【Daily Question 2019】Hydrogen production and hydrogenation section – Question No. 037

It can be divided into wet vulcanization and dry vulcanization

Using the appropriate straight-run oil as a raw material to carry the vulcanizing agent, and carrying out vulcanization through a slow reaction via liquid-phase circulation, is defined as wet vulcanization； Using cyclic hydrogen as the medium to carry the sulfiding agent, and carrying out the sulfidation reaction through gas-phase circulation is known as dry sulfidation.

Divided into wet vulcanization and dry vulcanization

It can be divided into wet vulcanization and dry vulcanization.

The in-vessel pre-vulcanization method can be further divided into wet vulcanization and dry vulcanization. Wet sulfiding is also known as liquid-phase sulfiding. The process involves first dissolving the liquid sulfiding agent in light distillate oil to form a sulfided oil, which is then fed into a reactor where it comes into contact with a hydrogenation catalyst to undergo the sulfidation reaction. Due to the favorable conditions for mass and heat transfer in the liquid phase, the sulfidation process is easy to control. However, the catalyst must be dried before liquid-phase sulfidation to remove moisture; otherwise, when the wet catalyst is heated together with the feed, it is prone to damage and the bed pressure will increase. Furthermore, since distillate oils tend to decompose during the reaction, producing a large amount of unsaturated hydrocarbons, the sulfidation time is long and catalyst carbon deposition is extensive. Furthermore, catalysts with high metal contents are often difficult to sulfide, which affects their activity and stability. Furthermore, liquid vulcanizing agents have a low auto-ignition point, strong corrosivity, and high toxicity, making their storage and transportation difficult. Catalysts supported on amorphous silicon aluminum should be sulfided in a liquid phase. Dry vulcanization does not require the preparation of vulcanization oil; instead, the vulcanizing agent is mixed with hydrogen and fed together into the catalyst bed. This not only reduces the loss of the vulcanizing agent and prevents metal corrosion on the inner surfaces of the pipes and fittings upstream of the reactor, but also enables the vulcanization process to be completed more quickly and in a more uniform manner. However, without mineral oil as a heat carrier, the large amount of heat generated during the sulfidation process can cause the temperature inside the reactor to rise too high, making it difficult to control the reaction. To achieve the optimal sulfidation of the hydrogenation catalyst, it is necessary to strictly control the reaction conditions at each stage of sulfidation. Catalysts containing molecular sieves are usually pre-sulfurized in a gas phase. The theoretical pre-vulcanization time inside the reactor is generally 6 or 3, but the actual vulcanization time is often longer. Although these methods differ from each other, they all share one common feature: it is necessary to first prepare a gaseous or liquid vulcanizing agent, which is then injected into the hydrogenation reactor. As a result, more equipment is required, such as vulcanizing agent tanks, vulcanization reactors, injection pumps, etc.; this leads to high investment costs. Moreover, the vulcanizing agents cause significant corrosion to the equipment and pose environmental hazards.

Depending on the state of the sulfurizing agent, the pre-sulfurization method within the hydrogenation unit can be divided into wet sulfurization and dry sulfurization

It can be divided into wet vulcanization and dry vulcanization

Divided into wet vulcanization and dry vulcanization