Study of the adsorption properties of a natural Hungarian mordenite and its ion-exchanged derivatives

The texture and adsorption properties of a natural, Hungarian mordenite were investigated by electron microscopy and BET adsorption measurements. The properties of the ion-exchanged adsorbents were characterized by CO₂ and SO₂ isotherms. The measurements were evaluated on the basis of the pore-filling theory of Dubinin. We have found that at 20°C the H⁺-form of mordenite interacts preferably with CO₂, while on the Na⁺- and Ca²⁺-derivatives stronger adsorption of SO₂ takes place. This fact accounts for their applicability as selective adsorbents.

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, . CO₂ SO₂. . , 20°C H⁺- CO₂, Na⁺- Ca²⁺- SO₂ . .

     

Adsorption characteristics of synthesized mordenite membranes

Nitrogen adsorption at 77 K was measured for a self-supporting mordenite membrane synthesized on and detached from, a polytetrafluoroethylene (PTFE) substrate, and for a simultaneously formed powder. The adsorption by the membrane saturated an amount which was about half that found for adsorption by the powder. To examine this difference in adsorption characteristics, both of powder and membrane were measured for adsorption for water, methanol,n-hexane andtert-butyl alcohol. For methanol,n-hexane andtert-butyl alcohol, the powder and membrane both showed the same adsorption behavior as for nitrogen. When water molecules were adsorbed, however, there was no difference in saturated adsorption amount between powder and membrane, suggesting the presence of deformed pores in the rectangular crystal layer of the mordenite membrane. The deformed pores are assumed to occur as gaps among crystallites which displaced along theab planes of the rectangular crystals, forming the rectangular crystal layer. The channel bonding sites resulting from such displacement were found to serve as pore walls against adsorbable molecules which have a cross-sectional area greater than that of the water molecule. and so to hinder their entrance into the deformed pores. X-ray diffraction analysis revealed that the rectangular crystals have no periodic, continuous structure along thec-axis; they show a slight distortion of the crystallite shift from the plane perpendicular to thec-axis.     

Adsorption characteristics of synthesized mordenite membranes

Nitrogen adsorption at 77 K was measured for a self-supporting mordenite membrane synthesized on and detached from, a polytetrafluoroethylene (PTFE) substrate, and for a simultaneously formed powder. The adsorption by the membrane saturated an amount which was about half that found for adsorption by the powder. To examine this difference in adsorption characteristics, both of powder and membrane were measured for adsorption for water, methanol,n-hexane andtert-butyl alcohol. For methanol,n-hexane andtert-butyl alcohol, the powder and membrane both showed the same adsorption behavior as for nitrogen. When water molecules were adsorbed, however, there was no difference in saturated adsorption amount between powder and membrane, suggesting the presence of “deformed pores” in the rectangular crystal layer of the mordenite membrane. The deformed pores are assumed to occur as gaps among crystallites which displaced along theab planes of the rectangular crystals, forming the rectangular crystal layer. The channel bonding sites resulting from such displacement were found to serve as pore walls against adsorbable molecules which have a cross-sectional area greater than that of the water molecule. and so to hinder their entrance into the deformed pores. X-ray diffraction analysis revealed that the rectangular crystals have no periodic, continuous structure along thec-axis; they show a slight distortion of the crystallite shift from the plane perpendicular to thec-axis.     

Thermogravimetric characteristics of barbituric acid and some of its derivatives

The thermolysis curves of barbituric acid and some of its derivatives have been determined. Barbituric acid, violuric acid and dilituric acid form hydrates while 1,3-dimethylvioluric acid and barbital are anhydrous. Barbital and 1,3-dimethylvioluric acid sublime before decomposition. The differential thermal analysis for dilituric acid showed a sharp exotherm at 190° indicating a violent explosion.     

甲苯在多级孔丝光沸石上的吸附平衡和吸附动力学

为了考察多级孔丝光沸石中介孔的存在对丝光沸石吸附平衡和动力学的影响,选择甲苯分子作为探针分子,对其在具有不同介孔孔隙度的多级孔丝光沸石上的吸附等温线和吸附动力学曲线进行了测试。结果表明,甲苯在多级孔丝光沸石上的吸附等温线可以很好地用双位Toth吸附模型进行描述,由拟合参数以及亨利常数（K_H）和初始吸附热（Q_st）的计算得知,相对于微孔丝光沸石,介孔的引入增大了甲苯在丝光沸石内的吸附量,但减弱了甲苯与沸石表面的相互作用力;另外,甲苯在多级孔沸石表现出高的吸附速率,并随介孔孔隙度的增加而增大,反映了沸石内介孔的存在可有效促进沸石的传质能力。     

Adsorption of lanthanides on mordenite from nitrate medium

The adsorption of lanthanides (except for Pm) on mordenite was investigated under various solution conditions of nitrate ion concentrations ([NO*3]: 0.001-2 mol/dm3) and total lanthanide concentrations (0.0005 mol/dm3). Solutions of lanthanide nitrates were equilibrated with zeolite samples at 296 K. A concave tetrad effect was evident in the change of logK d values within the lanthanide series and an explanation by a comparison of covalence in Ln-O bonds existing in triple bond Al-O(1/3Ln)-Si species found in the zeolite phase and in Ln(H2O)3+x or Ln(NO3) n-3 n complexes formed in the aqueous phase is presented. The decreasing trend in C1 and C3 coefficients, which are the function of E1 and E3 Racah f-interelectron repulsion parameters, is evidence of the magnification of covalence in Ln-O bond in the series triple bond S-iO(1/3Ln)-Al triple bond 相似文献   

Evaluation of cesium sorption on natural mordenite

The kinetic and equilibrium sorption behaviors of Cs⁺ on mordenite, a zeolite which can sorb cesium well, were investigated by using the batch method. Cesium-137 and the stable CsNO₃ were used as tracer and carrier to study the influences on Cs⁺ sorption behaviors by changing Cs⁺ initial concentration, pH value, particle size of mordenite and experimental temperature. The equilibrium was reached in 3 days and the saturated amount of cesium sorbed is about 0.19 kg Cs/kg NM. The sorption data at 25°C and 90°C were fitted to Freundlich sorption model and nonlinear isotherms were found. However, linear isotherm was applicable with a Cs⁺ initial concentration less than 10^–3M. The decrease of Cs⁺ sorption at elevated temperature suggested the sorption reaction was exothermic. The use of centrifugation to separate the liquid from solid phases in traditional batch techniques was not suitable to the kinetic experiment of Cs sorbed by mordenite for lower concentrations.     

Recationation and adsorption parameter adjustment for natural mordenite

Partially dealuminated forms of natural mordenite after alkali treatment have been used to show that the adsorption rates are increased and the adsorption energies are decreased for various substances as the Si/Al ratio increases. For that reason, there is a maximum in the performance of the modified mordenite specimens as the adsorption energy decreases in the purification of air from CO₂ and in the separation of the major components of air (O₂+N₂). L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 03039, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 36, No. 2, pp. 126–131, March–April, 2000.     

Cesium sorption behavior of a mordenite type synthetic zeolite and its modified form obtained by acid treatment

A locally produced mordenite type synthetic zeolite and its modified form obtained by the treatment with dilute hydrochloric acid were tested for their cesium uptake characteristics. The two zeolites were compared with other commercially available synthetic zeolites with respect to their ability to sorb radiocesium from dilute nitric acid solution. The effects of the changes in the composition of the solution including the concentration of nitric acid, sodium and cesium on the uptake of cesium were investigated. The results can be used in the removing processor radiocesium from different types of nuclear plant effluents by these zeolites.     

A study of dachiardite,a natural zeolite of the mordenite group

Dachiardite of the composition (Na_2.21K_0.35Ca_0.66Mg_0.10)[Al_4.41Si_19.67O₄₈] · 11.8H₂O (Tedzami, Georgia), a natural zeolite of the mordenite group, was studied using a Tian-Calvet high-temperature microcalorimeter. Melt solution calorimetry was used to determine the enthalpy of formation of the mineral from oxides (?613±45 kJ/mol) and elements (?26595±50kJ/mol). The obtained experimental and literature data were used to calculate the Gibbs energy of formation of dachiardite from elements. The thermodynamic properties of the hypothetical limiting members of the isomorphous series (Na, K, Ca)[Al₄Si₂₀O₄₈] · 13H₂O were estimated.     

Thermochemical characteristics of phosphorous acid derivatives

Enthalpies of formation enthalpies of a series of phosphorous acid derivatives were estimated from the heat effects of their reactions. The collected thermochemical data was used to analyze, on the basis of the additive scheme, the experimental enthalpies of formation and vaporization of four-coordinate phosphorus derivatives. Original Russian Text E.V. Sagdeev, Yu.G. Safina, 2007, published in Zhurnal Obshchei Khimii, 2007, Vol. 77, No. 2, pp. 275–279.     

Adsorption of ammonia by sulfuric acid treated zirconium hydroxide

The adsorption of ammonia on Zr(OH)(4), as well as Zr(OH)(4) treated with sulfuric acid, were examined. The results show that treating Zr(OH)(4) with sulfuric acid leads to the formation of a sulfate on the surface of the material, and that the sulfate contributes to the ammonia adsorption capacity through the formation of an ammonium sulfates species. Calcination of Zr(OH)(4) decreases the ammonia adsorption capacity of the material and limits the formation of sulfate species. NMR and FTIR spectroscopy results are presented that show the presence of two distinct ammonium species on the surface of the material. The adsorption capacity of the materials is shown to be a complex phenomenon that is impacted by the surface area, the sulfur content, and the pH of the material. The results illustrate that Zr(OH)(4), which is known to adsorb acidic gases, can be modified and used to adsorb basic gases.     

Directed metallations of 4-ethylidenetetronic acid and its derivatives as a synthetic entry to natural 4-oxy-2-furanones

Lithium diisopropylamide (LDA) removes the α-proton from the O-methyl tetronic acid (2$\text{b}$) leading to the vinylic carbanion (12), whereas treatment of the trimethylsilyl derivative (14) with LDA, followed by reaction with aldehydes gives products resulting from both γ? and ε-addition; the directed metallations provide access to a range of 4-oxy-2-furanone derivatives found amongst natural products.     

2-Bromohexafluoroisobutyric acid and its derivatives

Summary 2-Bromohexafluoroisobutyric acid and its derivatives were prepared.     

Study of hydroisomerization of n-hexane on natural mordenite catalyst

A mordenite-containing rock sample from the Tokaj Mountains (Hungary) and its various forms modified by chemical treatment have been tested for catalytic properties during isomerization of n-hexane. Addition of Pt to the catalyst leads to a sharp decrease in the rate of cracking and in the rate of deactivation and this results in a catalyst of high selectivity for hexane isomers.

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(), , , , -. Pt , .

     

Electrochemical characteristics of anthrapyridone and its derivatives

A mechanism is proposed for the electrical reduction of anthrapyridone and its derivatives on a dropping mercury electrode in anhydrous dimethylformamide. Parallelism in the electrochemical behavior, under the indicated conditions, or anthrapyridone and anthraquinone derivatives was noted. A linear correlation of the half-wave potential with the calculated energies of the lower vacant molecular orbital by the Hückel MO LCAO method within the Pariser-Parr-Pople approximation was found. The half-wave potentials correlate satisfactorily with the enthalpies of the intramolecular hydrogen bond of the investigated compounds.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1386–1390, October, 1976.     

Adsorption of natural gas and its whole components on adsorbents

Adsorption of each component of natural gas on adsorbent prepared from petroleum coke was studied. At 25 °C and 3.5 MPa, adsorption capacity of the components of natural gas are as follows: C₃H₈, H₂S(0.980) > CO₂(0.691) > C₂H₆(0.160) > CH₄(0.136) > N₂(0.096) (g/g). For natural gas, adsorption capacity is 145.2 (mL/mL) and delivery capacity is 105.7 (mL/mL). One equation between adsorption capacity and boiling point of adsorbed gas was firstly generalized. The adsorption capacity of different component like O₂, N₂, CH₄, C₂H₆, CO₂, H₂S on adsorbents were predicted using the equation. The results fit well with the experimental data. The equation has significance in predicting the adsorption capacity for any component of natural gas. Charge-discharge tests were conducted 10 times, the result indicates that natural gas has significantly worse reversibility in adsorption and desorption in the adsorbent than that of CH₄. The contents of the components after 10 charge-discharge show that the adsorption capacity drop of natural gas is due to the irreversible adsorption of heavy or polar components like C₃H₈, H₂S.