本文選題：費-托合成 + 介孔泡沫硅��； 參考：《蘇州大學(xué)》2016年博士論文

【摘要】：能源短缺和環(huán)境污染日益成為當(dāng)今世界各國關(guān)注的焦點。在我國,石油資源相對短缺,近年來石油需求量也急劇增長,日益突出的石油供需矛盾制約了我國經(jīng)濟和社會的發(fā)展。利用費-托合成技術(shù)把煤、天然氣和生物質(zhì)轉(zhuǎn)化為清潔液體燃料和高附加值化學(xué)品是緩解我國石油供需緊張局勢和高效利用煤、天然氣和生物質(zhì)的有效途徑之一。催化劑是費-托合成技術(shù)的核心,對于負載型的費-托合成催化劑,載體是制備催化劑的重要組成部分。有序介孔材料具有比表面積大、孔道結(jié)構(gòu)規(guī)整、孔徑大小可調(diào)等特點,成為常用的費-托合成催化劑載體。介孔泡沫硅(MCF,Mesostructured cellular silica foams)材料除了具有以上特征外,還具有大的孔徑和三維互通的孔道結(jié)構(gòu),有利于物質(zhì)在孔道中的傳輸和擴散。因此,本文以MCF為載體,并對其進行改性,系統(tǒng)研究了MCF及改性MCF負載的鈷催化劑的費-托合成反應(yīng)催化性能,該研究為開發(fā)反應(yīng)活性高、選擇性和穩(wěn)定性好的費-托合成催化劑提供了理論參考。本論文主要研究內(nèi)容如下:(1)以P123為模板劑,苯為微乳劑,正硅酸四乙酯為硅源合成了具有泡沫狀孔結(jié)構(gòu)的MCF材料,同時制備了孔徑相同但孔道結(jié)構(gòu)不同的SBA-16、KIT-6和SBA-15分子篩,并分別負載了15 wt.%的鈷基催化劑,即Co/MCF,Co/SBA-16,Co/KIT-6和Co/SBA-15。結(jié)果表明,四種催化劑表現(xiàn)出不同的還原度(39.1%-63.7%)和鈷的分散度(9.6%-11.1%),載體的孔結(jié)構(gòu)顯著影響鈷催化劑的分散度和還原度。具有三維(3D)孔結(jié)構(gòu)的Co/MCF、Co/SBA-16和Co/KIT-6的CO轉(zhuǎn)化率(46.0%-49.4%)明顯比二維(2D)孔結(jié)構(gòu)的Co/SBA-15(22.3%)高。同樣具有3D孔道結(jié)構(gòu)。催化劑Co/MCF比Co/SBA-16和Co/KIT-6活性高。由于MCF具有3D開放的孔道和大的孔徑,有利于合成氣和產(chǎn)物在孔道中的擴散,因此催化劑Co/MCF表現(xiàn)出較低的甲烷選擇性和高的C5+選擇性,其中C20+選擇性高達31.5%,明顯高于其它催化劑(14.7%-15.8%)。(2)以mcf為載體,檸檬酸為絡(luò)合劑,通過改變檸檬酸的用量獲得了具有不同粒徑大小的鈷催化劑。結(jié)果表明,隨著檸檬酸用量的增加,鈷的粒徑從9.4nm減小到3.9nm,還原度從63.5%降低到49.6%,分散度從10.2%增加到24.6%。當(dāng)鈷粒徑為6.9nm時,mcf負載的鈷催化劑具有較高的分散度(14.0%)和適當(dāng)?shù)倪�原度(54.2%),此時催化劑的co轉(zhuǎn)化率最高(62.7%)。當(dāng)鈷粒徑為3.9nm-8.0nm時,反應(yīng)的tof和鈷粒徑之間存在線性關(guān)系,鈷粒徑越大,tof值越大,當(dāng)鈷粒徑大于8.0nm時,tof保持不變。(3)采用ph值調(diào)節(jié)法成功制備了鋁硅比從0.05到0.3的al-mcf(amcf)載體。結(jié)果表明,al以計量比進入到mcf骨架中,而且仍然保持泡沫狀介孔結(jié)構(gòu)。負載鈷之后,隨著鋁含量的增加,鈷催化劑的分散度從7.5%增加到12.0%。費-托合成反應(yīng)測試表明:當(dāng)反應(yīng)溫度為220°c時,含鋁催化劑(co/amcfs)的co轉(zhuǎn)化率(31.6%-37.1%)明顯高于純硅mcf負載的鈷催化劑(19.5%)。當(dāng)反應(yīng)溫度為250°c時,co轉(zhuǎn)化率隨著鋁含量的增加從53.4%增加到57.6%。催化劑co/mcf由于失活較快,導(dǎo)致催化劑具有低的co轉(zhuǎn)化率(30.9%)、高的甲烷選擇性(24.3%)和低的c5+選擇性(58.4%),這是由于鈷的燒結(jié)形成難還原的鈷硅物種導(dǎo)致了催化劑的失活。催化劑co/mcf-3的液態(tài)產(chǎn)物(60.8%)和異構(gòu)烴選擇性(17.4%)最高,這是因為co/amcf-3具有最多的四配位骨架鋁和最強的酸性。(4)采用zsm-5晶種組裝合成了具有大比表面積,較大雙孔孔徑的三維泡沫狀介孔復(fù)合材料z-mcfs,并與相同條件下合成的純硅mcf進行對比。結(jié)果表明,催化劑co/z-mcfs的費-托合成反應(yīng)活性(76.5%-79.0%)明顯高于純硅mcf負載的催化劑co/mcf(68.1%)。隨著zsm-5晶種含量的增加,催化劑co/z-mcfs的活性逐漸增加,c5+選擇性降低。當(dāng)zsm-5晶種含量最高時,催化劑co/z-mcf-3具有最低的失活率,穩(wěn)定性最好,這歸因于催化劑中鈷和載體之間的強相互作用。降低反應(yīng)空速(8nl·h-1·g-1至4nl·h-1·g-1),產(chǎn)物中異構(gòu)烷烴的比例增加,烯烴減小,烴類產(chǎn)物主要集中在中間餾分(c5-c20),其值為64.2%。(5)以p123為模板劑,環(huán)己烷為微乳劑,正硅酸四乙酯為硅源合成了mcf,考察了環(huán)己烷的用量、老化溫度、鋁摻雜對mcf結(jié)構(gòu)和水熱穩(wěn)定性的影響。結(jié)果表明,隨著環(huán)己烷用量的增加,mcf的孔徑和孔容增大,比表面積都大于570m2·g-1。當(dāng)環(huán)己烷的用量為12.0g時,樣品mcf-2的比表面最大,約為800.7m2·g-1。MCF的孔徑和孔容隨著老化溫度的增加而增大。當(dāng)老化溫度為130°C時,MCF的比表面大于1000 m2·g-1,泡沫狀結(jié)構(gòu)最規(guī)整。經(jīng)水熱處理12 h后,純硅MCF的比表面積下降了73.5%,鋁摻雜的樣品Al-MCF的比表面積僅下降38.7%,表明摻雜鋁提高了MCF的水熱穩(wěn)定性。
[Abstract]:Energy shortage and environmental pollution have become the focus of attention of all countries in the world. In China, the shortage of oil resources and the rapid growth of oil demand in recent years, the increasingly prominent contradiction of oil supply and demand has restricted the development of our country's economy and society. The conversion of coal, natural gas and biomass into clean liquid by the use of Fisher technology. Materials and high added value chemicals are one of the effective ways to alleviate the tense situation of petroleum supply and demand and the efficient use of coal, natural gas and biomass. The catalyst is the core of the Fischer Tropsch synthesis technology. For the supported Fischer Tropsch synthesis catalyst, the carrier is an important part of the preparation of the catalyst. The ordered mesoporous material has a large specific surface area and a hole. The channel structure is regular, the size of the aperture is adjustable and so on. It has become a common carrier for the Fischer Tropsch synthesis catalyst. In addition to the above features, MCF, Mesostructured cellular silica foams has a large pore size and a three-dimensional interworking channel structure, which is beneficial to the transport and diffusion of the material in the pass. Therefore, this paper is based on MCF The carrier was modified and the catalytic performance of MCF and modified MCF supported cobalt catalyst was systematically studied. This study provides a theoretical reference for the development of FTIR synthesis catalyst with high reactive activity, selectivity and stability. The main contents of this paper are as follows: (1) P123 as a template, benzene as microemulsion, positive silicon Acid four ethyl ester was used as a silicon source to synthesize a MCF material with a foamy pore structure. At the same time, SBA-16, KIT-6 and SBA-15 molecular sieves with the same pore size but different pore structure were prepared, and 15 wt.% cobalt based catalysts, namely Co/MCF, Co/SBA-16, Co/KIT-6 and Co/SBA-15., showed that four kinds of catalysts showed different reducibility (39.1%-63.). 7%) and the dispersion of cobalt (9.6%-11.1%), the pore structure of the carrier significantly affects the dispersion and reducibility of the cobalt catalyst. The CO conversion rate (46.0%-49.4%) with a three-dimensional (3D) pore structure of Co/MCF, Co/SBA-16 and Co/KIT-6 (46.0%-49.4%) is obviously higher than the Co/SBA-15 (22.3%) of the two-dimensional (2D) pore structure. The same has a 3D pass structure. The activity is high. Because MCF has the open channel and large pore size of 3D, it is beneficial to the diffusion of synthetic gas and products in the channel. Therefore, the catalyst Co/MCF shows low methane selectivity and high C5+ selectivity. The selectivity of C20+ is 31.5%, obviously higher than that of other catalysts (14.7%-15.8%). (2) MCF is the carrier and citric acid is the complexing agent. The cobalt catalyst with different sizes was obtained by changing the dosage of citric acid. The results showed that with the increase of citric acid, the particle size of cobalt decreased from 9.4nm to 3.9nm, the reduction degree decreased from 63.5% to 49.6%, and the dispersion degree increased from 10.2% to 24.6%. when the cobalt particle diameter was 6.9nm, and the cobalt catalyst supported by MCF had a higher dispersion (14%). With the proper degree of reduction (54.2%), the CO conversion rate of the catalyst is the highest (62.7%). When the cobalt particle diameter is 3.9nm-8.0nm, there is a linear relationship between the reaction TOF and the cobalt particle diameter, the greater the cobalt particle diameter, the greater the TOF value, and the TOF remain unchanged when the cobalt particle size is greater than 8.0nm. (3) the al-mcf (AMCF) from 0.05 to 0.3 of aluminum and silicon ratio has been successfully prepared by using the pH value adjustment method. The carrier. The results show that Al is in the MCF framework and still maintains the foamy mesoporous structure. After loading cobalt, with the increase of aluminum content, the dispersion of cobalt catalyst increases from 7.5% to 12.0%. Fischer Tropsch synthesis reaction test shows that when the reaction temperature is 220 C, the CO conversion rate (31.6%-37.1%) of aluminum containing catalyst (co/amcfs) is clear. The cobalt catalyst (19.5%) was significantly higher than the pure silicon MCF load. When the reaction temperature was 250 C, the CO conversion increased from 53.4% to the 57.6%. catalyst co/mcf due to the faster deactivation, resulting in a low CO conversion (30.9%), a high methane selectivity (24.3%) and a low c5+ selectivity (58.4%), which was due to the sintering of cobalt. The cobalt silicon species, which is difficult to reduce, leads to the deactivation of the catalyst. The liquid product (60.8%) of the catalyst co/mcf-3 and the selectivity of isomeric hydrocarbons (17.4%) are the highest, which is because co/amcf-3 has the most four coordination skeleton aluminum and the strongest acidity. (4) the three dimensional foam with a large specific surface area and a large double pore aperture is synthesized by the ZSM-5 crystal assembly. The pore composite material z-mcfs was compared with the pure silicon MCF synthesized under the same conditions. The results showed that the catalyst co/z-mcfs's Fischer Tropsch synthesis reaction activity (76.5%-79.0%) was significantly higher than that of the pure silicon MCF supported catalyst co/mcf (68.1%). With the increase of the ZSM-5 crystal content, the activity of the catalyst co/z-mcfs increased gradually and the c5+ selectivity decreased. When ZSM-5, the selectivity of the catalyst decreased. At the highest grain content, the catalyst co/z-mcf-3 has the lowest inactivation rate and the best stability, which is attributed to the strong interaction between the cobalt and the carrier in the catalyst. The reaction space velocity (8nl. H-1. G-1 to 4nl. H-1. G-1) is reduced, the proportion of ISO paraffin in the product is increased, the alkene is reduced, and the hydrocarbon products are mainly concentrated in the middle fraction (C5-C20). 64.2%. (5) with P123 as a template, cyclohexane as microemulsion and four ethyl orthosilicate as the silicon source, MCF was synthesized. The effect of cyclohexane dosage, aging temperature and aluminum doping on the structure and hydrothermal stability of MCF was investigated. The results showed that the pore diameter and pore volume of MCF increased with the increase of cyclohexane, and the specific surface area was larger than 570m2 g-1. as ring self. When the amount of alkane is 12.0g, the specific surface of the sample mcf-2 is the largest. The pore size of 800.7m2. G-1.MCF and Kong Rong increase with the increase of aging temperature. When the aging temperature is 130 C, the specific surface of MCF is larger than 1000 m2. G-1, and the foam structure is the most regular. After 12 h, the specific surface area of pure silicon MCF decreases by 73.5% and the aluminum doped sample A The specific surface area of l-MCF only decreased by 38.7%, indicating that the doped aluminum increased the hydrothermal stability of MCF.

【學(xué)位授予單位】：蘇州大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：O643.36;TQ529.2
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本文編號：1810990