Table of Content

12 January 2021, Volume 52 Issue 1

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REVIEW AND APPLICATION PROSPECT ON DISTRIBUTED HYDROGEN PRODUCTION TECHNOLOGY

2021, 52(1):  1-9. 

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This paper expounds the necessity of developing distributed hydrogen production. The technologies using natural gas, methanol as raw materials as well as water electrolysis are reviewed for the development of the distributed hydrogen production. The prospects of technical economy, development and application of the technology are described. Suggestions for the development of distributed hydrogen production in our country are put forward. More attention should be paid to the development of renewable electricity electrolysis of water to produce hydrogen in the future.

RESEARCH PROGRESS OF IN-SITU OXIDATION BY HYDROGEN PEROXIDE GENERATED FROM HYDROGEN AND OXYGEN

2021, 52(1):  10-19. 

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H₂O₂ is an attractive alternative oxidant to the common industrial oxidants since it has high content of active oxygen and only water as by-product when it degrades. The direct synthesis of H₂O₂ from H₂ and O₂ is an environmental-friendly alternative route with high atom utilization efficiency compared with the current industrial process and is expected to replace the current traditional preparation processes and to realize the one-step integration of H₂O₂ generation in-situ and selective oxidation reaction. This paper discusses the recent progresses regarding the integration application of H₂O₂ direct synthesis process and oxidation reactions, like propylene epoxidation, Fenton reaction, methane oxidation and others, and aims to provide new research perspective for the in-situ oxidation reaction of H₂, O₂ and organic compounds systems through summarizing the exiting results and problems.

APPLICATION OF MAGNETIC SEPARATION TECHNOLOGY IN PETROLEUM AND CHEMICAL INDUSTRY

2021, 52(1):  20-26. 

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Magnetic separation technology, as an efficient separation technology, has the characteristics of large processing capacity, high efficiency, good selectivity and no secondary pollution in treatment processes. Based on the principle and technical characteristics of magnetic separation technology, the applications in petroleum and chemical industry are introduced in wastewater treatment, the separation of FCC catalysts and the separation of Fischer–Tropsch process catalysts. It shows that magnetic separation technology is effective in separating heavy metals, oils and fine suspended solids from waste water of petroleum and chemical industry. The process of separating and recovering FCC catalysts is simple with high economic benefit. After magnetic separation, the catalyst content in the liquid products of Fischer-Tropsch process is significantly reduced. It is pointed out that magnetic separation technology has a broad application prospect and that the recovery of magnetic seeds, the selection of magnetic matrice and the development of new magnetic separation equipments need to be focused on in the future.

NEW PROCESS FOR PYROLYSIS AND GASIFICATION OF LOW RANK COAL BY FLUIDIZED BED

2021, 52(1):  27-31. 

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Aiming at the problems encountered in fluidized bed pyrolysis and gasification, the heating mode of pyrolysis furnace, coal particle size grading, primary cooling and dust removal of pyrolysis gas, and ash discharging mode were discussed to optimize the process. In the new process, the high temperature semicoke was chosen to offer heat for pyrolysis furnace. The low rank coal feed was grinded into submillimeter particle size in which the fine powder smaller than 0.1 mm was separated out and delivered to the matched entraind flow bed gasifier to conduct the melting slag gasify together with the fine powder from fluidized bed gasifier to raise the carbon conversion rate. The major powder with particle size between 0.1-1.0 mm was fed into the pyrolysis furnace. The outlet gas from furnace contacted with proper cut fraction of tar oil to remove the tiny particles and then cooled down to 350 ℃ and further cooled by indirect heat transfer method. By this way the amount of organic wastewater could be lowered close to zero to realize clean and high efficiency pyrolysis and gasification. Taking the fluidized bed pyrolysis gasification process of low rank coal with a scale of 4 600 t/d as an example, the dry coal coarse powder entered the pyrolysis furnace, and the drying unit generated about 480 kt/a water. No organic wastewater was produced in the pyrolysis unit, but about 1.09×10⁹ m³/a hydrogen and about 81 kt/a coal tar were obtained. The carbon conversion rate of the system was up to over 95%，the yields of tar oil, coal gas, and semicoke reached 8.97%, 110 m³/t, and 67.5%, respectively and the volume fraction of effective gas in outlet gas of semicoke gasifier was more than 80%.

APPLICATION OPTIMIZATION OF HYDROUPGRADING TECHNOLOGY FOR INFERIOR FEEDSTOCK

2021, 52(1):  32-36. 

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The China Ⅵ standard compliant diesel fuel blending component was produced by hydro-upgrading two inferior raw oils. Under the same process conditions，the effect of the properties of the feedstocks on the distribution and properties of the hydro-upgraded products was investigated. The diesels from above two tests was mixed and used as raw material to investigate the effect of cut temperature for separation of light and heavy diesel on the properties of diesel density，composition, and cetane number. The results showed that the density，paraffin content，and cetane number of the light diesel and heavy diesel gradually increased with the increase of the cut point. The light diesel had a low cetane number and was a low-quality diesel blending component, and could be used as a raw material for catalytic cracking. The heavy diesel had a high cetane number，but with a high freezing point and needed to remove higher components further to become a high-quality No.0 China Ⅵ standard diesel blending component. In the case of above mixed diesel，at the conditions of cut point of 230℃and the freezing point at 0℃，the yield of heavy diesel components was the highest，and the cetane number could meet with the requirements of China Ⅵ standard.

OPERATION ANALYSIS OF REDUCING DIESEL/GASOLINE RATIO OF DIESEL HYDRO-UPGRADING UNIT

Xin Dingye Wu Xiaocan Qi Hongwei Feng Zhongwei

2021, 52(1):  37-42. 

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According to the requirements of the China VI oil product standard and reducing the diesel/gasoline ratio, PetroChina Karamay Petrochemical Company expanded and upgraded the existing 1.2 Mt/a diesel hydrogenation upgrading unit in May 2018. By a series of means such as adding a new reactor, revamping the fractionation system, adding an absorption stabilization system, and adjusting the catalyst gradation scheme, the processing scale of the unit was expanded from 1.2 Mt/a to 1.5 Mt/a. The full load calibration results showed that the naphtha yield was increased from 14.53% to 32.90%, the diesel yield was reduced from 46.80% to 39.43%, and the diesel/gasoline ratio of the unit was reduced from 3.22 before the modification to 1.20. It is proved that the new catalyst grading system exhibited excellent performance in hydrodesulfurization, denitrogenation, and flexible selectivity, which could meet the needs of oil quality upgrading and lower diesel/gasoline ratio in refineries.

COMPARISON OF AROMATICS EXTRACTION OPERATION CONDITIONS OF REFORMING DEPENTANIZER OIL AND HYDROTREATED PYROLYSIS GASOLINE AS FEEDS

2021, 52(1):  43-47. 

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The process of extracting aromatics from depentanizer oil and hydrotreated pyrolysis gasoline units, respectively, mixing the products and then distilling to produce benzene and toluene (named as two head and one tail process) was applied for two aromatics extraction units with 350 kt/a and 700 kt/a in CNOOC Huizhou Petrochemical Co. Ltd.. Based on the actual production data, the process design, raw material compositions, product comprehensive applications, product yields, unit energy consumption, and three reagents consumption for two raw materials were analyzed and compared. The problems in the operation of two sets of extraction units were summarized in order to provide reference for the production management of similar units.

COMMERCIAL TEST OF SULFUR TRANSFER BY CATALYTIC DISTILLATION-ALKYLATION DESULFURIZATION FOR FCC GASOLINE

2021, 52(1):  48-53. 

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The combination technology of catalytic distillation-sulfur transfer and hydrodesulfurization developed by PetroChina was commercially tested in Urumqi Petrochemical Company, and the test calibration was completed under the working conditions of two kinds of raw materials. The results showed that when a full-range FCC gasoline was used as feed, the sulfur concentration was 10.1 μg/g and 9.0 μg/g in the sulfur transferred light gasoline and the desulfurized heavy gasoline fraction, respectively; the sulfur content of blended full distillate gasoline was 9.5 μg/g with RON 88.7. When the etherified desulfurized heavy gasoline was employed as the raw fuel, the sulfur concentration was 11.1μg/g in the etherified light gasoline, 12.9 μg/g in the medium gasoline fraction and 11.4 μg/g in the desulfurized heavy gasoline; the sulfur content of blended full distillate gasoline was 11.7 μg/g with RON 90.2. By the catalytic distillation sulfur transfer technology for FCC gasoline, the cut temperature for separating light and heavy gasoline could be increased to 100-120 ℃. After the sulfur transfer, the sulfur content of the light gasoline is in line with the China V and Ⅵ standard gasoline blending components.

CALCULATION OF EFFECTIVE DIFFUSION COEFFICIENT OF GAS PHASE IN C₈ AROMATICS ISOMARIZATION CATALYST

2021, 52(1):  54-58. 

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A method for calculation of effective diffusion coefficient of gas phase was established. According to this method, the effective diffusion coefficients of the six gases such as xylene in C₈ aromatics isomerization catalyst under different reaction pressures and temperatures were estimated. The reliability of the method was verified and the effects of temperature and pressure on the molecular diffusion coefficient were discussed. The results showed that as the pressure increased, the gas density increased, the molecular distance shortened, the intermolecular force became larger, and the molecular diffusion coefficient decreased; while as the temperature was up, the molecular diffusion coefficient increased.

PREPARATION OF ACTIVATED CARBON FROM DWACTIVED RESIN CATALYST AND ITS APPLICATION IN ADSORPTION DESULFURIZATION FOR LPG

2021, 52(1):  59-65. 

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The low cost spherical activated carbon (KAC) was prepared by pretreatment, carbonization and KOH activation with deactivated MTBE resin catalyst as the precursor. The KAC prepared at the optimal KOH activation conditions of a base/carbon mass ratio of 4:1, an activation temperature of 800 ℃, and an activation time of 1 h, has a specific surface area of 2 769 m²/g with the total pore volume of 1.871 cm³/g. The Cu-KAC adsorbent was prepared by incipient impregnation method. The test showed that the adsorptive desulfurization performance of the adsorbent on LPG could be significantly improved by the modification of copper ions. The desulfurization performance of the adsorbent was the best when the load of copper ions was 10% and the adsorbent was calcinated at 400℃ for 2 h in N2.The results of methyl disulfide -TPD analysis showed that Cu-KAC adsorbent had stronger complexation adsorption capacity for DMDS than KAC. The regeneration performance of Cu-KAC adsorbent showed that the desulfurization rate of LPG could reach 60% after four times of regeneration at 400 ℃ for 2 h in N2.

EFFECT OF WATER ON CATALYTIC PERFORMANCE OF 3Si-5P-3Mg-ZSM-5 CATALYST FOR ALKYLATION OF TOLUENE WITH METHANOL

2021, 52(1):  66-71. 

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Para-xylene (PX) was synthesized through alkylation of toluene with methanol over composite modified ZSM-5 zeolite catalyst with a certain amount of steam introduced into the reaction. The influence of water vapor dosage on the conversion of toluene, PX selectivity and the stability of the catalyst was investigated. The fresh 3Si-5P-3Mg-ZSM-5 catalyst and the catalyst regenerated seven times were analyzed by XRD, N₂ physical absorption-desorption, NH₃-TPD, Py-FTIR, and ²⁷Al MAS NMR techniques. The results showed that toluene conversion, PX selectivity and anti-carbonization composite of modified 3Si-5P-3Mg-ZSM-5 catalyst were improved by introducing appropriate amount of water in the process of toluene alkylation with methanol. This could be attributed to the reduction of the content of strong acid center of the catalyst, the inhibition of the isomerization of p-xylene and the formation rate of the precursor of carbon deposition. When the mole ratio of water /(toluene＋methanol) was 10∶1, the conversion of toluene could be maintained at about 23% and the para-selectivity could be up to 74% within 50 h reaction time. The performance of regenerated 3Si-5P-3Mg-ZSM-5 catalyst showed that carbon deposition was the main cause of catalyst deactivation，no seriously damage of the framework structure and active components of the catalyst was found by adding steam. The catalyst could be restored to the level of fresh catalyst after repeated regeneration.

EFFECT OF Y AND BETA MOLECULAR SIEVES ON HYDROCRACKING OF NAPHTHENIC STRAIGHT-RUN DIESEL FRACTION

2021, 52(1):  72-78. 

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Using the modified Y, H-Beta molecular sieves and Y/H-Beta composite molecular sieves as acid components, respectively,the hydrocracking catalysts were prepared by equal volume impregnation method．The catalysts were characterized by XRD, BET, NH₃-TPD, Py-FTIR and H₂-TPR techniques. The results showed that compared with the catalysts prepared by Y molecular sieves and H-Beta molecular sieves, the catalyst prepared by modified Y/H-Beta compound molecular sieve has suitable acid amount and strength, and the active metals are uniformly dispersed, and the cracking and hydrogenation functions of the catalyst are reasonably matched. When the naphthenic straight-run diesel fraction was used as raw material, the composite catalyst could inhibite the secondary cracking obviously at high reaction temperature; and at higher conversion rate, the total liquid yield was the highest and the light naphtha yield was the lowest, while the yield of heavy naphtha was the highest, the potential aromatic of heavy naphtha and the cetane number of diesel fraction were both higher.

RESEARCH OF DENITRATION PERFORMANCE OF V₂O₅-MoO₃/TiO₂ CATALYST

2021, 52(1):  79-85. 

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A series of honeycomb V₂O₅-MoO₃/TiO₂  catalysts was prepared by extrusion molding. The effects of vanadium loading and molybdenum loading on the denitration activity of the catalysts and the performance of the catalysts against sulfur and alkali metal poisoning were tested. The physicochemical properties of fresh catalyst and sodium poisoned catalyst were analyzed by means of XRD, BET, SEM, H₂-TPR and XPS techniques. The results showed that when the vanadium loading (w) was in the range of 1.5%-2.5%, the denitration activity of the catalyst increased with the increase of vanadium loading. When the vanadium loading (w) was 1.5% and the molybdenum loading (w) was 4.0%, the catalyst had the best denitration performance. The poisoning effect of SO₂ on the V₂O₅-MoO₃/TiO₂ catalyst was reversible and could be recovered by heat treatment. When the Na₂O loading (w) was 2.0%, the catalyst was severely deactivated because the sodium salt agglomerated on the surface of the catalyst to form irregular white particles, covering the active site, resulting in a reduction of the catalyst surface area and poor redox performance. In addition, Na doping would affect the chemical state and surface composition of the active elements on the catalyst, reducing the ratio of V⁵⁺ and chemically adsorbed oxygen (O_α).

APPLICATION OF RG SERIES GUARD CATALYSTS IN HIGH ACID NAPHTHENIC VGO HYDROCRACKING UNIT

Zhao Chenxi Fang You Zeng Wenqin

2021, 52(1):  86-91. 

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The successful application of the RG series guard catalysts grading system in a high acid naphthenic VGO hydrocracking unit of CNOOC Huizhou Petrochemical Company Limited was introduced. The results of the operation for more than one year showed that the RG series guard catalyst system could remove and uptake the impurities, and effectively delay the rise of pressure difference of guard catalyst bed and total pressure difference of reactor. Besides, RG series catalysts exhibited certain refining activities, which shared a part of desulfurization and denitrogenation of the second fining catalyst bed and had a close function to the imported protective catalyst system. In summary, the industrial application results showed that the domestic grading guard catalyst could replace the imported protective agents, and be used with imported main catalysts of the hydrocracking unit.

INFLUENCE OF SAMPLE SOLVENT ON CHROMATOGRAPHIC DETERMINATION OF SULFIDE IN DIISOBUTYLENE AND ITS COUNTERMEASURES

2021, 52(1):  92-102. 

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The combination of gas chromatography (GC) and sulfur chemiluminescence detection (SCD) is a high effective method for analyzing sulfur compounds in hydrocarbon samples. A GC-SCD-FID combined instrument equipped with a PONA column was employed to determine sulfides in samples of synthesis diisobutylene (DIB). However, it was difficult to identify some SCD peaks due to solvent effects from DIB by the method. The influence of diisobutylene injection amount on the chromatographic peak properties of sulfide, disulfide and thiophene that may exist in petrochemical products was studied in detail. The retention time of sulfides without diisobutylene were predicted by sample dilution-extrapolation, and then confirmed by standard sample addition method. It was shown that the sulfide peaks appeared near the diisobutylene were greatly affected: The appearance time of diethyl sulfide peaks was 0.041 min earlier and the peak width increased by 2 times, the methyl tert-butyl sulfide retention time was prolonged by 0.443 min and the peak width increased by more than 9 times, the dimethyl disulfide peak time was prolonged by 0.377 min and the peak width was doubled, and the retention time of methyl sec-butyl sulfide was prolonged by 0.179 min. However, little effect on sulfide far away from the peak of solvent was found. Sulfides in diisobutylene samples identified by dilution-extrapolation method were mainly methyl tert-butyl sulfide, ethyl tert-butyl sulfide, di-tert-butyl sulfide, di-tert-butyl disulfide and other sulfides or disulfide containing isobutyl.

CHARACTERIZATION OF BASIC NITROGEN COMPOUNDS IN AROMATIC AND RESIN FRACTIONS IN VACCUM GAS OILS BY ION MOBILITY-TIME-OF-FLIGHT MASS SPECTROMETRY

2021, 52(1):  103-110. 

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Vacuum gas oil (VGO) samples were separated into saturates, aromatics and resin by column chromatography，then the basic nitrides in aromatics and resin fractions were characterized by electrospray ionization source (ESI) ion mobility-time-of-flight mass spectrometry (IMS-TOF MS), and the structural differences of the basic nitrides in VGOs from different sources were analyzed. The results showed that for VGO samples from different sources, even if the unsaturated degree of basic nitride was close, there were obvious differences in the connection mode of aromatic ring; however, for the aromatic components and resin of the same sample, the carbon number was similar, and the number of equivalent double bonds in resin was slightly lower. Taking the heteronuclear single quantum coherence test of NMR spectrometer and the evaluation of hydrodenitrogenation reaction as the auxiliary evidence, the relationship between the side chain length of aromatic ring of basic nitride in VGO and its removal difficulty was further speculated. Combining column chromatography with ESI IMS-TOF MS can solve the problem that samples with high wax content are difficult to dissolve, and weaken the ionization inhibition of strong polar components, thus obtaining more comprehensive mass spectrum information than direct injection.

PROCESS SIMULATION AND OPTIMIZATION FOR CONTINUOUS CATALYTIC REFORMING UNIT

2021, 52(1):  111-117. 

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Aspen HYSYS software was used to simulate the process of 700 kt/a continuous reforming unit in SINOPEC Luoyang Company. The ideal model which closed to the actual operation of the device was obtained. The model was used to optimize the operating parameters of the pre-hydrogenation fractionator (C101) and the heat exchange process of the reformate oil. The effects of reaction temperature on the octane number barrel of reformed gasoline, aromatics yield, hydrogen yield, and carbon deposition rate were simulated. After optimization, the content of C₅ component in the reformer feed decreased from 3.06% to 2.40%, the gas consumption of reboiler at the bottom of the C101 was reduced by 94 m³/h, the temperature of reformer depentanizer oil,supplied to aromatics extraction unit， increased from 70℃ to 95℃ by optimized heat exchange process， the 3.5 MPa steam consumption in downstream aromatics unit reduced by 2 t/h, and the fuel gas consumption of C201 reduced by 20 m³/h. Besides, two air-cooled devices at the top of C101 tower were shut down, saving 248 kW.h of electricity power. Combined with the coke burning capacity of the reformer, the suitable reaction temperature of the reformer was determined to be 520℃. Through the above optimization measures, the continuous reforming unit can increase the benefit by 13.58 million Yuan/a.

FAILURE ANALYSIS OF HIGH PRESSURE HEAT EXCHANGER OF HYDROTREATING UNIT AND STUDY ON CHANGE RULE OF AMMONIUM SALT CORROSION AND CRYSTALLIZATION TEMPERATURE

2021, 52(1):  118-125. 

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The failure cases of the E-104 tube bundles was analyzed and preliminarily judged that the system had corrosion under the ammonium salt scale. Then a simulation model of the reaction effluent system was established through software simulation. The risk of ammonium salt crystallization in the tube side and shell side of the failed heat exchanger was calculated. It was found that there was no risk of NH₄HS salt formation in the studied system. The ammonium salt crystallization temperature of the system increased slightly with the increase of the content of corrosive elements. The crystallization temperature of NH₄Cl in the hot high gas separation system in the original working condition and under new conditions were 177 ℃ and 181 ℃ respectively，and the NH₄Cl salt formation temperature of the cold low oil separation system were 178 ℃ and 182 ℃ respectively，which showed that under the original operating conditions，there was a risk of NH₄Cl crystallization in both the tube and shell side of E-104. Furthermore，the order of the factors affecting the crystallization temperature of NH₄Cl was determined as follows：content of Cl>content ofN >system gas flow rate>system operating pressure through the design of orthogonal experiments.What’s more，athree-dimensional map to predict the content change pattern was obtained，which will greatly improve the prediction efficiency of the NH4Cl salt temperature.

ANALYSIS OF HIGH COD IN WASTEWATER FROM FCC FLUE GAS DeSOx/DeNOx UNIT AND MEASURES

2021, 52(1):  126-130. 

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Aiming at the problem of high COD in the wastewater discharged from the RFCC unit of SINOPEC Hainan Refining and Chemical Co. Ltd., the factors such as the COD of the fresh water, the water replenishment of the washing tower, the SO₂ mass concentration in the flue gas at the outlet of the waste heat boiler, the C₅+ component volume fraction in the fuel gas, the operation conditions of the waste heat boiler, and the oxidation time of the waste water were analyzed, and the influence of the light gasoline of reforming on oxidation reactions of sulfite and hydrosulfite was investigated by adding it into RFCC slurry. Through comprehensive analysis, it is considered that the excessive SO₂ mass concentration in flue gas and the C₅+ hydrocarbons in wastewater inhibited the oxidation of sulfite and hydrosulfite, which are the reasons for high COD in wastewater. Measures such as reducing the ratio of Oman crude oil in processed crude oil, adjusting the reaction depth of residual oil hydrotreating unit to reduce the sulfur mass fraction in FCC feedstock to less than 0.4%, and controlling the volume fraction of C₅+ component in fuel gas not more than 0.5% were taken to ensure the stable discharge of COD in wastewater up to the standard.

PURIFICATION TEST OF ELECTRIC DESALTING WASTEWATER BY INORGANIC MEMBRANE

2021, 52(1):  131-135. 

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An inorganic membrane was used to treat electric desalting wastewater. The influence of operation parameters on membrane flux was investigated, and the cleaning and regeneration experiments were carried out. The results showed that the optimum operating parameters are temperature (T+15)℃, pressure (P+100) kPa and flow rate (V+1) m/s. After filtration, the removal rate of COD, suspended solids and oil in the sewage was 74.77%, 91.67% and 84.42%, respectively. The contents of ammonia nitrogen and volatile phenol were decreased, showing the obvious effect of purification. With the extension of filtration time, the membrane flux was decreased. The recovery rate of membrane flux was as high as 97.3% after cleaning with RYT-02 cleaner.