Investigation on the morphology of hierarchical mesoporous ZSM-5 zeolite prepared by the CO2-in-water microemulsion method

A series of hierarchical mesoporous ZSM-5 zeolites with different morphology were successfully synthesized by the CO₂-in-water microemulsion method, and mesoporosity was formed without organotemplate. The different synthesis conditions, including silica alumina molar ratio, stirring time and compressed CO₂ pressure, were systematically investigated to discuss the influence of these conditions on the morphology of ZSM-5 zeolite. The resulting samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), inductively coupled plasma (ICP) and nitrogen adsorption-desorption measurement. XRD results indicated that compressed CO₂ route for the synthesis of MFI zeolites had a fast crystallization rate and good crystallinity. SEM images showed that the ZSM-5 hierarchical mesoporous ZSM-5 zeolite had a uniform chain-like crystal morphology, whereas silicalite-1 displayed a monodisperse crystal morphology. In addition, the nitrogen adsorption-desorption measurement provided sufficient evidence for the presence of hierarchical mesopores in ZSM-5 zeolite.     

Synthesis,characteristics of hierarchical EU-1 zeolite for xylene isomerization probe reaction

Introduced a method of synthesizing hierarchical EU-1 zeolite with organosilanes as additive, and studied the influences of following different kinds of organosilanes on the synthesis of hierarchical EU-1 zeolite: γ-glycidoxy propyl trimethoxy silane(GPTMS), N-β-(aminoethyl)-γ-aminopropyl methyl dimethoxyl silane(APAEDMS),and N-(β-aminoethyl)-γ-aminopropyl dimethoxyl(ethyoxyl) silane(TMPED). The hierarchical EU-1 samples were characterized by XRD, SEM, N_2 adsorption, FT-IR and NH_3-TPD to analyze the crystallinity, morphology, surface area, pore size distribution and acidity. The results showed that hierarchical EU-1 zeolites were successfully synthesized; organosilanes have great influence on crystal morphology of EU-1 zeolites; the exterior surface area of hierarchical EU-1 zeolite, which synthesized with organosilanes(APAEDMS) adding into synthesis system, increased by 62.1% and mesopore volume increased by 129.1% compared with conventional EU-1 zeolites, thus can reduce the diffusional restriction markedly in catalytic reaction. The catalytic performance of hierarchical EU-1zeolites were evaluated in m-xylene isomerization on fixed bed reactor. The catalytic data showed that the isomerization activity PX/X of the hierarchical EU-1 zeolites reached around 24.09% in theoretical thermodynamic equilibrium from 23.83%, and the selectivity of C_8 aromatic hydrocarbon increased from 75.16% to 84.87%. The conversion of p-xylene increased from 16.30% to 18.41%.     

Polymorphism and transformation energetics of saturated monoacid triglycerides from differential scanning calorimetry and theoretical modeling

Differential scanning calorimetry studies on saturated monoacid triglycerides were extended to include most odd and even chain lengths from tricaprylin (C₈) through tritriacontanoin (C₃₀). Two β’-forms were common with triglycerides C₁₅ through C₂₄: shorter odd chain length triglycerides (C₉-C₁₃) exhibited only one β’-form; short even chain length triglycerides (C₈-C₁₄) exhibited three. Odd chain length C₂₁ and C₂₃ triglycerides showed two β-forms. Triglycerides of even chain lengths greater than C₂₁ produced two α-forms. Apparent energies of phase excitation for α-form transformations (determined from scans at different heating rates) showed odd-even alternation for short chain lengths, but increased linearly with chain length above C₁₄, evidencing the importance of extended chain conformation and interactions as determinants of polymorph properties. Changes in melting point patterns, particularly for β’ and β-forms, at C₁₄ correlated with the change in apparent phase excitation energy. Comparisons of X-ray data with dimensions from space-filling models and agreement between observed entropies of fusion and values calculated for probabilistic models also emphasize the importance of extended chain conformation and suggest configurational differences, and possibly different polymorph conversion pathways for odd versus even chain length triglycerides.     

Aminimides: II. Antimicrobial effect of short chain fatty acid derivatives

A new family of surfactants, aminimides, has been screened forin vitro antimicrobial activity. These compounds are active against both bacteria and yeast, activity being a function of chain length. Maximum activity for acetimide and acrylimide amine derivatives was extablished with chain lengths of C₁₄–C₁₆. Homologous compounds with lower or higher chain lengths were less active. While showing low antimicrobial activity against gram negative bacteria, mixtures containing C₁₂ and C₁₆ gave good activity against gram negative strains without losing gram positive activity. Aminimides gave low acute LD₅₀’s (200–400 mg/kg) when tested in mice by intraperitoneal injection.     

Synthesis of FeAPO-5 molecular sieves with high iron contents via improved ionothermal method and their catalytic performances in phenol hydroxylation

To synthesize zeolites in a safe and cost-saving manner is the first and the most important task for zeolite application in industry. In the present work, FeAPO-5 aluminophosphate molecular sieve with high iron content was ionothermally synthesized by microwave irradiation at ambient pressure using low dosage of eutectic mixture as the solvent. The influences of seed crystals and mechanochemical pretreatment on the synthesis of FeAPO-5 were investigated in detail. The resultant relatively pure FeAPO-5 molecular sieves were characterized by XRD, ICP-AES, SEM, N₂ physisorption and UV–Vis diffuse reflectance spectrometer, and their catalytic performances were studied using phenol hydroxylation as a probe reaction. The XRD results revealed that pure FeAPO-5 can be readily obtained from mechanochemically pretreated reactants, regardless of whether or not the seed crystals were added. The ICP-AES measurements suggested that only by using specific seed crystals can pure FeAPO-5 molecular sieve with high iron content be synthesized. The SEM analysis implied that seed crystals may play a role of morphology-directing agent in these syntheses. The catalytic results demonstrated that longer pronounced induction period were only observed over those FeAPO-5 catalysts with sole framework iron species. The different catalytic activity among five selected catalysts was largely determined by their different densities of framework iron species, while the selectivity towards dihydroxybenzene was mainly controlled by the diffusion path length. Under given reaction conditions, FeAPO-5 catalyst with up to 6.79 wt% of iron content gave 42.0% dihydroxybenzene yield with a selectivity of 94.1%.     

Purification,Surface Tensions,and Miscibility Gaps of Alkyldimethyl and Alkyldiethylphosphine Oxides

Alkyldimethyl (C _n DMPO) with chain lengths of n = 8 (octyl), 10 (decyl), 12 (dodecyl), and 14 (tetradecyl) as well as alkyldiethyl (C _n DEPO) phosphine oxides with chain lengths of n = 10, 12, and 14 were synthesized and purified to study how the adsorption properties and the location of the miscibility gap of these surfactants depend on the size of the head group and on the length of the alkyl chain. After surfactant purification, the surface tension isotherms were determined from which the cmc, the minimum surface tension σ_cmc, the maximum surface concentration Γ_max, and the minimum surface area A _min were obtained. As expected, for one homologous series, a decrease in the cmc and an increase in Γ_max was observed with increasing alkyl chain length. For two surfactants of the same alkyl chain length, the cmc values of the C _n DEPO surfactants are approximately two times lower than those of the C _n DMPO surfactants. However, the Γ_max values of C _n DEPO are lower than those of C _n DMPO as two ethyl chains are sterically more demanding than two methyl chains. In addition to the adsorption properties, the location of the miscibility gap as a function of the alkyl chain length and the head group size was studied. Its location depends on the total number of carbon atoms and not primarily on the length of the main alkyl chain. This observation reflects the decreasing water solubility which can be tuned by increasing the length of either the main alkyl chain or of the shorter head group chains.     

Effects of different structure-directing agents (SDA) in MCM-41 on the adsorption of CO2

CO₂ capturing technologies have attracted significant attention in order to limit emissions and reduce their negative effect on the environment. Mesoporous silica materials (MCM-41) are easily recyclable, affordable, and thermally and mechanically stable, providing added benefits in CO₂ capture. However, further studies are necessary to characterize the effects of MCM-41 pore size, adsorption temperature and surface silylation on CO₂ adsorption efficiency. In this work, mesoporous silica is synthesized using alkyltrimethylammonium bromide with different chain lengths (C_nH_2n + 1 N(CH₃)₃Br, n = 14, 16 and 18) as structure-directing agents, and the adsorption capacity of CO₂ on TTMCM-41 (C₁₇H₃₈NBr), CTMCM-41 (C₁₉H₄₂NBr), DTMCM-41(C₂₁H₄₆NBr) samples was measured gravimetrically at room temperature and pressure up to 40 bar. The silica structures were characterized by X-ray diffraction (XRD), nitrogen adsorption/desorption, Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy and transmission electron microscopy (TEM). The XRD, N₂ adsorption–desorption and TEM measurements indicated the presence of a well-ordered hexagonal array with uniform mesostructures. The mesoporous silica obtained, denoted as TTMCM-41, CTMCM-41 and DTMCM-41, had distinct physical properties, such as BET surface area, hexagonal unit cell, pore volume, pore diameter and pore wall thickness. CTMCM-41 exhibited an adsorption capacity (0.58 g CO₂/g adsorbent) of more than DTMCM-41 (0.48 g CO₂/g adsorbent) and TTMCM-41 (0.42 g CO₂/g adsorbent). The results suggest that CTMCM-41 can be a better mesoporous adsorbent for CO₂ adsorption .     

Synthesis of ZSM-5 type zeolites with and without template and evaluation of physicochemical properties and aniline alkylation activity

ZSM-5 zeolite containing SiO₂/Al₂O₃ = 28 was synthesised by hydrothermal process with and without template. Characterisation of the zeolites was done using XRD, IR, NMR, SEM and BET surface area measurements. Acidity of the zeolites was measured by ammonia adsorption-desorption. Catalytic activity of HZSM-5 zeolites was evaluated by aniline alkylation, cumene dealkylation, alkylation of benzene with ethylene and propylene and isomerisation ofm-xylene. Catalytic activity is discussed from the point of view of zeolite acidity and morphology.     

Organic template-free synthesis of ZSM-5/ZSM-11 co-crystalline zeolite

A series of ZSM-5/ZSM-11 co-crystalline zeolites with various compositions and morphologies were successfully synthesized via an organic template-free hydrothermal route and characterized by XRD, XRF, SEM, NMR and N₂ adsorption/desorption technologies. The effects of raw materials and batch composition were investigated systematically. Various silicon sources can be employed in the organic template-free synthesis of ZSM-5/ZSM-11 co-crystalline zeolite, however only a few types of aluminum sources are available. This organic template-free system is favorable to the aluminum-rich zeolite. With the increase of initial SiO₂/Al₂O₃ ratio, the ZSM-5 percentage in the ZSM-5/ZSM-11 co-crystalline zeolite increases as well as the crystal size, and especially the morphology of ZSM-5/ZSM-11 co-crystalline zeolite prepared from the colloidal silica-NaAlO₂ solution system changes gradually from nano-rod aggregation, micro-spindle to single hexagon and then to twinned hexagon crystals. Moreover, Na⁺ and OH⁻ in the initial materials can promote the nucleation of the ZSM-5/ZSM-11 co-crystalline zeolite significantly and are beneficial to the formation of crystals with relatively low length/width ratio, while K⁺ postpones the crystallization process seriously.     

Aminimides IV: Antimicrobial activity of 1,1,1-Tris (2-hydroxyethyl) amine-2-acylimides

The newest member of the aminimide family of surfactants was screened for antimicrobial activity. The present report supports past conclusions that chain lengths of C₁₄ or C₁₆ gave maximum activity to the aminimide derivative. When a number of hexadecane compounds with different polar groups were compared, the aminimide exhibited wide spectrum antimicrobial activity. Although the functional group was important, the length and character of the acyl chain also help to determine antimicrobial activity. A new amide antibiotic, Cerulenin, with a 4-keto-2-enyl chain, was more active than the unsaturated isomer. Thus, both the functional grup as well as the chain length contribute to biocidal activity.     

Efficient catalytic epoxidation of olefins with hierarchical mesoporous TS-1 using TBHP as an oxidant

A series of hierarchical mesoporous TS-1 zeolites with MFI structure were successfully synthesized via hydrothermal route using amphiphilic organosilanes as pore directing templates. These materials were characterized by nitrogen sorption (for surface area, pore volume and pore size distribution), FTIR, SEM and UV–Visible spectroscopy. These materials are efficient catalysts for liquid phase epoxidation of olefins using TBHP as the oxidant. All these TS-1 samples oxidized cyclohexene selectively into epoxide. For the TS-1 sample with 4.4 % Ti complete conversion of cyclohexene into epoxide was observed.     

Heterogeneous Ziegler–Natta catalysts with various sizes of MgCl<Subscript>2</Subscript> crystallites: synthesis and characterization

A MgCl₂-based Ziegler–Natta catalyst was characterized using X-ray diffraction (XRD) patterns, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and IR spectra. We focused on the XRD reflection at 2θ = 50° to determine the thickness of MgCl₂ crystals, and validated these results with TEM pictures. SEM pictures were taken in order to measure the size of the nanoparticles formed by the MgCl₂ crystals. Several compounds were synthesized for comparison and to aid interpretation of the infrared (IR) spectra. The catalysts were prepared by precipitating MgCl₂, which was used as support material and subsequently treated with TiCl₄. The thickness of the catalyst crystals was calculated from the XRD reflection at 2θ = 50°. Changing the precipitation temperature within a range from 40 to 90 °C altered the thickness of the MgCl₂ crystal plates. The maximum thickness of 7 nm was achieved at a precipitation temperature of 60 °C. The SEM pictures showed that the nanoparticles had a diameter of ~200 nm. A crystal base unit had a volume that corresponded to that of a sphere of 3.5 nm radius. Thus, we estimated that a typical catalyst particle with a diameter of 20 μm contained about one million nanoparticles, each of which consisted of about 25,000 MgCl₂ crystal units.     

Characterization and fluorine-free microwave hydrothermal synthesis of AlPO<Subscript>4</Subscript>-5 molecular sieves as adsorbents

With a characteristic of S-shaped water sorption isotherms, AlPO₄-5 molecular sieves have been considered as up-and-coming adsorbents for the utilization in adsorptive cooling and heating systems. In order to avoid toxicity and corrosion of fluoride, this paper introduced a fluorine-free microwave hydrothermal synthesis strategy of pure AlPO₄-5 crystals. The effects of hydrothermal conditions including template agent, crystallization temperature and time on the performances of AlPO₄-5 adsorbents were systematically investigated. Fourier transform infrared spectroscopy, X-ray diffraction (XRD), ²⁷Al and ³¹P solid state magic angle spinning nuclear magnetic resonance (MAS NMR), pore size analyzer and Scanning electron microscopy (SEM) were used to determine the chemical structure, crystalloid phase, framework, pore structure and the morphology. Adsorption and desorption performances were measured by static adsorption, thermogravimetry and temperature programmed desorption. XRD results indicated that both triethylamine and tetraethylammonium hydroxide as templates, AlPO₄-5 crystals could quickly be synthesized within 30–45 min under fluorine-free microwave irradiation. By comparison, the adsorption and desorption performance of the former (recorded as AlPO₄-5A) was superior to that of the latter (recorded as AlPO₄-5H). FT-IR, MAS NMR and SEM results revealed that AlPO₄-5 crystals have the frameworks of alternating AlO₄ and PO₄ units and typical hexagonal rod-like morphologies.     

Fatty Acid Biosynthesis: Chain-Length Regulation and Control

De novo biosynthesis of fatty acids is an iterative process requiring strict regulation of the lengths of the produced fatty acids. In this review, we focus on the factors determining chain lengths in fatty acid biosynthesis. In a nutshell, the process of chain-length regulation can be understood as the output of a chain-elongating C−C bond forming reaction competing with a terminating fatty acid release function. At the end of each cycle in the iterative process, the synthesizing enzymes need to “decide” whether the growing chain is to be elongated through another cycle or released as the “mature” fatty acid. Recent research has shed light on the factors determining fatty acid chain length and has also achieved control over chain length for the production of the technologically interesting short-chain (C₄–C₈) and medium-chain (C₁₀–C₁₄) fatty acids.     

ADSORPTION OF ETHOXYLATED NONIONIC SURFACTANTS FROM SILOXANE-BASED SOLVENT AND AQUEOUS SYSTEMS: USE OF QCM AND MODEL POLYMERIC SURFACES

Adsorption behavior was quantified with pure ethoxylated nonionic surfactants onto different polymeric surfaces (hydrophilic cotton and hydrophobic polyester) and model hydrophilic gold surface. The polymer materials used for the study were characterized using SEM. The role of ethylene oxide group variation in surfactant-polymer interaction was established using pure surfactant with the same alkyl chain length but varying ethoxylate chain lengths. It was observed that surfactant with more ethylene oxide groups per molecule, being more hydrophilic, interacts favorably with cotton in the hydrophobic siloxane solvent environment. The adsorption of the pure surfactants on model gold surface from hydrophobic solvent and water was also established using the quartz crystal microbalance with dissipation monitoring (QCM-D) system. Effect of ethylene oxide chain length and surfactant concentration on the extent of adsorption was quantified. At the gold-water interface, the plateau adsorption for C₁₂ E₃ (15.9 × 10^?6 mole/m²) is about four times higher than for C₁₂E₈. An opposite trend was observed for adsorption of the surfactants on gold in the hydrophobic D5 environment. Information about thickness, adsorption and desorption kinetics, and structure of adsorbed layer was obtained from the QCM-D frequency-dissipation data. The study is an important contribution towards fundamental understanding of applications involving the use of ethoxylated nonionic surfactants.     

Synthesis,characterization of Al-rich ZSM-12 zeolite and their catalytic performance in liquid-phase tert-butylation of phenol

Al-rich ZSM-12 zeolites were synthesized using N,N,N′,N′-tetraethylbicyclo[2.2.2]oct-7-ene-2,3:5,6-dipyrrolidinium diiodide as template under hydrothermal conditions. Their physico-chemical properties were characterized using XRD, ICP-AES, SEM, N₂ adsorption, ²⁷Al MAS NMR and NH₃-TPD. The results indicated that Al-rich ZSM-12 zeolites with low Si/Al ratios of 8–23 were successfully crystallized. Catalytic properties of the prepared zeolites were studied in the tert-butylation of phenol. Higher para selectivity was obtained on the Al-rich ZSM-12 zeolites compared with other types of zeolites.     

Surface Properties of Glucose-Based Surfactants and Their Application in Textile Dyeing with Natural Dyes

In this study, propylene glycol-based glycosides were obtained using an acetalization reaction in which glucose was first reacted with propylene glycol. Subsequently, the propylene glycol glycoside was reacted with alkyl glycidyl ether of varying carbon chain lengths (i.e., 08-G, 10-G, 12-G, 14-G, and 16-G) to synthesize a series of glucose-based biodegradable surfactants. The experimental results show that the surface activity of the C₈–C₁₂ glucose-based surfactants increases with the carbon chain length. However, the surface activity of the C₁₄–C₁₆ glucose-based surfactants decreased as the carbon chain length increased. Among all the surfactants, the C₁₂ glucose-based surfactant exhibited the most efficient emulsification ability, lowest surface tension, lowest fluorescence intensity, highest zeta potential, and good emulsification stability. The glucose-based surfactants were used as additives in natural plant dyes made from turmeric or henna to dye wool fabrics. Higher color strengths were observed in the C₁₄ glucose-based surfactant.     

Neue Tenside aus gemischten Guerbet-Alkoholen

New Surfactants from Mixed Guerbet-Alcohols 2-Benzyl fatty alcohols can be prepared in good yields by mixed Guerbet-reaction of fatty alcohols in the range of chain lengths from C₈–C₁₄ with benzyl alcohol. The polyglycolethers and polyglycolethersulfates from these mixed Guerbet-alcohols are very effective new surfactants with a better biodegradibility as compared to nonylphenol polyglycolethers.     

Polycrystalline silicon nitride fibers by combustion synthesis

SHS nitriding of Si in the presence of added (NН₄)₂(COO)₂ ? H₂O and FeCl₃ ? 6Н₂О under pressure of nitrogen gas was explored by XRD and SEM. The additives were used with an intention to transpose the nitriding reaction into the gas phase and thus to allow the deposition of Si₃N₄ from the gas phase. Thus prepared Si₃N₄ had a shape of polycrystalline fibers formed by 1D crystals of varied morphology and by the assemblies of nanosized crystals. Phase composition, fiber length, and shape of nanocrystals were found to depend on nitrogen pressure. Synthesized fibers can find their application in heat insulation of aircrafts, fabrication of coatings, deep purification filters, etc.     

Synthesis and catalytic performance of a bi-phase core-shell zeolite composite

A zeolite composite Y/Beta with core-shell structure was synthesized by adding tetraethylammonium bromide (TEABr) exchanged NaY zeolite into the pre-reacted mixture used to prepare Beta zeolite. The composite was characterized by XRD, N₂ adsorption, SEM, and FTIR spectra of pyridine. The results show that the composite is composed of a core zeolite Y and a shell of intergrown zeolite Beta crystals, representing dual microporous structures of both Y and Beta zeolites and a new mesoporous structure. The composite has a high activity in n-octane catalytic cracking because of the formation of intergrowths and the change of acidity due to the distorted interface and surface defects.