Gasoline desulfurization method

Abstract

The inventive gasoline desulfurization method includes performing cutting distillation on gasoline to obtain heavy fraction with high boiling range and light fraction having low boiling range; under selective hydrogenation desulfurization condition, contacting the heavy fraction and hydrogen gas with hydrogenation desulfurization catalyst to perform selective hydrogenation desulfurization, to obtain desulfurized heavy fraction; contacting the light fraction with alkali solution, to obtain sulfide-absorbed alkali solution and desulfurized light fraction; contacting the sulfide-absorbed alkali solution with oxidant, oxidation catalyst and a part of the desulfurized heavy fraction, to simultaneously perform alkali solution regeneration and desulfurization, so that sulfide salt in the alkali solution is oxidized into disulfide, which is extracted into the desulfurized heavy fraction; performing phase separation, and exhausting tail gas; returning at least part of the disulfide-absorbed heavy fraction to the heavy fraction after cutting distillation, to perform selective hydrogenation desulfurization; and mixing the desulfurized heavy and light fractions. The inventive method can obtain higher desulfurization rate and lower octane number loss.

Description

technical field [0001] The invention relates to a method for gasoline desulfurization. Background technique [0002] As we all know, the emission of toxic and harmful substances in automobile exhaust seriously affects the air quality. For this reason, countries all over the world have imposed stricter and stricter standards on the quality of oil used as engine fuel. On April 27, 2005, the State Environmental Protection Administration announced the emission standards of China's light-duty vehicles III and IV. Among them, No. Ⅲ emission standard for light vehicles came into effect on July 1, 2007, and No. Ⅳ emission standard came into effect on July 1, 2010. National No. Ⅲ and No. Ⅳ emission standards respectively stipulate that the sulfur content in motor gasoline shall not exceed 150 μg / g and 50 μg / g. It is expected that the national V emission standard will stipulate that the sulfur content in motor gasoline shall not exceed 10 μg / g. [0003] As we all know, the sulfur i...

AI Technical Summary

Problems solved by technology

This has two disadvantages: one is that the air flowing into the phase separation system is easy to form bubbles in the lye, which affects the sedimentation and separation of the regenerated lye and the disulfide phase or the solvent phase containing disulfide, so that the regenerated lye is still entrained. There are disulfides or solvents containing disulfides. When the regenerated lye is returned to the extraction system for recycling, the disulfides will be back-extracted into the gasoline raw material, and it is difficult to achieve the purpose of treating gasoline with lye for desulfurization; the second is It is difficult to completely remove the air contained in the regenerated lye or the fresh lye injected in the oxidation system. When the regenerated lye is returned to the extraction system for recycling, at least a part of the mercaptan in the hydrocarbon stream will be contained in the air in the lye and subsequently The disulfides generated under the action of the oxidation catalyst of the alkali liquor cycle remain in the hydrocarbon stream but are not absorbed into the alkali liquor, so the desulfurization effect is not obvious

[0010] The disadvantage of this method is that the heavy fraction used as the back extraction solvent contains surface active substances and is easy to form colloidal heteroatom ring compounds such as phenol, thiophenol, aniline, etc., and the emulsification is serious when it is separated from the regenerated lye by sedimentation. In this way, the heavy fraction after back-extraction carries more lye, and the regenerated lye after back-extraction carries more heavy fraction. After the extraction, the demercaptan rate and desulfurization rate decrease. On the other hand, the coalescence efficiency decreases when the back-extracted heavy fraction flows into the subsequent coalescer for treatment, and the service life of the coalescer is shortened, which affects the selectivity. Hydrogen catalysts are less active due to more base deposition

In particular, the desulfurization activity of the selective hydrogenation catalyst used in the method is not very high, and it is difficult to obtain a product with a sulfur content not greater than 50 μg / g

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