Study On The Preparation And Catalytic Performance Of Carbon-based Solid Acid From Distillers’ Grains

Acid catalysts play an important role in petroleum refining and chemical industry.Homogeneous catalysts show a better catalytic performance in esterification, so it is used in industrial production widely. However, it has some potential drawbacks such as environmental pollution, equipment corrosion, difficult to purification of the product and difficult to recycle. Taking those drawbacks into consideration, the heterogeneous catalysts have been paid much attention. Nevertheless, solid acid catalysts also have some common shortcomings: high costs and low acid site density.It’s more meaningful to develop a low-cost and high efficiency solid acid from biochar. As a matter of fact, the application of solid acid has been attracted much attentions recently years. In this work, sulfonated carbon-based solid acid catalyst and supported phosphotungstic acid on biochar were prepared by distillers’ grain. The phase composition, structure, surface acidity of the as-prepared catalysts were characterized by X-ray diffraction, FT-IR, XPS, TQ 31P MAS NMR, N2 adsorption-desorption, NH3-TPD ,elemental analysis acid-base titration method. The catalytic performance and stability of catalyst were evaluated in the esterification of acetic acid and n-butanol as a probe reaction,the selectivity of the catalyst was studied by gas chromatography, infrared spectrum and the refractive index. The sulfonated carbon-based solid acid catalyst was used to catalytic the synthesis of n-butyl lactate. The main results are as follows:(1) Response Surface Methodology was adopted to determine the optimal preparation conditions for producing sulfonated carbon-based solid acid catalyst by simultaneous carbonization and sulfonation of distillers’ grains with concentrated H2SO4. The conversion of acetic acid was 97.6 % when the sulfuric acid concentration of 85 wt%, preparation temperature of 20 ℃, preparation time of 1.4 h,acid density of 1.73 mmol/g. The catalyst performance will weaken with the increase of reuse times, but it could be regenerated by treatment with 85 wt% sulfuric acid.The catalyst also has high activity and selectivity in the catalytic the synthesis of n-butyl lactate.(2) Biochar was used as catalyst carriers, a series of supported phosphotungstic acid catalysts were prepared by impregnation method. The better catalystic performance can obtained over the loading of phosphotungstic acid was 50 wt%, and its specific surface area was 415 m2/g. Phosphotungstic acids keep Keggin structure absorb uniformly on the surface or into the internal. The optimum reaction conditions for esterification over biochar supported phosphotungstic acid catalyst were the dosage of catalyst was 0.008 g/g, mole ratio of alcohol to acid was 1.4, reaction time was 2.0 h.The conversion of acetic acid was 97.4 % under the above reaction conditions. The conversion of acetic acid was still 91.3 % after recycled five times.