- Inorganic salts of biguanide - Searching for new materials for second harmonic generation
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Five inorganic salts of biguanide with carbonic, nitric, phosphoric and phosphorous acids were prepared and X-ray structural analysis has been performed for three novel compounds. Biguanidium(1+) phosphite trihydrate crystallizes in the triclinic space group P over(1, ?), a = 7.1470(1) ?, b = 9.6530(2) ?, c = 11.3140(2) ?, α = 70.094(1)°, β = 75.688(1)°, γ = 86.099(1)°, V = 713.71(2) ?3, Z = 2, R = 0.0350 for 3031 observed reflections. The crystal structure is based on a network of phosphite anions and water molecules. Biguanidium(1+) cations form pairs through two intermolecular hydrogen bonds of the N-H...N type and fill the network with anions and water molecules. Biguanidium(2+) phosphite monohydrate crystallizes in the triclinic space group P over(1, ?), a = 6.9690(2) ?, b = 7.3500(3) ?, c = 8.1730(3) ?, α = 82.518(2)°, β = 83.015(2)°, γ = 82.811(2)°, V = 409.44(3) ?3, Z = 2, R = 0.0308 for 1779 observed reflections. The structure is formed of a network of alternating biguanidium(2+) cations, phosphite anions and pairs of water molecules interconnected by a system of intermolecular hydrogen bonds. Biguanidium(2+) hydrogen phosphate monohydrate crystallizes in the triclinic space group P over(1, ?), a = 7.0630(2) ?, b = 7.8740(3) ?, c = 8.1120(3) ?, α = 102.706(2)°, β = 104.976(2)°, γ = 92.632(3)°, V = 422.61(3) ?3, Z = 2, R = 0.0337 for 1827 observed reflections. The crystal structure is formed by pairs of anions that are mutually connected in chains through two water molecules. These chains are interconnected by biguanidium(2+) cations to form a three-dimensional network. The FTIR and FT Raman spectra of all five compounds were recorded, calculated (HF, B3LYP and MP2 methods) and discussed. Quantitative measurements of second harmonic generation of powdered biguanidium(2+) nitrate and novel biguanidium(2+) carbonate monohydrate at 800 nm were performed and a relative efficiency (compared to KDP) of 87% and 20% was observed, respectively.
- Matulková, Irena,Němec, Ivan,Císa?ová, Ivana,Němec, Petr,Mi?ka, Zdeněk
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- Flow-Tube Investigations of Hypergolic Reactions of a Dicyanamide Ionic Liquid Via Tunable Vacuum Ultraviolet Aerosol Mass Spectrometry
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The unusually high heats of vaporization of room-temperature ionic liquids (RTILs) complicate the utilization of thermal evaporation to study ionic liquid reactivity. Although effusion of RTILs into a reaction flow-tube or mass spectrometer is possible, competition between vaporization and thermal decomposition of the RTIL can greatly increase the complexity of the observed reaction products. In order to investigate the reaction kinetics of a hypergolic RTIL, 1-butyl-3-methylimidazolium dicyanamide (BMIM+DCA-) was aerosolized and reacted with gaseous nitric acid, and the products were monitored via tunable vacuum ultraviolet photoionization time-of-flight mass spectrometry at the Chemical Dynamics Beamline 9.0.2 at the Advanced Light Source. Reaction product formation at m/z 42, 43, 44, 67, 85, 126, and higher masses was observed as a function of HNO3 exposure. The identities of the product species were assigned to the masses on the basis of their ionization energies. The observed exposure profile of the m/z 67 signal suggests that the excess gaseous HNO3 initiates rapid reactions near the surface of the RTIL aerosol. Nonreactive molecular dynamics simulations support this observation, suggesting that diffusion within the particle may be a limiting step. The mechanism is consistent with previous reports that nitric acid forms protonated dicyanamide species in the first step of the reaction.
- Chambreau, Steven D.,Koh, Christine J.,Popolan-Vaida, Denisia M.,Gallegos, Christopher J.,Hooper, Justin B.,Bedrov, Dmitry,Vaghjiani, Ghanshyam L.,Leone, Stephen R.
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- Promoting condensation kinetics of polymeric carbon nitride for enhanced photocatalytic activities
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Polymeric carbon nitride (CN) semiconductor by thermal condensation of N-rich precursors has attracted much attention for its capability ranging from photocatalytic and photoelectrochemical energy conversion to biosensing. However, the influence of condensation process on the final structure of CN was rarely studied, making the condensation kinetic far from be fully optimized. Herein, we report the preparation of CN by a simple condensation kinetics modulation using a faster ramping rate during the polymerization process. The modified condensation recipe was even simpler than the conventional one, but led to an improved photocatalytic H2 evolution up to 3 times without any additional chemicals or other complements. Detailed mechanism studies revealed the increase of crystallinity and surface area due to the rapid condensation played the key roles. This work would offer a more facile and effective way to prepare bulk CN for large-scale industrial applications of bulk CN with higher photocatalytic actives for sustainable energy, environmental and biosensing.
- Ni, Dongya,Zhang, Yuye,Shen, Yanfei,Liu, Songqin,Zhang, Yuanjian
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- A Facile Synthesis of Pd–C3N4@Titanate Nanotube Catalyst: Highly Efficient in Mizoroki–Heck, Suzuki–Miyaura C–C Couplings
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Abstract: A Pd–C3N4@titanate nanotube (Pd–C3N4@TNT) catalyst workable in water medium, robust against leaching and agglomeration was prepared in a facile synthetic procedure using quite common chemicals such as TiO2 powder, urea and palladium acetate. The Pd–C3N4@TNT catalyst has been characterized by BET surface area and pore size distribution, X-ray diffraction, solid-state 13C NMR spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscopy. The Pd–C3N4@TNT is a green catalyst for the Miziroki–Heck and Suzuki–Miyaura C–C coupling reactions in water medium with high efficiency (??99% product yields) due to atomic level immobilization of Pd in C3N4 networked titanate nanotubes. Pd–C3N4@TNT is robust against leaching and agglomeration due to stable and furthermore it is recyclable and usable at least for five repeated cycles. The use of water as solvent, absence of leaching and agglomeration, recyclability and reusability ascertains the greenness of Pd–C3N4@TNT) catalyst and process. Graphic Abstract: Novel Pd–C3N4@titanate nanotube catalyst prepared from bulk TiO2 and urea by simple hydrothermal and thermal pyrolysis followed by immobilization of Pd is active and selective for Mizoroki–Heck, Suzuki–Miyaura C–C couplings in water medium.[Figure not available: see fulltext.].
- Velpula, Venkata Ramana Kumar,Ketike, Thirupathaiah,Paleti, Gidyonu,Kamaraju, Seetha Rama Rao,Burri, David Raju
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- Novel carbon nitride composites with improved visible light absorption synthesized in ZnCl2-based salt melts
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Poly(triazine imide)-based carbon nitride materials with BET surface areas up to 200 m2g-1were synthesized in ZnCl2containing salt melts without the use of hard templates. We found that the composition, structural order, optical properties and morphology of the products can be adjusted by careful selection of synthesis parameters. The nature of the salt eutectic and precursor concentration in the melt have an especially large influence, with ZnCl2being a reactive solvent. This novel synthesis route provides access to easily processable materials with improved optical absorption in the visible range that can be used as composite photocatalysts, CO2adsorbents or nanocomposite fillers. This journal is
- Fettkenhauer, Christian,Weber, Jens,Antonietti, Markus,Dontsova, Dariya
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- Studies of Cyanamide Derivatives. Part 110. A facile Synthesis of 2,4,6-Triureido-1,3,5-triazine and 2-Amino-4,6-diureido-1,3,5-triazine
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2,4,6-Triureido-1,3,5-triazine and 2-amino-4,6-diureido-1,3,5-triazine were readily synthetized in high yields, 94 and 85percent respectively, by the alcoholysis of 2,4,6-tris(cyanoamino)-1,3,5-triazine and 2-amino-4,6-bis(cyanoamino)-1,3,5-triazine in the presence of hydrogen chloride
- Iio, Kokoro,Ichikawa, Eiichi
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- Dramatic visible photocatalytic performance of g-C3N4-based nanocomposite due to the synergistic effect of AgBr and ZnO semiconductors
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In this study, we synthesized a novel visible-light-driven photocatalyst with excellent photocatalytic activity, g-C3N4/AgBr/ZnO, as a ternary nanocomposite for pollutant degradation via a facile method. This coupling was favorable due to charge transfer between the semiconductors to yield a Z-scheme photocatalysis system, and thus the separation of photo-excited electron–holes was improved. The structure, morphology, and optical properties of the photocatalyst were determined by using characterization techniques, including X-ray diffraction, transmission electron microscopy, scanning electron microscopy with energy dispersive X-ray spectroscopy and its elemental mapping, N2 adsorption-desorption analysis, ultraviolet-visible diffuse reflectance spectroscopy, photoluminescence, fourier transform infrared spectra, and zeta potential measurements. The photocatalytic activity of the g-C3N4/AgBr/ZnO heterostructure was evaluated with different weight ratios during the degradation of the cationic pollutant methylene blue (MB) under exposure to visible light. The optimal photocatalyst with a g-C3N4 content of 30% exhibited superior activity during the degradation of MB and the rate constant of 0.041 min?1 was about 4.6 times higher than the rate constant of the pure g-C3N4. In addition, we assessed the photosensitization of MB and its effect on the photodegradation process. We propose a possible mechanism to explain the photocatalytic activity of the prepared ternary nanocomposite based on experiments with reactive species scavengers. Finally, the reusability and stability of the photocatalyst was investigated after four cycles.
- Boorboor Azimi, Elham,Badiei, Alireza,Hossaini Sadr, Moayad
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- Dicyandiamide preparation method
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The invention provides a dicyandiamide preparation method, which comprises: mixing lime nitrogen and water to carry out a hydrolysis reaction, and introducing carbon dioxide to carry out a decalcification reaction to obtain calcium carbonate and a cyanamide aqueous solution; filtering the cyanamide aqueous solution, and filtering out particles to obtain a pure cyanamide aqueous solution; heating and polymerizing the pure cyanamide aqueous solution to obtain a dicyandiamide aqueous solution; and filtering, cooling, filtering and drying the dicyandiamide aqueous solution to obtain dicyandiamidecrystals. By adopting the method, impurities such as calcium oxide, calcium hydroxide and calcium carbonate in dicyandiamide are removed, and the quality of a dicyandiamide product is improved.
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Paragraph 0022-0025; 0028-0030; 0033-0035; 0038-0040; 0043-
(2021/01/24)
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- LOW-ENERGY CONSUMPTION PROCESS WITH REDUCED AMMONIA CONSUMPTION, FOR THE PRODUCTION OF HIGH-PURITY MELAMINE THROUGH THE PYROLYSIS OF UREA, AND RELATIVE PLANT
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A process is described, having a low-energy consumption and reduced ammonia consumption for the production of high-purity melamine, through the pyrolysis of urea, and the relative plant.
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Paragraph 0103-0123
(2020/02/13)
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- Prebiotic Origin of Pre-RNA Building Blocks in a Urea “Warm Little Pond” Scenario
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Urea appears to be a key intermediate of important prebiotic synthetic pathways. Concentrated pools of urea likely existed on the surface of the early Earth, as urea is synthesized in significant quantities from hydrogen cyanide or cyanamide (widely accepted prebiotic molecules), it has extremely high water solubility, and it can concentrate to form eutectics from aqueous solutions. We propose a model for the origin of a variety of canonical and non-canonical nucleobases, including some known to form supramolecular assemblies that contain Watson-Crick-like base pairs.The dual nucleophilic-electrophilic character of urea makes it an ideal precursor for the formation of nitrogenous heterocycles. We propose a model for the origin of a variety of canonical and noncanonical nucleobases, including some known to form supramolecular assemblies that contain Watson-Crick-like base pairs. These reactions involve urea condensation with other prebiotic molecules (e. g., malonic acid) that could be driven by environmental cycles (e. g., freezing/thawing, drying/wetting). The resulting heterocycle assemblies are compatible with the formation of nucleosides and, possibly, the chemical evolution of molecular precursors to RNA. We show that urea eutectics at moderate temperature represent a robust prebiotic source of nitrogenous heterocycles. The simplicity of these pathways, and their independence from specific or rare geological events, support the idea of urea being of fundamental importance to the prebiotic chemistry that gave rise to life on Earth.
- Menor Salván,Bouza, Marcos,Fialho, David M.,Burcar, Bradley T.,Fernández, Facundo M.,Hud, Nicholas V.
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p. 3504 - 3510
(2020/10/02)
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- Synthetic method for 1,3,5-triazine-2,4,6-triamine
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The invention discloses a synthetic method for 1,3,5-triazine-2,4,6-triamine. The synthetic method for 1,3,5-triazine-2,4,6-triamine is characterized by comprising the following steps: taking cyanoguanidine as a starting material; dispersing the cyanoguanidine and 5-amino-1H-tetrazole in distilled water; then dropwise adding a small amount of concentrated hydrochloric acid, after dropwise adding is finished, heating to refluxing, then carrying out cooling crystallization, separating out solids, filtering under reduced pressure to obtain a filter cake, cleaning and drying the filter cake undervacuum to obtain a target compound 1,3,5-triazine-2,4,6-triamine. By the method, the reaction temperature is greatly reduced, a reaction process is gentle, requirements for a reaction container and equipment are low, and the synthetic method is simple and convenient to operate.
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Paragraph 0022; 0027; 0028; 0030-0042
(2018/10/19)
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- SYSTEM AND PROCESS FOR MELAMINE PRODUCTION BY GAS-PHASE QUENCHING METHOD OF ENERGY EFFICIENT AND COST SAVING TYPE
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A system and process for melamine production by gas-phase quenching method and its process are provided. The said system includes a urea scrubber, after which a fluidized bed reactor, a hot-air cooler, a hot-air filter, a crystallizer and a melamine collector are installed in series successively, where the said melamine collector is connected to the said urea scrubber and the said fluidized bed reactor is connected to a carrier gas pre-heater which is connected to a carrier gas compressor; the said system further includes a gas-liquid separator which is connected to the said urea scrubber which is connected to a crystallizer; wherein a cool air blower is provided between the said gas-liquid separator and the crystallizer. The production system of the invention has the advantages of high productivity, stable operation, low energy consumption, low investment and high economic value of tail gas.
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(2014/01/07)
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- METHOD FOR PRODUCING AND PURIFYING MELAMINE
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The invention relates to the technique for producing melamine by converting urea into melamine using a non-catalytic method at high pressure, as a whole, as well as to a stage of removing dissolved gases from an aqueous solution of crude Melamine, and can be used in commercial production of melamine. The method for producing melamine comprises a stage of converting urea into melamine at increased temperature and pressure with the formation of a gas-liquid reaction mixture containing melamine, ammonia, carbon dioxide and impurities, and a melamine separation stage. In order to separate melamine, the gas-liquid reaction mixture is cooled with lowering pressure and contacting with an aqueous medium, resulting in the formation of an aqueous solution of crude melamine and the partial removal of dissolved gases. The melamine solution obtained is allowed to stand in order to decompose a part of impurities, the pressure and the temperature are lowered, and the dissolved gases are removed from the aqueous solution of crude melamine using the proposed method by means of blowing water vapour through this solution with simultaneous ammonia introduction. An alkali metal hydroxide solution is added to the resultant melamine solution and melamine is separated from the solution by crystallization. The technical result which can be produced when using this invention involves increase of melamine purity and ensuring independence of its purity from the process parameters fluctuations. Melamine-formaldehyde resins prepared on the base of melamine produced by the proposed method have a high degree of transparency.
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Page/Page column 3; 5-6
(2012/06/05)
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- Low-energy-consumption process for the production of high-purity melamine, through the pyrolysis of urea and relative equipment
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A process for the production of high-purity melamine comprising: a) separating a biphasic liquid-gas effluent product in a pyrolysis reaction of urea in a liquid stream of raw melamine (3) and a first stream of anhydrous off-gas (15); b) putting said liquid stream (3) in contact with a stream of gaseous anhydrous NH3 (13) and forming a liquid stream of raw melamine impoverished in CO2 (4) and a second stream of anhydrous off-gas (16); c) putting said first and second anhydrous off-gas streams (15,16) in contact with at least one aqueous washing stream (32) and forming an aqueous stream (20) and a stream of damp off-gas (19); d) removing from said aqueous stream (20) at least a part of the CO2 contained therein, and forming a stream (22) comprising the CO2 removed and an aqueous stream (21) comprising melamine and impoverished in CO2; e) recovering the melamine contained in said liquid stream (4) and the melamine contained in said aqueous stream (21) through crystallization by cooling, with the formation of a stream (10) of crystallized melamine and a stream (23) of mother liquor. The present invention also relates to the equipment for effecting the above process. img id="iaf01" file="imgaf001.tif" wi="247" he="132" img-content="drawing" img-format="tif"/>
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(2011/11/13)
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- LOW-ENERGY-CONSUMPTION PROCESS FOR THE PRODUCTION OF HIGH-PURITY MELAMINE, THROUGH THE PYROLYSIS OF UREA, AND RELATIVE EQUIPMENT
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A low-energy-consumption process is described for the production of high-purity melamine, through the pyrolysis of urea, by the collection and purification of the melamine in aqueous solution produced in the pyrolysis reactor, and its separation by crystallization. The present invention also relates to the equipment for effecting the above process.
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Page/Page column 6-7
(2011/11/13)
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- Formation of pyrimidin-2-ylcyanamide and 2-aminopyrimidine in the reaction of aniline derivatives with cyanamide and dimethylamino-1-pyridyl-2-propenone
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Substituted o- and p-nitroanilines and m-benzylaminoanilines in the reaction with cyanamide failed to yield the corresponding arylguanidines, and in the presence of 3-dimethylamino-1-(3-pyridyl)-2-propen-1-one formed 4-pyridyl-substituted pyrimidin-2-ylcyanamides and 2-amino-pyrimidines.
- Koroleva,Ignatovich, Zh.V.,Ignatovich,Gusak
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scheme or table
p. 1222 - 1226
(2011/12/01)
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- Generation of melamine polymer condensates upon hypergolic ignition of dicyanamide ionic liquids
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The reaction of dicyanamide ionic liquids with nitric acid results in hypergolic ignition and the formation of a stable precipitate. The precipitate consists of cyclic triazines, including melamine and its polymers, such as melam and melem (see scheme). This study introduces a novel approach to the synthesis of cyclic azines without resorting to high temperatures and pressures. Copyright
- Chingin, Konstantin,Perry, Richard H.,Chambreau, Steven D.,Vaghjiani, Ghanshyam L.,Zare, Richard N.
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experimental part
p. 8634 - 8637
(2011/11/07)
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- METHOD OF MAKING CYCLIC GUANIDINE FROM DICYANDIAMIDE AND COATING COMPOSITIONS CONTAINING SAME
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The present invention is directed to a method for preparing a cyclic guanidine comprising reacting (i) a cyanamide, (ii) a polyamine, and (iii) a weak acid. The present invention is also directed to a coating composition comprising the cyclic guanidine.
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Page/Page column 18
(2011/10/05)
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- METHOD FOR PRODUCING MEALMINE
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A process for the preparation of melamine by decomposition of urea with the use of a catalyst, the catalyst comprising a) 10-90% by weight of zeolite,b) 10-90% by weight of a matrix comprising silica, alumina, silicon aluminum oxides and/or clay minerals, andc) 0-10% by weight of additives and the total content of nickel and vanadium in the catalyst being less than 500 ppm.
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Page/Page column 3
(2010/08/07)
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- PROCESS FOR THE PREPARATION OF NITROGEN-CONTAINING COMPOUNDS
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Process for the preparation of a nitrogen-containing compound, comprising the steps of: a) bringing N2, optionally NH3 and optionally a recycle stream together with a carbon- and hydrogen-containing compound or a carbon-containing compound and H2 to form a reaction mixture, whereby the ammonia in the reaction mixture, if present, originates for at least 30 wt. % from the recycle stream; b) bringing the reaction mixture in contact with a catalyst at a temperature lying between 200° C. and 800° C. and at a space velocity lying between 102 and 106 ml/(g.h), said catalyst containing a metal M1 on a support, M1 being chosen from the group consisting of metals in group 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12 of the IUPAC Periodic Table of Elements or mixtures thereof, whereby the nitrogen-containing compound is formed; c) optionally separating, subsequent to step b), a portion of between 1 and 99 vol. % off from the reaction mixture, said portion being the recycle stream.
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Page/Page column 4
(2010/03/31)
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- IMPROVED PROCESS FOR THE TREATMENT OF RETENTATE IN A MELAMINE PRODUCTION PLANT
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A process is described for increasing the efficiency and overall yield of the synthesis process of melamine by treatment of the deammoniated and neutralized crystallization mother liquor of melamine, characterized in that it comprises the following operational phases: a) subjecting the stream of said mother liquor containing OATs and melamine to one or more ultrafiltration steps, with the production of : (i) a permeate consisting of an aqueous solution containing melamine and the sole soluble fraction of OAT and : (ii) a retentate consisting of a concentrated colloidal aqueous suspension comprising the fraction of OAT in excess with respect to the soluble fraction; the purpose of step a) being to reduce the volume of retentate thus obtained to the minimum; b) subjecting the retentate deriving from phase a) to a decomposition treatment by hydrolysis at a temperature ranging from 27O0C to 3000C, with the formation of a gaseous stream, consisting of NH3, CO2 and water vapour, and a liquid stream; said retentate leaving phase a) being brought to the temperature of the decomposition treatment by mixing with an aqueous stream having a temperature which is such that the stream resulting from the mixing has a temperature ranging from 2700C to 3000C; c) subjecting the liquid stream coming from phase b) to stripping treatment with the separation of a further gaseous stream consisting of NH3, CO2 and water vapour, and a liquid stream substantially free of organic compounds.
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Page/Page column 22-26
(2009/03/07)
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- PROCESS FOR THE PREPARATION OF MELAMINE
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The present invention relates to a non-catalytic process for the preparation of melamine comprising: a) reacting molten urea in a reaction section at a pressure of 4.5 to 15 MPa to produce a reaction mixture containing molten melamine and reaction off-gases; b) vaporizing the molten melamine in said reaction mixture in a vaporization section to produce a gaseous mixture comprising the vaporized melamine and the reaction off-gases at a pressure of 4.5 to 15 MPa; c) quenching the gaseous mixture obtained from step b) by contact with an aqueous ammonium carbamate solution; and d) isolating melamine; and to a combined process for the preparation of urea and melamine, wherein melamine is prepared in accordance to the above method wherein at least part of the concentrated aqueous ammonium carbamate solution is transferred to an urea plant as at least part of the feed stock, urea is prepared utilizing said concentrated aqueous carbamate solution and urea obtained from said preparation step is supplied in molten form to the reacting step a).
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Page/Page column 12
(2009/07/25)
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- Process for producing high-quality melamine from urea
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A process for high-pressure, liquid phase conversion of urea into melamine is disclosed, where molten urea is fed to a first reaction zone (S1) where the melamine melt is under mechanical agitation, and a heat input (Q1) is provided to maintain the endothermic reaction, and the liquid is then passed to a second reaction zone (S2) kept at a lower temperature and where further agitation is provided. Embodiments of plants adapted to carry out the process are also disclosed, including multiple stirred reactors in cascade and a single reactor with multiple internal compartments defining said first and second reaction zones.
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Page/Page column 10
(2009/12/05)
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- Process for the preparation of melamine
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The invention relates to a process for the preparation of melamine which process comprises at least the following steps: a. feeding ammonia and hydrogen cyanide, either separately or combined, to a first reactor that contains a catalyst that comprises at least one group 11 element and which reactor is maintained at a pressure of at least 2 bar and a temperature of 300-500 °C, at a space velocity lying between 102 and 106 ml/(g.hr), whereby a gaseous mixture (a) is formed comprising at least melamine, b. optionally purifying mixture (a) producing a melamine containing mixture (b), c. separating at least a part of the formed melamine thereby forming reaction mixture (c) and separated melamine The invention also relates to a process for the preparation of melamine, which process comprises at least the following steps: i. feeding methane and ammonia to a pre- reactor which pre- reactor is maintained at a temperature between 700 and 1500 °C whereby a gaseous mixture (i) is formed comprising at least hydrogen cyanide, ii. purifying mixture (i) thereby forming a mixture (ii) that contains at least hydrogen cyanide, a. feeding hydrogen cyanide from mixture (ii) and ammonia, either separately or combined, to a first reactor that contains a catalyst and which reactor is maintained at a pressure of at least 2 bar and a temperature of 300-500 °C, at a space velocity lying between 102 and 106 ml/(g.hr), whereby a gaseous mixture (a) is formed comprising at least melamine, b. optionally purifying mixture (a) producing a melamine containing mixture (b), c. separating at least a part of the formed melamine thereby forming reaction mixture (c) and separated melamine The invention further relates to the melamine obtained by the processes.
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Page/Page column 6
(2009/07/17)
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- A process for drying melamine
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A process is described for drying melamine wet cakes, comprising the steps of: a) providing a turbo-dryer (T) comprising a cylindrical tubular body (1) having a heating jacket (4), inlets and outlets (5, 6) and a bladed rotor (7) rotatably supported therein; b) feeding a continuous flow of a melamine wet cake into the turbo-dryer (T), the internal wall (9) of which is maintained at a temperature of at least 220°C; c) feeding a continuous flow of a gas selected from air or nitrogen into the turbo-dryer (T); d) subjecting the flow of melamine wet cake to the mechanical action of the bladed rotor (7) rotating at a speed of at least 200 rpm, with consequent centrifugation of the wet cake against the heated wall (9), thus causing the instantaneous evaporation of the water contained into the cake, and transport of the latter towards the outlet (6); e) continuously discharging, after an average residence time of less than 1 minute, a flow of melamine crystals having a humidity content of less than 0.1%.
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Page/Page column 4
(2008/06/13)
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- PROCESS FOR GENTLY COOLING AND CRYSTALLIZING MELAMINE FROM A MELAMINE MELT OR FROM THE GASEOUS PHASE
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Process for cooling and crystallizing solid melamine from the gaseous phase or from melamine melts as they develop in technical processes used to produce melamine, characterized in that the melamine-containing process gases or melamine melts are introduced into a liquid, organic phase at high pressure, said phase comprising polyvalent alcohols such as ethylene glycol, glycerine or their homologous series or of amines such as ethanol amines. Mixtures of both groups of compounds are suitable as well. The advantage of this process is that the hot melamine is cooled very quickly without forming thermal decomposition products and that during quenching no reaction of the melamine with the solvent occurs as in the case with a water quench. Additionally not only the formation of higher deammonation products such as melam and melem is prevented while reducing the pressure from the reactor, but also higher deammonation products of the melamine possibly still contained in the melt, such as melam and melem, are partially converted back into melamine.
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Page/Page column 10-11
(2008/06/13)
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- IMPROVED PROCESS FOR THE PRODUCTION OF MELAMINE WITH AN INCREASED YIELD
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A process is described for recovering from the crystallization mother liquor of melamine both the residual saturation melamine and oxyaminotriazines (OAT), comprising an ultrafiltration of the flushing mother liquor for separating the OAT in the colloidal state from the mother liquor containing them, said ultrafiltration producing a permeate and a retentate in aqueous solution, the permeate impoverished in OAT being recycled to the preparation step of the aqueous solution of raw melamine, said process being characterized in that the retentate is recycled to the synthesis reactor.
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Page/Page column 16-19
(2008/06/13)
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- process for the integrated production of urea and melamine
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A process for the integrated production of urea and melamine synthesized from at least part of said urea, comprising the steps of: - carrying out a urea synthesis in a first urea synthesis reactor (16), fed with ammonia and carbon dioxide, obtaining a reaction mixture comprising urea and ammonium carbamate, - carrying out melamine synthesis, with formation of off-gas comprising ammonia and carbon dioxide, - carrying out a further urea synthesis in a second urea synthesis reactor (28), fed with said off-gas, with production of a respective reaction mixture comprising urea and ammonium carbamate, - feeding said reaction mixture produced by said first reactor (16) and said reaction mixture produced by said second reactor (28) to a urea recovery unit (18), obtaining urea and an ammonium carbamate aqueous solution, - feeding said ammonium carbamate aqueous solution obtained in said recovery unit (18) to said second urea synthesis reactor (28).
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Page/Page column 3-6
(2008/06/13)
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- Process for gently cooling and crystallizing melamine from a melamine melt or from the gaseous phase
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Process for cooling and crystallizing solid melamine from the gaseous phase or from melamine melts as they develop in technical processes used to produce melamine, characterized in that the melamine-containing process gases or melamine melts are introduced into liquid, organic phase at high pressure, said phase comprising polyvalent alcohols such as ethylene glycol, glycerine or their homologous series or of amines such as ethanol amines or a mixture of both groups. The advantage this process is that the hot melamine is cooled very quickly without forming thermal decomposition products and that during quenching no reaction of the melamine with the solvent occurs, the formation of higher deammoniation products such as melam and melem is prevented and higher deammoniation products of the melamine such as melam and melem, are partially converted back into melamine.
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Page/Page column 5
(2008/06/13)
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- METHOD AND DEVICE FOR CRYSTALLIZING MELAMINE
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The invention relates to a method for the two-step crystallization of melamine, characterized in that an OAT-containing aqueous melamine solution is subjected to: a) a first crystallization step under vacuum, with a pH value greater than 11 and at a temperature TK1, during which a majority of the melamine crystallizes, which is fed to subsequent reprocessing whereby obtaining a first OAT-containing and melamine-containing mother liquor, afterwards; b) at least a portion of the first OAT-containing and melamine-containing mother liquor is subjected to at least one second crystallization step under vacuum, with a pH value greater than 11 and at a temperature TK2 whereby TK2 K1, during which another portion of the melamine crystallizes, which is returned to the melamine process whereby obtaining a second OAT-containing mother liquor that is fed to a waste-water reprocessing step. The nearly complete recycling of the melamine from the first mother liquor makes it possible, with an efficient use of energy, to increase the number of uses of urea in the entire process.
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Page/Page column 13-14
(2008/06/13)
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- HIGH PRESSURE METHOD FOR PRODUCING PURE MELAMINE IN A VERTICAL SYNTHESIS REACTOR
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The invention relates to a high pressure method for producing pure melamine by pyrolyzing urea in a vertical synthesis reactor. The invention is characterized in that the synthesis reactor has three stages vertically arranged above one other, whereby: a) in the first i.e. uppermost stage, the smaller portion of the total amount of urea is introduced into the central tube of a first tank reactor whereby forming a first melamine-containing reaction medium; b) in the second i.e. middle stage, the first melamine-containing reaction medium as well as the larger portion of the total amount of urea is introduced into the central tube of a second tank reactor whereby forming a second melamine-containing reaction medium, after which; c) in the third i.e. lowermost stage, the second melamine-containing reaction medium is introduced into a vertical tubular flow reactor whereby forming a raw melamine melt that is subsequently processed in any manner whereby obtaining pure melamine. This makes it possible to achieve a more uniform conversion of urea, a more mild and corrosion-reducing supply of reaction heat, and for the reaction to be optimally carried out as well as to achieve a complete reaction of the urea in the melamine synthesis reactor. In comparison to other melamine methods, the invention provides a more compact, economical and efficient synthesis of melamine.
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Page/Page column 10-12
(2008/06/13)
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- METHOD FOR PRODUCING MELAMINE
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The invention concerns a method for producing melamine by dissolving urea, in which solid, liquid or gaseous media other than the gas mixture consisting of the components formed during the reaction is used to desublime the melamine from the gas phase.
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Page/Page column 1; 5-6; 7-8
(2008/06/13)
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- METHOD FOR PRODUCING MELAMINE WITH HEAT RECOVERY
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The invention relates to a method for producing melamine by decomposing urea inside a fluidised bed reactor, during which the hot reaction gas is cooled inside a gas cooler, and the obtained heat is directly used for pre-heating the fluidising gas required for creating the fluidised bed.
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Page/Page column 1; 5-8
(2008/06/13)
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- METHOD FOR THE TREATMENT OF TRIAZINE-CONTAINING WATER OF A MELAMINE PLANT
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The invention relates to a method for treating triazine-containing water of a melamine plant. Said method is characterized in that the water containing ionic and non-ionic triazines in a dissolved form is fed to at least one membrane filtration unit (MF), the water is separated into an ionic triazine-rich fraction and a non-ionic triazine-rich fraction in the membrane filtration unit (MF), whereupon the ionic triazine-rich fraction is discharged and the non-ionic triazine-rich fraction is redirected into the melamine plant. The inventive method allows a great portion of the melamine contained in the triazine-containing water to be redirected into the process while the yield is increased along the entire melamine process. Furthermore, the need for fresh water in the wet part of the melamine plant is decreased. The disclosed method can be carried out continuously and in liquid phase.
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Page/Page column 10-14
(2008/06/13)
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- IMPROVING THE MELAMINE YIELD OF CATALYTIC MELAMINE PRODUCTION PROCESSES
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The process to increase the melamine yield and improving the dust separation in the melamine production from urea in fluidized-bed catalytic processes comprises transferring the process gas of the fluid-bed reactor, which contains besides melamine non-converted isocyanic acid, melam, melem and other higher molecular nitrogen compounds, into a filter-reactor which consists of one or more ring-reactors filled with catalysts, in which the not yet converted isocyanic acid is converted to melamine, the higher molecular nitrogen compounds, especially melam and melem, are also re-converted to melamine by reaction with the ammonia in the process gas, and the catalyst fines still present in the process gas of the fluidized-bed reactor are removed.
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Page/Page column 7-8
(2008/06/13)
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- Transformation of one of two C≡N groups of o-dicyanobenzene in the presence of cyanoguanidine. Crystal and gas-phase structure of 2-(2′-cyanophenyl)-4,6-diamino-1,3,5-triazine
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The transformation of one C≡N group in o-dicyanobenzene in the presence of cyanoguanidine yielding the melaminium derivative in crystalline form has been performed. In the final step of the closing of 1,3,5-triazined ring both hydrogen atoms of one amine
- Janczak, Jan,Kubiak, Ryszard
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- METHOD AND DEVICE FOR PRODUCING MELAMINE UNDER HIGH PRESSURE
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The invention relates to a method for producing melamine from urea under high pressure, comprising a phase transition device (1) for transitioning a melamine melt into the gas phase. To this end, heat is fed to the phase transition device (1) via at least one heat exchanger (2) and at least one substance flow (3) acting as a stripping medium is also fed to the phase transition device. The inventive method is characterized in that at least a portion of the melamine melt is guided into the phase transition device (1) in liquid form and, once inside, is guided in a counterflow to the rising gaseous phase or has fluidized beds. The invention also relates to a phase separating device for carrying out said method. This enables a simple purification of the gaseous phase before the separation.
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Page/Page column 6-14
(2008/06/13)
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- METHOD AND DEVICE FOR PRODUCING MELAMINE IN A SINGLE-PHASE TUBULAR REACTOR
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The invention relates to a method and a device for producing melamine by means of the thermal conversion of urea. The invention is characterised in that: a) urea is reacted to form melamine at least partially under reaction conditions wherein an educt, an intermediate and/or an end product are present in a supercritical state; and b) the mixture consisting of at least one educt, an intermediate and/or an end product essentially forms a homogeneous phase, especially all educts, intermediates, and/or end products being in a complete solution. The single-phase reaction results in an especially efficient reaction.
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Page/Page column 5
(2008/06/13)
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- TWO-STAGE REACTOR FOR THE PRODUCTION OF MELAMINE
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The invention relates to a method for the catalytic production of melamine by the decomposition of urea in particular on solid catalysts using a main and post reactor. A catalyst of low Lewis acidity is employed in the main reactor and in the post reactor a catalyst is employed with the same or preferably a greater Lewis acidity.
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Page/Page column 7-8
(2008/06/13)
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- Process for the production of high purity melamine from urea
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A method for purifying melamine comprising impurities like ureido-melamine, oxotriazines, melam, melem, comprises the step of putting into contact at a temperature comprised between 340° C. and 410° C. and at a pressure comprised between 8 and 17 MPa a melamine melt with a bed of a catalyst thus obtaining melamine with a purity of at least 99%.
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- Catalyst for melamine production
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A novel electrolytic method for preparing the catalyst (active aluminum oxide) for melamine synthesis and a process for catalytic synthesis of melamine from urea are proposed.
- Moiseeva,Kurylev,Pomerantsev,Tubolkin
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p. 1883 - 1884
(2007/10/03)
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- Sonodynamic therapy using an ultrasound sensitizer compound
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A method of treatment of a human or animal body by sonodynamic therapy in which a sensitizer agent is administered to the body and the body is exposed to ultrasound to achieve a cytopathogenic effect at a site therein, wherein the said sensitizer agent is a physiologically tolerable substance which is capable of enhancing the cytopathogenic efficacy of said sonodynamic therapy. Preferably, the sensitizer agent is a water-soluble polymer compound or a conjugate thereof.
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- Process for the preparation of urea
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In the present process for the preparation of urea, an off-gas stream released during the synthesis of melamine in a high-pressure melamine process which consists predominantly of ammonia and carbon dioxide, is introduced into at least one high-pressure section of a urea stripping plant and is used in the synthesis of urea. The off-gas stream can be used directly without any further treatment.
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- Articles having a chambray appearance and process for making them
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Articles made from melamine fibers and aramid fibers are dyed at selected conditions and with selected dyes such that the aramid fiber is dyed but the melamine fiber is not.
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- Method of alkylating of triazine derivatives
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A method for alkylation of at least one or more amino groups or mono-substituted amino groups, each on a carbon atom of a triazine ring of 1,3,5-triazine derivatives (melamine, melamine derivatives and various kinds of guanamine derivatives and the like), which includes reacting the 1,3,5-triazine derivatives having at least one or more amino groups or mono-substituted amino groups with alcohols in the presence of a catalyst of a metal of group VII and/or group VIII in the periodic table. The object of the invention is to provide a method for alkylation of 1,3,5-triazine derivatives, which includes alkylating amino groups or mono-substituted amino groups in carbon atoms of a 1,3,5-triazine ring, whereby substituted 1,3,5-triazine derivatives which are a group of useful compounds and which are widely used as intermediates of fine chemicals such as agricultural chemicals, medications, dye-stuffs, paints and the like, as resin materials and as flame-retardant materials can be easily produced in high yields.
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- Liquid-crystalline compounds
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Liquid-crystalline compounds of the formulae I and II, where Z1 is the radical of an m-valent alcohol an m-valent acid or certain trivalent triazine derivatives; Z2 is an n-valent radical of a monocyclic or polycyclic aromatic compound; X1 is a chemical bond or --CO--; X2 is --O--, --S--, --CO--O--, --O--CO--, --SO2 --, --SO2 --O--, --O--SO2 --O--, --NR4 --, --CO--NR4 --NR4 --O-- or --CO--N4 is H or C1 -C8 -alkyl; m and n are 3 to 6; R1 is a C2 -C20 -bridge having 2 to 12 bridging members, which may be interrupted by --O--, --S-- or --NR4 --, each of these hetero units being separated by at least 2 carbon atoms; Y is a chemical bond, --O--, --S--, --CO--O--, --O--CO--, --NR4 --, --CO--NR4 -- or --NR 4 --CO--; M is a mesogenic group. These compounds are suitable for the production of optical and electro-optical data carriers and display elements.
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- Defined oligomeric liquid-crystalline compounds having smectic liquid-crystalline phases
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Liquid-crystalline compounds of the formulae I and II; where Z1 is the radical of an m-valent alcohol an m-valent acid or certain trivalent triazine derivatives; Z2 is an n-valent radical of a monocyclic or polycyclic aromatic compound; X1 is a chemical bond or -CO-; X2 is -O-, -S-, -CO-O-, -O-CO-, -SO2 -, -SO2 -O-, -O-SO2 -O-, -NR4- , -CO-NR4 -, -NR4 -O- or -CO-N4 is H or C1 -C8 -alkyl; m and n are 3 to 6; R1 is a C2 2-C20 -bridge having 2 to 12 bridging members, which may be interrupted by -O-, -S- or -NR4 -, each of these hetero units being separated by at least 2 carbon atoms; Y is a chemical bond, -O-, -S-, -CO-O-, -O-CO-, -NR4 -, -CO-NR4 - or -NR4 -CO -; M is a mesogenic group. These compounds are suitable for the production of optical and electro-optical data carriers and display elements.
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- Coated pigment and colorant composition
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A pigment coated with a water-insoluble organic surface modifier can be prepared by: (a) preparing a mixture of water and a substantially water-insoluble organic surface modifier; (b) introducing the mixture, under pressure, into a conduit having a diameter-decreased portion and a turning portion wherein the diameter-decreased and turning portions provide accelerated flow through the diameter-decreased portion and mutual collision of the accelerated mixture or collision of the accelerated mixture against a wall of the conduit, thereby obtaining an aqueous dispersion in which the surface modifier is homogeneously dispersed in water; (c) mixing the aqueous dispersion with a pigment, thereby providing a pigment coated with the surface modifier; and (d) isolating the coated pigment.
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- Optically active phenoxypropionic esters
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Optically active compounds of the formula I STR1 where R is C1 -C12 -alkyl or -perfluoroalkyl in which one or two non-adjacent CH2 or CF2 groups can also be replaced by --O-- and/or --CO-- and/or --CO--O-- and/or --CH=CH-- and/or --CH-halogen-- and/or --CHCN-- and/or --0--CO--CH-halogen-- and/or --O--CO--CHCN--, or is C1 -C12 -alkyl which can have a terminal chemically reactive group and in which a CH2 group can be replaced by --O--, A1 and A2 are each, independently of one another, 1,4-phenylene which is unsubstituted or substituted by one or two F and/or Cl and/or Br atoms and/or CH3 groups and/or CN groups and in which one or two CH groups can also be replaced by N, 1,4-cyclohexylene in which one or two non-adjacent CH2 groups can also be replaced by --O-- and/or --S--, 1,4-piperidinediyl, 1,4-bicyclo[2.2.2]octylene, 2,6-naphthalenediyl, decahydro-2,6-naphthalenediyl or 1,2,3,4-tetrahydro-2,6-naphthalenediyl, A3 is unsubstituted or substituted phenyl, Z is --CO--O--, --O--CO--, --CH2 CH2 --, --OCH2 --, --CH2 O--, --C C-- or a single bond and m is 0, 1, 2 or 3.
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- Glycoluril salts and a process for the preparation thereof
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This invention is directed to glycoluril-triazine salts of the formula: STR1 wherein the R's are hydrogen and hydrocarbon radicals, n is 1 to 4, and m is 4-n. These materials are suitable for modifying polymers, such as polyurethanes and flameproofing polyamides.
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