Table of Content

22 January 2020, Volume 20 Issue 1

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Contents

Cover and Contents

Chin. J. Process Eng.. 2020, 20(1):  0. 

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Editorial

Editorial from the Editor-in-Chief

Suojiang ZHANG

Chin. J. Process Eng.. 2020, 20(1):  1-2.  DOI: 10.12034/j.issn.1009-606X.220001

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四季更迭，岁去年来，才刚刚叹完红枫知秋，不知不觉又到了雪漫故园的时节。时光总是不慌不忙，不急不缓，见证了时空交替的神奇转换，时光承载了过去一年里的重担和升华，也满载着对未来的期望与寄托。在这样一个新旧更替、万象更新的时刻，《过程工程学报》也细细回首了一路走来的点滴，展望新的憧憬、新的企盼！

Reviews

Prospects of process and bioreactors for large scale cultured meat production

Xueliang LI Guoqiang ZHANG Xinrui ZHAO Xiulan SUN Jingwen ZHOU Guocheng DU Jian CHEN

Chin. J. Process Eng.. 2020, 20(1):  3-11.  DOI: 10.12034/j.issn.1009-606X.219179

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The idea of culturing animal muscle tissues in vitro as food stocks for human consumption was conceptualised as early as 1930s and patented in the 1990s, but the technique has not been proven at an industrially relevant scale as of today. In the past five years or so, cultured meat enjoyed a surge of popularity in terms of media coverage, particularly since the high profile taste-test event of the first lab-grown beef burger in 2013. Over two dozens of companies have joined the effort to bring cultured meat to the market, but a consumer-ready product is yet to be seen. In addition to regulatory requirements and socio-ethical implications, a major bottle-neck that is hindering the implementation of large scale cultured meat production is the lack of an understanding of the scaling-up effects on animal cells, including mass transfer, heat transfer, mixing and shear stress, etc. Conventionally, animal cells and tissues are mostly cultured in the high-value, low-volume pharmaceutical industry. Even production facilities that are considered high-throughput are typically clusters of small production lines under 2?20 m3 running in parallel, where the homogeneity of the culturing environment is relatively easily maintained. Cultured meat from animal muscle cell cultivation as a commodity to compete with the agriculture industry demands volumes of bioreactors and cell densities at least an order of magnitude higher than what the current technology can provide. Significant progresses in the development of bioreactor technology are required to make cultured meat a commercially viable alternative source of animal protein. In this review, the bioreactor aspects of cultured meat production, including reactor type and operation mode were covered, as well as existing drawbacks and potential solutions.

Flow & Transfer

Mechanism analysis of refrigeration performance of gas wave oscillation tube influenced by high-temperature port pressure

Peiqi LIU Chuhan GAO Xiang LI Yang YU Dapeng HU

Chin. J. Process Eng.. 2020, 20(1):  12-19.  DOI: 10.12034/j.issn.1009-606X.219129

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The high-temperature port pressure is an important parameter affecting the refrigeration performance of the gas wave oscillation tube. By establishing a double-opening gas wave oscillating tube experimental platform, the relationship between the cooling temperature drop of the gas wave oscillating tube and the high-temperature port pressure was quantitatively measured. In order to analyze the internal mechanism of the phenomenon, an analysis model of the gas wave oscillating tube was established. It was found that the temperature drop of the whole machine increased first and then decreased with the increase of the high-temperature port pressure. The pressure of high-temperature port had the optimal value. When the high-temperature port pressure was low, the interface between the incident gas of the gas wave oscillating tube and the original gas in the tube was discharged from the high-temperature port of the oscillating tube, so that the reflux gas at normal temperature in the low-temperature port increased, and blended with the low-temperature incident gas after expansion in the tube, reducing the cooling performance of the oscillating tube. The simulation results showed that when the high temperature port pressure were 0.10 and 0.14 MPa, the ratio of high-pressure gas in HT to total high-pressure gas was 7.4% and 4.9%, respectively. As the pressure of the high-temperature port increased, the cooling performance was improved. However, the high-temperature port pressure also promoted the increase of the reverse compression wave intensity. The reverse compression wave pressures were 0.107 and 0.135 MPa at high-temperature port pressure of 0.11 and 0.14 MPa, respectively, which was not conducive to refrigeration. Therefore, the blending degree of the incident high pressure gas and the high-temperature side gas and the reverse compression wave pressure were the two factors why the high temperature port pressure had an optimum value.

Numerical simulation of mass transfer characteristics in an airlift reactor with a horizontal sieve plate

Zifan WANG Zhiyong ZHENG Minjie GAO Xiang LI Xiaobei ZHAN

Chin. J. Process Eng.. 2020, 20(1):  20-26.  DOI: 10.12034/j.issn.1009-606X.219137

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A CFD simulation of the mass transfer and flow field characteristics of gas–liquid two phases in an airlift reactor with a horizontal sieve plate was carried out by combining turbulent aggregation kernel with Lehr breakage kernel in the population balance model. The simulation results agreed well with the experimental results. The effects of horizontal sieve plate on the gas holdup, bubble diameter, volumetric mass transfer coefficient and gas–liquid flow field and velocity in the airlift reactor were investigated. It showed that the accumulation of the gas phase beneath the sieve plate increased the local gas holdup in the region, thereby increasing the overall gas holdup in the reactor. The forced re-distribution on the gas phase by the sieve plate attenuated bubble coalescence in the region between the sieve plate and the liquid surface, thereafter, decreased bubble diameter and increased the specific surface area of bubbles. A large number of bubbles smaller than the bubbles with the initial diameter were generated by the holes on the sieve plate with the breakup action, which increased the specific surface area of bubbles near the sieve plate. The velocity difference between the gas and liquid phases in the vicinity of the sieve plate was increased by the retardation on the liquid phase, thus improving the mass transfer coefficient of the liquid film in the region. The sieve plate reduced the flow velocities of liquid and gas in the reactor, thereby increased the contact time between the gas and liquid phases, increased the overall gas holdup of the reactor and enhanced the gas–liquid mass transfer. The volumetric mass transfer coefficient in the reactor was improved by assembling the horizontal sieve plate. The works would be beneficial to optimized internal structure of the airlift reactor and its applications.

Physical simulation on molten steel flow characteristics in the RH reactors with different arched snorkels

Zhifeng REN Zhiguo LUO Zongshu ZOU

Chin. J. Process Eng.. 2020, 20(1):  27-34.  DOI: 10.12034/j.issn.1009-606X.219171

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In order to improve the vacuum refining efficiency of Ruhrstahl–Heraeus (RH), three new RH vacuum degassing vessels with arched snorkels were designed and the corresponding physical models were established. In the water simulation experiment, the circulation flow rate and mixing time of the RH with arched snorkels and rounded snorkels were researched from the aspects of snorkel shape, gas flow rate and the insertion depth of the snorkel. The results showed that, compared with conventional RH with rounded snorkels, the circulation flow rate of new RH reactors increased by 45%~218%, the mixing time decreased by more than 15%. When the maximum gas flow rate of RH with rounded snorkels reached, the circulation flow rate of the three RH with arched snorkels still increased linearly. Compared with the gas flow rate of traditional RH (60~130 m3/h), the maximum circulation flow rate of new RH reactor with arched snorkels increased by more than 48%, which would be convenient short-time and high-strength vacuum refining operation. For the three new type RH with arched snorkels, the circulation flow rate linear increased with the increase of gas flow rate and increased with the increase of immersion depth, and the mixing time decreased accordingly. In practical application, the immersion depth of two RH with relatively small arches should be greater than 545 mm, the immersion depth of RH with maximum arches should be greater than 818 mm, the maximum gas flow rate of three RH reactors with arched snorkels should be controlled at about 173 m3/h. Compared with a gas flow rate of traditional RH (60~130 m3/h), the circulation flow rate of 1#, 2# and 3# RH with arched snorkels increased about 100%, 42% and 112% respectively, mixing time reduced more than 30%, 15% and 34% respectively. In argon flow rate range of the experiment, the circulation flow rate of RH with unsymmetrical arched snorkels was the maximum, and its mixing time was the minimum.

Pressure drop of gas-solid parallel flow in an axial moving bed filter

Han Lü Yiping FAN Yafei ZHAO Chunxi LU

Chin. J. Process Eng.. 2020, 20(1):  35-43.  DOI: 10.12034/j.issn.1009-606X.219184

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The pressure drop characteristics of an axial moving bed were investigated by varying the operating parameters including the superficial activation energy gas velocity, the particle circulation rate and the dust concentration in the inlet gas. The results showed that when the circulation rate of particles increased from 0 to 2.26 kg/(m2?s), the pressure drop of the equipment decreased slightly by 0.03 kPa. Besides, the influence of press cake in bed on the stability of pressure drop was studied under the operating condition of dust load. When the dust concentration in the inlet was low, the dust deposited in the moving bed could not form a stable filter cake structure, and the pressure drop fluctuation of the equipment was considerable. When the inlet gas dust concentration increased to 89.10 g/m3, the formation of filter cake in the moving bed tended to be stable, and the pressure drop operation of the equipment gradually became stable. Under dust load condition, when the equipment was in the fixed bed operation state, the static pressure drop increased rapidly with filtration, and increased with the increase of the dust concentration in the inlet gas, and the pressure drop increased faster. In addition, the pressure drop of the equipment reached a stable state around 500 s, at which time the pressure drop increased by about 0.10?0.14 kPa, and the fluctuation amplitude of the pressure drop after 500 s gradually decreased with the increase of dust concentration. Furthermore, when the superficial activation energy gas velocity was 0.126 m/s and the dust concentration was 89.10 g/m3, the process of press cake forming and damaging present a dynamic balance. After filtering for 500 s, the pressure drop stabled at 0.88 kPa. At the same time, the equipment had a high dust removal performance, and the dust collection efficiency of the equipment was more than 96%.

Process & Technology

Synthesis of the polyacrylic acid aluminum modified bentonite composite and its adsorption of Cr(VI)

Shuang WANG Hongfei GUO Bin ZHAO Xiuwu LIU Jilin CAO

Chin. J. Process Eng.. 2020, 20(1):  44-51.  DOI: 10.12034/j.issn.1009-606X.219141

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The pollution caused by toxic metal ions on ecosystems, agriculture and human health has attracted worldwide attention. Cr(VI) has detrimental effects on livers, lungs, kidney and nervous systems of mammals. Thus, the removal of Cr(VI) ions from wastewater are very important. Cr(VI) occurs as CrO42?, HCrO4?, Cr2O72? and HCr2O7? in aqueous solution. The surface of natural bentonite is negatively charged and has a small adsorption capacity for anions. The natural bentonite is powdery and difficult to separate from treated aqueous solutions. To improve the adsorption performance and application performance of bentonite to Cr(VI), the polyacrylic acid aluminum modified bentonite composite was prepared according to the following steps. Bentonite was modified with aluminum chloride hexahydrate, the polyacrylic acid-modified bentonite was prepared by polymerization of acrylic acid with aluminum modified bentonite in aqueous solution, and the polymer product were modified with hexadecyl trimethyl ammonium bromide (CTMAB) in aqueous solution. The characteristics of natural bentonite and modified bentonite were determined by XRD, FT-IR and SEM. Batch adsorption of Cr(VI) onto modified montmorillonite was investigated. The results showed that aluminum, acid monomers and CTMAB had intercalated into bentonite interlayers, and did not destroy the basic structure of natural bentonite. The adsorption capacity of Cr(VI) was 1.996 mg/g for 200 mL initial concentration of 20 mg/L by 0.5 g adsorbent at 25℃. The adsorption process to Cr(VI) was corresponding with the Lagergren secondary adsorption kinetics equation, chemical adsorption was the main control step. The adsorption capacity of the adsorbent increased with increasing the initial concentration of Cr(VI). The equilibrium adsorption capacity of the adsorbent for different concentrations of Cr(VI) was corresponding with the Freundlich isotherm equation. The adsorption of Cr(VI) onto the composite bentonite was multimolecular layer adsorption. The adsorption of Cr(VI) by granular adsorbent was mainly complexation reaction adsorption.

Simulation and optimization of methylchlorosilane distillation scheme

Xiongwei ZENG Jinxin PENG Zhenhao XI Ling ZHAO Weikang YUAN Changhong NIE Xiaohui ZHAO

Chin. J. Process Eng.. 2020, 20(1):  52-58.  DOI: 10.12034/j.issn.1009-606X.219156

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Methylchlorosilane crude monomer is the mixture of several components with a close boiling point, which demands high mass purity in subsequent polysiloxane polymerization process. Traditionally, seven to ten distillation columns are used to separate these methylchlorosilane components with huge energy consumption. In the field of this research, prevailing industrial seven-column scheme was simulated by using Aspen plus software. The effect of distillation column bottom extraction ratio, reflux ratio, feed stage and top pressure on product concentration and heat duty were studied systematically for the optimization of operation conditions using the method of double factors sensitivity analysis. According to sensitivity analysis, the appropriate operation conditions of Me1 column were as follows, that molar bottom extraction rate was 0.92, molar reflux ratio was 130, feed position was at 210th theoretical stage and top pressure was 0.18 MPa, respectively. According to energy calculation of seven-column scheme, heavies removal column, low removal column and Me1 column took up 96.2% of total heat duty consumption. In order to reduce energy consumption, new energy saving scheme was studied and simulated. Thermodynamic analysis showed that pressure was a non-significant influencing factor for key components separation of heavies removal column and low removal column. So, a more energy-efficient distillation process, double effect distillation, had been studied for two columns to achieve heat integration between heavies removal column condenser and low removal column reboiler. The result of rigorous simulation showed that the new double effect distillation scheme, comparing to original two-column scheme, can reduce total annual cost (TAC) by 39.70%. The thermodynamic analysis of Me1 column showed that relative volatility of key binary components was near 1. So the heat pump distillation scheme had been developed to improve heat efficiency of Me1 column. The result of rigorous simulation showed that heat pump distillation scheme, comparing to original Me1 column scheme, can reduce TAC by 41.42%.

Estimation of surface tension of Al-Mg-Li ternary alloy

Shanshan LIU Bo WANG Ailin ZHOU Jieyu ZHANG Kuochih CHOU

Chin. J. Process Eng.. 2020, 20(1):  59-66.  DOI: 10.12034/j.issn.1009-606X.219180

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The characteristics of the aluminum?magnesium alloy are light, good mechanical properties, corrosion resistance, low energy consumption, green and cheap, which make it more and more popular. Currently, aluminum?magnesium alloy has been widely used in automobile manufacturing, doors and windows sheet, medical apparatus and instruments, aerospace and marine transportation and other fields. The performances of aluminum?magnesium alloy are mainly affected by its thermophysical properties. It is important to study the surface properties involved in the presence of all liquid processes in the industrial process than other thermophysical properties. Surface tension, one of the key influence factors to the reaction of multiphase system and mass transfer, is a significant property of liquid metal, which plays a decisive role in the crystal growth of alloys, the microscopic appearance of welded joints and the cracking of metals during solidification. However, it is difficult to measure the surface tension at high temperature, only a small number of reference data can be referred to. In this work, the surface tensions of the Al?Mg, Al?Li and Mg?Li binary systems at 973 K were estimated on the basis of Butler?s equation, in combination with excess Gibbs energies, and the factors influencing surface tension were studied. The calculation results showed that the surface tension of aluminum melts decreased with the increase of magnesium or lithium content, the surface tension of magnesium melt decreased with increasing additions of lithium. On this basis, the surface tension of Al?Mg?Li ternary alloy at 973 K was calculated by using Chou model. The calculation results indicated that surface tension of Al?Mg?Li ternary alloy was approximately in the range of 0.326?0.851 N/m and its surface tension increased as the aluminum or magnesium content increased. Further, the essential factors that influence the surface tension were obtained. The results have important theoretical significance and practical application value for engineering research.

The regulation of electric field on CaO-SiO2-Al2O3 slag structure

Pan ZHANG Junhao LIU Kuixian WEI Zhi WANG Wenhui MA

Chin. J. Process Eng.. 2020, 20(1):  67-73.  DOI: 10.12034/j.issn.1009-606X.219182

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To development the photovoltaic industry for high-quality, high-end, the high-quality silicon raw materials are urgently required. Since boron (B) has a large separation coefficient and a small saturated vapor in the silicon, it is difficult to remove by directional solidification and vacuum melting or the like. B in silicon is one of the most difficult impurities to remove, slag refining is a mean to effectively remove B from silicon materials. In the slag refining process, the introduction of electric field can significantly improve the refining effect. The refining effect is closely related to the slag structure. In view of the difficult problem of removing B from silicon, this work studied on the structural level. The influence of electrical field on the structure was studied by observing the changes of different part of the slag structure and the high temperature quenching slag structural under different electric field conditions. It was found that the introduction of electric field caused the directional movement and redistribution of ions in slag, which caused the change of the slag structure. The upper structure of the slag was more completely depolymerized under the action of the electric field, but the slag structure was basically unchanged in the part which was from the interface of the slag. The electric field enhancement was beneficial to the depolymerization of the slag and when the electric field strength reached 10 V, the relative amount of Q0 structural unit with more non-bridge oxygen (NBO) increased. The upper structure of the slag was more sensitive to the change of the electric field. But the change of structure in the lower part of the slag was not obvious when the electric field changed.

Biochemical Engineering

Stability and biofouling behavior of plastic films in microalgae cultivation

Yixuan WANG Chenghu YAN Wei CONG

Chin. J. Process Eng.. 2020, 20(1):  74-83.  DOI: 10.12034/j.issn.1009-606X.219175

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The stability of six typical kinds of plastic films including polyethylene (PE), polypropylene (PP), ethylene/vinyl acetate (EVA), polyvinyl chloride (PVC), polyurethane (PU) and polyethylene terephthalate (PET) in NaClO, NaOH and HCl solutions and biofouling behavior in microalgae cultivation (Chlorella vulgaris) system were studied. The results showed that PVC film performed the poorest stability, and the transmittance decreased about 50% after immersing in NaClO, NaOH and HCl solutions. The transmittance of PU film and EVA film declined 10%?15% in NaClO and NaOH solutions, respectively. The transmittance of the other three kinds of plastic films has no significant change when immersed in NaClO, NaOH and HCl solutions for 24 h. Obvious microalgae biofouling behavior happened in six kinds of films, which was a typical biofilm formation process. Adhesion behavior of PVC surface was the most distinct, and the transmittance declined to about 0 on the 7th day, and the amount of adsorption solids increased with time and reached 3069 ?g/cm2 on the 45th day. However, the amount of adsorption solids on PU, EVA, PE, PP and PET film surface increased sharply and then decreased with time, the maximum amounts were 292, 375, 292, 194 and 236 ?g/cm2, respectively. The increase of chlorophyll content on the surface of the plastic films was not obvious in the first 4 d, which indicated that the initial stage of the adhesion was mainly the adhesion of protein and extracellular polymeric substances (EPS), and then microalgae cells began to adhere. The attachment of protein, EPS and microalgae cells on the plastic films was a typical biofilm formation process. The adhesion behavior of microalgae was affected by chemical structure and surface properties of the films, such as hydrophilicity, roughness and surface charge. For Chlorella vulgaris, polyolefin (PE, PP, etc.) and PET film surface with high hydrophilicity, low roughness and negatively charged will perform good anti-biofouling properties.

Preparation of biomimetic peptide attached supermacroporous poly(glycidyl methacrylate) microspheres for monoclonal antibody purification and its performance

Jia GE Xiangming NA Xuexing WU Weixing YANG Dongxia HAO Guanghui MA

Chin. J. Process Eng.. 2020, 20(1):  84-90.  DOI: 10.12034/j.issn.1009-606X.219166

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Recently, immunoglobulin G (IgG) has attracted great attentions in clinical medicine, biotechnology, stimulated the development of downstream purification technology of monoclonal antibodies. Now, the protein based affinity ligands during traditional chromatographic purification of IgG exist drawbacks including the high cost and low stability, which leads to the secondary contamination and biological toxicity to purified sample. Also the chromatographic agarose microspheres present shortcomings such as the gel compressibility and the mass transfer limitations. In this work, biomimetic peptide as the protein based ligands alternative, grafting on the supermacroporous dextran-poly(glycidyl methacrylate) microspheres (Dextran-PGMA) to overcome above drawbacks were prepared and to efficiently improve the IgG chromatographic separation. The hydroxy on dextran-grafted polymer chromatographic microspheres were converted to the epoxy groups in epichlorohydrin solution with 2 mol/L NaOH, and the epoxy groups were opened and coupled with biomimetic peptide, FYEILCH, to achieve the purpose of affinity modification. The SEM observed that the pore structure of macroporous was mostly maintained after coupling with the biomimetic peptide. The change of 10% dynamic binding capacity (DBC10%) of FYEILHC based on Dextran-PGMA microspheres and agarose microspheres under different flow rate (92~923 cm/h) was compared. The DBC10% of dextran-PGMA was declined only 8% under 923 cm/h, whereas the DBC10% of agarose was sharply declined about 25%. This phenomenon might be related to better mass transfer for IgG at higher flow rate on the Dextran-PGMA microspheres. The DBC10% of Dextran-PGMA microspheres maintained (21±1) mg/mL after cleaning-in-place (CIP) 40 cycles using 0.1 mol/L NaOH, indicating that the affinity medium had good chemical stability. The purity of recovered antibodies in plasma was 95.0%, demonstrating that this biomimetic peptide based affinity medium had great potential to purify IgG from complex biological samples. This biomimetic peptide grafted supermacroporous poly(glycidyl methacrylate) microspheres could meet the requirement for rapid and high-throughput separation of monoclonal antibody.

Optimization of enzymatic hydrolysis conditions for antioxidant peptide preparation from velvet antler collagen by response surface methodology

Yaru LAN Shuo HUANG Fei ZHAO Hongyu WU Yongxue GUO

Chin. J. Process Eng.. 2020, 20(1):  91-98.  DOI: 10.12034/j.issn.1009-606X.219174

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It is believed that the velvet antler head has the best health benefits in traditional Chinese medicine. But its output is small, and the price is high. The first section of velvet antler is used frequently, and its protein/peptide content is highest among all sections. The polypeptide molecular weight is about 5 kDa. In this work, in order to make full use of the velvet antler resources, the water extract of the middle and low sections collagen of velvet antler was used as an enzymatic substrate to prepare an antioxidant peptide using papain. Enzymatic hydrolysis conditions (time, enzyme addition ratio, pH and temperature) were optimized by response surface methodology (RSM). The 1,1-diphenyl-2-picrylhydrazyl (DPPH?) radical-scavenging activity rate was used as an index. The target antioxidant peptide (molecular weight less than 5 kDa) obtained by separation through an ultrafiltration membrane was further separated by reversed-phase high-performance liquid chromatography. And 10 components, S1?S10, were obtained respectively and the components were lyophilized. Component S3 was further subjected by reversed-phase ultra-high performance liquid chromatography (UPLC) on-line electrospray ionization mass spectrometry (ESI-MS) for molecular weight determination. The polypeptide with the highest antioxidant activity was fractionated by ultrafiltration membranes of molecular weight cut off of 50, 10 and 5 kDa respectively. The results showed that the optimal experimental conditions were time of 56 min, enzyme addition of 1.40wt%, pH of 5.60, temperature of 60℃, DPPH? radical-scavenging activity rate was 83.09%. The molecular weight of polypeptide was 0.2?0.6 kDa. The resulting small molecule peptide has similar health benefits as the head section, is more easily absorbed by the body, and is easier to further process and store.

Molecular weight and molecular weight distribution of alginate determination by gel permeation chromatography

Ruixin ZHANG Zhihui WANG Wei CONG Fengji HUI Bin WANG

Chin. J. Process Eng.. 2020, 20(1):  99-107.  DOI: 10.12034/j.issn.1009-606X.219177

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A method for the determination of molecular and molecular weight distribution of alginate by gel chromatography and conventional detector was proposed. Alginates in a wide range of viscosities extracted from two dominated raw materials—Lessonia nigrescence and Lessonia trabeculata were taken as the samples. The relative molecular weight of alginate was determined by high-performance gel permeation chromatography (GPC) combined with refractive index detector (RID) with pullulan served as a standard. The corresponding relations of relative weight average molecular weight ( ), relative number average molecular weight ( ) measured by GPC–RID and absolute weight average molecular weight ( ), absolute number average molecular weight ( ) measured by multi-angle laser scattering (GPC–MALLS) were obtained by least square method. The results showed that there was a good linear correlation between the relative molecular weight of alginate determined by GPC–RID and the absolute molecular weight of alginate determined by GPC–MALLS. The correlation index was more than 0.9. The relative error between the absolute weight average molecular weight determined by the established GPC–RID method and the absolute weight average molecular determined by GPC–MALLS was less than ?12%. The relative error between the absolute number average molecular weight determined by the established GPC–RID method and the absolute number average molecular determined by GPC–MALLS was less than ?12%. The polydispersity index calculated by the established GPC–RID method was less than ?12%, compared with that obtained by GPC–MALLS method. The GPC–RID method for the determination of the relative molecular weight of alginate can be used to determinate the absolute molecular weight and the polydispersity index of alginate. It manifested that it was feasible and economical to use the GPC–RID method provided in this work for the determination absolute of the absolute weight molecular weight, absolute number molecular weight and polydispersity index of alginate. The method can save the investment on the instrument and reduce the cost of determination the molecular weight of alginate.

Environment & Energy

Ionic liquids self-templating to synthesize nitrogen-doped porous carbon materials for CO₂ adsorption

Jiahui LIU Huiting LIU Guoying ZHAO Zhenyu SUN

Chin. J. Process Eng.. 2020, 20(1):  108-115.  DOI: 10.12034/j.issn.1009-606X.219164

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With the increase of man-made emissions, CO2 capture after combustion has become a key component of greenhouse gas emission reduction. The search for a better CO2 capture material has caused great attention and nitrogen-doped porous carbon materials are considered as one of the most promising candidates. However, traditional preparation methods of nitrogen-doped porous carbon materials suffer from the shorts of complex process, harsh reaction conditions and low product yield. Using ionic liquids as the raw materials to synthesize nitrogen-doped porous carbon materials through ionothermal cyclotrimerization is a simplified and high-yield manner. In the present works, a series of nitrogen-doped porous carbon materials were synthesized directly by high temperature carbonization using cyano ionic liquids as raw material. By varying the structure and anions of the ionic liquid precursor and synthesis conditions, the pore architecture and surface functional groups of the materials could be controlled. The ionic liquid precursors were characterized by 1H-NMR, CHN element analysis and thermogravimetric analysis (TGA). The nanostructure of the porous carbon materials were observed by Transmission Electron Microscope (TEM) and the types of N-containing groups of the carbon material were investigated by X-ray photoelectron spectroscopy (XPS). The N element content was confirmed by elements analysis. The pore structures were evaluated by Brunauer–Emmett–Teller (BET) nitrogen sorption isotherms measured at 77 K. CO2 adsorption performance of these materials was carried out on a gravimetric microbalance (IGA). Combing the BET results and TGA analysis showed that the anions of ionic liquids acted as the template agent in the process of polymerization. These nitrogen-doped porous carbon materials mainly had mesoporous structure and the highest specific surface area reached to 732.6 m2/g. The highest N content reached to 9.9wt%. Owing to strong interactions between the CO2 molecules and nitrogen-containing basic sites, the highest CO2 adsorption quantity reached to 20.9wt% under 1.8 MPa at 25℃. The materials could be completely regenerated under the vacuum at 180℃, indicating its good stability.

Effect of Zn modification on hydroisomerization performance of the Fischer?Tropsch heavy diesel over Ni/ZSM-22 catalyst

Yiling BAI Lichuang FAN Tao LI Huimin CHEN Huaike ZHANG Yong YANG Guangjin ZHANG

Chin. J. Process Eng.. 2020, 20(1):  116-122.  DOI: 10.12034/j.issn.1009-606X.219167

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The hydroisomerization catalyst is a metal-acid bifunctional catalyst that provides addition dehydrogenation function by metal component, and acidic component provides isomerization function. Hydroisomerization can effectively reduce oil pour point, provide low-temperature flow performance, and improve oil quality. The ZSM-22 zeolite was modified by ion exchange, molding and loading methods to obtain different Zn loadings. The physicochemical properties were characterized by X-ray diffraction (XRD), N2 physical adsorption-desorption (BET), X-ray fluorescence (XRF) and pyridine adsorption infrared (Py-IR). Ni-based hydroisomerization catalyst was prepared by using modified ZSM-22 zeolite as an acidic component and Ni as a metal component. The heterogeneous pour point depressing performance was evaluated by using Fischer–Tropsch heavy diesel oil as a raw material in the fixed bed reactor. Liquid and gas products were measured by off-line gas chromatography and on-line gas chromatography to calculate diesel yield. The results showed that ion exchange had little effect on the zeolite structure, and Zn species were highly dispersed on the surface of the zeolite. The Br?nsted (B) acid content of the catalyst had a significant effect on the activity. The higher B acid content, the higher activity of the catalyst. The introduction of Zn in the zeolite reduced the acidity ratio of B acid to Lewis (L) acid (B/L). With the increase of Zn content, the B/L value decreased, the yield of isomeric hydrocarbon increased, the cracking reaction was effectively inhibited, and the diesel yield was improved. Loading Zn could significantly reduce the cold filter point of heavy filter, and the cold filter point rose with Zn load content increased gradually. When the metal hydrogenation performance was the same, the matching of the metal and acid sites on the catalyst and the heterogeneous performance of the heavy diesel were improved with the decrease of B acid content. When the cold filter point of diesel reached the requirement of -10# diesel of China VI National Standard (cold filter point –5℃), the yield of prepared HI-3 catalyst reached 90.65%.