Comparison of consumer perspectives of the natural and commercial synthetic chemical-based mosquito repellent products
- Authors: Ndoyana, Lusanda
- Date: 2019
- Subjects: Insect baits and repellents , Mosquitoes -- Control Consumers -- Attitudes Consumers -- South Africa
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/42902 , vital:36704
- Description: The present study was conducted to determine the perceptions of consumers between the natural mosquito repellent products and the synthetic chemical mosquito repellent products. The perception is that natural mosquito repellent products are more effective than synthetic chemical mosquito repellents based on odour, cost and quality. A comparison of the two products was done in a form of a structured questionnaire where randomly selected participants were given two questionnaires. The participants were asked to provide their perceptions concerning cost, quality and odour. Each participant was also given one formulated natural (green) candle and one synthetic (white) chemical mosquito repellent product. The formulated natural candles contain Oil of Lemon Eucalyptus (OLE) as the active ingredient. OLE is a natural plant-based repellent which is extracted from the leaves and twigs of the lemon-scented gum eucalyptus plant. The results showed that both products were effective in terms of cost, product quality and odour. However, the natural mosquito repellent product was more effective than the synthetic chemical product based on the observed p-value results.
- Full Text:
- Date Issued: 2019
- Authors: Ndoyana, Lusanda
- Date: 2019
- Subjects: Insect baits and repellents , Mosquitoes -- Control Consumers -- Attitudes Consumers -- South Africa
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/42902 , vital:36704
- Description: The present study was conducted to determine the perceptions of consumers between the natural mosquito repellent products and the synthetic chemical mosquito repellent products. The perception is that natural mosquito repellent products are more effective than synthetic chemical mosquito repellents based on odour, cost and quality. A comparison of the two products was done in a form of a structured questionnaire where randomly selected participants were given two questionnaires. The participants were asked to provide their perceptions concerning cost, quality and odour. Each participant was also given one formulated natural (green) candle and one synthetic (white) chemical mosquito repellent product. The formulated natural candles contain Oil of Lemon Eucalyptus (OLE) as the active ingredient. OLE is a natural plant-based repellent which is extracted from the leaves and twigs of the lemon-scented gum eucalyptus plant. The results showed that both products were effective in terms of cost, product quality and odour. However, the natural mosquito repellent product was more effective than the synthetic chemical product based on the observed p-value results.
- Full Text:
- Date Issued: 2019
Synthesis of P-Methane-3,8-Diol
- Authors: Mpuhlu, Batsho
- Date: 2007
- Subjects: Insect baits and repellents
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10411 , http://hdl.handle.net/10948/570 , http://hdl.handle.net/10948/d1011717 , Insect baits and repellents
- Description: The synthesis of para-menthane-3,8-diol in a batch reactor was investigated in some detail with the view to evaluate the potential of producing said p-menthane- 3,8-diol in a continuous-flow reactor from the results obtained from the batch process. The methodology used as base for this investigation was a published procedure by Takasago of Japan. The Takasago-method produced 92.3 percent Yield for the product para-menthane-3,8-diol, and 2.7 percent Yield of the by-product, acetal. The objective for this investigation was to produce a minimum p-menthane-3,8- diol content of 97.0 percent and a maximum content of 3.0 percent for the by-product acetal. The batch production process was evaluated in detail using statistical experimental design methodologies. Three process variables, namely catalyst loading, organic/aqueous phase ratio and reaction temperature were selected for the study. The experimental method was based on the Takasago procedure, however the substrate was added as a single slug as opposed to gradual addition method and the reaction period was reduced to 30 minutes. Apart from statistical analysis, mechanistic aspects were also used to interpret the following results. Using a central composite design, three response models (one for the conversion of citronellal, p-menthane-3,8-diol and acetal formation) were determined. An analysis of the response surfaces indicated that, to increase the citronellal conversion all three variables should be increased. To increase the amount of pmenthane- 3,8-diol, the reaction temperature and acid concentration should be increased, but the Aq/org ratio should be decreased as the acid catalyst concentration is increased. To minimize the amount of acetals formed during the reaction, the Aq/org ratio should be decreased; temperature and acid concentration can be decreased or increased. The reaction mechanism suggested that p-menthane-3,8-diol may be formed along two pathways: One pathway directly forms p-menthane-3,8-diol, whilst the second pathway forms the isopulegol first, then proceeds to form product by hydrolysis. The acetal is formed as result of the reaction between unreacted citronellal and p-menthane-3,8-diol. From the design experiments it was suggested that reaction time can be reduced to 8 minutes at reaction temperatures between, 80-85 0C The product and acetal were isolated by simple vacuum evaporation of the low boiling citronellal and isopulegol. Results from recycling the catalyst phase were similar to those of the initial process. The results of this investigation has clearly shown that with a proper understanding of the effect of process variables on the performance of the batch synthesis route, the conversion of this traditionally batch (actually semi-batch) process into a continuous process is quite feasible provided that suitable equipment is available. The most important features required for such equipment would be: Intense mixing throughout the reaction zone so as to maximise the surface area between the two immiscible phases, hence the rate of mass transfer between the two phases; and the ability to run reactions above the boiling point of water. Plans for the further study of the process are already well underway and sections of static mixing tubes have been acquired to build a continuous lab scale tubular reactor that would be capable of providing the level of mixing required.
- Full Text:
- Date Issued: 2007
- Authors: Mpuhlu, Batsho
- Date: 2007
- Subjects: Insect baits and repellents
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10411 , http://hdl.handle.net/10948/570 , http://hdl.handle.net/10948/d1011717 , Insect baits and repellents
- Description: The synthesis of para-menthane-3,8-diol in a batch reactor was investigated in some detail with the view to evaluate the potential of producing said p-menthane- 3,8-diol in a continuous-flow reactor from the results obtained from the batch process. The methodology used as base for this investigation was a published procedure by Takasago of Japan. The Takasago-method produced 92.3 percent Yield for the product para-menthane-3,8-diol, and 2.7 percent Yield of the by-product, acetal. The objective for this investigation was to produce a minimum p-menthane-3,8- diol content of 97.0 percent and a maximum content of 3.0 percent for the by-product acetal. The batch production process was evaluated in detail using statistical experimental design methodologies. Three process variables, namely catalyst loading, organic/aqueous phase ratio and reaction temperature were selected for the study. The experimental method was based on the Takasago procedure, however the substrate was added as a single slug as opposed to gradual addition method and the reaction period was reduced to 30 minutes. Apart from statistical analysis, mechanistic aspects were also used to interpret the following results. Using a central composite design, three response models (one for the conversion of citronellal, p-menthane-3,8-diol and acetal formation) were determined. An analysis of the response surfaces indicated that, to increase the citronellal conversion all three variables should be increased. To increase the amount of pmenthane- 3,8-diol, the reaction temperature and acid concentration should be increased, but the Aq/org ratio should be decreased as the acid catalyst concentration is increased. To minimize the amount of acetals formed during the reaction, the Aq/org ratio should be decreased; temperature and acid concentration can be decreased or increased. The reaction mechanism suggested that p-menthane-3,8-diol may be formed along two pathways: One pathway directly forms p-menthane-3,8-diol, whilst the second pathway forms the isopulegol first, then proceeds to form product by hydrolysis. The acetal is formed as result of the reaction between unreacted citronellal and p-menthane-3,8-diol. From the design experiments it was suggested that reaction time can be reduced to 8 minutes at reaction temperatures between, 80-85 0C The product and acetal were isolated by simple vacuum evaporation of the low boiling citronellal and isopulegol. Results from recycling the catalyst phase were similar to those of the initial process. The results of this investigation has clearly shown that with a proper understanding of the effect of process variables on the performance of the batch synthesis route, the conversion of this traditionally batch (actually semi-batch) process into a continuous process is quite feasible provided that suitable equipment is available. The most important features required for such equipment would be: Intense mixing throughout the reaction zone so as to maximise the surface area between the two immiscible phases, hence the rate of mass transfer between the two phases; and the ability to run reactions above the boiling point of water. Plans for the further study of the process are already well underway and sections of static mixing tubes have been acquired to build a continuous lab scale tubular reactor that would be capable of providing the level of mixing required.
- Full Text:
- Date Issued: 2007
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