• Trend in development of carbon-one chemical technology under model of emission peak and neutrality of carbon dioxide

    LI Zhong;ZHANG Peng;MENG Fanhui;FU Tingjun;FAN Hui;State Key Laboratory of Clean and Efficient Coal Utilization, Taiyuan University of Technology;Technology Center, Sedin Engineering Co., Ltd.;

    The carbon-one chemical technology with the core of catalytic hydrogenation of CO, catalytic carbonylation and catalytic dehydration of methanol is a key technology of the modern coal chemical industry based on coal gasification. In the past decade, it has achieved great success in industrial application and has become the main way of clean and efficient utilization of coal. However, coal is not only a raw material, but also a fuel for the heat and power of the conversion process, which makes the carbon dioxide emissions in the modern coal chemical industry large and concentrated, with the characteristics of local strong emission. From the aspects of the low-carbon raw materials, the clean conversion of heat and power, innovation of thermal catalytic technology and catalysts, high selectivity of reaction products, and photo/electrocatalytic conversion technology of CO_2, the development trend and prospects of carbon-one chemical technology under the dual-carbon model of emission peak and neutrality of carbon dioxide were discussed. With the development of clean new energy large-scale and low-cost "green hydrogen" preparation technology, reverse water-gas shift reaction or electrocatalytic CO_2 reduction will be promoted to the "green CO" large-scale application. It will make a huge change in the carbon-one chemistry syngas feedstock, from the currently CO reverse water gas shift reaction to hydrogen by high-carbon fossil energy, to the CO_2 inverse water gas shift reaction by the new clean "green hydrogen". That is, the change of syngas from "CO+H_2" prepared by fossil energy sources towards "CO + green H_2" with low carbon emissions or "green CO + green H_2" withnegative carbon emissions, in order to achieve the goal of emission peak and neutrality of carbon dioxide. The adoption of renewable clean energy sources such as near-zero carbon emission photovoltaic and wind power to replace the existing coal-fired boilers in the carbon-one chemistry, as well as the adoption of new energy-saving and emission reduction measures and inter-industry technology coupling to reduce energy consumption through optimal design, are also effective measures to reduce CO_2 emissions to achieve emission peak and neutrality of carbon dioxide.

    2022 01 v.28;No.137 [PaperDigest][OnlineView][HTML全文][Download 5002K]
  • Effect of integrated process of coal pyrolysis and catalytic activated H_2 by coal ash on tar yield and quality

    ZHANG Juntao;LIU Jian;WANG Xian;TANG Ruiyuan;HUANG Chao;CAO Pengcheng;REN Zhaoyang;TIAN Yuanyu;College of Chemistry & Chemical Engineering,Xi′an Shiyou University;Oilfield Gas Chemical Technology Company of Shaanxi Yanchang Petroleum(Group)Co.,Ltd.;State Key Laboratory of Heavy Oil Processing,China University of Petroleum;

    The synergistic action of activated small molecules and catalysts can regulate the composition and distribution of coal pyrolysis products. An in-depth understanding of this process can help to realize the clean and efficient utilization of coal resources. The effects of the coupled reaction between catalytically activated H_2 and coal pyrolysis with coal ash and its main oxides of coal ash(such as Al_2O_3, Fe_2O_3, CaO, MgO, etc.)on coal pyrolysis products were studied in a two-stage fixed-bed reactor. The results show that when the activation temperature is 700 ℃ and the pyrolysis temperature is 600 ℃, the tar yield increases by 15.6% and 13.7%, respectively, compared with that before the addition of coal ash and Fe_2O_3, because the ·H generated by the catalytic activation of H_2 participates in the coal pyrolysis reaction. The results of GC-MS and simulated distillation analysis of tar show that the main components of coal ash(such as Al_2O_3, Fe_2O_3, CaO and MgO) are used as H_2 activation catalyst, only being conducive to the formation of aromatic hydrocarbons, phenols and lipids. When coal ash is used as H_2 activation catalyst, it is beneficial to the formation of ethers, lipids and aromatics in tar and can improve the content of light oil, phenolic oil and wash oil, which has a significant effect on the lightening of tar.

    2022 01 v.28;No.137 [PaperDigest][OnlineView][HTML全文][Download 33560K]
  • Research progress of mass spectrometry in molecular structure analysis of coal

    FAN Xing;XU Hao;Key Laboratory of Coal Clean Conversion & Chemical Engineering Process of Xinjiang Urumqi Autonomous Region, Xinjiang University;College of Chemical and Biological Engineering, Shandong University of Science and Technology;

    In order to realize the cleanliness of coal chemical production process, high-end target products and transformation of the industry under the goal of "double carbon", the endowment characteristics of coal molecules are used as the starting point to enhance the value of its fine conversion products. Mass spectrometry(MS) can clearly analyze the structural characteristics of coal molecules at the molecular level. This paper reviewed the research progress in coal molecules and mild conversion of coals using collision induced dissociation, a MS method. The progress of research related to the structure of coal molecules was reviewed. Determining the distribution of heteroatoms on aromatic nuclei and lipid chains allows the evaluation of the differences in reactivity of heteroatoms at different positions. The study of mass spectrometry methods in coal molecular structure profiling provides methodological guidance for understanding coal molecular structure units, monitoring heteroatom reaction pathways, and optimizing catalysts and reaction systems.

    2022 01 v.28;No.137 [PaperDigest][OnlineView][HTML全文][Download 11897K]
  • Research progress on alkali metal migration and detection during co-pyrolysis of coal and biomass

    BIE Nanxi;WANG Jiaofei;LYU Peng;BAI Yonghui;SONG Xudong;SU Weiguang;YU Guangsuo;State Key Laboratory of High-Efficiency Utilization of Coal and Green Chemical Engineering, Ningxia University;School of Chemistry and Chemical Engineering,Ningxia University;Institute of Clean Coal Technology, East China University of Science and Technology;

    Co-pyrolysis of coal and biomass is an important technology to realize the clean and efficient utilization of coal and biomass which can not only alleviate the contradiction between the increasing demand and the decreasing reserves of coal, but also solve the problems caused by low energy density, dispersion and seasonality of biomass. However, equipment corrosion caused by alkali metal volatilization seriously restricts the development of coal and biomass pyrolysis technology. In this paper, the influence factors, migration path, research methods and detection methods of alkali metal migration during the process of coal and biomass pyrolysis were reviewed. A review of domestic and international studies on the migration and transformation of alkali metals during the separate pyrolysis and co-pyrolysis of coal and biomass was presented to thoroughly analyze the migration mechanism of alkali metal during the process of coal and biomass pyrolysis. The effects of pyrolysis temperature, thermal conversion atmosphere, heating rate and raw materials on the migration of alkali metals during the process of co-pyrolysis, the gas-phase release and solid-phase transformation of alkali metals during the process of co-pyrolysis, the research progress of research methods and detection methods of alkali metals were summarized. The further research on the in-situ detection of alkali metals volatilization during co-pyrolysis of coal and biomass was prospected.

    2022 01 v.28;No.137 [PaperDigest][OnlineView][HTML全文][Download 14863K]
  • Research progress on solid sorbents for CO_2 capture

    JIANG Tao;WEI Xiaojuan;WANG Shengping;MA Xinbin;School of Chemical Engineering and Technology,Tianjin University;Key Laboratory for Green Chemical Technology,Tianjin university;

    Carbon dioxide, one of the main components of greenhouse gases, increased rapidly because of the growing use of fossil fuels. Excessive emissions of greenhouse gases have accelerated global warming and climate change since the humanity entered the industrial society.Carbon capture, utilization and storage(CCUS) technology has received a great deal of attention as an effective way to reduce CO_2 emission. Among all the ways to reduce carbon dioxide emissions, adsorption methods exhibit excellent prospect to achieve the CO_2 separation and removal. Solid adsorption materials are considered to be the ideal CO_2 capture materials because they have the advantages of wide operating temperature range, less corrosion to the devices, less waste produced in the recycling process, and the used adsorbent easy to manage. The research progresses of three types of CO_2 sorbents were reviewed, including low temperature, medium temperature and high temperature sorbents. And the advantages, limitations and methods on enhancing the CO_2 capture performance and cyclic stability of various solid sorbents were pointed out. Low temperature sorbents exhibit superior sorption capability but low selectivity under high pressure. And the moisture in the gas stream may hydrolyze the coordination bonds of the sorbents and compete with CO_2 for adsorption, leading to a decrease in CO_2 adsorption performance. Thus, the adsorption capacity, adsorption selectivity, and hydrothermal stability of low temperature sorbents are the focus of their research. Among the medium temperature solid adsorbents, hydrotalcite-like materials are challenged by their hydrogen-bonded stacked structure which limits further increase in adsorption capacity. And the main challenge to the practical application of MgO sorbents for CO_2 capture lies in their quite low CO_2 capture capacity and poor sorption kinetics, due to the barren basic active sites and intrinsically high lattice enthalpy. Therefore, improvement of the adsorption capacity and cycling stability has become a priority of medium temperature sorbents to be addressed. As for high temperature sorbents, Li_4SiO_4 adsorbents have lower preparation costs and higher adsorption capacities than that of the Li_2ZrO_3 adsorbents, Nevertheless, both of them face the problem of kinetic limitations. CaO-based sorbents have received tremendous attention due to their high theoretical capture capacity, wide availability, low cost, non-toxicity and fast adsorption kinetics. However, thermal deactivation in activity caused by sintering and attrition of the sorbent particles are identified as the primary challenges with CaO-based sorbents, in the multi-cycle process of CO_2 adsorption/desorption. And several modification methods have been utilized to fabricate high-performance CaO-based sorbents, such as high-temperature pretreatment, hydration, chemical doping, acid modification. Moreover, the development of granulation techniques and the scale-up production are quite urgent for realistic large-scale applications.

    2022 01 v.28;No.137 [PaperDigest][OnlineView][HTML全文][Download 4924K]
  • Research progress on CO_2 capture by synthesizing zeolite from coal-based solid waste

    ZHU Tao;YUAN Bo;HAO Weixiang;HAN Yiwei;LIU Shuai;LIU Yatao;SONG Huiping;Institute of Atmospheric Environmental Management and Pollution Control,China University of Mining & Technology-Beijing;Institute of Resources and Environmental Engineering,Shanxi University;

    The burning of coal emits a lot of carbon dioxide into the atmosphere, causing great environmental pollution. Solid adsorption method can effectively capture CO_2 gas with the advantages of low cost, easy operation and high recovery rate, which is the main technology for removing CO_2 in terminal treatment. Coal-based solid waste can be used to prepare zeolite adsorbents for CO_2 capture. That not only effectively alleviates the environmental pollution caused by coal-based solid waste, but also achieves the goal of carbon emission reduction. The research progress of CO_2 capture by synthesizing zeolite molecular sieve from coal-based solid waste was summarized. Firstly, the research status, advantages and disadvantages of coal-based solid waste synthesis zeolite molecular sieve technology were introduced. Then, the CO_2 capture effect of coal-based solid waste zeolite molecular sieve was briefly described, the factors affecting the CO_2 capture performance of coal-based solid waste zeolite molecular sieve were described, and the path to improve the CO_2 capture effect of coal-based solid waste zeolite molecular sieve was proposed. Finally, the current challenges of CO_2 capture technology with coal-based solid waste zeolite molecular sieve were summarized, and the future development direction of this field was forecasted.

    2022 01 v.28;No.137 [PaperDigest][OnlineView][HTML全文][Download 18598K]
  • Influence of the preparation method of copper-zinc-aluminum catalyst on the performance of carbon dioxide CO_2 hydrogenation reaction

    REN Chao;XU Bo;WANG Anjie;LIU Yingya;SUN Zhichao;WANG Yao;School of Chemical Engineering,Dalian University of Technology;

    A series of copper-zinc-aluminum catalysts were prepared by sol-gel method and co-precipitation method, which were used in combination with ZSM-5 molecular sieve to catalyze hydrogenation of CO_2 to light olefins. The prepared catalysts were characterized by means of N_2 physical adsorption, X-ray diffraction(XRD), and hydrogen temperature-programmed reduction(H_2-TPR). The performance of the catalysts prepared by two different methods were comparatively investigated in CO_2 hydrogenation to produce light olefins. The results show that different catalyst preparation methods significantly affect the CuO particle size, specific surface area and Cu component dispersion of the prepared catalysts, which in turn affects the performance of CO_2 hydrogenation reaction. In this system, the copper-zinc-aluminum catalyst has a great influence on CO_2 conversion rate and CO selectivity, but has little effect on the selectivity of light olefins in hydrocarbons. The catalyst prepared by the sol-gel method with the aid of citric acid complexation affords 20.17% CO_2 conversion with a total selectivity to light olefins of 50.48% at 320 ℃, CO_2∶H_2=1∶3, and space velocity of 3 600 mL/(g·h), whereas the catalyst prepared by the co-precipitation method with sodium carbonate gives 29.14% CO_2 conversion with a total selectivity to light olefins of 54.57%.

    2022 01 v.28;No.137 [PaperDigest][OnlineView][HTML全文][Download 7787K]
  • Research progress of integrated coal gasification fuel cell combined power generation (IGFC) technology

    WANG Qi;YANG Zhibin;LI Chufu;LEI Ze;LIU Shuqin;School of Chemistry and Environmental Engineering, China University of Mining and Technology-Beijing;National Institute of Clean-and-Low-Carbon Energy;

    Integrated coal gasification fuel cell combined power generation technology(IGFC), whose power efficiency can exceed 60% without considering cogeneration, is a new clean and efficient power generation technology of coal-based. Moreover, it can effectively control the emission of pollutants, create conditions for the capture and recovery of CO_2, and realize near zero emission of CO_2. IGFC system is generally composed of coal gasification & purification, fuel cell power generation, waste heat recovery, CO_2 capture and storage and other subsystems. Fuel cell power generation technology is the key technology that restricts the development of IGFC. Solid oxide fuel cell(SOFC) and molten carbonate fuel cell(MCFC) are both of the fuel cell technologies suitable for IGFC system. SOFC has more advantages in cost of production and power generation efficiency. In 2017, China Energy Group, together with China University of mining and Technology-Beijing, National Institute of Clean-and-Low-Carbon Energy, China Huaneng Group Clean Energy Research Institute and Tsinghua University, undertook the National Key R&D Program of China, which includes the development of 100 kW SOFC and MCFC power generation units, and the building of MW_(th) IGFC demonstration project with near zero CO_2 emission. The project achievements have promoted the pace of China′s IGFC system from basic technology R&D to industrialization.

    2022 01 v.28;No.137 [PaperDigest][OnlineView][HTML全文][Download 8260K]
  • Analysis on the technology development status of coal-based needle coke in China

    CHENG Junxia;ZHAO Xuefei;ZHU Yaming;LAI Shiquan;GAO Lijuan;College of Chemical Engineering,University of Science and Technology Liaoning;

    The development of coal-measure needle coke in China originated in the 1980 s. Now, the production of coal-measure needle coke has begun to take shape through decades of continuous efforts of relevant workers. The three main development stages of coal-measure needle coke preparation technology in our country were reviewed and summarized: technology development in laboratory and initial industrialization stage, the breakthrough of technical barriers of coal-measure needle coke industrialization and dream-realization localization stage, and the in-depth development stage of coal-measure needle coke technology. Meanwhile, the research focus and development direction of coal-measure needle coke technology in each development stage were introduced in detail. Current production technology process of coal-measure needle coke production companies in our country have been discussed and analyzed according to the pretreatment unit, delayed coking unit and calcination unit, respectively. In the pretreatment unit, three kinds of unique pretreatment technology have been developed based on the solvent extraction method. Overall, the raw material pretreatment operation with high refined pitch yield and ideal QI removal effect has been realized. There are two different process technologies(zero cycle ratio process and adjustable cycle ratio process) on the delayed coking unit during the industrial production of needle coke. Where, the fundamental difference is that the materials entering the coke tower are different, and the difference in the specific operation process was that the operation mode of zero cycle ratio process is constant temperature, variable pressure and short coke generation cycle. While the operation mode of adjustable cycle ratio process is variable temperature, variable pressure, and long coke generation cycle. Most coal-measure needle coke production enterprises choose the adjustable cycle ratio technology. Moreover, the calcination unit is major in rotary kiln calcination process and supplemented by the tank furnace calcination process. The former has a short processing cycle and ideal production capacity, but has large carbon burning loss, low yield, and is not friendly to the calcination of green needle coke containing more powders. Therefore, the calcination technology of tank furnace has been attracted a lot of attention again in the past two years. Based on the analysis of the current situation of domestic coal-measure needle coke technology, the existing situation of poor quality and serious "homogenization" of coal-measure needle coke products should be broken. The technical foundation research and continuous improvement of production process were emphasized to pay more attention according to the current situation of the coal-measure needle coke industry in our country. Which is favourable to improve the quality of China′s coal-based needle coke products and enhance the international competitiveness. Furthermore, the trend of industrial technology development of coal-based needle coke in the future was suggested as follows: through the development of two-stage coking process, the advanced production technology with simple operation, less human intervention, high process parameter control precision, friendly environment and high added value of by-products will be realized. On this basis, the strategic objectives of product quality "high-end quality" and the performance satisfaction "application differentiation" will be achieved to promote the orderly development of China′s coal-measure needle coke industry.

    2022 01 v.28;No.137 [PaperDigest][OnlineView][HTML全文][Download 19104K]
  • Advances in the modification of coal-based porous carbon for supercapacitors

    WU Xiaoyan;QIN Zhihong;YANG Xiaoqin;LIN Zhe;School of Chemical Engineering and Technology,China University of Mining and Technology;

    Coal is a promising carbonaceous precursor for high-quality porous carbon because of its high carbon content, abundant reserves and low price. The preparation of porous electrode materials for supercapacitors from coal is one of the important routes to realize the high value-added utilization of coal. The results show that the electrochemical properties of coal-based porous carbon electrode materials can be effectively improved by adjusting the pore structure and improving the surface chemical activity. The pore size distribution can be adjusted by three methods: physical and chemical co-activation, template method combined with chemical activation and combination of different chemical activators. The combined physical activation and chemical activation method mainly uses water vapor or CO_2 to assist the activation process of KOH, so as to obtain a large number of micropores and a certain amount of mesoporous pores, and realize the synergistic control of the pore structure and wettability of coal-based porous carbon. The combination of template method and chemical activation can obtain the same pore structure as template agent, and at the same time, KOH activation can further produce abundant micropores, thus achieving reasonable pore size distribution. In addition to using template agent, a large number of impurities contained in the carbon precursor can also be used as self-template. The adjustment of pore structure can also be realized by combining different chemical activators. For example, different pore size distribution can be obtained by combining K~+ and Na~+ ions with different ionic sizes. Using the fluidity of KCl at high temperature, the intermediate products of KOH can be carried to a wider and deeper extent, so as to realize the transformation from microporous to mesoporous. The surface chemical activity can be improved in 2 ways: by the pre-oxidation of carbon precursors and the introduction of heteroatoms. If the raw coal is pretreated by strong acid or strong oxidant, the organic oxygen content of the prepared carbon material can be increased, the active sites are increased and the wettability is improved. Heteroatoms can be introduced into carbon materials by dopant doping, the most applied of which is N doping. The introduced nitrogen-containing structures mainly include pyrro-N(N-5), pyridin-N(N-6), Quaternary N(N-Q), and pyridine-N-oxide(N-X). In addition, O, B, S and P are the common doped heteroatoms. Another way to introduce heteroatoms is through co-carbonization of coal with biomass, in which biomass acts as both carbon and heteroatom source. The wettability, electrical conductivity and structural stability of carbon materials can be improved by doping heteroatoms, and a certain amount of pseudocapacitance can be produced. In this paper, the research progress of coal-based porous carbon electrode materials in recent years was reviewed from the above aspects, the advantages and disadvantages of different modification methods were analyzed, the existing problems were discussed, and the future research trend of coal-based porous carbon for supercapacitors was prospected.

    2022 01 v.28;No.137 [PaperDigest][OnlineView][HTML全文][Download 8210K]
  • Composition analysis and biological toxicity evaluation of coal pyrolysis wastewater

    GAI Hengjun;PANG Xinran;FENG Bingxiao;WANG Zhendong;XIAO Meng;School of Chemical Engineering,Qingdao University of Science and Technology;

    In order to improve the biodegradability of coal pyrolysis wastewater and ensure the stable operation of biochemical device, it is necessary to clarify the toxicity source of wastewater and evaluate the toxicity reduction performance of pretreatment process. In this paper, the pollutants were classified by trioctylamine extraction combined with macroporous resin fractional adsorption to overcome the analysis problems of peak area overlap and large difference. Then the toxicity of the analyzed pollutants was evaluated by luminescent bacteria method, and the key pollutants in wastewater were determined. Finally, the reduction of biological toxicity, chemical oxygen demand, total phenol content and key pollutant content of wastewater treated by four conventional liquid-liquid systems were evaluated to provide theoretical support for the improvement of pretreatment process. The results show that phenols are the most important pollutants contributing to the biological toxicity of coal pyrolysis wastewater, and p-cresol is the most toxic. The type, position and number of substituents on the benzene ring of phenolic compounds have a significant impact on biological toxicity. Heterocyclic compounds have more residues in biochemical effluent and contribute greatly to the toxicity of wastewater. The toxicity reduction rates of four conventional extractants to wastewater are butyl acetate(96.6%), methyl isobutyl ketone(95.1%), isopropyl ether(92.4%) and trioctylamine(79.5%). The reduction rate of total phenol content in the wastewater after trioctylamine extraction is the highest, but the reduction rate of chemical oxygen demand and biological toxicity is the lowest. It indicates that the complex extractant is not suitable for the treatment of complex phenol containing wastewater. Butyl acetate and methyl isobutyl ketone can widely remove various key pollutants, so the reduction rate of chemical oxygen demand and toxicity is high, which is suitable for the extraction treatment of pyrolysis wastewater.

    2022 01 v.28;No.137 [PaperDigest][OnlineView][HTML全文][Download 2346K]
  • Progress in the synthesis of degradable polyglycolic acid from coal via syngas

    YE Linmin;HUANG Lele;DUAN Xinping;YUAN Youzhu;XIE Suyuan;College of Chemistry and Chemical Engineering,Xiamen University;State Key Lab of Physical Chemistry of Solid Surfaces,Xiamen University;National Engineering Lab for Green Chemical Productions of Alcohols-Ethers-Esters,Xiamen University;Tan Kah Kee Innovation Laboratory of Fujian Province, Xiamen University;

    Since 2009, the coal-to-ethylene glycol technology via syngas has been rapidly expanded in China, and the total production capacity of ethylene glycol is estimated to reach 13.68 Mt/a by 2022. The increasing maturity of coal-to-ethylene glycol technology further drives the technical progress of biodegradable plastic polyglycolic acid from coal via syngas, that is, dimethyl oxalate in the coal-to-ethylene glycol technology is selectively hydrogenated to methyl glycolate, and then the methyl glycolate is polymerized to degradable plastic polyglycolic acid. Polyglycolic acid is not only positioned as a high-end product in the polyester industry, but also used to produce fully degradable polyester products. It is a new material that has great market demand potential and space, encouraged by countries and regions where the "plastic limit order" is implemented. Thus, the R & D of the branch technology of degradable polyglycolic acid from coal via syngas is of great significance to enrich the product structure of the coal-to-ethylene glycol industry. Focusing on the R & D progress of degradable polyglycolic acid from coal via syngas, this review discussed the technical principle of hydrogenation of dimethyl oxalate to methyl glycolate monomer and polymerization of methyl glycolate to polyglycolic acid, as well as the engineering design and feasibility of this technical route. For the synthesis of methyl glycolate monomer, the key technology to achieve high conversion of dimethyl oxalate and high selectivity of methyl glycolate lies in designing and adjusting the composition and structure of the catalyst and optimizing the reaction conditions. For the preparation of polyglycolic acid from methyl glycolate, there are two main techniques: direct polycondensation method with methyl glycolate or glycolic acid as raw material and ring-opening polymerization method with glycolide as raw material. The quality of polyglycolic acid products can be significantly affected by different polymerization processes: low molecular weight polyglycolic acid can be produced by direct polycondensation and high molecular weight polyglycolic acid can be produced by ring opening polymerization. The development of degradable polyglycolic acid technology from coal via syngas will be conducive to the development and expansion of China′s coal-to-ethylene glycol technology.

    2022 01 v.28;No.137 [PaperDigest][OnlineView][HTML全文][Download 14071K]
  • Synthesis of dimethyl carbonate by urea alcoholysis using propylene glycol as a circulating agent in a reactive distillation column

    AN Hualiang;QU Yaqi;LIU Zhen;ZHAO Xinqiang;WANG Yanji;School of Chemical Engineering and Technology,Hebei University of Technology;Hebei Provincial Key Lab of Green Chemical Technology and High Efficient Energy Saving,Hebei University of Technology;

    Synthesis of dimethyl carbonate via urea and methanol is an important extension of the coal chemical industry chain, which can increase the added value of the coal chemical products. In this paper, propylene glycol was used as a circulating agent to intensify this reaction process. First, the two reactions, urea reacting with propylene glycol to propylene carbonate catalyzed by Zn-Al oxide and transesterification of propylene carbonate with methanol to dimethyl carbonate over Ca-Al oxide, were investigated in a reactive distillation column. The highest yields of propylene carbonate and dimethyl carbonate were 82.4% and 98.1%,respectively. Based on these experimental results, the catalytic distillation process of urea alcoholysis to dimethyl carbonate intensified by a circulating agent propylene glycol was realized, and the influence of reaction conditions was studied. Under the reaction conditions of a feed molar ratio of urea to methanol of 17,and a liquid hourly space velocity of the raw mixture of 0.5 h~(-1),the dimethyl carbonate yield reaches the highest of 58.2%.

    2022 01 v.28;No.137 [PaperDigest][OnlineView][HTML全文][Download 5656K]
  • Process flow simulation of methanol to aromatics and optimization of heat exchange network

    CHEN Shiyao;SHEN Jun;WANG Yugao;LIU Gang;NIU Yanxia;SHENG Qingtao;College of Chemistry and Chemical Engineering, Taiyuan University of Technology;

    As important basic chemical materials, benzene, toluene and xylene are currently mainly derived from petroleum cracking. China is rich in coal and less in oil with an overcapacity of coal-based methanol. Therefore, it is necessary to develop coal-based methanol to aromatics(MTA) production technology and to save energy and reduce CO_2 emissions. The MTA process flow was divided into four parts, namely methanol aromatization unit, aromatics/non-aromatics separation unit, aromatics separation unit and non-aromatics separation unit. Different physical property methods were selected for each unit according to different materials and operating conditions, namely PRMHV2, UNIFAC, SRK, PENG-NOB. The kinetic parameters were modified, so that the simulation results were basically consistent with the experimental results. On this basis, the MTA process was simulated by Aspen Plus. Sensitivity analysis was used to optimize the reactor, the extractive distillation tower and the toluene purification and rectification tower. Pressure swing rectification and complete thermal coupling rectification were used to carry out energy-saving transformation of the process. At last, the Aspen Energy Analyzer was used to optimize the heat exchange network of the process. The results show that the optimal reaction temperature of the reactor is 470 ℃, the catalyst dosage is 7 000 kg, the optimum extractant dosage of the extractive distillation column is 10 000 kg/h, and the number of trays of the toluene purification and rectification column is 59, the feed position is 29, and the reflux ratio is 3. After the energy-saving renovation, the pressure swing rectification saves 43% of energy and reduces CO_2 emission by 227.3 kg/h; the completely thermally coupled rectification saves 56.26% of energy, reduces CO_2 emission by 185.5 kg/h. After the optimization of the heat exchange network, the MTA process saves 52.82% of energy, namely 36.34 MW, and reduces 64.40% of CO_2 emissions, namely 6 282 kg/h. The final simulated main products are benzene, toluene, xylene with purity of 97.89%, 99.99% and 99.99% respectively, and output of 397.28, 2 772.81 and 5 486.49 kg/h, respectively. The use of chemical process simulation software to optimize the operating conditions and energy-saving transformation of the MTA process provides a reference for the realization of the industrialization of the MTA process, and meets the requirements of energy conservation and emission reduction in China.

    2022 01 v.28;No.137 [PaperDigest][OnlineView][HTML全文][Download 23070K]
  • Technical progress and industrialization status on the separation and purification of 2-methylnaphthalene from coal tar

    HU Fating;MAO Xuefeng;LI Junfang;ZHAO Peng;LIU Min;Beijing Research Institute of Coal Chemistry,CCTEG China Coal Research Institute;State Key Laboratory of Coal Mining and Clean Utilization;National Energy Technology and Equipment Laboratory of Coal Utilization and Emission Control;

    2-Methylanaphthalene is an important organic chemical raw material with a wide application range. With the rapid development of fine chemical industry, separating 2-methyl naphthalene from washing oil has received attention. From the perspective of oil washing processing, the technical characteristics of various separation and purification 2-methylnaphthalene techniques from wash oil were discussed. The industrial status and technological characteristics of 2-methylnaphthalene production at home and abroad were introduced, and the development direction of 2-methylnaphthalene separation and purification technologies and industrialization were prospected. Wash oil′s components form many azeotrope and eutectic mixture. It is difficult to separate and refine 2-methylnaphthalene products with high purity from wash oil by a single process of separating and refining method. At present, the separation and purification techniques of 2-methylnaphthalene are the combination of distillation, azeotropic distillation, alkylation, acid-alkaline washing, isomerization, solvent recrystallization, solvent extraction, freezing crystallization and so on. The washing-distillation-crystallization method is mature and reliable, which is the most widely used 2-methylnaphthalene production technology in industry. However, acid and alkali washing has environmental pollution, equipment corrosion and other problems. The process of washing and multistage distillation is simple and the production efficiency is high, but the purity of the product needs to be improved. The combination of distillation and azeotropic distillation is green, low cost and low indole content. It is the development direction of separating and refining 2-methyl naphthalene in the future. The method of combining chemical reaction with distillation crystallization is high in yield and purity, but the special reactor and catalyst needed for chemical reaction increase the production cost. Compared with similar enterprises abroad, domestic enterprises producing 2-methylnaphthalene have gaps in product type and purity, energy consumption, environmental protection and so on. Green environmental protection and high efficiency energy saving are the future development trends of oil washing processing enterprises. It is an effective means to improve the economic and social benefits of coal chemical enterprises to strengthen the development of new technologies and new processes, improve the product yield and purity, and solve the technical problems of industrialization and scale in 2-methyl naphthalene separation and refining. The development of the green separation process of 2-methyl naphthalene in oil washing processing to improve the coupling level of various separation and refining methods will not only meet the environmental protection requirements of "energy saving and low carbon" in the chemical production process, but also is the development direction of the future oil washing deep processing technology.

    2022 01 v.28;No.137 [PaperDigest][OnlineView][HTML全文][Download 1263K]
  • Influence of MgO on the structure and adsorption-enhanced hydrogen production performance of NiMgAlCa composite catalyst

    XU Kai;WANG Shidong;JING Jieying;LIU Lu;FENG Jie;LI Wenying;State Key Laboratory of Clean and Efficient Coal Utilization, Taiyuan University of Technology;

    One of the key technologies for the large-scale application of CO_2 sorption-enhanced methane steam reforming process for hydrogen production is the development of a composite catalyst with high catalytic and adsorption capacities. In this study, a series of NiMgAlCa composite catalysts with different MgO addition were prepared by co-precipitation method, and the influence of MgO addition on the structure of NiMgAlCa catalyst and its CO_2 enhanced sorption methane steam reforming performance were investigated. It is found that MgO addition can significantly improve the activity of the NiMgAlCa composite catalysts. In the CO_2 sorption-enhanced CH_4/H_2O reforming reaction, the as-synthesized composite catalysts can obtain a high volume fraction of H_2(98.7%) and a CH_4 conversion of 96.5% when MgO addition was 1%. The improved hydrogen production performance was ascribed to the addition of MgO, which endowed the composite catalyst a proper interaction between the active component Ni and the carrier in the NiMgAlCa composite catalyst. Meanwhile the higher specific surface area of the composite catalyst(42.5 m~2/g) provids more active sites and enhances CO_2 sorption. The small Ni particle size(13.2 nm) enhances the anti-sintering capacity of the composite catalyst, endowing the composite catalyst superior stability.

    2022 01 v.28;No.137 [PaperDigest][OnlineView][HTML全文][Download 6177K]
  • Research and application progress of foaming technology of foam ceramics made from coal-based solid waste

    MENG Fanhui;ZHANG Jinghao;DU Juan;LI Zhong;State Key Laboratory of Clean and Efficient Coal Utilization, Taiyuan University of Technology;Guoyang Investment Consulting Co., Ltd.;

    Coal-based solid waste mainly includes coal gangue discharged in the process of coal mining and coal washing, and fly ash discharged from coal-fired power plants. Because it cannot be utilised on a large scale, the continuous accumulation of coal-based solid waste caused serious environmental pollution. The improvement of environmental protection requirements makes the utilization of coal-based solid waste become the top priority of the coal industry. Foam ceramics is a new type of porous material with high temperature resistance, excellent performance and a wide range of applications. The use of coal-based solid waste to produce foam ceramics can not only realize the large-scale utilization of coal gangue and fly ash, reduce environmental pollution, but also reduce the cost of foam ceramics production. The main methods of producing foam ceramics from coal gangue and fly ash were reviewed, including foaming method, adding pore former method and the organic foam impregnation method. Different types of foaming agents can react or decompose to generate gas at high temperature, thereby creating pores in the blanks. The pore-forming mechanism of the pore-forming agent was mainly emphasized, including the effect of the amount of pore-forming agent on the pore distribution, pore size and morphology of the foam ceramics, as well as the performance of ceramic foam, such as porosity and compressive strength. The advantages and disadvantages of different preparation methods, the scope of application and main development directions were compared. The foaming method can control the anisotropy of the product, but the requirements for raw materials are relatively high, and the preparation process conditions are not well controlled. The organic foam impregnation method can regulate the morphology and composition of the foam ceramic, but it takes a long time to remove the organics. The pore former method can obtain products with complex shapes and different pore structures, but the pore former is prone to agglomeration. The application progress of foam ceramics in different fields was outlined. For different application fields, the focus of the foam ceramics performance and the requirements for the pore structure are also different. Due to the different complexity of the composition of coal-based solid waste, the development of foam ceramics is hindered to a certain extent. The problems that need to be solved in the production of foam ceramics from coal-based solid waste in the future were pointed out, i.e., to deeply study the material characteristics and sintering activity of coal-based solid waste, strengthen the theoretical study of the pore structure during the formation process, and establish the performance index system and performance standards of different types of foam ceramics produced from coal-based solid waste, so as to provide a reference for the subsequent research and large-scale application of foam ceramic properties.

    2022 01 v.28;No.137 [PaperDigest][OnlineView][HTML全文][Download 11742K]
  • Research progress on activation modification of coal gangue as rubber reinforcing filler

    HUANG Wei;YANG Kai;ZHANG Qian;LIU Jianwei;HAO Zeguang;LUAN Chunhui;State Key Laboratory of Clean and Efficient Coal Utilization, Taiyuan University of Technology;College of Chemistry and Chemical Engineering, Taiyuan University of Technology;

    Coal gangue is a solid waste discharged in the process of coal mining. The massive accumulation of coal gangue has resulted in severe environmental problems and waste of resources. Carbon black is the most important reinforcing filler in rubber production, but its production process accompanied by a lot of environmental pollution. Coal gangue has the potential to be used as rubber filler to replace or partially replace carbon black/silica, which can make rational use of solid waste resources. However, the activation and modification process is required due to the poor affinity of rubber with the minerals contained in coal gangue. The existence form, chemical composition and the current application status of coal gangue were introduced in this paper. And the mainstream activation modification methods of coal gangue and evaluation indicators of modification effect were reviewed. The current problems in the research and application of coal gangue as rubber filler were also pointed out, including the prospect of the industrial application. Coal gangue is mainly composed of Al_2O_3, SiO_2 and C. Used in rubber reinforcing filler, SiO_2 can increase the strength of rubber, Al_2O_3 plays an incremental role, and the carbon surface is rich in active sites of oxygen and hydroxyl, which is easy to cross-linked with polymer molecules. The mainstream activation modification methods include mechanical modification, calcination modification, microwave modification and surface chemical modification. Through composite modification, the particle size of coal gangue is reduced, the proportion of amorphous Al_2O_3 and SiO_2 in coal gangue is increased, and its surface properties are changed, so as to improve the dispersion and compatibility of coal gangue filler in rubber. At present, through the comprehensive evaluation of the modification effect of coal gangue filler by direct method and indirect method, it is found that the chemical modification of coal gangue surface has the most significant impact on the performance of rubber, and the selection of appropriate surface modifier can change the characteristics of rubber products. Promoting inter-industry cooperation in research, developing new surface modifiers with high quality and low price, and optimizing product detection methods is the achievement of the purpose of large-scale utilization of coal gangue rubber filler.

    2022 01 v.28;No.137 [PaperDigest][OnlineView][HTML全文][Download 12341K]
  • Research advances on H_2S removing over zeolites and its application in coal gas

    GUO Yan;XIANG Yuqiao;ZHAO Bai;WANG Wei;LI Ruifeng;CHANG Liping;LIAO Junjie;State Key Laboratory of Clean and Efficient Utilization of Coal-based Energy, Taiyuan University of Technology;Key Laboratory of Coal Science and Technology of Ministry of Education, Taiyuan University of Technology;Ningbo Fareasttech Catalytic Engineering Co.,Ltd.;School of Chemistry and Chemical Engineering, Taiyuan University of Technology;

    Coke oven gas and blast furnace gas are important secondary energy sources. The sulfur compounds not only cause environmental pollution, but also lead to catalyst poisoning in the subsequent processing and utilization, which largely limits their further utilization. Therefore, it is necessary to efficiently remove H_2S from these gas for their clean utilization. Zeolite adsorption desulfurization technology has the advantages of easy operation, low operating costs, excellent regeneration ability and long service life, so it has great application potential in desulfurization field. This paper made a review on the investigation and application of H_2S removal over zeolite. The types and characteristics of zeolites used for H_2S removal were summarized. The mechanisms of H_2S removing by zeolite were investigated. The influences of zeolite modification on desulfurization performance were discussed. And the competitive effects on H_2S adsorption caused by the components contained in coal gases, e.g., CO, CO_2, H_2O and O_2 were analyzed. Some suggestions on the development of zeolite desulfurizer were proposed based on the correlation between the mechanism of desulphurisation and the structural properties of molecular sieve. The results show that zeolites have excellent selective shape as well as acid-base site and metal site adjustability, and are widely used in the adsorption and removal of H_2S. The zeolites used for H_2S removal mainly include clinoptilolite, LTA, FAU, MFI and titanium silicon zeolites. The mechanism of H_2S adsorption on zeolites is closely related to the active site. Depending on the active site, H_2S adsorption mechanisms include Si—OH adsorption mechanism, alkali metal dissociation mechanism, transition metal coordination mechanism and surface acid-base interaction mechanism, which are closely related with the crystal structure and surface physical and chemical properties of zeolites. Metal element modification and surface acid-base modification can effectively improve their desulfurization performance. Gas composition can also affect the desulphurisation performance of zeolites: H_2O molecules and H_2S molecular structural similarity, resulting in strong competition for adsorption; CO can be coordinated with transition metal ions, such as Cu~+, resulting in competition for adsorption; acidic gas CO_2 will combine with the molecular sieve surface alkaline sites to produce competition for adsorption, in addition to the reaction with H_2S to generate COS; O_2 can cause the generation of singlet sulphur, giving O_2 can cause the formation of singlet sulphur, making the regeneration of the adsorbent difficult. Based on the analysis of existing research, further clarification of the structure-activity relationship of the adsorbent and the intrinsic mechanism of competitive adsorption, as well as the kinetic behavior of H_2S adsorption in gas purification will be the focus of future research. In the process of developing the application of zeolite adsorbent for H_2S removal, the following aspects should be taken into consideration: operation conditions, proper adsorption mechanism and the corresponding modification, avoiding and inhibiting the competitive adsorption, improving regeneration ability and reducing preparing costs.

    2022 01 v.28;No.137 [PaperDigest][OnlineView][HTML全文][Download 20694K]
  • Research progress on carbonation of municipal solid waste incineration fly ash

    ZHENG Xufan;DU Yi;MIAO Endong;XIONG Zhuo;ZHAO Yongchun;ZHANG Junying;State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology;Department of Geology, Northwest University;

    Municipal solid waste incineration(MSWI) fly ash, as a kind of hazardous waste, has been a research hotspot for resource treatment by reasonable means. The carbonation of MSWI fly ash for CO_2 storage has been widely concerned in recent years. In this paper, the status of carbonation treatment of MSWI fly ash was systematically analyzed. Firstly, the composition and treatment methods of MSWI fly ash were briefly described. The main components include CaO, SiO_2, Al_2O_3, soluble Na/K salts and heavy metals, etc. At present, they are mainly treated by cement solidification, melting solidification and chemical treatment. The carbonation reaction mechanism was described. The potential of CO_2 isolation from fly ash was introduced from the aspect of the influence of fly ash components on carbon fixation rate. Then, the influencing factors of the carbonation reaction of MSWI fly ash were analyzed, including reaction temperature, liquid-solid ratio, reaction atmosphere, CO_2 volume fraction, reaction pressure, particle size, reaction time and process conditions, etc. It is concluded that: different reaction conditions have different requirements for temperature and CO_2 volume fraction, the liquid-solid ratio is generally about 0.3, the existence of SO_2 in the reaction atmosphere hinders the reaction forward. The reaction pressure doesn′t affect the carbonation equilibrium, but it plays an important role in the whole process kinetics. Too large or too small particles are unfavorable to the reaction. The carbonation rate decreases with time, and the liquid-phase reaction is better than the gas-solid direct carbonation. The carbonation process model of MSWI fly ash, including leaching-precipitation model, shrinking core model and surface covering model was introduced. The simulation results of carbonation reaction kinetics were analyzed. The results show that the relative strength of interfacial reaction and diffusion depends on the amount of water. Finally, the influence of carbonation reaction on heavy metal and soluble salt leaching behavior of MSWI fly ash was analyzed. The potential application prospect and challenge of carbonation treatment of municipal solid waste incineration fly ash were prospected, so as to provide a way for the carbonation treatment of fly ash from solid waste incineration.

    2022 01 v.28;No.137 [PaperDigest][OnlineView][HTML全文][Download 8845K]
  • Performance and mechanism of low-concentration CH_4 catalytic combustion based on composite oxides of Cu-Ce

    ZHANG Chenhang;DOU Baojuan;TENG Zihao;WU Liangkai;HAO Qinglan;BIN Feng;College of Marine and Environmental Sciences, Tianjin University of Science & Technology;State Key Laboratory of High Temperature Gas Dynamics, Institute of Mechanics, Chinese Academy of Sciences;

    A large quantity of CH_4 is discharged from exhaust gas in China every year, which causes serious environmental pollution of atmosphere. Catalytic combustion is considered as one of the most effective ways to remove methane due to its low operating temperature and high efficiency. Herein, three catalysts, CuO-CeO_2, CuO and CeO_2, were prepared by sol-gel method to investigate the catalytic combustion activity of CH_4 under(1% CH_4, 78% N_2 and 21% O_2) atmosphere. The physical structure and surface properties were characterized using XRD, XPS, H_2-TPR and O_2-TPD techniques, etc. The results show that Ce ions not only promote the dispersion of Cu on the catalyst surface, but also the conversion between trivalent(Ce~(3+)) and tetravalent(Ce~(4+)) improves the oxygen storage and release capacity of the catalyst, which is beneficial for CuO-CeO_2 to improve the catalyst activity. The evaluation of catalyst activity provides evidence that the activity order of the three catalysts follows the order CuO-CeO_2>CuO>CeO_2. Then, the most active CuO-CeO_2 catalyst is employed to further investigate kinetic partial pressure experiment and reaction mechanism to determine the reaction rate of methane at different oxygen/methane partial pressure ratios. The results indicate that the reaction follows the L-H mechanism, that is, the adsorbed CH_4 reacts with the adsorbed O_2. Based on in-situ infrared spectra analysis, the microscopic reaction mechanism of CH_4 over CuO-CeO_2 catalyst is proposed: CH_4 is firstly adsorbed on the surface of CuO-CeO_2 and then reacts with CuO-CeO_2 to produce intermediate products methoxy substance(Cu-OCH_3) and formate substance(Cu-OOCH). Finally, the intermediate products are decomposed into CO_2 and H_2O to achieve the purpose of the complete oxidation.

    2022 01 v.28;No.137 [PaperDigest][OnlineView][HTML全文][Download 9199K]
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