Structure modification of mordenite through isomorphous Ti substitution: Characterization and catalytic properties

The introduction of Ti atoms by means of TiCl₄ treatment and hydrothermal synthesis has been applied to mordenite zeolite with different structures from silicalite. The incorporation of Ti into the mordenite framework is demonstrated by XRD, FTIR,²⁹Si MAS NMR techniques, and tested with catalytic oxidation reactions. Ti-Al-mordenite catalyses the oxidation ofn-hexane, cyclohexane and benzene with hydrogen peroxide under very mild conditions. These reactions can be performed in methanol, acetonitrile and water as solvents. The rate of the reaction is strongly affected by the kind of solvent.     

Characterization and supercritical carbon dioxide extraction of walnut oil

Walnut (Juglans regia L.) oil was extracted with compressed carbon dioxide (CO₂) in the temperature range of 308 to 321 K and in the pressure range of 18 to 23.4 MPa. The influence of particle size was also studied at a superficial velocity of 0.068 cm/s, within a tubular extractor of 0.2 L capacity (cross-sectional area of 16.4 cm²). FFA, sterol, TAG, and tocopherol compositions were not different from those of oil obtained with n-hexane. The main FA was linoleic acid (56.5%), followed by oleic acid (21.2%) and linolenic acid (13.2%). The main TAG was LLL (linoleic, linoleic, linoleic) (24.4%), followed by OLL (oleic, linoleic, linoleic) (19.6%) and LLLn (linoleic, linoleic, linolenic) (18.4%). The main component of sterols was β-sitosterol (85.16%), followed by campesterol (5.06%). The amount of cholesterol was low (0.31 and 0.16% for oils extracted by n-hexane and supercritical fluid extraction, respectively. The CO₂-extracted oil presented a larger amount of tocopherols (405.7 μg/g oil) when compared with 303.2 μg/g oil obtained with n-hexane. Oxidative stability determined by PV and the Rancimat method revealed that walnut oil was readily oxidized. Oil extracted by supercritical CO₂ was clearer than that extracted by n-hexane, showing some refining. A central composite, nonfactorial design was used to optimize the extraction conditions using the software Statistica, Version 5. The best results were found at 22 MPa, 308 K, and particle diameter (Dp) −0.1 mm.     

Porous polymers prepared via high internal phase emulsion polymerization for reversible CO2 capture

A series of porous polymers with different pore volumes, pore sizes, and crosslinking densities were synthesized by high internal phase emulsion (HIPE) polymerization. The crosslinked polymerized HIPEs (polyHIPEs) were formed by the copolymerization of 4-vinylbenzyl chloride and divinylbenzene using water droplets in conventional or Pickering HIPEs as the templates. These porous materials were further modified by quaternization and ion exchange to introduce quaternary ammonium hydroxide groups. The resulting polyHIPEs were utilized as sorbents for reversible CO₂ capture from air using the humidity swing. The effect of pore structure on the CO₂ adsorption and desorption processes was studied. The polyHIPEs containing large pores and interconnected porous structures showed improved swing sizes and faster adsorption/desorption kinetics of CO₂ compared to a commercial Excellion membrane with similar functional groups.     

Radiation-induced grafting of methacrylic acid onto polyurethane in the presence of solvents

The radiation-induced grafting of methacrylic acid onto polyurethane has been carried out in the presence of solvents. The swelling of polyurethane was highest when the solubility parameter of the monomer solution was 11.0. The molecular weight of polyurethane did not change with the irradiation dose up to 30 Mrad in the absence of solvent. The irradiation in the presence of solvent, on the other hand, decreased the molecular weight. The grafting yield in CCl₄, benzene, and n-hexane decreased monotonously with the decrease in monomer concentration. The large decrease of the grafting yield in CCl₄ was proved to be due to the high possibility of chain transfer to CCl₄. When such solvents as water, methanol, and DMF were used, on the other hand, a maximum grafting yield was obtained when the monomer concentration was ca. 75%. The hydrogen bonding among polyurethane, methacrylic acid, and solvent was found to affect both the swelling and the grafting yield.     

Soap-free emulsion polymerization of n-butyl acrylate: Copolymerization with 1,1-(dimethyl)-1- (3-methacryloxyethyl)-1-(sulfopropyl)ammonium betaine

Emulsifier-free emulsion polymerization of n-butyl acrylate has been performed in the presence of a polymerizable sulfobetaine monomer, 1,1-(dimethyl)-1-(3-methacryloxyethyl)-1-(sulfopropyl)ammonium betaine (SPE). An investigation of the effect of various salts (NaCl, NaHCO₃, Na₂CO₃, and NaH₂PO₄) on the emulsifier-free emulsion polymerization of n-butyl acrylate revealed that the type and quantity of salt is important in determining the size and size distribution of the final latex particles. In the case of the copolymerizations, control of the monomer feeding protocol (batch vs. semicontinuous and unseeded vs. seeded reactions) and of the ionic strength of the reaction mixture via addition of electrolytes allowed the preparation of stable latexes at 10% solids content with controllable particle size distributions. The results indicate that the amphiphilic sulfobetaine is able to stabilize the latex in much the same way as a polymerizable surfactant or an ionic comonomer. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 227–236, 1998     

Experimental study of diffusivity of hexane in bitumen-saturated porous media under high temperature/pressure conditions

Solvent mass transfer plays a key role in a thermal gravity drainage process involving solvent. The diffusion coefficients of solvent in such a process are not well studied. This article presents the effective diffusion coefficients of solvent in bitumen-saturated sands under high temperature/pressure conditions measured using a CT scanning technique. Experimental results show that the effective diffusion coefficient of n-hexane in bitumen-saturated sands varied with the solvent concentration or with the viscosity of solvent–bitumen mixture (i.e., D_e ∝ c^0.4 or D_e ∝ μ_m^−0.46). The solvent concentration weighted diffusion coefficient of n-hexane in the bitumen under the condition 160–170°C/1,900 kPa had an order of magnitude of about 10⁻⁵ cm²/s for solvent volume concentration less than 0.2. The penetration distance of n-hexane in bitumen-saturated sands depended on the nonlinearity of diffusion and had a value of −2 cm after 1-day diffusion. The stronger the nonlinearity of diffusion, the shorter the penetration distance.     

Solvent engineering applied to lipase-catalyzed glycerolysis of triolein

Solvent engineering was applied to lipase-catalyzed glycerolysis of triolein for the selective synthesis of monoolein and diolein. The effect of different binary mixtures of n-hexane and 2-methyl-2-butanol (2M2B) on the selective production of mono- or diacylglyceride was established. Conditions for high selectivity toward monoolein synthesis were enhanced from 10.6 mol% in pure n-hexane to 64 mol% in 2M2B. On the contrary, the highest production of diolein, corresponding to 62 mol%, was achieved in n-hexane. Concerning triolein conversion, the best results were obtained in 100% 2M2B, with a conversion of 75%. The effect of the n-hexane/2M2B ratio on diolein regioisomer production during triolein glycerolysis was also evaluated. Two different profiles of diolein regioisomers were observed as a function of solvent composition: Although the production of the 1,2-diolein isomer was favored as the proportion of 2M2B in n-hexane was increased, the 1,3-isomer was preferentially synthesized in reactions where n-hexane was the predominant solvent. When 100% n-hexane was used as a solvent, 1,3-diolein comprised 72 mol% of the total diolein population (58 mM). On the contrary, when the reaction was carried out in 100% 2M2B, the total concentration of diolein was lower (21 mM) but the 1,2-diolein regioisomer was preferentially formed (89%). These results were explained as a consequence of the different extents of hydrolysis-synthesis reactions involved in the glycerolysis process, which are strongly dependent on solvent mixtures and water concentration. Finally, some advantages of the use of binary mixtures of solvents compared with other strategies applied to glycerolysis reactions are discussed.     

Highly efficient and versatile one-pot synthesis of substituted thienylidene compounds

A novel, efficient, and very mild one-pot synthesis of methyl 2-[(Z)-4-aryl-5-morpholino-3-oxo-2,3-dihydrothiophen-2-ylidene]acetate derivatives under kinetic control has been developed. The title compounds were prepared by the reaction of thioacetomorpholides with dimethyl acetylene-dicarboxylate (DMAD) in the presence of K₂CO₃ in a non-polar solvent with excellent yields.     

Extraction of rotundifuran and casticin from chaste tree fruits by near critical liquid carbon dioxide

In this study we investigated the use of near critical liquid CO₂ for the extraction of chaste tree ripe fruits (Vitex agnus-castus L.). Two procedures utilizing near critical liquid CO₂ were tested: (1) the extraction of plant material via continuous solvent recycling and (2) the extraction by a Soxhlet-type process via periodic solvent recycling. The results were compared with data obtained from the traditional Soxhlet extraction process using three different solvents, namely n-hexane, dichloromethane, and methanol. Extractions with liquid CO₂, recycled in continuous mode, of chaste tree fruits in three sizes: (1) <0.3 mm, (2) 0.3–0.8 mm, and (3) 3–3.2 mm resulted in maximum yields of 4.9%, 4.1% and 2.8%, respectively. Extraction times of 0.17–25 h were used. Extraction by continuous recycling of liquid CO₂ is more efficient than Soxhlet-type periodic recycling of liquid CO₂, resulting in up to three times higher yield for the same solvent-to-feed ratio. Comparison of HPLC data for extracts obtained by liquid CO₂, n-hexane, dichloromethane and methanol showed that the diterpene rotundifuran is best extracted by liquid CO₂ (3.010 g/kg drug), and the flavonoid casticin is best extracted by n-hexane (1.067 g/kg drug).     

Effect of hydrogen treatments on ZrO2 and Pt/ZrO2 catalysts

ZrO₂ and Pt/ZrO₂ catalysts have been investigated by TPR, hydrogen chemisorption, TPDH and in the conversion ofn-hexane. At high temperature, ZrO₂ takes up hydrogen. High temperature hydrogen treatment is a precondition of the catalytic activity in then-hexane conversion. Possibly, catalytically active acid sites are formed by this hydrogen treatment. The high temperature hydrogen treatment induces a strong Pt-ZrO₂ interaction.     

Glycoconjugated polymer 6. Synthesis of poly[styrene-<Emphasis Type="Italic">block</Emphasis>-(styrene-<Emphasis Type="Italic">graft</Emphasis>-amylose)] via potato phosphorylase-catalyzed polymerization

Summary The potato phosphorylase-catalyzed polymerization of α-D-glucose-1-phosphate (G-1-P) onto poly[styrene-block-(4-vinylbenzyl maltohexaoside)] (1) was performed at the molar ratios of [G-l-P]₀ and [maltohexaose]₀ of 35, 80, and 250. The product was found to be soluble in dimethyl sulfoxide, which was a good solvent for amylose, and showed the complex-formation with iodine, indicating that the product was assignable to poly[styrene-block-(styrene-graft-amylose)] (2). The quantitative analysis of the liberated phosphoric acid gave the average degree of polymerization o f the glucose unit (n) as 27, 5 1, and 180 for 2-I, 2-II, and 2-III, respectively. Received: 29 November 2002/Accepted: 22 December 2002 Correspondence to Toyoji Kakuchi     

Enzymatic Synthesis of Thioesters in Non-conventional Solvents

The feasibility of enzymatic thioesterification between oleic acid and butanethiol in n-hexane, with the immobilised lipase (Lipozyme) from Mucor miehei, has been demonstrated. The immobilised enzyme quantity (100 mg), temperature (40°C), pH range (6–9) and water content (10%) were studied and their optimum values were determined. A preliminary kinetic study indicated a low butanethiol affinity for the enzyme (K_m = 1·85 mol dm⁻³). Even when butanethiol was used without solvent, no substrate inhibition was observed. The possibility of carrying out this reaction in a natural solvent, supercritical carbon dioxide (SCCO₂), was successfully verified. After 8 h reaction, a conversion yield of oleic acid of about 33% was obtained. © 1997 SCI.     

Is 1-hexene epoxidation in TS-1 diffusion limited in different solvents?

PFG NMR diffusion measurements were carried out to determine the effect of solvent on intracrystalline reactant diffusivities and on 1-hexene epoxidation rates in TS-1 catalyst. Using n-hexane in silicalite as a mimic for the TS-1 system, the self-diffusivity of n-hexane in silicalite was found to be 24% higher in methanol solvent than in acetonitrile solvent and 45% higher than in acetone solvent. The presence of trace Al did not affect n-hexane diffusivity. Based on analysis of the Weisz modulus for a slab morphology, the 1-hexene epoxidation reaction in TS-1 was found to be diffusion limited only if the crystal size is at least 38 μm in the methanol system.     

Pathways for CO2 Formation and Conversion During Fischer–Tropsch Synthesis on Iron-Based Catalysts

CO₂ reaction and formation pathways during Fischer–Tropsch synthesis (FTS) on a co-precipitated Fe–Zn catalyst promoted with Cu and K were studied using a kinetic analysis of reversible reactions and with the addition of ¹³C-labeled and unlabeled CO₂ to synthesis gas. Primary pathways for the removal of adsorbed oxygen formed in CO dissociation steps include reactions with adsorbed hydrogen to form H₂O and with adsorbed CO to form CO₂. The H₂O selectivity for these pathways is much higher than that predicted from WGS reaction equilibrium; therefore readsorption of H₂O followed by its subsequent reaction with CO-derived intermediates leads to the net formation of CO₂ with increasing reactor residence time. The forward rate of CO₂ formation increases with increasing residence time as H₂O concentration increases, but the net CO₂ formation rate decreases because of the gradual approach to WGS reaction equilibrium. CO₂ addition to synthesis gas does not influence CO₂ forward rates, but increases the rate of their reverse steps in the manner predicted by kinetic analyses of reversible reactions using non-equilibrium thermodynamic treatments. Thus the addition of CO₂ could lead to the minimization of CO₂ formation during FTS and to the preferential removal of oxygen as H₂O. This, in turn, leads to lower average H_2/CO ratios throughout the catalyst bed and to higher olefin content and C₅₊ selectivity among reaction products. The addition of ¹³CO₂ to H₂/¹²CO reactants did not lead to significant isotopic enrichment in hydrocarbon products, indicating that CO₂ is much less reactive than CO in chain initiation and growth. We find no evidence of competitive reactions of CO₂ to form hydrocarbons during reactions of H₂/CO/CO₂ mixtures, except via gas phase and adsorbed CO intermediates, which become kinetically indistinguishable from CO₂ as the chemical interconversion of CO and CO₂ becomes rapid at WGS reaction equilibrium.     

Sorption-enhanced dimethyl ether synthesis—Multiscale reactor modeling

As an opportunity for the attenuation of atmospheric CO₂ emissions, conversion of carbon dioxide into valuable oxygenates as fuel additives or fuel surrogates was explored conceptually in terms of a potentially feasible dimethyl ether (DME) conversion process. Incentives for application of conventional CO₂–DME conversion process are insufficient due to low CO₂ conversion, and DME yield and selectivity. In-situ H₂O removal by adsorption (sorption-enhanced reaction process) can lead to the displacement of the water gas shift equilibrium and therefore, the enhancement of CO₂ conversion into methanol and the improvement of DME productivity. A two-scale, isothermal, unsteady-state model has been developed to evaluate the performance of a sorption-enhanced DME synthesis reactor. Modeling results show that under H₂O removal conditions, methanol and DME yields and DME selectivity are favoured and the methanol selectivity decreases. The increase of methanol and DME yields and DME selectivity becomes more important at higher CO₂ feed concentration because a relatively large amount of water is produced followed by a large quantity of water removed from the system. Also, the drop in the fraction of unconverted methanol becomes more important when CO₂ feed concentration is higher and the dehydration reaction is favoured. Therefore, application of the sorption-enhanced reaction concept allows the use of CO₂ as a constituent of the synthesis gas as the in-situ H₂O removal accelerates the reverse water gas shift reaction.     

Carbon dioxide pressure induced heterogeneous and homogeneous Heck and Sonogashira coupling reactions using fluorinated palladium complex catalysts

The Heck reaction of iodobenzene and methyl acrylate was investigated with CO₂-philic Pd complex catalysts having fluorous ponytails and the organic base triethylamine (Et₃N) in the presence of CO₂ under solventless conditions at 80 °C. The catalysts are not soluble in the organic phase in the absence of CO₂ and the reaction occurs in a solid-liquid biphasic system. When the organic liquid mixture is pressurized by CO₂, CO₂ is dissolved into the organic phase and this promotes the dissolution of the Pd complex catalysts. As a result, the Heck reaction occurs homogeneously in the organic phase, which enhances the rate of reaction. This positive effect of CO₂ pressurization competes with the negative effect that the reacting species are diluted by an increasing amount of CO₂ molecules dissolved. Thus, the maximum conversion appears at a CO₂ pressure of around 4 MPa under the present reaction conditions. The catalysts are separated in the solid granules by depressurization and are recyclable without loss of activity after washing with n-hexane and/or water. When the washing is made with hexane alone, the catalytic activity tends to increase on the repeated Heck reactions, probably due to the accumulation of such a base adduct as Et₃NHI on the catalysts. When the washing is further made with water, however, the base adduct is taken off from the catalysts and they show similar activity levels in the repeated runs. The potential of CO₂ pressure tunable heterogeneous/homogeneous reaction system has also been investigated for Sonogashira reactions of iodobenzene and phenylacetylene under similar conditions.     

Investigations on nylon 4 membranes. Synthesis and transport properties. I. Synthesis of nylon 4 polymer

The synthesis of nylon 4 (polypyrrolidone) by the anionic polymerization of 2-pyrrolidone through the use of the CO₂/potassium pyrrolidonate catalyst system for use in preparing polymer membranes for separation purposes was investigated in detail. The effects of the quantity of CO₂, the potassium pyrrolidonate catalyst, and the reaction temperature on the yield and molecular weights of the nylon 4 were studied. At reaction temperatures of 50°C and a reaction time of 120 hr, a yield of 50.9% with intrinsic viscosity of 4.42 (corresponding to M_n of 108,200 and M_w of 135,850) was obtained. The molecular weight distributions of the nylon 4 were determined by gel permeation chromatography (GPC) using m-cresol as the eluting solvent and were found to have a relatively narrow distribution.     

The Oxidative Dehydrogenation of <Emphasis Type="Italic">n</Emphasis>-Hexane over a β-NiMoO<Subscript>4</Subscript> Catalyst

Abstract  

The oxidative dehydrogenation of n-hexane over β-NiMoO₄ catalysts was performed in a fixed bed continuous flow reactor. Catalytic testing was done below and above the flammability limits for n-hexane and the effect of reaction conditions was examined to optimize hexene selectivity. The contact times (0.61-2.4 s), n-hexane/oxygen molar ratios and nitrogen dilution (31–60%) were varied. The highest selectivity to total hexenes obtained was 54.7% which was made up of 27.4% 1-hexene, 25.0% trans-2-hexene and 2.3% cis-2-hexene. These selectivities were obtained at a fuel/O₂ ratio of 2.2, a contact time of 1.0 s and 43% nitrogen dilution.     

Selective hydrogenation of chloronitrobenzene to chloroaniline in supercritical carbon dioxide over Ni/TiO2: Significance of molecular interactions

The hydrogenation of chloronitrobenzene to chloroaniline was investigated over Ni/TiO₂ at 35 °C in supercritical CO₂ (scCO₂), ethanol, and n-hexane. The reaction rate followed the order of scCO₂ > n-hexane > ethanol. In scCO₂, the selectivity to chloroaniline and to aniline over Ni/TiO₂ were 97–99.5% and <1%, respectively, in the conversion range of 9–100%. The high chemoselectivity to chloroaniline cannot be achieved over Ni/TiO₂ in ethanol and n-hexane. In situ high-pressure Fourier transform infrared measurements were made to study the molecular interactions of CO₂ with the following reactant and reaction intermediates: chloronitrobenzene, chloronitrosobenzene, and N-chlorophenylhydroxylamine. The molecular interaction modifies the reactivity of each species and accordingly the reaction rate and the selectivity. The influence of Cl substituent on the interaction modes of CO₂ with these reacting species is discussed. Possible reaction pathways for the hydrogenation of chloronitrobenzene in scCO₂ over Ni/TiO₂ are also proposed.     

A water‐soluble CO2‐triggered viscosity‐responsive copolymer of N,N‐dimethylaminoethyl methacrylate and acrylamide

A series of copolymers PDAMs were synthesized with varying monomer ratio of acrylamide (AM) and N,N‐dimethylaminoethyl methacrylate (DMAEMA). The resulting copolymer solution shows an interesting property of viscosity‐response which is CO₂‐triggered and N₂‐enabled. Tertiary amine groups of PDAMs experience a reversible transition between hydrophobic and hydrophilic state upon CO₂ addition and its removal, which induced different rheological behavior. A combination of zeta‐potential, laser particle‐size analysis, and electrical conductivity analysis indicated that, when the monomer mole ratio of DMAEMA and AM is less than or equal to 3 : 7, the hydrophobic association structure between the copolymer molecules was destroyed by the leading of CO₂ and caused a viscosity decrease in its solution. On the contrary, when the monomer mole ratio of DMAEMA and AM is more than 3 : 7, a more extended conformation due to the protonated tertiary amine groups is formed and the enhanced repulsive interactions among the copolymer molecule results in a rise of its solution viscosity. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40872.