Abstract
There is a significant interest in converting eggshells into value-added products. Therefore, the goal of this research is to synthesize and study iron-impregnated eggshells as a catalyst for partial oxidation of methane. The objectives of this research were to test the effects of iron loading, flow rate, oxygen concentration, and temperature on methane oxidation. The catalysts were synthesized using ferric chloride hexahydrate at various loadings and tested in a heated stainless-steel reactor under different experimental conditions. The reaction products included C2–C7 hydrocarbons, carbon monoxide, and carbon dioxide depending on the reaction conditions. Results indicated that iron loading beyond 5 wt% caused a decrease in methane conversion. A decrease in oxygen concentration enhanced methane conversion with a substantial drop in the production of CO2. Besides, an increase in temperature resulted in a decrease in methane conversion with a simultaneous increase in the production of CO2 via overoxidation. The reusability experiments indicated that the catalyst was active for four reaction cycles. Our results indicate that eggshells can be used as catalyst support for methane partial oxidation and can simultaneously solve the waste disposal problems faced by the poultry industry.
Highlights
The poultry industry worldwide produces over 8.4 billion kilograms of eggshells each year most of which is disposed as landfill wastes (Laca et al 2017; Shahbandeh 2020)
Aqueous F eCl3 may have reacted with C aCO3 in the eggshell to exchange chlorine as well as to change the pH substantially because of the release of HCl and CO2 (Eqs. 1 and 2): FeCl3 + 3H2O ⇋ Fe(OH)3 + 3HCl
Effect of temperature The results suggested that the fractional conversion of methane for iron-impregnated eggshell catalysts decreased with increasing temperature (Fig. 6a)
Summary
The poultry industry worldwide produces over 8.4 billion kilograms of eggshells each year most of which is disposed as landfill wastes (Laca et al 2017; Shahbandeh 2020). Eggshells consist of calcium carbonate (~ 98%), magnesium (~ 0.9%), phosphorus (~ 0.9%), and organic semipermeable membrane structures (Waheed et al 2019; Simpson et al 2019). Due to the presence of calcium and organic semi-permeable membranes in eggshells, several authors proposed the use of eggshells as adsorbents and catalysts. Besides transesterification catalysts and adsorbents, calcium-rich eggshells could potentially be used as precursors in selective oxidation of methane. Methane constitutes about 80–90% of natural gas that is abundantly available (Horn and Schlögl 2015). Based on 2018 calculations, the world annual production of natural gas has crossed 3,900 billion cubic meters (International Energy Agency 2019). As suggested by Sharma et al (2020), transforming methane into fuels and chemicals is of high priority
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