Production of activated carbons from biodegradable waste materials as an alternative way of their utilisation

New carbonaceous adsorbents were prepared by means of direct, physical and chemical activation of corn cobs and cherry stones as well as coffee and tobacco industry waste materials. The effect of activation method on the textural parameters, acid-base character of the surface and sorption properties toward toxic gases of the materials obtained was tested. Depending on the precursor as well as method of preparation, the final products were micro/mesoporous activated carbons of surface area reaching to 1426 m²/g, showing largely different acid-base properties of the surface. The results obtained in our study have proved that a suitable choice of the activation procedure for industrial and agricultural biodegradable waste materials permits production of cheap carbonaceous adsorbents with very high sorption capacity towards nitrogen dioxide and hydrogen sulphide reaching to 83 mg NO₂/g_ads and 215 mg H₂S/g_ads, respectively.     

Selective sorption of water vapor from gas mixtures containing H<Subscript>2</Subscript>S,SO<Subscript>2</Subscript>, NO<Subscript>2</Subscript>, NO,and CO on KU-2 sulfonic styrene cation exchanger in different ion forms

Sorption of water vapor and some acid gases (H₂S, SO₂, NO₂, NO, and CO) on Ku-23-15/100 macroporous sulfonic cation exchanger in different ion forms and on commercial KSM silica gel and NaX artificial zeolite was studied under equilibrium and dynamic conditions. The equilibrium isotherms of water vapor sorption were measured for all the adsorbents examined. The mechanism of water sorption on the sulfonic cation exchanger was discussed.     

Comparison of Dinitrogen,Methane, Carbon Monoxide,and Carbon Dioxide Mass‐Transport Dynamics in Carbon and Zeolite Molecular Sieves

Equilibrium (based on Henry constants) and kinetic (based on relaxation‐time constants or rather macropore transport diffusivities) selectivities for commercial zeolite and carbon‐molecular‐sieve (CMS) adsorbents were compared. Adsorption isotherms were recorded at ?20°. The frequency‐response (FR) sorption‐rate spectra were determined in the range of ?78 and 70° at 133 Pa. In particles of a larger size than 1.0 mm, macropore diffusion governed the rate of sorption mass transport in both types of microporous materials. The differences in the intercrystalline diffusivities established the kinetic separation of the gases notwithstanding the essential importance of interactions in the micropores. Zeolites seem to be more advantageous for a dynamic separation of CO₂ and CH₄ than CMS 4A. With the CO₂ and CO pair, the CMS is characterized by short characteristic times which, together with a good separation factor, is a double advantage in a short‐cycle adsorption technology. Upon comminution of the carbon pellets, intercrystalline‐diffusion resistance can be completely removed by using CMS 4A adsorbent particles with a diameter smaller than 1 mm. The carbonization of spruce‐wood cubes resulted in an excellent carbon honeycomb structure, which seems to be ideal from a dynamic point of view for applications in short‐cycle adsorption‐separation technologies. In the development of adsorbents, the use of the FR method can be beneficial.     

Synthesis of Discrete CHA Zeolite Nanocrystals without Organic Templates for Selective CO2 Capture

Small-pore zeolites such as chabazite (CHA) are excellent candidates for the selective separation of CO₂; however, the current synthesis involves several steps and the use of organic structure-directing agent (OSDA), increasing their cost and energy requirements. We report the synthesis of small-pore zeolite crystals (aluminosilicate) with CHA-type framework structure by direct synthesis in a colloidal suspension containing a mixture of inorganic cations only (Na⁺, K⁺, and Cs⁺). The location of CO₂ molecules in the host structure was revealed by 3D electron diffraction (3D ED). The high sorption capacity for CO₂ (3.8 mmol g⁻¹ at 121 kPa), structural stability and regenerability of the discreate CHA zeolite nanocrystals is maintained for 10 consecutive cycles without any visible degradation. The CHA zeolite (Si:Al=2) reaches an almost perfect CO₂ storage capacity (8 CO₂ per unit cell) and high selectivity (no CH₄ was adsorbed).     

Sorption characteristics of uranium onto composite ion exchangers

The composite ion exchangers were tested for their ability to remove UO₂ ²⁺ from aqueous solutions. Polyacrylonitrile (PAN) composites having natural zeolite, clinoptilolite, and synthetic zeolite, zeolite X, were used as an adsorbents. The influences of pH, U(VI) concentration, temperature and contact time on the sorption behavior of U(VI) were investigated in order to gain a macroscopic understanding of the sorption mechanism. The optimum adsorption conditions were determined for two composites. The sorption behaviors of uranium on both composites from aqueous systems have been studied by batch technique. Parameters on desorption were also investigated to recover the adsorbed uranium.     

以催化裂化废催化剂为原料合成NaY分子筛的研究

针对催化裂化(FCC)废催化剂的回收利用问题,提出了一种废催化剂再利用的方法,即以FCC废催化剂为铝源,合成时只补充部分硅源,采用自制的高效NaY沸石导向剂,水热合成NaY分子筛。同时,以普通的化工原料合成了对比试样Y型分子筛。讨论了不同的FCC废催化剂预处理方式对合成产物性能的影响,发现以经过碱熔活化处理的废催化剂为原料合成的Y分子筛拥有更高的结晶度和纯度。采用X射线衍射、热分析、程序升温脱附法(NH3-TPD)和N₂静态容量吸附法对结晶产物和对比样品的晶体结构,热稳定性、酸性质、比表面积以及孔分布进行了表征。结果显示,以FCC废催化剂为原料完全可以合成出与普通原料性能接近的NaY分子筛。其BET比表面积可以达到615 m²·g^-1,孔体积可达0.38 cm³·g^-1,孔径集中在0.51 nm左右。     

Thermal behavior and evolved gases analysis of 1,2,4-triazole-3-one derivatives

In order to obtain a better understanding of thermal substituent effects in 1,2,4-triazole-3-one (TO), the thermal behavior of 1,2,4-triazole, TO, as well as urazole and the decomposition mechanism of TO were investigated. Thermal substituent effects were considered using thermogravimetry/differential thermal analysis, sealed cell differential scanning calorimetry, and molecular orbital calculations. The onset temperature of 1,2,4-triazole was higher than that of TO and urazole. Analyses of evolved decomposition gases were carried out using thermogravimetry–infrared spectroscopy and thermogravimetry–mass spectrometry. The gases evolved from TO were determined as HNCO, HCN, N₂, NH₃, CO₂, and N₂O.     

苯并噻吩在酸改性NaY分子筛上的吸附

以NaY分子筛为母体,通过柠檬酸、磷酸改性分别得到吸附剂NaY-C和NaY-P.采用SEM、XRD、XRF、N₂物理吸附及NH₃-TPD表征可知,柠檬酸改性后得到的NaY-C吸附剂介孔表面积增加,分子筛骨架结构保持不变.同时,磷酸改性使得NaY分子筛表面弱酸量减少强酸量增加,改性后所得吸附剂NaY-P的强酸量大于NaY-C.吸附实验表明,NaY-C和NaY-P均可完全脱除模拟油品中的苯并噻吩,同时NaY-C吸附剂对0^#柴油的脱硫能力优于NaY-P吸附剂.再生实验中NaY-C和NaY-P吸附剂对模拟油品的脱硫率由第一次的100%分别下降至第6次的91.97%和85.96%.由此可知,柠檬酸改性NaY分子筛所得NaY-C吸附剂的脱硫能力优于NaY-P,原因是吸附剂上的介孔更易于发生吸附脱硫.     

Thermoanalytical investigations on ion-exchanged Y-zeolites

NH₄Y and NH₄LaY-type zeolite catalysts were prepared by cyclic ion-exchange of a synthetic Linde Y-zeolite. The release of ammonia and water were followed by evolved gas analysis (automatic thermogastitrimetric equipment) as well as with a continuous selective water detector. The ion-exchangeability of NH ₄ ⁺ for La³⁺ on the zeolite was also investigated. The capacity of the NH₄Y-zeolite was found to be 3.60 mequiv./g calcined zeolite. After a three times repeated ion-exchange process, 88.9 % of the ammonia was replaced by lanthanum.     

Sorption and partial molar volumes of gases in poly(ethylene-co-vinyl acetate)

Sorption and dilation properties of polymer-gas systems involving poly(ethylene-co-vinyl acetate) and N₂, CH₄, or CO₂, have been investigated at pressures up to 50 atm at temperatures of 10–40°C. Sorption isotherms for low-solubility gases (i.e., CH₄ and N₂) can be described by Henry's law, and those for high-solubility gas (i.e., CO₂) by Flory-Huggins dissolution equation. Dilation isotherms are similar in contour to the corresponding sorption isotherms. From the obtained sorption and dilation data, partial molar volumes of the gases in the polymer were determined as a function of temperature. Thermal expansivity of dissolved CO₂ molecules was estimated at ca. 2.4 × 10^?3°C^?1 from the temperature dependence of partial molar volume. The expansivity is smaller than that of liquid CO₂ and larger than those of the polymer and organic liquids. © 1994 John Wiley & Sons, Inc.     

Sorption properties of activated carbons obtained from corn cobs by chemical and physical activation

The paper presents results of a study on obtaining activated carbon from common corn cobs and on its use as adsorbent for removal of pollution from liquid and gas phases. The crushed precursor was subjected to pyrolysis at 500 and 800?°C in argon atmosphere and next to physical or chemical activation by CO₂ and KOH respectively. The effect of pyrolysis conditions and activation method on the physicochemical properties of the materials obtained was tested. The sorption properties of the carbonaceous adsorbents obtained were characterized by determination of nitrogen dioxide and hydrogen sulphide sorption from gas stream in dry and wet conditions as well as by iodine and methylene blue removal from aqueous solution. The final products were microporous activated carbons of well-developed surface area varying from 337 to 1213 m²/g and showing diverse acid-base character of the surface. The results obtained in our study have proved that a suitable choice of the activation procedure for corn cobs permits production of cheap adsorbents with high sorption capacity toward toxic gases of acidic character as well as different pollutants from liquid phase.     

Current developments in CO2 hydrogenation towards methanol: A review related to industrial application

Regarding the still increasing CO₂ emissions and the accompanied imminent climate change, utilization of CO₂-containing exhaust gases is one of the major opportunities to lower CO₂ emissions while obtaining valuable products in parallel. Methanol as one of today's key platform chemicals can be industrially produced from these exhaust gases by heterogeneously catalyzed CO₂ hydrogenation. This review elaborates why the Cu/ZnO/Al₂O₃ catalyst is still the most promising candidate to catalyze CO₂ hydrogenation from exhaust gases to reduce CO₂ emissions in the short term. It emphasizes catalyst lifetime and deactivation as well as catalyst poisoning, which are significant factors considering the use of impurity-containing exhaust gases. Besides modifications of the Cu/ZnO system, completely different catalysts are discussed regarding their usability and comparability to the conventional Cu/ZnO/Al₂O₃ catalyst.     

NaX zeolite,carbon fibre and CaCl2 ammonia reactors for heat pumps and refrigerators

The key elements of solid sorption machines are the chemical compressors-adsorbers. Two categories of the solid sorption system are analyzed: adsorbents NaX zeolite, carbon fibre Busofit with NH₃, and complex combinations that undergo chemical reaction and physical adsorption (CaCl₂ + carbon fibre Busofit with NH₃).Two phase ammonia motion inside the adsorbent bed was checked. That accompanied NH₃/CaCl₂ solution redistribution between the cold and hot surfaces of the sorbent bed, resulting in a rich CaCl₂ concentration at the boundaries.Solid sorption heat pump and refrigerator technology utilizing heat pipe heat recovery with a condensing/evaporating refrigerant holds considerable promise for bivariant (space and domestic) applications due to the variable temperature and variable load capabilities of such machines.     

Pyrolysis mechanism of urazole by evolved gas analysis

In order to obtain a better understanding of thermal substituent effects in 1,2,4-triazole-3-one (TO), the thermal behavior of 1,2,4-triazole, TO, as well as urazole and the decomposition mechanism of TO were investigated. Thermal substituent effects were considered using thermogravimetry/differential thermal analysis, sealed cell differential scanning calorimetry, and molecular orbital calculations. The onset temperature of 1,2,4-triazole was higher than that of TO and urazole. Analyses of evolved decomposition gases were carried out using thermogravimetry–infrared spectroscopy and thermogravimetry–mass spectrometry. The gases evolved from TO were determined as HNCO, HCN, N₂, NH₃, CO₂, and N₂O.     

TG–MS–FTIR (evolved gas analysis) of kaolinite–urea intercalation complex

The products evolved during the thermal decomposition of kaolinite–urea intercalation complex were studied by using TG–FTIR–MS technique. The main gases and volatile products released during the thermal decomposition of kaolinite–urea intercalation complex are ammonia (NH₃), water (H₂O), cyanic acid (HNCO), carbon dioxide (CO₂), nitric acid (HNO₃), and biuret ((H₂NCO)₂NH). The results showed that the evolved products obtained were mainly divided into two processes: (1) the main evolved products CO₂, H₂O, NH₃, HNCO are mainly released at the temperature between 200 and 450 °C with a maximum at 355 °C; (2) up to 600 °C, the main evolved products are H₂O and CO₂ with a maximum at 575 °C. It is concluded that the thermal decomposition of the kaolinite–urea intercalation complex includes two stages: (a) thermal decomposition of urea in the intercalation complex takes place in four steps up to 450 °C; (b) the dehydroxylation of kaolinite and thermal decomposition of residual urea occurs between 500 and 600 °C with a maximum at 575 °C. The mass spectrometric analysis results are in good agreement with the infrared spectroscopic analysis of the evolved gases. These results give the evidence on the thermal decomposition products and make all explanation have the sufficient evidence. Therefore, TG–MS–IR is a powerful tool for the investigation of gas evolution from the thermal decomposition of materials and its intercalation complexes.     

Sorption and partial molar volume of gases in poly (dimethyl siloxane)

Sorption of N₂, O₂, Ar, CH₄, CO₂, C₂H₄, and C₂H₆ in poly (dimethyl siloxane) liquid and rubber and the dilation of the polymers due to sorption of the gases are studied at 25°C under pressures up to 50 atm. In the liquid, the sorption isotherms for low-solubility and high-solubility gases are described by Henry's law and the Flory–Huggins equation, respectively. Gas sorption in the rubber, which contains a 29 wt % silica filler, follows the dual-mode sorption model, though marked hysteresis is observed in the sorption of O₂ and CH₄. The dilation isotherms increase linearly or exponentially in both polymers with increasing pressure. Considering that gas molecules adsorbed into micropores of the filler particles do not participate in the dilation, partial molar volumes of the dissolved gases in the rubber are determined from data of sorption and dilation. The values are nearly equal to the partial molar volumes in the liquid (48–60 cm³/mol).     

Adsorption separation of carbon dioxide, methane and nitrogen on monoethanol amine modified B-zeolite

A new type of composite adsorbents was synthesized by incorporating monoethanol amine (MEA) into β-zeolite. The parent and MEA-functionalized β-zeolites were characterized by X-ray diffraction (XRD), N₂ adsorption, and thermogravimetric analysis (TGA). The adsorption behavior of carbon dioxide (CO₂), methane (CH₄), and nitrogen (N₂) on these adsorbents was investigated at 303 K. The results show that the structure of zeolite was well preserved after MEA modification. In comparison with CH₄ and N₂, CO₂ was preferentially adsorbed on the adsorbents investigated. The introduction of MEA significantly improved the selectivity of both CO₂/CH₄ and CO₂/N₂, the optimal selectivity of CO₂/CH₄ can reach 7.70 on 40 wt% of MEA-functionalized β-zeolite (MEA(40)-β) at 1 atm. It is worth noticing that a very high selectivity of CO₂/N₂ of 25.67 was obtained on MEA(40)-β. Steric effect and chemical adsorbate-adsorbent interaction were responsible for such high adsorption selectivity of CO₂. The present MEA-functionalized β-zeolite adsorbents may be a good candidate for applications in flue gas separation, as well as natural gas and landfill gas purifications.     

Heterogeneous Heck Reaction in Microemulsion with Palladium Supported Na‐Y Zeolites as Catalyst

Heterogeneous Heck reaction catalyzed by Pd (NH₃)₄ ²⁺‐Na‐Y zeolite in the presence of K₂CO₃ as the base has been carried out in an oil‐in‐water microemulsion based on Triton X10 at 80°C.     

Microporous Magnesium and Manganese Formates for Acetylene Storage and Separation

Acetylene sorption of microporous metal formates M(HCOO)₂ (M=Mg and Mn) was investigated. Measurements of acetylene sorption at 196, 275, and 298 K showed a Type I isotherm with quick saturation at low pressures, and 50–75 cm³ g^?1 uptake at 1.0 atm. The single‐crystal X‐ray structure analysis of the acetylene‐adsorbed metal formates revealed that acetylene molecules occupy two independent positions in the zigzag channels of the frameworks with a stoichiometry of M(HCOO)₂?1/3C₂H₂, which is consistent with the gas sorption experiments. No specific interaction except van der Waals interactions between the adsorbed acetylene molecules and the walls of the frameworks was found. Sorption properties of other gases, including CO₂, CH₄, N₂, O₂, and H₂, were also investigated. When the temperature was increased to 298 K, the amount of adsorbed acetylene was still above 60 cm³ g^?1 for Mg(HCOO)₂ and 50 cm³ g^?1 for Mn(HCOO)₂, whereas the uptake of other gases decreased substantially. The microporous metal formates may thus be useful not only for the storage of acetylene but also its separation from other gases at room or slightly higher temperatures.     

A Robust Porous Metal–Organic Framework with a New Topology That Demonstrates Pronounced Porosity and High‐Efficiency Sorption/Selectivity Properties of Small Molecules

A robust porous metal–organic framework (MOF), [Co₃(ndc)(HCOO)₃(μ₃‐OH)(H₂O)]_n ( 1 ) (H₂ndc=5‐(4‐pyridyl)‐isophthalic acid), was synthesized with pronounced porosity. MOF 1 contained two different types of nanotubular channels, which exhibited a new topology with the Schlafli symbol of {4².6⁵.8³}{4².6}. MOF 1 showed high‐efficiency for the selective sorption of small molecules, including the energy‐correlated gases of H₂, CH₄, and CO₂, and environment‐correlated steams of alcohols, acetone, and pyridine. Gas‐sorption experiments indicated that MOF 1 exhibited not only a high CO₂‐uptake (25.1 wt % at 273 K/1 bar) but also the impressive selective sorption of CO₂ over N₂ and CH₄. High H₂‐uptake (2.04 wt % at 77 K/1 bar) was also observed. Moreover, systematic studies on the sorption of steams of organic molecules displayed excellent capacity for the sorption of the homologous series of alcohols (C₁–C₅), acetone, pyridine, as well as water.