Preparation of activated carbon from petroleum coke by KOH chemical activation for adsorption heat pump

To achieve highly cold heat output of water vapor type adsorption heat pump (AHP), an attempt was made to improve the water adsorptivity of activated carbon in the operation relative pressure of AHP ranging from 0.11 to 0.38. In this study, petroleum coke was used as a raw carbonaceous material and was activated by KOH chemical activation method under nitrogen gas flow. The weight ratios of KOH to coke, R, were varied from 2 to 5, while the activation temperature was changed in the range of 773–1073 K. As a result, the porosity of activated carbon was found to increase with an increase in the activation temperature and weight ratio of KOH to coke. Further, it was found that, at the activation temperature of 773 K, the amount of acidic surface functional groups increased significantly with KOH/coke weight ratio. By contrast, the effect of KOH/coke weight ratio on the amount of acidic surface functional groups was negligible at 1073 K. Finally, the activated carbon prepared from petroleum coke at 873 K and R = 2 was characterized by 1.2 times higher adsorptivity of water vapor in the operation relative pressure of AHP than conventional silica gel.