Studies On Preparation And Catalytic Performances Of Millet Char Sulfonic Acid

Along with the strengthening of environmental awareness among the people and the increasing environmental protection requirements, the solid acid catalyst research has also 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, and easy expansion in organic solvents, and derived from non-renewable raw materials such as coal and petroleum and other mineral resources. Therefore, it is interesting and significant to prepare solid sulfonic materials from biomass.In this paper, spherical millet has been used as a natural carbon source to prepare the millet char via decompression carbonizing. The effects of heating increase rate of temperature, the carbonization temperature, and the retention time at the carbonization temperate on the properties of the millet char were investigated. The millet char sulfonic acid (MCSA) was prepared via sulfonating the millet char by oleum. The amount of acid of MCSA influenced by the concentration of oleum, the temperature, the sulfonation time, and increase rate of temperature for sulfonation were studied in details. The amount of acid of MCSA was 1.00-1.80 mmol.g^-1 under the optimized conditions.The millet char and the prepared MCSA were characterized by FT-IR, TG-DTG, SEM, and XRD. FT-IR spectrum showed that the millet char converted to carbon-riched materials via decompression carbonizing. In addition, the prepared MCSA showed an obvious C-S absorption peak in FT-IR spectrum. TG-DTG studies showed that millet lost weight mainly at 250-300℃. Besides, the prepared MCSA showed a large lost-weight peak at 220℃. SEM studies showed that there were abundant honeycomb-shape channels on the surface of the millet char before and after sulfonation. XRD studies showed that amorphism degree of the millet char increased with the increase of cabornation temperature.This work focuses on the catalytic performance of MCSA in esterification, acylation of cyclohexene with formic acid and acetic anhydride, condension reaction of glycerol with ketones and aldehydes. In the esterification reactions which catalyzed by MCSA, the conversion of alcohols were above 90%, the selectivity of ester came up to 100%. MCSA had a perfect catalytic activity in condension reaction of glycerol with ketones and aldehydes, especially in condension reaction of glycerol with cyclohexantone which the conversion of cyclohexanone came up to 99%. MCSA which was reused for 8 times also had a catalytic activity. Results showed that MCSA had a better catalytic activity and good reusably.MCSA prepared with two-step synthesis method is a new type of biological carbon-based solid sulfonic acid, which expanded the research fields of biological carbon-rich solid sulfonic acid.