Desulfurization of light gasoline in gasoline hydrogenation units

Yes, after passing through the SHU reactor, light sulfur is mainly present in light gasoline, while heavy sulfur is primarily found in the heavy gasoline fractions. Through pre-fractionation, light gasoline and heavy gasoline can be separated, and the light sulfur components in the light gasoline become more stable, thereby reducing the sulfur content of the light gasoline. At the same time, pre-fractionation can also improve the processing efficiency of gasoline hydrogenation units, resulting in higher purity of the gasoline. .

In the SHU reaction, heavy hydrocarbons (including octane, nonane, etc.) are dehydrogenated, desulfurized, and denitrified, producing more olefins and aromatic compounds. Light hydrocarbons (such as butane, isobutane, etc.) do not readily undergo the aforementioned reaction; therefore, they are relatively abundant in the products resulting from the reaction. At the same time, in the SHU reaction, heavier sulfur and nitrogen compounds are typically converted into lighter forms such as sulfide and ammonia; these sulfide and ammonia substances are adsorbed in the catalyst bed where they undergo further conversion. As a result, the gasoline that comes out of the reactor may still contain substances such as hydrogen sulfide and ammonia. Therefore, when further processing the gasoline produced by the SHU reactor through pre-fracturing, separation and treatment can be carried out based on the characteristics and contents of different substances. Generally speaking, these substances can be effectively separated and removed, thereby keeping the sulfur content in gasoline at a low level while also improving the quality of gasoline.

The crude oil undergoes selective hydrogenation (SHU) to saturate dienes and convert light sulfur compounds into heavy sulfides, a process that reduces the sulfur content in light oils.

In the SHU reactor, the main processes are: 1) the selective hydrogenation of dienes to form monoenes, and 2) a sulfur transfer reaction in which sulfur from the light fractions is transferred to the medium fractions, while the olefins remain mainly in the light fractions or the medium fractions. After pre-fracturing, the heavier components are hydrodesulfurized, thereby ensuring that the loss of octane number is minimized

The SHU reactor is known as selective hydrodesulfurization; its purpose is to focus on the hydrogenation of dienes, with little or no hydrogenation of olefins occurring. This approach helps to remove substances that tend to cause coking during HDS reactions, while also contributing to the maintenance of octane rating. Additionally, during this process, sulfur is transferred to heavier components, resulting in only small amounts of light sulfides in the light gasoline, thus keeping its sulfur content low. Typically, about 20%-30% of the light gasoline is separated out in this way. However, due to the difficulty in removing thiophene sulfur, the cutting ratio varies significantly.

1. Light thiol compounds are converted into heavier sulfides: RSH + R’ (C5 to C7 alkenes) → RS R’.
2. Light thiol compounds are converted into heavier thiols: Step 1: RSH + H2 → RH + H2S; Step 2: H2S + R’ (C5 to C7 alkenes) → R’SH.
3. Light thioethers are converted into heavier thiols: Step 1: CH3–S–CH3 + H2 → CH4 + H2S; C2H5–S–CH3 + H2 → C2H6 + H2S; Step 2: H2S + R’ (C5 to C7 alkenes) → R’SH. In SHU reactors, the main processes are 1) the selective hydrogenation of dienes to form monoenes, and 2) sulfur transfer reactions, where sulfur from the light components is transferred to the medium-weight components, while the alkenes remain primarily in the light or medium-weight components