Formation Of Nitrogen-containing Compounds Research Articles

Formation of nitrogen-containing compounds during microwave pyrolysis of microalgae: Product distribution and reaction pathways

The formation of nitrogen-containing compounds in bio-oil during microwave pyrolysis of Chlorella and Spirulina microalgae has been investigated in this study. Activated carbon (AC) and magnetite (Fe3O4) were used as microwave receptors during microwave pyrolysis experiments. It has been found that the use of Fe3O4 increased the total yield of bio-oil. The use of different microwave receptors did not seem to have affected the total yield of nitrogen-containing compounds in the bio-oil. However, Fe3O4 promoted the formation of nitrogen-containing aliphatics, thereby reducing the formation of nitrogen-containing aromatics. The use of AC promoted the dehydration reactions during amino acid decomposition, thereby enhancing the formation of nitrogen-containing aromatics during pyrolysis. From the gas chromatography–mass spectrometry (GC–MS) analysis results, the major high-value nitrogen-containing compounds in the pyrolysis bio-oil of Chlorella and Spirulina were identified as indole and dodecamide. The formation mechanisms of nitrogen-containing compounds were proposed and discussed.

Aqueous Processing of Atmospheric Organic Particles in Cloud Water Collected via Aircraft Sampling.

Cloudwater and below-cloud atmospheric particle samples were collected onboard a research aircraft during the Southern Oxidant and Aerosol Study (SOAS) over a forested region of Alabama in June 2013. The organic molecular composition of the samples was studied to gain insights into the aqueous-phase processing of organic compounds within cloud droplets. High resolution mass spectrometry (HRMS) with nanospray desorption electrospray ionization (nano-DESI) and direct infusion electrospray ionization (ESI) were utilized to compare the organic composition of the particle and cloudwater samples, respectively. Isoprene and monoterpene-derived organosulfates and oligomers were identified in both the particles and cloudwater, showing the significant influence of biogenic volatile organic compound oxidation above the forested region. While the average O:C ratios of the organic compounds were similar between the atmospheric particle and cloudwater samples, the chemical composition of these samples was quite different. Specifically, hydrolysis of organosulfates and formation of nitrogen-containing compounds were observed for the cloudwater when compared to the atmospheric particle samples, demonstrating that cloud processing changes the composition of organic aerosol.

SIMS study of plumes generated from laser ablation of polymers

Plumes generated by ablation of polymer targets using a third-harmonic Nd:YAG laser under different atmospheres (air, N2 and He) were deposited on a H-terminated silicon substrate. The chemical composition and distribution of deposited ablation debris were measured using time-of-flight secondary-ion mass spectrometry. Mass-resolved images show that the size and shape of the plume is dependent on the laser pulse energy and atmosphere in which the plume expanded. In air and nitrogen, plumes are hemispherical with distinct borders. In He they are mushroom-shaped without sharp borders. Since all experiments were carried out at atmospheric pressure, these differences can be related to the reactivity and molecular weight of the gas. Nitrogen-containing compounds (NCCs) and oxygen-containing compounds (OCCs) were found in plumes ablated in air but not in N2 and He environments. We suggest that the formation of NCCs and OCCs is due to the interaction of the hot plume with air, initiating thermal dissociation of O2 and oxygen-assisted dissociation of N2.

Fine ParticulateN–Nitroso and Nitrite Organic Compounds in the Atmosphere

Abstract Photochemistry between gas phase organic compounds, oxides of nitrogen, and ozone is expected to result in the formation of nitrogen-containing compounds of potential toxicological importance. Classes of compounds which may form include nitro-, N-nitroso-, nitrate-, and nitrite-substituted organic compounds. Many of these compounds are labile, semivolatile organic compounds in equilibrium between the gas and particulate phases in the atmosphere. The phase distribution of these potentially toxic semivolatile organic compounds can be determined using diffusion denuder sampling technology. The total concentration of N-nitroso compounds in a collected sample is determined using N-nitroso-specific denitrosation reactions followed by detection of the produced nitric oxide with a chemiluminescence detector. Denitrosation chemistry can also be used to determine nitrite compounds. Differentiation between total N-nitroso- and nitrite-containing compounds is accomplished using sulfamic acid as a nitrite-spe...

Formation of Nitrogen-Containing Compounds during Slow Pyrolysis and Oxidation of Petroleum Coke

The petroleum coke from a fluid coking process was pyrolyzed in helium and oxidized in 1% and 4% O2 and in air, with the aim to determine N-containing compounds such as HCN, NH3, NO, and N2O. The experiments were performed with and without limestone. NO was the major product during all oxidation runs. N2O was formed only in air. In this case, N2O formation was delayed when compared with that of NO. The addition of limestone decreased formation of HCN and increased that of NH3, whereas NO formation was least affected.

Structural Investigations of N-modified Lignins by 15N-NMR Spectroscopy and Possible Pathways for Formation of Nitrogen Containing Compounds Related to Lignin

Investigations were carried out on the characterization of nitrogen containing substructures in N-modified lignins and on the possible pathways for their formation by combination of several analytical methods. These methods include NMR spectroscopy, in particular 15 N-NMR, IR spectroscopy, and GCMS analysis. Among the substructures identified, aromatic nitriles and urea were shown to be constituents of N-modified lignins and N-modified lignin model compounds. A number of low molecular weight fragments with ring bonded nitrogen were identified as well as certain amides. N-heterocyclic products were not found. Possible pathways for the formation of these structures are discussed in view of the reaction conditions employed and the electronic structure of the reactants. The 15 N-NMR technique was shown to be very effective in structural elucidation of N-modified lignins and related model compounds. However, the compounds concerned must be present in sufficiently high concentrations.

Gas chromatographic and capillary gas chromatographic-mass spectrometric analysis of thermal decomposition products of liquid crystal polymers

The thermal decomposition products of a series of liquid crystalline poly(azomethine ester)s and their model compounds of low molecular mass were investigated. The volatile gaseous products evolved in Curie-point pyrolysis at 500° C were analysed using a Porapak S column and a thermal conductivity detector of high sensitivity. The less volatile aliphatic and aromatic products evolved in flash pyrolysis at 500° C were analysed by gas chromatography-mass spectrometry. The decomposition of the ester group resulted in carbon monoxide and carbon dioxide. The polymers containing methoxy substituent groups gave higher amounts of carbon monoxide and methane, indicating cleavage of the methoxy group. The phenyl undecanoate moiety of the polymers resulted in phenol and p-cresol. In contrast, the phenyl hexanoate sequence of the model compounds appeared in the pyrolysate as p-hexenylphenol and p-hexenylphenyl hexanoate, which were attributed to intra/intermolecular reactions of the pentyl radicals formed through decarbonylation of the hexanoate ester. In general, the formation of nitrogen-containing compounds was found to be negligible. The infrared spectroscopic analysis of the residue left after pyrolysis at 400 and 500° C indicated that the azomethine moiety had altered but the nitrogen remained mostly in the char.