Photochemical weathering study of Brazilian petroleum by EPR spectroscopy

Guedes, Carmen Luı́sa Barbosa; Mauro, Eduardo Di; Antunes, Valdemir; Mangrich, Antônio S.

doi:10.1016/s0304-4203(03)00114-2

Cited by 39 publications

(26 citation statements)

References 19 publications

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“…The oxygen-centered phenoxy radical, thought to be a major radical species in lignin pyrolysis, typically has higher g values ranging from 2.0040 to 2.0053. [15,21] However, these g values are sensitive to interactions between products and neighboring atomic structures. [15] The broad and unstructured peak on EPR spectra suggests contributions from several radical species that have slightly different g values.…”

Section: Resultsmentioning

confidence: 99%

“…[15,21] However, these g values are sensitive to interactions between products and neighboring atomic structures. [15] The broad and unstructured peak on EPR spectra suggests contributions from several radical species that have slightly different g values. Previously, we found that the free radicals produced from the pyrolysis of benzyl phenyl ether (BPE), a simple dimeric molecule serving as a model compound to study pyrolysis of aryl ether linkages, have a g value of 2.0035.…”

Section: Resultsmentioning

confidence: 99%

“…[16] The single broad unstructured peak in each EPR spectrum had g values in the range of 2.0028-2.0031, which corresponded to organic free radicals. [18] In comparison, the g values for the free radicals of asphaltenes reported in the literature ranged from 2.0028 to 2.0034, [15] whereas free radicals observed from coal pyrolysis ranged from 2.0026 to 2.0035. [19] Benzyl radicals are carboncentered free radicals that can be expected on the basis of the lignin structure.…”

Section: Quantitative Analysis Of Free Radicals In Pyrolysis Productsmentioning

confidence: 99%

“…[13] It also has been used to study free radicals in airborne particulate matter [14] and petroleum. [15] Corn stover (selected as representative of lignocellulosic biomass), corn-stover-derived organosolv lignin, and cellulose were separately pyrolyzed and the resultant bio-oils were analyzed for free radicals. Also, pyrolytic lignin (PL) was extracted from corn-stover bio-oil and analyzed for free radicals.…”

Section: Introductionmentioning

confidence: 99%

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Quantitative Investigation of Free Radicals in Bio‐Oil and their Potential Role in Condensed‐Phase Polymerization

et al. 2015

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We report on the quantitative analysis of free radicals in bio-oils produced from pyrolysis of cellulose, organosolv lignin, and corn stover by EPR spectroscopy. Also, we investigated their potential role in condensed-phase polymerization. Bio-oils produced from lignin and cellulose show clear evidence of homolytic cleavage reactions during pyrolysis that produce free radicals. The concentration of free radicals in lignin bio-oil was 7.5×10(20) spin g(-1), which was 375 and 138 times higher than free-radical concentrations in bio-oil from cellulose and corn stover. Pyrolytic lignin had the highest concentration in free radicals, which could be a combination of carbon-centered (benzyl radicals) and oxygen-centered (phenoxy radicals) organic species because they are delocalized in a π system. Free-radical concentrations did not change during accelerated aging tests despite increases in molecular weight of bio-oils, suggesting that free radicals in condensed bio-oils are stable.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Quantitative Analysis Of Free Radicals In Pyrolysis Productsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Quantitative Investigation of Free Radicals in Bio‐Oil and their Potential Role in Condensed‐Phase Polymerization

et al. 2015

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“…Espinosa et al (2001) have employed EPR in the analysis of V(IV) porphyrins in petroleum products. Guedes et al (2003) employed EPR in the characterisation of the molecular structure of asphaltenes in Brazilian oil whilst multicomponent systems have been studied in the laboratory by Misel (1969, 1970), Guilbault and Moyer (1970). Mangrich et al (2009) have used EPR to trace the provenances of dusts by studying sunlight bleaching of Ti E1 electron trap centres in quartz which are induced by natural radiation (Gao et al 2009).…”

Section: Introductionmentioning

confidence: 99%

Metal pollutants in Indian continental coastal marine sediment along a 3700 km transect: An electron paramagnetic resonance spectroscopic study

Alagarsamy

Hoon

2018

Science of The Total Environment

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We report the analysis and geographical distribution of anthropogenically impacted marine surficial sediments along a 3700km transect around the continental shelf of India. Sediments have been studied using a mixed analytical approach; high sensitivity electron paramagnetic resonance (EPR), chemical analysis and environmental magnetism. Indian coastal marine deposits are heavily influenced by monsoon rains flushing sediment of geological and anthropogenic origin out of the subcontinental river systems. That is, climatic, hydro-, geo- and anthropogenic spheres couple strongly to determine the nature of Indian coastal sediments. Enrichment of Ni, Cu and Cr is observed in shelf sediments along both east and west coasts associated with industrialised activities in major urban areas. In the Gulf of Cambay and the Krishna and Visakhapatnam deltaic regions, levels of Ni and Cr pollutants (≥80 and ≥120ppm respectively) are observed, sufficient to cause at least medium adverse biological effects in the marine ecosystem. In these areas sediment EPR spectra differ in characteristic from those of less impacted ones. Modelling enables deconvolution of EPR spectra. In conjunction with environmental magnetism techniques, EPR has been used to characterise species composition in coastal depositional environments. Paramagnetic species can be identified and their relative concentrations determined. EPR g-values provide information about the chemical and magnetic environment of metals. We observe g-values of up to 5.5 and large g-shifts indicative of the presences of a number of para and ferrimagnetic impurities in the sediments. EPR has enabled the characterisation of species composition in coastal depositional environments, yielding marine sediment environmental 'fingerprints'. The approach demonstrates the potential of EPR spectroscopy in the mapping and evaluation of the concentration and chemical speciation in paramagnetic metals in sediments from marine shelf environments and their potential for source apportionment and environmental impact assessment.

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