Research On Deep Desulfurization Of Diesel Oil With Reaction/adsorption Method

During the industrialization, more and more people realized the importance of protecting the environment. In the past decade, lots of stringent regulations for gas oil and diesel oil are issued by developed counties, such as USA, Japan and so on. China has recently created a miracle in its economic development, and it began to set down criteria for oils due to further deterioration of the environment. The aim to produce clean oil is to reduce sulfur in the oil.Based on adsorption technology, a new desulfurization technology was presented, which can be used to reduce total sulfur amount down to 15ppm, for solving problems presented in conventional HDS technology.The Condensation reaction/adsorption method, which was used for deep desulfurization in this paper, is combining a kind of condensation reaction of formaldehyde and thiophene while acid as a catalyst with adsorption technology. According to the previous works, oils contain not only some kind of oganic sulfur compounds, but also a certain amount of oganic nitrogen compounds. Those nitrogen compounds will compete with sulfur compounds during the process of adsorption and reaction due to the similarities of chemical structure and property between oganic heterocyclic nitrogen compounds and derivatives of thiophene, which results in lower efficiency of sulfur removal by condensation reaction/adsorption method. We prepared two kinds of model oil, one with only thiophene as solute was named as'MO', another one with thiophene, quinoline and indole as solute was named as'MDO'. It was demonstrated that the existing nitrogen compounds within oils have an effect on DSR removing sulfur compounds by batch reaction experiment. Then, two pretreating agents, phosphowolframic acid (PWA) and PTR (a certain amount of HNO3 loaded in silica gel), were selected to remove nitrogen compounds so that MDO can be further desulfurized by DSR. We fixed on a set of optimal operating conditions, such as temperature of 30℃and 40℃; weight ratio of 0.3 for HNO3 and SGB (B-type silica gel), weight ratio of 40 for MDO and SGB, weight ratio of 2.0: 35 for PWA and MDO; reaction time both of 3 hour, respectively for PTR or PWA pretreating MDO. Two catalytic diesel oils were pretreated under the optimal operating conditions, then a series of breakthrough and saturated capacities of DSR were tested by fixed adsorption-bed reaction. The results showed that the two catalytic diesel oils can be deeply desulfurized below 15ppm sulfur content after pretreated by PTR.It is necessary to remove nitrogen compounds before deep desulfurization. Further research should be done on how to take off those nitrogen compounds contained in oils and the denitrogenation mechanisms.