An investigation into the antibacterial activites of medicinal plants traditionally used in the Eastern Cape to treat lung infections in cystic fibrosis patients
- Authors: Wilson, Katherine Leigh
- Date: 2004
- Subjects: Medicinal plants -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10985 , http://hdl.handle.net/10948/242 , Medicinal plants -- South Africa -- Eastern Cape
- Description: Lung infections in cystic fibrosis (CF) patients are very serious and are usually fatal. Prolonged antibiotic treatment can result in the development of antibiotic resistance. Thus, studies are required to determine if traditional medicinal plants have any significant effects (i.e. antibacterial effects in this case) on certain bacteria causing lung infections in CF patients, providing possible alternative treatment. The aim of this study was to test the effects of several Eastern Cape medicinal plants on specific bacteria causing lung infections in CF patients, for possible antibacterial activities. Four plants traditionally used to treat lung infections (Artemisia afra, Dodonaea angustifolia, Leonotis leonurus & Tulbaghia violacea), and different strains of four bacteria (Staphylococcus aureus, Pseudomonas aeruginosa, Pseudomonas species & Klebsiella pneumoniae), usually causing lung infections were investigated. Methanol, aqueous and acetone extraction methods were used to make extracts of the various plants chosen. A decoction of each plant was also investigated. An adapted microtitre plate method for testing the antibacterial activity of the plant extracts against the chosen bacteria was used. The minimum inhibitory concentration (MIC) of each plant extract was determined by means of this method.
- Full Text:
- Date Issued: 2004
- Authors: Wilson, Katherine Leigh
- Date: 2004
- Subjects: Medicinal plants -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10985 , http://hdl.handle.net/10948/242 , Medicinal plants -- South Africa -- Eastern Cape
- Description: Lung infections in cystic fibrosis (CF) patients are very serious and are usually fatal. Prolonged antibiotic treatment can result in the development of antibiotic resistance. Thus, studies are required to determine if traditional medicinal plants have any significant effects (i.e. antibacterial effects in this case) on certain bacteria causing lung infections in CF patients, providing possible alternative treatment. The aim of this study was to test the effects of several Eastern Cape medicinal plants on specific bacteria causing lung infections in CF patients, for possible antibacterial activities. Four plants traditionally used to treat lung infections (Artemisia afra, Dodonaea angustifolia, Leonotis leonurus & Tulbaghia violacea), and different strains of four bacteria (Staphylococcus aureus, Pseudomonas aeruginosa, Pseudomonas species & Klebsiella pneumoniae), usually causing lung infections were investigated. Methanol, aqueous and acetone extraction methods were used to make extracts of the various plants chosen. A decoction of each plant was also investigated. An adapted microtitre plate method for testing the antibacterial activity of the plant extracts against the chosen bacteria was used. The minimum inhibitory concentration (MIC) of each plant extract was determined by means of this method.
- Full Text:
- Date Issued: 2004
The evaluation of waste minimization/waste treatment strategies for a commercial production process of 4-methyl-3-thiosemicarbazide
- Authors: Bennen, Wilroy
- Date: 2002
- Subjects: Hazardous wastes , Hazardous substances -- Analysis
- Language: English
- Type: Thesis , Masters , MTech (Chemistry)
- Identifier: vital:10951 , http://hdl.handle.net/10948/97 , Hazardous wastes , Hazardous substances -- Analysis
- Description: Chemical synthesis is closely related to waste minimization. There is no chemical process that does not produce waste. The methods used by industry to deal with this waste is a major environmental concern. This thesis describes the laboratory scale waste minimization and waste treatment strategies for the commercial production process of 4-methyl-3-thiosemicarbazide (MTSC). The production process of 4-methyl-3-thiosemicarbazide was investigated with the aim of increasing the isolated yield of MTSC and at the same time decrease the amount and toxicity of effluent obtained. During this study, parameters were investigated such as the use of excess DIPEA and the temperature of the reaction. Preliminary studies clearly showed that both factors have a significant influence on the final yield of the product. The next part of the investigation was to optimize the two parameters influencing the isolated yield of the MTSC. For this investigation, a multi factorial design was used to determine the optimum conditions in the MTSC yield response. From the results obtained, it was clear that the excess of DIPEA and the temperature of the reaction both need to be high to obtain high yields. These theoretical results were confirmed by results obtained practically, where yields of up 82 % were obtained, but it became clear that even higher yields could be obtained since chromatographic results showed yeilds as high as 90 %. The mass balance of the MTSC synthesis showed a loss of approximately 30 grams per reaction. This loss may have an influence on the final yield. The effluent obtained during the synthesis of MTSC was investigated and a waste treatment protocol was established to reduce the high COD value of the MTSC effluent. The protocol consists of two steps used for the clean up of the effluent. The first being a cooling step; the effluent was cooled at 0oC to induce precipitation of a solid, consisting mostly of MTSC. The second step is a high pressure wet oxidation of the effluent with oxygen in a high pressure reactor. The remaining compounds in the effluent were oxidized, resulting in another precipitate, consisting mostly of sulphur. After the oxidation the COD value of the effluent was decreased by 98 % to a value of 0.4 %. The MTSC present in the precipitate obtained after cooling could be isolated and purified, to add to the yield of the synthesis. The sulphur obtained during the oxidation could also be isolated and reused, or sold to prevent it from contaminating the environment.
- Full Text:
- Date Issued: 2002
- Authors: Bennen, Wilroy
- Date: 2002
- Subjects: Hazardous wastes , Hazardous substances -- Analysis
- Language: English
- Type: Thesis , Masters , MTech (Chemistry)
- Identifier: vital:10951 , http://hdl.handle.net/10948/97 , Hazardous wastes , Hazardous substances -- Analysis
- Description: Chemical synthesis is closely related to waste minimization. There is no chemical process that does not produce waste. The methods used by industry to deal with this waste is a major environmental concern. This thesis describes the laboratory scale waste minimization and waste treatment strategies for the commercial production process of 4-methyl-3-thiosemicarbazide (MTSC). The production process of 4-methyl-3-thiosemicarbazide was investigated with the aim of increasing the isolated yield of MTSC and at the same time decrease the amount and toxicity of effluent obtained. During this study, parameters were investigated such as the use of excess DIPEA and the temperature of the reaction. Preliminary studies clearly showed that both factors have a significant influence on the final yield of the product. The next part of the investigation was to optimize the two parameters influencing the isolated yield of the MTSC. For this investigation, a multi factorial design was used to determine the optimum conditions in the MTSC yield response. From the results obtained, it was clear that the excess of DIPEA and the temperature of the reaction both need to be high to obtain high yields. These theoretical results were confirmed by results obtained practically, where yields of up 82 % were obtained, but it became clear that even higher yields could be obtained since chromatographic results showed yeilds as high as 90 %. The mass balance of the MTSC synthesis showed a loss of approximately 30 grams per reaction. This loss may have an influence on the final yield. The effluent obtained during the synthesis of MTSC was investigated and a waste treatment protocol was established to reduce the high COD value of the MTSC effluent. The protocol consists of two steps used for the clean up of the effluent. The first being a cooling step; the effluent was cooled at 0oC to induce precipitation of a solid, consisting mostly of MTSC. The second step is a high pressure wet oxidation of the effluent with oxygen in a high pressure reactor. The remaining compounds in the effluent were oxidized, resulting in another precipitate, consisting mostly of sulphur. After the oxidation the COD value of the effluent was decreased by 98 % to a value of 0.4 %. The MTSC present in the precipitate obtained after cooling could be isolated and purified, to add to the yield of the synthesis. The sulphur obtained during the oxidation could also be isolated and reused, or sold to prevent it from contaminating the environment.
- Full Text:
- Date Issued: 2002
Evaluation of Lewis acid catalysed and other nitration strategies for the selective nitration of cresols
- Van Niekerk, Rudolf Jacob Francois
- Authors: Van Niekerk, Rudolf Jacob Francois
- Date: 2001
- Subjects: Nitration
- Language: English
- Type: Thesis , Masters , MTech (Chemistry)
- Identifier: vital:10957 , http://hdl.handle.net/10948/60 , Nitration
- Description: The nitration of m- and p-cresol was investigated under mild reaction conditions in a number of solvents; the effects of certain nitration catalysts were also evaluated. These different reaction parameters were evaluated in terms of their effect on a number of important reaction responses. Other important factors that were investigated were the manipulation of the isomer ratios by changing reaction parameters, as well as important process chemistry information, such as product distribution, isolation and purification, identification of side products formed, and evaluation of the heat of reaction. Use was made of an experimental design system to evaluate the effect of reaction parameters on the chosen design responses. It was found that the ratio of para to ortho nitrocresol products could be influenced slightly by using low concentrations of nitric acid and low reaction temperatures. A different mechanism for the formation of 2-methyl-1,4-benzoquinone (from mcresol nitration) was proposed (compared with that previously reported), which could explain a “one mole nitric acid” pathway and the fact that only the pbenzoquinone isomer was observed. Reaction side products were identified and found to consist of dimers of cresol and nitrocresol, which were probably the result of oxidation of the cresol, subsequent formation of a quinomethide intermediate and reaction with either the product or the substrate. The heat of nitration was determined for various reaction systems and found to be governed by two factors, namely the actual nitration process and also an oxidation process, which is responsible for the formation of side products.
- Full Text:
- Date Issued: 2001
- Authors: Van Niekerk, Rudolf Jacob Francois
- Date: 2001
- Subjects: Nitration
- Language: English
- Type: Thesis , Masters , MTech (Chemistry)
- Identifier: vital:10957 , http://hdl.handle.net/10948/60 , Nitration
- Description: The nitration of m- and p-cresol was investigated under mild reaction conditions in a number of solvents; the effects of certain nitration catalysts were also evaluated. These different reaction parameters were evaluated in terms of their effect on a number of important reaction responses. Other important factors that were investigated were the manipulation of the isomer ratios by changing reaction parameters, as well as important process chemistry information, such as product distribution, isolation and purification, identification of side products formed, and evaluation of the heat of reaction. Use was made of an experimental design system to evaluate the effect of reaction parameters on the chosen design responses. It was found that the ratio of para to ortho nitrocresol products could be influenced slightly by using low concentrations of nitric acid and low reaction temperatures. A different mechanism for the formation of 2-methyl-1,4-benzoquinone (from mcresol nitration) was proposed (compared with that previously reported), which could explain a “one mole nitric acid” pathway and the fact that only the pbenzoquinone isomer was observed. Reaction side products were identified and found to consist of dimers of cresol and nitrocresol, which were probably the result of oxidation of the cresol, subsequent formation of a quinomethide intermediate and reaction with either the product or the substrate. The heat of nitration was determined for various reaction systems and found to be governed by two factors, namely the actual nitration process and also an oxidation process, which is responsible for the formation of side products.
- Full Text:
- Date Issued: 2001
The development and evaluation of procedures for the synthesis of phenolic ethers by Baeyer-Villiger oxidation
- Authors: Hoffmann, Petra
- Date: 2001
- Subjects: Ethers , Phenols
- Language: English
- Type: Thesis , Masters , MTech (Chemistry)
- Identifier: vital:10955 , http://hdl.handle.net/10948/51 , Ethers , Phenols
- Description: A novel preparative method has been discovered in our laboratories which produces hydroxy-substituted phenolic ethers in a simple one-pot process. Initially it was found that 4-hydroxyacetophenone, when oxidized in the presence of ammonium peroxydisulfate and concentrated sulfuric acid in methanol, resulted in 4- methoxyphenol as product in high yield. Being novel, no information about the method was available in the literature, and hence it was our task to study the reaction more extensively. The scope of the reaction was investigated in that different reagents and substrates, as well as alternative oxidants, catalysts and alcohols (or reagents which may be envisaged to behave similarly to alcohols) were used. The studies showed that 4- hydroxy-substituted benzaldehyde and acetophenone, vanillin, fuchsones and stilbenequinones as substrates all successfully afforded the phenolic ether. Other oxidants such as hydrogen peroxide, sodium perborate etc. also afforded the phenolic ether but were less effective. The use of other acids than sulfuric acid resulted in comparable or lower yields of the desired phenolic ether. When the use of alcohols or similar reagents was varied, it was found that methanol, ethanol, benzyl alcohol, allyl alcohol, but-3-en-1-ol, hex-5-en-1-ol and undec-10-en-1-ol all afforded the desired ethers in significant yields. In an investigation to determine how this method may be useful for industrial applications, it was observed that compounds such as 3,5-di-tert-butyl-4-hydroxysubstituted alkenyloxy phenols, having potential application as antioxidant precursors in the polymer industry, may be prepared. Results showed that the reaction became less efficient when the alkenyl chain length was increased. The use of different acids and oxidants, the change of the oxidant:substrate ratio and the addition of a potential lanthanide catalyst did not improve the yield of the desired ether. A mechanism for the reaction was proposed which involved an initial Baeyer-Villiger oxygen insertion step to afford an ester which was hydrolysed in situ to hydroquinone. The remaining oxidant was then involved in oxidizing some of the soformed hydroquinone to benzoquinone. It was then proposed that these two compounds, i.e., hydroquinone and benzoquinone, interacted with each other in solution, forming a charge-transfer complex. According to our proposal, the carbonyl group of the benzoquinone, when complexed with hydroquinone in solution, was then attacked by nucleophilic reagents such as alcohols. Etherification hence resulted as a consequence of this attack. A statistical experimental evaluation and optimization study was then performed which led to a system that produced the phenolic ether, 4-methoxyphenol, in an 86% yield. An analysis of the effects of the reaction parameters on the reaction showed that the reaction temperature and the oxidant:substrate ratio played a major role in deciding the effectiveness of the reaction, while the amount of substrate and acidic catalyst had a much smaller influence on the ether yields.
- Full Text:
- Date Issued: 2001
- Authors: Hoffmann, Petra
- Date: 2001
- Subjects: Ethers , Phenols
- Language: English
- Type: Thesis , Masters , MTech (Chemistry)
- Identifier: vital:10955 , http://hdl.handle.net/10948/51 , Ethers , Phenols
- Description: A novel preparative method has been discovered in our laboratories which produces hydroxy-substituted phenolic ethers in a simple one-pot process. Initially it was found that 4-hydroxyacetophenone, when oxidized in the presence of ammonium peroxydisulfate and concentrated sulfuric acid in methanol, resulted in 4- methoxyphenol as product in high yield. Being novel, no information about the method was available in the literature, and hence it was our task to study the reaction more extensively. The scope of the reaction was investigated in that different reagents and substrates, as well as alternative oxidants, catalysts and alcohols (or reagents which may be envisaged to behave similarly to alcohols) were used. The studies showed that 4- hydroxy-substituted benzaldehyde and acetophenone, vanillin, fuchsones and stilbenequinones as substrates all successfully afforded the phenolic ether. Other oxidants such as hydrogen peroxide, sodium perborate etc. also afforded the phenolic ether but were less effective. The use of other acids than sulfuric acid resulted in comparable or lower yields of the desired phenolic ether. When the use of alcohols or similar reagents was varied, it was found that methanol, ethanol, benzyl alcohol, allyl alcohol, but-3-en-1-ol, hex-5-en-1-ol and undec-10-en-1-ol all afforded the desired ethers in significant yields. In an investigation to determine how this method may be useful for industrial applications, it was observed that compounds such as 3,5-di-tert-butyl-4-hydroxysubstituted alkenyloxy phenols, having potential application as antioxidant precursors in the polymer industry, may be prepared. Results showed that the reaction became less efficient when the alkenyl chain length was increased. The use of different acids and oxidants, the change of the oxidant:substrate ratio and the addition of a potential lanthanide catalyst did not improve the yield of the desired ether. A mechanism for the reaction was proposed which involved an initial Baeyer-Villiger oxygen insertion step to afford an ester which was hydrolysed in situ to hydroquinone. The remaining oxidant was then involved in oxidizing some of the soformed hydroquinone to benzoquinone. It was then proposed that these two compounds, i.e., hydroquinone and benzoquinone, interacted with each other in solution, forming a charge-transfer complex. According to our proposal, the carbonyl group of the benzoquinone, when complexed with hydroquinone in solution, was then attacked by nucleophilic reagents such as alcohols. Etherification hence resulted as a consequence of this attack. A statistical experimental evaluation and optimization study was then performed which led to a system that produced the phenolic ether, 4-methoxyphenol, in an 86% yield. An analysis of the effects of the reaction parameters on the reaction showed that the reaction temperature and the oxidant:substrate ratio played a major role in deciding the effectiveness of the reaction, while the amount of substrate and acidic catalyst had a much smaller influence on the ether yields.
- Full Text:
- Date Issued: 2001
The evaluation of autoxidation procedures for the selective oxidation of aliphatic alcohols
- Authors: Bacela, Siyabulela Mawande
- Date: 2001
- Subjects: Oxidation , Aliphatic compounds
- Language: English
- Type: Thesis , Masters , MTech (Chemistry)
- Identifier: vital:10950 , http://hdl.handle.net/10948/59 , Oxidation , Aliphatic compounds
- Description: The homogeneously catalyzed oxidation of 1-propanol by dioxygen in glacial acetic acid using cobalt(II)acetate and sodium bromide as the catalyst system has been investigated with the view of determining the significance of various experimental variables during the oxidation. The results of this investigation show unequivocally that a number of reaction variables have a direct influence upon catalytic activity and hence the reaction products. It is quite evident that the major product of this autoxidation reaction is propionic acid with the respective esters as side-products. This is an indication that the autoxidation mechanism occurs via a two-stage pathway, namely, the oxidation of 1-propanol to propionaldehyde as the primary product and, subsequently, the further oxidation of the propionaldehyde to propionic acid as the major product. Thus the esterification process of the propionic acid with the substrate 1-propanol could be termed as a side-reaction because its not facilitated by the catalyst system and it consumes the formed product. The catalyst activity has been demonstrated to depend on a number of factors, including the bromide concentration, the cobalt(II)acetate concentration, the water concentration, reaction temperature, and the presence of metal acetates as co-catalysts. There is an observed decrease in catalytic activity at high bromide concentration, which may be explained in terms of cobalt bromide complexes that form at these high concentrations. Subsequently, the same trend of catalyst activity reduction at high cobalt(II)acetate concentration may be ascribed to the “inactive” metal complexes that are susceptible to form at high metal ion concentrations. The catalytic activity increases with increase in total concentration and rapidly decreases at very high concentrations. This can be explained in terms of the observations made during the investigation of the effect of cobalt(II)acetate and bromide concentrations. The high increase in catalytic activity with increasing temperature is ascribed to the Arrhenius law, which relates the rate constant for a particular reaction to temperature. However, there is an observed loss of catalyst selectivity at high temperatures which maybe due to two possible factors. The first is simply related to an increased loss of volatile material from the reactor in the oxygen gas stream as the temperature is increased. The second relates to the increasing activity of the catalyst system for the selective decarboxylation of the carboxylic acid product. The addition of water to the reaction system rapidly reduces the catalyst activity. This detrimental effect is an indication that there is an effective competition by water with bromide for coordination sites on cobalt(II), thereby preventing the formation of the active catalyst species. The introduction of metal acetates as co-catalyst reduces the catalyst activity quite dramatically. This inhibition effect is suggested to relate to the redox potential of the respective metal ions. The results of statistical analysis of the experimentally derived response surface during the oxidation of 1-propanol, show no significant lack of fit, and the residuals obtained by applying the response surface to the design settings show that the data is normally distributed. The response surface is therefore reliable, but keeping in mind that the central composite design used is not rotatable so that its predictive power, especially outside the experimental domain investigated, is quite limited. However, several interesting observations were still possible The oxidative dehydrogenation of ethanol over supported noble-metal catalysts has been investigated with the view of identifying the most active supported noble-metal and also to compare this oxidation procedure with the autoxidation procedure. Secondly, the effect of an acidic resin as a co-catalyst was also investigated during the said oxidation. On the basis of results presented in this study during oxidative dehydrogenation of ethanol, catalysts no.2 (10% Pd/C), 8 (2% Pd/Al – Pb-promoted) and 9 (2% Pt/8% Pd/C) appear to be the most active in terms of relative rates, while catalysts 6 (10% Pd/C- Pbpromoted), 7 (5% Pd/C-shell reduced-Pb -promoted) and 10 (5% Pt 5% Pd on C) are more active based on the comparison of average rates. Two other observations are of interest. Firstly, the promotion of the Pd catalysts with lead appears to improve catalyst activity to some extent as shown by the comparisons between catalysts 1 and 5, 4 and 8, 2 and 6 and 3 and 7. Secondly, the introduction of Pt up to equal amounts with palladium seems to produce the most active catalysts. On its own, platinum appears to be a better catalyst than Pd when supported on activated carbon (catalysts 1 and 12). In comparison with the homogeneous, cobalt-bromide catalyzed oxidation of 1- propanol in the liquid-phase, oxidations over noble-metal catalysts in the liquid-phase appear to be significantly less active. The presence of the resin promoted the formation of ethyl acetate to some extent, the improvements are not as dramatic as expected.
- Full Text:
- Date Issued: 2001
- Authors: Bacela, Siyabulela Mawande
- Date: 2001
- Subjects: Oxidation , Aliphatic compounds
- Language: English
- Type: Thesis , Masters , MTech (Chemistry)
- Identifier: vital:10950 , http://hdl.handle.net/10948/59 , Oxidation , Aliphatic compounds
- Description: The homogeneously catalyzed oxidation of 1-propanol by dioxygen in glacial acetic acid using cobalt(II)acetate and sodium bromide as the catalyst system has been investigated with the view of determining the significance of various experimental variables during the oxidation. The results of this investigation show unequivocally that a number of reaction variables have a direct influence upon catalytic activity and hence the reaction products. It is quite evident that the major product of this autoxidation reaction is propionic acid with the respective esters as side-products. This is an indication that the autoxidation mechanism occurs via a two-stage pathway, namely, the oxidation of 1-propanol to propionaldehyde as the primary product and, subsequently, the further oxidation of the propionaldehyde to propionic acid as the major product. Thus the esterification process of the propionic acid with the substrate 1-propanol could be termed as a side-reaction because its not facilitated by the catalyst system and it consumes the formed product. The catalyst activity has been demonstrated to depend on a number of factors, including the bromide concentration, the cobalt(II)acetate concentration, the water concentration, reaction temperature, and the presence of metal acetates as co-catalysts. There is an observed decrease in catalytic activity at high bromide concentration, which may be explained in terms of cobalt bromide complexes that form at these high concentrations. Subsequently, the same trend of catalyst activity reduction at high cobalt(II)acetate concentration may be ascribed to the “inactive” metal complexes that are susceptible to form at high metal ion concentrations. The catalytic activity increases with increase in total concentration and rapidly decreases at very high concentrations. This can be explained in terms of the observations made during the investigation of the effect of cobalt(II)acetate and bromide concentrations. The high increase in catalytic activity with increasing temperature is ascribed to the Arrhenius law, which relates the rate constant for a particular reaction to temperature. However, there is an observed loss of catalyst selectivity at high temperatures which maybe due to two possible factors. The first is simply related to an increased loss of volatile material from the reactor in the oxygen gas stream as the temperature is increased. The second relates to the increasing activity of the catalyst system for the selective decarboxylation of the carboxylic acid product. The addition of water to the reaction system rapidly reduces the catalyst activity. This detrimental effect is an indication that there is an effective competition by water with bromide for coordination sites on cobalt(II), thereby preventing the formation of the active catalyst species. The introduction of metal acetates as co-catalyst reduces the catalyst activity quite dramatically. This inhibition effect is suggested to relate to the redox potential of the respective metal ions. The results of statistical analysis of the experimentally derived response surface during the oxidation of 1-propanol, show no significant lack of fit, and the residuals obtained by applying the response surface to the design settings show that the data is normally distributed. The response surface is therefore reliable, but keeping in mind that the central composite design used is not rotatable so that its predictive power, especially outside the experimental domain investigated, is quite limited. However, several interesting observations were still possible The oxidative dehydrogenation of ethanol over supported noble-metal catalysts has been investigated with the view of identifying the most active supported noble-metal and also to compare this oxidation procedure with the autoxidation procedure. Secondly, the effect of an acidic resin as a co-catalyst was also investigated during the said oxidation. On the basis of results presented in this study during oxidative dehydrogenation of ethanol, catalysts no.2 (10% Pd/C), 8 (2% Pd/Al – Pb-promoted) and 9 (2% Pt/8% Pd/C) appear to be the most active in terms of relative rates, while catalysts 6 (10% Pd/C- Pbpromoted), 7 (5% Pd/C-shell reduced-Pb -promoted) and 10 (5% Pt 5% Pd on C) are more active based on the comparison of average rates. Two other observations are of interest. Firstly, the promotion of the Pd catalysts with lead appears to improve catalyst activity to some extent as shown by the comparisons between catalysts 1 and 5, 4 and 8, 2 and 6 and 3 and 7. Secondly, the introduction of Pt up to equal amounts with palladium seems to produce the most active catalysts. On its own, platinum appears to be a better catalyst than Pd when supported on activated carbon (catalysts 1 and 12). In comparison with the homogeneous, cobalt-bromide catalyzed oxidation of 1- propanol in the liquid-phase, oxidations over noble-metal catalysts in the liquid-phase appear to be significantly less active. The presence of the resin promoted the formation of ethyl acetate to some extent, the improvements are not as dramatic as expected.
- Full Text:
- Date Issued: 2001
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