Oxidation of Phenolics in Supercritical Water. Quarterly Report, 1 June 1995--30 November 1995 PDF Download
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Author: Publisher: ISBN: Category : Languages : en Pages : 7
Book Description
Our focus these past two quarters involved experimental work concerning the cresol reaction products and the supercritical water oxidation (SCWO) of some of these products. This work included a quantitative investigation of the products from the SCWO of m- and p- cresol. Hydroxybenzaldehydes were found to be the intermediate products from the oxidation of cresols at supercritical conditions. We studied the destruction kinetics of the hydroxybenzaldehydes in supercritical water. We continued our study of the use of structure --reactivity relationships and discovered that there are factors causing these relationships to not be applicable to our current system of compounds.
Author: Publisher: ISBN: Category : Languages : en Pages : 7
Book Description
Our focus these past two quarters involved experimental work concerning the cresol reaction products and the supercritical water oxidation (SCWO) of some of these products. This work included a quantitative investigation of the products from the SCWO of m- and p- cresol. Hydroxybenzaldehydes were found to be the intermediate products from the oxidation of cresols at supercritical conditions. We studied the destruction kinetics of the hydroxybenzaldehydes in supercritical water. We continued our study of the use of structure --reactivity relationships and discovered that there are factors causing these relationships to not be applicable to our current system of compounds.
Author: Publisher: ISBN: Category : Languages : en Pages : 9
Book Description
Over the past two quarters, our work has focused on three main areas. The first area of interest involved a reexamination of the rate laws that were formed in past quarters. A possible error was discovered for the analytical methods used in the o-cresol oxidation study and the data were corrected, yielding a new rate equation. The data for hydroxybenzaldehydes were studied again, this time as a system of parallel oxidation and thermolysis reactions. The second area in which progress was made was the study of the thermolysis of nitrophenols and dihydroxybenzenes in supercritical water. These investigations were needed to determine the effect that pyrolysis or hydrolysis had on our previous supercritical water oxidation experiments. Thirdly, we have continued to investigate the use of molecular orbital theory in the determination reactivity indices. A reactivity index, such as the enthalpy of formation, may be used in a structure-reactivity relationship to summarize the kinetics for the oxidation of phenolics in supercritical water. Progress in each of these areas is summarized.
Author: Publisher: ISBN: Category : Languages : en Pages : 10
Book Description
Oxidation reactions are accomplished in an isothermal, high-pressure, flow reactor designed specifically for operation at supercritical water conditions. The reactor feed stream is prepared by mixing two separate streams. One stream is an aqueous solution of the phenolic reactant and the second stream is water with dissolved oxygen. Controlling the flow rates of these two streams allows us to control the reactor residence time and the relative amounts of the phenol and oxygen fed to the reactor. The reactor effluent is cooled and depressorized and then collected for analysis. The gaseous products are analyzed by gas chromatography (GC). The liquid-phase products are analyzed by GC, high-performance liquid chromatography, and GC-mass spectrometry. Our work to date has focused on the oxidation of cresols in SCW. We have explored the effects of temperature, pressure, and the concentrations of o-cresol, oxygen, and water. Table I gives these experimental conditions and the resulting ocresol conversions. We reported a portion of this data in our previous quarterly report. New information is given in the last three columns where we report the molar yields of phenol, CO2, and CO. Molar yields were calculated as the molar flow rate of a given product divided by the initial molar flow rate of o-cresol and normalized by the stoichiometric coefficient. Earlier, we used the o-cresol conversion data to determine the parameters in a global reaction rate law for o-cresol disappearance.
Author: Publisher: ISBN: Category : Languages : en Pages : 5
Book Description
An environmental hazard associated with coal liquefaction and gasification is the generation of aqueous waste streams containing phenolics and carcinogenic organics such as polynuclear aromatics. Oxidation in supercritical water (SCW) is an emerging technology for the ultimate destruction of phenolics and other organics in waste water streams. SCW oxidation involves the oxidation of organics in an aqueous medium at temperatures between 400--650°C and pressures around 250 atm. These conditions exceed the thermodynamic critical point of water, hence the water is said to be supercritical. Wastes can be converted by SCWO to benign products: carbon is converted to CO2, hydrogen to H2O, and nitrogen to N2 or N2O (but not NO(subscript x)). The objective of this project is to oxidize selected phenolics in SCW and then determine the reaction kinetics (rate constants, reaction orders, activation energies) and the reaction pathways. These reaction fundamentals can then be used to evaluate, design, optimize, and control coal-conversion waste water treatment processes based on SCW oxidation. Our work to date has focused on the oxidation of o-cresol in SCW. We have explored the effects of temperature, pressure, and the concentrations of cresol, oxygen and water.
Author: Publisher: ISBN: Category : Languages : en Pages : 11
Book Description
An environmental hazard associated with coal liquefaction and gasification is the generation of aqueous waste streams containing phenolics and carcinogenic organics such as polynuclear aromatics. Oxidation in supercritical water (SCW) is an emerging technology for the ultimate destruction of phenolics and other organics in waste water streams. SCW oxidation involves the oxidation of organics in an aqueous medium at temperatures between 400--650 C and pressures around 250 atm. These conditions exceed the thermodynamic critical point of water, hence the water is said to be supercritical. Wastes can be converted by SCWO to benign products: carbon is converted to CO2, hydrogen to H2O, and nitrogen to N2 or N2O (but not NO(subscript x)). The objective of this project is to oxidize selected phenolics in SCW and then determine the reaction kinetics (rate constants, reaction orders, activation energies) and the reaction pathways. These reaction fundamentals can then be used to evaluate, design, optimize, and control coal-conversion waste water treatment processes based on SCWO.
Author: Publisher: ISBN: Category : Languages : en Pages : 13
Book Description
An environmental hazard associated with coal liquefaction and gasification is the generation of aqueous waste streams containing phenolics and carcinogenic organics such as polynuclear aromatics. Oxidation in supercritical water (SCW) is an emerging technology for the ultimate destruction of phenolics and other organics in waste water streams. SCW oxidation involves the oxidation of organics in an aqueous medium at temperatures between 400-650°C and pressures around 250 atm. These conditions exceed the thermodynamic critical point of water, hence the water is said to be supercritical. Wastes can be converted by SCWO to benign products: carbon is converted to CO2, hydrogen to H2O, and nitrogen to N2 or N2O (but not NO{sub X}). SCWO possesses several attractive features. (1) The effluents from the SCWO process can be collected or held in a recycle loop so the process can be easily {open_quotes}bottled up{close_quotes} with no uncontrolled emissions should an upset occur. (2) The oxidation reaction is exothermic, so it is possible to operate the SCWO reactor in an autothermal mode. That is, the oxidation of the organic material in the aqueous stream liberates sufficient heat to maintain the elevated reactor temperature and also preheat the feed. Thus, after start-up, the process would not require an external energy source and could even be used to produce energy provided the organics content in the feed stream was sufficiently high. (3) Operating at supercritical conditions also provides a single, homogeneous fluid phase in the reactor. Indeed, water above its critical point has a high solubility for organics, and it is totally miscible with oxygen. (4) The temperature in SCWO is high enough to provide rapid reaction rates but not so high that alloys begin to lose their mechanical strength. Thus, the oxidation of organics goes essentially to completion in a very short time (a few seconds).
Author: Publisher: ISBN: Category : Languages : en Pages : 9
Book Description
The overall objective of this research project is to obtain the reaction engineering information required to evaluate the utility of catalytic supercritical water oxidation (SCWO) for treating wastes arising from coal conversion processes. Our more specific objectives for this first phase of the project were: 1. to recruit and train a graduate student to work on this project 2. to construct a reactor system for the experimental studies 3. to initiate catalytic SCWO experiments and identify an active catalyst. Each of these three objectives has been met. The literature search revealed that both CuO and Mno2 are effective catalysts for the oxidation of organics (including phenol) in aqueous streams. Recently, these materials have also shown promise in catalytic supercritical water oxidation. Accordingly, our initial experiments have employed CuO and MhO2 catalysts that are commercially available. The catalyst we used in these initial studies, CARLITE 150 from Carus Chemical Company, has been commercially used in treating volatile organic compounds generated in various chemical processes. It contains MnO2 and CuO supported on Al2O3. The commercial catalyst pellets were ground to powders and separated by size before use. We used phenol as the first model pollutant to study because it is ubiquitous in wastewaters and there is a large data base for non- catalytic SCWO with which we can contrast results from catalytic SCWO.
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