Aspects of kerogen oxidative dissolution in subcritical water using oxygen from air

Abstract

Society's growing demands on everyday products and materials are increasingly difficult to meet in an environment that seeks to avoid petroleumbased processes. Instead of abandoning fossil materials altogether, more research should be done on their efficient and clean conversion. One option for this is the oxidative dissolution of kerogen in water under conditions that satisfy the subcritical range (T = 150-200 °C, pO 2 = 0.5-4 MPa). The resulting mixture contains a substantial amount of various aliphatic carboxylic and dicarboxylic acids. Both batch and semi-continuous processes were set up to find the main factors and optimal conditions for the kerogen dissolution process. The rate of transformation of organic carbon to dissolved organic compounds was mainly influenced by elevated temperature and oxygen partial pressure. To obtain high yields of organic carbon dissolution and to avoid the formation of excess CO 2 , the oxidation of kerogen should be carried out fast (< 1 h) and under high oxygen pressure. By employing a temperature of 175 °C and O 2 pressure of 2 MPa, over 65% of the initial organic carbon dissolves in about one hour. Prolonged reaction times or harsher oxidation conditions resulted in a rapid degradation of dissolved matter and also of the valuable products formed. The organic matter content of the initial oil shale had a direct effect on the further degradation of dicarboxylic acid and consequently on the overall yield. The suitability of using a trickle-bed reactor for kerogen dissolution is discussed in detail on the basis of experimental results.

A two-step model for assessing the potential of shale-derived chemicals by oxidation of kukersite

“…The idea is based on the knowledge that the organic structure of kukersite kerogen contains compounds with widely varying oxidation potentials. The authors of this paper have shown repeatedly that methylresorcinols are far more sensitive towards air oxidation than the rest of the kerogen or formed dicarboxylic acids due to the increased electron density on the aromatic ring [20,23]. If oxidized as single compounds, methylresorcinols are decomposed into CO 2 within 1 hour at 175 °C with pO 2 20 bar, together with the formation of acetic acid, formic acid and butanoic acid [24].…”

“…Calculations were made using experimental data from previous publications [19,20]. In these experiments, oil shale with the organic content enriched to 70% was used (hereafter referred to as K-70).…”

“…In order to develop technologies which would directly produce valuable dicarboxylic acids from oil shale, both nitric acid [13][14][15][16] and molecular oxygen in a non-catalytic process [17,18] have been used. In the previous studies by Kaldas et al [19,20], the results of wet air oxidation (WAO) applied to oil shale concentrates at temperatures up to 200 °C were presented. The aim was to explore the potential for obtaining various feedstock chemicals through this advanced oxidation process.…”

“…It should also be noted that resorcinols can act as co-oxidants if placed in the same solution with oil shale or carboxylic acids, i.e. they can promote the oxidative decomposition of other inherent substances and thereby increase the amount of CO 2 emitted [20,23].…”

Release performance and kinetic behavior of volatile products from controlled pressure pyrolysis of oil shale in nitrogen atmosphere

“…This is consistent with the demonstration by Liu et al 24 and Wu et al 25 through experiments. In addition, under the conditions of subcritical water 26 , 27 , water vapor 13 , 28 and nitrogen 29 , 30 , the evolution of pore structure of oil shale has been studied, but under the conditions of high pressure, the influence mechanism of pore structure evolution on the coking and product release behavior of shale oil is less studied. To sum up, the effects of environmental atmosphere, temperature and pressure on oil shale pyrolysis have been extensively studied.…”