scholarly journals Titanium-based phenoxy-imine catalyst for selective ethylene trimerization: effect of temperature on the activity, selectivity and properties of polymeric side products

2020 ◽  
Vol 10 (6) ◽  
pp. 1602-1608
Author(s):  
Astrid Cordier ◽  
Pierre-Alain Breuil ◽  
Typhène Michel ◽  
Lionel Magna ◽  
Hélène Olivier-Bourbigou ◽  
...  
Keyword(s):  
Kinetic Studies ◽  
Effect Of Temperature ◽  
Titanium Catalyst ◽  
Thermal Switch ◽  
Ethylene Trimerization

A thermal switch of selectivity for a phenoxy-imine titanium catalyst was studied by combining kinetic studies and a “polymer-to-catalyst” approach.

Solid phase sorption of microamount of Hg(II) onto 1-(2-thiazolylazo)-2-naphthol (TAN) loaded polyurethane foam

2005 ◽  
Vol 93 (3) ◽  
Author(s):  
Muhammad M. Saeed ◽  
Sadia Z. Bajwa ◽  
Muhammad S. Ansari ◽  
Riaz Ahmed
Keyword(s):  
Free Energy ◽  
Metal Ions ◽  
Adsorption Process ◽  
Solid Phase ◽  
Kinetic Studies ◽  
Environmental Pollutant ◽  
Intraparticle Diffusion ◽  
Effect Of Temperature ◽  
Loading Capacity ◽  
Optimum Ph

SummaryMercury is a toxic environmental pollutant. A method has been developed to remove these metal ions by preconcentrating onto 1-(2-thiazolylazo)-2-naphthol (TAN) loaded polyurethane (PUR) foam that proves an excellent sorbent for these metal ions. The accumulation conditions are optimized with respect to pH, shaking time, loading capacity and adsorbent weight. The optimum pH for sorption was found to be 7, which is close to the natural water. Optimum shaking time for Hg(II) is 30 min. The kinetic studies indicate that sorption occurs through intraparticle diffusion process. Classical adsorption isotherms are applied to determine the nature of sorption. The sorption free energy value indicates that adsorption process is chemisorption. Effect of temperature has been used to compute the values of Δ

Kinetische Untersuchungen und Charakterisierung der solubilisierten Oestradiol-bzw. Testosteron-"sensitiven" 17 β-HSD-Aktivitäten / Microsome-Associated 17β-Hydroxysteroid Dehydrogenases of Human Placenta, II Kinetic Studies and Characterization of the Solubilized Estradioland Testosterone-“Sensitive” 17β-HSD-Activities

1975 ◽  
Vol 30 (1-2) ◽  
pp. 17-24 ◽  
Author(s):  
Kunhard Pollow ◽  
Wilfried Runge ◽  
Barbara Pollow
Keyword(s):  
Steroid Hormones ◽  
Human Placenta ◽  
Hydrogen Transfer ◽  
Kinetic Studies ◽  
Integrated System ◽  
The Other ◽  
Effect Of Temperature ◽  
Ph Optimum ◽  
Hydroxysteroid Dehydrogenases ◽  
Estradiol 17Β

Abstract Detailed enzyme kinetic parameters of the reactions catalyzed by the two 17β-hydroxysteroid dehydrogenases (17β-HSD), which were solubilized from the microsomes of human placenta by treatment with phospholipase A, followed by enrichment and separation were determined. Both enzymes are strictly substrate specific. The most active substrate of one of the 17β-HSD (fraction A) is estradiol-17β, the other 17β-HSD (fraction B) is sensitive to testosterone. Both NAD and NADP can serve as hydrogen transferring coenzymes, the latter giving about one-third of the initial rate of the former. With respect to the influence of temperature, different buffers and pH values, Michaelis constants [Km] with estradiol-17β and testosterone as substrates, the solubilized and separated microsomal 17β-HSD behave like those isolated from the cytoplasmic fraction. The two 17β-HSD, after solubilization from the microsomal fraction of human placenta, enrichment and separation from each other, show only a little activity for the transfer of hydrogen between C17 of estradiol-17β and C17 of androstenedione. On the other hand, intact microsomes and an integrated system prepared by recombination of the 17β-enzymes by preincubation in phosphate buffer are able to catalyse very actively the transfer of hydrogen between estradiol-17β and androstenedione. The effect of temperature and time on the recombination of the two enriched and separated microsomal enzyme activities and the determination of the pH-optimum of the hydrogen transfer reaction are described. Finally it is proposed that the hydrogen transfer between steroid hormones represents an aspect of the true reaction mechanism of steroid hormones: Steroid hormones function as hydrogen transferring coenzymes by forming part of a chain of hydrogen carriers.

scholarly journals The effect of temperature on the individual stages of the hydrolysis of non-specific-p-nitrophenol esters by α-chymotrypsin

1977 ◽  
Vol 161 (1) ◽  
pp. 83-92 ◽  
Author(s):  
P A Adams ◽  
E R Swart
Keyword(s):  
Kinetic Studies ◽  
Detailed Comparison ◽  
Effect Of Temperature ◽  
Thermal Transitions ◽  
Arrhenius Plots ◽  
Ph Values ◽  
The Individual ◽  
Hydrolysis Of

Precise studies were performed on the effect of temperature on the rate and equilibrium parameters characterizing the individual stages of the alpha-chymotrypsin-catalysed hydrolysis of non-specific p-nitrophenol esters at pH 7.40 and 8.50. At both pH values the results indicate that a sharp kinetic anomaly is observed in Arrhenius plots of these parameters for the binding and acylation stages of the process, but not for the deacylation stage. Detailed comparison with other kinetic studies was made, and a comparison with thermal transitions observed in alpha-chymotrypsin by using physical techniques was attempted. A detailed discussion of possible causes of the anomalies is given.

scholarly journals Comparative Study on the Adsorption Kinetics and Thermodynamics of Metal Ions onto Acid Activated Low Cost Pandanus Carbon

2007 ◽  
Vol 4 (2) ◽  
pp. 238-254 ◽  
Author(s):  
R. Sudha ◽  
K. Kalpana ◽  
T. Rajachandrasekar ◽  
S. Arivoli
Keyword(s):  
Metal Ions ◽  
Metal Ion ◽  
Low Cost ◽  
Freundlich Isotherm ◽  
Kinetic Studies ◽  
Ion Concentration ◽  
Effect Of Temperature ◽  
Ferrous Ions ◽  
Sem Images ◽  
Operating Variables

Batch experiments were carried out for the sorption of Copper and Ferrous ions onto acid activated carbon prepared. The operating variables studied were initial metal ion concentration, pH, and temperature and contact time. The equilibrium data were fitted to the Langmuir and Freundlich isotherm equations. From this adsorption efficiency, adsorption energy, adsorption capacity, intensity of adsorption and dimensionless separation factor were calculated. From the kinetic studies the rate constant values for the adsorption process was calculated. From the effect of temperature thermodynamic parameters like ΔG°, ΔH°, and ΔS° were calculated. The mechanism of adsorption for metal ions onto carbon was investigated by using the experimental results and confirmed by FT- IR, XRD and SEM images.

scholarly journals Removal of ammonium from fish farms by biochar obtained from rice straw: Isotherm and kinetic studies for ammonium adsorption

2018 ◽  
Vol 36 (5-6) ◽  
pp. 1294-1309 ◽  
Author(s):  
Ahmed Khalil ◽  
Nikolai Sergeevich ◽  
Vita Borisova
Keyword(s):  
Rice Straw ◽  
Removal Efficiency ◽  
Kinetic Studies ◽  
Effect Of Temperature ◽  
Fish Farms ◽  
Isothermal Adsorption ◽  
Ammonium Adsorption ◽  
Pseudo Second Order ◽  
Water Pollutant ◽  
Physical And Chemical

Ammonium is a water pollutant that harms the environment, particularly fisheries. Rice straw is also an economic waste of rice, with millions of tons produced per year around the world. In this paper, physical and chemical procedures for the modification of rice straw were studied. The kinetic and isothermal adsorption trends were investigated, including the ammonium removal efficiency, the contact time of the adsorbent, the amount of adsorbent, and the initial concentration of NH4+. The effect of temperature and pH on the adsorption process was discussed. The removal efficiency of NH4+ recorded 43, 53.7, and 69.5%, with maximum adsorption values of 2.9, 3.5, and 4.5 mg/g at temperatures of 25 ± 5, 35 ± 5, and 45 ± 5°C, respectively, at pH 7.5. The biochar obtained from rice follows the pseudo-second-order equation for ammonium adsorption kinetics (R2 = 0.98). The adsorption isotherm follows Freundlich’s model (R2 = 0.99) and Langmuir’s model (R2 = 0.98).

Kinetic studies on the pyrrole–Cr-based Chevron-Phillips ethylene trimerization catalyst system

2014 ◽  
Vol 481 ◽  
pp. 39-48 ◽  
Author(s):  
Siyang Tang ◽  
Zhen Liu ◽  
Xiaowei Yan ◽  
Ning Li ◽  
Ruihua Cheng ◽  
...  
Keyword(s):  
Kinetic Studies ◽  
Catalyst System ◽  
Ethylene Trimerization

Enhanced Adsorption for P-Chlorophenol by Ammonia Modified Activated Carbon

2013 ◽  
Vol 663 ◽  
pp. 807-812
Author(s):  
Guo Yang ◽  
Yan Jie ◽  
Hu Yang ◽  
Chen Hong Zhang
Keyword(s):  
Activated Carbon ◽  
Adsorption Capacity ◽  
Functional Groups ◽  
Kinetic Studies ◽  
Effect Of Temperature ◽  
Order Kinetic ◽  
Surface Functional Groups ◽  
Order Kinetic Model ◽  
Pseudo Second Order ◽  
Enhanced Adsorption

To investigate the influence of N-containing surface functional groups on adsorption capacity of AC, the activated carbon (AC) was modified with ammonia gas at 650 °C. Surface functional groups were quantitatively analyzing by Boehm titration. The effect of temperature on adsorption capacity suggested higher temperature is favourable. The influence of pH indicated the adsorption was favorable in acidic solution. The adsorption isotherms were fitted by Langmuir model and Freundlich model. Moreover, kinetic studies showed the adsorption of phenol onto adsorbents was followed by pseudo-second-order kinetic model. The adsorption capacity of ammoniated AC for p-chlorophenol was greatly improved.

scholarly journals Study of Nickel Extraction Process from Spent Catalysts with Hydrochloric Acid Solution: Effect of Temperature and Kinetics Study

2021 ◽  
Vol 3 (2) ◽  
pp. 161-170
Author(s):  
Kevin Cleary Wanta ◽  
◽  
Ivanna Crecentia Narulita Simanungkalit ◽  
Elsha Pamida Bahri ◽  
Ratna Frida Susanti ◽  
...  
Keyword(s):  
Hydrochloric Acid ◽  
Kinetic Studies ◽  
Extraction Process ◽  
Core Model ◽  
Effect Of Temperature ◽  
Average Error ◽  
Shrinking Core Model ◽  
Nickel Extraction ◽  
Shrinking Core ◽  
Spent Catalysts

As one of the hazardous and toxic solid wastes, spent catalysts need to be treated before the waste is discharged into the environment. One of the substances that need to be removed from the spent catalysts is the heavy metal ions and/or compounds contained therein. The method that can be applied is the extraction method using an acid solvent. In this study, the extraction process was carried out on spent catalysts samples from PT. Petrokimia Gresik. The focus of the study is on nickel extraction by varying the temperature in the range of 30–85 oC. A 1 M hydrochloric acid (HCl) solution was used as a solvent while the extraction process was 120 minutes. The experimental results show that the maximum nickel recovery of 14.70% can be achieved at a temperature of 85 oC. Kinetic studies were carried out using two kinetic models. The results of both models evaluation on the research data show that the lump model gives better results than the shrinking core model. The average error percentage of the lump model is smaller than the shrinking core model. It indicates that the extraction process was controlled by the diffusion step through the ash layer in the solid and chemical reactions simultaneously.

Nucleation of Disorder in Fe3Al Alloys

1967 ◽  
Vol 25 ◽  
pp. 312-313
Author(s):  
P. R. Swann ◽  
W. R. Duff ◽  
R. M. Fisher
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Annealing Temperature ◽  
Antiphase Domain ◽  
Effect Of Temperature ◽  
Domain Structures ◽  
Transmission Electron ◽  
Domain Boundaries ◽  
Higher Temperature ◽  
The One

Recently we have investigated the phase equilibria and antiphase domain structures of Fe-Al alloys containing from 18 to 50 at.% Al by transmission electron microscopy and Mössbauer techniques. This study has revealed that none of the published phase diagrams are correct, although the one proposed by Rimlinger agrees most closely with our results to be published separately. In this paper observations by transmission electron microscopy relating to the nucleation of disorder in Fe-24% Al will be described. Figure 1 shows the structure after heating this alloy to 776.6°C and quenching. The white areas are B2 micro-domains corresponding to regions of disorder which form at the annealing temperature and re-order during the quench. By examining specimens heated in a temperature gradient of 2°C/cm it is possible to determine the effect of temperature on the disordering reaction very precisely. It was found that disorder begins at existing antiphase domain boundaries but that at a slightly higher temperature (1°C) it also occurs by homogeneous nucleation within the domains. A small (∼ .01°C) further increase in temperature caused these micro-domains to completely fill the specimen.

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