scholarly journals Adsorption of Carbon Dioxide, Methane, and Nitrogen Gases onto ZIF Compounds with Zinc, Cobalt, and Zinc/Cobalt Metal Centers

2019 ◽  
Vol 2019 ◽  
pp. 1-11
Author(s):  
Ahmed Awadallah-F ◽  
Febrian Hillman ◽  
Shaheen A. Al-Muhtaseb ◽  
Hae-Kwon Jeong
Keyword(s):  
Carbon Dioxide ◽  
Equilibrium Adsorption ◽  
Cobalt Metal ◽  
Transfer Coefficients ◽  
Metal Centers ◽  
Equilibrium Behavior ◽  
Three Samples ◽  
Different Temperatures ◽  
Adsorption Quantity ◽  
Dual Site

ZIF-8, Co-ZIF-8, and Zn/Co-ZIF-8 are utilized in adsorbing nitrogen (N2), methane (CH4), and carbon dioxide (CO2) gases at temperatures between 25 and 55°C and pressures up to ~1 MPa. Equilibrium adsorption isotherms and adsorption kinetics are studied. The dual-site Langmuir equation is employed to correlate the nonisothermal adsorption equilibrium behavior. Generally, N2 showed the lowest equilibrium adsorption quantity on the three samples, whereas CO2 showed the highest equilibrium adsorption capacity. Amid the ZIF samples, the biggest adsorption quantities of N2 and CH4 were onto Zn/Co-ZIF-8, whereas the highest adsorption quantity of CO2 was on ZIF-8. The isosteric heats of adsorbing these gases on ZIF-8, Co-ZIF-8, and Zn/Co-ZIF-8 were examined. Moreover, the overall mass transfer coefficients of adsorption at different temperatures were investigated.

scholarly journals The Effect of the Temperature and Moisture to the Permeation Properties of PEO-Based Membranes for Carbon-Dioxide Separation

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2053
Author(s):  
Dragutin Nedeljkovic
Keyword(s):  
Carbon Dioxide ◽  
Partial Pressure ◽  
Carbon Dioxide Emission ◽  
Combustion Products ◽  
Mixed Matrix Membranes ◽  
Mixed Matrix Membrane ◽  
Mixed Matrix ◽  
Gas Treatment ◽  
Carbon Dioxide Separation ◽  
Different Temperatures

An increased demand for energy in recent decades has caused an increase in the emissions of combustion products, among which carbon-dioxide is the most harmful. As carbon-dioxide induces negative environmental effects, like global warming and the greenhouse effect, a decrease of the carbon-dioxide emission has emerged as one of the most urgent tasks in engineering. In this work, the possibility for the application of the polymer-based, dense, mixed matrix membranes for flue gas treatment was tested. The task was to test a potential decrease in the permeability and selectivity of a mixed-matrix membrane in the presence of moisture and at elevated temperature. Membranes are based on two different poly(ethylene oxide)-based polymers filled with two different zeolite powders (ITR and IWS). An additive of detergent type was added to improve the contact properties between the zeolite and polymer matrix. The measurements were performed at three different temperatures (30, 60, and 90 °C) under wet conditions, with partial pressure of the water equal to the vapor pressure of the water at the given temperature. The permeability of carbon-dioxide, hydrogen, nitrogen, and oxygen was measured, and the selectivity of the carbon-dioxide versus other gases was determined. Obtained results have shown that an increase of temperature and partial pressure of the vapor slightly increase both the selectivity and permeability of the synthesized membranes. It was also shown that the addition of the zeolite powder increases the permeability of carbon-dioxide while maintaining the selectivity, compared to hydrogen, oxygen, and nitrogen.

Metal-organic frameworks for electrochemical reduction of carbon dioxide: The role of metal centers

2020 ◽  
Vol 40 ◽  
pp. 156-170 ◽  
Author(s):  
Ping Shao ◽  
Luocai Yi ◽  
Shumei Chen ◽  
Tianhua Zhou ◽  
Jian Zhang
Keyword(s):  
Carbon Dioxide ◽  
Electrochemical Reduction ◽  
Metal Organic Frameworks ◽  
Metal Centers ◽  
Metal Organic

scholarly journals Kinetics and thermodynamic properties related to the drying of 'Cabacinha' pepper fruits

2016 ◽  
Vol 20 (2) ◽  
pp. 174-180 ◽  
Author(s):  
Hellismar W. da Silva ◽  
Renato S. Rodovalho ◽  
Marya F. Velasco ◽  
Camila F. Silva ◽  
Luís S. R. Vale
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Free Energy ◽  
Thermodynamic Properties ◽  
Gibbs Free Energy ◽  
Removal Rate ◽  
Effective Diffusion ◽  
Drying Time ◽  
Three Samples ◽  
Different Temperatures

ABSTRACT The objective of this study was to determine and model the drying kinetics of 'Cabacinha' pepper fruits at different temperatures of the drying air, as well as obtain the thermodynamic properties involved in the drying process of the product. Drying was carried out under controlled conductions of temperature (60, 70, 80, 90 and 100 °C) using three samples of 130 g of fruit, which were weighed periodically until constant mass. The experimental data were adjusted to different mathematical models often used in the representation of fruit drying. Effective diffusion coefficients, calculated from the mathematical model of liquid diffusion, were used to obtain activation energy, enthalpy, entropy and Gibbs free energy. The Midilli model showed the best fit to the experimental data of drying of 'Cabacinha' pepper fruits. The increase in drying temperature promoted an increase in water removal rate, effective diffusion coefficient and Gibbs free energy, besides a reduction in fruit drying time and in the values of entropy and enthalpy. The activation energy for the drying of pepper fruits was 36.09 kJ mol-1.

Comparison of Existing Supercritical Carbon Dioxide Heat Transfer Correlations for Horizontal and Vertical Bare Tubes

2012 ◽  
Author(s):  
Prabu Surendran ◽  
Sahil Gupta ◽  
Tiberiu Preda ◽  
Igor Pioro
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Wall Temperature ◽  
Statistical Error ◽  
Heat Fluxes ◽  
Transfer Coefficients ◽  
Bulk Fluid ◽  
Heat Transfer Correlations ◽  
Supercritical Carbon

This paper presents a thorough analysis of ability of various heat transfer correlations to predict wall temperatures and Heat Transfer Coefficients (HTCs) against experiments on internal forced-convective heat transfer to supercritical carbon dioxide conducted by Koppel [1], He [2], Kim [3] and Bae [4]. It should be noted the Koppel dataset was taken from a paper which used the Koppel data but was not written by Koppel. All experiments were completed in bare tubes with diameters from 0.948 mm to 9 mm for horizontal and vertical configurations. The datasets contain a total of 1573 wall temperature points with pressures ranging from 7.58 to 9.59 MPa, mass fluxes of 400 to 1641 kg/m2s and heat fluxes from 20 to 225 kW/m2. The main objective of the study was to compare several correlations and select the best of them in predicting HTC and wall temperature values for supercritical carbon dioxide. This study will be beneficial for analyzing heat exchangers involving supercritical carbon dioxide, and for verifying scaling parameters between CO2 and other fluids. In addition, supercritical carbon dioxide’s use as a modeling fluid is necessary as the costs of experiments are lower than supercritical water. The datasets were compiled and calculations were performed to find HTCs and wall and bulk-fluid temperatures using existing correlations. Calculated results were compared with the experimental ones. The correlations used were Mokry et al. [5], Swenson et al. [6] and a set of new correlations presented in Gutpa et al. [7]. Statistical error calculations were performed are presented in the paper.

EFFECTS OF QUANTUM CONFINEMENT ON LOW FREQUENCY NOISE IN δ-DOPED GaAs STRUCTURES GROWN BY MBE

2002 ◽  
Vol 02 (01) ◽  
pp. L37-L45
Author(s):  
X. Y. CHEN ◽  
P. M. KOENRAAD
Keyword(s):  
Quantum Confinement ◽  
Low Frequency ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Free Carriers ◽  
In Doping ◽  
Three Samples ◽  
Different Temperatures ◽  
Lower Magnitude ◽  
Different Thickness

Low frequency noise (LFN) was measured in δ-doped GaAs structures in which the free carriers are confined to a 2-dimensional plane. Three samples grown at different temperatures, resulting in doping layers of a different thickness, are used to study the effects of quantum confinement on the LFN. We observed both 1/f noise and generation-recombination noise components. We find that a stronger quantum confinement results in a bigger Hall mobility and a lower magnitude of the 1/f noise.

scholarly journals Determination of Oleanolic and Ursolic Acids inHedyotis diffusaUsing Hyphenated Ultrasound-Assisted Supercritical Carbon Dioxide Extraction and Chromatography

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Ming-Chi Wei ◽  
Yu-Chiao Yang ◽  
Show-Jen Hong
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
High Performance ◽  
Extraction Yield ◽  
Extraction Time ◽  
Different Temperatures ◽  
Ultrasound Assisted ◽  
High Concentrations ◽  
Static Extraction ◽  
Supercritical Carbon

Oleanolic acid (OA) and ursolic acid (UA) were extracted fromHedyotis diffusausing a hyphenated procedure of ultrasound-assisted and supercritical carbon dioxide (HSC–CO2) extraction at different temperatures, pressures, cosolvent percentages, and SC–CO2flow rates. The results indicated that these parameters significantly affected the extraction yield. The maximal yields of OA (0.917 mg/g of dry plant) and UA (3.540 mg/g of dry plant) were obtained at a dynamic extraction time of 110 min, a static extraction time of 15 min, 28.2 MPa, and 56°C with a 12.5% (v/v) cosolvent (ethanol/water = 82/18, v/v) and SC–CO2flowing at 2.3 mL/min (STP). The extracted yields were then analyzed by high performance liquid chromatography (HPLC) to quantify the OA and UA. The present findings revealed thatH. diffusais a potential source of OA and UA. In addition, using the hyphenated procedure for extraction is a promising and alternative process for recovering OA and UA fromH. diffusaat high concentrations.

scholarly journals Quality and shelf life of packaged fresh sliced mushrooms stored at two different temperatures

2008 ◽  
Vol 15 (4) ◽  
pp. 414 ◽  
Author(s):  
E. GONZÁLEZ-FANDOS ◽  
A. SIMON JIMENES ◽  
V. TOBAR PARDO
Keyword(s):  
Carbon Dioxide ◽  
Shelf Life ◽  
Agaricus Bisporus ◽  
Microbiological Quality ◽  
Air Atmosphere ◽  
Pvc Film ◽  
Different Temperatures ◽  
Aerobic And Anaerobic ◽  
Quality And Shelf Life

The sensory and microbiological quality of sliced mushrooms (Agaricus bisporus L.) packaged in films of perforated and non-perforated PVC and stored at 3 and 9ºC, was studied. The carbon dioxide and oxygen content inside the packages, colour, weight loss, sensory attributes, mesophiles, Pseudomonas, Enterobacteriaceae, aerobic and anaerobic spore formers were determined. The atmosphere generated with the perforated PVC film was similar to that of air atmosphere at 3 or 9ºC. T.he non-perforated PVC film generated inside the packages CO2 : O2 concentrations of 3.4% : 8.1% at 3ºC and CO2 : O2 concentrations of 4.5% : 0.15% at 9ºC. Browning of mushrooms was lower at 3 than at 9ºC. The quality of sliced mushrooms packaged in perforated PVC and stored at 3ºC was adequate after 9 days. However, at 9ºC, the slice deformation and brown blotches incidence were severe after 9 days. The atmosphere generated with non-perforated PVC inhibited aerobic microorganism growth compared to mushrooms packaged in perforated PVC. At 3ºC, the shelf life of mushrooms packaged in non perforated PVC was around 13 days. However, the extremely low O2 atmospheres generated at 9ºC was accompanied by off-odours and growth of anaerobic spore formers, although the appearance of sliced mushrooms was acceptable.;

Adsorption Research of Polymer on Oil Sands in Qidongyi Block of Xinjiang Conglomerate Reservoir

2014 ◽  
Vol 580-583 ◽  
pp. 2518-2523
Author(s):  
Xiao Bin Nie ◽  
Ying Guo ◽  
Qing Xiang Lou ◽  
Wei Dong Liu ◽  
Ling Hui Sun ◽  
...  
Keyword(s):  
Oil Sands ◽  
Adsorption Process ◽  
Slow Growth ◽  
Stable State ◽  
Polymer Flooding ◽  
Equilibrium Adsorption ◽  
Negative Effects ◽  
Polymer Molecules ◽  
Maximum Value ◽  
Adsorption Quantity

In the process of polymer flooding in porous media, polymer was detained due to interactions between surface adsorption and polymer molecules, and this could lead to negative effects on oil displacement. For polymer adsorption in Xinjiang conglomerate reservoir, HPLC analysis was adopted to study the static and dynamic laws. Results have showed that the adsorption process could be divided into 3 stages: rapid growth, slow growth and stable state. With the loss of polymer molecular weight, equilibrium adsorption quantity reduces gradually. The adsorption amount is different for the same polymer on four types of oil sands. For equilibrium adsorption, the maximum value is argillaceous sandstone, followed by conglomeratic sandstone.The third is argillaceous gravel, and the minimum is sand gravel. For polymer flooding in conglomerate cores, the dynamic retention amount of seriate conglomerate is much greater than that of fine particle conglomerate. These data have provided reference for project design of polymer flooding in conglomerate reservoir.

Investigation of Buoyancy Effects in Asymmetrically Heated Near-Critical Flows of Carbon Dioxide in Horizontal Microchannels Using Infrared Thermography

2021 ◽  
Author(s):  
Lindsey V. Randle ◽  
Brian M. Fronk
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Heat Flux ◽  
Infrared Thermography ◽  
Test Section ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Parallel Microchannels

Abstract In this study, we use infrared thermography to calculate local heat transfer coefficients of top and bottom heated flows of near-critical carbon dioxide in an array of parallel microchannels. These data are used to evaluate the relative importance of buoyancy for different flow arrangements. A Joule heated thin wall made of Inconel 718 applies a uniform heat flux either above or below the horizontal flow. A Torlon PAI test section consists of three parallel microchannels with a hydraulic diameter of 923 μm. The reduced inlet temperature (TR = 1.006) and reduced pressure (PR = 1.03) are held constant. For each heater orientation, the mass flux (520 kgm−2s−2 ≤ G ≤ 800 kgm−2s−2) and heat flux (4.7 Wcm−2 ≤ q″ ≤ 11.1 Wcm−2) are varied. A 2D resistance network analysis method calculates the bulk temperatures and heat transfer coefficients. In this analysis, we divide the test section into approximately 250 segments along the stream-wise direction. We then calculate the bulk temperatures using the enthalpy from the upstream segment, the heat flux in a segment, and the pressure. To isolate the effect of buoyancy, we screen the data to omit conditions where flow acceleration may be important or where relaminarization may occur. In the developed region of the channel, there was a 10 to 15 percent reduction of the local heat transfer coefficients for the upward heating mode compared to downward heating with the same mass and heat fluxes. Thus buoyancy effects should be considered when developing correlations for these types of flow.

scholarly journals Modified Dual-Site Langmuir Adsorption Equilibrium Models from A GCMC Molecular Simulation

2020 ◽  
Vol 10 (4) ◽  
pp. 1311
Author(s):  
Junchao Wang ◽  
Yongjie Wei ◽  
Zhengfei Ma
Keyword(s):  
Molecular Simulation ◽  
Adsorption Energy ◽  
Pressure Swing Adsorption ◽  
Adsorption Equilibrium ◽  
Equilibrium Data ◽  
Different Temperatures ◽  
Adsorption Energies ◽  
Pressure Swing ◽  
Adsorption Equilibrium Data ◽  
Dual Site

In the modern industrial separation process, the pressure swing adsorption technology is widely used to separate and purify gases due to its low energy consumption, low cost, convenience, reliability, and environmental benignity. The basic elements of the design and application of the pressure swing adsorption process are adsorption isotherms at different temperatures for adsorbents. The dual-site Langmuir (DSL) adsorption equilibrium model is the mostly used model; however, this model is based on the assumption that the adsorption energy on the surface of an adsorbent is uniform and remains unchanged. Here, a grand canonical Monte Carlo (GCMC) molecular simulation was used to calculate the CO2 adsorption equilibrium on MIL-101 (Cr) at 298 K. MIL-101 (Cr) was chosen, as it has more a general pore structure with three different pores. The calculation results showed that the adsorption energies with different adsorption pressures fitted a normal distribution and the relationship of the average adsorption energies, E with pressures had a linear form described as: E = aP + c. With this relationship, the parameter b = k·exp(E/RT) in the DSL model was modified to b = k·exp((aP + c)/RT), and the modified DSL model (M-DSL) was used to correlate the adsorption equilibrium data on CO2-MIL-101 (Cr), C2H4-HHPAC, CH4-BPL, and CO2-H-Mordenite, showing better correlations than those of the DSL model. We also extended the parameter qm in the M-DSL model with the equation qm = k1 + k2T to adsorption equilibrium data for different temperatures. The obtained model (M-TDSL) was checked with the abovementioned adsorption equilibrium systems. The fitting results also indicated that the M-TDSL model could be used to improve the correlation of adsorption equilibrium data for different temperatures. The linear relationship between the average adsorption energy and adsorption pressure could be further tested in other adsorption equilibrium models to determine its universality.

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