Performances of functional groups and KOH-transformation in corn stover waste through catalytic pyrolysis

Abstract

Catalytic pyrolysis can enhance the value of corn stover waste (CSW) by converting it into the functionalized carbon-based material. Understanding of the performance of functional groups in the CSW via catalytic pyrolysis, including catalyst transformation, is essential for the productive utilization of biomass waste. In this research, the changes of surface functionalities on the CSW and catalyst behavior by pyrolysis temperature in the range of 400–700 °C under N2 atmosphere and the KOH-catalyst loading in the range of 0.5 to 3 M were investigated. The surface functional groups on carbon materials were analyzed by using Fourier-transform infrared spectroscopy (FTIR) technique whilst the KOH-transformation was examined for crystalline structures by using X-ray diffraction (XRD) technique. From the FTIR results, in case of without catalyst the increase of pyrolysis temperature led to the decrease of surface functional groups which were hydroxyl, alkyl, carboxyl, carbonyl, ketone, ester and especially ether groups. However, at high temperature of 700 °C the graphite structure could be formed due to high polymerization reaction and more condensed carbon structure. The increase in concentration of KOH-catalyst from 0.5 to 3 M resulted in the increase of band intensities of OH stretching, CO stretching and KO vibration which could confirm the deposition of KOH-catalyst on the CSW surface. The maximum intensity of the functional groups was derived from the catalytic pyrolysis at a temperature of 400 °C with the KOH-catalyst concentration of 1 M. After the catalyst removal, the functional group of carbonate ion (CO32−) disappeared which became carbonaceous material. In terms of analysis of KOH-transformation by XRD, the KOH-catalyst could transform to crystalline compounds such as K2O, KHCO3 and K2CO3. The catalytic pyrolysis at pyrolysis temperatures of both 400 and 700 °C with the KOH-catalyst concentration of 1 M was transformed into KHCO3 in contrast to KOH at the concentration of 3 M, which was transformed into K2CO3. The investigation illustrated that KOH-transformation at 1 M and 3 M similarly presented K2O crystallite. Overall, the FTIR spectra accorded with XRD result of carbon materials obtained showed the KOH-transformation pathways in this research. This research work lies in the fact that the pyrolysis temperature in cases of without/with KOH-catalyst used in pyrolysis process can impact upon the surface functional groups on the carbon-based material and KOH-transformation.