Polyethylene conversion in supercritical water

Watanabe, Masaru; Hirakoso, Hideyuki; Sawamoto, Shuhei; Adschiri, Tadafumi; Arai, Kunio

doi:10.1016/s0896-8446(98)00058-8

Cited by 109 publications

(65 citation statements)

References 5 publications

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“…If the second prediction is correct, the experimental v value for the volatiles produced at higher T, indicative of nonstatistical BB products, should increase with increasing T. While the high-T data in Figure 2 appear relatively internally consistent with v ≈ 0.11, the internally inconsistent low-T data in Figure 3 are too scattered and/or incomplete to test the prediction. Thus, the data of Watanabe and co-workers 75 and Murata and co-workers 19 indeed suggest a notably lower v value, near the RS limit, but the other data 63,64 do not.…”

Section: Computational Model For Initial Product Distributionsmentioning

confidence: 81%

Reexamination of the Pyrolysis of Polyethylene: Data Needs, Free-Radical Mechanistic Considerations, and Thermochemical Kinetic Simulation of Initial Product-Forming Pathways

Poutsma

2003

Macromolecules

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Gaps in the voluminous data on pyrolysis of polyethylene that impede mechanistic understanding are highlighted, especially for H:C material balances, product distributions at varying conversions in isothermal closed systems, and inconsistencies between GC and FIMS analyses of products with lower volatility. Thermochemical kinetic estimates are made for the rates of various initiation processes; these suggest that molecular disproportionation contributes to chain initiation, along with homolysis, at lower Mn. Simulations indicate that the standard statistical test for random scission, a linear relationship between log Nc and c for volatile products, is not generally valid in open systems, and its empirical observation implies restrictions on the dependence of the rate of volatilization on c.Simulations of the initial distributions of volatile products and residue functionalities were performed based on propagation rate constants estimated by thermochemical kinetic procedures. The practice of deducing the amount of backbiting from positive deviations at lower c from the linear log N c-c relationship established for higher c values is shown to underestimate the fraction of backbiting because the latter will give some products at every c so long as the 1,5-shift is not exclusive (k15 . k16 > k14). Compositions of volatiles at finite conversions were simulated by formal superposition of (a) backbiting and unzipping products predicted from this kinetic model and (b) random scission products, which form only after multiple bond cleavages, predicted from a statistical model. Comparisons with experimental data showed some success but were limited by data gaps and inconsistencies.

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Section: Computational Model For Initial Product Distributionsmentioning

confidence: 81%

Reexamination of the Pyrolysis of Polyethylene: Data Needs, Free-Radical Mechanistic Considerations, and Thermochemical Kinetic Simulation of Initial Product-Forming Pathways

Poutsma

2003

Macromolecules

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“…This trend is consistent with our previous findings 7) . However, the opposite trend was found in polyethylene pyrolysis under supercritical water conditions 8) . Molecular weight decreased and 1-alkene/n-alkane ratio of light products increased with higher water density because the supercritical water conditions promoted polyethylene pyrolysis due to dissolution of some hydrocarbons in supercritical water 8) .…”

Section: E F F E C T O F F L O W R a T E R A T I O O F S T E A M Tmentioning

confidence: 87%

“…However, the opposite trend was found in polyethylene pyrolysis under supercritical water conditions 8) . Molecular weight decreased and 1-alkene/n-alkane ratio of light products increased with higher water density because the supercritical water conditions promoted polyethylene pyrolysis due to dissolution of some hydrocarbons in supercritical water 8) . In contrast, the present study found that steam did not promote heavy oil cracking but rather hydrogenation of product oil.…”

Section: E F F E C T O F F L O W R a T E R A T I O O F S T E A M Tmentioning

confidence: 87%

Catalytic Cracking of Heavy Oil with Iron Oxide-based Catalysts Using Hydrogen and Oxygen Species from Steam

Fumoto

Sugimoto

Sato

et al. 2015

J. Jpn. Petrol. Inst.

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This study investigated the transfer of oxygen and hydrogen species from steam to product during the catalytic cracking of heavy oil with iron oxide-based catalysts containing zirconia and alumina. Light oil and carbon dioxide were produced in the catalytic oxidative cracking of petroleum residual oil in the presence of steam. The alkene/alkane ratio of light aliphatic hydrocarbons decreased and carbon dioxide yield increased with higher flow rate ratio of steam to feedstock. The steam catalytic cracking of dodecylbenzene as a model compound of heavy oil showed lower alkene/alkane ratio and generation of a small amount of oxygen-containing compounds. The oxygen species derived from steam reacted with heavy oil and were transferred to carbon dioxide and a small amount of oxygen-containing compounds, producing hydrogen species from the steam. The hydrogen species were transferred to light hydrocarbons, thus suppressing alkene generation. The alkene/alkane ratio decreased with higher supporting zirconia content in the catalyst because zirconia promotes hydrogen generation from steam.

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“…The gasification of waste plastic in supercritical water also attracted much attention. Supercritical water gasification of waste plastics and the model compounds (such as polyethylene) were investigated by many researchers (Watanabe et al, 1998;Watanabe et al, 2001;Shibasaki et al, 2004;Su et al, 2004;Takeshita et al, 2004;Su et al, 2007). The anaerobic organic wastewater from wheat straw includes acids (acetic acid, butyric acid) and ethanol etc.…”

Section: Organic Wastesmentioning

confidence: 99%