固体酸碱催化剂的制备、表征及其在两步法制备生物柴油中的应用

发布时间：2018-05-30 22:05

本文选题：生物柴油 + 固体酸碱　；参考：《合肥工业大学》2011年博士论文

【摘要】：我国生物柴油生产普遍采用的液体酸碱两步催化法首先是使用浓硫酸(H_2SO_4)催化油脂中游离脂肪酸生成脂肪酸甲酯(生物柴油),再利用氢氧化钠(NaOH)催化甘油三酯生成脂肪酸甲酯,催化剂溶于反应体系,反应后需要中和、水洗和干燥,造成过多的废水排放和能量消耗。而固体酸碱催化剂不溶于反应体系当中,反应后离心即可去除催化剂,以固体酸碱催化剂代替H_2SO_4和NaOH,生产过程中的废水排放和能量消耗会显著减少,生产成本也相应降低。本论文分别选用Na_3PO_4和Zr(SO_4)_2·4H_2O为活性化合物,γ-Al_2O_3和硅藻土为载体,进行了新型负载型固体碱催化剂Na_3PO_4/γ-Al_2O_3和固体酸催化剂Zr(SO_4)_2-Kieselguhr的制备和表征研究,并利用自制的固体酸和固体碱催化剂在20 L中试规模装置上进行放大试验,制备了符合GB/T20828-2007的生物柴油产品。主要内容和结果如下: (一)以磷酸钠(Na_3PO_4)为催化剂,考查了其在催化菜籽油与甲醇的转酯化反应中的催化特性。考察了Na_3PO_4在不同反应条件下的转酯化效果,比较了Na_3PO_4和文献上发表的一些固体和液体催化剂在催化生物柴油制备上的活性;检测了不同反应条件下Na_3PO_4在相应产物中的残留;考察了催化剂的重复使用效果。结果表明在在催化剂用量3 wt%,醇油摩尔比9:1,反应温度343 K和搅拌转速600 rpm的条件下,20 min内生物柴油的产率就可以达到95%,与液体碱催化剂的活性相近;Na_3PO_4在生物柴油中的残留很少,催化剂能够重复使用8次。 (二)以四水合硫酸锆(Zr(SO_4)_2·4H_2O)为催化剂,催化菜籽油脂肪酸主要组成成分-油酸与甲醇的酯化反应制备油酸甲酯(脂肪酸甲酯的主要组成部分)。考察了Zr(SO_4)_2·4H_2O在不同反应条件下催化酯化反应得活性并利用建立的一种拟均相反应动力学模型拟合实验结果;考察了Zr(SO_4)_2·4H_2O在甲醇中的溶解;考察了Zr(SO_4)_2·4H_2O的重复使用效果以及不同方法对催化剂的活性恢复效果。Zr(SO_4)_2·4H_2O在在催化剂用量3 wt%,反应温度333 K,醇酸摩尔比12:1以及搅拌转速600 rpm条件下能转化95%以上的油酸为油酸甲酯, SO42-能溶于甲醇当中导致催化剂在重复使用4次后活性下降,通过硫酸(H_2SO_4)负载的方法能恢复Zr(SO_4)_2·4H_2O的活性。 (三)以Na_3PO_4为活性化合物,γ-Al_2O_3为载体,浸渍法制备Na_3PO_4/γ-Al_2O_3负载型催化剂。考察了制备条件(Na_3PO_4负载量、焙烤温度和焙烤时间)对催化剂活性的影响,通过各种仪器表征方法考察了制备条件对催化剂结构的影响,探索活性与结构之间的关系;以活性最高的Na_3PO_4/γ-Al_2O_3为催化剂,催化菜籽油与甲醇反应制备生物柴油,考察反应温度、催化剂用量和醇油摩尔比对生物柴油产率的影响;考察了催化剂的重复使用效果,利用XRF等方法探索了催化剂在重复使用过程中的失活原因并建立了活性再生方法。结果表明固体碱催化剂的碱性、碱量、孔径尺寸,Na_3PO_4中所含结晶水个数对活性有影响;Na_3PO_4/γ-Al_2O_3在最优条件下的生物柴油转化率超过95%;催化剂能够重复使用4次,在使用过程中Na_3PO_4逐渐转变为Na_2HPO_4和NaH2PO4,通过碱洗把它们转变回Na_3PO_4后,活性得到恢复。 (四)以Zr(SO_4)_2·4H_2O为活性化合物,硅藻土为载体,制备了Zr(SO_4)_2-Kieselguhr固体酸催化剂。考察了制备条件(Zr(SO_4)_2负载量、焙烤温度和焙烤时间)对催化剂活性的影响,并把活性变化与催化剂结构、活性化合物的变化联系起来;以活性最高的Zr(SO_4)_2-Kieselguhr为催化剂,催化油酸与甲醇反应制备油酸甲酯,考察反应温度、催化剂用量和醇酸摩尔比对油酸甲酯产率的影响;利用XRF等方法考察了催化剂重复使用过程中的活性变化,探索了催化剂失活原因并建立了活性再生方法。催化剂的酸性、酸量、孔径和Zr(SO_4)_2中结晶水个数对活性影响较大,最理想条件下Zr(SO_4)_2-Kieselguhr催化的最佳酯化产率可达95.2%,催化剂在重复使用4次过程中SO_4~2-逐渐流失导致失活,重新负载Zr(SO_4)_2后活性得到恢复。 (五)分别以Na_3PO_4/γ-Al_2O_3和Zr(SO_4)_2-Kieselguhr为固体酸碱催化剂,固体酸碱两步法催化菜籽毛油与甲醇反应制备生物柴油。在酸催化中考察了催化剂用量、反应温度和醇油摩尔比对生物柴油产率的影响;在碱催化中考察了催化剂用量、反应温度、醇油摩尔比、酸催化时间和甲醇添加方式对生物柴油产率的影响,并利用二次旋转正交法优化碱催化反应。建立了生物柴油固体酸碱两步法20 L中试工艺和生物柴油后处理工艺,本工艺所制备的生物柴油产率可达97.6%,产品符合国家标准GB/T20828-2007,与液体酸碱两步法比较,该工艺可节省热能7.6%,节省电能43.6%,废水排放降低一半。
[Abstract]:The two - step catalytic method of liquid acid and alkali used in biodiesel production in China firstly uses concentrated sulfuric acid ( H _ 2SO _ 4 ) to catalyze free fatty acid in oil to produce fatty acid methyl ester ( bio - diesel oil ) , then uses sodium hydroxide ( NaOH ) to catalyze triglyceride to form fatty acid methyl ester . The catalyst is dissolved in the reaction system . After the reaction , the catalyst can be removed . The solid acid - base catalyst is not dissolved in the reaction system . After the reaction , the catalyst can be removed . The solid acid - base catalyst can replace H _ 2SO _ 4 and NaOH , and the wastewater discharge and energy consumption in the production process can be reduced significantly , and the production cost is correspondingly reduced .

The preparation and characterization of Na _ 3PO _ 4 / 纬 - Al _ 2O _ 3 and solid acid catalyst Zr ( SO _ 4 ) _ 2 - Kipling were carried out by using Na _ 3PO _ 4 and Zr ( SO _ 4 ) _ 2 路 4H _ 2O as the active compound .

( 1 ) The catalytic properties of sodium phosphate ( Na _ 3PO _ 4 ) in the transesterification of rapeseed oil and methanol were investigated .

The transesterification effects of Na _ 3PO _ 4 under different reaction conditions were investigated . The activities of Na _ 3PO _ 4 and some solid and liquid catalysts in the preparation of biodiesel were compared . The results showed that the yield of the biodiesel was 95 % under the conditions of 3 wt % of catalyst , 9 : 1 molar ratio of alcohol oil , 343 K of reaction temperature and 600 rpm , and the activity of the catalyst was similar to that of the liquid base catalyst . The residual of Na _ 3PO _ 4 in biodiesel was little , and the catalyst could be reused 8 times .

( 2 ) The main components of methyl oleate ( fatty acid methyl ester ) were prepared by esterification of oleic acid with methanol by using zirconium sulfate tetrahydrate ( Zr ( SO _ 4 ) _ 2 路 4H _ 2O ) as catalyst .

The effects of Zr ( SO _ 4 ) _ 2 路 4H _ 2O on the catalytic esterification of Zr ( SO _ 4 ) _ 2 路 4H _ 2O in methanol were investigated . The effect of Zr ( SO _ 4 ) _ 2 路 4H _ 2O on the activity of Zr ( SO _ 4 ) _ 2 路 4H _ 2O was investigated . The activity of Zr ( SO _ 4 ) _ 2 路 4H _ 2O was investigated . The activity of Zr ( SO _ 4 ) _ 2 路 4H _ 2O was recovered by means of sulfuric acid ( H _ 2SO _ 4 ) loading .

( 3 ) Na _ 3PO _ 4 / 纬 - Al _ 2O _ 3 supported catalyst was prepared by impregnation method with Na _ 3PO _ 4 as active compound and 纬 - Al _ 2O _ 3 as carrier .

The effects of the preparation conditions ( Na _ 3PO _ 4 loading , baking temperature and baking time ) on the activity of the catalyst were investigated . The effects of the preparation conditions on the catalyst structure were investigated by various instrument characterization methods . The results showed that the conversion of Na _ 3PO _ 4 / 纬 - Al _ 2O _ 3 in the process of reuse was more than 95 % . The results showed that the activity of Na _ 3PO _ 4 / 纬 - Al _ 2O _ 3 was more than 95 % .

( 4 ) Zr ( SO _ 4 ) _ 2 路 4H _ 2O as active compound and diatomite as carrier , Zr ( SO _ 4 ) _ 2 - Kilowsolid acid catalyst was prepared .

The effects of preparation conditions ( Zr ( SO _ 4 ) _ 2 loading , baking temperature and baking time on the activity of catalyst were investigated . The effects of reaction temperature , catalyst dosage and molar ratio of alcohol and acid on the yield of methyl oleate were investigated by reaction of oleic acid with methanol .

( 5 ) Using Na _ 3PO _ 4 / 纬 - Al _ 2O _ 3 and Zr ( SO _ 4 ) _ 2 - Kip1 as solid acid - base catalyst , the solid acid - base two - step method was used to catalyze the reaction of rapeseed crude oil with methanol to prepare biodiesel .

The effects of catalyst dosage , reaction temperature and molar ratio of alcohol and oil on the yield of biodiesel were investigated in acid catalysis . The effects of catalyst dosage , reaction temperature , molar ratio of alcohol and oil , acid - catalyzed time and methanol addition on the yield of biodiesel were investigated .
【学位授予单位】：合肥工业大学
【学位级别】：博士
【学位授予年份】：2011
【分类号】：TE667;TQ426.95

【引证文献】