What is the purpose of catalyst sulfurization?

Catalyst activity in the sulfided state is higher than that in the oxidized state. The process of converting the catalyst from the oxidized state to the sulfided state is usually called presulfidation. The sulfurization process should generally be carried out before the catalyst is put into normal use. Untreated catalysts are all in an oxidized state. In order for the catalyst to obtain higher activity, the catalyst must be converted from the oxidized state to the sulfurized state, that is, pre-sulfurized. Use DMDS to pre-vulcanize it.

This is the poster I found on other forums for reference! Hydrogenation catalyst sulfurization is one of the key technologies to improve catalyst activity, activate device operation, extend the device operation cycle, and improve economic benefits. Hydrogenation catalysts are mainly composed of metal components and carriers. The metal component is loaded on the porous carrier in the form of oxidation state to promote hydrogenation and deN, hydrogenation and S, hydrogenation and dearomatization, hydrodemetallization, hydrodeoxygenation and other reactions. Only when the catalyst is pre-sulfurized to convert the metal component from the oxidized state to the sulfurized state can cat have high activity, stability and selectivity, strong resistance to toxicity and long life, and can maximize the role of the hydrogenation catalyst. Sulfidation of metal oxides Sulfidation of metal oxides is an efficient thermal reaction. The ideal sulfidation reaction is: MoO3+2H2S+H2 = MoS2+3H2O-163.3kJ/mol 9CoO+8H2S+H2 = Co9O8+9H2O 3NiO+2H2S+H2 = Ni3S2+3H2O-129.8 kJ/mol WO3+2H2S+H2 = WS2+3H2O The classification method of vulcanization technology depends on the place where the vulcanization reaction is carried out. Hydrogenation catalyst vulcanization can be divided into in-vessel vulcanization and external vulcanization. In-vessel vulcanization refers to vulcanization after cat is loaded into the hydrogenation reactor. External vulcanization means that the hydrogenated cat is combined with the vulcanizing agent before the cat is loaded into the reactor, and then loaded into the reactor. When starting the operation, only hydrogen and oil are introduced, and then the temperature is raised for vulcanization. Sulfurization method Catalyst sulfurization is generally divided into two types: wet sulfurization and dry sulfurization. Wet vulcanization is to use hydrocarbons or distillates containing sulfides to vulcanize in a liquid or semi-liquid phase in the presence of hydrogen. ； Dry vulcanization is to vulcanize directly with hydrogen sulfide containing a certain concentration or directly injecting organic sulfide into circulating hydrogen in the presence of hydrogen. Wet vulcanization is divided into two types. One is that the sulfur required for the catalyst vulcanization process is vulcanized by externally added sulfide (such as CS3 dimethyl disulfide, etc.) ； The other is to rely on the sulfur of the vulcanized oil itself for vulcanization. It is now recommended to use an external pre-sulfurized catalyst. After the external pre-sulfurized catalyst is loaded into the reactor, it is replaced by nitrogen and the air tightness is qualified. Without the need for temperature rise and drying, hydrogen replacement and temperature rise can be started directly. The start-up steps are simple and fast, and the time required for start-up is significantly shortened. Catalyst sulfurization is safe, and the start-up time of the device is shortened, which can significantly improve the economic benefits of the enterprise.

Generally, catalysts shipped from the factory are in an oxidized state. The oxidized state is a stable state and is convenient for storage and transportation. Sulfurization In order to change the active metallic center of the catalyst to a sulfurized state and thereby improve the activity of the catalyst, sulfurization is divided into wet sulfurization and dry sulfurization. Depending on the properties of the catalyst, the catalyst manufacturer will put forward requirements for sulfurization and formulate corresponding sulfurization plans according to the requirements.

The oxidized catalyst needs to be presulfided before feeding to restore the activity of the catalyst.