni- Al2O3 at 600 擄C. the activity of CO conversion and CH_4 selectivity decreased gradually in the first 20 h. The reactor blockage was forced to terminate at 62 h due to serious carbon deposition, and the pre-reactor pressure increased slightly after the 10Ni/SiC reaction reached 100h. Up to 1.2 MPa, the activity and selectivity of 7Ce-10Ni- / sic decreased slightly during the 100h reaction. During the 100h reaction, the CO conversion and CH_4 selectivity remained at the same level. The characterization of 10Ni/SiC and 10Ni/Al_2O_3 showed that the grain size of Ni on 10Ni / sic was smaller. The results of the characterization of the catalyst after the reaction show that the 10Ni- / Al2O3Ni- / sic and the Ni grains on 7Ce-10Ni/SiC have different growth, and the carbon deposition rate is 0.00528g / h 0.00465g / h 0.00465g / h 0.00465g / h 0.00465g / h ~ 0.00465g / h ~ 0.00465g / h ~ 0.00465g / h ~ 0.00465g / h ~ 0.00465g / h ~ 0.00465g / h ~ 0.00465g / h ~ 0.00465g / h ~ 0.00465g / h ~ 0.00465g The carbon deposition is mainly graphite carbon or graphitized carbon, and more carbon fibers are formed, which results in the exfoliation of Ni. It is considered that the surface inertia and good thermal conductivity of sic can remove the reaction exothermic heat in time. The results of 7Ce-10Ni/SiC characterization show that CeO-2 is uniformly dispersed around Ni particles, which effectively prevents the agglomeration of Ni grains, increases the dispersion of Ni, and enhances the interaction force between metal and support. In addition, ce _ 3 / ce _ 4 redox electron pair increased the electron cloud density of Ni, promoted the dissociation of CO, and accelerated the rate of methanation reaction.
【學(xué)位授予單位】：太原理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：O643.36

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