Pathway of TCNE Interaction with Coal To Enhance Its Solubility in the NMP−CS₂ Mixed Solvent

Abstract

Tetracyanoethylene (TCNE) is a very effective additive enhancing coal solubility in the N-methyl-2-pyrrolidinone (NMP)-CS 2 (1:1, v/v) mixed solvents. It was found that TCNE generates 1,1,2,3,3-pentacyanopropene (PCNP) anion in NMP in the presence of water. The PCNP anion is not an electron acceptor but is as effective as TCNE at enhancing solubility. This rules out chargetransfer complexation between coal and TCNE as a main factor in increasing coal solubility. In addition, we have not found a correlation between the electron acceptor ability of additives and their ability to enhance coal solubility. These results do not support the proposal that formation of a charge-transfer complex between electron acceptors and coal is responsible for the enhancement of coal solubility.

Effect of Addition of Various Salts on Coal Extraction with Carbon Disulfide/N-Methyl-2-pyrrolidinone Mixed Solvent

“…This is the one of the reasons why these polarizable anions that are categorized into soft base have less effect on the extraction yields than nonpolarizable anions (hard base). (6) The extraction yields of acid-treated and subsequently methylated SG without TBAF are smaller than that of original SG with TBAF. This suggests that TBAF suppress not only the acid-base interactions between coal molecules in which cations and protons participate, but also other presently undefined acid-base interactions occurring in the original SG.…”

“…However, the correlation between the solubility of coal and the electron acceptability of the additives was not successful. 6 Furthermore EPR studies of Illinois No. 6 coal demonstrate that the increase in the spin concentration by the addition of electron acceptors is not due to the formations of new paramagnetic centers, i.e., thermally accessible triplet state arising from charge-transfer interactions.…”

Hydroxide-Initiated Conversion of Aromatic Nitriles to Imidazolines: Fullerenes vs TCNE

“…The in situ UVÀvis spectra of the reaction mixture display absorption bands at 400 and 419 nm, which have been assigned to originate from the 1,1,2,3,3-pentacyanopropenyl anion (PCNP À ) 20 likely formed via an oligomerization initiated by nucleophilic attack of RTCNE À to neutral TCNE. 19c Additional absorption bands are shown between 510 and 564 nm for the reaction mixture with a 1:20 molar ratio of OH À to TCNE, which likely arise from the anionic species from further oligomerization due to a higher TCNE concentration.…”

Interactions of Illinois No. 6 Bituminous Coal with Solvents: A Review of Solvent Swelling and Extraction Literature

“…33,46,48,50,[73][74][75][76][77] This seems unlikely, for various reasons, 84,85 but perhaps the 16 arguments also involve semantics. Anthracite coals, for example, are insoluble because of their more graphitic-like structure.…”

“…46,48,50,[73][74][75][76][77] They found that NMP/CS 2 mixed solvents can significantly increase the swelling of coals and the extraction yields of soluble material. However, much of this work is based on results obtained from a single coal, Upper Freeport, about 59% of which is soluble in NMP/CS 2 mixtures compared to only 35% in pyridine.…”