Study on the Deuteration of Pyridine Extract from Yubari Coal with D3PO4-BF3 Complex

Abstract

The present work on the deuteration of coal extracts was attempted to gain more information of coal structure, since the informations from previously reported papers were mainly concerned with the structural conception and no mention of its reactivity derivable from its structure has been made.In this study, deuterophosphoric acid-boron trifluoride complex was used as a deuteration reagent. First, the deuteration of some authentic hydrocarbons was made in ordr to determine the reactivity based on the structure of these hydrocarbons. It was found that the deuteration of aromatic hydrocarbons occured readily at 65°C in two hours, and aromatic hydrogens were deuterated up to 80% or more. The deuteration in the alkyl parts of the alkyl aryl hydrocarbons was observed only in the case of cumene and tetralin, and almost all aliphatic hydrocarbons were not substituted under the above conditions.These results may be useful for the analyses of the aromatic structure and reactivity of coal. Thus in the present work, a pyridine extract of Yubari coal was used for the application of deuteration. The content of deuterium was also calculated by means of a measurement of density of heavy water formed by combustion. In infra-red spectroscopy, especially absorption in the region of C.H stretching (near 2920cm-1) and out-of-plane deformation (920 -680cm-1) were so remarkable that their specific absorbance (the integral intensity in the case of out-of-plane deformation) could be utilized as a parameter of the deuteration on aromatic and aliphatic hydrogens.In the case of pyridine extract, the reaction also proceeded rapidly, and 15 minutes from the onset of the reaction was sufficient to change 63% of the total exchangeable hydrogen. It was summarized that there was a limit of reaction under such a condition (17 hours at 65°C) and the total exchangeable hydrogen of the raw material was 27.3%. It was found that the aromatic substitution was faster than aliphatic substitution.