Adsorption properties of polyacrylonitrile‐based activated carbon hollow fiber

In this work, polyacrylonitrile (PAN) hollow fibers are pretreated with ammonium dibasic phosphate and then further oxidized in air, carbonized in nitrogen, and activated with carbon dioxide. The adsorption properties of the resultant activated carbon hollow fibers (ACHF) prepared in different conditions were studied. The results show that the adsorption properties of ACHF change regularly with preparing conditions of ACHF. The different adsorption ratios to three adsorbates reflect the number of micropores and mesopores in PAN‐based ACHF. Pretreatment with phosphate can increase the number of mesopores. Proper oxidation temperature and time can increase the number of micropores and mesopores. When carbonization temperature is more than 900°C and carbonization time ranges from 50 to 90 min, the number of micropores and mesopores, especially mesopores, greatly increases. Compared with other treatments, activation treatment greatly increases the number of micropores and mesopores, and the dominant pore sizes of mesopores in PAN‐based ACHF are from 2 to 10 nm. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 602–607, 2004     

Effects of activation time on the properties and structure of polyacrylonitrile‐based activated carbon hollow fiber

Polyacrylonitrile (PAN) hollow fibers were pretreated with ammonium dibasic phosphate, then further oxidized in air, carbonized in nitrogen, and activated with carbon dioxide. The effects of activation time of a precursor fiber on the microstructure, specific surface area, pore‐size distribution, and adsorption properties of PAN‐based activated carbon hollow fibers (PAN‐ACHF) were studied in this work. The BET surface area of PAN‐ACHF and surface area of mesopores gradually increase with activation time extending, and reach the maximum values, 780 and 180 m² g^?1, respectively, when fibers are activated at 800°C for 100 min. The adsorption ratio to creatinine changes little with activation time extending and all values over all activation time are above 90%. The adsorption ratio to VB₁₂ gradually increases with activation time extending before 60 min, and then becomes relatively constant from 60 to 100 min. The number of pores on the surface of PAN‐ACHF increases with activation time extending. The amount of mesopores in PAN‐ACHF made of fibers activated for different time increases with activation time extending and the dominant pore sizes of mesopores in PAN‐ACHF range from 2 to 5 nm. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 2565–2569, 2006     

Raman spectroscopic study of the microstructure of carbon films developed from cobalt chloride‐modified polyacrylonitrile

Polyacrylonitrile (PAN) was modified with cobalt chloride at 90°C for 5 min. The carbon films prepared from original and modified PAN films were carbonized up to 1300°C. The structure of the resulting carbon film was studied using X‐ray diffraction and Raman spectroscopy. The stacking size obtained from X‐ray diffraction approaches the L_c value of the resulting carbon films as the heat treatment temperature increased. The mean average carbon basal planes in crystalline (Lc/d) also increased with increasing pyrolysis temperature. Raman spectra confirmed the progressive structural ordering as treatment temperature increased. During pyrolysis, a substantial decrease in the intensity of the band near the 1350 cm⁻¹ region was observed, indicating a decrease in the disordered structure. The crystal size (L_a) of the resulting carbon films also showed a remarkable increase with increased heat treatment temperature. The resulting carbon films developed from the modified PAN films had higher L_c and L_a than those developed from the original PAN film. It was established that cobalt catalyzes graphitization of amorphous carbon during pyrolysis. This modification not only promoted the growth of crystal size but also increased the close packing of the carbon basal planes. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2219–2225, 1999     

Effects of oxidation time on the structure and properties of polyacrylonitrile‐based activated carbon hollow fiber

Polyacrylonitrile (PAN) hollow fibers were pretreated with ammonium dibasic phosphate, then further oxidized in air, carbonized in nitrogen, and activated with carbon dioxide. The effects of oxidation time of PAN hollow fiber precursor on the microstructure, specific surface, pore size distribution, and adsorption properties of PAN‐based activated carbon hollow fiber (PAN‐ACHF) were studied in this work. Both of specific surface area and adsorption ratio to VB₁₂ reach maximums when PAN hollow fibers are oxidized for 5 h in air. The adsorption ratios for creatinine are all higher than 90% over all oxidation time. After 5 h of oxidation, the number of pores on the surface obviously increases, and the pore size is uniform. After 7 h of oxidation, the number of macropores in PAN‐ACHF increases. The dominant pore sizes of mesopores in PAN‐ACHF range from 2 to 5 nm. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Effects of the oxidation temperature on the structure and properties of polyacrylonitrile‐based activated carbon hollow fiber

Polyacrylonitrile (PAN) hollow fibers were pretreated with ammonium dibasic phosphate, oxidized in air, carbonized in nitrogen, and activated with carbon dioxide. The effects of the oxidation temperature of the PAN hollow fiber precursor on the microstructure, specific surface, pore size distribution, and adsorption properties of PAN‐based activated carbon hollow fiber (PAN‐ACHF) were studied. When PAN hollow fibers were oxidized at 270°C, because of drastic oxidation, chain scission occurred, and the number of pores within and on the surface of the resultant PAN‐ACHF increased, but the pores were just in the thinner region of the skin of PAN‐ACHF. The surface area of PAN‐ACHF reached a maximum when the oxidation temperature was 270°C. The adsorption ratios to creatinine were all higher than 90% at all oxidation temperatures, and the adsorption ratio to VB₁₂ reached a maximum (97%) at 230°C. The dominant pore sizes of the mesopores in PAN‐ACHF ranged from 2 to 5 nm. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 203–207, 2005     

Effects of activation temperature on the properties and structure of PAN‐based activated carbon hollow fiber

Polyacrylonitrile (PAN) hollow fibers were pretreated with ammonium dibasic phosphate, then further oxidized in air, carbonized in nitrogen, and activated with carbon dioxide. The effects of activation temperature of a precursor fiber on the microstructure, specific surface, pore‐size distribution, and adsorption properties of PAN‐based activated carbon hollow fibers (PAN‐ACHF) were studied in this work. After the activation process, the BET surface area of the PAN‐ACHF and surface area of mesopores in the PAN‐ACHF increased very remarkably and reached 1422 m² g^?1 and 1234 m² g^?1, respectively, when activation temperature is 1000°C. The adsorptions to creatinine and VB₁₂ of PAN‐ACHF were much high and reached 99 and 84% respectively. In PAN‐ACHF which went through the activation at 700°C and 800°C, the micropore filling mainly occurred at low relative pressures, multimolecular layer adsorption occurred with the increasing of relative pressure, and the filling and emptying of the mesopores by capillary condensation occurred at high relative pressures. But in PAN‐ACHF which went through the activation at 900°C, a mass of mesopores resulted in the large pore filling by capillary condensation. The dominant pore sizes of mesopores in PAN‐ACHF are from 2 nm to 5 nm. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3778–3783, 2006     

NaOH催化水蒸气活化制煤基活性炭和氢气

在NaOH的催化作用下,通过水蒸气活化法制备了神府煤基活性炭和H2。探讨了NaOH/煤质量比、活化时间、活化温度等工艺条件对活性炭性能和H2产量的影响。结果表明,在活化温度为700℃,NaOH/煤质量比为0.5,单元活化时间为10 min的工艺条件下,可以制得碘值为635 mg/g,亚甲基蓝值为280 mg/g的活性炭,此时H2产量约17.9 mmol/g煤。     

煤焦与CO2及水蒸气气化特性研究进展

为了深入系统的研究煤焦与CO2及水蒸气的气化反应特性,综述了国内外对煤气化的主要影响因素、煤焦与CO2及水蒸气气化反应动力学、煤的结构特性在气化过程中的变化及CO2气化与水蒸气气化反应活性对比等方面的研究进展,并进行了总结。     

Kinetic study of the dehydrogenation reaction in polyacrylonitrile‐based carbon fiber precursors during thermal stabilization

The kinetics of dehydrogenation reaction and the structural evolution in polyacrylonitrile precursor fibers during thermal stabilization in air have been studied by Fourier transform infrared spectroscopy. The results indicate that, with the progress of dehydrogenation, the absorbance of methylene groups (? CH₂? ) gradually decreases, whereas that of methine groups (?CH? ) gradually increases. The dehydrogenation reaction in the fibers is basically completed after 20‐min stabilization above 255°C. According to the Beer–Lambert law, the values of the absorbance for both ? CH₂? groups and the resulting ?CH? groups have been calculated and converted into the concentration fractions of ? CH₂? groups via the Lorentzian multipeak fitting. According to the principles of chemical kinetics, the dehydrogenation reaction has been determined as a pseudo‐second‐order reaction with an activation energy of 107.6 kJ mol^?1. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

CO_2活化生物质水解残渣制备活性炭的正交实验

以玉米秸秆酸水解残渣为原料、CO2为活化剂,制备了一系列活性炭,采用正交试验方法分析了原料颗粒大小、CO2/N2体积比、活化温度、活化时间4个因素对生物质水解残渣原料活性炭的比表面积、孔径和得率的影响。正交试验结果表明,活化温度和CO2/N2体积比是影响该类活性炭吸附性能的主要因素。制备的活性炭产品最大比表面积达到845.4m2/g,对应的制备工艺:原料颗粒50目、CO2/N2体积比1∶1、活化温度1000℃、活化时间210min。     

The effects of carbonization temperature on the properties and structure of PAN‐based activated carbon hollow fiber

Polyacrylonitrile (PAN) hollow fibers were pretreated with ammonium dibasic phosphate and then further oxidized in air, carbonized in nitrogen, and activated with carbon dioxide. The effects of carbonization temperature of PAN hollow fiber precursor on the microstructure, specific surface, pore‐size distribution, and adsorption properties of PAN‐based carbon hollow fiber (PAN‐CHF) and PAN‐based activated carbon hollow fibers (PAN‐ACHF) were studied in this work. After the activation process, the surface area of the PAN‐ACHF increased very remarkably, reaching 900 m² g^?1 when carbonization is 1000°C, and the adsorption ratios to creatinine and VB₁₂ of ACHF were much higher than those of CHF, especially to VB₁₂. The different adsorption ratios to two adsorbates including creatinine and VB₁₂ reflect the number of micropores and mesopores in PAN‐ACHF. The dominant pore sizes of mesopores in PAN‐ACHF are from 2 to 5 nm. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2155–2160, 2005     

Influence of activation temperature on the properties of polyacrylonitrile-based activated carbon hollow fiber

In this work, polyacrylonitrile hollow fiber was oxidized, carbonized, and activated by carbon dioxide into activated hollow carbon fiber. The effects of the activation temperature on the characteristics of the resulting activated hollow carbon fiber, including the mechanical properties, the surface area, and pore size distribution, were studied. The results show that by activating for 40 min at 800°C, the mechanical properties was better, the surface area was larger, and the pore size was distributed in three ranges. Higher activation temperature led to the decrease in the mechanical strength, the increase in the burn-off degree of the surface, the reduce of the portion of micropores, and the greatly broadening the pore size distribution. Lower activation temperature can only produce pleading on the surface of the fiber instead of open pores, due to the milder attack of CO₂. Therefore, the characteristics of the activated hollow carbon fiber can be controlled by the activation temperature. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1331–1336, 1998     

活性炭载体对TiO2/AC光催化降解苯酚影响研究

分别以典型煤基活性炭和椰壳活性炭为载体,采用溶胶-凝胶法制备了TiO2/AC复合光催化剂,采用低温氮气吸附、X射线衍射、扫描电镜等对其性能进行了表征,分析了活性炭载体对复合光催化剂性能的影响.结果表明:TiO2在椰壳活性炭载体上的负载率高于煤基活性炭,TiO2负载使椰壳活性炭的比表面积和微孔容明显减小,TiO2溶胶对微...     

Comparison about the structure and properties of PAN‐based activated carbon hollow fibers pretreated with different compounds containing phosphorus

Polyacrylonitrile (PAN) hollow fibers were pretreated with five different compounds containing phosphorus, including ammonium dibasic phosphate, ammonium dihydrogen phosphate, triammonium phosphate, phosphoric acid, and metaphosphoric acid, and then further oxidized in air, carbonized in nitrogen, and activated with carbon dioxide. The effects of different compounds containing phosphorus as pretreating agents on the properties and structure of the resultant oxidized hollow fibers, carbon hollow fibers, and activated carbon hollow fibers are discussed. Comparing the Brunaner‐Emmett‐Teller (BET) surface area of PAN‐activated carbon hollow fibers (ACHF) pretreated with five different compounds, ammonium dibasic phosphate > triammonium phosphate > ammonium dihydrogen phosphate > phosphoric acid > metaphosphoric acid, and the surface area of mesopores in PAN‐ACHF pretreated with ammonium dibasic phosphate reaches maximum, 174 m² g^?1. The adsorption ratio to mesomolecule adsorbate, VB₁₂, of PAN‐ACHF pretreated with ammonium dibasic phosphate also reaches maximum, 97.7 wt %. Moreover, the dominant pore sizes of PAN‐ACHF range from 2 to 5 nm in diameter. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 294–300, 2005     

An in situ Raman study of dimethyl carbonate synthesis from carbon dioxide and methanol over zirconia

In situ Raman spectroscopy has been used to investigate the mechanism of dimethyl carbonate (DMC) synthesis via the reaction of methanol with carbon dioxide over zirconia. Methanol adsorption leads to the appearance of adsorbed methoxide groups, whereas CO₂ adsorption leads to the formation of carbonate species. Monomethyl carbonate species, (CH₃O)COO(Zr)₂, are formed by the reaction of methoxide and monodentate carbonate species and DMC is formed via the further reaction of monomethyl carbonate species with methanol. This sequence is supported by evidence that DMC decomposition on zirconia proceeds via the reverse of the proposed mechanism.     

Partial gasification of lignite coke with steam in a rotary kiln for activated carbon production

Experiments on the partial gasification of lignite cokes with steam were carried out in a laboratory rotary kiln. The results showed that on the one hand it was possible to produce activated carbons with a pronounced mesopore volume from low-t3emperature coke. On the other hand, microporous carbons could be produced from higher-temperature cokes; in this case, higher reaction temperatures could be applied. The reaction times required to obtain uniform burnoff were nearly equal.     

Effect of steam and carbon dioxide pretreatments on methane decomposition and carbon gasification over doped-ceria supported nickel catalyst

Effects of steam (H₂O) and carbon dioxide (CO₂) pretreatments on methane (CH₄) decomposition and carbon gasification over doped-ceria supported nickel catalysts have been studied from 400 to 500 °C. The doped ceria employed were gadolinia-doped ceria and samaria-doped ceria. Results indicate that a drastic increase of both H₂O and CO₂ dissociation activities occurs as the temperature increases from 450 to 500 °C. The formation of the surface hydroxyl species during H₂O treatment inhibits the followed CH₄ decomposition. CO but no CO₂ was formed during CH₄ reaction after H₂O treatment. Carbon deposition during CH₄ decomposition is quite large but can be removed via gasification with afterward CO₂ treatment. However, some of the deposited carbon species is in a form which can not be removed with CO₂ treatment but can be removed with O₂ treatment. And, higher values of the oxygen-ion conductivity and the density of the surface oxygen vacancies lead to higher activities for all dissociation and decomposition reactions.     

改性蜂窝状活性炭吸附二氧化碳和氮气的热力学

蜂窝状活性炭具有较高的比表面积、多孔道、压降低、吸脱附速率快、不易堵塞等优点,因此被认为是捕集烟道气中CO₂重要吸附材料。选用蜂窝状煤基和椰壳两种活性炭吸附剂,采用磁悬浮热天平分别测定了CO₂和N₂的吸附等温线。采用1 mol·L^-1 K₂CO₃对蜂窝状活性炭材料进行浸渍改性,提高在低二氧化碳分压下的CO₂吸附性能。采用Langmuir、multi-site Langmuir和Virial 3种模型对吸附平衡数据进行拟合,得出热力学参数,为后续吸附工艺优化设计提供基础数据。结果表明在实验范围内3种模型均能对实验测量的等温线进行较好的拟合,Langmuir模型总体拟合效果最好。     

Theoretical analysis and experimental study on SO2 adsorption onto pistachio‐nut‐shell activated carbon

The adsorption study of SO₂ onto the activated carbon prepared from pistachio‐nut shell was studied theoretically and experimentally. A single‐particle sorption model known as concentration‐dependent surface diffusivity micropore, surface and macropore diffusion control model incorporating micropore, macropore and surface diffusions, together with a nonlinear isotherm at the micropore mouth, has been derived and solved by a finite difference method. The effects of different types of nonlinear isotherms and concentration dependent surface diffusivities have been thoroughly studied. The effects of adsorbate concentration and temperature on adsorption were studied experimentally. Good agreement was found between the model predictions and the experimental results. The value of the tortuosity factor and the extracted diffusion coefficients obtained are consistent with their corresponding values reported. © 2008 American Institute of Chemical Engineers AIChE J 2009     

活性炭负载纳米二氧化钛对水体中砷的去除

采用批处理吸附实验,研究了颗粒活性炭和粉末活性炭负载纳米二氧化钛对水体中砷的去除效果及其初步机理。X射线衍射表征两种活性炭负载纳米二氧化钛后饱和吸附As(Ⅴ)和As(Ⅲ)前后的晶体结构图谱表明,其对砷的吸附属于表面吸附。结果说明,活性炭负载纳米二氧化钛便于纳米材料的回收,是发挥纳米二氧化钛除砷效果的重要措施。