Production of Benzene Carboxylic Acids and Small-Molecule Fatty Acids from Lignite by Two-Stage Alkali-Oxygen Oxidation

Abstract

Carboxylic acids are widely used in industry as a kind of important chemical materials, and it is very promising to produce carboxylic acids from lignite. The traditional alkalioxygen oxidation of lignite does not consider the complex structure of lignite, and the structures with different reactivities are treated under identical and harsh reaction conditions, resulting in a low yield of carboxylic acids. We propose a twostage oxidation process of lignite to increase the yield and mitigate the harsh reaction conditions. First, lignite was extracted using a NaOH aqueous solution to yield two parts (extract and residue) with different reactivities. The extract and residue then were oxidized separately with alkali-oxygen oxidation under different conditions. In this way, high yields of benzene carboxylic acids (BCAs, 12 types) and small-molecule fatty acids (SMFAs) could be obtained. The extraction conditions and the alkali-oxygen oxidation conditions of the extract and the residue were investigated. Compared with the oxidation of extract, the oxidation of residue requires higher reaction temperature, higher initial O 2 pressure, higher alkali concentration, and longer reaction time. The structures of the extract and residue were characterized by 13 C nuclear magnetic resonance ( 13 C NMR) and Fourier transform infrared (FT-IR) spectroscopy, which indicates that most of aromatic structures in the extract are single aromatic rings with side chains containing many oxygen-containing functional groups. However, aromatic structures in the residue are mainly condensed aromatic rings with side chains containing many alkyl chains. These differences in their structures result in different yields of carboxylic acids from the extract and residue.

Mechanically Resistant and Sustainable Cellulose-Based Composite Aerogels with Excellent Flame Retardant, Sound-Absorption, and Superantiwetting Ability for Advanced Engineering Materials

“…This indicates that during the thermal decomposition process of the AH NPs@cellulose composite aerogels, the AH NPs were degraded into metallic oxides, which results in the absorption of the decomposition products originating from the cellulose aerogel matrix. The adsorbed compounds were transferred to carbon by catalytic action in the solid phase …”

“…At the same time, the process of decomposition releases plenty of water and will not produce toxic, flammable, or corrosive gas, which has contributed to the reduction of the concentration of oxygen on the surface. After that, the porous metallic oxides, generated during the combustion process, not only retard the heat spread but also suppress the release of fuel from the solid phase to the combustion area . Then, the nanometal particles can form a continuous and dense network-structured protective layer without forming a crack that damages the flame-retardant effect, which can serve as a thermal insulation layer of the original polymer below the layer while isolating oxygen to prevent combustion. − On the basis of these facts, the flame-retardant properties of cellulose composites aerogel are greatly improved.…”

“…The adsorbed compounds were transferred to carbon by catalytic action in the solid phase. 45 Potential Flame-Retardant Mechanism. On the basis of the above analysis, it is interesting to observe that the addition of AH NPs has obviously improved the thermal stability and fire retardancy of cellulose aerogels.…”

“…Meanwhile, it can effectively enhance the thermal stability of char residues via catalytic reactions in the solid phase. [44] The EDS spectra and the results of the char for the AH NPs@cellulose composite aerogels is presented in Figure S2. It can be seen that carbon became the main element in the residues.…”

Trial by Fire: On the Terminology and Methods Used in Pyrogenic Organic Carbon Research

“…These may be derived from lignin or tannin, which include a wide variety of polycondensed aromatics (Hernes and Hedges, 2000;Waggoner et al, 2015). Other non-pyrogenic OM sources of condensed aromatic OM are abundant in the geosphere, including woody peat, coal, kerogen, and oil (Yoshioka and Ishiwatari, 2005;Hammes et al, 2007;Wang et al, 2012;Hartman et al, 2015;Li et al, 2017). Still other studies have found that nonpyrogenic OM can be readily transformed to condensed aromatic OM, which would appear to be pyrogenic, through photolytic, microbial, or chemical degradative processes (Glaser and Knorr, 2008;Chen et al, 2014;Waggoner et al, 2015;DiDonato et al, 2016).…”