前驅(qū)體對完全液相法Cu-Zn-Al催化劑結(jié)構(gòu)及其催化合成氣制乙醇性能的影響
發(fā)布時間：2018-09-18 16:13
【摘要】：乙醇作為世界公認的綠色環(huán)保優(yōu)質(zhì)替代性液體燃料和汽油添加劑,相比其它燃料具有辛烷值高、毒性低、硫分灰分低、CO_2排量小的優(yōu)良特性,應(yīng)用廣泛。傳統(tǒng)的乙醇制備方法——糧食發(fā)酵法和乙烯水合法具有原料緊缺、能耗大等突出問題,根據(jù)我國煤炭相對豐富的現(xiàn)狀,煤基合成氣制乙醇是一條前景廣闊、研究價值高的合成途徑。本課題組針對漿態(tài)床反應(yīng)器特點,自主研發(fā)了漿態(tài)床催化劑完全液相制備工藝,并在前期研究中發(fā)現(xiàn):采用完全液相法制備的Cu-Zn-Al催化劑在催化合成氣制甲醇過程中高選擇性地生成了乙醇,但是由于高選擇性乙醇催化劑對前驅(qū)體結(jié)構(gòu)敏感,故重現(xiàn)性和穩(wěn)定性較差。在后期研究中發(fā)現(xiàn),溶膠制備方法、老化方式以及膠凝劑的種類對催化劑前驅(qū)體影響較大,且Al OOH對CO的解離和C鏈增長有積極作用。針對以上內(nèi)容,本文采用完全液相法制備催化劑,通過改變制備方法(醇解法、水解法)、Al OOH溶膠的加入量、老化方式(混合老化、分開老化)以及膠凝劑的種類,探索催化劑前軀體結(jié)構(gòu)的優(yōu)化,以期提高催化劑的穩(wěn)定性和重現(xiàn)性,并結(jié)合XRD、N_2吸脫附、H_2-TPR、NH_3-TPD-MS、FT-IR、TG-DTG、27Al-MAS-NMR、XPS、TEM多種測試手段對催化劑的結(jié)構(gòu)進行了表征分析,獲得以下主要結(jié)論:(1)一種催化劑制備的新思路:在不添加任何助劑的條件下,分開制備Cu-Zn-Al溶膠(第一鋁源)和Al OOH溶膠(第二鋁源)得到溶膠前驅(qū)體,進而老化、熱處理制得催化劑。此法制備的催化劑穩(wěn)定性高,120 h內(nèi)未出現(xiàn)失活現(xiàn)象,CO轉(zhuǎn)化率最高可達60%。(2)選用結(jié)論1的方法,改變AlOOH溶膠的加入量,當催化劑中n(Cu:Zn:Al:Al OOH)=2:1:0.8:0.6時,催化劑的初始乙醇(Et OH)/總醇(ROH)選擇性達最大。此比例下,醇解法比水解法的初始乙醇/總醇選擇性大,混合老化比分開老化的初始乙醇/總醇選擇性大。醇解法混合老化催化劑的初始Et OH/ROH選擇性可達70.3%;醇解法分開老化催化劑的初始Et OH/ROH選擇性可達35.4%;水解法混合老化催化劑的初始Et OH/ROH選擇性可達27.1%,水解法分開老化催化劑的初始Et OH/ROH選擇性可達15.8%。(3)選用結(jié)論1的方法,反應(yīng)前催化劑中鋁物種為無定型Al OOH,有五配位鋁和六配位鋁。反應(yīng)后催化劑中的鋁物種為Al2O3,存在四配位鋁和六配位鋁,五配位鋁消失。結(jié)合實驗結(jié)果推測,當催化劑中六配位鋁與五配位鋁的量達到合適比例,且五配位鋁的量和占比較高時有利于乙醇的生成。當六配位鋁的量和占比遠大于五配位鋁的,且存在四配位鋁時有利于DME的生成。(4)選用檸檬酸溶液做膠凝劑的催化劑,初始Et OH/ROH選擇性由第一天的29.6%以上升趨勢在第四天達42.6%,CO轉(zhuǎn)化率第二天可達37.7%,之后逐漸下降�？傊�,分開制備Cu-Zn-Al溶膠(第一鋁源)和Al OOH溶膠(第二鋁源)的催化劑制備方法,使得催化劑的穩(wěn)定性和重現(xiàn)性顯著提高。
[Abstract]:Ethanol is recognized as an environmental friendly and high quality alternative liquid fuel and gasoline additive. Compared with other fuels, ethanol has the advantages of high octane number, low toxicity, low sulfur content and low CO _ 2 emission, so it is widely used. The traditional methods of ethanol preparation, such as grain fermentation and ethylene-water, have outstanding problems such as shortage of raw materials and high energy consumption. According to the relative abundance of coal in our country, coal-based syngas is a promising way to produce ethanol. To study the high value synthetic pathway. According to the characteristics of slurry bed reactor, our team has developed a complete liquid phase preparation process for slurry bed catalyst. In previous studies, it was found that the Cu-Zn-Al catalyst prepared by the complete liquid phase method was highly selective to produce ethanol in the process of synthesis gas to methanol, but the highly selective ethanol catalyst was sensitive to the precursor structure. Therefore, the reproducibility and stability are poor. In the later study, it was found that the preparation method of sol, aging method and the type of gelling agent had great influence on the catalyst precursor, and Al OOH had a positive effect on the dissociation of CO and the growth of C chain. In view of the above, the catalyst was prepared by the complete liquid phase method. The amount of Al OOH sol, the aging mode (mixed aging, separating aging) and the type of gelling agent were changed by changing the preparation method (alcoholysis, hydrolysis method). In order to improve the stability and reproducibility of the catalyst, the structure of the catalyst was characterized and analyzed with XRD,N_2 desorption and desorption H2-TPRN NH3-TPD-MSFT-IRT-TG-DTG 27Al-MAS-NMR-27Al-MAS-NMR-XPSTEM. The main conclusions are as follows: (1) A new way of preparing catalyst: Cu-Zn-Al sol (first aluminum source) and Al OOH sol (second aluminum source) were prepared separately without adding any additives, and then aged. The catalyst was prepared by heat treatment. The catalyst prepared by this method has high stability and no deactivation within 120 hours. (2) the method of conclusion 1 is chosen to change the amount of AlOOH sol. When n (Cu:Zn:Al:Al OOH) is 2: 1: 0.8: 0.6 in the catalyst, The initial ethanol (Et OH) / total alcohol (ROH) selectivity of the catalyst was the highest. In this ratio, the selectivity of the initial ethanol / total alcohol was higher than that of the hydrolysis method, and the selectivity of the mixed aging was higher than that of the separated aging method. The initial Et OH/ROH selectivity of the mixed aging catalyst for alcoholysis can reach 70.3, the initial Et OH/ROH selectivity of the catalyst separated by alcoholysis can reach 35.4and the initial Et OH/ROH selectivity of the mixed aging catalyst by hydrolysis method can reach 27.1%, and the initial Et OH/ROH selectivity by hydrolysis method can be as high as 27.1g. The initial Et OH/ROH selectivity of the catalyst can reach 15.8%. (3) the method of conclusion 1 is selected. The aluminum species in the catalyst before the reaction are amorphous Al OOH, with five coordinated aluminum and six coordinated aluminum. After the reaction, the species of aluminum in the catalyst were Al2O3, with four coordinated aluminum and six coordinated aluminum, and the five coordinated aluminum disappeared. Combined with the experimental results, it was inferred that the amount of six-coordinated aluminum and five-coordinated aluminum in the catalyst reached an appropriate proportion, and the amount and proportion of five-coordinated aluminum were higher in favor of ethanol production. When the amount and proportion of hexa-coordinated aluminum is much larger than that of five-coordinated aluminum, and the existence of four-coordinated aluminum is favorable to the formation of DME. (4) citric acid solution is used as the catalyst for gelling agent. The initial Et OH/ROH selectivity increased from 29.6% on the first day to 42.6% on the fourth day, and the conversion rate of CO reached 37.7% on the second day, and then decreased gradually. In a word, the stability and reproducibility of Cu-Zn-Al sol (first aluminum source) and Al OOH sol (second aluminum source) were improved significantly.
【學位授予單位】：太原理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：O643.36;TQ223.122
[Abstract]:Ethanol is recognized as an environmental friendly and high quality alternative liquid fuel and gasoline additive. Compared with other fuels, ethanol has the advantages of high octane number, low toxicity, low sulfur content and low CO _ 2 emission, so it is widely used. The traditional methods of ethanol preparation, such as grain fermentation and ethylene-water, have outstanding problems such as shortage of raw materials and high energy consumption. According to the relative abundance of coal in our country, coal-based syngas is a promising way to produce ethanol. To study the high value synthetic pathway. According to the characteristics of slurry bed reactor, our team has developed a complete liquid phase preparation process for slurry bed catalyst. In previous studies, it was found that the Cu-Zn-Al catalyst prepared by the complete liquid phase method was highly selective to produce ethanol in the process of synthesis gas to methanol, but the highly selective ethanol catalyst was sensitive to the precursor structure. Therefore, the reproducibility and stability are poor. In the later study, it was found that the preparation method of sol, aging method and the type of gelling agent had great influence on the catalyst precursor, and Al OOH had a positive effect on the dissociation of CO and the growth of C chain. In view of the above, the catalyst was prepared by the complete liquid phase method. The amount of Al OOH sol, the aging mode (mixed aging, separating aging) and the type of gelling agent were changed by changing the preparation method (alcoholysis, hydrolysis method). In order to improve the stability and reproducibility of the catalyst, the structure of the catalyst was characterized and analyzed with XRD,N_2 desorption and desorption H2-TPRN NH3-TPD-MSFT-IRT-TG-DTG 27Al-MAS-NMR-27Al-MAS-NMR-XPSTEM. The main conclusions are as follows: (1) A new way of preparing catalyst: Cu-Zn-Al sol (first aluminum source) and Al OOH sol (second aluminum source) were prepared separately without adding any additives, and then aged. The catalyst was prepared by heat treatment. The catalyst prepared by this method has high stability and no deactivation within 120 hours. (2) the method of conclusion 1 is chosen to change the amount of AlOOH sol. When n (Cu:Zn:Al:Al OOH) is 2: 1: 0.8: 0.6 in the catalyst, The initial ethanol (Et OH) / total alcohol (ROH) selectivity of the catalyst was the highest. In this ratio, the selectivity of the initial ethanol / total alcohol was higher than that of the hydrolysis method, and the selectivity of the mixed aging was higher than that of the separated aging method. The initial Et OH/ROH selectivity of the mixed aging catalyst for alcoholysis can reach 70.3, the initial Et OH/ROH selectivity of the catalyst separated by alcoholysis can reach 35.4and the initial Et OH/ROH selectivity of the mixed aging catalyst by hydrolysis method can reach 27.1%, and the initial Et OH/ROH selectivity by hydrolysis method can be as high as 27.1g. The initial Et OH/ROH selectivity of the catalyst can reach 15.8%. (3) the method of conclusion 1 is selected. The aluminum species in the catalyst before the reaction are amorphous Al OOH, with five coordinated aluminum and six coordinated aluminum. After the reaction, the species of aluminum in the catalyst were Al2O3, with four coordinated aluminum and six coordinated aluminum, and the five coordinated aluminum disappeared. Combined with the experimental results, it was inferred that the amount of six-coordinated aluminum and five-coordinated aluminum in the catalyst reached an appropriate proportion, and the amount and proportion of five-coordinated aluminum were higher in favor of ethanol production. When the amount and proportion of hexa-coordinated aluminum is much larger than that of five-coordinated aluminum, and the existence of four-coordinated aluminum is favorable to the formation of DME. (4) citric acid solution is used as the catalyst for gelling agent. The initial Et OH/ROH selectivity increased from 29.6% on the first day to 42.6% on the fourth day, and the conversion rate of CO reached 37.7% on the second day, and then decreased gradually. In a word, the stability and reproducibility of Cu-Zn-Al sol (first aluminum source) and Al OOH sol (second aluminum source) were improved significantly.
【學位授予單位】：太原理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：O643.36;TQ223.122
【參考文獻】
相關(guān)期刊論文 前10條
1 張小雨;黃偉;高志華;張琳;時培祥;邊仲凱;;完全液相法中Cu源對Cu-Zn-Al催化劑結(jié)構(gòu)及性能的影響[J];燃料化學學報;2016年10期
2 游向軒;樊金串;黃偉;周由之;魏s，
本文編號：2248435
本文鏈接：http://sikaile.net/kejilunwen/huaxue/2248435.html
最近更新
教材專著
