Dual pore-size sieving in a novel oxygenate-pillared microporous adsorbent for C6 alkane isomers separation

Adsorbents executing molecular sieving mechanisms for the efficient separation of n-hexane (C6) alkane isomers require delicate pore size control, but afford unsatisfactory single-component separations according to their branch degrees. Herein, we report a novel oxygenate-pillared microporous adsorbent, MoOFOUR-Co-tpb, ([Co(tpb)₂MoO₄], tpb = 1,2,4,5-tetra(pyridin-4-yl) benzene), with three gourd-shaped channels for dual pore-size sieving of C6 isomers. In particular, MoOFOUR-Co-tpb excludes 2,2-dimethylbutane, while 3-methylpentane (3MP) can enter one channel showing a high uptake of 82.6 mg g⁻¹, contrasting to the n-hexane (nHEX) adsorption by two channels (136 mg g⁻¹). This dual pore-size control strategy renders a record high equilibrium–kinetic combined selectivity for nHEX/3MP (30.2). Moreover, three- and five-component breakthrough experiments confirm the practical separation performances and cycling stability. Multiple theoretical simulations reveal the separation mechanism and adsorption sites.     

Nanocomposites from phenolic resin and various organo‐modified montmorillonites: Preparation and thermal stability

Phenolic resin (PF)/montmorillonite (MMT) nanocomposites have been successfully prepared using intercalative polymerization of resole‐type phenolic resins in montmorillonites modified by octadecylamine (C18), benzyldimethylhexadecylammonium chloride (B2MH), benzyltriethylammonium chloride (B3E), and benzyldimethylphenylammonium chloride (B2MP). X‐ray diffraction measurements and transmission electron microscope observations showed that clay platelets were partially exfoliated or intercalated after complete curing of the phenolic resins. The cured nanocomposites were named as modifier‐MP (MP means montmorillonite‐phenolic resin), for example, B3E‐MP. Thermogravimetric analysis showed that thermal decomposition temperatures (T_ds) of the cured nanocomposites B2MP‐MP (826 K), B3E‐MP (794 K), and B2MH‐MP (783 K) were much higher than those of C18‐MP (768 K) and cured phenolic resin (737 K). Therefore, thermal stability of the nanocomposites depends mainly on the chemical structure of the organic modifiers. B2MP‐MP possesses the highest T_d since B2MP contains both benzyl and phenyl groups, followed with B3E‐MP and B2MH‐MP whose modifiers contain only one benzyl group. This is attributable to favorable interaction between phenolic resin and organic modifiers containing benzene rings. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5336–5343, 2006     

Reactions of hexane and 3-methylpentane on HZSM-5 at moderate temperatures in liquid phase and gas phase [1]

The reactivity of 3-methylpentane (3MP) and hexane (H) on HZSM-5 at 120–160 °C changes from gas (H > 3MP) to liquid phase (3MP > H), as does product selectivity. The liquid phase reactivity ratio is similar on HZSM-5 and in trifluoromethanesulfonic acid (TFMSA), where the reaction involves initiation by oxidation to allyl cations. In both cases, olefins are intermediates, but do not appear in the products. Because hydride transfer catalysis is absent in the reaction of H and the steric requirements for hydride transfer are smaller than for cracking, the mechanism involving protonation of sigma bonds, as in liquid superacids, does not operate in zeolites. The H:3MP reactivity ratio does not measure steric constraints in cavities.     

Tuning the selectivity for ring-opening reactions of methylcyclopentane over Pt catalysts: A mechanistic study from first-principles calculations

Using density functional calculations, we studied the conversion of methylcyclopentane to its ring-opening products: branched hexanes [2-methylpentane (2MP), 3-methylpentane (3MP)], as well as unbranched n-hexane (nHx). We employed flat Pt(1 1 1) and stepped Pt(2 1 1) to describe terrace-rich large and defect-rich small Pt particles, respectively. On Pt(1 1 1), the barriers of all elementary steps for the paths leading to branched hexanes lie below 90 kJ mol^?1, while the formation of nHx features a barrier of 116 kJ mol^?1 in its C–C bond scission step. This higher barrier impedes the formation of nHx on Pt(1 1 1) and thus rationalizes the experimental observations that terrace-rich large Pt particles selectively produce branched hexanes. However, on Pt(2 1 1), the barrier of C–C scission for the formation of nHx decreases to 94 kJ mol^?1, thus implying enhanced formation of nHx over the defects, in agreement with the essentially statistical product distribution observed with defect-rich small Pt particles.     

Untersuchungen zur Sulfochlorierung von Paraffinen. IX. Substitutionsregelmäßigkeiten bei der Sulfochlorierung verzweigter Paraffine

Studies on Sulphochlorination of Paraffins. IX. Regularities of the Sulphochlorination of Branched-chain Paraffins In the cases of 2-methylbutane and 2-methylpentane the formation of tertiary sulphochlorides in the sulphochlorination of the parent hydrocarbons could be established by means of ¹³C-n.m.r.-spectroscopy. The relative rates of the various C H-bonds in 2-methylbutane, 2-methylpentane and 3-methylpentane in the sulphochlorination reaction were determined. The relative rates of the tertiary C H-bonds in the sulphochlorination were considerably lower than the corresponding values for the chlorination of the branched-chain paraffins.     

Geometric and promoting effects of methylcyclopentane conversion over alkaline Pt/L zeolites

The hydrogenolysis of methylcyclopentane (MCP) has been used as a test reaction to analyze geometric and promoting effects in Pt catalysts supported on alkaline L zeolites. It has been observed that the production of 3-methylpentane (3MP) over these catalysts is significantly higher than over other Pt catalysts. Based on the micro-geometry of the system, we propose that collimating (geometric) effects play an important role in hydrocarbon reactions on these catalysts. On the other hand, the increased activity exhibited by the KL zeolite-supported catalysts relative to SiO₂-supported catalysts might indicate that promoting effects are also operative.     

Reforming of C6 Hydrocarbons Over Model Pt Nanoparticle Catalysts

Size-controlled model Pt nanoparticle catalysts, synthesized by colloidal chemistry, were used to study the hydrogenative reforming of three C₆ hydrocarbons in mixtures with 5:1 excess of H₂: methylcyclopentane, n-hexane and 2-methylpentane. We found a strong particle size dependence on the distribution of different reaction products for the hydrogenolysis of methylcyclopentane. The reactions of 50?Torr methylcyclopentane in 250?Torr H₂ at 320 °C, using 1.5 and 3.0 nm Pt nanoparticles produced predominantly C₆ isomers, especially 2-methylpentane, whereas 5.2 and 11.3 nm Pt nanoparticles were more selective for the formation of benzene. For the hydrogenolysis of n-hexane and 2-methylpentane, strong particle size effects on the turnover rates were observed. Hexane and 2-methylpentane reacted up to an order of magnitude slower over 3.0 nm Pt than over the other particle sizes. At 360 °C the isomerization reactions were more selective than the other reaction pathways over 3.0?nm Pt, which also yielded relatively less benzene.     

Side chain functional carbazole-fluorene electroactive polymers: Optical,electrochemical properties,antimicrobial activity and thin film morphologies

A new electroactive polymer based on fluorene and carbazole moieties with double bond side chain (MP25) was synthesized and then double bond at the side chain was functionalized with  COOH and  Si(OEt)₃ as ITO/glass compatible groups. Electrochemical and optical properties of the polymers were elucidated with cyclic voltammetry (CV), ultraviolet–visible absorption (UV–Vis), and photoluminescence (PL) spectroscopy. It was observed that all polymers absorbed only the UV region and emitted blue light. By using CV, HOMO values were found as approximately 5.45 eV. According to AFM results, when the rough MP25 polymer thin film was modified with ITO/glass compatible groups, more uniform and smoother polymer thin films were obtained. Thermogravimetry analyses (TGA) shown that the MP25-Si and MP25-COOH were stable against thermo-oxidative decomposition. The weight loss of MP-25-Si was found to be only %23 at 700°C. Additionally, antimicrobial activity of MP25 polymers was also investigated. According to test results, all polymers were found to have antimicrobial activity against C.albicans.     

Phosphorescence emission from poly(di-n-hexylsilane) in a glass: Temperature dependence and optically detected magnetic resonance (ODMR) spectra

The low-temperature steady-state phosphorescence spectrum of poly(di-n-hexylsilane) (PDHS) in a 3-methylpentane (3MP) glass at 1.5 K has been measured. The temperature dependence of the phosphorescence decay was determined and zero-field optically detected magnetic resonance (ODMR) experiments were performed. Evidence of at least two distinct emitting species was found. A narrow phosphorescence spectrum with no distinct vibronic structure was observed for PDHS and interpreted as indicating a delocalized triplet state. The ODMR spectrum is dependent on the detection wavelength, indicating that the triplet splittings are sensitive to the conformation and local environment of the polysilane chains. The phosphorescence disappears completely above 30 K. This is attributed to the presence of a dissociative triplet state.     

Preparation of hybridizing zeolitic imidazolate frameworks with carboxymethylcellulose for adsorption separation of n-hexane/3-methylpentane

A novel ZIF-8-CMC hybrid material was fabricated from the hybridization of ZIF-8 and carboxymethylcellulose (CMC) by impregnation method for n-hexane/3-methylpentane separation. The surface properties of ZIF-8 were tailored by introducing CMC into ZIF-8 nanoparticles. In this work, adsorption separation of n-hexane (nHEX) and 3-methylpentane (3MP) on ZIF-8-CMC were investigated by batch vapor-phase adsorption and liquid-phase breakthrough adsorption. The adsorption selectivity of nHEX/3MP reversed from preferable adsorption of nHEX to preferable adsorption of 3MP upon the increasing of CMC containing in the hybrid materials. As the temperature increases, the adsorption amounts of nHEX and 3MP decrease. With the increasing of CMC contents, the nHEX uptake decreased, the uptake capacity of 3MP increased gradually. For liquid-phase breakthrough adsorption, the dynamic adsorption capacity of nHEX also decreased with the increasing of temperature.     

Anion Exchange Resins as Effective Sorbents for Acidic Dye Removal from Aqueous Solutions and Wastewaters

Purification of wastewaters, particularly those containing dyes, has become increasingly important. The aim is to avoid a potential threat to the environment. Various sorbents have been used in the treatment of wastewaters contaminated by the Acid Orange 7 dye (AO7). In this article, the three anion exchange resins–weakly basic (Lewatit MonoPlus MP 62), intermediate (Lewatit MonoPlus MP 64), and strongly basic (Lewatit MonoPlus MP 500) were applied for AO7 removal from the aqueous solutions and wastewater. The most effective anion exchanger in wastewater purification proved to be Lewatit MonoPlus MP 500. AO7 sorption was not affected by the presence of Na₂SO₄ and CH₃COOH even at relatively high concentrations. The dye retentions were almost unchanged in the presence of non-ionic and anionic surfactants. AO7 sorption by Lewatit MonoPlus MP 62, MP 64, and MP 500 sharply decrease when the cationic surfactant is present in the solution. The monolayer adsorption capacity (Q₀ ) for MP 62 was found to be 79.9 mg/g at 25°C. At 45°C this value was almost ten times higher (769.5 mg/g). The increase of Q₀ values from 568.5 to 896.8 mg/g for MP 64 and from 979.0 to 1004.4 mg/g for MP 500 was observed with the rise in temperature. The optimal desorption conditions were found as follows: 1 M KSCN in 80–90% methanol for MP 62 (95–100% desorption) and MP 64 (～88% desorption) as well as 1 M HCl in 90% methanol for MP 500 (87% desorption).     

The hydrogenolysis of methylcyclopentane on platinum model catalysts: Particle size effect due to a reaction occurring at the phase boundary metal-support

The hydrogenolysis of methylcyclopentane at 520 K on platinum model catalysts was studied and the mechanism of this reaction investigated. Catalysts of low metal dispersion (<0.15) were prepared by high-vacuum evaporation of platinum onto thin films of amorphous alumina. After annealing at 770 K in air and hydrogen treatment at 520 K the mean size of the Pt particles was about 10 nm as determined by electron microscopy. On these catalysts the reaction products are mainly 2-methylpentane and 3-methylpentane and only 9–14% n-hexane is formed, as is to be expected for large Pt particles. On top of these catalysts a thin layer of Al₂O₃ (0.3 nm mean thickness) was then deposited in order to reduce the surface area of platinum in relation to the phase boundary platinum/alumina. Thereafter a decrease of the catalytic activity, as well as a shift in the product distribution, was observed. The n-hexane content was significantly enhanced (up to 22%) and the ratio of the three products was comparable to that usually obtained with Pt catalysts of higher dispersion. This result supports a reaction model which consists of two parallel reactions (i) occurring on the platinum surface and producing mainly 2-methylpentane and 3-methylpentane and (ii) occurring on the phase boundary platinum/support and producing additional n-hexane.     

Syntheses of cyclic poly(lactones) by zwitterionic ring opening polymerization catalyzed by N‐heterocyclic carbene

Synthesis of cyclic biopolymers from renewable monomers remains a big challenge because of lack of efficient catalysts. The organocatalyst of N‐heterocyclic carbene (NHC), (+)‐1‐methyl‐3‐menthoxymethyl imidazol‐2‐ylidene, is used to prepare cyclic polylactones including poly(ε‐caprolactone) (poly(ε‐CL)), poly(δ‐valearolactone) (poly(δ‐VL)), and poly(ε‐caprolactone‐co‐δ‐valearolactone) (poly(ε‐CL‐co‐δ‐VL)) via zwitterionic ring opening polymerization. The NHC catalyst is founded a highly efficient organic catalyst for the polymerization. The resulting cyclic polymers show a melting temperature (T_m) in a range of 20–60°C, which is dramatically lower than the T_m of cyclic poly(lactide) (T_m = 120–150°C). The resulting copolymer, cyclic poly(ε‐CL‐co‐δ‐VL) owns high molecular weight comparing with corresponding linear poly(ε‐CL‐co‐δ‐VL) produced by other catalysts. The synthesized cyclic homo and copolymers were characterized by ¹H‐, ¹³C‐NMR spectroscopy, gel permeation chromatography, differential scanning calorimetry–thermogravimetric analysis and matrix‐assisted laser desorption ionization‐time of flight mass spectrometry. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Diffusion Properties of Tm3+ in Congruent LiNbO3 Crystal

Diffusion properties of Tm³⁺ in congruent LiNbO₃ crystal have been investigated, together with other two related issues, i.e., Tm³⁺‐doping contribution to refractive index of LiNbO₃ substrate and Li out‐diffusion. Four X‐cut and four Z‐cut congruent LiNbO₃ substrates locally coated with 15–31 nm‐thick Tm‐metal films were annealed in surrounding air under different temperatures of 1030°C–1130°C for different durations of 20–70 h. After anneal, refractive index at Tm³⁺‐doped and Tm³⁺‐free parts of crystal surface was measured at the wavelengths of 1311 and 1553 nm and surface Li₂O contents were evaluated from measured refractive index. The results show that Tm³⁺ doping has a weak effect on substrate index and a small contribution to index increment in waveguide layer in comparison with Ti⁴⁺‐ or Zn²⁺ doping. The Li₂O content at the Tm³⁺‐doped surface equals that at the Tm³⁺‐free surface. The Li out‐diffusion depends mainly on the diffusion temperature. Below 1100°C, the Li out‐diffusion is not measurable. At 1130°C, a 30‐h diffusion procedure may cause 0.2–0.3 mol% slight loss of Li₂O content. Secondary ion mass spectrometry was used to study the Tm³⁺ diffusion properties. The results show that the diffused Tm³⁺ ions in all samples follow a complementary error function profile. From measured Tm³⁺ profiles, characteristic diffusion parameters such as diffusivity, diffusion constant, activation energy, solubility, solubility constant, and heat of solution were obtained and discussed in comparison with the case of Er³⁺ diffusion. In comparison with Er³⁺ diffusion, the Tm³⁺ diffusion shows similar anisotropy and temperature dependence of solubility. In the aspect of diffusivity, under lower temperature the Tm³⁺ has a lower diffusivity than the Er³⁺, and their diffusivity difference reduces with the increased temperature and becomes null at 1130°C.     

Experimental and fundamental critical analysis of diffusion model of airflow drying

Scientific literature of agromaterial drying present contradictory conclusions in terms of the kinetic effect of airflow velocity. Some authors confirmed that it does not trigger any modification of drying, while some articles tried to establish empirical models of the effective diffusivity D_eff versus the airflow velocity, what is fundamentally erroneous. By analyzing internal and external transfer phenomena, this research aimed at recognizing that once air velocity is higher than a critical airflow velocity (CAV), the internal transfers become the limiting phenomenon. CAV depends on the effective diffusivity and the product size. It was calculated in the cases of two studied raw materials (apple and carrot), differently textured by instant controlled pressure drop (DIC). Values of CAV greatly depend on diffusivity of water within the matrix. At temperature T?=?40°C, they were 1?m/s for untreated carrot and 2.1?m/s for DIC-textured carrot, whose D_eff values were 1.31 and about 3?×?10^?10?m²/s, respectively. Also, at temperature T?=?40°C, they were 2.1?m/s for untreated apple and 3?m/s for DIC-textured apple, whose D_eff were 1.4 and about 10.4?×?10^?10?m²/s, respectively.     

Sorption of low molar mass silicones in silicone elastomers

Elastomers based on polydimethylsiloxane (PDMS) are used as insulating material in outdoor electrical power applications. It is believed that migration of small molecule PDMS species plays an important role in the recovery of hydrophobicity of oxidized or polluted PDMS elastomer surfaces. This paper reports data on diffusivity and solubility of low molar mass PDMS liquids in PDMS rubbers (8000 < M _c < 16,000 g/mol) obtained by sorption measurements. It was found that the diffusivity (D) of linear PDMS liquids was approximately independent of the concentration of penetrant and that in the molar mass range 400 < M _c < 18,000 g/mol it decreased with molar mass (M _c) of the diffusing liquid according to D α M _c^−0.8. Theory and previous data for other oligomers and elastomers predict that D is proportional to M⁻¹. Linear PDMS liquids of lower molar mass exhibited a stronger molar mass dependence. The diffusivity of a given PDMS liquid increased with increasing elastomer crosslink density. The activation energy of the diffusivity was constant at 15.5 ± 2 kJ/mol for linear PDMS liquids of M _c larger than 1000 g/mol⁻¹ with only a negligible influence of network density and filler content. The activation energy of the lowest molar mass penetrant was considerably lower, 6 to 7 kJ/mol. The solubility increased markedly with decreasing molar mass of the penetrant and with decreasing elastomer crosslink density.     

Species Recognition from Postpharyngeal Gland Contents of Ants of the Cataglyphis bicolor Group

The Cataglyphis bicolor group of species of desert-dwelling ants, difficult to identify from morphological features alone, can be readily recognized by the contents of their postpharyngeal glands. Analysis by linked gas chromatography–mass spectrometry of glands from colonies identified only by code numbers showed in all samples straight and branched-chain alkanes and linear alkenes. C. viaticus, C. bicolor, and C. savignyi, the three species most difficult to distinguish morphologically, each contained distinctly different patterns of hydrocarbons, as illustrated by cluster analysis. The 16 most abundant hydrocarbons in the whole group of samples were selected and plotted as windrose diagrams. The differences in the windroses have more visual impact than gas chromatograms of the same data. The only case where there was any similarity was that between C. bicolor and C. diehlii, and even there the resemblance was not close. C. bombycinus is a sympatric species but is recognized as not belonging to the bicolor group by its different mandibular gland substances. It also was easily distinguished by its postpharyngeal gland contents from the other species.     

Dufour Gland Contents of Ants of the Cataglyphis bicolor Group

The species of desert-dwelling ants of the Cataglyphis bicolor (Hymenoptera: Formicidae) group are difficult to distinguish by morphological features. Analysis of the secretion from the Dufour glands of workers of a number of colonies was undertaken to see if it provided a clear test of species. Linked 6c-ms showed in all samples straight and branched-chain alkanes, linear alkenes, ketones, aldehydes, acetates, and a group of C₂₂ to C₂₈ esters not previously identified in this genus. Contents of the Dufour glands of C. savignyi from Tunisia and Egypt were similar, and comprised straight and branched-chain alkanes, alkenes and small amounts of esters. C. bicolor from Tunisia contained compounds similar to C. savignyi but was distinguished from the latter by larger amounts of the esters. The major compound in the glands of C. viaticus was tridecane, in contrast to the pentadecane of other species. It also contained a branched alkane, 3-methyltridecane as a major component. Branched-chain esters and a wide variety of acetates were also found in this species. C. diehlii had a limited range of compounds, with branched alkanes almost completely absent and high proportions of pentadecene and dodecyl acetate. C. bombycinus, a sympatric species, but recognized as not belonging to the bicolor group by its different mandibular gland substances, was notable in having butanoate esters in its Dufour glands. Despite these differences among species, both the great variability of individuals from a single colony and the among between conspecific colonies make species diagnosis from a few individuals difficult, in contrast with postpharyngeal glands, which, as recently reported, give a clearer indication of species.     

Laboratory extraction of cottonseed with various petroleum hydrocarbons

Summary Solvent extraction of cottonseed with various hydrocarbons in the C₅ to C₇ range was studied to determine comparative yields and quality of oil produced with pure and commercial hydrocarbon solvents. The solvents used were Pure Grade (minimum 99 mol per cent purity) isopentane, normal pentane, cyclohexane, normal heptane, and benzene; Technical Grade (minimum 95 mol per cent purity) neohexane, diisopropyl, 2-methylpentane, 3-methylpentane, normal hexane, methylcyclopentane, and a 90 mol per cent cyclopentane; and Commercial Grade normal pentane, isohexanes, normal hexane, isoheptanes, and normal heptane. The effects of precooking the seeds and of the inclusion of hulls on yield and color of extracted oil were determined. Yields and colors of crude oils from cottonseed with both high and intermediate free fatty acid content were studied, and characteristics of the oils determined and compared. Refining losses, refined colors, and bleach colors of oils extracted with various hydrocarbons were compared. Color comparisons were made with a Gardner Color Comparator and a Fisher Electrophotometer. Other test methods used were modifications of official A.O.C.S. methods adapted to small samples. In general normal paraffins and isoparaffins were found to have some advantages over cyclic hydrocarbons. Presented at the 39th annual meeting of the American Oil Chemists' Society in New Orleans, May 4–6, 1948.     

Effect of glass transition temperature and saturation temperature on the solid‐state microcellular foaming of cyclic olefin copolymer

Effect of glass transition temperature and saturation temperature on the solid‐state microcellular foaming of cyclic olefin copolymer (COC)—including CO₂ solubility, diffusivity, cell nucleation, and foam morphology—were investigated in this article. COCs of low T_g (78°C) and high T_g (158°C) were studied. Solubilities are 20–50% higher in high T_g COC than in the low T_g COC across the saturation temperature range. Diffusivities are about 15% higher on average in high T_g COC for temperatures up to 50°C. A much faster increase of diffusivity beyond 50°C is observed in low T_g COC due to it being in the rubbery state. Under similar gas concentration, high T_g COC starts foaming at a higher temperature. And the foam density decreases faster in low T_g COC with foaming temperature. Also, high T_g COC foams show about two orders of magnitude higher cell nucleation density than the low T_g COC foams. The effect of saturation temperature on microcellular foaming can be viewed as the effect of CO₂ concentration. Nucleation density increases and cell size decreases exponentially with increasing CO₂ concentration. Uniform ultramicrocellular structure with an average cell size of 380 nm was created in high‐T_g COC. A novel hierarchical structure composed of microcells (2.5 μm) and nanocells (cell size 80 nm) on the cell wall was discovered in the very low‐density high‐T_g COC foams. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42226.