农业工程学报Issue(1)：169-174,6.DOI:10.3969/j.issn.1002-6819.2014.01.022
碳基固体酸催化剂加压催化合成生物柴油
Synthesis of biodiesel using carbon-based solid acid catalyst under pressure
摘要
Abstract
Due to the environmental pollution caused by the widely use of and the depletion of fossil energy resources, the search for renewable energy has gained worldwide attention. Biodiesel has been considered as an alternativeto conventional fuels, because it is biodegradable and has high cetane number, low aromatic hydrocarbon content and excellent lubrication performance. Traditionally, the catalysts used for the esterification of inedible oil into biodiesel are liquid acids such as sulfuric acid, which is corrosive and difficult to reprocess. To alleviate these problems, a carbon-based solid acid catalyst was developed by the sulfonation of incompletely carbonized cellulose. The cellulose was heated at an 500℃ under N2 flow about 11 hrs to produce incomplete carbonization. The resulting material with 4 g was then ground to powders and heated in 50mL of concentrated H2SO4 (98%) under N2 flow to introduce SO3H into the aromatic carbon rings. The catalyst was characterized by a series of measurements. The layer structure was found from the Scanning Electron Microscope (SEM) image of the prepared carbon material. The BET result showed the catalyst had no pore structure on the SEM image. The powder X-ray diffraction (XRD) pattern of carbon material after the sulfonation showed broad and weak diffraction peaks attributable to amorphous carbon composed of aromatic carbon sheets oriented in a considerably random fashion. The temperature programmed desorption of NH3 (NH3-TPD) profiles showed that the catalyst had two distinct desorption peaks from 100 to 300℃and 750 to 800℃that were assigned to two types of acid sites. The low and high temperature peaks were corresponded to the weak and strong acid sites, respectively. The catalytic performance of the carbon-based solid acid catalyst for the synthesis of biodiesel was investigated via the esterification of palmitic acid and methanol. The effects of reaction conditions (molar ratio of methanol to palmitic acid, reaction temperature, reaction time and catalyst amount) on esterification efficiency were investigated. Comparison of catalytic activities among carbon-based solid acid catalyst, concentrated sulfuric acid and para-toluenesulfonic acid were conducted under pressure. The results indicated that the optimal molar ratio of methanol to palmitic acid, reaction temperature, reaction time and catalyst amount was 10:1, 110℃, 2h, and 5%(based on the mass of palmitic acid), respectively. The catalytic activity of carbon-based solid acid catalyst was higher than the other two catalysts. In order to evaluate the reusability, the catalyst was recovered for further conversion of palmitic acid under the optimized conditions through simple filtering. The conversion ratio was still above 60% after the catalyst was reused for four times. The gas chromatograph-mass spectrometer was used for analyzing the product oil components. The content of the fatty acid methyl esters in the product oil was 93.8%, which consisted mainly of hexadecanoic acid methyl ester of 11.8%, octadecadienoic acid methyl ester of 26.6%, eicosenoic acid methyl ester of 10.7%, docosenoic acid methyl ester of 10.6%and docosanoic acid methyl ester of 5.8%.关键词
生物柴油/催化剂/酯化反应/碳基固体酸Key words
biodiesel/catalysts/esterification/carbon-based solid acid分类
化学化工引用本文复制引用
司展,蒋剑春,王奎,徐俊明..碳基固体酸催化剂加压催化合成生物柴油[J].农业工程学报,2014,(1):169-174,6.基金项目
林业公益性行业科研专项经费资助（201204801）；国家自然科学基金 （）
