Method for efficiently removing FCC (fluid catalytic cracking) oil slurry solid impurities by porous straw-based adsorbent

Abstract

The invention discloses a method for efficiently removing solid impurities in FCC (fluid catalytic cracking) oil slurry by using a porous straw-based adsorbent. The method comprises the following steps: S1, preparing the porous straw-based adsorbent: S1-1, performing primary alkaline process pore forming; s1-2, carrying out secondary sulfonation crosslinking; and S2, solid removal of the oil slurry. Through a specific chemical modification means, the multistage pore structure of the wheat straw is preferentially regulated and controlled, and a physical adsorption carrier dominated by high specific surface area and high pore connectivity is constructed, so that high-efficiency capture and separation of fine particle impurities in the oil slurry are realized.

Description

Technical Field

[0001] This invention relates to the field of biomass-assisted desolidification technology, specifically to a method for efficiently removing solid impurities from FCC oil slurry using a porous straw-based adsorbent. Background Technology

[0002] Catalytic cracking (FCC) slurry is a high-value byproduct of petroleum refining, but the fine catalyst particles it carries can severely impact subsequent processing. Furthermore, slurry that has not undergone efficient solidification cannot meet the stringent standards for low-sulfur marine fuel oil (solids content ≤60 mg / kg), thus hindering the high-value utilization of this resource. Therefore, developing efficient and low-cost solidification technologies is a key requirement for the refining industry.

[0003] Currently, mainstream solids removal technologies all have significant limitations. In physical separation methods: centrifugation, while offering high processing capacity and ease of operation, suffers from low efficiency (typically below 30%) in removing critical fine particles smaller than 5 micrometers, and is accompanied by high energy consumption and high oil content in the solid residue (over 15%), leading to oil loss and the burden of secondary processing. Filtration separation (such as ceramic membrane filtration) can deeply purify solids to below 50 mg / kg, but the complex colloidal and asphaltic components in the oil slurry easily cause severe membrane fouling, resulting in a sharp decline in filtration flux (more than 60%) in a short period, significantly increasing equipment maintenance and membrane replacement costs. Hypergravity technology improves particle settling efficiency (approximately 40%) by enhancing the mass transfer process; however, it suffers from technical bottlenecks such as low purified oil yield (85-90%) and easy wear of internal components. Furthermore, the process often relies on chemical scale inhibitors, increasing complexity and operating costs. In chemically assisted separation methods, while additive-assisted sedimentation and its combined processes can significantly reduce ash content (e.g., from 0.390% to 0.041%), the chemical additives used often lack universality and have poor adaptability to oil slurries with different properties. More importantly, they may introduce new exogenous chemical impurities, interfering with subsequent high-value-added processing of the oil slurry. Compound solvent extraction can effectively separate oil and solids, but its core drawback lies in the enormous energy consumption of solvent recovery (which can account for more than 30% of total energy consumption), and the environmental and safety risks posed by solvent evaporation or residue. Flexible desolvation technology, while exhibiting excellent adaptability, faces significant challenges in terms of economic viability and large-scale engineering implementation due to its system complexity and high initial investment costs. These shortcomings have prompted the industry to seek better solutions.

[0004] In recent years, biomass-assisted descaling technology for the green economy has attracted attention. This technology utilizes raw materials such as straw to prepare porous carbon materials, which achieve efficient adsorption due to their high specific surface area and abundant functional groups. It has significant advantages such as being environmentally friendly, low-cost, and renewable, showing the potential to replace traditional technologies.

[0005] However, the development of this technology still faces bottlenecks due to the unclear core mechanisms. Whether the desolidification process is dominated by physical retention or chemical adsorption remains controversial. A systematic understanding of the structure-property relationship between material pore structure, surface properties, and desolidification performance is lacking, resulting in a lack of theoretical guidance for adsorbent design and process optimization. Therefore, elucidating the dominant mechanism and establishing a clear structure-property relationship have become key scientific issues that must be addressed to promote the industrial application of this technology. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a method for efficiently removing solid impurities from FCC oil slurry using a porous straw-based adsorbent.

[0007] The technical solution of this invention is: A method for efficiently removing solid impurities from FCC oil slurry using a porous straw-based adsorbent includes the following steps: S1. Preparation of porous straw-based adsorbent: S1-1, One-time alkali method for pore formation: The pretreated straw is mixed with the first mixture and reacted at 85~100℃ for 1~3h. Then the solid and liquid are separated, and the resulting solid product is washed until neutral to obtain the primary porous material. The first mixture is a mixed aqueous solution of sodium hydroxide and sodium sulfite, wherein the molar concentration of sodium hydroxide is 2~3.5 mol / L and the molar concentration of sodium sulfite is 0.5~1.2 mol / L; S1-2, Secondary sulfonation crosslinking: The primary porous material is mixed with the second mixture and reacted at 70~90℃ for 1~2h. Then, the solid and liquid are separated and the resulting solid product is washed until neutral and dried to obtain a porous straw-based adsorbent. The second mixture is an aqueous solution of sodium sulfite and sodium metaborate, wherein the concentration of sodium sulfite is 0.2~0.8 mol / L and the concentration of sodium metaborate is 0.1~0.5 mol / L; S2. Desolidification of FCC oil slurry: After diluting the FCC oil slurry, add the porous straw-based adsorbent, stir to ensure full contact with the solid particles in the FCC oil slurry, and centrifuge to obtain clear desolidified FCC oil slurry.

[0008] Furthermore, in S1-1, the straw is wheat straw.

[0009] Note: Wheat straw contains a rich cellulose skeleton, is low in cost, and is environmentally friendly.

[0010] Further, in S1-1, the pretreatment method is to wash and dry the straw and then crush it through an 80-mesh sieve.

[0011] Note: Pre-treatment of wheat straw helps prevent interference from impurities.

[0012] Furthermore, in S1-1, the mixing ratio of the straw to the first mixture is 1g:3~10mL, and deionized water is used for washing.

[0013] Note: By reasonably controlling the mixing ratio of the straw and the first mixture, the high porosity and high initial sulfonic acid loading of the primary porous material are ensured.

[0014] Further, in S1-2, the mixing ratio of the primary porous material to the second mixture is 1g:4~8mL, and the washing is performed with deionized water, and the drying temperature is 45~55℃.

[0015] Explanation: By reasonably controlling the mixing ratio of the primary porous material and the second mixture, the primary porous material is ensured to react fully. Crosslinking imparts excellent stability to it, and secondary sulfonation further optimizes its function.

[0016] Furthermore, in S2, FCC slurry dilution involves mixing it with diesel fuel, with a volume ratio of FCC slurry to diesel fuel of 1:1~2.

[0017] Explanation: By diluting, the viscosity of the FCC slurry is reduced, and its fluidity is improved, so that the adsorbent can be fully mixed and contacted with the FCC slurry, and subsequent solid-liquid separation is facilitated.

[0018] Further, in S2, the amount of the porous straw-based adsorbent added is 5-15 wt% of the mass fraction of the diluted FCC slurry.

[0019] Note: By reasonably controlling the amount of the porous straw-based adsorbent added, sufficient active surface and adsorption sites are provided to achieve the target purification depth.

[0020] Furthermore, in S2, the stirring temperature is 25~55℃, the stirring speed is 200~300rpm, and the stirring time is 1~3h.

[0021] Note: By properly adjusting the stirring parameters, we can ensure uniform mixing and improve efficiency.

[0022] Furthermore, in S2, the centrifugal separation speed is 4000~6000 rpm, and the centrifugal separation time is 10~20 min.

[0023] Note: By properly adjusting the centrifugal speed, thorough centrifugation can be ensured, and this is easy to achieve.

[0024] The beneficial effects of this invention are: (1) The present invention provides a method for efficiently removing solid impurities from FCC oil slurry using a porous straw-based adsorbent. Through specific chemical modification, the multi-level pore structure of wheat straw is preferentially controlled to construct a physical adsorption carrier dominated by high specific surface area and high pore connectivity, thereby achieving efficient capture and separation of fine particulate impurities in the oil slurry.

[0025] (2) In this invention, through two-stage chemical modification, firstly, deep sulfonation is performed in a strongly alkaline environment to create pores, deeply dissolving lignin and most of the hemicellulose. Subsequently, repair and reinforcement are carried out in a mild alkaline environment, followed by secondary sulfonation. Under hydrothermal alkaline conditions, the borate ions in sodium metaborate can undergo reversible esterification reactions with the cis-hydroxyl groups on the surface of cellulose and the hydroxyl-rich hemicellulose degradation products, forming dynamic covalent bonds of borate esters. This guides the dissolved hemicellulose fragments to rearrange in a more oriented manner, building new and more stable cross-linking bridges between or on the surface of cellulose microfibrils, forming a dynamic borate ester cross-linking network. This repairs and strengthens the hemicellulose. This process removes the cellulose skeleton that may be damaged in the first step, significantly improving the material's mechanical stability and acid and alkali resistance. At the same time, during the continuous dissociation and recombination of this network, it can guide the sulfonate groups to be distributed more evenly, preventing them from becoming excessively aggregated locally. The formed borate ester bonds may have a certain spatial shielding effect on the adjacent hydroxyl groups, which may cause the sulfonation reaction to occur in a more specific and favorable position, thereby improving the adsorption efficiency of each sulfonate group. Sulfonation and crosslinking occur almost simultaneously, and the newly introduced sulfonate groups can be immediately anchored and protected by the crosslinking network that is forming, thus potentially achieving higher functional group stability.

[0026] (3) This invention solves the engineering problem of the inability to simultaneously achieve efficiency, economy and environmental protection in traditional desolidification technologies for FCC slurries. It overcomes the comprehensive defects of centrifugal separation for removing fine particles, membrane filtration for easy fouling and rapid flux decline, chemical additive methods for high cost and potential secondary pollution, and solvent methods for huge energy consumption. It provides an efficient, low-consumption and environmentally friendly alternative to desolidification. More importantly, it solves the "black box" problem caused by the unclear core mechanism in emerging biomass-assisted desolidification technologies. Through systematic experimental design and characterization analysis, it clarifies and verifies for the first time the core scientific conclusion that "physical pore structure is the dominant factor determining desolidification efficiency". Specifically, it solves the following key cognitive bottlenecks: The dominant mechanism of deconsolidation has been clarified: it has been determined that physical adsorption and spatial retention play a decisive role in the process of biomass-assisted deconsolidation, rather than simple surface chemical action, thus ending the previous controversy about the dominant mechanism. A clear structure-property relationship was established: the direct positive correlation between the physical structural parameters of biomass materials, such as specific surface area, pore volume and pore connectivity, and their desolidification performance was revealed, providing a clear theoretical basis and optimization direction for the targeted design and modification of high-performance adsorption materials. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the centrifugal deconsolidation mechanism of wheat straw assisted by different modification methods in the experimental examples; Figure 2 The effects of the three model components cellulose, hemicellulose and lignin on the deashing effect of FCC oil slurry in the experimental example are: (a) the effect of different biomass types on the ash content of FCC oil slurry; (b) the effect of different biomass types on the ash removal ratio of FCC oil slurry. Figure 3 The effects of different modified wheat straws on the deashing effect of FCC oil slurry in the experimental examples are: (c) the effect of wheat straws with different modification methods on the ash content of FCC oil slurry; and (d) the ash removal ratio of FCC oil slurry by wheat straws with different modification methods. Detailed Implementation

[0028] Example 1 A method for efficiently removing solid impurities from FCC oil slurry using a porous straw-based adsorbent includes the following steps: S1. Preparation of porous straw-based adsorbent: S1-1, One-time alkali method for pore formation: After washing and drying wheat straw, it is crushed and passed through an 80-mesh sieve. The pretreated wheat straw is mixed with the first mixed liquid at a ratio of 1g:5mL. The mixture is reacted at 90℃ for 2h, followed by solid-liquid separation. The resulting solid product is washed with deionized water until neutral to obtain primary porous material. The first mixture is an aqueous solution of sodium hydroxide and sodium sulfite, wherein the molar concentration of sodium hydroxide is 3 mol / L and the molar concentration of sodium sulfite is 1 mol / L. S1-2, Secondary sulfonation crosslinking: The primary porous material is mixed with the second mixture at a ratio of 1g:6mL. The mixture is reacted at 80℃ for 1.5h, followed by solid-liquid separation. The resulting solid product is washed with deionized water until neutral and dried at 50℃ to obtain a porous straw-based adsorbent. The second mixture is an aqueous solution of sodium sulfite and sodium metaborate, wherein the concentration of sodium sulfite is 0.6 mol / L and the concentration of sodium metaborate is 0.3 mol / L. S2. Oil Slurry Deconsolidation: FCC oil slurry dilution involves mixing it with diesel fuel at a volume ratio of 1:1. After dilution, a porous straw-based adsorbent is added at a concentration of 5 wt% of the diluted FCC oil slurry. The adsorbent is stirred to ensure full contact with the solid particles in the FCC oil slurry. The stirring temperature is 35°C, the stirring speed is 250 rpm, and the stirring time is 2 hours. The resulting clarified deconsolidated FCC oil slurry is obtained by centrifugation at a speed of 4000 rpm for 15 minutes.

[0029] Example 2 The difference between this embodiment and Embodiment 1 is that: The straw is corn stalks.

[0030] Example 3 The difference between this embodiment and Embodiment 1 is that: In S1-1, the mixing ratio of straw to the first mixed liquid is 1g:3mL. The mixture is reacted at 85℃ for 3h, followed by solid-liquid separation. The resulting solid product is washed with deionized water until neutral to obtain the primary porous material.

[0031] Example 4 The difference between this embodiment and Embodiment 1 is that: In S1-1, the mixing ratio of straw to the first mixed liquid is 1g:10mL. The mixture is reacted at 100℃ for 1h, followed by solid-liquid separation. The resulting solid product is washed with deionized water until neutral to obtain the primary porous material.

[0032] Example 5 The difference between this embodiment and Embodiment 1 is that: The first mixture is an aqueous solution of sodium hydroxide and sodium sulfite, wherein the molar concentration of sodium hydroxide is 3.5 mol / L and the molar concentration of sodium sulfite is 0.5 mol / L.

[0033] Example 6 The difference between this embodiment and Embodiment 1 is that: The first mixture is an aqueous solution of sodium hydroxide and sodium sulfite, wherein the molar concentration of sodium hydroxide is 2 mol / L and the molar concentration of sodium sulfite is 1.2 mol / L.

[0034] Example 7 The difference between this embodiment and Embodiment 1 is that: The first mixture is an aqueous solution of sodium hydroxide and sodium sulfite, wherein the molar concentration of sodium hydroxide is 2.2 mol / L and the molar concentration of sodium sulfite is 0.7 mol / L.

[0035] Example 8 The difference between this embodiment and Embodiment 1 is that: S1-2, Secondary sulfonation crosslinking: The primary porous material is mixed with the second mixture at a ratio of 1g:4mL. The mixture is reacted at 70℃ for 2h, followed by solid-liquid separation. The resulting solid product is washed with deionized water until neutral and dried at 45℃ to obtain a porous straw-based adsorbent.

[0036] Example 9 The difference between this embodiment and Embodiment 1 is that: S1-2, Secondary sulfonation crosslinking: The primary porous material is mixed with the second mixture at a ratio of 1g:8mL. The mixture is reacted at 90℃ for 1h, followed by solid-liquid separation. The resulting solid product is washed with deionized water until neutral and dried at 55℃ to obtain a porous straw-based adsorbent.

[0037] Example 10 The difference between this embodiment and Embodiment 1 is that: The second mixture is an aqueous solution of sodium sulfite and sodium metaborate, wherein the concentration of sodium sulfite is 0.4 mol / L and the concentration of sodium metaborate is 0.2 mol / L.

[0038] Example 11 The difference between this embodiment and Embodiment 1 is that: The second mixture is an aqueous solution of sodium sulfite and sodium metaborate, wherein the concentration of sodium sulfite is 0.2 mol / L and the concentration of sodium metaborate is 0.1 mol / L.

[0039] Example 12 The difference between this embodiment and Embodiment 1 is that: The second mixture is an aqueous solution of sodium sulfite and sodium metaborate, wherein the concentration of sodium sulfite is 0.8 mol / L and the concentration of sodium metaborate is 0.5 mol / L.

[0040] Example 13 The difference between this embodiment and Embodiment 1 is that: S2. Oil Slurry Deconsolidation: FCC oil slurry dilution involves mixing it with diesel fuel at a volume ratio of 1:2. After dilution, a porous straw-based adsorbent is added at a concentration of 10 wt% of the diluted FCC oil slurry. The mixture is stirred to ensure full contact with the solid particles in the FCC oil slurry. The stirring temperature is 25°C, the stirring speed is 200 rpm, and the stirring time is 3 hours. The resulting clarified and deconsolidated FCC oil slurry is obtained by centrifugation at a speed of 5000 rpm for 20 minutes.

[0041] Example 14 The difference between this embodiment and Embodiment 1 is that: S2. Oil Slurry Deconsolidation: FCC oil slurry dilution involves mixing it with diesel fuel at a volume ratio of 1:1.5. After dilution, a porous straw-based adsorbent is added at a concentration of 15 wt% of the diluted FCC oil slurry. The mixture is stirred to ensure full contact with the solid particles in the FCC oil slurry. The stirring temperature is 55°C, the stirring speed is 300 rpm, and the stirring time is 1 hour. The resulting clarified and deconsolidated FCC oil slurry is obtained by centrifugation at a speed of 6000 rpm for 10 minutes.

[0042] Experimental Example Adsorbent materials prepared by different methods were used to adsorb FCC slurry, and the adsorption treatment method in S2 of Example 1 was followed. The following comparative experimental groups were set up respectively: The blank control group was denoted as WS-Blank. Wheat straw treated with 1 mol / L hydrochloric acid solution is denoted as WS-Acid; The adsorbent in Example 1 is designated as WS-Alkali; Wheat straw treated successively with 1 mol / L hydrochloric acid solution and a mixed solution of 2.5 mol / L sodium hydroxide and 0.5 mol / L sodium sulfite is denoted as WS-Acid-base. Wheat straw treated successively with 1 mol / L hydrochloric acid solution, a mixed solution of 2.5 mol / L sodium hydroxide and 0.5 mol / L sodium sulfite, and an aqueous solution of 6.9% citric acid and 6.5% sodium dihydrogen phosphate is denoted as WS-Citric. Wheat straw treated successively with 1 mol / L hydrochloric acid solution, a mixed solution of 2.5 mol / L sodium hydroxide and 0.5 mol / L sodium sulfite, and 20% rosin ethanol solution is denoted as WS-Rosin. The specific markings are shown in the table below: Table 1. Labels for each experimental group

[0043] Mechanisms of wheat straw-assisted centrifugal deconsolidation of FCC slurry under different modification methods, such as Figure 1As shown, the desolidation efficiency mainly depends on the synergistic effect between the reconstruction of the physical pore structure and the regulation of surface chemical properties of the modified straw. Among them, the optimization of the pore structure is the dominant factor determining the desolidation efficiency. WS-Alkali exhibits the best performance (deashing rate of 93.76%). By dissolving lignin and hemicellulose, it significantly increases the specific surface area and pore volume, forming a highly interconnected porous network that provides sufficient physical adsorption and bridging sites for solid particles. At the same time, the hydrophilic functional groups such as sulfonic acid groups introduced on the surface enhance the interfacial affinity with particles, achieving a synergistic enhancement of physical retention and chemical adsorption. In contrast, WS-Acid, due to pore collapse, WS-Citric, due to pore filling by the modifier, and WS-Rosin, due to pore blockage by the hydrophobic coating, all failed to effectively construct the spatial carrier required for adsorption, resulting in limited desolidation effects. While WS-Acid-base deeply purifies the components, its desolidation efficiency is low due to the failure of the pore network. Therefore, an ideal modification strategy should prioritize the construction of porous structures with high specific surface area and high connectivity, supplemented by appropriate surface chemical modifications, to achieve efficient capture and separation of fine particles through a synergistic mechanism of "physical adsorption as the main method and chemical adsorption as the auxiliary method".

[0044] like Figure 2 As shown, under the conditions of 50% diesel ratio, 4000 rpm, 10 min centrifugation time, and 5% addition amount, the effects of three model components—cellulose, hemicellulose, and lignin—and different modified wheat straw on the deashing effect of FCC oil slurry were investigated. The results showed that hemicellulose had the best deashing effect, reducing the ash content to 79.37 ppm (removal rate 98.35%), while cellulose and lignin had ash contents of 955.66 ppm and 3747.33 ppm, respectively. The amorphous, highly branched three-dimensional structure of hemicellulose allows it to form an open, porous interface architecture in the oil phase. This structure not only greatly increases the specific surface area, thus constructing active microregions rich in polar functional groups on its surface, these microregions can efficiently adsorb hydrophilic solid particles and achieve "adsorption-bridging" through flexible molecular chains, which is key to its efficient desolidation in the oil phase. In contrast, cellulose's rigid crystalline structure results in a limited specific surface area and a lack of porosity, making it unable to effectively fix water and bridge particles. Lignin, due to its inherent hydrophobic properties and the dense aggregation that easily occurs in the oil phase, severely limits its interfacial contact and interaction with hydrophilic solid particles, resulting in the worst ability to assist in deconsolidation.

Claims

1. A method for efficiently removing solid impurities from FCC oil slurry using a porous straw-based adsorbent, characterized in that, Includes the following steps: S1. Preparation of porous straw-based adsorbent: S1-1, One-time alkali method for pore formation: The pretreated straw is mixed with the first mixture and reacted at 85~100℃ for 1~3h. Then the solid and liquid are separated, and the resulting solid product is washed until neutral to obtain the primary porous material. The first mixture is a mixed aqueous solution of sodium hydroxide and sodium sulfite, wherein the molar concentration of sodium hydroxide is 2~3.5 mol / L and the molar concentration of sodium sulfite is 0.5~1.2 mol / L; S1-2, Secondary sulfonation crosslinking: The primary porous material is mixed with the second mixture and reacted at 70~90℃ for 1~2h. Then, the solid and liquid are separated and the resulting solid product is washed until neutral and dried to obtain a porous straw-based adsorbent. The second mixture is an aqueous solution of sodium sulfite and sodium metaborate, wherein the concentration of sodium sulfite is 0.2~0.8 mol / L and the concentration of sodium metaborate is 0.1~0.5 mol / L; S2. Desolidification of FCC oil slurry: After diluting the FCC oil slurry, add the porous straw-based adsorbent, stir to ensure full contact with the solid particles in the FCC oil slurry, and centrifuge to obtain clear desolidified FCC oil slurry.

2. The method for efficiently removing solid impurities from FCC oil slurry using a porous straw-based adsorbent according to claim 1, characterized in that, In S1-1, the straw is wheat straw.

3. The method for efficiently removing solid impurities from FCC oil slurry using a porous straw-based adsorbent according to claim 1, characterized in that, In S1-1, the pretreatment method is to wash and dry the straw, then crush it and pass it through an 80-mesh sieve.

4. The method for efficiently removing solid impurities from FCC oil slurry using a porous straw-based adsorbent according to claim 1, characterized in that, In S1-1, the mixing ratio of the straw to the first mixture is 1g:3~10mL, and deionized water is used for washing.

5. The method for efficiently removing solid impurities from FCC oil slurry using a porous straw-based adsorbent according to claim 1, characterized in that, In S1-2, the mixing ratio of the primary porous material to the second mixture is 1g:4~8mL. During washing, deionized water is used, and the drying temperature is 45~55℃.

6. The method for efficiently removing solid impurities from FCC oil slurry using a porous straw-based adsorbent according to claim 1, characterized in that, In S2, FCC slurry dilution involves mixing it with diesel fuel, with a volume ratio of FCC slurry to diesel fuel of 1:1~2.

7. The method for efficiently removing solid impurities from FCC oil slurry using a porous straw-based adsorbent according to claim 1, characterized in that, In S2, the amount of the porous straw-based adsorbent added is 5-15 wt% of the mass fraction of the diluted FCC slurry.

8. The method for efficiently removing solid impurities from FCC oil slurry using a porous straw-based adsorbent according to claim 1, characterized in that, In S2, the stirring temperature is 25~55℃, the stirring speed is 200~300rpm, and the stirring time is 1~3h.

9. The method for efficiently removing solid impurities from FCC oil slurry using a porous straw-based adsorbent according to claim 1, characterized in that, In S2, the centrifugal speed is 4000~6000 rpm and the centrifugal time is 10~20 min.

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