Analysis of atomic scale chemical environments of boron in coal by 11B solid state NMR

Takafumi Takahashi, Shunsuke Kashiwakura, Koji Kanehashi, Shunichi Hayashi, Tetsuya Nagasaka

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

Atomic scale chemical environments of boron in coal has been studied by solid state NMR spectroscopy including magic angle spinning (MAS), satellite transition magic angle spinning (STMAS), and cross-polarization magic angle spinning (CPMAS). The 11B NMR spectra can be briefly classified according to the degree of coalification. On the 11B NMR spectra of lignite, bituminous, and sub-bituminous coals (carbon content of 70-90mass%), three sites assigned to four-coordinate boron [4]B with small quadrupolar coupling constants (≥0.9 MHz) are observed. Two of the [4]B sites in downfield are considered organoboron complexes with aromatic ligands, while the other in the most upper field is considered inorganic tetragonal boron (BO4). By contrast, on the 11B NMR spectra of blindcoal (carbon content > 90 mass%), the [4]B which substitutes tetrahedral silicon of Illite is observed as a representative species. It has been considered that the organoboron is decomposed and released from the parent phase with the advance of coal maturation, and then the released boron reacts with the inorganic phase to substitute an element of inorganic minerals. Otherwise boron contained originally in inorganic minerals might remain preservedevenunder the high temperature condition that is generated during coalification.

Original languageEnglish
Pages (from-to)890-895
Number of pages6
JournalEnvironmental Science and Technology
Volume45
Issue number3
DOIs
Publication statusPublished - 2011 Feb 1

ASJC Scopus subject areas

  • Chemistry(all)
  • Environmental Chemistry

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