Spontaneous Combustion Characteristics of Activated Carbon Modified via Liquid Phase Impregnation during Drying.

Spontaneous combustion characteristics are important issues for the safe operation of the wet-modified activated carbon drying process. The spontaneous combustion characteristics of activated carbon modified via liquid phase impregnation were fully investigated in this study. The modified activated carbon was prepared using columnar activated carbon and 4-amino-1,2-butanediol solution. Physical properties and surface functional group analyses were performed for activated carbon before and after modification. The ignition temperature of activated carbon before and after modification was then characterized using the methods of GB/T20450-2006, thermogravimetry-derivative thermogravimetry (TG-DTG), and TG-mass spectrometry (TG-MS). At the same time, the activation energy of activated carbon before and after modification was calculated by using thermodynamic analysis. Furthermore, a new self-designed test platform was introduced to investigate the spontaneous combustion characteristics of wet-modified activated carbon under the drying temperatures of 150, 175, 180, and 210 °C. The results show that the specific surface area of Brunauer, Emmett, and Teller (BET) is decreased by 368 m2·g-1, the total volume of pore size is decreased by 0.17 cm3·g-1, and the content of oxygen-containing functional groups is decreased by 0.071 mmol/g compared with row activated carbon. The ignition temperatures of the sample before modification characterized by the three methods are 483, 596, and 599 °C, respectively. The ignition temperatures of the sample after modification are 489, 607, and 611 °C, respectively. The activation energy of the modified activated carbon is increased by 35 kJ/mol compared to the original activated carbon. It is concluded that the temperature that triggers the modified activated carbon combustion during the drying process is between 175 and 180 °C, and the heat is mainly gathered at the longitudinal center of the combustion chamber through the investigation of spontaneous combustion experiments. The results in this study can contribute to safe production to prevent combustion in the process of modifying activated carbon during the drying process.

Quantitative Structure-Property Relationship Analysis for the Prediction of Propylene Adsorption Capacity in Pure Silicon Zeolites at Various Pressure Levels.

This work is devoted to the development of quantitative structure-property relationship (QSPR) models using various regression analyses to predict propylene (C3H6) adsorption capacity at various pressures in zeolites from a topologically diverse International Zeolite Association database. Based on univariate and multilinear regression analysis, the accessible volume and largest cavity diameter are the most crucial factors determining C3H6 uptake at high and low pressures, respectively. An artificial neural network (ANN) model with five structural descriptors is sufficient to predict C3H6 uptake at high pressures. For combined pressures, the prediction of an ANN model with pore size distribution is pleasing. The isosteric heat of adsorption (Q st) has a significant impact on the improvement of the prediction of low-pressure gas adsorption, which finely classifies zeolites into high or low C3H6 adsorbers. The conjunction of high-throughput screening and QSPR models contributes to being able to prescreen the database rapidly and accurately for top performers and perform further detailed and time-consuming computational-intensive molecular simulations on these candidates for other gas adsorption applications.