Molecular Distributions of Soluble Oxidation Products from Coals Characterized by Mass Spectrometers.

Xing Fan,Fei Wang

doi:10.1155/2018/5174172

Abstract

Oxidation of three coals with rank from lignite to anthracite in NaOCl aqueous solution was investigated in this study. The oxidation products were characterized by using gas chromatography/mass spectrometry and direct analysis in real-time mass spectrometry. The results showed that most of organic compounds in coals were converted into water-soluble species under mild conditions, even the anthracite. Benzene polycarboxylic acids (BPCAs) and chloro-substituted alkanoic acids (CSAAs) were major products from the reactions. The products from lower rank coals consist of considerable CSAAs and most products from high rank coals are BPCAs. As coal rank increases, the yield of BPCAs with more carboxylic groups increases.

Highlights

Coal consists of three-dimensional crosslinking networks, commonly called coal macromolecules, with a wide range of small organic species scattered inside the networks [1, 2]
Mild oxidation was proven as an effective method to study coal structures and acquire chemicals like aliphatic acids (AAs), benzenepolycarboxylic acids (BPCAs), and other oxygen-containing species from coals [14]
The filtrate 1 (F1) was acidified with aqueous HCl to pH 2-3 and filtrated to obtain filter cake 2 (FC2) and filtrate 2 (F2)

Summary

Introduction

Coal consists of three-dimensional crosslinking networks, commonly called coal macromolecules, with a wide range of small organic species scattered inside the networks [1, 2]. Oshika and Okuwaki [13] examined the O2 oxidation of coal-tar pitch in alkaline solution and found that plenty of benzene polycarboxylic acids were produced These attempts were not successful enough because most of the reactions were performed under severe conditions such as high temperature, high pressure, and strong acids, or only available for low rank coals. Gas chromatography/mass spectrometry (GC/MS) is a powerful analytical method obtaining the molecular-level information of complex mixture such as biomass and coal derivatives and plays a crucial role in understanding composition and structure of coal [16, 17]. Soluble oxidation products were analyzed using GC/MS for understanding the structure difference among various ranks and finding a potential way to obtain organic acids from coals. DART-MS was applied to obtain an overall molecular information for the oxidation products

Experimental

Results and Discussion

Conclusions