Abstract
This study aims to investigate the thermal behaviour of raw and phosphoric acid impregnated olive stones via coupled thermogravimetric analysis-Mass spectrometry (TGA-MS) during pyrolysis. The impregnated material was prepared at three H 3 PO 4 /precursor weight ratio of 0.5; 1 and 1.5; for various impregnation time of 3, 6 and 9 h, which was then subjected for thermal analysis. TGA profiles were obtained under dynamic conditions in temperature range 25 °C to 750 °C with a heating rate of 10 °C/min, using pure nitrogen as an inert gas. Thermal degradation of olive stones was observed in three stages namely dehydration, active and passive pyrolysis. Two-steps degradation of raw olive stone occurred, whereas the impregnated material displayed only one step. Addition of phosphoric acid sharply reduced the onset temperature of the main decomposition step. Onset temperatures decreased with increasing rate or time of impregnation. It could conclude that 3 h is sufficient as time of impregnation for activated carbon production. Examination of the main gas products were carried out using coupled TGA-MS. The principal permanent gases detected were H 2 , H 2 O, CO, CO 2 and the light hydrocarbons C 2 H 6 and CH 4 . Different kinetic scenarios of raw and impregnated olive stones were observed. The above results should be useful to understand the pyrolysis mechanism of phosphoric acid impregnated olive stone for improving activated carbon production.
Highlights
Activated carbons (AC) have been frequently applied in gas separation, solvents recovery, and water treatment and in catalytic processes [1,2,3,4,5]
OS have a high fixed carbon and volatile matter contents (21.64%, 67.88%, respectively), as well as other common biomass such as: orange waste [47], olive solid waste [21], almond shell [48], date kernel [49], C. monspeliensis [49], date stones [50]. This implies that olive stones could be an excellent precursor for activated carbon production instead of expensive raw materials widely used for producing activated carbon
In this study the thermal behaviour of raw and impregnated OS with different rate and time of impregnation during pyrolysis has been evaluated by means of thermogravimetric analysis-Mass spectrometry (TGA-mass spectrometry (MS))
Summary
Activated carbons (AC) have been frequently applied in gas separation, solvents recovery, and water treatment and in catalytic processes [1,2,3,4,5]. Several suitable agricultural by-products including olive stones [12], date stones [13], rice husks [14], plum stones [15] and pomegranate [16] have been studied as ACs precursors in many studies published over the last decades. These by products are abundant in some countries and do not have other direct technical applications and instead are discarded as wastes [17,18]
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