Research On Preparation Of The Activated Carbon For Gasoline Adsorption From Datong Coal

Gasoline is light oil, which is easy to evaporate during use and transportation to pollute the air. At present, the gasoline emission in China is controlled mainly by carbon canister with activated carbon as adsorbent. The carbon canisters are used to adsorb escaped gasoline vapor when the engine is off and when the engine works again, the gasoline vapor adsorbed on the activated carbon is blown out by air and enters the engine to burn. China is the largest automobile producer and consumer in the world, a large amount of special activated carbon to be used to produce carbon canisters each year, so it is very important to study the activated carbon with high efficiency gasoline vapor adsorption.Based on the research of the raw material ratio, carbonization temperature and heating rate, activation temperature, burn-off, the optimum preparation conditions were determined according to hardness and butane work capacity. Meanwhile, the pore structure of activated carbon was determined by nitrogen adsorption method, the relationship between the butane adsorption properties of the activated carbon and the pore structure was studied to determine the optimum pore size range suitable for butane adsorption. In addition, this paper also identified the relationship between butane adsorption properties and iodine value, methylene blue adsorption, caramel adsorption. Finally, the kinetic analysis of the activated carbon adsorption was carried out to determine the appropriate kinetic equation, which provides a theoretical guidance for the application of activated carbon in the field of gasoline adsorption.The optimum preparation conditions were obtained through the study of the process conditions. The experiment results show that the optimal conditions are 90% of Da Tong coal, 10% of Shan Dong coal, 960℃ of activation temperature, 650℃ of carbonization temperature, 12℃/min of carbonization heating rate, and 85% of burn-off. Under the conditions, the activated carbon is 92.0% in hardness, 0.296 in apparent density, 11.70g/100 mL in butane work capacity, 1494m3/g in surface area, 1.11m3/g in total pore volume.The burn-off has a significant effect on the hardness and the butane adsorption properties of activated carbon, the higher the burn-off is, the lower hardness is, but the better butane adsorption properties are. The 80%-85% of burn-off is beneficial to protect the hardness and improve the butane adsorption properties of activated carbon. The higher carbonization temperature is beneficial to the improvement of the butane adsorption properties. Besides, a slower carbonization heating rate leads to a less content of colloid, as a result of an increase of the butane absorption properties of the activated carbon. However, the hardness of the activated carbon is decrease due to pulverized coal particle unable to bond sufficiently. Inaddition, the activation temperature has little effect on the butane adsorption properties of activated carbon, and the higher activation temperature can shorten the production cycle.By analyzing the relationship between the butane adsorption properties and pore structure of activated carbon, the results show that the increase of total pore volume and average pore diameter is beneficial to the improvement of the butane work capacity of the activated carbon. The pore volume within 1.42-4.82 nm is propitious to the improvement of the butane work capacity of the activated carbon, and the pore volume between 0.79-1.10 nm will lead to the increase of the butane retentivity of the activated carbon.The conventional indicators including iodine number, methylene blue adsorption, caramel adsorption and the butane adsorption propertiess of the activated carbon were analyzed, the results show that the linear relationship between butane adsorption properties and methylene blue adsorption, caramel adsorption is appropriately, and there is no linear relationship between butane adsorption properties and iodine number. Furthermore, the activated carbon with above 60% of caramel adsorption, 320mg/g of methylene blue adsorption is more than 10g/100 mL in butane work capacity.The results of butane adsorption kinetics experiment of the activated carbon show that the temperature has effect on the adsorption capacity of butane, the lower the temperature is, the more butane is adsorpted by activated carbon; the butane flow rate mainly affect the time to reach adsorption equilibrium, the higher the butane flow rate is, the faster the adsorption equilibrium is reached. In the nitrogen desorption experiments, the nitrogen flow rate increases, the desorption amount of butane is higher. By fitting the kinetic equation, Bngham equation is the most suitable to fit the adsorption and desorption experimental data, the R2 is more than 0.99, this equation is appropriate for describing the butane adsorption and desorption process of the activated carbon.