Studies On The Structure Modification Of The Activated Carbons Used For Gasoline Saturated Vapour Recovery

There are many serious problems such as gasoline evaporation and loss during gasoline storage, transportation and utilization. The gasoline vapour which is dispersed is the major component in the formation of photochemical smog, which has seriously affected the atmospheric environment. So the study on gasoline vapour recovery and utilization has recently attracted increasing interest. Gasoline vapour recovery methods mainly include absorption, adsorption, condensation and membrane separation, and adsorption is an effective gasoline vapor recovery technology. However, now there are shortcomings such as low surface area and pore volume, small pore size in commercial activated carbon used for adsorbent in the adsorption method. The shortcomings are disadvantageous to gasoline vapour recovery and utilization. The main purpose of this paper is to seek simple modification methods to improve the activated carbon absorption /desorption properties on the gasoline saturated vapour, and expand the utilization of the recovered gasoline vapour, increase the pentane weight percent in desorption gas, this will be conducive to the separation and the utilization of pentane.Firstly, the chemical structures of the surface of commercial activated carbon A particles were modified by nitric acid, hydrogen peroxide, ammonia, hydrogen, acid and alkali. The surface functional groups were analysed according to Boehm titration. The pore structure of the carbons were characterized by nitrogen adsorption/deorption at low temperature. The dynamic state adsorption/ desorption equipment was set up, and the effects of modification agent concentration on the surface functional groups, pore structure and the pentane weight percent in desorption gas were studied by adsorption/desorption of the 90# gasoline saturated vapour on various kinds of activated carbons in this equipment and the TPD experiment. Results showed that ammonia, hydrogen, acid and alkali treatment improved the absorption / desorption properties of activated carbon on the gasoline saturated vapour, and the modified carbon based on 10% alternate acid and alkali treatment was the best one. The pentane enrichment results of desorption gas showed that nitric acid and ammonia treatment were better than the others, and the optimum concentration was 10%, 20% respectively.Secondly, the physical structure on the surface of commercial activated carbon B particles were modified by potassium hydroxide. The pore structure of the carbons were characterized by nitrogen adsorption/desorption at low temperature. The effects of alkali/carbon ratio, activation temperature, activation time on the pore structure and the pentane weight percent of desorption gas were studied by adsorption/desorption of 90# gasoline saturated vapour on various kinds of activated carbons in the dynamic state adsorption/ desorption equipment and the TPD experiment. Results showed that the absorption/desorption properties of the activated carbon to the gasoline saturated vapour were affected by various structutural parameters, and microporous surface area was the most important factor. Besides, large mesopore volume and wide pore size distribution were conducive to the absorption / desorption of gasoline saturated vapour. At the same time the optimal modification conditions were obtained as follows: alkali/carbon ratio of 1.4, activation temperature of 800℃, activation time of 120 minutes.