Chemical Processing in High-Pressure Aqueous Environments. 4. Continuous-Flow Reactor Process Development Experiments for Organics Destruction

Elliott, Douglas C.; Phelps, M.R.; Sealock, L.J.; Baker, E.G.

doi:10.1021/ie00027a013

Cited by 126 publications

(86 citation statements)

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“…The technology can, however also be used for 3 the conversion of dry organic wastes and materials, where the addition of water is justified since supercritical water serves as both reaction medium and reactant. It has been shown that the mechanism for hydrogen formation during SCWG is mainly through the formation of CO, followed by the water-gas shift reaction (WGSR) of the CO [7][8][9]. In addition, methane formation in SCWG would usually involve demethylation but methanation of CO or CO2 using the in situ produced hydrogen from the WGSR has been reported as equally important.…”

mentioning

confidence: 99%

Supercritical water gasification of RDF and its components over RuO2/γ-Al2O3 catalyst: New insights into RuO2 catalytic reaction mechanisms

Onwudili

2016

Fuel

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Five samples, including a composite refuse derived fuel (RDF) and four combustible components of municipal solid wastes (MSW) have been reacted under supercritical water conditions in a batch reactor. The reactions have been carried out at 450 °C for 60 min reaction time, with or without 20 wt% RuO2/gamma-alumina catalyst. The reactivities of the samples depended on their compositions; with the plastic-rich samples, RDF and mixed waste plastics (MWP), giving similar product yields and compositions, while the biogenic samples including mixed waste wood (MWW) and textile waste (TXT) also gave similar reaction products. The use of the heterogeneous ruthenium-based catalyst gave carbon gasification efficiencies (CGE) of up to 99 wt%, which was up by at least 83% compared to the non-catalytic tests. In the presence of RuO2 catalyst, methane, hydrogen and carbon dioxide became the dominant gas products for all five samples. The higher heating values (HHV) of the gas products increased at least two-fold in the presence of the catalyst compared to non-catalytic tests. Results show that the ruthenium-based catalyst was active in feedstock steam reforming, methanation and possible direct hydrogenolysis of C-C bonds. This work provides new insights into the catalytic mechanisms of RuO2 during SCWG of carbonaceous materials, along with the possibility of producing high yields of methane from MSW fractions.Keywords: MSW, supercritical water gasification, ruthenium catalysis, mechanisms, methane * Corresponding Author. Tel.: +44 121 204 4703 Email address: j.onwudili@aston.ac.uk 2 IntroductionRapid urbanization and technological developments are largely responsible for the increasing generation of millions of tonnes of municipal solid wastes (MSW) in major cities around the world. MSW can be broadly classified into organic and inorganic fractions. Among the organic components of MSW, further classifications can be made into biodegradable and nonbiodegradable fractions. By far, food and garden wastes occupy a huge proportion of MSW but these are biodegradable and are often treated by anaerobic digestion (AD) to produce biogas, leading to complete mineralization. After the separation of recyclables, the mixture of nonreadily biodegradable organic components make up a combustible fraction of MSW, which can be made into solid recovered fuels (SRF) and refuse derived fuels (RDF), depending on the specification. The stringent regulations concerning the production and utilization of SRF and RDF indicate that many components of MSW cannot be directly burned as fuels [1][2]. Massproduced synthetic polymers such as plastics and textile materials fall into the category of combustible MSW fractions [3]. Other organic components of MSW that do not hold huge attractions for AD operators include waste wood and reinforced cardboards.Advanced thermochemical technologies suitable for treating plastics and other combustible organic wastes and materials include incineration, pyrolysis and gasification. These technologies convert organic ...

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confidence: 99%

Supercritical water gasification of RDF and its components over RuO2/γ-Al2O3 catalyst: New insights into RuO2 catalytic reaction mechanisms

Onwudili

2016

Fuel

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“…Above T g = 275°C the carbon conversion reached almost unity under a certain LHSV value. Even 150 h -1 of the LHSV value was small enough for the complete conversion at T g = 350°C, indicating that this catalyst is highly reactive as compared with the catalysts presented in the literature (Elliott et al, 1994b).…”

Section: Hydrothermal Gasification Behavior Of the Industrial Wastewatermentioning

confidence: 79%

“…The experimental conditions employed by these researchers were rather severe. Elliott et al (1993Elliott et al ( , 1994aElliott et al ( , 1994bElliott et al ( , 1999 have succeeded in gasifying p-cresol completely at 350°C and 20 MPa using a Ni/Al 2 O 3 catalyst that was selected from many candidates. His group has also proposed a wastewater treatment process using this gasification method.…”

Section: Introductionmentioning

confidence: 99%

Production of Fuel Gas through the Hydrothermal Gasification of Wastewater Using Highly Active Carbon-Base Catalyst

Nakagawa

Namba

Sharma

et al. 2007

J. Chem. Eng. Japan

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Treatments of wastewaters containing various organic compounds in small concentrations are causing serious problems elsewhere in the world, therefore, the development of efficient process for treating wastewaters has been desired. In this study a novel Ni-supported carbon catalyst that we developed was used for gasifying the organic compounds dissolving in an industrial wastewater under hydrothermal conditions. The organic compounds were almost completely gasified above 275°C under the conditions examined. Main gaseous products were CH 4 , H 2 , and CO 2 , having the lower heating value of around 20 MJ/m 3 , indicating that the product gas can be used as fuel gas. The product gas composition was highly dependent on pressure: H 2 and CO 2 were dominant components under 5 MPa, and CH 4 and CO 2 were dominant ones under 20 MPa when the wastewater was gasified at 300°C. Equilibrium calculation for the reactions clarified that these results reflected the state of water, vapor or liquid, in the reactor. A simple calculation for mass and energy balance of the proposed process showed that 46% of the lower heating value of the organic compound (aqueous isopropyl alcohol solution of 3.33 wt% in concentration) can be recovered as fuel gas under the conditions of T g = 350°C, P = 20 MPa even when this process is operated as a stand-alone one. This result shows that the proposed process can be not only a wastewater treatment process but an energy production process if certain conditions were met.

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“…Catalyst employed can include metal [36][37][38][39][40][41][42][43][44][45], alkali [46], and carbonaceous ones [47]. A detail review is available for the catalyst employed for SCW gasification [48].…”

Section: Biomassmentioning

confidence: 99%

Production of Chemicals in Supercritical Water

Matsumura

Yong

2014

Biofuels and Biorefineries

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Supercritical water (SCW) is expected to be a green solvent for dissolving substances, for chemical synthesis, or for chemical reactions, and thus various study has been carried out. Production of chemicals has been found possible in SCW. This chapter reviews the chemical production in terms of feedstocks and reactions. The feedstocks can include biomass (cellulose, hemicellulose and lignin), plastics, other wastes (e.g., tire, rubber), inorganics and waste water. The reactions include SCW gasification (where hydrolysis and pyrolysis take important roles), SCW oxidation, depolymerization, precipitation, hydrothermal synthesis, other organic reactions for synthesis of chemicals. In these reactions, roles of H 2 O are: (1) Reactant/product (hydrolysis, hydration, hydrogen source and freeradical chemistry) or catalyst (Acid/base catalyst precursor and catalyst in the transition state); (2) Intermolecular interactions in high temperature water: Solvation effects (effects of preferential solvation, hydrophobicity and solvent dynamics) and density inhomogeneity effects (ions, organic compounds, noble gases and radicals); (3) Medium: Energy transfer, diffusion and solvent cages and phase behavior. However, low selectivity and yield and high production cost are barriers for the commercialization of production of chemicals in SCW.

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Chemical Processing in High-Pressure Aqueous Environments. 4. Continuous-Flow Reactor Process Development Experiments for Organics Destruction

Cited by 126 publications

References 9 publications

Supercritical water gasification of RDF and its components over RuO2/γ-Al2O3 catalyst: New insights into RuO2 catalytic reaction mechanisms

Supercritical water gasification of RDF and its components over RuO2/γ-Al2O3 catalyst: New insights into RuO2 catalytic reaction mechanisms

Production of Fuel Gas through the Hydrothermal Gasification of Wastewater Using Highly Active Carbon-Base Catalyst

Production of Chemicals in Supercritical Water

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