Decomposition Of Pyridine Research Articles

Thermodynamic and kinetic study of NO reduction by pyridine/pyrrole during biomass tar reburning: the quantum chemical method approach

NOx emission is a serious problem during fossil fuel combustion. Novel reburning fuels, namely, nitrogen-containing tar compounds, including pyridine and pyrrole were taken into consideration for NO reduction and investigated by quantum chemical method. Theoretical calculation results show that pyridine could first decompose into small species, such as CN and hydrocarbon radicals, then reduce NO to N2. The decomposition of pyridine should overcome quite high energy barrier and adsorb a large amount of heat. This pathway may occur at high temperature zone, such as core flame zone of pulverized coal fired boiler. As soon as pyridine decomposes, the active intermediates (CN radical, etc.) could reduce NO very quickly. The direct reduction of NO by pyridine molecule should overcome lower energy barrier, which could occur at wider temperature range. Pyrrole is less thermostable than pyridine; the energy barriers of pyrrole cracking and direct reduction of NO stay at same level. Therefore, the reburning efficiency of pyrrole may be better at lower temperature than pyridine. Theoretical calculations indicate that nitrogen-containing tar compounds produced during biomass pyrolysis/gasification could have good performance for NO reduction in pulverized coal fired boiler as well as biomass or MSW furnace.

No.31 タール中窒素のモデル化合物の分解に対するリモナイトの触媒性能

No.31 タール中窒素のモデル化合物の分解に対するリモナイトの触媒性能

No.1 褐鉄鉱を用いるタール中窒素の分解除去 : 褐鉄鉱のピリジン分解性能に及ぼす共存ガスの影響(改質・処理・クリーン化(1)、熱分解・コークス(1))

No.1 褐鉄鉱を用いるタール中窒素の分解除去 : 褐鉄鉱のピリジン分解性能に及ぼす共存ガスの影響(改質・処理・クリーン化(1)、熱分解・コークス(1))

Fast photo-catalytic degradation of pyridine in nano aluminum oxide suspension systems

UV light can degrade pyridine to ammonia nitrogen at room temperature. The decomposition of pyridine under UV irradiation with the help of aluminum oxide powders was rarely studied. While with the assist of alumina, fast photo-catalytic degradation of pyridine to 100 percentage ammonia nitrogen was realized within an hour. The promising promotion phenomena were confirmed in opening other nitrogen heterocyclic compounds (NHCs) such as quinoline and 2,2′-bipyridine. Scanning electron microscopy images showed the alumina powder was about 100 nm in size. X-ray diffraction results indicated that the sample was mainly a-Al 20 3. Specific surface area of the sample was about 280 m 2/g determined by BET method. The optimum dosages of catalysts and effects of pH value were also tested. There was no clear absorbance of the alumina sample showed in the range of 200-420 nm. It is believed that the interaction between pyridine and alumina surface hydroxyl caused by chemisorptions weakened the carbon-nitrogen bond and led to the promotion of the decomposition.

Regeneration of activated carbons saturated with pyridine or phenol using supercritical water oxidation method enhanced with hydrogen peroxide

While activated carbon (AC) is widely employed for treating water resources contaminated with hazardous organic compounds, regeneration of AC after saturation has been a concerning issue. Supercritical water oxidation (SCWO) in a batch reactor was used to regenerate two commercial activated carbons (CAL and COCO) saturated with pyridine or phenol. BET surface area, pore volume and pore size distribution of CAL and COCO were characterized before and after their regeneration. Decomposition of pyridine and phenol was examined at 400, 450, 525 °C with the presence or absence of hydrogen peroxide. The SCWO regeneration efficiency was determined from the amount of pyridine or phenol adsorbed and desorbed in successive adsorption-regeneration cycles. Effects of SCWO on adsorption capacity of CAL and COCO were experimentally investigated. With SCWO enhanced by H 2O 2, adsorbed organic compounds could be converted to carbon dioxide, hydrogen and nitrogen.

ChemInform Abstract: Matrix-Controlled Photochemistry of Benzene and Pyridine.

Dewar benzene has been shown to be a primary product from the photolysis of benzene in low temperature argon matrices at 253.7 nm. This is the first observation of Dewar benzene product at this wavelength and a mechanism is proposed that involves benzene S{sub 1}-S{sub 2} state mixing induced by the matrix environment. Analogous experiments on the photolysis of pyridine show that the only primary products are isomeric species derived at least in part from a triplet state of pyridine, probably T{sub 1}. This is the first observation of photochemistry from the T{sub 1} state and may be the process responsible for the small values of {tau}{sub p} and {phi}{sub p} in pyridine. Analysis of the IR spectral bands points to the main product being Dewar pyridine although other isomers cannot be ruled out. In contrast to the gas phase, no decomposition of pyridine was found in matrices producing compounds such as acrylonitrile, ethyne, and hydrogen cyanide.

Nitrogen-doped multiwalled carbon nanotubes and their electrocatalysis towards oxidation of NO

Nitrogen-doped multiwalled carbon nanotubes (N-MWCNTs) were synthesized by thermal decomposition of pyridine and iron phthalocyanine over an iron catalyst in an atmosphere of ammonia. The N-MWCNTs thus obtained were analyzed by X-ray photoelectron spectroscopy. They were found to contain three types of nitrogen (N) atoms, namely pyridine-like, graphite-like, and molecular N. The effect of the pyridine-like N and the graphite-like N was investigated. The pyridine-like N is absorbing nitric oxide (NO) more easily than the graphite-like N. The N-MWCNTs with higher N content (especially the pyridine-like N) have higher catalytic activity (in terms of electrooxidation of NO) than those containing less N. The N-MWCNTs with high levels of pyridine N were incorporated into an electrode which suitable for sensing NO and for removal of NO due to its excellent electrocatalytic activity.

Direct synthesis of nitrogen-containing filamentous carbon on a high-percentage Ni-Cu catalyst

Nitrogen-containing catalytic filamentous carbon (N-CFC) of chemical composition NC18-NC104 has been synthesized by the decomposition of pyridine (Py) from gaseous mixtures with argon or H2 at 550–800°C on Ni/Al2O3 (Ni) and Ni-Cu/Al2O3 (Ni-Cu) high-percentage catalysts. The activity of the Ni-Cu catalyst in Py decomposition in mixtures with H2 is about one order of magnitude higher than its activity in Py/Ar mixtures (more than 70 g N-CFC per metal gram in 4.5 h at 750°C), which is interpreted as arising from the nickel-catalyzed hydrogenation of Py. The formation and growth of carbon fibers occurs through the decomposition of Py (from Ar/Py mixtures) and/or Py hydrodenitrification products (from H2/Py mixtures). The carbon material has been characterized by elemental analysis, low-temperature nitrogen adsorption, high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS). The effect of the noncatalytic reactions of Py and its transformation products on the composition and texture of N-CFC is discussed.

Pyridine adsorption and reaction on Mo(1 1 0) and C/N–Mo(1 1 0): experiment and modeling

The adsorption of pyridine (C 5H 5N) on clean and carbon/nitrogen-modified Mo(1 1 0) surfaces has been investigated using temperature-programmed desorption (TPD) and density-functional theory (DFT) calculations. Pyridine adsorbs and decomposes on Mo(1 1 0) and C/N–Mo(1 1 0) at temperatures less than 530 K. Molecular pyridine desorption on clean Mo(1 1 0) occurs at temperatures of 375 ± 5 K ( E ads = 23.5 ± 0.3 kcal mol −1) and 530 ± 5 K ( E ads = 33.6 ± 0.3 kcal mol −1). At higher exposures, a multilayer physisorption peak was also observed at ≈260 K ( E ads = 10.4 ± 0.3 kcal mol −1). Pyridine decomposition on Mo(1 1 0) results in surface carbon and nitrogen accumulation, and gaseous dihydrogen. The energetics of various pyridine adsorption modes were calculated with DFT in order to identify the bonding modes resulting in molecular desorption and surface decomposition. The DFT calculations suggest that pyridine initially adsorbs as η 6-Py-0° coordination followed by η 1(N)-Py-90° adsorption on clean Mo(1 1 0), and surface heating is suggested to result in the transformation of a portion of η 6-Py-0° pyridine to surface α-pyridyl species (μ 2,η 2(N,C2)-Pyridyl, η 2(N,C2)-Pyridyl) that further decompose to surface carbon and nitrogen and desorbing dihydrogen on clean Mo(1 1 0).

The chemisorption and decomposition of pyridine and ammonia at clean and oxidised Al(1 1 1) surfaces

The nature of the oxygen state at Al(1 1 1) surfaces has been probed by the adsorption of ammonia and pyridine using photoelectron spectroscopy to study reaction products as the sample was warmed from 130 to 540 K. Ammonia only physisorbs at the clean Al(1 1 1) surface but the presence of surface oxygen catalyses a decomposition reaction which leads to the formation of an amide and, on warming to 295 K and above, a nitride. There is no evidence in the XP spectra for the presence of an hydroxyl species or for the desorption of water. Higher oxygen concentrations result in a decrease in the extent of decomposition, with ammonia being stable to 295 K on the pre-oxidised surface. Pyridine partially decomposes at the clean Al(1 1 1) surface at 130 K, giving rise to a well defined intermediate tentatively assigned to an α-pyridyl on the basis of the C:N ratio. Further decomposition occurs on warming with the formation of carbide and nitride by 540 K. Pre-adsorbed oxygen reduces the extent of pyridine decomposition at low temperatures but the species assigned as an α-pyridyl is still formed by room temperature.

Selective Oxidative Decomposition of Pyridine on a Copper-Containing Zeolite in the Gas Phase

Copper-containing zeolites of mordenite, pentasil, and faujasite types selectively catalyze the oxidation of pyridine in the gas phase to CO2, H2O, and N2. The cation-decationated CuHY samples, prepared by solid state ion exchange, were optimal (most active and selective) among the catalysts tested with respect to formation of the products named under adsorption-catalytic conditions of gas purification.

Characteristics of Fe2+/H2O2/UV Oxidization Process

The characteristics of a Fe2+/H2O2/UV system, which was constructed by introducing UV irradiation (wave length 253.7 nm) into a Fenton oxidization system, were evaluated on decomposition of pyridine and other organics. The effect of oxygen on organic decomposition was also examined by feeding air into the reactor. The optimum Fe2+ concentrations for pyridine and acetic acid were found to be 45.6 and 9.1 mg l−1, respectively, under the conditions of 250 mgTOC l−1, 2450 mgH2O2 l−1, and 35°C. On the other hand, there existed no optimum H2O2 concentration for pyridine decomposition in the range of 550 mg l−1 to 2450 mg l−1. Aeration was found to be an effective method to increase the TOC removal efficiency. The reaction rate was increased by increasing the reaction temperature. Of the 15 compounds investigated in this study, organics with high electron density, such as aromatic and heterocyclic compounds were relatively easy to decompose, compared with the aliphatic compounds such as alcohols, ketones, and organic acids. The relatively low decomposition rates of alcohols and ketones were originated from the formation of acetic acid. Nitromethane was difficult to be completely decomposed by the Fe2+/H2O2/UV system.

Characteristics of Fe2+/H2O2/UV Oxidization Process

The characteristics of a Fe2+/H2O2/UV system, which was constructed by introducing UV irradiation (wave length 253.7 nm) into a Fenton oxidization system, were evaluated on decomposition of pyridine and other organics. The effect of oxygen on organic decomposition was also examined by feeding air into the reactor. The optimum Fe2+ concentrations for pyridine and acetic acid were found to be 45.6 and 9.1 mg l−1, respectively, under the conditions of 250 mgTOC l−1, 2450 mgH2O2 l−1, and 35°C. On the other hand, there existed no optimum H2O2 concentration for pyridine decomposition in the range of 550 mg l−1 to 2450 mg l−1. Aeration was found to be an effective method to increase the TOC removal efficiency. The reaction rate was increased by increasing the reaction temperature. Of the 15 compounds investigated in this study, organics with high electron density, such as aromatic and heterocyclic compounds were relatively easy to decompose, compared with the aliphatic compounds such as alcohols, ketones, and organic acids. The relatively low decomposition rates of alcohols and ketones were originated from the formation of acetic acid. Nitromethane was difficult to be completely decomposed by the Fe2+/H2O2/UV system.

Laser induced chemical vapour deposition of polypyridine films

Continuous-wave CO2 laser photosensitized (SF6) decomposition of pyridine is dominated by dehydrogenative coupling of the heterocyclic rings, and it represents a convenient process for chemical vapour deposition of thin polypyridine films.