Study On Adsorbent Preparation And Adsorption Technology For Gasoline Deep Desulfurization

Selective adsorption is a prospective technique for gasoline deep desulfurization. Compared with hydrodesulfurization technique, Adsorption desulfurization technique offers several potential advantages: (1) the process is operated at ambient temperature and atmosphere, which leads to low investment and low operating cost; (2) the process is very effective for ultra-deep desulfurization of liquid hydrocarbon fuels; (3) there is no or quite little reduction of octane number. Key issue for the commercialization of deep adsorption desulfurization is to develop new adsorbents with higher sulfur capacity and desired stability. In this thesis, experimentally investigation related to new adsorbent preparation, the adsorbent performance evaluation and regeneration, and adsorption process was conducted fro gasoline deep desulfurization. Detailed achievements are given as follows:13X loaded with cuprous ion adsorbents were prepared by the impregnation method for modeling gasoline (C6-C8 alkane + thiophene) deep desulfurization. The effect of pretreatment and regeneration conditions on the desulfurization performance of the adsorbents were examined. The suitable pretreatment and regeneration conditions were determined experimentally as follows: the pretreatment conditions, reducing 3h at 500℃under the nitrogen; and the regeneration conditions, N2 flow rate 40mL/min, sweeping 4h at 200℃. Under the conditions above, the adsorbents showed excellent desulfurization performance and quite fair stability for modeling gasoline.The supports of adsorbent with different ratios of activated alumina, diatomite and zinc oxide were prepared by physical mixing. The effects of composition and addition of pore-expanding agent on special surface and pore size of the supports were investigated. Results show that the optimal ratio ofγ- Al2O3, SiO2 and ZnO is 2:1:2, the suitable pore-expanding agent PEG-1000 and suitable addition amount 15%. The adsorbents loaded with Ni and Co were prepared by combining ultrasound and ordinary impregnation. Desulfurization conditions for the prepared Ni-Co adsorbents were investigated under room temperature and atmosphere. Factors influencing the desulfurization performance of the adsorbents, including Ni/Co concentrations, impregnation time, microwave dry means and reduced temperature were investigated.Adsorption desulfurization experiments for FCC gasoline were carried out in a fixed bed adsorption unit. Desulfurziation performance of three adsorbents was comparatively examined. The composition and specific surface area of adsorbents were characterized using XRD and BET techniques. Effects of adsorption temperature, liquid hourly space velocity and hydrogen flow rate on sulfur content removal from FCC gasoline were investigated. The experimental results indicate that the preferable conditions for adsorption desulfurization are as follows: adsorption temperature 320℃, liquid hourly space velocity 2.0h-1, hydrogen flow rate 60～140mL/min. Under the conditions above, the breakthrough sulphur capacity of the adsorbent is about 6.94mg/g (assigned sulphur content of the effluent was 30mg/L as the breakthrough point).The suitable regeneration conditions of the Ni-Co adsorbents were: regenerated at 320℃about 4h under air with high purity. After four times regeneration, the sulphur capacity of the adsorbents decreased a little due to the high regeneration temperature which may cause the agglomeration of the adsorbents.