Design And Synthesis Of Hydrophobic Acidic Carbon Based On Diazo Reduction Method And Their Applications In Biofuel Synthesis

Environmental problems caused by the rapid consumption of fossil energy has become critical issues in recent years.In order to reduce human's over dependence on oil and alleviate the environmental problems such as greenhouse effect,the synthesis of alternative fuels based on biomass sources has attracted more and more attention.Among them,the first-generation biodiesel of fatty acid methyl esters obtained by esterification and transesterification of fatty acids and triglycerides with methanol has been extensively studied.Recently,based on lignocellulose derivatives,the alkylation reaction of 4-ethylphenol with benzyl alcohol and 2-methylfuran with small molecular aldehydes and ketones produced macromolecular fuel precursors,which were subsequently hydrogenated to obtain high biomass.The fuel synthesis route has slowly attracted the attention of researchers.Although both types of reactions can use acid catalysts,but the by-product water in the reaction is not only easily adsorbed on the acid sites,resulting in a decrease in the acid strength of the catalyst,but also triggers a series of side reactions that affect the selectivity of the target product.Therefore,it is of great significance to design and prepare a recyclable catalyst that is both hydrophobic and super acidic.In this paper,based on the diazo reduction reaction,a series of hydrophobic and strong acid carbon-based catalysts were designed and prepared for biodiesel and biomass high-density fuels.By changing the type and quantity of functional compounds,the acid amount,acid strength and hydrophobicity of the catalyst can be precisely adjusted.The main research contents and conclusions are as follows:(1)Hydrophobic acid activated carbon is prepared by grafting arenesulfonic acid groups with different carbon chain length onto commercial activated carbon via one-step diazo reduction reaction.It is used as potential catalyst for oleic acid esterification,oleic acid triglyceride ester transfer reaction and 2-methylfuran alkylation reaction.Among them,the hydrophobicity,acid strength and catalytic performance of AC-pNaphSO3H grafted with naphthalene sulfonic acid were significantly higher than those of the samples grafted with sulfuric acid or benzene sulfonic acid,indicating that the longer the carbon chain length of the grafted group,the higher the hydrophobicity and acid strength of the material,and the better the catalytic reaction.In the end,4.27wt%AC-pNaphSO3H achieved 96.7%and 86.3%conversion in the esterification and transesterification reactions respectively,88.3%in the alkylation reaction,and the target product selectivity was 86.2%,which was better than that of commercial ion exchange resin amberlyst-15.In addition,the conversion is still 88.5%after five cycles in esterification,which shows good catalytic performance.(2)The hydrophobic acid biochar is prepared by grafting acid benzene sulfonic acid group and hydrophobic tert-butylbenzene group on the biochar.The biochar with large specific surface area is obtained by activate the waste oil tea shell at high temperature.These catalysts are used for alkylation of 4-ethylphenol with benzyl alcohol and 2-methylfuran with cyclopentanone/cyclohexanone.This series of catalysts not only improve the acid amount and mass transfer rate of the reaction due to its large specific surface area,but also solve the problem that the high acid amount and hydrophobicity can not coexist through the second step of hydrophobic treatment,thus realizing the independent control of acid group and hydrophobic group.Compared with amberlyst-15 and 3.28wt%B-SO3H,these catalysts have higher catalytic activity and selectivity in the alkylation of 4-ethylphenol with benzyl alcohol and 2-methylfuran with cyclic ketones,which is of great significance for the preparation of high-density fuel.In addition,they have good stability and can be reused at least 5 times.(3)A series of hydrophobic superacid catalysts were successfully prepared by grafting halogenated benzenesulfonic acid group onto ter-butyl benzene group based on two-step diazo reduction method.This improvement enhances the acid strength of the catalyst while ensuring its excellent hydrophobicity.Compared with amberlyst-15 and 3.28wt%B-SO3H,these catalysts exhibit excellent catalytic activity and selectivity in the alkylation of 4-ethylphenol with benzyl alcohol and 2-methylfuran with cyclic ketones.These catalysts not only effectively reduce the negative effects of by-product water on the reaction,but also show good stability and catalytic performance in multiple cycle experiments.The work in this chapter provides an efficient and stable catalyst for complex reaction systems such as alkylation,and further promotes the application of the diazo reduction method in the functionalization of carbon materials,which is beneficial to its application in industrial production.