Table of Content

12 August 2020, Volume 51 Issue 8

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SOLVENT SELECTION FOR AROMATIC EXTRACTION FROM LIGHT CYCLE OIL

2020, 51(8):  1-6. 

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The suitable model compounds were selected base on the analysis of hydrocarbon compositions of LCO to investigate the extraction effect of solvent on aromatic compounds in LCO and the relationship between solvent extraction performance and solvent physical parameters. It was found that the order of the selectivity coefficient of the studied solvents to aromatics was sulfolane> DMSO > furfural > DMF > NMP > DMAC. The dipole moment and dielectric constant of the solvent should be sufficiently different from those of the hydrocarbons in LCO in order to effectively separate the aromatic hydrocarbons in LCO. The selectivity coefficient of solvent to aromatics can be correlated with its solubility parameter. For the solvent with δD（dispersion force parameter, one of the solubility parameters）close to that of aromatics, the larger δP (polarity force), the better the selectivity coefficient to aromatics. At 40 ℃ and oil-mass ratio 1:1, the total aromatics mass fraction in the extracted oil obtained by DMF was only 87.2% in a single pass, while that of sulfolane was 97.3%. By introducing co-solvent into DMF to enhance δP, the total aromatics mass fraction and yield of extracted oil reached 96.5% and 29.9%, respectively under the same conditions.

COMMERCIAL PRACTICE OF METHANE- HYDROGEN GAS FROM C₂ RECOVERY UNIT AS FEED FOR HYDROGEN PLANT

2020, 51(8):  7-11. 

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In order to reduce the production cost of No.2 hydrogen production plant using natural gas as feed, SINOPEC Beijing Yanshan Company used the by-product methane hydrogen gas (methane more than 70% by volume) from the C₂ recovery unit as feed for No.2 hydrogen production plant. To avoid the adverse effect of nitrogen in the feed on the medium temperature shift process, the process risk was analyzed and the key process indexes were monitored and tracked. The application results showed that the plant operated normally, and the compressor load reduced from 71% to 60%. The plant using the methane hydrogen feed can save 23.28 million Yuan/a on natural gas cost and compressor power consumption.

STUDY ON AROMATICS REMOVAL FROM FCC DIESEL BY EXTRACTION

2020, 51(8):  12-18. 

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The traditional aromatics extraction process requires the use of high temperature （180-240 ℃）steam at 1.0-1.3 MPa, which has the disadvantages of high energy consumption and high temperature leading to fast deterioration of solvent performance. In this paper, liquid-liquid extraction method at low temperature under atmospheric pressure was used to remove polycyclic aromatic hydrocarbons from FCC diesel. The operating conditions of extraction dearomatization, aromatics recovery, reverse extraction and solvent regeneration were investigated. The results showed that the optimal parameters for extraction dearomatization process were as follows: the agent A /FCC diesel volume ratio was 1.5, the extraction temperature was 50 ℃, the extraction time was 5 min, and the phase separation time was 5 min, the aromatics recovery conditions: agent B / (agent A + aromatics) volume ratio was 0.2, the extraction temperature was 50 ℃, the extraction time was 4 min and the phase separation time was 3 min. Under the optimal extraction conditions, the yield of mixed aromatics product was 29.29%, the mass fraction of mixed aromatic was 93.71%. The solvent was regenerated under the best reverse extraction conditions: agent C / (agent A + agent B) volume ratio was 0.2, reverse extraction 40 ℃ and 3 min, the phase separation time was 3 min, and vacuum distillation at 78℃. The extraction effect of the regenerated solvent was as good as the fresh one. Finally, the principle process of liquid-liquid extraction dearomatization for FCC diesel was proposed.

STUDY ON PRODUCTION OF INDUSTRIAL WHITE OIL FROM HYDROGENATED OIL OF DIRECT COAL LIQUEFACTION

2020, 51(8):  19-23. 

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Two types of hydrofining catalysts were used to produce industrial white oil from hydrogenated oil of direct coal liquefaction process in a two-stage hydrofining process. The results showed that the reaction temperature, pressure and volume space velocity had a great influence on desulfurization，denitrogenation and aromatics saturation reaction in the first stage of the process. At the conditions of 15 MPa， 380 ℃ and LHSV 0.4 h-1，the mass fractions of sulfur and nitrogen in product oil were 1.6μg /g and 1.5 μg /g, respectively，the desulfurization rate and denitrogenation rate reached 97.72% and 99.81%，respectively. The aromatics content in the product was 31.2% and the aromatics saturation rate was 55.9%. After the deep hydrofining in the second stage，the aromatics content in the product reduced to less than 5%. The products were cut in a true boiling point distillation device. The 280-300 ℃ and 300-320 ℃ distillates obtained can satisfy the No.5, No.7 industrial white oil (Ⅰ) industry standard requirements, respectively.

TECHNICAL MEASURES TO REDUCE OLEFIN CONTENT OF FCC GASOLINE

2020, 51(8):  24-29. 

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In order to reduce the olefin content in stabilized gasoline of FCC unit (MIP process) to meet the national VIA standard of vehicle gasoline, the optimization of operation conditions was carried out in a 4.8 Mt/a FCC unit. The results showed that the volume fraction of olefins in stabilized gasoline decreased by 2.4 percentage points by increasing the temperature of the first reaction zone by 4 ℃; the increase of micro-reaction activity of the equilibrium catalysts of 2.8 units led to a reduction of olefin content by 4.6 percentage points; recycling the crude gasoline at a rate of 15 t/h resulted in a reduction of olefin content by 1.3 percentage points, and increasing the final boiling point of stabilized gasoline by 4℃ would decline the olefin content by 0.3 percentage points. The main principles of technical measures are to enhance the hydrogen transfer reaction and the small molecule olefins cracking reaction. These reactions are secondary reactions and result in a high coke yield. The large oil refining enterprises should take the blending pool of gasoline into consideration and choose the appropriate olefin content of the stabilized gasoline to get the comprehensive benefits.

PREPARATION OF Ni/γ-Al₂O₃/FeCrAl MESH-TYPE CATALYST AND ITS CATALYTIC PERFORMANCE FOR METHANE STEAM REFORMING TO PRODUCE HYDROGEN

2020, 51(8):  30-36. 

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Ni/γ-Al₂O₃/FeCrAl mesh-type catalyst for methane steam reforming（MSR）was prepared by slurry method. The surface morphology，crystal structure，pore characteristics，thermal stability and adhesion between coating and substrate of the catalyst were studied by scanning electron microscope，X-ray diffraction，nitrogen physical adsorption, thermal shock, and ultrasonic vibration test techniques. The MSR test system was set up to evaluate the performance of the self-made mesh-type catalyst and commercial pellet catalyst at different temperatures and space velocities. The results showed that the mesh-type catalyst had a higher specific surface area and better conversion rate of CH₄ at high gas hourly space velocity than that of the commercial catalyst. However，there are still some problems for the mesh-type catalyst，such as high CO content in the product of SMR and carbon deposition on the catalyst，which need to be further optimized.

PREPARATION OF MESOPOROUS ZSM-5 ZEOLITE AND ITS PERFORMANCE IN FCC GASOLINE HYDROFINING

Jing-Feng Li Gao Haibo Yao Wenjun Xiang Yongsheng Zhang Yongze Wang Gaofeng

2020, 51(8):  37-42. 

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The mesoporous H-ZSM-5 zeolite with moderate pore structure and acidity was prepared by optimization of crystallization time, crystallization temperature and mass ratio of rubber latex-3/silicon in gel（R） using cheap rubber latex-3 as the mesoporous template，followed by steaming/citric acid combination treatments. The hydrogenation performance of FCC gasoline was evaluated for the octane number recovery catalyst prepared on the basis of this molecular sieve. The characterization results indicated that the optimum value of crystallization time, crystallization temperature and R was 48 h, 190 ℃ and 0.26, respectively. In addition, the combination treatments not only markedly increased the mesoporous ratio of H-ZSM-5 zeolite but also regulated its acidity in a wide range. The FCC gasoline with a sulfur content of 113 μg/g and a olefin volume fraction of 40.9% was used for the evaluation of the octane recovery catalyst. The hydrotreated gasoline by newly prepared catalyst, compared with that of industrial catalyst, had lower volume fraction of alkenes by 2.2 percentage points, higher volume fraction of iso-alkanes by 1.1 percentage points, higher volume fraction of aromatics by 1.1 percentage points,whilet he desulfurization rate increased by 11.5 percentage points, and the loss in research octane number (RON) decreased by 0.5 unit with the same liquid yield. The results indicated that the bigger average pore, higher ratio of strong Lewis acidity/Bronsted acidity and more weak acidity contribute to decrease olefin and sulfur content, to hold RON and to increase liquid yield of hydrotreated FCC gasoline product. Moreover, the bigger average pore is beneficial to the dispersion of active metals in mesoporous molecular sieves, so as to make it show higher desulfurization performance for FCC gasoline.

CAUSE ANALYSIS OF DEACTIVATION OF HYDROFINING CATALYST IN DIESEL HYDROCRACKING UNIT

2020, 51(8):  43-49. 

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It was found that the surface of hydrofining catalyst on the top of hydrofining reactor was covered with scale during the turnaround of a diesel hydrocracking unit and replacement of catalysts. After toluene extraction and regeneration, the hydrofining catalysts were analyzed using specific surface area and pore structure analyzer, carbon & sulfur analyzer, and scanning electron microscope (SEM) techniques. The results showed that the main cause of the catalyst deactivation is the impurities deposited on hydrofining catalyst. The deposition was inorganic components containing P, Si and Fe, showing eggshell type distribution on cross section of the catalyst. It is suggested that the refinery should strictly control the impurities content, such as P, Si and Fe in the feed, and load some silicon trap catalyst and optimize the grading of guard catalyst, so as to ensure the activity of the main catalyst and realize the smooth operation of the unit.

STUDY ON LANTHANUM MODIFIED Cu-SSZ-13 MOLECULAR SIEVE AS NH3-SCR CATALYST

2020, 51(8):  50-55. 

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The Cu-SSZ-13 molecular sieve was prepared by one-step process and then modified by lanthanum nitrate solution with different concentration. The modified molecular sieve were used as a NH3-SCR catalyst and characterized by XRD, BET, FT-IR, TPR and DRIFTS techniques. The NH3-SCR reaction results showed that the performance of La0.015-Cu-SSZ-13 catalyst was significantly better than that of Cu-SSZ-13 catalyst, and the NO conversion rate of La0.015-Cu-SSZ-13 catalyst was more than 90% in the temperature range of 175-450 ℃ with a good N2 selectivity. The NH3-SCR mechanism of La modified Cu-SSZ-13 is similar to Cu-SSZ-13 catalyst: ammonium nitrate, an intermediate species, is generated by surface ammonia species and nitrate species, and then ammonium nitrate is reduced by NO to generate N2 and H2O.

ACIDITY OF ZSM-35 ZEOLITE AND EFFECT ON N-BUTENE ISOMERIZATION

2020, 51(8):  56-61. 

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In order to determine qualitatively and quantitatively the internal and external acid sites of ZSM-35 zeolites, three types of ZSM-35 samples (GNJ, GNX, and GW) prepared under different crystallization and calcination conditions were characterized using NH3-TPD and 31P MAS NMR with different probe molecules. The selectivity and activity of n-butene isomerization of different catalysts were investigated. The results showed that the amount of Bronsted acid site in ZSM-35 zeolites were much more than Lewis acid site, the acid strength and amount on ZSM-5 zeolite were different according to preparation conditions. GNJ had a kind of weak Bronsted acid site, GW had three kinds of Bronsted acid sites with different strengths, the weaker Bronsted acid sites were distributed inside and outside the channel and the stronger two kinds of Bronsted acid sites were mainly distributed inside the channel. GNX had two kinds of Bronsted acid sites of different strengths and distributed inside and outside the channel. Bronsted acid amount of GNX was more than the other two samples. It is recognized that the medium strong Bronsted acid was an essential for isobutene formation. Therefore, the ZSM-35 molecular sieve with appropriate suitable medium-strong Bronsted acid and distribution was beneficial to the n-butene isomerization reaction.

EFFECT OF CHELATING AGENT ON HDS SELECTIVITY OF CoMo CATALYST

2020, 51(8):  62-69. 

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A series of CoMo/ZSM-5-Al2O3 HDS catalysts was prepared with different chelating agents, such as citric acid, nitrilotriacetic acid, ethylene diamine tetraacetic acid and trans-1,2-cyclohexanediamine-N,N,N',N'-tetraacetic acid and characterized by FT-IR, H2-TPR, HRTEM, 27Al NMR and XPS techniques. The effect of the chelating agents on the HDS selectivity was investigated. The results showed that the agents preferentially complexed with Co and Al in the carrier and reduce the reduction temperature of metal components, improve the sulfurization degree of Mo, and increase the number of active center of the catalyst. The use of chelating agent increases the number of stacking layer and the length of MoS2 lamella. The number of stacking layer played a dominant role in promoting desulfurization, resulting in a greater increase in desulfurization activity of the modified catalyst than that in olefin saturation.

ACCESSIBILITY STUDY OF BRONSTED ACID SITE IN USY ZEOLITE

2020, 51(8):  70-75. 

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The accessibility of the Bronsted acid center of the USY is the key factor to catalytic cracking performance. The physical properties and structural parameters of USY and HY zeolites were investigated by in-situ infrared specrum technique using pyridine, 2, 6-dimethylpyridine, and 2,6-di-tert-butylpyridine as probe molecules. The MAT evaluation was conducted using Dagang light diesel fraction as feed. It was found that the accessibility of the Bronsted acid sites in the supercages of the USY zeolite to the larger-sized probes is significantly better than that of the conventional HY zeolite. It was concluded that lower Bronsted acid density is the main reason that USY zeolite showed superior Bronsted acid center accessibility in the cage. The MAT of USY zeolite was 69%, higher than that of conventional HY zeolite.

EFFECT OF IONIC LIQUID MODIFIED NANO-Fe3O4 AS ADDITIVE ON THE TRIBOLOGICAL PROPERTIES OF SILICONE GREASE

Xia Yanqiu An Bingyang

2020, 51(8):  76-80. 

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Different silicone greases were prepared with three different imidazolium hexafluorophosphate ionic liquids modified nano-Fe3O4 particles as additives. The volume resistivity of greases was measured by GEST-121 volume surface resistance tester．The effect of nano particle additives on the tribological properties of silicone grease was investigated by MTF-R4000 friction and wear tester. The surface morphology of the wear scar was observed by scanning electron microscope (SEM). The results showed that the nano-Fe3O4 modified by ionic liquid can further improve the tribological properties of lubricating grease and reduce the volume resistance. Its excellent tribological properties and low resistance are attributed to the interaction between the nano-Fe3O4 and the polarity of ionic liquid.

PREPARATION AND PROPERTIES OF ASPHALT MODIFIED BY HYDROTALCITE/WASTE CRUMB RUBBER COMPOSITE

2020, 51(8):  81-86. 

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Using Karamay No.90 asphalt as a matrix, the modified asphalts by hydrotalcite（LDHs）and waste crumb rubber composite were prepared. The effects of the amount of LDHs on the physical properties, anti-ultraviolet aging performance and rheological properties of the composite modified asphalt were investigated at constant waste crumb rubber amount. The results showed that when the content of waste crumb rubber was 15%, as the addition of LDHs increases, the softening point increased while the penetration and ductility of the composite modified asphalt decreased. It is demonstrated that the integration of two kinds of modifiers improves the physical properties of the composite modified asphalt, and met the requirements of national standard of polymer modified asphalt. Considering the cost of modifying agent, the mass fraction of LDHs added was 3%-4%. The addition of LDHs reduced the softening point increment and increased the residual penetration ratio and ductility retention of the composite modified asphalt, indicating that LDHs can significantly improve the UV aging resistance of the composite modified asphalt. The addition of LDHs can also increase the complex modulus and rutting factor of composite modified asphalt and decrease the phase angle, indicating that LDHs can improve the rutting resistance of composite modified asphalt.

SIMULATION AND OPTIMIZATION OF GAS FRACTIONATION COLUMN BASED ON ASPEN PLUS

2020, 51(8):  87-91. 

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Taking the No.2 gas fractionation unit with the capacity of 0.48 Mt/a of SINOPEC Yangzi Petrochemical Co. Ltd. as the research object，the Aspen Plus process simulation software was used to establish steady-state model of the gas fractionation unit. The simulation results were consistent with the actual production of the unit. Based on the above results，the sensitivity analysis tool was used to optimize the analysis of important operating parameters such as the top pressure and reflux ratio of the distillation column of the unit，with the goal of reducing energy consumption and maximizing propylene production，while ensuring the quality requirements of each product. The optimization results proved that under increasing the pressure at the top of the propylene rectification column and the propylene product quality，the propylene yield of the gas fractionation unit was improved. After optimization，the yield of propylene product increased by 0.08 percentage point，and the annual economic benefit was about 920 500 Yuan. The application of process simulation to optimize the production of propylene has a significant effect.

APPLICATION OF INTELLIGENT MONITORING SYSTEM FOR STEAM PIPLINE NETWORK

2020, 51(8):  92-97. 

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The intelligent steam pipeline network monitoring system can monitor the parameters of the steam pipeline network in real time and simulate the network by mathematical model. The monitoring system was applied to the medium pressure steam pipeline network of Sinochem Quanzhou Petrochemical Co.Ltd. The steam supply and inlet temperature of the turbine of the key unit were simulated under the two working conditions of -30 to 60 t/h and 30 to 90 t/h, which solved the problem of low inlet temperature of the turbine of some units. The method of adding new turbine to digest surplus steam and stabilize medium pressure pipeline network was put forward. It was recognized by simulation that the optimal position of the new turbine is near the FCC unit to realize energy saving optimization and safe and stable operation of the whole steam system.

COMPARISON OF TREATMENT TECHNOLOGIES FOR CYANIDE CONTAINING WASTEWATER FROM HEAVY OIL GASIFICATION

2020, 51(8):  98-103. 

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A large amount of cyanide containing wastewater was produced during the operation of POX unit of a refinery and affected the normal operation of the downstream wastewater treatment plant. Especially when processing high-nitrogen crude oil in atmospheric distillation unit, the amount of cyanide in the wastewater increased significantly, and the discharge of waste water exceeds the internal control index, which seriously restricted the crude oil purchase of the petro-chemical enterprise. In order to meet environmental requirements and remove the constraints for crude oil purchase, this paper introduced the advantages and disadvantages of three kinds of cyanide removal technologies: (i) catalytic oxidation and hydrolysis at high temperature and high pressure, (ii) elec-tro-catalytic oxidation, and (iii) chemical addition precipitation.

PREPARATION OF SUPERHYDROPHOBIC MATERIAL WITH HIGH OIL REMOVAL EFFICIENCY BY GRAFTING SiO₂ NPS ON PTFE SURFACE

2020, 51(8):  104-110. 

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Oil-water separation is one of the important processes in industrial production, and the demand for simple and environmental friendly oil-water separation and coalescence materials is increasing. In order to develop new superhydrophobic materials, nano silica was attached to the surface of polytetrafluoroethylene (PTFE) by using GMA as the intermediate. The results of XPS and SEM showed that nano silica was uniformly adhered to the surface of PTFE, resulting in a greatly increased surface roughness and a superhydrophobic layer. The oil removal experiment showed that the modified material had a good oil-water separation performance, good acid，alkali and salt-resistance, good stability and reusability. The materials used in the preparation of the new materials are from a wide range of sources and have good compatibility with other technologies, which have a broad application prospect in the oil-water separation industry.

ENERGY CONSUMPTION ANALYSIS AND OPTIMIZATION OF SINOALKY SULFURIC ACID ALKYLATION UNIT

2020, 51(8):  111-114. 

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The present situation of energy consumption of 0.20 Mt/a alkylation unit was introduced and the causes of high consumption of 1.0 MPa steam, circulating water and demineralized water were analyzed. Four measures were taken, such as cooling and decompressing operation in fractionators, stopping the acid, alkali and water washing process of reaction products, reduce anti-surge flow of refrigerating compressor, optimizing water service, resulting in reduction of 1.0 MPa steam consumption by 9 t/h, 3.5 MPa steam by 3 t/h, demineralized water by 7 t/h, electricity by 102.95 kW.h, and circulating wate by 340 t/h. According to the comprehensive calculation, comparing with the initial stage of operation, the energy consumption of unit reduced from 6 064.762 MJ/t to below 4 598 MJ/t. According to the actual situation of the unit, the measures, such as reusing of low temperature medium heat of process, and low temperature heat of condensate water, adding frequency conversion of machine pump, were put forward as the direction for further energy-saving of the unit.

THE STATUS OF SOLID ACID CATALYST ON OLIGOMERIZATION OF LIGHT OLEFINS

2020, 51(8):  115-120. 

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With the continuous optimization of China's refining process and gasoline pool composition, the conversion of C4 olefins into clean gasoline with high octane number by oligomerization reaction has been developed rapidly, with solid acid as most widely used catalyst. The source of raw materials and processing route of olefins were briefly introduced with the applications of various kinds of solid acid catalysts being summarized in this paper, mainly including solid phosphoric acid, acid resin, zeolite, clay, heteropoly acid, sulfonated metal oxide and metal/acid supported catalysts, etc. The mechanism of carbon ion reaction over solid acid catalyst was also summarized. It was found that among these catalysts, zeolites has the advantages of adjustable pore and acidity, easy regeneration, no pollution and high activity, which have more industrial application potentials in the future.