Pre-sulfurization of the catalyst

2.3 Catalyst presulfurization: The catalyst is presulfurized inside the reactor. The reaction system passed the airtightness test at 8.0 MPa hydrogen pressure; after establishing the hydrogen circulation, catalyst sulfidation was carried out. The sulfidation conditions are shown in the table below: System pressure, Mpa: 6.0; Space velocity, h-1: 1.5; Hydrogen-to-oil volume ratio: 500. For the first constant-temperature sulfidation stage, bed temperature and time: 230°C for 6 hours. For the second constant-temperature sulfidation stage, bed temperature and time: 290°C for 6 hours. For the third constant-temperature sulfidation stage, bed temperature and time: 320°C for 4 hours. Sulfidation oil: Straight-run kerosene. Sulfidizing agent: Carbon disulfide or dimethyl disulfide. Theoretical sulfur requirement, m% (per catalyst): approximately 9.5. Actual amount of carbon disulfide or dimethyl disulfide required, m% (per catalyst): 15–18. Parameters for the sulfidated oil: Density (20°C), g/cm-3: ≤0.84; Total sulfur/μg.g-1: ≤600; Total nitrogen/μg.g-1: ≤100; Colority: ≥19.0; Flash point/°C: ≥40; Dynamic viscosity at 40°C, mm2/s: 1.0–2.0; Copper sheet corrosion (100°C, 3 hours), grade: ≤1; Boiling range/°C at 10% cut: ≤205; Dry point: ≤300. The temperature rise process during catalyst sulfidation is shown in the table below (using carbon disulfide): Temperature at reactor inlet, °C; Rate of temperature increase/decrease, °C/h; Time for maintaining a constant temperature; Maximum allowable rate of temperature increase per °C for the bed; H2S content in circulating hydrogen, v%. From normal temperature to 175°C: 10–15 °C/h; start adding the sulfidizing agent at 200 kg/h. At 175°C: 3 hours. From 175°C to 195°C: 5–10 °C/h; 3 hours at 195°C. From 195°C to 230°C: 5–10 °C/h; actual time: 6 hours. At 230°C: 20 minutes; H2S content: 0.3–0.8%. From 230°C to 290°C: 5–10 °C/h; actual time: 6 hours. At 290°C: 20 minutes; H2S content: 1.0–2.0%. From 290°C to 320°C: 5–10 °C/h; 3 hours. At 320°C: 40 minutes; H2S content: 1.0–2.0%. Overall sulfidation process: 40 minutes. Sulfidation steps: (1) Raise the temperature at the reactor inlet at a rate of 10–15 °C/h until it reaches 175°C, then maintain that temperature. (2) Increase the pressure in the reaction system to 6.0 Mpa at a rate of 2.0 Mpa/h while maintaining a constant pressure, with full circulation of hydrogen. (3) Once each system has stabilized, start the carbon disulfide or dimethyldisulfide pump to begin injecting carbon disulfide or dimethyldisulfide, with the initial injection rate controlled at 200 kg/h, while simultaneously monitoring the level of the sulfiding agent. (4) Analyze the hydrogen sulfide content in the recycled hydrogen every half hour, and analyze its composition every four hours, recording the amount of water generated. (5) After the temperature wave passes through the reaction bed, the temperature is maintained at 175°C; then it is increased at a rate of 7°C/h to 230°C, where it remains constant for 6 hours. (6) After the constant temperature at 230°C is reached, the temperature is increased at a rate of 5°C/h to 290°C, where it remains constant for 6 hours. Then heat at 6°C/h to 320°C, and maintain the temperature for 4 hours. Sample the recycled hydrogen gas once per hour to determine the H2S content. (7) Water is generated during the pre-vulcanization process; after vulcanization begins, the amount of water is measured, and drainage is carried out at regular intervals with proper recording. Before each drainage, a sample is taken to analyze the hydrogen sulfide content in the generated water. (8) During the sulfidation process, in principle, carbon disulfide or dimethyldisulfide should be injected and the temperature raised according to the pre-calculated amounts. If any of the following phenomena occur, adjust the operation as follows: a. After injecting carbon disulfide or dimethyldisulfide, the catalyst in the reactor will absorb sulfides, resulting in a temperature wave; do not raise the temperature until this temperature wave has passed through the entire reactor. b. During the heating phase, stop increasing the temperature once the temperature of any reactor bed rises by more than 20°C; if necessary, reduce the amount of carbon disulfide or dimethyldisulfide injected accordingly until injection is halted. c. Until the H2S content in the recycled hydrogen is detected or its concentration is less than 0.3 (V/V)%, the bed temperature inside the reactor must not exceed 230°C. d. When the bed temperature in the reactor is below 230°C, the H2S content in the recycle hydrogen should be maintained at 0.1–0.5 (V/V)%; between 230°C and 320°C, it should be kept at 0.5–1.0 (V/V)%. Before the end of the constant-temperature phase at 320°C, the H2S content in the recycle hydrogen should be greater than 1.0 (V/V%); this value is used to control the amount of carbon disulfide or dimethyl disulfide injected. e. Sulfurization increases significantly above 200°C; the heating rate must be slow. (9) During the constant-temperature phase at 320°C, the maximum temperature of the catalyst bed shall not exceed 370°C; if a temperature spike occurs, it is permissible to inject cold hydrogen. If the maximum temperature of the catalyst bed exceeds 380°C, the reactor inlet temperature shall be reduced until the heater is turned off. (10) After the temperature reaches 320°C, it is maintained at this level for 4 hours. During this time, the H2S content in the circulating hydrogen is kept between 1.0 and 2.0 (V/V)%. If the hydrogen sulfide concentration in the circulating hydrogen remains unchanged after two consecutive measurements, and if the level of the liquid phase no longer rises along with the formation of water, then the sulfidation process is complete. (11) After sulfidation is complete, the temperature is reduced to 260°C at the reactor inlet and maintained constant; the injection rate of CS2 is decreased or stopped, keeping the H2S content in the recycled hydrogen at 0.05–0.1 (V/V)%. Raise the pressure to the reaction pressure in preparation for feeding the feed oil.

There are wet and dry methods； The vulcanizing agents used include DMDS, CS2, etc ；

It is generally divided into dry vulcanization and wet vulcanization. The vulcanization conditions are primarily determined by the requirements of the catalyst; wet vulcanization is used as it makes it easier to control the process

Is there any summary on vulcanization, such as the sulfuring rate?···

⒈Fill the hydrogen system of the hydrogenation unit with hydrogen, establish a cyclic heating process, and introduce appropriate auxiliary oils； ⒉When the temperature reaches a certain level, the hydrogen-handling system begins to inject sulfiding agents such as DMDS and CS2 ； ⒊Pay attention to the bed temperature rise; different devices have different requirements ； ⒋Continuously monitor changes in hydrogen sulfide levels in the system at different stages, and adjust the sulfur injection volume accordingly ； ⒌When the hydrogen sulfide level in the system reaches a certain value, sulfur injection is stopped.

Hydrocracking catalysts are generally sulfided by the dry method, while residue hydrogenation is usually carried out using the wet method