What are the uses of catalytic slurry?

Deep Processing Products of Catalytic Cracking Slurry and Their Applications Abstract: This paper introduces the comprehensive utilization of catalytic cracking slurry in China and explores the applications of the products derived from this slurry. Keywords: slurry, deep processing, product applications; Introduction: Catalytic cracking is one of the most important processing methods for converting heavy oils into lighter ones today. To meet the growing demand for light fuel oil and the increasing heaviness of crude oil, as well as to raise the slag blending ratio in the feedstock, some FCC units process atmospheric residue directly, while other FCC units have begun to incorporate vacuum residue into their processing. Heavier feed materials have many adverse effects on FCC units, particularly coking and scaling, which prevent the units from operating properly. To prevent coking and scaling in the equipment as well as to maintain its thermal balance, many refineries employ this method of slurry discharge to address this issue. As the feedstock becomes increasingly heavy, the production of oil slurry will increase further. Therefore, its effective utilization is receiving increasing attention. Currently, domestic catalytic slurry is generally shipped as an inexpensive heavy fuel oil. To obtain high-value-added products from catalytic slurry, numerous research efforts have been carried out to determine that the slurry can be extracted and further processed. Since the oil slurry contains 30% to 50% saturated hydrocarbons, and these saturated hydrocarbons are high-quality feedstocks for catalytic cracking ； At the same time, aromatics account for over 50% of the oil slurry; aromatics are highly valuable chemical products with a wide range of applications and promising market prospects. Therefore, it is a great shame to burn catalytic slurry as an inexpensive heavy fuel oil; exploiting it can bring significant economic benefits to refineries. Process technology: China started research on the utilization of oil slurry relatively late. Although significant progress has been made through experiments and studies in recent years, it is still in its initial stage, and more investment in scientific and technological efforts is needed. Since the catalytic cracking slurry contains about 35% saturated hydrocarbons, about 50% aromatics, and gums asphaltenes, the properties of the slurry from FCC units in different refineries are shown in Table 1. After years of research and experimentation, it has been shown that the solvent extraction process can be used to achieve a preliminary separation of the oil slurry. The wax oil obtained as a result is an excellent raw material for catalytic cracking, while the oil extracted through this process contains a high proportion of aromatics (around 90%). Through further processing and refinement, high-value aromatics can be produced, thereby enabling full utilization of the oil slurry. Table 1: Main components of FCC slurry, composition in wt% – Daqing Refining & Chemical Company, Shijiazhuang Refinery, Shengli Refinery, Jiujiang Refinery. Saturated hydrocarbons: 36.5, 28.3, 33.68, 38.5; Aromatic hydrocarbons: 60.1, 34.2, 52.48, 53.6; Resins and asphalts: 3.4, 37.5, 13.94, 7.9. Density, g/cm3: 1.0082, 1.013, 1.0046, 1.025. In terms of processing technology, the slurry extraction process for this type of oil slurry is already fairly mature. At present, the Luoyang Petrochemical Research Institute has achieved success in industrial production using a dual-solvent system (with furfural as the main solvent). Shandong Guangrao Petrochemical Group Co., Ltd., in collaboration with China University of Petroleum (Beijing), achieved excellent results by using the N-methyl-2-pyrrolidone mixed extraction process; the products launched on the market generated significant economic benefits. Features of the slurry extraction process: A dual-solvent extraction process is employed. To prevent the water carried by the second solvent from affecting the extraction efficiency, two solvent separation tanks were used to further separate the solvents. Purification of heavy mixed aromatics: After extraction from the slurry, oil is distilled out, resulting in heavy mixed aromatics, which have limited applications, poor quality, and low added value. Generally used as a softener in the rubber industry, due to its poor quality, it can be further processed through extraction and refining techniques to be separated into several products. This not only increases the variety of products and improves their quality as well as broadening their applications, but it also enhances the economic benefits for enterprises. The separation process of mixed aromatics is relatively simple; by means of vacuum separation and product purification techniques, the heavier mixed aromatics can be further separated to yield products in different fractions. The main products obtained after the deep processing of oil slurry are as follows: (1) Refined oil – high-quality wax oil. ⑵Aromatic 1# — Aromatic oil at <500°C (light aromatic). ⑶Aromatic hydrocarbons 2# – Aromatic oil at 500–545°C (heavy aromatic hydrocarbons). ⑷Aromatic asphalt. ⑸Heavy aromatics – rubber additives (refined heavy aromatics or extracted mixed aromatics), mainly used as softeners and rubber filling oils. ⑹Heat transfer oil, etc. Product Applications and Market: The products obtained after slurry separation have a wide range of uses. Aromatics are highly valuable chemical products that can be further processed to produce items with higher added value. At the same time, aromatic hydrocarbons are used as plasticizers for polyvinyl chloride, heat transfer oils, and rubber softeners; they are inexpensive and of high quality, and demand for them will continue to grow, offering very promising prospects for market application. The various product applications and market conditions are as follows: High-quality wax oil. This type of oil has superior quality compared to vacuum wax oil; it contains a high level of wax, very low levels of heavy metals, a low coking rate (around 3%), and a low dry gas yield. It also produces almost no sludge, making it an ideal raw material for catalytic cracking. Uses of Aromatic Hydrocarbon 1# and Aromatic Hydrocarbon 2#: As plasticizers for polyvinyl chloride (PVC). Aromatic Hydrocarbon 1# and Aromatic Hydrocarbon 2# can be used as plasticizers for PVC, either alone or in combination. PVC is one of the five major general-purpose resins, and its plasticizers have a wide market in China. At present, the main plasticizers for PVC used outside China are ester compounds (dioctyl phthalate DOP and dibutyl phthalate BOP). These products require expensive raw materials, involve complex production processes, and result in high costs; their current selling price ranges from 6,000 to 8,000 yuan per ton. China’s total production capacity for PVC resin is approximately 1.5 Mt/year. The actual production volume is nearly 1.2 Mt/year, while China’s annual demand for plasticizers is around 500 kt. Aromatic hydrocarbon 1# and aromatic hydrocarbon 2# are used as plasticizers. As early as 1987, experiments were conducted by the Beijing Plastic Industry School, and it was clearly stated in the summary of the \"Experiments on Formulations Using Petroleum Aromatic Plasticizers\" that: \"Petroleum aromatics have good processability, but their plasticizing efficiency is low; their performance at low temperatures and their susceptibility to heat loss are poor, which makes them unsuitable as primary plasticizers for PVC. However, they can be used as auxiliary plasticizers, replacing up to one-third of the primary plasticizer.\" Given its low price and use as an auxiliary plasticizer in PVC, it has very broad market prospects. As a heat transfer oil, it is an important heat carrier in petrochemical production. At present, the similar products in China are mainly the YD series of heat transfer oil products produced by Beijing Yanshan Petrochemical Company (YD-300, YD-340). The main components are: **aromatic hydrocarbon compounds such as naphthalene, methylnaphthalene, and dimethylbenzene, that is, aromatics with 3–4 rings. The actual flash point of YD-type heat transfer oil ranges from 110 to 140°C, and its raw material comes from medium-weight aromatics in catalytic diesel. Aromatic 1# and Aromatic 2# produced in this project can be used as two grades of heat transfer oil products. The flash point is between 200 and 280°C, and its performance is **superior to that of similar products in China. Aromatic asphalt – By mixing aromatic asphalt with the existing asphalt in China (which meets certain quality standards), high-grade road petroleum asphalt can be produced, which possesses excellent overall properties and is an essential material for building highways. At present, there are many highways in China that need to be built, resulting in an urgent demand for asphalt for high-grade roads. However, China is constrained by the properties of crude oil; in particular, the new product quality standards set explicit requirements for wax content (<2%, <3%), which makes it practically impossible for Chinese refineries to produce high-grade road petroleum asphalt. To alleviate the supply-demand imbalance, in 1999 Sinopec decided to import specific crude oils, which would then be processed by Chinese refineries to produce high-grade road petroleum asphalt. But the problem is: (1) Classifying imported foreign petroleum products as specific foreign crude oils means that it is not possible to produce enough of such materials domestically ； ⑵This specific type of imported crude oil is not an excellent raw material for producing other petroleum products; after processing in refineries, its yield and product quality are inferior to those of domestic crude oil, as well as to those of other imported crude oils that do exist. To this end, a new process can be utilized, involving the blending of aromatic asphalt with domestically produced semi-oxidized asphalt, to produce \"high-grade road petroleum asphalt\". This process takes advantage of the high pitch content in aromatic bitumen to produce petroleum bitumen of high grade, filling a gap in China. Rubber softeners: At present, China’s total rubber production exceeds 850 kt/year (including 400 kt/year of synthetic rubber), with imports amounting to around 250 kt/year. Approximately 150 kt/year of rubber additives are required, including processing oils and filling oils. Among the raw materials used in the rubber industry, the consumption of softeners is second only to raw rubber and carbon black. As a rubber softener, heavy aromatic hydrocarbons have been tested and found to be fully capable of replacing the 10# and 30# machine oils currently widely used in the rubber industry. Aromatic softeners possess excellent physical and mechanical properties, such as good compatibility with rubber, favorable processability, high tensile strength, and low wear. Its price will be lower than that of 10# engine oil and 30# engine oil. At present, the refineries of the Tianjin Dagang Petroleum Administration and the Shanghai Refinery are able to produce a small amount of aromatic softeners, but this is not sufficient to meet the needs of the rubber industry. It is estimated that there is still a shortage of at least 50 kt/a of aromatic softeners. At the same time, the widespread use of aromatic softeners in the rubber industry has driven efforts in China to standardize, serialize, and regulate petroleum-based softeners. It is of great significance. Other uses: The products listed here are merely introduced for now; they are still in the development stage. As new products, they can fill a gap in the Chinese market, which gives them certain significance. 　 Solvent for special building membranes. Special membranes are a new type of building material; they are made from rubber and asphalt as primary materials, which are dissolved in solvents and then applied to a backing fabric to create a waterproof material that serves as a replacement for traditional felt paper. The key raw material for this building material is a solvent, but the solvents currently in use are not ideal, as they are immiscible with rubber and asphalt; rubber softeners, on the other hand, are more suitable solvents. The brightener used in casting, aromatic hydrocarbon pitch, is a highly luminous carbon material whose carbon content can exceed 50%, which is 7 to 15 times that of natural casting coal powder. Industrial casting carried out by large enterprises such as the Process Materials Research Institute of Luoyang Tractor Factory and Shanxi Yuci Hydraulic Parts Factory, along with systematic research conducted by Tsinghua University, show that it exhibits excellent resistance to sand adhesion; the surfaces of the cast parts produced are smooth, and there are no offensive odors during the casting process, **which reduces the labor intensity required for cleaning the surface of the cast parts. The quality of the castings is excellent; it is the best anti-sand clogging material in China, reaching international advanced standards. China is a major producer of castings, with an annual output of millions of tons. Due to the lower cost of aromatic asphalt, market demand is expected to increase. High-strength carbon fibers are produced in industrial settings. Carbon fibers are important high-tech products of the 20th century; they are functional and structural materials that can be used for various purposes. Due to its high specific strength and specific modulus, as well as advantages such as heat resistance, corrosion resistance, and impact resistance, carbon fiber has a wide range of applications. It is now widely used in many fields such as aerospace, transportation, chemicals, machinery, electronics, medicine, and sports. Luoyang Institute and Taiyuan Carbon Fiber of the Chinese Academy of Sciences. Due to its high aromatic content, relatively uniform molecular weight and aromatic distribution, as well as moderate average aromatic number and H/C atom ratio, heavy oil is a candidate raw material for the production of intermediate-phase pitch carbon fibers, holding significant potential for further development. It is recommended that since the deep processing of oil sludge in China is still in its infancy, only a few plants exist in the country, with a processing capacity of less than 100 kt/a. China National Petroleum Corporation’s Linyuan Refinery plans to put into operation an oil sludge extraction unit with a capacity of 50 kt/a by 2002. China’s catalytic cracking units produce around 3 Mt of slurry per year, which remains largely untapped; thus, there is great potential for its utilization. In terms of production processes, more investment in technology is needed; currently, China conducts industrial production only in the areas of slurry extraction and refining. In the future, further development of aromatic compounds after separation should be pursued to produce products such as casting brighteners and carbon fibers with higher added value. And achieve industrial production as soon as possible to fill the gap in China at an early date. In the production of carbon fibers, if it is possible to further reduce the content of solid impurities and heteroatoms during the preparation of heavy aromatic oils and before the modification of asphalt, it will be possible to significantly improve the performance of asphalt-based carbon fibers. Furthermore, exploring appropriate methods for modifying such residual oils, as well as processes for melt spinning and post-treatment, holds great potential for enhancing the performance of the final products.

Oil slurry, used directly as fuel oil, can easily clog the nozzles. Nozzle coking is also very severe. 1. In the past, some plants imported slurry dewatering systems from abroad to remove the catalyst from the oil slurry and recycle it back to the reactor; this process was rather complicated, the containers tended to get clogged easily, and the high pressure drop made operation difficult. 2. The oil slurry is further separated (at Luoyang Refinery) into light oil slurry and heavy oil slurry; the light oil slurry is sent for reactive reprocessing (with much less coke formation compared to direct reprocessing), while the heavy oil slurry is used as a raw material for solvent deasphalting to produce fuel oil, as well as as a raw material for blending asphalt. 3. As a feedstock for delayed coking, it is used to produce needle coke, which serves as fuel for steel mills. 4. Aromatic extraction: The details of this process are not very clear, but it is certainly feasible.

For carbon fiber, we previously discussed this with the Shanxi Institute of Coal Chemistry under the Chinese Academy of Sciences; however, its composition and purity are of crucial importance.