In-catalyst dry sulfidation is carried out in a high-pressure circulation loop composed of heating, reaction, heat exchange, cooling, high-pressure separation, circulating hydrogen compressor and logistics pipeline of hydrocracking. The procedure includes: using the circulating hydrogen heated by the heating furnace, heating the catalyst according to the maximum circulating hydrogen flow rate and the required heating rate, and injecting the vulcanizing agent (DMDS) into the inlet of the reaction heating furnace according to the strictly controlled flow rate, using The sulfurizing agent is decomposed in the presence of hydrogen to generate the H2S sulfurizing catalyst. When the catalyst is presulfurized, the following two main reactions take place in the reactor:
(1) The vulcanizing agent (DMDS) first reacts with hydrogen to generate hydrogen sulfide and methane, which is an exothermic reaction. The reaction generally occurs at the inlet of the refining reactor R101, and the reaction speed is relatively fast.
(2) The catalyst active components in the oxidized state (nickel oxide, molybdenum oxide, etc.) react with hydrogen sulfide to become the catalyst active components in the sulfurized state. This reaction is an exothermic reaction and occurs on each catalyst bed in the reactor. . The temperature rise phenomenon that occurs during pre-vulcanization is caused by this reaction.
(3) According to the above chemical reaction equation and the content of active metal components in the catalyst, the theoretical amount of vulcanizing agent and the theoretical amount of generated water can be calculated for the unit catalyst to be completely vulcanized.
There may also be undesired side reactions during the sulfidation process: the active components of the catalyst in the oxidized state (nickel oxide, molybdenum oxide, tungsten oxide) are reduced by hydrogen to form metal elements and water, which will greatly damage the activity of the catalyst. This reaction is extremely dangerous and should be avoided as much as possible. This side reaction is more likely to occur at higher temperatures (greater than 230°C) in the presence of hydrogen and without hydrogen sulfide.
The vulcanization process mainly goes through two constant temperature stages at 230°C and 370°C. The degree of completion of vulcanization is generally based on the addition of vulcanizing agent in the whole process reaching 120% of the theoretical sulfur content of the catalyst calculated by metal. The constant temperature can be determined by measuring the hydrogen sulfide concentration at the outlet of the reactor. Before the constant temperature of 230°C, the hydrogen sulfide must be required to completely penetrate the catalyst bed (marked by the beginning of a large amount of hydrogen sulfide in the circulating hydrogen). The final temperature of vulcanization is generally 360℃-370℃. In fact, at each temperature, there is an equilibrium limit value. Even if the vulcanization time is prolonged, the sulfur content will not increase. When the temperature reaches above 300 °C, the vulcanization reaction speed is very fast, and the vulcanization can be completed.