摘要
In this study, biodiesel was produced from waste vegetable oil using a heterogeneous base catalyst synthesized by impregnating potassium hydroxide(KOH) onto diatomite. Response surface methodology based on a central composite design was used to optimize four transesterification variables: temperature(30–120 °C), reaction time(2–6 h), methanol to oil mass ratio(10%–50%) and catalyst to oil mass ratio(2.1%–7.9%). A quadratic polynomial equation was obtained to correlate biodiesel yield to the transesterification variables. The diatomite–KOH catalyst was characterized using X-ray diffraction(XRD), Fourier transform infra-red spectroscopy(FTIR) and a scanning electron microscope(SEM) equipped with an energy dispersive X-ray detector(EDS). A maximum biodiesel yield of 90%(by mass) was obtained. The reaction conditions were as follows: methanol to oil mass ratio 30%, catalyst to oil mass ratio 5%, reaction time 4 h, and reaction temperature 75 °C. The XRD, FTIR and SEM(EDS) results confirm that the addition of KOH modifies the structure of diatomite. During impregnation and calcination of the diatomite catalyst the K2 O phase forms in the diatomite structural matrix and the active basicity of this compound facilitates the transesterification process. It is possible to recycle the diatomite–KOH catalyst up to three times. The crucial biodiesel properties from waste vegetable oil are within the American Standard Test Method specifications.
In this study, biodiesel was produced from waste vegetable oil using a heterogeneous base catalyst synthesized by impregnating potassium hydroxide（KOH） onto diatomite. Response surface methodology based on a central composite design was used to optimize four transesterification variables： temperature（30–120 °C）, reaction time（2–6 h）, methanol to oil mass ratio（10%–50%） and catalyst to oil mass ratio（2.1%–7.9%）. A quadratic polynomial equation was obtained to correlate biodiesel yield to the transesterification variables. The diatomite–KOH catalyst was characterized using X-ray diffraction（XRD）, Fourier transform infra-red spectroscopy（FTIR） and a scanning electron microscope（SEM） equipped with an energy dispersive X-ray detector（EDS）. A maximum biodiesel yield of 90%（by mass） was obtained. The reaction conditions were as follows： methanol to oil mass ratio 30%, catalyst to oil mass ratio 5%, reaction time 4 h, and reaction temperature 75 °C. The XRD, FTIR and SEM（EDS） results confirm that the addition of KOH modifies the structure of diatomite. During impregnation and calcination of the diatomite catalyst the K2 O phase forms in the diatomite structural matrix and the active basicity of this compound facilitates the transesterification process. It is possible to recycle the diatomite–KOH catalyst up to three times. The crucial biodiesel properties from waste vegetable oil are within the American Standard Test Method specifications.
基金
support by the centre of research excellence(Vaal University of Technology)grant no 2188-2892 to fund this project is gratefully acknowledged
