Different Ziegler-Natta catalysts were employed to polymerize ethylene. To investigate the influences of reaction parameters, namely Al/Ti molar ratio, hydrogen and processing parameters, i.e. ethylene pressure and te...Different Ziegler-Natta catalysts were employed to polymerize ethylene. To investigate the influences of reaction parameters, namely Al/Ti molar ratio, hydrogen and processing parameters, i.e. ethylene pressure and temperature, a Taguchi experimental design was worked out. An L27 orthogonal array was chosen to take the above-mentioned parameters and relevant interactions into account. Response surface method was the tool used to analyze the experimental design results. Al/Ti, ethylene pressure and temperature were selected as experimental design factors, and catalyst activity and polymerization yield were the response parameters. Increasing pressure, due to an increment in monomer accessibility, and rising Al/Ti, because of higher reduction in the catalysts, cause an increase in both polymerization yield and catalyst activity. Nonetheless, a higher temperature, thanks to reducing ethylene solubility in the slurry medium and partially catalyst destruction, lead to a reduction in both response parameters. A synergistic effect was also observed between temperature and pressure. All catalyst activities will reduce in the presence of hydrogen. Molecular weight also shows a decline in the presence of hydrogen as a transfer agent. However, the polydispersity index remains approximately intact. Using SEM, various morphologies, owing to different catalyst morphologies, were seen for the polyethylene.展开更多
Residual stresses can reduce the reliability of plastic injection molding parts. This work is an attempt to model the residual stresses as a function of injection molding parameters. More stress is placed on reducing ...Residual stresses can reduce the reliability of plastic injection molding parts. This work is an attempt to model the residual stresses as a function of injection molding parameters. More stress is placed on reducing the number of input factors and to include all possible interactions. For this purpose, two-stage experimentation is suggested: a factor screening stage and Response Surface optimization stage. In screening stage Taguchi 3 level experimental design is used to classify the input parameters as significant and non-significant factors. Eight input variables were classified into 3 non-significant and 5 significant factors using this screening stage. Thus for the Response Surface optimization stage: instead of doing 160 experiments in Central Composite, 56 are only needed after the screening stage in half Central Composite Design. The best subset and regression model fitting tools in addition to model verification using randomly selected input setting were used to select a model for predicting residual stresses with a verified Root Mean Square Error (RSME) of nearly 0.93 MPa.展开更多
In this work,MIL-101,a metal organic framework,has been synthesized and examined in the adsorptive denitrogenation process.Due to the importance of adsorption capacity and selectivity,the effects of synthesis paramete...In this work,MIL-101,a metal organic framework,has been synthesized and examined in the adsorptive denitrogenation process.Due to the importance of adsorption capacity and selectivity,the effects of synthesis parameters including metal type,reagent ratio,time and temperature on the MIL-101 performance were investigated by measuring quinoline(QUI)separation from iso-octane.The optimum conditions were determined using a Taguchi experimental design and the multiresponse optimization(multivariate statistical)method.Based on the arithmetic mean of normalized QUI adsorption capacity and QUI/dibenzothiophene(DBT)selectivity,as the objective function,the optimum value of synthesis parameters were found to be manganese as metal type in the structure,180°C for synthesis temperature,15h for synthesis time and 1.00 for reagent molar ratio.Under these conditions,QUI adsorption capacity and QUI/DBT selectivity were 19.3 mg-N/g-Ads.and 24.6,respectively.Accordingly,the arithmetic mean between normalized values of these measured parameters was equal to 1.10,which is in good agreement with the predicted value.The MIL-101 produced under optimum conditions was characterized by determining its specific surface area,X-ray powder diffraction patterns and Fourier transform infrared spectroscopy.Finally,isotherm and kinetic studies indicate that the Langmuir isotherm and pseudo-first-order model can successfully describe the experimental data.展开更多
Pure greenish-blue cobalt chromite(Co Cr/_2O_4) nanoparticles with narrow particle range of 4.1±1.9nm and surface area of 78.2 m2·g-1were synthesized through mixed chelates thermolysis of corresponding metal...Pure greenish-blue cobalt chromite(Co Cr/_2O_4) nanoparticles with narrow particle range of 4.1±1.9nm and surface area of 78.2 m2·g-1were synthesized through mixed chelates thermolysis of corresponding metals using 2-Mercaptopyridine N-oxide sodium salt as chelating agent. During the thermolysis procedure,high amount of gases were emitted that led to the formation of nanoparticles with high surface area. The product was characterized by TGA, DTG, XRD, TEM, SEM, LLS, BET and chemical analysis. Design of experiments was performed to fulfill the two levels L_4 Taguchi design. It was found that the temperature and time of thermolysis process have significant effect on the particle size reduction. The Oxidation of trichloroethylene was carried out over Co Cr_2O_4 nanocrystallite. Catalytic activity analysis revealed that the synthesis Co Cr_2O_4 possesses high catalytic activity for this process.展开更多
Extensive use of lambda-cyhalothrin(LC)for agricultural and domestic pest control leads to the accumulation of its residues in soil and water,which poses a serious threat to the environment.Remediation of LC at the po...Extensive use of lambda-cyhalothrin(LC)for agricultural and domestic pest control leads to the accumulation of its residues in soil and water,which poses a serious threat to the environment.Remediation of LC at the point source is the most effective way to avoid its spread and harmful effects.Therefore,this study was planned to investigate the potential of indigenously isolated bacteria for the remediation of LC in cotton-vegetated soils.Three potent LC-degrading bacteria,Brucella intermedia Halol,Alcaligenes faecalis CH1S,and Aquamicrobium terrae CH1T,were isolated from a pyrethroid-contaminated soil.A consortium CHST comprising these three strains was found to exhibit a higher potential for LC degradation as compared to the individual strains.The degradation of LC by CHST was optimized for four varying factors,i.e.,pH,inoculum density(ID),carbon source(CS),and initial pesticide(i.e.,LC)concentration(PC),by applying Taguchi design of experiment.The contributions of these factors to the biodegradation of LC were found to be in the order of pH>CS>PC>ID.The enhanced degradation of LC(84%)was attained at pH 7.0 in minimum salt medium containing 10 mg L^(-1)LC and 3%inoculum.The consortium CHST was also augmented in sterilized and unsterilized soil microcosms at three PCs,i.e.,2,5,and 10 mg kg^(-1).After 21 d of incubation,complete LC degradation was achieved at 2 mg kg^(-1)PC in sterilized as well as unsterilized soil,whereas at higher PCs,the extent of degradation was comparatively less.At PC of 5 mg kg^(-1),88%and 96%LC degradation were observed in sterilized and unsterilized soils,respectively,compared to 79%and90%degradation at 10 mg kg^(-1),respectively.During biodegradation,the major metabolite of LC,i.e.,3-phenoxybenzoic acid,was produced and further degraded.In a cotton-planted soil spiked with 10 mg kg^(-1)LC,the consortium degraded 91.8%LC,as well as improving the agronomic parameters of the cotton plants.In a nutshell,the consortium CHST was found to be a promising candidate for the remediation of LC contamination at the point source.展开更多
文摘Different Ziegler-Natta catalysts were employed to polymerize ethylene. To investigate the influences of reaction parameters, namely Al/Ti molar ratio, hydrogen and processing parameters, i.e. ethylene pressure and temperature, a Taguchi experimental design was worked out. An L27 orthogonal array was chosen to take the above-mentioned parameters and relevant interactions into account. Response surface method was the tool used to analyze the experimental design results. Al/Ti, ethylene pressure and temperature were selected as experimental design factors, and catalyst activity and polymerization yield were the response parameters. Increasing pressure, due to an increment in monomer accessibility, and rising Al/Ti, because of higher reduction in the catalysts, cause an increase in both polymerization yield and catalyst activity. Nonetheless, a higher temperature, thanks to reducing ethylene solubility in the slurry medium and partially catalyst destruction, lead to a reduction in both response parameters. A synergistic effect was also observed between temperature and pressure. All catalyst activities will reduce in the presence of hydrogen. Molecular weight also shows a decline in the presence of hydrogen as a transfer agent. However, the polydispersity index remains approximately intact. Using SEM, various morphologies, owing to different catalyst morphologies, were seen for the polyethylene.
文摘Residual stresses can reduce the reliability of plastic injection molding parts. This work is an attempt to model the residual stresses as a function of injection molding parameters. More stress is placed on reducing the number of input factors and to include all possible interactions. For this purpose, two-stage experimentation is suggested: a factor screening stage and Response Surface optimization stage. In screening stage Taguchi 3 level experimental design is used to classify the input parameters as significant and non-significant factors. Eight input variables were classified into 3 non-significant and 5 significant factors using this screening stage. Thus for the Response Surface optimization stage: instead of doing 160 experiments in Central Composite, 56 are only needed after the screening stage in half Central Composite Design. The best subset and regression model fitting tools in addition to model verification using randomly selected input setting were used to select a model for predicting residual stresses with a verified Root Mean Square Error (RSME) of nearly 0.93 MPa.
文摘In this work,MIL-101,a metal organic framework,has been synthesized and examined in the adsorptive denitrogenation process.Due to the importance of adsorption capacity and selectivity,the effects of synthesis parameters including metal type,reagent ratio,time and temperature on the MIL-101 performance were investigated by measuring quinoline(QUI)separation from iso-octane.The optimum conditions were determined using a Taguchi experimental design and the multiresponse optimization(multivariate statistical)method.Based on the arithmetic mean of normalized QUI adsorption capacity and QUI/dibenzothiophene(DBT)selectivity,as the objective function,the optimum value of synthesis parameters were found to be manganese as metal type in the structure,180°C for synthesis temperature,15h for synthesis time and 1.00 for reagent molar ratio.Under these conditions,QUI adsorption capacity and QUI/DBT selectivity were 19.3 mg-N/g-Ads.and 24.6,respectively.Accordingly,the arithmetic mean between normalized values of these measured parameters was equal to 1.10,which is in good agreement with the predicted value.The MIL-101 produced under optimum conditions was characterized by determining its specific surface area,X-ray powder diffraction patterns and Fourier transform infrared spectroscopy.Finally,isotherm and kinetic studies indicate that the Langmuir isotherm and pseudo-first-order model can successfully describe the experimental data.
文摘Pure greenish-blue cobalt chromite(Co Cr/_2O_4) nanoparticles with narrow particle range of 4.1±1.9nm and surface area of 78.2 m2·g-1were synthesized through mixed chelates thermolysis of corresponding metals using 2-Mercaptopyridine N-oxide sodium salt as chelating agent. During the thermolysis procedure,high amount of gases were emitted that led to the formation of nanoparticles with high surface area. The product was characterized by TGA, DTG, XRD, TEM, SEM, LLS, BET and chemical analysis. Design of experiments was performed to fulfill the two levels L_4 Taguchi design. It was found that the temperature and time of thermolysis process have significant effect on the particle size reduction. The Oxidation of trichloroethylene was carried out over Co Cr_2O_4 nanocrystallite. Catalytic activity analysis revealed that the synthesis Co Cr_2O_4 possesses high catalytic activity for this process.
基金supported by the Higher Education Commission(HEC),Pakistan(No.NRPU 9570)。
文摘Extensive use of lambda-cyhalothrin(LC)for agricultural and domestic pest control leads to the accumulation of its residues in soil and water,which poses a serious threat to the environment.Remediation of LC at the point source is the most effective way to avoid its spread and harmful effects.Therefore,this study was planned to investigate the potential of indigenously isolated bacteria for the remediation of LC in cotton-vegetated soils.Three potent LC-degrading bacteria,Brucella intermedia Halol,Alcaligenes faecalis CH1S,and Aquamicrobium terrae CH1T,were isolated from a pyrethroid-contaminated soil.A consortium CHST comprising these three strains was found to exhibit a higher potential for LC degradation as compared to the individual strains.The degradation of LC by CHST was optimized for four varying factors,i.e.,pH,inoculum density(ID),carbon source(CS),and initial pesticide(i.e.,LC)concentration(PC),by applying Taguchi design of experiment.The contributions of these factors to the biodegradation of LC were found to be in the order of pH>CS>PC>ID.The enhanced degradation of LC(84%)was attained at pH 7.0 in minimum salt medium containing 10 mg L^(-1)LC and 3%inoculum.The consortium CHST was also augmented in sterilized and unsterilized soil microcosms at three PCs,i.e.,2,5,and 10 mg kg^(-1).After 21 d of incubation,complete LC degradation was achieved at 2 mg kg^(-1)PC in sterilized as well as unsterilized soil,whereas at higher PCs,the extent of degradation was comparatively less.At PC of 5 mg kg^(-1),88%and 96%LC degradation were observed in sterilized and unsterilized soils,respectively,compared to 79%and90%degradation at 10 mg kg^(-1),respectively.During biodegradation,the major metabolite of LC,i.e.,3-phenoxybenzoic acid,was produced and further degraded.In a cotton-planted soil spiked with 10 mg kg^(-1)LC,the consortium degraded 91.8%LC,as well as improving the agronomic parameters of the cotton plants.In a nutshell,the consortium CHST was found to be a promising candidate for the remediation of LC contamination at the point source.
