Table of Content

12 February 2024, Volume 55 Issue 2

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RESEARCH PROGRESS ON INTERFACE STRUCTURE REGULATION OF ELECTROLYTIC WATER CATALYSTS

2024, 55(2):  1-9. 

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With the advancement of carbon neutrality goalin China, the exploration and utilization of renewable energy has become a hot research topic, in which hydrogen production by electrolytic water as a green,large-scale production of H2 energy technology has attracted much attention.The process of water electrolysis mainly involves two half reactions, namely hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). At present, the efficiency of hydrogen production on a large scale is low, so the development of efficient catalysts to improve the efficiency of water electrolysis is the core to improve the efficiency of hydrogen production. High-efficiency electrocatalysts should have a large number of exposed active sites, high conductivity and long life.As the main site for catalytic reactions, the interface can be regulated to tailor the reaction path by adjusting the interfaceatomic arrangement and electronic structure. Interface engineering can modify the catalyst to obtain new physicochemical properties and excellent synergistic effects. Due to the increased density of active sites, the activity and stability of electrocatalysts can be greatly improved. Therefore, it is necessary to adjust the interface structure at the nanoscale to develop efficient electrocatalysts for water splitting.In this paper, three main interface structures and interface structure control strategies were reviewed, which could provide guide for interface structure control to enhance the electrocatalytic performance.

PROGRESS ON CATALYSTS FOR AMMONIA DECOMPOSITION

2024, 55(2):  10-22. 

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Hydrogen energy,as a clean and environmentally friendly renewable energy source,is attracting worldwide attention.However, the extremely low volume energy density andthe flammable and explosive characteristics of hydrogen bring difficulties and dangersto large-scale storage and transportation of hydrogen. Ammonia is a kind of carbon-free hydrogen carrier,which not only has high volume and mass energy density, but also has mature storage and transportation technology.On-site hydrogen productionfrom ammonia can solve the problems of hydrogen storage and transport, so ammonia hydrogen storage from ammoniais attracting a lot of attention. Currently, the most efficient catalyst for ammonia decomposition is ruthenium-based catalysts, but it can not be used in large scale because of its high price. Among the non-precious metal-based catalysts, Ni-based catalysts have the highest activity and relatively low cost,which are considered to have great application potential. However, Ru-based and Ni-based catalytic systems still havesome challenges in terms of activity and stability. In this paper,the latestresearch progress of ammonia decomposition catalysts, including catalysts based on Ru, catalysts based on non-precious metals Fe and Ni, and bimetallic catalysts, and the reaction mechanism of ammonia decompositionin recent literaturewere reviewed.

RESEARCH PROGRESS ON SULFUR AND PHOSPHORUS POISONING IN DIESEL VEHICLE EXHAUST OXIDATION CATALYSTS

2024, 55(2):  23-35. 

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Diesel vehicle exhaust oxidation catalyst (DOC) is an important part of diesel vehicle emission post-treatment system. Its main function is to effectively remove carbon monoxide (CO) and hydrocarbons (HC) caused by incomplete combustion, and oxidize a portion of nitric oxide (NO) to nitrogen dioxide (NO₂), which promotes the subsequent regeneration of diesel particulate filters (DPF) and ammonia selective catalytic reduction (NH₃-SCR) reactions. However, in practical operation, the DOC, which is located at the forefront of the entire after treatment system for diesel emission, inevitably suffers from sulfides and phosphates in diesel and lubricating oil, which affects the overall purification efficiency of the after treatment system. In this paper, the effects of sulfur and phosphorus on the catalytic performance of DOC, the mechanism of sulfur and phosphorus poisoning, and strategies for mitigating sulfur and phosphorus poisoning were reviewed in detail. In view of gap between scientific research and practical applications of DOC for sulfur and phosphorus poisoning, the development direction of DOC for sulfur and phosphorus poisoning in the future was prospected.

RESEARCH PROGRESS OF MOLECULAR SIEVE SKELETON ALUMINUM ATOM DISTRIBUTION

2024, 55(2):  36-42. 

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Molecular sieves have been widely used in acid-catalyzed reactions of petrochemical industrybecause of their variable acidic sites, good shape selectivity and hydrothermal stability. The distribution of acid sites is determined bythe position of aluminum atom in the molecular sieve framework, therefore, the distribution of skeleton aluminum atoms (including the porevolume, chemical environment of skeleton aluminum location, the distance between two aluminum atoms) has a great influence on its acidcatalytic performance (reaction pathway or reaction rate). Becausethe synthesis ofmolecular sieveinvolves a complex crystallization process,there are many factors affectingthe distribution of skeleton aluminum atoms, such as the kind and concentration of starting materials, crystallization conditions, introduction of heteroatoms, and post-treatment methods, etc. Many researchers have done a lot of research on regulation ofskeletonaluminum atoms. Based on this,the related research resultswere reviewed in order to promote theoriented synthesis of specific aluminum atom-distributed molecular sieves.

RESEARCH PROGRESS OF HETEROGENEOUS CATALYSTS FOR SELECTIVE HYDROGENATION OF FATTY ACIDS TO ALCOHOLS

2024, 55(2):  43-51. 

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Fatty alcoholsare important raw materials for the synthesis lubricants, detergents and surfactants. The oil hydrogenation method has become one of the most promising methods for the preparation of fatty alcohols due to its advantages of environmental friendliness and wide source of raw materials. The core of selective hydrogenation of oil to prepare fatty alcohols is high selectivity, and the catalyst is the keyto ensure high selectivity and reaction rate. Because the catalytic hydrodeoxygenation of natural oils or model compounds (such as fatty acids) will first generate extremely unstable intermediate fatty aldehydes, fatty aldehydes will be hydrogenated into stable fatty alcohols or decarbonylated to alkanes, and excessive hydrogenation of fatty alcohols will also generate growth chain alkanes, which requires the catalyst to have a weak adsorption capacity for the oxygen atoms of the carbonyl group in the fatty aldehyde and the hydroxyl group in the fatty alcohol.Based on this, the heterogeneous catalysts commonly used in oil hydrogenation were introduced from three aspects: active metal, metal promoter and carrier,and the mechanism of oil selective hydrogenation, and the methodsto improve the selectivity of fatty alcoholswere discussed. A new idea for the design of catalysts for preparationof fatty alcoholby oil selective hydrogenation was proposed.

RESEARCH PROGRESS ON TUNGSTEN-BASED CATALYSTS FOR SELECTIVE CONVERSION OF BIOMASS TO DIOLS

2024, 55(2):  52-63. 

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Diols, such as ethylene glycol and propylene glycol, are extensively utilized as fuels and chemicals across industries due to their high market demand. However, the conventional production of diols from petroleum derivatives poses significant drawbacks including reliance on non-renewable raw materials and substantial environmental pollution. Therefore, the utilization of biomass-based green pathways for diols production is conducive to promoting sustainable development. This study comprehensively reviewed the current research progress on tungsten-based catalysts employed in the chemoselective production of diols from biomass as well as its derivatives (including cellulose, glucose, and fructose) in recent years, and provided a detailed overview of the catalyst structure, the reaction pathway, reaction mechanism, and catalyst stability. Building upon this, it anticipated the trajectory of catalytic synthesis of diols from biomass feedstocks, aiming to provide valuable insights for researchers in the related field.

RESEARCH PROGRESS ON INTENSIFICATION OF GAS-LIQUID MASS TRANSFER IN CO2 CAPTURE PROCESS

2024, 55(2):  64-74. 

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Carbon dioxide（CO₂) capture is a bottom-up technology for achieving carbon neutrality. Chemical absorption is one of the most promising technologies for commercialization, and the intensification of gas-liquid mass transfer in the absorption process is an important factor affecting the efficiency, energy consumption and cost of CO₂ capture. For the new gas-liquid mass transfer intensification mode, the methods and research status of enhancing carbon dioxide absorption in recent years were summarized and reviewed from the aspects of microfluidic enhancement, introduction of additional energy field, introduction of the second-phase medium and micro-interfacial oscillation technology.The paper focused on the principle and research methodology of the micro-interfacial oscillation technology, and discussed the advantages and disadvantages of different enhancement means to provide reference for promoting the development of gas-liquid mass transfer enhancement incarbon capture process.

PROGRESS IN METHANOL SYNTHESIS BY CO₂ CATALYTIC HYDROGENATION

2024, 55(2):  75-83. 

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Thermal catalysis CO₂ hydrogenation to methanol has significant carbon reduction effect, can effectively store renewable energy, andhas broad prospects for industrial prospect. In this review, the reaction network for the CO₂ hydrogenation to methanol and thermodynamic challenges were introduced, and the process and its industrial applications at domestic and abroad were summarized. Then the research progress on the catalysts with different active components in recent years was reviewedfrom the aspects ofpreparation method, the active sites, reaction mechanism and kinetics in terms of problems and advantages. The structure-activity relationship ofcopper-based catalysts, including the effects of the active components, support and additives on the activity and methanol selectivity, was emphatically described. A prospect was finally presented for the catalyst development in the future.

RESEARCH PROGRESS OF CATALYSTS FOR DIRECT SYNTHESIS OF DIMETHYL CARBONATE FROM CO₂ AND METHANOL

2024, 55(2):  84-90. 

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The direct synthesis of green and environmentally-friendly intermediate dimethyl carbonate (DMC) from CO₂ and methanol not only meets the needs of green chemical development, but also makes the utilization of CO₂ as a resource. In order to turn the research scope to industrialization, the development of high-efficiency catalysts is the focus of DMC in the future. The research progress of DMC catalysts for direct synthesis of CO₂ and methanol was reviewed, and the reactivities of different types of catalysts were introduced, mainly including metal carbonate, metal oxide catalyst, supported catalyst, metal complex catalyst, ionic liquid catalyst, and electrosynthesis catalyst, which would provide a reference for the direct and efficient synthesis of DMC.

PROGRESS IN THE PREPARATION OF FENTON-LIKE CATALYTST MEMBRANES AND THEIR APPLICATION INORGANIC WASTEWATERTREATMENT

2024, 55(2):  91-100. 

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Fenton-like catalyst membranes have obvious advantages in the treatment of pollutants in wastewater, and are widely used in removal of dyes, oil, new pollutants and other fields. Based on this,the common types of Fenton-like catalyst membranes, including transition metal-based, carbon-based, composite and other novel catalyst membranes,were described. The preparationmethod of Fenton-like catalyst membrane was introduced,the mechanism of membrane filtration and oxidative degradationof organic pollutants in treatingwater by Fenton-like catalyst membrane system was analyzed, the application statusof Fenton-like catalyst membranes in typical organic wastewater was reviewed, and the challenges of Fenton-like catalyst membrane water treatment technology were put forward, which helped to promote the development and application of Fenton-like catalyst membranes in practical wastewater treatment.

RESEARCH STATUS AND PROSPECT OF EXTRACTIVE SEPARATION TECHNOLOGY OF RARE EARTH ELEMENTS

2024, 55(2):  101-109. 

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Petroleum refining and chemical catalysts are an important field of rare earth application. With the increasing demand for rare earth elements, obtaining large quantities of pure rare earth elements has become a challenge. In this paper, by combing the separation technologies such as precipitation, ion exchange, solvent extraction, membrane separation, adsorption and electrochemistry, the development of extraction and separation technology was summarized from the aspects of efficiency, selectivity, economy, environmental protection and sustainability, and the advantages and disadvantages of various process technologies were evaluated, finally, the development prospects of rare earth extractive separation technology were prospected.

RESEARCH PROGRESS ON RECYCLING TECHNOLOGY OF MOTHER LIQUID IN ZEOLITE SYNTHESIS

2024, 55(2):  110-114. 

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The recycling technology of mother liquid in the synthesis of zeolites is a new method for the preparationof zeolites, which can effectively improve the utilization rate of raw materials and reduce the discharge of waste liquid. In this article, the generation and composition of mother liquidof zeolitesynthesiswas introduced, the recycling technology of mother liquid of zeolite synthesisand its application in zeolite synthesis were briefly described, and the research progresses of this technology focused on the synthesis of the most representative zeolites including Y, ZSM-5, SAPO-34 as well as other zeolites were summarized. In addition, the challenges faced by the recycling technology of mother liquid of zeolitesynthesiswere also proposed.Based on this, the development direction of this technology in industrial production was envisioned. This research would provide reference for achieving the efficient and sustainable development of zeolite industry.

RESEARCH PROGRESS ON THE REGULATION OF GRANULAR DRY DESULFURIZER BY USING BINDERS AND PORE-FORMING AGENT

2024, 55(2):  115-120. 

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With the "carbon peaking" and "carbon neutrality" goal proposed, the enterprises have to pay more attention to the removal of sulfur dioxide. Due to the characteristics of low cost, simple preparation, high desulfurization performance and easy operation, the granular dry desulfurization process will become the trend of flue gas desulfurization in the future. Binder and pore-forming agent used in granular dry desulfurizer were introduced. Adding binder to the desulfurizer could increase the mechanical strength and desulfurization efficiency of desulfurizer and make desulfurizer difficult to pulverize. Adding pore-forming agent to desulfurizer could increase its specific surface area and porosity, thus increasing the contact chance between desulfurizer and sulfur dioxide, and improving the desulfurization efficiency. By adding binder and pore-forming agent to granular dry desulfurizer, the utilization rate of granular dry desulfurizer could be greatly improved, so the cost of desulfurization was reduced. In the future, it is the development trend to add cheap binder and pore-forming agent into granular dry desulfurizer to improve the mechanical strength and desulfurization efficiency of desulfurizers and reduce the cost.

RESEARCH PROGRESS ON CATALYTIC COMBUSTION CATALYSTS FOR LOW-CONCENTRATION METHANE FROM THE PERSPECTIVE OF INDUSTRIAL APPLICATION

2024, 55(2):  121-127. 

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Methane is a strong greenhouse gas with a short life span and rapid warming effect. Coal mining, which mainly consists of underground mining, makes coal mine methane become the main source of methane emission from energy activities in China. However, there is still no efficient method to utilize low-concentration methane. Catalytic combustion of methane can completely convert methane to carbon dioxide at a lower temperature, which is an efficient and environmentally friendly utilization method to use methane. Methane molecules have high structural stability, especially the catalytic combustion of low-concentration methane under mild conditions is more challenging. In this paper, based on the industrial application perspective, focusing on the requirements of actual working conditions for catalysts, the research progress in four aspects of catalyst activity, thermal stability, mechanical stability and anti-toxicity stability was overviewed, and the challenges in the application of methane-catalytic combustion catalysts and future development trend were analyzed. The purpose of this paper is to provide a reference for the development of catalytic combustion catalysts of ventilation air methane in coal mines for industrial applications.

DESIGN AND ENHANCEMENT OF GREEN AND ENERGY-SAVING EXTRACTIVE DISTILLATION PROCESS

2024, 55(2):  128-134. 

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Extractive distillation is a separation technique for multi-component azeotropes by adding new solvents, which can effectively extract and separate the target substance in the mixture. However, traditional extractive distillation processes have drawbacks such as low separation efficiency, high energy consumption, and severe environmental pollution. With the depletion of energy and the increasing emphasis on environmental protection, energy-saving and efficient separation of azeotropes is of great significance for the development and design of chemical processes. It is urgent to design an energy-saving and efficient enhanced extractive distillation process. Firstly, the design route of extractive distillation process was summarized, andthe important position of thermodynamic topology theory in process design was pointed out. Secondly, the application of process strengthening in distillation process design was studied. Thirdly, the selection method of extractants in extractive distillation was pointed out, and the application of relative volatility and molecular simulation in it was explained in detail. Finally, the methods for optimizing and designing extractive distillation process parameters were introduced, and the advantages and disadvantages of sequential iterative optimization and multi-objective optimization were discussed. This study provideda new idea and method for the design and enhancement of green and energy-saving extractive distillation processes, and provided reference for research and application in related fields.

FABRICATION, MODIFICATION AND PHOTOCATALYTIC APPLICATIONS OF BISMUTH FERRITE NANOMATERIALS

2024, 55(2):  135-143. 

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Bismuth ferrite has been considered to be one of the ideal materials for semiconductor photocatalysts due to its narrow band gap, high chemical stability, and excellent visible-light response. However, as a photocatalyst, bismuth ferrite always has some disadvantages, such as the low carrier efficiency and high photo-generated electron-hole pair recombination rate，which limits its practical application. Based on the basic properties of bismuth ferrite and photocatalytic mechanism, this review firstly introduced the common fabrication methods of bismuth ferrite. Subsequently, three modification strategies, including element doping, heterojunction construction and morphology control were elaborated. Finally, the photocatalytic applications of bismuth ferrite were summarized. Meanwhile, the future research focus and direction of bismuth ferrite-based photocatalysts were prospected.

DESIGNING Pt-Co-ZnO TERNARY INTERFACES FOR ENHANCED CO₂ HYDROGENATION PERFORMANCE THROUGH LATTICE MATCHING

2024, 55(2):  144-152. 

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Aiming at the difficuly of accurately constructing nanomultiple interface ofmulti-component solid catalysts, given the extremely high lattice match between hexagonal cobalt(II) oxide (hcp-CoO) and zinc oxide (ZnO)(>99.8%),the Pt-ZnO@CoO ternary catalyst was was designed and synthesized using lattice mathing strategy for targeted construction of ternary interface. The morphology, elemental distribution, phase structure, elemental content, reduction capability, and adsorption capacity of the catalystwere characterized by scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), inductively coupled plasma mass spectrometry (ICP-MS), hydrogen programmed temperature reduction (H₂-TPR) and carbon dioxide programmed temperature desorption (CO₂-TPD), then its catalytic performance for CO₂ hydrogenationwas evaluated in a fixed-bed reactor. The results showed that Co and Pt were highly dispersed on the surface ofPt-ZnO@CoO catalyst, and the precursors of CoO and Pt were reduced to nano-particles after reduction treatment. The Pt-ZnO@CoO catalyst exhibits excellent catalytic performance and stability for CO₂ hydrogenation, this is because of its high density of the interface sites, strong reduction ability and strong CO₂ adsorption capacity.

OPTIMIZATION OF PRODUCTION AND OPERATION PLAN OF REFINERYUNDER THE SITUATION OF “DUAL CARBON CONTROL”

2024, 55(2):  153-159. 

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With the steady progress of “dual-carbon” strategy in China, the new situation of shifting from “dual-control of energy consumption” to “dual-control of carbon emission” has put forward higher requirements for energy conservation and carbon reduction in the petrochemical industry. From the perspective of the key link of petrochemical industry chain-production, operation and planning optimization,this study exploreda newwayto reducecarbon emission by optimizing production schemewithout changing the existing production process and energy structureand increasing additional investment. By combining the carbon emissions from the production process of a refining-chemical integrated enterprise A and a fuel-based enterprise B, and innovating the calculation method of indirect emission factors, the carbon emissions from each set of units of the enterprisewas accurately calculated, the accuracy of carbon emissions measurement of refineries was advancedfrom the whole-plant level to the level of units. Furthermore,the carbon emissions of the plant was incorporated into the production planning optimization model, and the influence of carbon emissions of the plant onthe enterprise planning optimizationwas investigated, and it was found that there was a space for optimizing the carbon reduction of at least 3% under the conditions of no change in the crude oil processing volume and ethylene production, which provided practical solutions for carbon emission reduction of enterprises A and B in the actual production.

PREPARATION OF Ni/ZnO-Zn/ZSM-5 BIFUNCTIONAL COUPLING CATALYST AND COUPLED AROMATIZATION DURING REACTIVE ADSORPTIVE DESULPHURIZATION

2024, 55(2):  160-167. 

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In the process of fluid catalytic cracking(FCC) gasoline deep desulfurization,olefin saturation exists inthe traditional Ni/ZnO adsorbent, which results in the loss of octane number.In order to solve this problem, reactive adsorptive desulfurization coupling olefin aromatization reaction was attempted by introducing Zn-ZSM-5 into Ni/ZnO component.Bifunctional coupled Ni/ZnO-Zn/ZSM-5 catalyst was prepared by the equal volume impregnation method, the performances of coupling catalysts for desulfurization and olefin aromatization were evaluated, andthe effects of Ni content and Ni partition ratio on ZnO and Zn/ZSM-5 were investigated. The results showed that the catalyst hadthe best catalyticperformance at a reaction temperature of 450 ℃when the mass fraction of Ni content was 6% and theratio of NitoZnO and Zn/ZSM-5 was 1:1.The aromatics generation rate of 38.58% and the liquid yieldrate of 88.33%could be achieved.The operating temperature of the process was optimized and the regeneration performance of the catalyst was examined. At 420 ℃,the desulphurization rate, olefin conversion rate andaromatics generation rate of 6% Ni/ZnO-Zn/ZSM-5(1:1) catalyst were 98.7%, 54.0% and 29.7%, respectively, and the loss of octane number was reduced by 0.69 compared with that of the conventional Ni/ZnO desulphurization reaction. In addition, the process exhibited excellent desulfurization and aromatization performance in multiple regeneration cycles, demonstrating the feasibility of continuous processing.

RESEARCH ON THE ANTI-COKING PERFORMANCE OF La_0.75Sr_0.25MnO₃ PEROVSKITE COATING

2024, 55(2):  168-177. 

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In the process of producing ethylene through thermal cracking, it is difficult to avoid coking on the inner wall of furnace tube. Perovskite oxides have many advantages, such as rich chemical adsorption oxygen, flexible modification, high thermal stability and excellent oxidation/reduction performance, etc., it has been widely used in fields of environmental protection, thermochemical conversion, and synthesis of catalyst material and other fields. Inspired by the application of La_1-xSr_xMnO₃ perovskite material in the removal of hydrocarbons in the field of environmental protection, the plasma spraying method was used to prepare La_0.75Sr_0.25MnO₃ perovskite coating on stainless steel surface. The morphology, composition, and chemical structure of the perovskite coating and surface coke layer were investigated by means of scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results showed that the coating was dense, with a thickness of about 30 μm. The anti-coking performance of the coating was evaluated by pyrolysis coking test of naphtha. The coking experiment results showed that the inhibition rate of coking reached 70.4% and 64.8% respectively when the cracking time was 1 h and 3 h. After 6 cycles of coking/cleaning, the coking inhibition rate of the coating still reached to 35.6%. Moreover, the coating could maintain good structural stability at high temperature of 900 ℃, which could meet the demand of inhibiting coking in hydrocarbon pyrolysis.

CASE ANALYSIS OF ENERGY UTILIZATION OPTIMIZATION IN REFINERY

Wang Shiwen

2024, 55(2):  178-185. 

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Based on the practices and characteristics of energy consumption in refining and chemical enterprises, with the help of process simulation, benchmarking and big data analysis etc., CNOOC Ningbo Daxie Petrochemical Co., Ltd. conducted a study on optimizing the energy utilization of the entire plant. Improvement measures and optimization plans were proposed in terms of process analysis, heat exchange network, reasonable utilization of low-temperature heat, and energy utilization of steam cascade. In addition, the optimization of direct feed ratio of DCC unit raw materials and the circulation heat exchange integration at fractionating column overhead, including recovery and utilization of low-temperature waste heat in the ethylbenzene unit, and the optimization of the feed heat exchange network in the toluene column, and the application of steam jet pump technology in the extractive distillation units were carried out. The economic benefit is about 57.27 million yuan per year, and the energy saving of 36 ktCE/a (1 tCE=29.3 GJ) is realized by energy-saving optimization transformation. The carbon dioxide emission is reduced by 103 kt/a, and the low-temperature heat utilization ratio of the whole refinery is increased by 16.3%.

SYNTHESIS OF Co₂P NANOPLATES WITH DUAL-TEMPLATE METHOD AND THEIR CATALYTIC ACTIVITY FOR HYDROLYSIS OF AMMONIA BORANE

2024, 55(2):  186-192. 

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The development of a kind of catalyst with high activity and high selectivityunder mild conditions is the key to realize the application ofhydrolysis of ammonia borane(AB)for hydrogen production. Starting from the construction of P-doped materials, the catalyst with two different proportions of metal salts as the salt template and the transition non-precious metal Co²⁺ as the center metal was prepared. The Co₃O₄ precursor was prepared by cobalt acetate and ammonia water, and the Co₃O₄ precursor was mixed with NaH₂PO₄, NaCl and LiCl, and calcined in N₂ atmosphere to synthesize Co₂P-NaLi catalyst. After washing, the two salt templates were removed to obtain the final Co₂P-NaLi catalyst, which was a highly efficient catalyst that could react under mild conditions. The results showed that the catalytic activity of Co₂P-NaLi_0.15 catalyst was the highest when n(NaCl)∶n(LiCl)＝1:0.15, its initial conversion rate(TOF) was 31.2 min^-1at 298 K under light irradiation, and the activation energy (E_a)for the decomposition of ammonia borane on the catalyst was 60.8 kJ/mol. After 5 cycles, the catalytic still keep goodactivity, whichindicated that it had good stability.

EFFECT OF ORGANIC MOLYBDENUM AND POLYOL ESTER ON FRICTION PERFORMANCE OF POLYUREA GREASE FOR HUB BEARINGS

2024, 55(2):  193-199. 

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In order to further improve the tribological performance of polyurea greases for hub bearing of electric vehicles, a multi-functional friction and wear tester and a self-designed rolling bearing friction test-bed were used,the effects of organic molybdenum 855 and polyol ester 3970 on the tribological performance of commercial polyurea greases were investigated under pure sliding conditions and actual bearing operation conditions respectively, and the wear surface morphology and surface roughness of the test steel balls were characterized by microscope, scanning electron microscope, and 3D white-light interferometer. The results showed that the antifriction and anti-wear performance of commercial polyurea grease could not be improved byadding organic molybdenum 855 alone, but polyol ester 3970 alone and the combination of them could be used.In particular,the tribological performance of polyurea grease with (855+3970) could be significantly improved under various bearing operating conditions.The friction coefficient of polyurea grease with (855+3970) was reduced by more than 20%, and the largest decrease was38.8%.

LOW-TEMPERATURE EXTRACTION OF HELIUM FROM HELIUM-POOR NATURAL GAS BASED ON THE COUPLING OF MULTI-STAGE FLASH EVAPORATION AND MULTI-COLUMN DISTILLATION

2024, 55(2):  200-206. 

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Aiming at the engineering problem of helium extraction from low-grade helium-containing natural gas in China, based on the analysis of the development status and improvement direction of the existing deep-cooling process, to solve the problem of low helium purity and high energy consumption,a low-temperature helium extraction process by coupling multi-stage flash evaporation and multi-column distillation was proposed and simulated with ASPEN HYSYS. The results showed that the helium product with purity of 99% could be obtained by the proposed process from helium-poor natural gas with helium content of 0.05%. At the same time, 99.96% of methane and 99% of nitrogen, LNG and fuel gas were obtained, respectively, which enhanced the flexibility of the product scheme. The cooling capacity of the separation system was provided by throttling expansion refrigeration, and the reasonable matching heat transfer between the cold and hot materials in the process was realized. The unit compression power consumption of the multi-stage flash distillation + multi column distillation was 0.058 kW.h/kmol, which was much lower than that of the improved ExxonMobil helium extraction process (1.29 kW.h/kmol). It showed that the design of helium extraction process had a certain application potential.

SYNTHESIS AND PROPERTIES OF POLYARAMIDES MODIFIED WITH FLUORINE STRUCTURE

2024, 55(2):  207-212. 

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Firstly, a novel diamine monomer 9,9-bis (3, 5-dimethoxy-4-(4-amino-2-methylphenoxy) phenyl) containing fluorene was preparedby three-step organic reaction. This monomer was then used to synthesize a series of polyarylamides (PA 3a-3d) with fluorine by low-temperature solution condensation with four commercial aromatic diacids (terephthalic acid, 2, 2-bis (4-carboxyphenyl) hexafluoropropane,4, 4-diphenyl ether dicarboxylic acid, and 4-tert-butylisophthalic acid). The structure and properties of these polymers were characterized by ¹H NMR, FT-IR and GPC. The solubility, thermal properties, optical properties and mechanical properties of the polymers were investigated. The results showed that the polyarylamidescouldbe dissolved in high-boiling polar solvents such as DMAc, NMP, DMF, and pyridine and low-boiling point solvent THF. The glass-transition temperature T_g of these polymers ranged from 217℃ to 234℃. The 10% mass loss temperature in air and nitrogen were both above 450℃, indicating excellent thermal stability. The prepared films exhibited excellent mechanical properties, with tensile strength more than 76.6 MPa and elongation at break above 8.7%. These polymers with fluorene structures showed excellent comprehensive properties.