陽衛(wèi)軍++秦明高++劉世明??
摘 要:以從鹽湖鹵水中提取的RbCl為原料,利用原位法和浸漬法制備了含銣的固體超強堿Rb2O/γ-Al2O3.以蔗糖為模板劑,以Rb2CO3及Al(NO3)3為反應物,原位法制備了Rb2O/γ-Al2O3.同時以蔗糖為模板劑,先分別以Al(NO3)3和異丙醇鋁(Al[ CH(CH3)2]3)為鋁源制備了介孔γ-Al2O3,再通過浸漬RbNO3溶液,制備了一系列的負載型Rb2O/γ-Al2O3.通過優(yōu)化制備條件,兩種方法制備的Rb2O/γ-Al2O3的堿強度均可達26.5以上,即為超強堿.把制備的超強堿Rb2O/γ-Al2O3用于三醋酸甘油酯和甲醇為模型反應物模擬生物柴油制備過程中的催化酯交換反應.得到了最佳的催化反應條件:原料醇酯比8∶1,反應溫度338 K,反應時間4 h,催化劑用量w三醋酸甘油酯=6.0%,在此工藝條件下乙酸甲酯產(chǎn)率達98%以上.
關(guān)鍵詞:銣;γ-Al2O3;固體超強堿;酯交換反應;三醋酸甘油酯
中圖分類號:O643.36 文獻標識碼:A
Preparation of Rubidium Solid Superbases and Its Catalytic
Application in Interesterification
YANG Wei-jun,QIN Ming-gao ,LIU Shi-ming
(College of Chemistry and Chemical Engineering ,Hunan Univ ,Changsha ,Hunan 410082,China)
Abstract:Solid superbases Rb2O/γ-Al2O3were prepared from rubidium salts separated from salt brine. Sucrose was used as the template, Rb2CO3 (prepared from RbCl) and Al(NO3)3 as the raw materials, we prepared Rb2O/γ-Al2O3 successfully by using in-situ method. In impregnation method, we first used sucrose as the template, Al (NO3)3 and Al[CH(CH3)2]3 as aluminum sources, respectively to prepare γ-Al2O3,and then a series of Rb2O/γ-Al2O3 with different rubidium contents through the impregnation of RbNO3 (prepared from RbCl). The base strength of Rb2O/γ-Al2O3 both can reach 26.5 or more, belonging to superbase prepared through the two methods by controlling the conditions. The prepared Rb2O/γ-Al2O3 solid superbases were used to simulate interesterification in the process of producing biodiesel by catalyzing triglycerides acetate and methanol. The optimum reaction conditions were as follows: the ratio of alcohol to ester was 8∶1, the reaction temperature was 338 K, the reaction time was 4 h, and the amount of catalyst is 6.0% of the weight of ester. Under those conditions, the productivity of methyl acetate was up to 98%.
Key words: rubidium;γ-Al2O3;solid superbase;transesterification
固體超強堿是指堿強度指數(shù)H-大于26.5的固體堿性物質(zhì)[ 1].固體超強堿在烯烴異構(gòu)化、酯交換、Michael加成、醇脫氫與縮合等反應中均表現(xiàn)出很高的催化活性.作為非均相催化劑,具有與產(chǎn)物容易分離,后處理簡單,可回收重復利用,對設(shè)備腐蝕小,產(chǎn)生的廢液少等優(yōu)勢[ 2-5],因而具有廣闊的應用前景.然而,固體超強堿的常見修飾組分為堿金屬鈉、鉀及其化合物或堿土金屬化合物[ 6-8],以銣化合物修飾的固體超強堿很少被研究.
我國鹽湖鹵水中的銣儲量很大,但是由于鹵水中銣元素的濃度非常低,其它共生離子種類多、濃度高,從鹽湖鹵水中提取微量的銣存在很大的困難.我們課題組在前期研究中,已從青海鹽湖鹵水中提取出了高純度的氯化銣[9-10].本論文以此氯化銣為原料制備出了含銣的固體超強堿,再以三醋酸甘油酯為模型化合物,以制備的含銣固體超強堿做催化劑,模擬生物柴油制備工藝中的催化酯交換反應,探索了最佳的催化劑制備條件和催化酯交換反應條件.研究結(jié)果將為合理利用我國鹽湖鹵水中銣元素提供一條新的途徑.
湖南大學學報(自然科學版)2015年
第12期陽衛(wèi)軍等:含銣固體超強堿Rb2O/γ-Al2O3的制備及其催化酯交換反應研究
1 實驗部分
1.1 實驗試劑與儀器