Studies On Preparation And Catalytic Performances Of Coconut Char Sulfonic Acid

Traditional liquid acid such as sulfonic acid were often used as catalysts in industrial fields,however,such liquid-acid catalysts require special processing in the form of neutralization,which involves costly and inefficient catalyst separation from products and results in an unrecyclable sulfate waste.According to the strengthening of environmental awareness among the people and the increasing environmental protection requirements,production methods should be refined so as to minimize adverse effects on the environment or human health.The migration to strong solid acids,which are recyclable and nontoxic,from liquid acids such as sulfuric acid is therefore a desirable goal.So the solid acid catalyst research has been developed by leaps and bounds.At present,although organic-solid material of sulfonic acid has been widely used in industrial fields,it is difficult to overcome its own shortcomings such as high price,poor strength,easy expansion in organic solvents,and derived from non-renewable raw materials.Therefore,it is interesting and significant to prepare new solid sulfonic materials which can break away from non-renewable raw materials such as coal and petroleum and other mineral resources.In this paper,we focused on the development of a new solid sulfonic materials in catalytic field.Hainan Coconut Shell scrap as raw material, through decompression carbonizing and sulfuric acid catalytic charring methods to obtain the coconut shell char sulfonic acid(CSCSA),coconut shell charcoal and then be sulfonated acid.The different positions of coco, decompression carbonizing temperature and different disposal to the original materials for charring and sulfonation were studied in details. Under the optimized conditions the amount of acid of CSCSA can reach up to 0.8-1.5mmol/g mmol.g^_!.The coconut char and the prepared CSCSA were characterized by FT-IR,TG-DTG,XRD and acid-base titration.The results showed that the obtained char materials have polycyclic aromatic tings with a number of oxygen-groups and the prepared CSCSA showed an obvious C-S absorption peak in FT-IR spectrum.At the same time,this catalyst has good thermal stability of which sulfonic acid groups in the decomposition of weightlessness before 220℃and those solid acid prepared by the two types of methods are amorphous.The catalytic application of CSCSA were investigated in Biginelli reactions,Mannich reactions and ring-open reactions.The amounts of CSCSA and different solvents were studied on the Mannich reaction.The influenced factors of the synthesis were discussed and the optimal conditions were found as follows:the amount of catalyst was 2%mol with ethanol as solvent under 30℃.The catalytic efficiency of the novel solid acid was examined by comparing the catalytic effect of the reaction with sulfonated resins,sulfamic acid,sodiumhydrogensulfate,paratoluenesulfon acid,vitriol and so on.It is proved that CSCSA possess satisfactory catalytic activity.In order to show the generality and scope of this new protocol,we also surveyed the scope of arylaldehydes and amines which include 2-acetylpyrazine in the direct Mannich reactions and afforded the correspondingβ-amino carbonyl compounds in excellent yields.The new compounds are fully characterised by ¹H NMR spectroscopy.The CSCSA which was reused for 5 times also owned catalytic activity under normal temperature(30℃) in Mannich rections.The three-component Biginelli reaction of benzaldehyde,urea and ethylacetoacetate was examined.Several solvents and the amount of catalyst were investigated in the model reaction.The optimal conditions were found as follows:the amount of catalyst was 20%mol with ethanol as solvent.Used the novel solid acid,the 3,4-Dihydropyrimidin-2(1H)-ones derivatives were synthesized in moderate condition and resulted to high yields,which compared to that of vitriol,sulfonated resins,citric acid and so on.This new protocol for the Biginelli reaction includes the following important features:excellent yields,non-toxic, inexpensive and easily available reagent.In alcoholysis of epoxide which obtained high conversation and selectivity in short time with the CSCSA.But this catalyst also exists some shortages,especially in high temperature reaction system;In Mannich rections CSCSA still has a catalytic activity under normal temperature(30℃) when reused for 5 times,but catalytic activity come down quickly in Biginelli reaction under 80℃.As a novel solid acid catalyst,the universality of origin material,low toxicity and high catalytic activity make CSCSA catalysts attractive.