Elucidation of Hydrogen Mobility in Functional Groups of Coals Using Tritium Tracer Methods

Abstract

Hydrogen exchange reactions of coal with tritiated water and gaseous hydrogen were investigated to estimate the mobility of hydrogen in coal using not only a batch type reactor but also a flow type reactor. Specifically, the reactivities of functional groups were traced in these reactions. In the reaction of coal with tritiated water at 100°C the hydrogen exchange of functional groups such as hydroxyl group in coals could be estimated. In the pressurized system using stainless batch type reactor aromatic hydrogen at ortho-and para-positions of a functional group could also be estimated by the hydrogen exchange reactions of coal and tritiated water at higher temperature. In hydrogen exchange reactions of coals with tritiated gaseous hydrogen using a flow reactor, reaction temperature was controlled exactly. The use of a Pt/Al 2 O 3 catalyst promoted the generation of hydrogen radicals which reacted with coal. This method enables us to estimate the reactivity of a functional group with a hydrogen radical. Further, it was found that the particle size of coal only slightly affected hydrogen exchange ratio of coal in both cases of tritiated gaseous hydrogen and tritiated water.

Effect of hydrothermal treatment on the carbon structure of Inner Mongolia lignite

“…This indicates that the hydrogen bond decreased during the hydrothermal treatment of lignite because of hydrolysis of the oxygen functional group. While water absorbed in KBr may obscure this band, the results agree with Ishihara et al (2002) and Yan et al (2020) and the discussion above.…”

“…The CH 2 /CH 3 ratio clearly increases in the second stage because hydrolysis of the oxygen functional groups (such as carboxyl, esters, and ethers) plays an important role in this stage. The hydrogen of the functional groups in lignite can exchange with water via electrophilic substitution on addition of water at this temperature (Ishihara et al 1993(Ishihara et al , 2002, and then transfer in lignite or the methyl hydroaromatic structures opposite to the branched aliphatic structures. The H radicals produced by the condensation of free phenol also participate in the hydrogen transfer.…”

Upgrading of low rank coal by hydrothermal treatment: Coal tar yield during pyrolysis

“…[31,32]. The recovery of hydrothermal treatment coal is about 90%, while the ash contents in the treated coal are almost the same with those in the raw coal.…”

Role of FeS Catalyst in the Hydromodification of Lignite in a Subcritical Water–CO System

“…17,18 However, several researchers reported that catalysts directly promote the transfer of hydrogen from molecular hydrogen to coal rather than through tetralin. 19,20 Li et al 21 revealed that iron-based catalysts mainly promoted coal pyrolysis and the formation of activated hydrogen to accelerate the secondary distribution of H in the reaction. Niu et al 22 reported that iron-based catalysts can directly promote the hydrogen transfer and exchange between coal and the solvent, whereas the α-radical of tetralin acts as an important intermediate.…”

“…In fact, numerous studies have focused on studying the role of iron-based catalysts in the hydrogenation of coal. − For the hydropyrolysis of coal, researchers found that the catalytic activity of iron on cracking was higher than that on hydrogenation, which changes the composition of tar and makes it lighter . In the coal liquefaction process, the conventional theory suggested that iron-based catalysts can split molecular hydrogen into tetralin and then catalyze the fast dehydrogenation of tetralin to release hydrogen for coal hydrogenation. , However, several researchers reported that catalysts directly promote the transfer of hydrogen from molecular hydrogen to coal rather than through tetralin. , Li et al revealed that iron-based catalysts mainly promoted coal pyrolysis and the formation of activated hydrogen to accelerate the secondary distribution of H in the reaction. Niu et al reported that iron-based catalysts can directly promote the hydrogen transfer and exchange between coal and the solvent, whereas the α-radical of tetralin acts as an important intermediate.…”