Preparation Of Rice Straw Carbon-Based Solid Acid And Their Application For ?-Pinene Synthesis Of ?-Terpineol

At present,the synthesis of?-pineneol from?-pinene in industry mainly uses dilute sulfuric acid as a catalyst.There are existed a serious problems that difficult to separate between the product and the catalyst,strong corrosion of the reaction equipment,and environmental pollution in the traditional process of?-terpeneol preparation.And the effectively ways of solution to problems are through introducing a solid acid catalyst.Biomass carbon-based solids have a good texture structure to meet the requirements of preparing active catalysts.There are existence great advantage that biomass solid acids to replace traditional liquid acid catalysts is not only conforms to the concept of green chemical industry,but also has easy access to raw materials and low prices.Therefore,the waste agricultures are use to preparation of biomass carbon-based solid acid catalyst with high catalytic activity and their application researchs have important social significance and practical value.In this paper,biomass carbon-based solid acid prepared via incomplete carbonization of rice straw?RS?and concentrated H₂SO₄sulfonation.Characterization of the structural characteristics and physical and chemical properties of rice straw biomass carbon-based solid acid were carried out Thermogravimetric?TG?,scanning electron microscope?SEM?,N₂physical adsorption-desorption apparatus?BET?,Fourier transform infrared spectroscopy?FT-IR?,Temperature programmed desorption?NH₃-TPD?,and X-ray photoelectron spectroscopy?XPS?analysis methods.And the catalytic performance of carbon-solid acid catalysts for?-pinene to?-terpineol was measured on a fixed reactor,study the influence of hydration reaction factors on the catalytic performance.Explore the preparation of biomass solid acid catalyst suitable for?-pineol hydration to prepare?-terpineol and its synthesis optimization process parameters.The main research contents and results are as follows:1.Explore the effect of carbonization temperature on the pore and morphology structure of carbon precursor and catalyst.As the carbonization temperature increases,an appropriate increase in the carbonization temperature is conducive to improving the pore structure of the carbon precursor,while excessively high temperature causes the carbon precursor to decompose.The S_BETand V_Totalof the carbon precursor showed a trend of increasing at first and then decreasing with the carbonization temperature increased.But in the subsequent sulfonation modification,the S_BETand V_Totalof the catalyst showed the opposite rules to the carbon precursor.When the carbonization temperature and sulfonation temperature is 300?and 80?,respectively,the S_BETand V_Totalof RS300-80 reach the maximum values of 420.9 m²/g and 4.048 cm^3/g,respectively.Low-temperature carbonization and sulfonation modification have almost no effect on RS's D_pore.The D_poreof a series of prepared carbon precursors and catalysts is about 3.85nm,which are all mesoporous materials.2.The carbon precursor?RS300?prepared by carbonization of rice straw at300?was used as the carrier,explore the effect of sulfonation temperature on the catalyst morphology and pore structure.The results show that with the increase of the sulfonation temperature,the catalyst morphology and structure did not excessively collapse and decompose,and S_BETand V_Totalshowed a trend of increasing first and then slightly decreasing with the increase of the sulfonation temperature.It shows that the sulfonation temperature has little effect on the morphology structure of the catalyst,but it can improve the pore structure of carbon precursors with"soft carbon"structure.3.The carbon precursor?RS300?prepared by carbonization of rice straw at300?was used as the carrier,explore the effect of sulfonation temperature on the acidity distribution of the catalyst.The results show that with the increase of sulfonation temperature,the amount of strong acid and weak acid increases first and then decreases,and the amount of medium strong acid continues to decrease.High temperature sulfonation is not conducive to the loading of sulfonic acid groups.When the sulfonation temperature is 80?,the acid content of the strong acid site of the catalyst reaches the maximum value 0.82 mmol/g,and the acid content of the medium strong acid and weak acid reaches 0.66 mmol/g and 1.39mmol/g,respectively,and the total acidity reaches 2.87 mmol/g.4.The conversion rate of?-pinene and the selection rate of?-terpineol as evaluation indicators,study the effects of RS carbonization temperature and sulfonation temperature on?-pinene hydration reaction under two-phase and three-phase reaction systems.The results show that under the two-phase reaction system,with the increase of carbonization and sulfonation temperature,the conversion rate of?-pinene increases,while selectivity of?-terpineol increases first and then decreases.The selectivity of?-terpineol reached the highest value of 57.07%,and the conversion rate of?-pinene was 67.60%.In the three-phase reaction system,as the carbonization temperature increases,the conversion rate of?-pinene first increases and then decreases,and the selectivity of?-terpineol continues to decrease;as the sulfonation temperature increases,although the conversion rate increases first and then decreases,the selectivity of?-terpineol decreases first and then increases.The conversion rate is higher than that of the two-phase reaction system,but the selectivity of?-terpineol decreases more than that of the two-phase reaction system.The conversion of?-pinene hydration to a maximum of 85.28%,the selectivity of?-terpineol is only 18.51%when RS300-50 as catalyst.5.Using RS300-80 as a catalyst to catalyze the hydration reaction of?-pinene,the optimized process parameters are determined through single factor experiments.The results showed that when the optimized reaction parameters were 0.5 g RS300-80,the water/?-pinene molar ratio was 10,5.25 ml of deionized water,20 ml of acetic acid,the reaction temperature at 80?for 24 h.The conversion of?-pinene and the selectivity of?-terpineol were reached67.60%and 57.07%,respective.6.The results of the catalyst service life experiment show that-HSO₃groups were successfully loaded on RS300 and connected with RS300 in the form of covalent bond,and the catalytic reaction activity of the catalyst had alternative stability.