Preparation And Catalytic Performance Of Carbon-based Solid Acid Catalyst From Biomass Materials

At the initial period of biodiesel development,one of the most widely used catalysts was concentrated sulfuric acid,its main shortcomings were difficulty in separation of product and catalyst,strong corrosion to reaction device and environmental pollution of waste liquid etc. To solve the above problems,solid acid catalysts were introduced to substitute homogeneous catalysts.Nowadays,most widely investigated solid acid catalysts were molecular sieve,ion exchange resin,heteropoly acid and solid super-acid etc,but they are exposed of obvious shortcomings in the use,such as high cost,low catalytic activity and low stability.Therefore, investigation on preparation and application of a novel and cheap biodiesel solid acid catalyst were of great realistic meaning and practical value.This thesis took natural biomass wooden powder as raw material and biomass carbon-based solid acid catalyst was prepared by carbonizatin-sulphonation method.Effects of preparation parameters on catalytic properties were discussed and as a result got the optimal preparation condition.Results indicate that carbonization and sulphonation temperature had significant effects on catalytic activity of carbon-based solid acid catalyst.Appropriate carbonization temperature and time are 400℃and 30 min;suitable sulphonation temperature and time are 135℃and 60 min.Thermo-gravimetric analysis(TGA),X-ray diffraction(XRD),Fourier transformation infrared spectrometry(FT-IR),High resolution transmission electron microscopy(HRTEM) and elemental analysis(EA),X-ray photoelectron spectroscopy analysis(XPS) were taken to characterize biomass carbon-based solid acid catalyst.HRTEM and XRD analysis show that biomass carbon-based solid acid catalyst has turbostratic carbon structure made up of countless small particles microcrystalline,the gap between microcrystalline particles and between mocrocrystalline layers reached nano-scale.FT-IR and XPS analysis indicate that the sulfuric acid group(-SO₃H) does exist in the catalyst.EA result shows that sulfuric acid group (-SO₃H) content in the optimal condition catalyst reach as high as 13.25%.TGA result shows that biomass carbon based solid acid catalyst has good thermal stability in the air under 220℃.Traditional esterification device has disadvantages of long reaction time,unstable reaction system,large amount of catalyst dosage and low reaction efficiency etc.The rectifying to remove water and continuous esterification device was designed and effectively solved problems existing in the traditional esterification reactor.In the rectifying to remove water and continuous esterification device,and the optimum reaction condition was determined by optimizing the parameters of esterification reaction,that is:methanol to oleic acid molar ratio of 6:1,catalyst dosage of 5%oleic acid weight,esterification temperature of 90℃and reboiler temperature of 65℃and esterification time of 2 h.Biomass carbon-based solid acid catalyst has many merits such as excellent catalytic efficiency,good stability,easy reusability,environmental friendliness,low cost and etc.All the advantages make it possible for biomass carbon-based biodiesel catalyst to become one of the most potential "green catalysts" in the 21st century,and it will play an important role in pre-esterification treatment of high acid-value waster cooking oil and easterification production of biodiesel.