Papers by Keyword: Nitration

Abstract: Nowadays the development of biodiesel production as an alternative renewable energy became crucial. The reusability of enzymes as biocatalysts in biodiesel production has limitations and can be improved by the immobilization process onto the appropriate solid support, such as polyethersulfone (PES). Polyethersulfone has been synthesized utilizing microwave-assisted reaction method (400 W, 170 °C, 60 minutes). Nitration reaction of PES was performed by refluxing the synthesized PES with the mixtures of H₂SO₄ (0 °C, ± 30 minutes) and HNO₃ (25 °C, 4 hours). The –NO₂ groups of the synthesized PES-NO₂ was subsequently reduced to be PES-NH₂ using SnCl₂.2H₂O as reducing agent by reflux method (60 °C, ± 3 hours). The structure of PES and its derivatives was confirmed by FTIR and ¹H-NMR. Candida antarctica lipase was successfully immobilized onto the synthesized PES and its derivatives, which were confirmed by its FTIR spectra and its activity tests of the supernatants in hydrolyzing p-nitrophenol palmitate (pNPP) into p-nitrophenol (pNP). The results showed that the conversion percentage of pNPP to become pNP were 20.6% (free enzyme), 18.9% (PES-enzyme), and 3.7% (PES-NH₂-enzyme). The decrease in the supernatant enzyme activity showed that the enzyme has been successfully immobilized through physical adsorption onto the synthesized polymers.

Abstract: The results of metallographic studies show the effect of the layers thickness of multilayer metal material on the diffusion depth after chemical heat treatment. The accelerate diffusion model of diffusible element along layers boundaries is proposed.

Abstract: The processes of nitration of 2-methylimidazole to produce 2-methyl-4(5)-nitroimidazole are considered in this paper. The processes of nitration by mixture of nitric and sulfuric acids and nitrate salts of alkali metals were compared. It was found the nitration of nitrate salts of alkali metal proceeds smoother. The yield of the desired product 2-methyl-4(5)-nitroimidazole was 85 % and 95% in case of nitric acid and nitrate salt.

Abstract: Mixing processes are best understood in turbulent flows, where, ironically they are only understood in a statistical sense. Similarly, detailed analysis of the mechanisms of the realistic mixing process in deterministic laminar flows is nearly absent from literature. This experiment was implemented to investigate the comparable performance of reactive mixing at various perturbation; including continuous, periodic and chaotic. The experiment was designed to reveal the effects of perturbations on glycerin dissolution in nitric acid in stirred vessel. The ratio of glycerin (C₃H₅ (OH)₃) to nitric acid (HNO₃) is 1 : 3. The geometrical parameter was set to R₁/R₂ = 37.5/7, and an eccentricity of ε = 18.75 mm. The mixing time for dissolving fixed amounts of glycerin in fixed amounts of nitric acid was measured and compared to those from several different perturbations. It was found that mixing time for the exothermic reaction of glycerin nitration had been influenced by perturbations applied to fluid mixing. Comparable experiments have shown that mixing time in the glycerin-nitration reaction could be changed dramatically, along with various perturbations. This experiment results explicitly demonstrate the benefits of mixing performance from chaotic perturbations.

Abstract: 5,10,15-Tris(4-nitrophenyl)-20-hydroxylphenylporph-yrin was synthesized by a novel method which was for the nitration of the phenyl groups of 5-(4-hydroxylphenyl)-10,15,20- triphenylporphyin(MHTPP) using NaNO2 and trifluoroacetic acid(TFA) and characterized using mass spectrometry, NMR spectroscopy, UV-visible, IR spectrometry. The mild reaction conditions produced higher yields and minimum macrocyclic degradation. Its fluorescence spectra was studied compared with MHTPP and tetraphenylporphyrin(TPP). The results showed that the absorption and emission bands of the product experienced red shifts and the fluorescence intensity weakened compared with MHTPP and TPP.

Abstract: Nitration-oxidation lignosulfonate (NOLS) was prepared using lignosulfonate (LS) as raw material. The product was characterized by Fourier Transform Infrared spectroscopy (FT-IR). The performance as a drilling fluid additive was evaluated with regard to rhology, filtration and temperature resistance. The results showed that NOLS can improve the viscosity under room temperature, decrease the viscosity under high temperature and reduce the filtration more effectively than that of lignosulfonate, which display its good temperature resistance. So NOLS may be used as sustained release nitrogen fertilizer in agriculture as it was abandoned after the drilling process.

Abstract: The newly sulfated nanosolid superacid TiO₂/SO₄ prepared by sol-gel method was broadly characterized by acid base titration, XRD and TEM, which identified that the superfine solid TiO₂/SO₄ showing good dispersibility with average size of 27 nm belongs to kind of crystalline nanoparticles. With the help of the catalyst TiO₂/SO₄, the optimal reaction condition for direct transformation of pyrazole and nitrosonitric acid into 3, 5-Dinitropyrazole was n (pyrazol)=0.10 mol, m (TiO₂/SO₄ )＝1.5g, V(n-octannol)＝90mL, and V(nitrosonitric acid)＝50mL. Moreover, the optimal yield of the catalytic reaction reached up to 59.4% when the reaction time is 7 hours. The nanosolid superacid catalyst is still of high activity after regenerating eight times by calcination at 600^。C.

Abstract: In this paper, the preparation of 2, 6-diamino-3, 5-dinitropyridine (DADNP) were systematically investigated. The optimal method was found. The key parameters have been systematically studied, such as the synthesis route, temperature, solvent, time, the reactant ratio, and the purification route. The optimal route was confirmed and would have an important reference for pilot plant scale-up.

Abstract: Organic-inorganic Nano composite membranes were prepared by Sulfonated amine-poly(ether sulfone)s (S-APES)s and SiO2. S-APESs were prepared by nitration, reduction and sulfonation of poly(ether sulfone) (ultrason®-S6010). Poly(ether sulfone) was reacted with ammonium nitrate and trifluoroacetic anhydride to produce the nitrated poly(ether sulfone), and was followed by reduction using tin(Ⅱ)chloride and sodium iodide as reducing agents to give the amino-poly(ether sulfone). The S-APES was obtained by reaction of 1,3-propanesultone and the amino-poly(ether sulfone) (NH2-PES) with sodium methoxide. The different degrees of nitration and reduction of poly(ether sulfone) were successfully synthesized by an optimized process. Organic-inorganic nano composite membranes were obtained by mixing S-APES (45 %) with hydrophilic SiO2 (20 nm, 4-10 %) obtained by sol-gel process. Different contents of SiO2 of the S-APES were studied by FT-IR, 1H-NMR spectroscopy, differential scanning calorimetry (DSC), and thermo gravimetric analysis (TGA). Sorption experiments were conducted to observe the interaction of sulfonated polymers with water and methanol. The ion exchange capacity (IEC), a measure of proton conductivity, was evaluated. The nano composite membranes exhibit conductivities (25 °C) from 3.51 x 10-3 to 4.10 x 10-3 S/cm, water swell from 57.25 to 60.50 %, IEC from 0.68 to 0.73 meq/g, and methanol diffusion coefficients from 2.81 x 10-7 to 3.33 x 10-7 cm2/S at 25 °C.

Abstract: The machinery used in coal thermoelectrical plants usually is submitted to erosive wear. The erosive wear occurs mainly in the metallic pipe set of heat exchangers due the flow of hot gases carrying erosive particles. Jorge Lacerda’s thermoelectrical complex at Capivari de Baixo city holds seven power units, where two units use approximately 20 000 ASTM A178 heat pipes. The set is submitted to a semester maintenance schedule (preventive and corrective) where the damaged pipes are changed. So, in this work a set of erosive wear accelerated tests according ASTM G76 were performed in order to develop and specify materials and methods to diminish the erosive action caused by the combustion gases over the heat pipes. Specimens were coated with WC12Co and Cr3C2-25NiCr alloys using the HVOF technique and the coated specimens were tested at 450°C, the heat pipes working temperature. Silica was used as abrasive material at 30° and 45° impact angles, simulating a harder erosive condition than the real condition. The best performance coating at laboratory scale was later used in field condition. The results showed the coated specimen performance is better than the ASTM A178 alloy. The erosion resistance of the Cr3C2-25NiCr and WC12Co coatings is eight times higher than the uncoated alloy, and the coatings also presented a better corrosion resistance. This feature is important, because despite the erosive action the circulating gases also present a large amount of sulfur in their composition. Sulfur at lower temperatures forms H2SO4, causing intense corrosion of the pipes located at the heat exchangers colder parts. Based on the results and considering the coating costs the Cr3C2-25NiCr alloy was selected to coat a set of pipes mounted at the region of the heat exchanger with the most intense erosive wear. At the moment these coated tubes are in field operation and under observation regarding their performance in comparison with the uncoated pipes located at the same heat exchanger. The real operation conditions of the coated pipes will be estimated from the field life cycle analysis, and after all the cost-benefit of the studied coating.