Knowledge on the coking of non-hydrogen catalysts?

Catalyst regeneration and coking conditions for non-hydrogenated gasoline upgrading units: Pressure less than 0.8 MPa, temperature less than 450°C. After operating for a certain period of time, the catalyst in the reactor loses its activity; its activity can be restored by employing an in-reactor coking regeneration method, depending on its performance status. Stop feeding the material and cool down the reactor. When the temperature inside the reactor drops to 250°C, use a blind flange to completely seal off the pipeline from the raw oil inlet up to the heat exchanger. Then remove the blind flange that connects the reactor to the regeneration system; at this point, the reactor is connected to the regeneration system. The process for catalyst regeneration is the same as that used during drying ； The reaction vessel was purged with nitrogen. It is necessary to ensure that the system has been properly purged with nitrogen and contains no crude oil ； Heating by furnace ； It is carried out in accordance with the catalyst regeneration coking conditions. During the coking process, air is supplied as needed to the compressor and to the second and third bed layers of the reactor, and its flow rate is adjusted to prevent excessive or rapid temperature rise (the maximum temperature should not exceed 450°C) ； At the same time, the system pressure and the O2 concentration in the circulating gas are regulated by adjusting the control valve on the top of the buffer tank ； Based on the temperature rise in the reactor bed, gradually increase the coking temperature and the amount of air supplied ； Ensure that the bed temperature rises by 50–60°C, with the highest temperature inside the device remaining below 450°C℃ ； If the sulfur content in the catalyst carbon deposit is high, it is necessary to add alkali solution to the vapor-liquid separation tank through a temporary pipeline in order to reduce the sulfide content in the recycled gas ； When a large amount of air is introduced and the charring temperature reaches 450°C, with no significant temperature rise in the bed layer, after maintaining this temperature for four hours, the supply of air is stopped and N2 is used to displace the air in the reactor until the oxygen content drops below 0.5%, at which point the charring process is complete. Remove the relevant blind flanges, close the inlet and outlet valves of the reactor, open the bypass valve, and put the reactor on standby.

Research location: Shenyang Paraffinization Plant. I. Main description: The non-hydrogenation reforming process for straight-run gasoline involves bringing straight-run gasoline and heavy n-paraffins into contact with a catalyst in a fixed-bed reactor (under reaction conditions of 330°C–440°C, pressure of 0.2–0.4 Mpa, and a reaction space velocity of 0.3–0.5 h-1). A series of catalytic reactions such as selective cracking, isomerization, oligomerization, dehydrogenation, and aromatization occur as a result, thereby altering the properties of the straight-run gasoline and producing high-octane gasoline. As a by-product, some light liquefied gas, along with a small amount of dry gas and hydrogen, is generated; the yield of high-octane gasoline can reach around 75%. The non-hydrogenation reforming process for straight-run gasoline at this plant utilizes patented technology from the Petroleum Processing Research Institute; preliminary preparations began in June 2003, and the facility was completed and put into operation successfully in November 2003. It is reported that the research on this process is based on paraffin-based crude oil. Since the factory has access to Daqing crude oil, the technology developed by the Petroleum Chemical Science Research Institute is well-suited for this factory. As for crude oils of other types, further discussions with the Petroleum Science Research Institute are needed before any conclusions can be drawn. II. The process flow for the hydrocarbon-free reforming of straight-run gasoline is as follows: III. Design capacity and utility requirements: The utility conditions required for this facility are as follows: Fresh water: 0.4–0.5 MPa; Steam: 1.1 MPa; Deoxygenated water: 50–60°C; Instrument air: 0.4–0.6 MPa. This process is simple, and the area required is approximately 60*25 meters. Since the Shenyang Waxing Plant was built by modifying the framework of an existing solvent deasphalting unit, it has a processing capacity of 70,000 tons per year, with 42,000 tons per year processed as straight-run gasoline and 28,000 tons per year as heavy naphtha. The plant feeds 60% straight-run gasoline and 40% heavy naphtha into the reactor, with the main goal of reducing the olefin content in the gasoline. The octane rating of the resulting gasoline can reach 87 (RON), and this gasoline can be blended with catalytically cracked gasoline to produce qualified 90# or 93# gasoline. IV. Properties of the raw materials used: Properties of straight-run gasoline – Key parameters: Heavy paraffins content: Initial boiling point, °C: ≥36; C3 content: 0.66; Final boiling point, °C: ≤170; C3 content: 0.07; RON: >50; C4–C1 content: 0.10; Density (at 25°C): 0.7–0.73 g/cm3; IC4 content: 0.08; Sulfur content: 98; Total butenes content: >60.

V. Energy consumption details: Water, t per ton of raw material; Electricity, kwh per ton of raw material; Gasoline, t per ton of raw material; Fuel, t per ton of raw material. Total energy consumption: 104 kcal per ton of raw material – 16.2, 20.94, 0.226, 0.0113, 1.62, 6.282, 17.176, 11.3, 36.378; i.e., 104 kcal per ton of raw material.

VI. Main equipment: 1. 2 reactors; 2. 1 absorption and separation tower; 3. 2 heating furnaces; 4. 1 stabilization tower; 5. 2 air compressors; 6. 1 gas compressor; 7. 9 heat exchange units; 8. 8 pumps.

VII. Investment requirements: The total investment for this project is over 20 million yuan, covering the electrical system, DCS control system, and main equipment. This amount does not include patent fees, process package and design costs, nor catalyst acquisition costs (which are around 10 million yuan, with a total catalyst loading of 44 tons, at approximately 238,000 yuan per ton).

VIII. Analysis of gasoline and liquefied gas quality after modification: After undergoing modification reactions, the RON of straight-run gasoline increases by more than 30%, while the MON increases by more than 25%. The total sulfur and mercaptan contents decrease, resulting in an overall improvement in product quality. The modified gasoline has an olefin content of less than 5%, an aromatic content of less than 35%, and a benzene content of less than 1.5%, all of which meet the requirements for clean gasoline formulations. The remaining components are mainly high-octane naphthenes and isoparaffins, with no significant differences in other properties. Comparison of the properties of raw materials used in the reforming reaction and gasoline products. Gasoline category: Straight-run gasoline; Raw material for straight-run gasoline; Product obtained from straight-run gasoline reforming; Product obtained from straight-run gasoline reforming with the addition of C4 compounds. RON: 54.0, 86.3, 87.7; MON: 54.2, 79.1, 81.4. Boiling range/°C (initial boiling point): 36–158, 38–212, 40–203. Residue/mg•(100ml)−1: 3.0. Induction time/min: >1000, >1000, >1000. Sulfur content/%: 0.06, 0.002. Copper sheet corrosion test (50°C, 3 hours): 3c, 1b, 1b. Vapor pressure/kPa: 58, 62. Density/kg·m−3: 720, 736, 735. Composition of gasoline as determined by chromatography, ω%: Aromatics: 4.9, 25.7, 33.4; Olefins: 0, 0.5, 1.0; Cycloalkanes: 36.5, 29.7, 28.7; Normal alkanes: 38.1, 14.9, 10.7; Isomeric alkanes: 20.0, 29.2, 26.2. Total: 100.0, 100.0, 100.0. Benzene content: 0.54, 1.07, 1.23. In the reforming reaction, the yield of C5+ gasoline is approximately 75%, while the yield of dry gas (H2 + C1 + C2) is only 0.64–1.0% of the total feed volume. Therefore, the overall liquid yield from the reforming reaction is higher than 98%. The dry gas yield from direct steam reforming is very low. Product distribution of the reforming reaction: Raw material names and compositions, ω%
Pure straight-run gas reforming; Straight-run gas with butenes added for reforming; Straight-run gasoline as raw material: 100, 60
Light butenes as raw material: 0, 40
Product distribution based on the total feed, ω%: H2+C1+C2: 0.62, 1.06; C3+C4: 26.85, 22.92; C5+ gasoline: 73.98, 75.62
Total liquid yield: 99.36, 98.94
Gasoline yield based on straight-run gasoline, ω%: 73.98, 89.18
The yield of reformed gasoline increases significantly when butenes are added to the raw materials, calculated based on the amount of straight-run gasoline used as feed; this is due to the conversion of butene hydrocarbons into high-octane gasoline during the reaction. Therefore, blending C4 not only improves the octane number of gasoline products but also significantly increases the gasoline yield. When the blending amount of C4 reaches 40 m%, the yield of the modified gasoline product relative to the straight-run gasoline feed can exceed 100%. In liquefied gas, propane accounts for 50% to 60% of the volume. LPG has a light composition and low olefin content; after desulfurization, it can be used as vehicle LPG. Composition and properties of liquefied gas products: ψ% Category Components Straight steam reforming product Straight steam with C4 blending reforming product C2: 2.5 1.5 C3o: 55.8 59.0 C4o: 39.6 36.6 C4+: 2.0 2.4 C5+: 0.1 0 Economic benefits: Since the plant uses Daqing crude oil, the price difference between 93# gasoline and liquefied gas is virtually zero. Under these conditions, the economic benefit generated by this facility is approximately 6 million yuan per year.

2# bingyu252 Thank you for your selfless dedication. I’ve learned it.* It would be even better if there were factors affecting product quality and methods to address them.

3# lx_drq: The highest amount of C4 that can be blended, as indicated by the available data, is 40%. Could someone knowledgeable explain this? There is a saying that if the ratio is too high, it is difficult to control the bed temperature. Combination is a highly exothermic reaction. I agree. The question is: how significant is the impact of a high ratio on coking? How exactly does coke come into being? It seems there is no material that explains it from a fundamental perspective. Could an expert share their operational experience? This would help us gain a deeper understanding of coking.

The highest amount of C4 blended, as indicated by existing data, is 40%. Could someone knowledgeable explain this? ( @7 [& l# K7 i7 t: Q1 n3 }$ K' u5 CThere is a saying that when the ratio is too high, it’s difficult to control the bed temperature. Combination is a highly exothermic reaction. Here it’s 3:7 (naphtha:C4).