Hydrogenation through Partial Oxidation of Hydrocarbons in Supercritical Water

Adschiri, Tadafumi; Okazaki, Susumu; Mochiduki, Makoto; Kurosawa, Shutaro; Arai, Kunio

doi:10.5188/ijsmer.7.273

Cited by 14 publications

(11 citation statements)

References 11 publications

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“…Tetralin (NP) and Decalin (DL) were the main products. As in the DBT experiments, the rate of naphthalene hydrogenation in CO−SCW and in CO 2 −H 2 −SCW was higher than that in H 2 −SCW. , Similar results were obtained for the denitrogenation of carbazole, namely, a faster reaction in CO−SCW and CO 2 −H 2 −SCW than in H 2 −SCW at a lower water density, as shown in Figure . However, for this system, the suppression of the hydrogenation rate with increasing water density was observed, which suggests the need for a new catalyst suitable for the dense SCW hydrogenation.…”

Section: Resultssupporting

confidence: 78%

Hydrogenation of Hydrocarbons through Partial Oxidation in Supercritical Water

Arai

Adschiri

Watanabe

2000

Ind. Eng. Chem. Res.

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We propose a new process for the hydrotreatment of heavy oils in supercritical water (SCW). The discussion in this paper is composed of three parts: (1) hydrogenation through water-gas shift reaction in supercritical water, (2) selective formation of carbon monoxide by partial oxidation in supercritical water and through combinations of these two, and (3) hydrogenation of hydrocarbons through their partial oxidation in supercritical water. In the experiments involving hydrogenation of dibenzothiophene, carbazole, and naphthalene, faster hydrogenation rates could be obtained in a CO−SCW atmosphere than in a H2−SCW atmosphere. Even in the case of a H2−CO2−SCW atmosphere, similarly faster reaction rates were obtained, which suggests that an intermediate species of the water-gas shift reaction is the actual reason for the high hydrogenation rates. Partial oxidation experiments were conducted for hexylbenzene and n-hexadecane. The selectivity of CO increased with increasing density of water, while CO2 was the main product of the gas-phase reaction. Partial oxidation of dibenzothiophene (with a sulfur-treated NiMO/Al2O3 catalyst) and n-hexadecane (without catalysts) were also examined. Hydrodesulfurization of dibenzothiophene proceeds effectively in water. For n-hexadecane oxidation, the alkane/alkene ratio increased with increasing water density. The observed product distribution is probably due to the production of carbon monoxide, which is followed by the formation of active hydrogenating species via the water-gas shift reaction. This work demonstrates that hydrogenation reactions can be greatly accelerated in supercritical water through the use of either direct introduction of carbon monoxide or in situ formation of carbon monoxide through the partial oxidation of hydrocarbons.

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Section: Resultssupporting

confidence: 78%

Hydrogenation of Hydrocarbons through Partial Oxidation in Supercritical Water

Arai

Adschiri

Watanabe

2000

Ind. Eng. Chem. Res.

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“…Likely the reason for the rather high CO 2 and the low H 2 yields in our experiments is that the gasification is not complete after 15 min, which means that the hydrogen missing in the gas phase may be bonded in the organic compounds of the liquid phase. Other studies show that H 2 formed via the water gas shift reaction can further react with organic compounds to form hydrogenated products .…”

Section: Discussionmentioning

confidence: 99%

Biomass Conversion in Water at 330−410 °C and 30−50 MPa. Identification of Key Compounds for Indicating Different Chemical Reaction Pathways

Kruse¹,

Gawlik²

2002

Ind. Eng. Chem. Res.

451

314

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The degradation of biomass is studied in the ranges of 330-410 °C and 30-50 MPa and at 15 min of reaction time. To characterize the chemistry of biomass degradation, key compounds which are intermediates of the biomass degradation are identified and quantified. These key compounds are used to compare the results from earlier studies of model compounds such as, e.g., glucose or cellulose, with biomass degradation in order to identify chemical reaction pathways. Key compounds identified are phenols (phenol and cresols), furfurals, acids (acetic acid, formic acid, lactic acids, and levulinic acid), and aldehydes (acetic aldehyde and formic aldehyde). In addition, sum parameters such as the total organic carbon content and the composition of the formed gas phase are used to describe the biomass degradation. The results are compared with the hydrothermal upgrading process and with the well-known gas-phase gasification processes. The influence of the change of water properties from subcritical to supercritical conditions on the biomass degradation is also discussed. These comparisons show that most of the main reaction pathways detected by the key compounds can be understood by the studies of model compounds. On the other hand, biomass is much more complex because biomass contains a lot of different substances. Especially, the influence of salts is significant and, in addition, rather complex.

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“…The reaction is catalyzed by metal, metal oxide or homogeneous catalyst and can be driven by removing one of the products. Studies by Arai et al [46,47] have demonstrated that hydrogenation reactions can be greatly accelerated in supercritical water (SCW) through the use of either direct introduction of carbon monoxide or in situ formation of CO through the partial oxidation of hydrocarbons. Experiments were conducted with NiMo/Al 2 O 3 at 673 K and 30-32 MPa, in various atmospheres (H 2 -SCW, CO-SCW, CO 2 -H 2 -SCW).…”

Section: Introductionmentioning

confidence: 99%