Table of Content

12 May 2023, Volume 54 Issue 5

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PRACTICE AND PROSPECT OF DIGITAL TRANSFORMATION OF GREEN, STABLE AND HIGH EFFICIENT OPERATION OF CATALYTIC CRACKING UNIT

2023, 54(5):  1-6. 

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Digital transformation serves as a powerful engine to promote the development of the petrochemical industry toward green, low-carbon, and high-quality. In this paper, an overview of the background of digital transformation is provided, the main problems being encountered in the production and operation phases of the catalytic cracking unit is analyzed, and a digital transformation application case of "catalytic cracking unit level" is elaborated on. A practical example of a catalytic cracking unit of SINOPEC is introduced with highlighting the implementation process and application effect of digital transformation on a green, stable and high efficient operation. Finally, the prospects of the key development direction of digital transformation in the petrochemical industry is proposed.

STUDY ON DIRECT CATALYTIC CRACKING OF INFERIOR VACUUM RESIDUE WITH HIGH CARBON RESIDUE

2023, 54(5):  7-12. 

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In view of the problem that the production of high sulfur petroleum coke from delayed coker may be restricted in market, the feasibility of on-line co-production of high-pressure steam from coke in catalytic cracking of inferior vacuum residue with high carbon residue was studied. Using inferior Middle East mixed vacuum residue with 18.62% of carbon residue as feed and FCC equilibrium catalyst as catalyst, the effects of reaction temperature, mass ratio of catalyst to oil and space velocity on the catalytic cracking of vacuum residue were investigated in a fixed fluidized bed reactor, and the use of the products was discussed according to their properties. The results showed that the process route of inferior vacuum residue with high carbon residue catalytic cracking combined with generating high-pressure steam was feasible. With the increase of reaction depth, the dry gas and coke yields increased, and the total liquid yield decreased. The processing conditions could be flexibly adjusted according to the product demand to produce more distillate oil or more steam. Under different reaction conditions, the total yield of ethylene, propylene and butene was lower than that of typical catalytic cracking, and the content of aromatics in the distillates was relatively high, which could produce light aromatics and also be used as feedstock for the production of graphite-like carbon materials.

STUDY ON NON-HYDROGEN CONSUMPTION HEAVY AROMATICS CRACKING TECHNOLOGY

2023, 54(5):  13-17. 

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In order to efficiently convert heavy aromatics (mainly C₉-C₁₁A) from naphtha distillate into light aromatics without hydrogen consumption, a pilot-scale study on catalytic cracking of heavy aromatics was carried out using heavy aromatics as feedstock in DCC unit. The results indicated that the heavy aromatics were efficiently converted and benzene, toluene, xylene (BTX) and low carbon hydrocarbons were formed under the action of special catalyst A. The conversion rate of heavy aromatics was over 80%, the yield of BTX was over 40%, and the yield of light olefins was about 6% at different reaction temperature; the yield of BTX was the highest at 640 ℃ (43.38%), and the yield of BTX + ethylene and propylene was over 50%. The ratio of BTX could be adjusted within certain range by adjusting the reaction temperature. With the increase of reaction temperature, the yield of benzene and toluene increased, while the yield of xylene decreased. The non-aromatic hydrocarbons in the feed were efficiently converted, and the aromatic hydrocarbons in the gasoline product were highly concentrated. Light aromatics could be produced by distillation without adding a new aromatics extraction unit, which could greatly reduce the energy consumption of BTX production and realize quality improvement and efficiency enhancement in refining and chemical enterprises

EFFECT OF NAPHTHALENE COMPOUNDS ON THE COMPOSITION AND STRUCTURE OF NEEDLE COKE PREPARED BY AROMATIC ENRICHED FRACTION FROM FCC SLURRY

2023, 54(5):  18-23. 

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Needle coke was prepared by two-stage coking from aromatic fraction of paraffin-based catalytic cracking slurry (FCCDO) with the addition of different naphthalene compounds (naphthalene, 1-methylnaphthalene, tetrahydronaphthalene and decahydronaphthalene). The influence of naphthalenes on the composition and the properties of needle coke was investigated by elemental analysis, FT-IR and group composition, etc. The results showed that the addition of small molecular aromatics promoted the formation of carbonaceous mesophase with the increasing of naphthalene content. Aromatics with alkyl chains could improve the carbonization activity of the system through free radical and hydrogen transfer reactions, which could effectively increase the condensation degree of the products. At the same time, the aromatics with naphthenic structure could also change the rheological properties of the system through ring-opening reaction and hydrogen transfer reaction, and reduce the viscosity of the system, thus reducing the condensation degree of the product.

LARGE-SCALE COMMERCIAL APPLICATION OF FLEXIBLE SOLVENT DEASPHALTING (RFSD) TECHNOLOGY

2023, 54(5):  24-28. 

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Based on the deep understanding of the composition, structure and liquid-liquid extraction theory of residue, SINOPEC Research Institute of Petroluem Processing Co., Ltd. (RIPP) has studied the dissolution and mass transfer characteristics of heavy oil in different solvent systems, the RIPP flexible solvent deasphalting (RFSD) technology was developed. The industrial operation data of a 1.6 Mt/a solvent deasphalting unit in a refinery showed that a two-stage process was adopted with vacuum resid with carbon residue of 13.48% as raw material and butane as solvent, and a light deasphalted oil (LDAO）with a yield of 35.58%, carbon residue value of 2.85% and mass fraction of metal（Ni+V）of 2.42 μg/g could be obtained. The LDAO could be used as raw material for deep catalytic cracking and BS bright oil base oil. The operation energy consumption of the unit was 943.0 MJ/t.

EFFECT OF ALKYLATION OF FCC GASOLINE ON COKING INHIBITION IN THE HEAT EXCHANGER OF S Zorb UNIT

2023, 54(5):  29-35. 

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In view of coking problem S Zorb unit feed heat exchanger, the causes of coking formation were analyzed, and the effect of alkylation desulfurization and olefin reduction on the coking properties of FCC gasoline was studied, and the catalyst, reaction temperature and reaction space velocity for the alkylation of FCC gasoline were optimized. The results showed that Amberlyst 35 resin had the best catalytic performance for FCC gasoline alkylation reaction among the four selected catalysts. The optimized alkylation temperature of FCC gasoline was 90 ℃, the space velocity was 1.0 h^-1 and the pressure was 0.5 MPa. Under optimum conditions, the coking amount of the treated gasoline on an iron disc was significantly reduced, but the octane number and Reid vapor pressure were also decreased. The octane number and Reid vapor pressure of the gasoline could be increased by adding C₄ mixed hydrocarbon to the gasoline after the alkylation reaction, so that the alkylated gasoline could meet the quality standard.

STUDY ON REGENERATION OF SPENT DIESEL HYDROGENATION CATALYST AND ITS APPLICATION IN RESIDUE HYDRODESULFURIZATION

2023, 54(5):  36-41. 

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The effects of different regeneration methods on physicochemical properties of spent diesel hydrogenation catalyst and its residue hydrodesulfurization activity were investigated by conventional method. Firstly, the spent catalyst was regenerated, the pores of the catalyst were unblocked, and the aggregated active metals were redispersed, but the activity of the catalyst used in residue hydrodesulfurization was significantly lower than that of the standard catalyst. Secondly, the catalyst was modified from the perspective of pore expansion and strengthening the metal-support interaction.After the pore was expanded, the aggregated low active metals in the catalyst were removed, the pore structure of the catalyst was further optimized, and the utilization rate of active metals was improved.The residue hydrodesulfurization performance of the catalyst was significantly improved after strengthening the MSI. Finally, coupling the above two modification methods, the optimized catalyst was obtained, and the activity of the catalyst used in residue hydrodesulfurization was close to the level of the standard catalyst.

CAUSE ANALYSIS OF DEACTIVATION OF INDUSTRIAL DEOLEFINIZATION CATALYST FOR C₈+ AROMATICS FRACTION

2023, 54(5):  42-47. 

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The pore structure, crystal structure and surface acid properties of commercial fresh, deactivated and regenerated catalysts for olefin removal were studied by means of N₂ adsorption-desorption, XRD, NH₃-TPD and Py-IR, the commercial deactivated catalyst were characterized by TG and ¹³C NMR, and the organic composition in toluene-ethanol washing solution of deactivated catalyst was analyzed by FT-IR. The deolefinization activity of commercial fresh, deactivated and regenerated catalysts was evaluated by using catalytic reforming C₈+ aromatics as raw materials. The results showed that the specific surface area and pore volume of the deactivated catalyst decreased significantly, the average pore size increased, the total acid content decreased, and the acid strength of B acid and L acid decreased significantly. The main cause of deactivation of the deolefinization catalyst was the carbon (coke) deposited on the surface and in the pores of the catalyst. The carbon (coke) was mainly formed by the condensation of aromatics and assisted by the condensation of olefin. After regeneration, the specific surface area, pore volume, total acid amount, B acid and L acid amount recovered basically to the level of fresh catalyst, and the initial deolefinization activity restored to 96 %.

SELECTIVE AEROBIC OXIDATION OF CYCLOHEXANE BY CeX ZEOLITE

2023, 54(5):  48-56. 

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In this paper, NaX zeolite was modified with Ce ions by liquid phase ion exchange method. After comparing the catalytic effects of Ce(III)X and Ce(IV)X, the effect of ion occupation and valence state on cyclohexane oxidation were investigated under different ion exchange rates and different calcination atmosphere. The modified catalysts were characterized by ICP, XRD, BET, XPS, H2-TPR. The results showed that the conversion of cyclohexane on Ce(III)X was 2.6 times higher than that on NaX, and slightly higher than that on Ce (IV) X; the conversion of cyclohexane was increased from 3.15% to 8.54% with the Ce(III)X ion occupation increasing from 13.4% to 76.2%, and the conversion of cyclohexane was reduced to 7.5% and 5.7% with Ce(III)X calcinated in vacuum and air, respectively. The reduction of catalytic activity was related to the migration of Ce(III) ions to sodalite cages and valence variation. At the same time, the optimum process conditions were obtained: oxygen pressure was 1.5 MPa, reaction temperature was 150℃, stirring speed was 800 r/min, and reaction time was 2 hours. The conversion of cyclohexane was 8.54%, and the selectivity of target products (cyclohexanone and cyclohexanol) was 86.39% under the optimum process conditions.

REACTION OF TERMINAL OLEFINS DURING S Zorb DESULFURIZATION PROCESS

2023, 54(5):  57-64. 

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Model of 10% (w) 1-hexene in FCC gasoline was used to study reactions of terminal olefins during S Zorb desulfurization process in a fixed bed reactor. The results showed that reactions of saturating and double bond isomerization could take place in the process of adsorptive desulfurization. The reaction temperature, the reaction pressure, the mole ratio of H2 to hydrocarbons and weight space velocity had significantly effects on saturating and isomerizing reactions of 1-hexene. High reaction temperature, low reaction pressure and low mole ratio of H2 to hydrocarbons promoted the double bond isomerization of olefin, such as the double bond isomerization of 1-hexene to 2-hexene and 3-hexene. Internal olefins had higher octane number and lower hydrogenation saturation activity, so the double bond isomerization of internal olefins formed by end-olefin reaction reduced the octane number loss during S Zorb desulfurization process.

CFD-PBM SIMULATION OF LIQUID-LIQUID DISPERSION IN DOUBLE-LAYER STIRRING TANK

2023, 54(5):  65-72. 

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The fragmentation kernel function was applied to the population balance model（PBM）and coupled with computational fluid dynamics (CFD) method to simulate size distribution and liquid-liquid dispersion characteristics of droplets in the stirring tank under different types of impeller combinations. The results showed that the propeller (TXL) could promote the axial mixing of the fluid, while the turbine paddle was beneficial to the dispersion of the fluid. Meanwhile, there were significant differences in the flow field characteristics under different impeller combinations. At the same rotating speed, the suction (PM) + TXL combined oars had smaller power consumption, while the RT + RT combined oars had larger power consumption. The presence of baffles could effectively promote droplet breaking, and the stirring performance of the PM+RT combined oars was largely enhanced by the baffle. Moreover, simulation results showed that the dispersed phase was rapidly broken into small-sized droplets in the first few minutes, and then the droplet diameter became stable with the evolution of the operating time. Based on the results of this study, the application of baffle should be considered first in the commercial application of double impeller stirring tank. When the droplet dispersion performance was not required, the PM + TXL combined impeller with axial flow type should be preferred; when high droplet dispersion performance was required, the PM + RT combined impeller with baffle plate should be preferred.

STUDY ON REACTION ACTIVITY AND TRIBOLOGICAL PROPERTIES OF SULFUR-PHOSPHORUS EXTREME PRESSURE ANTI-WEAR AGENT AND ESTER OIL-BASED AGENT

2023, 54(5):  73-79. 

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Based on density functional theory (DFT), parathion-based extreme pressure anti-wear agent (EP) and ester oil agent were geometrically optimized, and their global and local reactive sites and quantum chemical parameters of the structure were calculated; these two kinds of additives were added into the emulsion, and the tribological properties were investigated by four-ball test; the morphology and element distribution on the surface of four-ball test steel balls were characterized by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The results showed that the reactive sites of EP molecules were mainly distributed on S、Zn and other polar atoms. The emulsion containing zinc dialkyl dithiophosphate (ZDDP), oil agent ethyloleate (EO), compound emulsifier and rust-preventing agent benzotriazole (BTA) had excellent extreme pressure anti-wear performance, its maximum no-bite load was 1 403 N, the friction coefficient was 0.029, the wear spot diameter was only 0.69 mm, and the extreme pressure anti-wear lubrication coefficient was 11.16.

STUDY ON PREPARATION OF TETRAUREA LUBRICATING GREASE BY PREFABRICATION METHOD

2023, 54(5):  80-87. 

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The influence of the preparation conditions on the basic properties of tetraurea grease using prefabrication method was investigated, the mechanism of the preparation process was discussed from the perspective of the structure-activity relationship, and the relationship between the macro-properties and the micro-structure was understood. The optimized preparation conditions and basic steps were as follows: reacting at 50-70 ℃ for 30 min, a tetrauret thickener was obtained, which was added to the base oil, stirred and heated to 170-180 ℃, and refined at constant temperature for 1.5 h, the tetrapolyurea grease was obtained after cooling and grinding. The results of performance analysis of lubricating grease showed that the tetrapolyurea grease was prepared from the lightly refined naphthenic base oil, 20% tetrapolyurea thickener by mass and 0.8% extreme pressure antiwear agent by mass. The drop point, working cone penetration and oil separation rate of the prepared tetrapolyurea grease were 318 ℃, 281(0.1 mm) and 0.83%, respectively, and the other properties, such as water resistance, similar viscosity, oxidation stability, extreme pressure and wear resistance, met the quality standard SH/T0789―2007.

THE UNDERGROUND MIGRATION AND DISTRIBUTION OF PETROLEUM CONTAMINATION AT A REFINERY WASTE WATER TREATMENT PLANT

2023, 54(5):  88-96. 

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With the rapid development of petrochemical industry, petrochemical pollutants from production process due to leakage, maintenance, accidents can penetrate into soil and ground water, and cause the contaminate of soil and ground water. Based on the comprehensive analysis of the existing data, the types of pollutants on the site were determined to be petroleum hydrocarbon 1,1,2-trichloroethane, 1,2,3-Trichloropropane and benzo[a] pyrene. By means of GMS and SURFER software simulation, a three-dimensional visualization model of polluted stratum media and characteristic pollution space was constructed. The results showed that the filling soil, silty clay and pebbles were polluted to different degrees, and the pollution plume extends along the direction of ground water flow field. The effects of lithology conditions on pollutant migration were comprehensively analyzed, which provided basis for pollution risk assessment, pollution prevention and remediation.

IMPROVING CAUSTIC SOLUTION UTILIZATION IN LPG SWEETENING PROCESS TO REALIZE ZERO DISCHARGE OF SPENT CAUSTICS

2023, 54(5):  97-100. 

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By analyzing the problems of high caustic consumption and large spent caustics discharge in the treating system of LPG sweetening process, the caustic scrubbing process of each LPG sweetening unit was improved and a spent caustics regeneration unit was added, and the total sulfur concentration of refined LPG in each unit is not more than 20 mg/m³, the product quality is significantly improved, and the consumption of fresh caustic solution and the discharge of caustic residue are significantly reduced. Through utilizing the old fiber membrane caustics CO₂ neutralization device, the caustics wet oxidation unit can be stopped, realizing zero discharge of caustics.

TPYE SELECTION OF CRUDE OIL FOR STRAIGHT-RUN ASPHALT PRODUCTION BASED ON SVDD METHOD

2023, 54(5):  101-107. 

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Straight-run asphalt production is the main way to produce road asphalt, which has significant advantages in economy and energy efficiency. However, the selection of crude oil in this production process usually depends on qualitative analysis and historical experience while lacking complete theoretical data support. Through collecting a large number of successful cases of asphalt production, extracting the physical properties data of corresponding crude oil and processing and analysis, combined with the SVDD single-value classifier characteristics, a support vetor data description(SVDD-based) model for identifying the types of bituminous crude oil produced by straight-run asphalt was established. Based on the model, 273 types of crude oil in the SINOPEC crude oil database were mined and identified, and 46 types of crude oil suitable for straight-run asphalt production were finally obtained. Furthermore, through feasibility analysis, the validity of single-value classifier in crude oil data mining was confirmed, which provided theoretical support for the management decision of refinery enterprises. This method not only can clarify the selection space of oil for asphalt production, but also reduces the cost of trial and error of crude oil selection and improves the feasibility of asphalt production.

PROCESS SIMULATION AND OPERATION OPTIMIZATION OF DELAYED COKING ABSORPTION-STABILIZATION SYSTEM

2023, 54(5):  108-112. 

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The 1.85 Mt/a delayed coking unit of SINOPEC Jinling Company was taken as an example to solve the problem of poor separation effect in the absorption-stabilization system of delayed coker. Process simulation software PetroSIM was used to simulate and analyze the process of the absorption-stabilization system. The results showed that the simulation process parameters were basically consistent with the actual operation. On this basis, the actual production process was analyzed, and the effects of operating variables, such as the flow rate of additional absorbent, the temperature of absorbent, the feeding mode of desorption column and the reflux ratio of stabilizing column, on the separation effect and energy load of absorption-stabilization system, were investigated. Based on the simulation results, the unit was optimally operated. After optimization, the molar fraction of C₃+ in dry gas decreased to 2.37%, and the output of liquefied petroleum gas increased by 0.69 t/h.

EXTRACTION AND ANALYSIS OF PETROLEUM HYDROCARBONS FROM REFINERY WASTE CATALYSTS

2023, 54(5):  113-119. 

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A method for the extraction and analysis of C₁₀-C₄₀ petroleum hydrocarbons in refinery waste catalysts was established by using accelerated solvent extraction-gas chromatography method. The purification effects of solid phase extraction columns with different packings and elution solvents were investigated. The analysis conditions of gas chromatography were optimized, and the accuracy and the recovery rate of the method were evaluated. The results showed that the suitable column for petroleum hydrocarbon extraction was magnesium silicate column or silica gel solid phase extraction column, and the suitable elution solvents were n-hexane-dichloromethane mixed solvent with a volume ratio of 4:1(magnesium silicate column) and n-hexane-dichloromethane mixed solvent with a volume ratio of 9:1(silica gel column) , respectively. The polycyclic aromatic hydrocarbon recoveries of the two extraction columns were 94%-100%, and the calibration curves of n-alkanes were determined by GC-FID with a relative deviation of 0.6%-10.9% and a 0.999 3, respectively; the recoveries of n-alkanes and heavy oil were 74% and 84%, respectively, which showed that the method could meet the analysis of petroleum hydrocarbons in refinery waste catalysts. The carbon number distribution and content of petroleum hydrocarbon (C₁₀-C₄₀) in different sources of refinery catalyst were found to be significantly different, this was mainly related to the corresponding process and raw material characteristics of the waste catalyst.

ANALYSIS AND TREATMENT OF AMMONIUM SALT SCALING IN REACTION SYSTEM OF DIESEL HYDROGENATION UNIT

2023, 54(5):  120-124. 

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The phenomenon of ammonium salt scaling and corrosion of high-pressure heat exchanger in the reaction system of a diesel hydrofining unit and its influence on the operation of the unit were introduced, the crystallization temperature of ammonium chloride determined by detailed calculation coincided with the operation data of the high-pressure heat exchanger, and then the scheme and implementation effect of online water washing were introduced, which can be used as a reference for the analysis and treatment of the scaling of ammonium salt in hydrofining unit.

RECENT PROGRESS ON CATALYTIC PYROLYSIS OF WASTE PLASTICS TO PRODUCE LIGHT OLEFINS, LIGHT FUEL OIL AND AROMATICS

2023, 54(5):  125-132. 

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With the increasing production of waste plastics and the reduction of fossil energy, the issue of carbon resources recycling has attracted widespread attention. Catalytic pyrolysis technology is a promising treatment solution for the recycling of waste plastics at present, which can solve the problems of environmental pollution and energy shortage. In this paper, the production of light fuel oil and high value-added products by catalytic cracking of waste plastics were reviewed, the effects of waste plastics composition, reaction temperature, reactor type, and catalyst type on the yield of light olefins, light fuel oil and aromatics were investigated, and the application prospect of catalytic cracking of waste plastics to produce light olefins, light fuel oils and aromatics was briefly described. This research was of great significance to the efficient conversion and high-value utilization of waste plastics.