Regarding MTBE catalyst leaching and soaking

This is our setup, which includes the reactor, reaction tower, and the alcohol washing procedure for the catalyst. (1) Since the catalyst contains about 50% water, it has a strong affinity for water. If this moisture is not removed and the C4 component is introduced directly, the bed will experience a very high level of resistance, which can damage the equipment. Therefore, the water in the catalyst must be removed. The dehydration method in the catalyst is the (methanol substitution method). The current setup operates with three reactors in series; these reactors can be used for dehydration separately or for continuous sequential dehydration. (2) Reactors: The volume of each of the three reactors is 36 m3. The volumetric flow rate of the methanol feed pump is Q=7 m3/h; therefore, it takes about 5–6 hours to start the methanol feed pump and feed methanol into Section 1 of the reactor until this section is filled with methanol. The outlet valve at the bottom of Section 1 is then closed, and the vent valve at the top of the section is monitored – once methanol begins to flow from this vent valve, it indicates that Section 1 is fully filled with methanol, at which point the vent valve is closed as well. Start a circulation pump to circulate methanol in the external circulation system for about 4-8 hours. The aqueous methanol, which has had the catalyst in stage 1 of the reactor dehydrated, is discharged into stage 2 of the reactor; the circulation pump for stage 2 is started to circulate the methanol within the external circulation system of stage 2, with this circulation lasting approximately 4–8 hours. The aqueous methanol, which has had the catalyst in section two of the reactor dehydrated, is sent to section three of the reactor. The circulation pump for section three is started, allowing the methanol to circulate within the external circulation system of that section; this circulation lasts for about 4–8 hours, during which the water contained in the catalyst of section three is removed. During the two-stage cyclic dehydration in reactor stage 2, fresh methanol can be injected into reactor stage 1 for a second dehydration process. Then, methanol from the second dehydration stage of Reactor 1 is used to carry out secondary dehydration in Reactor 2 and Reactor 3 in sequence. (3) During the methanol feeding process into the etherification reactor, nitrogen can be vented from the system by opening the (safety valve bypass valve). Do not open the nitrogen discharge valve too wide, to prevent the catalyst from being carried into the flare system and resulting in catalyst loss. (4) The etherification reactor is dehydrated through a second alcohol wash, and the methanol concentration in the methanol-water solution is analyzed; it is considered satisfactory when the methanol content is 80% or higher. (5) Dehydration of the catalyst in the reaction tower. The catalyst dehydration method in the reaction tower is different from the method mentioned above. First, the catalyst here cannot be soaked in methanol; second, the catalyst here cannot be circulated with methanol either. Only leaching can be used to remove moisture from the catalyst. Start the methanol feed pump, and open the manual valve of the methanol pipeline leading to the upper section of the reactor tower for catalyst drying. The washing rate is 10 m3/h, with a washing time of approximately 8 hours. Analyze the concentration of methanol in the methanol-water solution; a concentration of 80% or higher is considered acceptable. (6) The total volume of all these aqueous methanol solutions is approximately 150 m3. During the alcohol washing of the catalyst, the methanol recovery tower is in a material waiting cycle. If the methanol recovery tower is not adjusted properly and the waste methanol resulting from catalyst dehydration in the etherification reactor cannot be processed, it can be temporarily stored in the 50 m3 capacity carbon tetrafluoride buffer tank after etherification. The waste methanol from catalyst dehydration in the reaction tower can be temporarily stored inside the upper section of the reaction tower until all the water-containing methanol has been recovered. The methanol recovered by the methanol recovery unit is returned to the methanol feed tank through pipes. Note: This process must be carried out during the first startup; otherwise, it is not necessary.

Natural dehydration: After the catalyst is installed, it is subjected to natural dehydration for 12 hours (from the bottom of the tower to the drain). Methanol spraying: Change the feeding method for both reactors to top feeding, start the methanol pump P302, and adjust the amount of methanol sprayed according to the temperature rise (keeping the bed temperature below 50°C). If the temperature rises rapidly, pause the methanol pump temporarily until no significant further temperature increase is observed in the bed. Cyclic soaking: After no significant temperature rise in the bed layer is observed, increase the spraying rate. Fill both vessels (before filling them, allow air to escape from the bottom of the vessels for dehydration; stop this process once methanol appears), and then restore normal operation of the inlet and outlet ports at the top and bottom. Redirect the outlet of R302 to the waste methanol tank V304B, and contact the laboratory for testing promptly. Once the methanol concentration exceeds 80%, stop feeding methanol into V304B and instead direct it to the start/stop tank V303, where it will circulate before being sent to mixer X301 via P304. Samples are taken for testing at any time during the circulation process, and P302 is used to add new methanol as appropriate based on the concentration levels. Removal of methanol: Dehydration is completed after 24 hours of cycling (samples are taken for testing at various points during the cycling process to ensure that the methanol concentration is above 90% by the end of the cycle). Methanol under nitrogen pressure is pushed from the top of the two vessels into V304B; the methanol in V303 is then sent to V304B via P304.

Soak in methanol for 24 hours, then remove the pressure under its own weight; after pressure equilibrium is achieved, purge with nitrogen. After that, replace the contents once with the material after the reaction and once with fresh C4 material, after which it is ready for use