Papers by Ashraf Muhammad
Chemistry & Biodiversity, 2012
Samples of the aerial parts of Thymus broussonetii, T. ciliatus, T. leptobotrys, T. maroccanus, T... more Samples of the aerial parts of Thymus broussonetii, T. ciliatus, T. leptobotrys, T. maroccanus, T. pallidus, T. satureioides, and T. serpyllum collected from different natural regions in southern and south-western Morocco were analyzed for their qualitative and quantitative essential oil profiles. In total, 46 compounds, representing more than 99% of the oils, were characterized. Monoterpenes, both hydrocarbons (12.9-58.0%) and oxygenated monoterpenes (38.8-81.1%), were the principal classes of compounds for most of the thyme species studied. Cluster analysis allowed the classification of the species into three main groups: a carvacrol group (Group I), comprising the species T. maroccanus and T. leptobotrys, a linalyl acetate and (E)-nerolidol group (Group II), represented by T. serpyllum, and a thymol and/or carvacrol, γ-terpinene, and p-cymene group (Group III), composed of T. satureioides, T. broussonetii, T. ciliatus, and T. pallidus. The essential oils were screened for their antioxidant and anticandidal activities. The data showed that the oils obtained from T. leptobotrys and T. maroccanus (carvacrol group) possessed the highest antioxidant activities as assessed by the determination of the DPPH free radical-scavenging ability and the ferric-reducing potential. The anticandidal assays indicated that the highest activity was noticed for the essential oil isolated from T. leptobotrys.
Muhammad Ashraf, 2022
Dumping dairy manure in surroundings of confined animal feeding operations (CAFO) is an extensive... more Dumping dairy manure in surroundings of confined animal feeding operations (CAFO) is an extensively implemented malpractice. This exercise poses serious environmental complications along with global warming, water, and air pollution. This study aims to explore and compare the pyrolytic conversion of the dairy manure of two common milch animals (Cow and Buffalo) of CAFO through detailed kinetic and thermodynamic analysis. Physicochemical characterization indicated an analogy in samples with close values of volatile contents (63 % ± 0.22), elemental carbon contents (37 % ± 0.24) and heating values (16 MJ/Kg ± 0.0.95). Subsequently, under non-isothermal and inert thermogravimetric analysis (TGA), the thermal degradations kinetics were studied through Isoconversional methods and Model fitting methods. TGA recorded major conversion (≈ 50 %) during active pyrolysis zone in temperature range of 240 to 360⁰C for both sample with similar patterns. The average activation energy (Ea) determined by the Isoconversional methods were 143.84 and 137.74 kJ mol − 1 , with corresponding frequency factor (A) values of 4.19 × 10 26 and 2.47 × 10 23 min − 1 for cow manure (CM) and buffalo manure (BM), respectively. The kinetic compensation effect described strong linear relationship between the Ln(A) and Ea with comparable isokinetic temperatures. Master plot indicated that decomposition was driven by order-based reaction (F n) with transition to Diffusion (D n) models. The empirical modeling by Sestak and Berggren's model showed an excellent correlation with the experimental data. Finally, thermodynamic analysis indicated a non-spontaneous and endothermic trend in entire conversion. Overall, the study suggested comparable thermo-kinetics of CM and BM pyrolysis.
Biomass Conversion and Biorefinery, 2021
The over reliance on fossil fuels for power generation has resulted in an alarming depletion of p... more The over reliance on fossil fuels for power generation has resulted in an alarming depletion of petrochemical crude oil reserves, that also is the cause of elevated greenhouse gas effects. Biomass resources are considered potential fuels for the future on account of their renewable and carbon-neutral features. This study presents the physicochemical characteristics and pyrolysis behavior of a novel biomass Ficus natalensis barkcloth (FNB). Physicochemical characterization indicated that the FNB has 74.4% volatile matter contents, a higher heating value (HHV) of 13.8 MJ/kg, and it has 67% cellulose as its main chemical constituent. Thermogravimetric analysis (TGA) showed that major decomposition occurred at the core devolatization (235℃ to 410 ℃) under inert thermal degradation. Model-free and model-fitting kinetic methods were applied to TGA data to compute the kinetics triplet for FNB biomass. The average activation energy (E a) of the FNB pyrolysis process was determined to be 168 kJ/mol. The compensation effects between pre-exponential factor (A) and E a detected a rise in collision intensity for the pyrolysis of FNB at high heating rates. The Criado master plot results showed that the pyrolysis of FNB followed first-order reaction (F 1) mechanism. The thermodynamic parameters, such as change in enthalpy (ΔH), Gibbs free energy (ΔG), and entropy (ΔS), were also calculated and compared with kinetics parameters to evaluate the evolution of thermal degradation. Physiochemical and thermo-kinetic analysis of FBN revealed its comparable bioenergy potential with established biomasses.
Partial oxidation of dried cattle dung cannot achieve temperatures necessary for endothermic redu... more Partial oxidation of dried cattle dung cannot achieve temperatures necessary for endothermic reduction reactions in autothermal gasification, because of lower fixed carbon (FC) content and higher volatility of feedstock. This study comprehends a simplified and viable allothermal gasification of cattle dung in an integrated system. Solar photovoltaic (PV) induced air gasification of dried cattle dung was carried out in a small-scale tubular furnace, equipped with controlled operating systems. Characterization of cattle dung showed that it had a higher heating value (HHV) of 16 ± 0.01 MJ/kg, volatile content of 63% ± 1%wt, and FC of 15 ± 1%wt. Gasification was performed at variable power supply levels (W) of the solar PV system and corresponding temperatures with varying air-fuel equivalence ratios (ER = 0.21-0.3). The optimal fractions of hydrogen (13.26 ± 0.95%), carbon monoxide (14.39 ± 1.2%), and methane (2.15 ± 0.5%) were achieved at 1100 W, 800 °C, and 0.26 ER. The HHV of syngas was 4.89 ± 0.4% MJ/Nm 3 at optimal process conditions with an average yield of 2.20 ± 0.001 m 3 /kg. Based on the solid residue and thermal conversion efficiencies, 82.67 ± 1.2% of biomass was converted to syngas and 66.70 ± 2% of biomass energy was extracted through gasification. This research provides a firm and novel foundation for a long term, efficient and cost-effective hybrid gasification system capable of handling a wide range of high-volume biowaste feedstock, particularly cattle dung.
The pyrolysis of the cattle dung was quantified using the Coats-Redfern method. The thermogravime... more The pyrolysis of the cattle dung was quantified using the Coats-Redfern method. The thermogravimetric and derivate curves (TG/DTG) divided the decomposition into three stages. Apart from stage I (dehydration), stage II exhibited higher thermal decomposition rate in the temperature range of 220-380 °C whereas, in stage III (390-690 °C), a lower decomposition rate was noticed. Comparative kinetic parameters for solid-state reactions showed that first-order reaction (F 1) had the highest value of regression coefficient (R 2) in both stages. In stage II, the Power-law (P 3/2), reaction order-2 and 3 (F 2 and F 3), and diffusion models (D 1 and D 2) produced higher activation energy (E a) values, while 3-diffusion (D 3) produced the lowest E a value. However, in subsequent stage III, only two reaction mechanisms (F 1 and F 2) were estimated with significant R 2 value and F 2 showed higher E a value. The simulated TG/DTG validated that decomposition of cattle dung was best described by F 1 in both stages. In addition to kinetic analysis through Coats-Redfern method, mass change at 20 °C/min was also processed by employing artificial neural network (ANN) and the model was validated with a strong R 2 value and lower mean squared error (MSE). In thermodynamic analysis, the increase in the heating rate decreased ∆G and increased ∆S for the whole process with stable ∆H. This study provides the theoretical and practical guideline for the utilization of cattle dung as a potential energy source.
The study investigates the non-isothermal thermogravimetric analysis of cattle manure at varied h... more The study investigates the non-isothermal thermogravimetric analysis of cattle manure at varied heating rates to compare the kinetic and thermodynamic behaviors of cattle manure in N 2 and air atmospheres. The Thermogravimetric (TG) curves indicated that the decomposition of the manure can be divided into three different regions. Exclusive of stage I (dehydration), the activation energy (Ea) values of stage II (devolatilization) for all model-free methods varied between 144-270 and 32-227 kJ/mol in pyrolysis and combustion respectively. While in stage III, Ea values varied in ranges of 49-336 kJ/mol and 71-136 kJ/mol for pyrolysis (carbonation) and combustion (char burning), respectively. The overall average Ea for the pyrolysis (≈146 kJ/mol) is higher than the combustion process (≈127 kJ/mol). The variation in the values of frequency factor "A" also indicated the complexity of both processes. Pyrolysis followed overall 2-Diffusion (D 2) reaction models, while combustion followed 3-Power law (P 3) and reaction Order-1 (O 1) in stage II and III respectively. The thermodynamic study was also conducted to evaluate the important parameters, change in Enthalpy change (ΔH), Gibbs free energy (ΔG), and Entropy (ΔS).
The over reliance on fossil fuels for power generation has resulted in an alarming depletion of p... more The over reliance on fossil fuels for power generation has resulted in an alarming depletion of petrochemical crude oil reserves, that also is the cause of elevated greenhouse gas effects. Biomass resources are considered potential fuels for the future on account of their renewable and carbon-neutral features. This study presents the physicochemical characteristics and pyrolysis behavior of a novel biomass Ficus natalensis barkcloth (FNB). Physicochemical characterization indicated that the FNB has 74.4% volatile matter contents, a higher heating value (HHV) of 13.8 MJ/kg, and it has 67% cellulose as its main chemical constituent. Thermogravimetric analysis (TGA) showed that major decomposition occurred at the core devolatization (235℃ to 410 ℃) under inert thermal degradation. Model-free and model-fitting kinetic methods were applied to TGA data to compute the kinetics triplet for FNB biomass. The average activation energy (E a) of the FNB pyrolysis process was determined to be 168 kJ/mol. The compensation effects between pre-exponential factor (A) and E a detected a rise in collision intensity for the pyrolysis of FNB at high heating rates. The Criado master plot results showed that the pyrolysis of FNB followed first-order reaction (F 1) mechanism. The thermodynamic parameters, such as change in enthalpy (ΔH), Gibbs free energy (ΔG), and entropy (ΔS), were also calculated and compared with kinetics parameters to evaluate the evolution of thermal degradation. Physiochemical and thermo-kinetic analysis of FBN revealed its comparable bioenergy potential with established biomasses.
Biomass Conversion and Biorefinery, 2021
The pyrolysis of the cattle dung was quantified using the Coats-Redfern method. The thermogravime... more The pyrolysis of the cattle dung was quantified using the Coats-Redfern method. The thermogravimetric and derivate curves
(TG/DTG) divided the decomposition into three stages. Apart from stage I (dehydration), stage II exhibited higher thermal
decomposition rate in the temperature range of 220–380 °C whereas, in stage III (390–690 °C), a lower decomposition rate
was noticed. Comparative kinetic parameters for solid-state reactions showed that first-order reaction (F1) had the highest
value of regression coefficient (R2) in both stages. In stage II, the Power-law (P3/2), reaction order-2 and 3 (F2 and F3), and
diffusion models (D1 and D2) produced higher activation energy (Ea) values, while 3-diffusion (D3) produced the lowest Ea
value. However, in subsequent stage III, only two reaction mechanisms (F1 and F2) were estimated with significant R2 value
and F
2 showed higher Ea value. The simulated TG/DTG validated that decomposition of cattle dung was best described by
F
1 in both stages. In addition to kinetic analysis through Coats-Redfern method, mass change at 20 °C/min was also processed by employing artificial neural network (ANN) and the model was validated with a strong R2 value and lower mean
squared error (MSE). In thermodynamic analysis, the increase in the heating rate decreased ∆G and increased ∆S for the
whole process with stable ∆H. This study provides the theoretical and practical guideline for the utilization of cattle dung
as a potential energy source.
Case Studies in Thermal Engineering
The study investigates the non-isothermal thermogravimetric analysis of cattle manure at varied h... more The study investigates the non-isothermal thermogravimetric analysis of cattle manure at varied heating rates to compare the kinetic and thermodynamic behaviors of cattle manure in N 2 and air atmospheres. The Thermogravimetric (TG) curves indicated that the decomposition of the manure can be divided into three different regions. Exclusive of stage I (dehydration), the activation energy (Ea) values of stage II (devolatilization) for all model-free methods varied between 144-270 and 32-227 kJ/mol in pyrolysis and combustion respectively. While in stage III, Ea values varied in ranges of 49-336 kJ/mol and 71-136 kJ/mol for pyrolysis (carbonation) and combustion (char burning), respectively. The overall average Ea for the pyrolysis (≈146 kJ/mol) is higher than the combustion process (≈127 kJ/mol). The variation in the values of frequency factor "A" also indicated the complexity of both processes. Pyrolysis followed overall 2-Diffusion (D 2) reaction models, while combustion followed 3-Power law (P 3) and reaction Order-1 (O 1) in stage II and III respectively. The thermodynamic study was also conducted to evaluate the important parameters, change in Enthalpy change (ΔH), Gibbs free energy (ΔG), and Entropy (ΔS).
The over reliance on fossil fuels for power generation has resulted in an alarming depletion of p... more The over reliance on fossil fuels for power generation has resulted in an alarming depletion of petrochemical crude oil reserves, that also is the cause of elevated greenhouse gas effects. Biomass resources are considered potential fuels for the future on account of their renewable and carbon-neutral features. This study presents the physicochemical characteristics and pyrolysis behavior of a novel biomass Ficus natalensis barkcloth (FNB). Physicochemical characterization indicated that the FNB has 74.4% volatile matter contents, a higher heating value (HHV) of 13.8 MJ/kg, and it has 67% cellulose as its main chemical constituent. Thermogravimetric analysis (TGA) showed that major decomposition occurred at the core devolatization (235℃ to 410 ℃) under inert thermal degradation. Model-free and model-fitting kinetic methods were applied to TGA data to compute the kinetics triplet for FNB biomass. The average activation energy (E a) of the FNB pyrolysis process was determined to be 168 kJ/mol. The compensation effects between pre-exponential factor (A) and E a detected a rise in collision intensity for the pyrolysis of FNB at high heating rates. The Criado master plot results showed that the pyrolysis of FNB followed first-order reaction (F 1) mechanism. The thermodynamic parameters, such as change in enthalpy (ΔH), Gibbs free energy (ΔG), and entropy (ΔS), were also calculated and compared with kinetics parameters to evaluate the evolution of thermal degradation. Physiochemical and thermo-kinetic analysis of FBN revealed its comparable bioenergy potential with established biomasses.
The study investigates the non-isothermal thermogravimetric analysis of cattle manure at varied h... more The study investigates the non-isothermal thermogravimetric analysis of cattle manure at varied heating rates to compare the kinetic and thermodynamic behaviors of cattle manure in N 2 and air atmospheres. The Thermogravimetric (TG) curves indicated that the decomposition of the manure can be divided into three different regions. Exclusive of stage I (dehydration), the activation energy (Ea) values of stage II (devolatilization) for all model-free methods varied between 144-270 and 32-227 kJ/mol in pyrolysis and combustion respectively. While in stage III, Ea values varied in ranges of 49-336 kJ/mol and 71-136 kJ/mol for pyrolysis (carbonation) and combustion (char burning), respectively. The overall average Ea for the pyrolysis (≈146 kJ/mol) is higher than the combustion process (≈127 kJ/mol). The variation in the values of frequency factor "A" also indicated the complexity of both processes. Pyrolysis followed overall 2-Diffusion (D 2) reaction models, while combustion followed 3-Power law (P 3) and reaction Order-1 (O 1) in stage II and III respectively. The thermodynamic study was also conducted to evaluate the important parameters, change in Enthalpy change (ΔH), Gibbs free energy (ΔG), and Entropy (ΔS).
The pyrolysis of the cattle dung was quantified using the Coats-Redfern method. The thermogravime... more The pyrolysis of the cattle dung was quantified using the Coats-Redfern method. The thermogravimetric and derivate curves (TG/DTG) divided the decomposition into three stages. Apart from stage I (dehydration), stage II exhibited higher thermal decomposition rate in the temperature range of 220-380 °C whereas, in stage III (390-690 °C), a lower decomposition rate was noticed. Comparative kinetic parameters for solid-state reactions showed that first-order reaction (F 1) had the highest value of regression coefficient (R 2) in both stages. In stage II, the Power-law (P 3/2), reaction order-2 and 3 (F 2 and F 3), and diffusion models (D 1 and D 2) produced higher activation energy (E a) values, while 3-diffusion (D 3) produced the lowest E a value. However, in subsequent stage III, only two reaction mechanisms (F 1 and F 2) were estimated with significant R 2 value and F 2 showed higher E a value. The simulated TG/DTG validated that decomposition of cattle dung was best described by F 1 in both stages. In addition to kinetic analysis through Coats-Redfern method, mass change at 20 °C/min was also processed by employing artificial neural network (ANN) and the model was validated with a strong R 2 value and lower mean squared error (MSE). In thermodynamic analysis, the increase in the heating rate decreased ∆G and increased ∆S for the whole process with stable ∆H. This study provides the theoretical and practical guideline for the utilization of cattle dung as a potential energy source.
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Papers by Ashraf Muhammad
(TG/DTG) divided the decomposition into three stages. Apart from stage I (dehydration), stage II exhibited higher thermal
decomposition rate in the temperature range of 220–380 °C whereas, in stage III (390–690 °C), a lower decomposition rate
was noticed. Comparative kinetic parameters for solid-state reactions showed that first-order reaction (F1) had the highest
value of regression coefficient (R2) in both stages. In stage II, the Power-law (P3/2), reaction order-2 and 3 (F2 and F3), and
diffusion models (D1 and D2) produced higher activation energy (Ea) values, while 3-diffusion (D3) produced the lowest Ea
value. However, in subsequent stage III, only two reaction mechanisms (F1 and F2) were estimated with significant R2 value
and F
2 showed higher Ea value. The simulated TG/DTG validated that decomposition of cattle dung was best described by
F
1 in both stages. In addition to kinetic analysis through Coats-Redfern method, mass change at 20 °C/min was also processed by employing artificial neural network (ANN) and the model was validated with a strong R2 value and lower mean
squared error (MSE). In thermodynamic analysis, the increase in the heating rate decreased ∆G and increased ∆S for the
whole process with stable ∆H. This study provides the theoretical and practical guideline for the utilization of cattle dung
as a potential energy source.
(TG/DTG) divided the decomposition into three stages. Apart from stage I (dehydration), stage II exhibited higher thermal
decomposition rate in the temperature range of 220–380 °C whereas, in stage III (390–690 °C), a lower decomposition rate
was noticed. Comparative kinetic parameters for solid-state reactions showed that first-order reaction (F1) had the highest
value of regression coefficient (R2) in both stages. In stage II, the Power-law (P3/2), reaction order-2 and 3 (F2 and F3), and
diffusion models (D1 and D2) produced higher activation energy (Ea) values, while 3-diffusion (D3) produced the lowest Ea
value. However, in subsequent stage III, only two reaction mechanisms (F1 and F2) were estimated with significant R2 value
and F
2 showed higher Ea value. The simulated TG/DTG validated that decomposition of cattle dung was best described by
F
1 in both stages. In addition to kinetic analysis through Coats-Redfern method, mass change at 20 °C/min was also processed by employing artificial neural network (ANN) and the model was validated with a strong R2 value and lower mean
squared error (MSE). In thermodynamic analysis, the increase in the heating rate decreased ∆G and increased ∆S for the
whole process with stable ∆H. This study provides the theoretical and practical guideline for the utilization of cattle dung
as a potential energy source.