Chemical Engineering Journal (13858947)405
The side reactions play an evident role in the selectivity of propylene in methanol to propylene (MTP) process. Recycling by-products such as C4 and C5 hydrocarbon cuts is an effective way to utilize these hydrocarbons and to improve the propylene selectivity. So, the aim of this study was to present a kinetic model for the MTP process over the H-ZSM-5 (Si/Al = 200) catalyst in the presence of co-reaction of methanol and C4-C5 olefin mixture based on the Langmuir-Hinshelwood theory. This model was established on a comprehensive mechanism including methanol conversion, methylation, cracking, hydrogenation, dehydrogenation, and oligomerization reactions. The Response Surface Methodology based on Central Composite Design was applied to evaluate the impact of C4= (5–16 wt%) and C5= (2–9 wt%) mass fraction, WHSV (1.93–7.73 h−1), and temperature (455–485 °C) on the product distribution. It was found that the co-feeding of C4-C5 olefin mixture with methanol can enhance the propylene selectivity up to 73% by controlling the operating conditions. The excellent agreement between the model prediction and experimental data shows that the proposed kinetic model accurately describes the product distribution, and is applicable to this process. © 2020 Elsevier B.V.
Applied Physics A: Materials Science and Processing (14320630)127(10)
Metronidazole (MTZ) is an antibacterial drug, which is frequently detected in wastewater, resulting in pathogen-resistance and mutagenicity. Therefore, MTZ removal is a serious challenge. In this research work, the visible-light-driven Z-scheme CuWO4/Bi2S3 heterojunction with optimized weight percentage (7%wt) was evaluated for MTZ degradation under LED radiation in batch and continues reactor. The effect of operational factors such as MTZ concentration (10–30 ppm), catalyst dose (0.4–1 mg/L), pH (3–9) and illumination time (90–150 min) on MTZ degradation efficiency was investigated through response surface methodology (RSM). The optimum values of the operating parameters were found to be as: irradiation time = 150 min, pH = 3, MTZ concentration of 10 ppm and catalyst dose = 0.7 g/L. The utmost degradation efficiencies were obtained 79% and 84%, respectively, in batch and continues flow mode at the optimum conditions. Thereafter, the effect of immobilization of the binary composite on FTO was studied at the obtained optimum conditions. The effect of temperature and light intensity on photocatalytic performance was also investigated, and the optimal values were found to be 25 °C and 400 W/m2, respectively. The mineralization of MTZ was investigated through TOC removal rates with the maximum value of 61.32%. The gas chromatography-mass spectrometry analysis was used to detect the photodegradation intermediates. The kinetic study of MTZ degradation by the binary composite followed the pseudo-first order by the reaction rate of 2 times greater than pristine Bi2S3. The main active species were found to be hydroxyl radical and superoxide by the trapping test method. The binary heterojunction demonstrated high durability and stability after five cycles. This work recommends a promising heterojunction for MTZ photodegradation. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature.
Materials Science in Semiconductor Processing (13698001)127
A novel Z-scheme MnWO4/Bi2S3 heterojunction was constructed by a hydrothermal method for the first time. The structure, morphology and optical absorption characterization of photocatalysts were comprehensively identified. The photocatalytic performance of catalysts was investigated by the cephalexin (CFX) and metronidazole (MTZ) degradation under LED irradiation. The degradation efficiency of binary composite was promoted compared to pure MnWO4 and Bi2S3. The enhanced performance was assigned to the Z-scheme construction, leading the broad visible-light adsorption spectrum, superior redox potential as well as impressive separation and reduced recombination of photo-induced charge carriers. The effect of catalyst dose, temperature and light intensity on photodegradation activity was studied. The effect of inorganic ions was investigated in order to simulate the actual situation. The optimal values of catalyst dose, temperature and illumination intensity were found to be 1.2 g/L, 25 °C and 400 W/m2, respectively. The maximum degradation efficiencies of 74.5% and 79.8% were achieved for CFX and MTZ, respectively. TOC removal analysis was applied to measure the mineralization of CFX (46%) and MTZ (65.2%). The degradation intermediates were distinguished by using the gas chromatography/mass spectrometry (GC/MS) analysis. The kinetic investigation of photodegradation followed the first order kinetic for both drugs. The novel binary composite depicted high stability after six cycles. The trapping experiments detected the hydroxyl (OH.) and superoxide (O2.) radicals as the main active species. This research revealed a novel Z-scheme photocatalyst as a promising strategy in order to remove antibiotics. © 2021
Asia-Pacific Journal of Chemical Engineering (19322135)15(6)
The present study aims to conduct a systematic assessment of Al-SBA-15 as the aluminum-substituted mesoporous catalyst for raw methanol dehydration to dimethyl ether (MTD). The catalysts are synthesized by varying the pretreatment variables (pH of the preparation and Si/Al ratio), the posttreatment variable (steaming time), and by the addition of aluminophosphate as the binder. The experimental design and the analysis of the results, especially the relation of characterization results and reactor performance, are performed by the optimal response surface method in Design-Expert software. The prepared micro-mesoporous catalyst exhibits an excellent activity, stability, and DME selectivity; therefore, it can be introduced as an efficient catalyst for raw methanol dehydration. © 2020 Curtin University and John Wiley & Sons, Ltd.
Biofuels (17597277)11(1)pp. 93-99
In the present study, enzymatic biodiesel production from low-cost, non-edible crude Eruca sativa oil was investigated. Candida rugosa lipase (CRL), a commercially promising biocatalyst in different industries, was used. Although this source of lipase has been reported as unsuitable for biodiesel production from non-edible oil, in this study, it was attempted to use this enzyme for production of fatty acid methyl esters (FAME) from Eruca sativa oil in a solvent-free system. For the first time, the effects of pre-hydrolysis and pH on the yield of biodiesel were evaluated. Afterward, the four most commonly reported influential parameters were analyzed with the use of response surface methodology (RSM). It was observed that pre-hydrolysis had a significant effect on biodiesel conversion due to the mechanism of enzymatic biodiesel production. Deionized water was more efficient in comparison with phosphate buffer with different pH values. According to the RSM analysis, water content and temperature have a highly significant effect on biodiesel production. Methanol-to-oil ratio and enzyme amounts were also significant factors in FAME production. The optimum methanol-to-oil ratio, enzyme amount, water content, and temperature for achieving high conversion was found to be 3:1, 5 mg, 40%, and 21 °C, respectively. © 2017, © 2017 Informa UK Limited, trading as Taylor & Francis Group.
Chemosphere (00456535)251
A novel double Z-scheme CuWO4/Bi2S3/ZIF67 ternary heterostructure was synthesized through hydrothermal method. The catalysts were characterized by XRD, FTIR, SEM, EDX, BET, TEM, PL, and UV–vis DRS analyses. The degradations of Metronidazole (MTZ) and Cephalexin (CFX) antibiotics by ternary catalyst were investigated in the batch and continuous slurry photoreactor under LED illumination. The ternary heterostructure exhibited a remarkable improvement in photoactivity compared with CuWO4/Bi2S3, and pristine ZIF67. Indeed, higher surface area, photo-stability, bandgap suppressing as well as better charge separation based on the dual Z-scheme structure caused the enhancement. The optimum values of operating parameters were obtained by the central composite design as: catalyst dose = 0.3 g/L, pH = 7, illumination time = 80 min, and 20 ppm initial concentration of antibiotic. The maximum degradation efficiencies by the new ternary heterostructure were 95.6% and 90.1%, respectively for MTZ and CFX at optimum conditions in the continuous flow mode. Maximum total organic carbon (TOC) removal rates were 83.2% and 74% for MTZ and CFX, respectively. The degradations by ternary composite followed the first-order kinetic, by reaction rate of 9 times, 5.5 times, and 4 times higher than that obtained by Bi2S3, ZIF67, and the binary CuWO4/Bi2S3, respectively. The influences of temperature and light intensity were explored, revealing 25 °C and 400 W/m2 as the optimum values. The new ternary heterostructure demonstrated excellent reusability and chemical stability after six cycles. The dominant active species were explored by trapping tests, indicating OH. free radicals as the most primary oxidant. © 2020
Applied Energy (18729118)267
Retrofitting or reducing heat consumption in existing Heat Exchanger Networks can be done by set of modifications which is termed “bridge”. A bridge links heat outlets to hot utility users. The most complicated step in identification of the economical bridges, is the determination of the optimum routes. The “Energy Transfer Diagram” and a few modifications on bridge method are among the recent efforts for the better identification of the bridges. Though the internal exchangers in the initial network participate as the “transferring interface or chain rings along the bridges”, the role and the characteristics of their participation has not dealt with clearly and quantitatively in any of previous works. This paper presents “Heat Flow Diagram” as a new graphical tool and also an analyzing algorithm, to improve bridges identification in retrofit analysis method. The role of internal exchangers as the transferring interface and the limiting factors affects its transferring capacity is conceptually and quantitatively analyzed for the first time. Subsequently several illustrative examples ‘covering different situations and clarifying concepts of new retrofitting method’ were illustrated. Heat integration of a Methanol plant analyzed with three different method to compare with our new suggestion; resulted in 18.8%, 79.2% and 98.9% heat recovery. © 2020 Elsevier Ltd
Nokhodiyan isfahani, N.,
Bahadori, M.,
Marandi, A.,
Tangestaninejad, S.,
Moghadam, M.,
Mirkhani, V.,
Beheshti dehkordi, M.,
Afzali, N. Industrial and Engineering Chemistry Research (15205045)59(26)pp. 11970-11978
Hierarchical H-form ZSM-5 (h-ZSM-5) was synthesized and successfully functionalized with imidazolium-based ionic liquids for solvent-free insertion of carbon dioxide to epoxides and synthesis of cyclic carbonate. Tetrapropyl ammonium hydroxide and polyurethane foam were used as soft and hard templates, respectively, to introduce mesoporosity in the structure. The synthesized hierarchical H-form ZSM-5 provided a large surface area for covalent attachment of imidazolium-based ionic liquids to produce h-ZSM-5-IL. The successful synthesis of the new catalyst was confirmed by X-ray diffraction, Fourier transform infrared spectroscopy, the Brunauer-Emmett-Teller method, and scanning electron microscopy and utilized for the insertion of carbon dioxide to epoxides and production of cyclic carbonate under solvent-free conditions. High conversion and selectivity for the synthesis of cyclic carbonate and recovery of the catalyst for five consecutive times without loss of catalytic activity are the advantages of this newly synthesized catalyst. Copyright © 2020 American Chemical Society.
Journal of Photochemistry and Photobiology A: Chemistry (18732666)394
Herein, a new visible-light driven CuWO4/Bi2S3 Z-scheme composite was synthesized by a hydrothermal method. The photocatalyst was specified by XRD, FT-IR, EDX, SEM, TEM, HRTEM, BET, UV–vis DRS and PL analyses. The prepared heterojunction greatly improved the CFX photodegradation performance compared with pristine Bi2S3 and CuWO4 under LED illumination. The enhanced degradation efficiency was assigned to the higher visible-light adsorption spectrum, higher redox ability, effective separation and reduced recombination of photoinduced electron-hole pairs due to the Z-scheme construction. The point of zero charge (pzc) pH for the binary CuWO4/Bi2S3 heterojunction was calculated as 6.2 through pH drift method. The maximum degradation efficiencies in batch (76 %) and continoues flow (81.7 %) reactor were achieved at optimum values of the operating parameters as follows: irridation time = 150 min, CFX concentration = 10 ppm, pH = 3 and 0.8 g/L of catalyst dose. The optimum values for temperature and light intensity were 25 °C and 400 W/m2, respectively. According to the kinetic studies, the photocatalytic degradation of CFX followed the first order kinetic. The new Z-scheme composite indicated desirable reusability and chemical stability after five cycles. According to the trapping tests, the Z-schematic construction was proposed for the photocatalytic mechanism and superoxide and hydroxyl radicals were found to be the main active species in the degradation process. This work recommended a novel Z-scheme heterojunction as a new idea for CFX removal. © 2020
Renewable Energy (09601481)140pp. 104-110
In the present study, a novel two-phase enzymatic membrane bioreactor (TP-EMR) was developed for the enzymatic biodiesel production from crude Eruca sativa oil. Commercial poly acrylonitrile (PAN) ultrafiltration membrane was examined with a molecular weight cut offs (MWCO) of 30 and 100 kilo Dalton (kDa). Using enzymatic membrane bioreactor with hydrophilic PAN membrane increased the yield of biodiesel production. In this regards, PAN membrane with a MWCO of 100 kDa gave the better results. The inactivation and inhibition effects of methanol and produced glycerol were reduced with the use of membrane bioreactor. It was found that by methanol feeding via aqueous phase, methanol has been penetrated across membrane pores to the organic phase. Afterwards, methanol has reacted with oil at the interface of the membrane at the presence of Candida rugosa lipase (CRL) as a biocatalyst. Produced glycerol, which surrounded the CRL, could be removed from organic phase and conveyed to the aqueous phase to reduce the inhibitory effect of glycerol on the activity of CRL. The yield of about 100% from Eruca sativa oil was achieved in TP-EMR with PAN 100 and organic phase flow rate of 40 ml/min along with 40% initial water content in organic phase. © 2019
Gharibi kharaji, A.,
Beheshti dehkordi, M.,
Repke, J.,
Tangestani-nejad, S.,
Görke, O.,
Godini, H.R. Reaction Kinetics, Mechanisms and Catalysis (18785204)127(1)pp. 375-390
In this study, ZSM-5 was synthesized via the hydrothermal method and then extruded using aluminophosphate as a binder. Before using it as a catalyst in methanol to propylene reaction, it was tried to eliminate the undesired contributions of the used binder by hydrothermal post- treatment. The experimental design and the analysis of the results, especially the relation of characterization results and reactor performance, are performed by optimal response surface method in Design Expert Software. The effects of the exposing time and the temperature during the steaming procedure on the catalytic characteristics and the performance of this system were investigated for two different average particle sizes (75 and 150 µm) of this catalyst. The results of the post-treatment represent the main dependency on the catalyst particle size, where the catalyst with smaller particle size showed lower methanol conversion and selectivity towards light olefins. It was concluded that an increase in the particle size of the catalyst intensifies the transport restrictions within the zeolite structure, which consequently increases the intra-particle residence time for production of higher hydrocarbons and then facilitates their cracking in order to produce more light olefins. This needs to be taken into consideration while synthesizing the catalyst for large-scale application. © 2019, Akadémiai Kiadó, Budapest, Hungary.
Energy (18736785)164pp. 1114-1134
This paper applies an extend energy - exergy analysis as a strategy for evaluating the performance of different types of distillation columns in ethylene production process by using industrial data. Regarding to the limitation and deficiency of energy – exergy combination, a new method named exergy destruction level (EDL) and conceptual diagram based on equipment target value is proposed for process equipment with pressure and chemical composition changes. The effects of different operational parameters on the component separation are evaluated by sensitivity analysis. Eventually response surface methodology (RSM) and artificial intelligence (DE) method are developed for optimization of the chemical plant. Comparing obtained results from ethylene plant optimization by using RSM and DE, it was found that annual profit percentage with DE method is 61.6% more than RSM method. Also, results of optimization showed that the most effective operating parameters consist of feed stream temperature, boil-up ratio, reflux ratio, column pressure and feed stage. It was observed that utilities and refrigeration cycle consumption work have been declined significantly by using DE optimizer and EDL analysis (12.6% and 11.6%) compared to RSM optimizer and exergy analysis (11.9% and 4.8%). It is obvious that, EDL analysis and DE method expedite process optimization and provide more precise analysis than conventional energy-exergy analysis. © 2018 Elsevier Ltd
Chemical Engineering and Processing - Process Intensification (02552701)123pp. 158-167
Distillation with vapor recompression (VRC) has received much attention in recent years as a technology for enhancing energy efficiency of distillation systems. Various configurations of vapor recompression were proposed in previous studies. A novel system is proposed that utilizes the same concepts, distillation without hot utilities (DWHU). In a DWHU system, water at normal temperatures is the sole source of thermal energy for distillation. In this paper, a set of novel DWHU configurations are proposed and their energy and economic performances are presented and compared with previous systems such as conventional distillation column and VRC. Seven configurations (including five DWHU configurations) were studied for separation of a propylene/propane mixture. From both energy and economic points of view, it has been revealed that the newly proposed DWHU configuration can outperform conventional distillation, VRC and base DWHU systems. © 2017 Elsevier B.V.
International Journal Of Industrial Chemistry (22285547)9(1)pp. 75-84
Vapor recompression and bottom flashing are among the developed technologies for enhancing energy efficiency of distillation processes. In this paper, a novel configuration of bottom flashing system is proposed for enhancing energy efficiency of dual columns such as direct distillation sequences. The system is designed to operate between two distillation columns. The proposed system engages two separate distillation columns, both of which can be wide boiling systems. The system incorporates two interacting bottom flashing systems that engage the two distillation columns through heat transfer from the top product of the second column to the bottom product of the first column which in turn results in elimination/reduction of utility requirements of condenser of the second column along with reboiler of the first column. Based on the results of this study, compared to conventional direct sequence distillation, 40.3% reduction in energy requirements and 20.7% reduction total annual costs of the process can be obtained through application of the proposed system. © 2017, The Author(s).
Chemical Engineering Science (00092509)181pp. 19-35
In this paper, various configurations of vapor recompression and bottom flashing systems were developed. The systems were developed based on direct sequence, indirect sequence, Petlyuk and side stripper designs. This research was performed with three main aims. First aim was to investigate possibility of enhancing energy and economic performance of complex three-product distillation systems via implementation of vapor recompression and bottom flashing. Second aim was to shed light on differences in potentials of vapor recompression and bottom flashing systems in energy and costs savings of three-product distillation schemes. Third aim was to name the best configuration of three-product separation schemes from economic and energy points of view. Twelve configurations were designed. Energy and costs requirements of each configuration were evaluated and compared to each other. Based on the presented results, implementation of vapor recompression and bottom flashing systems can lead to better economic performance of complex three-product distillation systems. In case study presented in this work, application of vapor recompression and bottom flashing enhanced performance of direct sequence, indirect sequence, Petlyuk and side stripper designs. Equivalent work requirements of base direct sequence separation system was 5.59 MW. Based on the obtained results, considering energy requirements, Side stripper and Petlyuk arrangements are the best options for separation of the three-product system with equivalent work savings of 27.6 and 23.5%, respectively. Considering equivalent mechanical work of the systems, the highest savings was obtained in Side stripper with VRC heat pump (71.3% saving). It is shown that the most economically attractive configuration is Petlyuk with bottom flashing with total annual costs (TAC) saving of 43.4% (compared to 9.58 mUSD/year TAC of the base case), while the best performances of vapor recompression systems were obtained on Petlyuk and side stripper designs with TAC savings of 37.4 and 31.0%, respectively. © 2018 Elsevier Ltd
RSC Advances (20462069)8(9)pp. 4561-4570
Novel methods have been developed for lipase immobilization on poly acrylonitrile (PAN) membranes to increase the activity and stability of the immobilized lipase. In this study, poly acrylonitrile (PAN) membranes were aminated and then activated by glutaraldehyde or epichlorohydrine to be used for enzyme immobilization. In the other approach, magnetic nanoparticles (MNPs) which were functionalized with trichlorotriazine (TCT) or glutaraldehyde (GA) were attached to the membrane surface to prepare the nanocomposite membranes named TCT-MNP@PAN & GA-MNP@PAN membranes. Candida rugosa lipase (CRL) was covalently immobilized on this activated nanocomposite membrane. Nanoparticles and nanocomposite membranes were characterized with various techniques such as SEM, TEM, XRD, FTIR, FTIR-ATR, AFM, contact angle goniometry and surface free energy measurement. The evidence of immobilization was also done by FTIR-ATR, enzyme activity, and loading efficiency. It was found that the activity of immobilized lipase on GA and TCT functionalized NCPAN membrane were about 50% and 31% higher than that immobilized on GA-activated PAN membrane. The kinetic parameters of enzymatic membranes showed the better conformation of the lipase enzyme immobilized on the TCT-MNP@PAN membrane. The presented enzymatic nanocomposite membranes are easy to prepare with low cost and are good candidates for use in membrane bioreactors. © The Royal Society of Chemistry 2018.
Applied Energy (18729118)211pp. 1261-1281
Various configurations of vapor recompression (VRC), bottoms flashing (BF) and external heat pump (EHP) for energy and/or costs savings were proposed in literature. Based on published studies, the best configuration for having the highest performance among the proposed separation systems cannot be easily identified by process engineers as the basis for comparison were not the same. In this study, a comparative study was carried out among the most recent configurations of VRC, BF, EHP and two previously proposed ideas for thermal enhancement of VRC. Based on the schemes and ideas presented by previous researchers, 18 heat pump assisted configurations were designed for separation of propylene from a propylene-propane mixture. The highest total energy saving of 93.8% was identified upon application of a configuration, designed based on heat recuperation ideas. Based on the results of current research, the BF exhibited the best economic performance among the basic heat pump systems, while the external heat pump system exhibited the worst energy and economic performance compared to the other designs. The base conventional distillation column was found to have the lowest capital costs (15.6 mUSD), while a heat recuperated VRC system had the lowest annual operating costs (3.04 mUSD) and total annual costs (7.63 mUSD). © 2017
Energy (18736785)140pp. 1059-1073
Pinch Technology has been widely adopted and considered to be one of the most successful techniques in process energy integration. But according to limitation and defect of pinch analysis in heat exchanger retrofit, a new conceptual diagram is proposed for super-ambient and sub-ambient temperature process. This diagram is based on heat flow rate as a function of temperature. By using this diagram, it can be achieve to the concepts such as: 1- retrofit of the HEN for energy saving, 2- the best location of hot and cold utility, 3- The actual amount of required hot and cold utility. Composite curve, the grand composite curve and the energy transfer diagram have been constructed for analysis of the HEN of a methanol to propylene plant. In this novel design it was attempted to improve the HEN's efficiency of MTP process and get the maximum economic return. Annual profit percentage reach to 13.2% by improving HEN via bridge method. Results showed that utilities consumption have been decreased significantly in the novel design by bridge method (about 9.3%) to pinch analysis (5.0%). Finally, it can be said, bridge analysis provides more detail about heat savings modifications, than traditional pinch analysis. © 2017 Elsevier Ltd
Energy (18736785)125pp. 449-458
Application of vapor recompression systems can result in enhanced energy efficiency and reduced energy requirements of distillation systems. In vapor recompression systems, temperature and dew point temperature of the top product of the column are increased through compression. By transferring heat from top to bottoms product, required boil up and reflux streams for the column are provided. In this paper, a new system is proposed for efficient stripping of sour water based on vapor recompression. Ammonia and H2S are the contaminants of sour water. Initially, based on a certain specifications of products, a sour water stripping system is implemented. A novel processing system is then developed and simulated to reduce utility requirements. The two processing systems are economically evaluated by Aspen Economic Evaluation software. There are 89.0% and 83.7% reduction of hot and cold utility requirements for the proposed system in comparison to the base processing system. However, the new processing system requires new equipment such as compressor and corresponding mechanical work that increases its capital and operating costs in comparison to the base case. However, the results indicate that the proposed system results in reduction of 11.4% of total annual costs and 14.9% of operating costs. © 2017 Elsevier Ltd
Chemical Engineering and Processing - Process Intensification (02552701)120pp. 161-172
Exergy analysis method is applied to evaluate the performance of reactive distillation (RD) column in the acetic acid production process, at which acetic acid is produced via reaction between carbon monoxide and methanol with a soluble catalyst system consisting of rhodium complex (catalyst) and methyl iodide-hydrogen iodide (promoter). In this column, desired purity of the product is obtained through reaction between methanol and hydrogen iodide. The effects of different operational parameters on the separation and the exergy efficiencies of this RD column are evaluated by sensitivity analysis, finally, the response surface methodology (RSM) method is applied for modeling and optimization of the exergy loss. The adequacy of the developed model for exergy losses in the reactive distillation column is evaluated using analysis of variances (ANOVA). The result of ANOVA study shows that the most effective operating parameters are feed stream temperature, boilup ratio, and reflux ratio. As the result of this optimization the exergy losses and energy consumption for the reactive distillation column reduced by 28% and 12% respectively. This study shows that RSM method besides the exergy concept could be an appropriate tool for optimization of complex and energy intensive reactive distillation systems. © 2017 Elsevier B.V.
Energy (18736785)118pp. 77-84
An exergy analysis was conducted for CO2removal process from syngas using methyldiethanolamine activated by piperazine (a-MDEA). The process was simulated with Aspen HYSYS and the validation of the results was performed using the field data of Fanavaran Petrochemical Company. The process was divided into five separate sections. In order to determine the exergy loss, exergy balance equation was established around each section. The results showed that the highest exergy loss amongst five sections returns to the flasher (contributes 31.5% of total exergy loss); followed by the absorber column, stripper column, heat recovery section and the pump. In order to decrease the exergy loss in the process, piperazine concentration in a-MDEA solvent was increased which led to reduction in amine solvent flow rate. According to the results, the total exergy loss is decreased from 3.25 MW to 2.63 MW. When the amine flow rate decreased by 27%, the exergy loss, total energy consumption and the total utilities cost decreased by 19%, 18% and 25%, respectively. © 2016
Chemical Engineering Science (00092509)172pp. 385-394
Conversion of methanol to propylene combined with cracking of C5/C6 and C4 hydrocarbon cuts was studied on a commercial Süd-Chemie Germany ZSM-5 catalyst. The C5/C6 hydrocarbon cut consisted of hydrocarbons with 5 and 6 carbons in their structure (27.74% i-pentene, 43.14% i-hexene, 3.70% i-pentane and 7.37% i-hexane). The C4 hydrocarbon cut consisted of both olefinic and paraffinic molecules. A fraction of the feed hydrocarbon mixture was converted to other hydrocarbons while the conversion of methanol was remained close to 100%. It was observed that co feeding of the hydrocarbons mixture with methanol considerably increase propylene selectivity. Propylene selectivity up to 61% was gained in the propylene via methanol (PVM) process by co feeding of C5/C6 hydrocarbon cuts. For the C4 hydrocarbon cut, propylene selectivity up to 65% was obtained. However, these values do not represent the actual selectivity at actual flow rates of recycle streams. Based on third order polynomials, effects of steady state recycle streams of these cuts are also predicted in this paper. At the best conditions of a steady state recycle stream, 47.7% selectivity was obtained for propylene in the PVM reactors. © 2017 Elsevier Ltd
Food and Bioproducts Processing (09603085)100pp. 351-360
Membrane-immobilized enzymes have received increasing attention in a variety of fields such as biosensors, enzymatic reactors, and membrane bioreactors. In this study, Candida rugosa lipase (CRL) was covalently immobilized on nanocomposite membrane. Initially, the Fe3O4@SiO2 nano-particles were dip-coated onto the ultrafiltration membrane surface through a low temperature hydrothermal (LTH) process, and then, reacted with 3-aminopropyletriethoxysilane (APTS). Glutaraldehyde was used as a coupling agent to covalently immobilize lipase on the nanocomposite membrane surface. Various techniques such as SEM, TEM, XRD, FTIR, AFM, contact angle goniometry and surface free energy measurement were applied to characterize the nanocomposite membrane. The results showed that the immobilization process was successful in terms of enzyme activity and immobilization efficiency. It was found that the activated nanocomposite membrane greatly improved the relative activity and loading capacity in comparison to unmodified UF membrane. The investigation of kinetic parameters of enzymatic reaction shows the decreasing of Km and vmax due to immobilization which represents the increasing of substrate affinity and decreasing of catalytic activity of immobilized enzyme. The higher thermal, storage, and operational stability of immobilized enzyme make it a suitable candidate for to bio-catalytic processes. © 2016
Journal of Industrial and Engineering Chemistry (1226086X)21pp. 580-586
The immobilization of alumina nanoparticles onto the NaX zeolite granules, using the sol-gel and a physical method, for the removal of Cr (III) and Co (II) was investigated. Alumina nanoparticles immobilized zeolite (ANIZ) was characterized by SEM/EDX, XRD and AAS. The results suggested the formation of nanoscale alumina (~30-50. nm) on the zeolite (loading ~8-10. wt%) and the stability of the zeolite structure after the immobilization of alumina nanoparticles. ANIZ showed a good capacity for the removal of metal ions. Kinetic and equilibrium data were best fitted with the pseudo second order model and the Langmuir model respectively. © 2014 The Korean Society of Industrial and Engineering Chemistry.
Food and Bioproducts Processing (09603085)94pp. 657-667
Streptococcus thermophilus and Lactobacillus bulgaricus are the most common yogurt starter cultures used in the dairy industry. Generally, they are produced by single strain fermentation and then mixed together in appropriate proportions for the purpose of yogurt production. In the present study a kinetic model was developed for the growth and lactic acid production by these two bacteria in pH-controlled single strain batch cultures and whey based medium. The model is a function of pH, temperature, biomass, lactic acid, carbon, and nitrogen substrate concentrations. A four-parameter function was used to describe the effect of pH on the growth of each bacterium. Moreover, a modified Arrhenius law was applied in the model to describe the temperature effect. Response surface methodology was implemented to design the experiments in order to estimate the effect of pH and temperature on bacterial growth. The model was validated on a set of 12 experiments for each bacterium. © 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
Journal of Food Engineering (02608774)166pp. 72-79
Streptococcus thermophilus and Lactobacillus bulgaricus are yogurt starter cultures widely used in the dairy industry. Co-culture of these bacteria leads to higher biomass yield than their separate single strain culture because of the proto-cooperation between the two species. In the present study, a kinetic model was developed for the growth and lactic acid production by these two bacteria in pH-controlled co-cultures. This model quantifies the effects of pH, temperature, lactic acid, carbon and nitrogen substrate concentrations, and the influence of each bacterium on the growth of the other. The latter effect was described by considering the calculated concentration of metabolites produced by each of the bacterium which stimulate the growth of the other. The model was validated by the experimental data obtained from a set of 12 experiments which were designed using the response surface methodology. © 2015 Elsevier Ltd. All rights reserved.
Journal Of Environmental Health Science And Engineering (2052336X)13(1)
Pollution associated with crude oil (CO) extraction degrades the quality of waters, threatens drinking water sources and may ham air quality. The systems biology approach aims at learning the kinetics of substrate utilization and bacterial growth for a biological process for which very limited knowledge is available. This study uses the Pseudomonas aeruginosa to degrade CO and determines the kinetic parameters of substrate utilization and bacterial growth modeled from a completely mixed batch reactor. The ability of Pseudomonas aeruginosa can remove 91 % of the total petroleum hydrocarbons and 83 % of the aromatic compounds from oily environment. The value k of 9.31 g of substrate g-1 of microorganism d-1 could be far higher than the value k obtained for petrochemical wastewater treatment and that for municipal wastewater treatment. The production of new cells of using CO as the sole carbon and energy source can exceed 23 of the existing cells per day. The kinetic parameters are verified to contribute to improving the biological removal of CO from oily environment. © 2015 Talaiekhozani et al.
Journal of Molecular Liquids (18733166)211pp. 1060-1073
Adsorption of the nickel and copper ions from single and bi-component solutions by nanostructure γ-alumina is studied experimentally and described by thermodynamic and kinetic modeling. Effects of the contact time, temperature and pH on these adsorptions are investigated. Kinetics of adsorption is studied by fitting the time-dependent data into different mechanisms, among which the pseudo-second order mechanism has been found successful. To model adsorption equilibrium, Freundlich isotherm resulted in the best fitting. With a 200 ppm initial concentration, maximum adsorption capacity at 40 °C for the Ni2 + and Cu2 + ions is measured to be 49.7 mg g- 1 and 31.3 mg g- 1. The Langmuir-Freundlich model could describe the two-component adsorption successfully. © 2015 Published by Elsevier B.V.
Journal of Molecular Liquids (18733166)209pp. 246-257
The removal of Cr (III) and Co (II) from various samples of ionic solutions was investigated using several sorbents such as alumina nanoparticles (Al2O3 NPs), NaX zeolite granules and a new sorbent: alumina nanoparticles immobilized zeolite (ANIZ), in batch mode. The effects of various operating parameters were studied in order to optimize the removal conditions. Results showed that the removal capacity of zeolite has been significantly improved (Cr (III): 31.76%, Co (II): 17.2%) after the immobilization of Al2O3 NPs. Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R) equations were examined to describe the isotherm models and their constants were evaluated. The kinetic data were analyzed using Pseudo first order, Pseudo second order, Elovich and intraparticle diffusion models. The equilibrium data showed excellent correlation for both Langmuir and Freundlich isotherm models and the Pseudo second-order model was fitted to experimental results better than the other kinetic models. Thermodynamic analyses of the equilibrium data suggested that the removal reactions were spontaneous [- ΔG°, kJ·mol- 1 = 29.37 to 43.69 for Cr (III); and 33.54. to 41.61 for Co (II)] and the spontaneity increased with increasing temperature. © 2015 Elsevier B.V. All rights reserved.
Desalination and Water Treatment (19443994)28(1-3)pp. 103-107
Two strains of Pseudomonas aeruginosa were isolated from crude oil of Isfahan oil refinery and used in a lab scale fermenter for removal of floating crude oil pollution from water. Maximum stable removal efficiency of 92% was reached despite the stepwise increase in the culture medium crude oil concentration from 0.1 g/l to 0.3 g/l and maximum biodegradation rate of 98.6 mg/l h was obtained. During 91 d mixed liquid suspended solid (MLSS) changed between 4000 and 8000 mg/l and sludge volume index (SVI) changed between 20 and 90 mg/l. The performance was investigated during a 91 d continuous operation of a fermenter which was intermittently fed with oil-polluted water. It seems biodegradation of this mixed culture is high removal efficiency (92%) in low time (7.5 d). © 2011 Taylor & Francis Group, LLC.
Desalination and Water Treatment (19443994)28(1-3)pp. 108-114
Oil pollution is one of the important environmental problems in the world. In order to degrade floating crude oil in the wastewater, two soil samples were taken from the oil-contaminated soils in Ahwaz (Iran) and an oil refinery complex in Tehran (Iran). Fourteen strains of bacteria iso¬lated from these samples. Among these bacteria a strain marked as A-14 could treat 91% of total petroleum hydrocarbons and 83% of aromatic compounds in the floating crude oil after 10 d. Also the optimum time to reach the maximum removal percent (90%) was found to be 7 d. A-14 was identified to be Pseudomonas aeruginosa. All isolated bacteria in this study were able to produce biosurfactant. A-12 resulted in the best emulsification index that was about 36%. However, this strain could remove only 46% and 37% of the total petroleum hydrocarbons and aromatic compound, respectively. Most of the isolated microorganisms in this study had higher efficiency for the degradation of total petroleum hydrocarbons (TPH) than aromatic compounds. In most of the previous studies, only dissolved or tiny droplet of crude oil were degraded but the pure culture of P. aeruginosa that we isolated them from the oil contaminated soils could degrade floating crude oil with high removal efficiency (90%). © 2011 Taylor & Francis Group, LLC.
Journal of Dispersion Science and Technology (15322351)31(4)pp. 536-550
In this work, the primitive SAFT equation of state along with three different hard-sphere equations was used to correlate and predict mean ionic activity coefficients of aqueous electrolyte solutions. The mean ionic activity coefficient of aqueous electrolyte solutions was considered as the contribution of hard-sphere and dispersion effects. The Mansoori (M), Wang-Khoshkbarchi-Vera (WKV) and Ghotbi-Vera (GV) hard-sphere equations were applied in correlating the mean ionic activity coefficient of electrolyte solutions. The comparison among above indicated equations was shown. First, vapor pressure and densities of water in the temperature range of 373.15 to 423.15K was regressed by SAFT equation of state. In the restrictive primitive mean spherical model, ions were hard spheres without any chain structure. Neither association effects were considered in this study. Clearly, in common used five SAFT parameters were decreased to three, which were calculated by using the experimental mean ionic activity coefficients of electrolyte solutions. The comparison among three hard-sphere equations of state approved that Ghotbi-Vera hard-sphere model (GV) correlated the experimental data accurately than the others; two hard-sphere models. The mean ionic activity coefficients of some electrolyte solutions were being predicted by taking the advantage of the regressed values surely, in a wide range of molality. © Taylor & Francis Group, LLC.
Journal of Zanjan University of Medical Sciences and Health Services (16069366)18(70)pp. 68-80
Background and Objective: Oil pollutions are one of the most important environmental problems worldwide that researchers have tried different methods for its degradation. In this regards biological methods attracted the attention of the researchers more than other methods. The main objective of this study was to find microorganisms that could degrade aromatic components in the floating crude oil. Materials and Methods: In order to find such microorganisms, some samples were taken from areas contaminated by petroleum compounds. Microorganisms that could live with crude oil as sole carbon source were isolated. From these samples 14 microorganisms isolated which all were bacteria. The variations of aromatic compounds concentration were measured by gas chromatography method. Results: Among 14 microorganisms two microorganisms that called A-3 and A-14 had more ability and degraded the aromatic components 89% and 86% respectively. By microbiological techniques it was found that A-14 is pseudomonas aerogenusa. Conclusion: The results of this study showed that biodegradation of aromatic compounds that are one of the must toxic materials in crude oil are possible. Also indicated that some oil-degrading microorganisms exist in the nature that do not need to adaptation for biodegradation of oily compounds.
Korean Journal of Chemical Engineering (19757220)27(1)pp. 253-260
The aim of this work is to model the adsorption process used for mercaptan and water removal from natural gas. Three fixed beds containing Zeolite molecular sieve type 13X, are used in this plant. In this operation, two beds are in process for adsorption purposes and the other one is regenerated simultaneously. This system is also operated under isothermal condition. In modeling of this process, rate of adsorption is approximated by linear driving force (LDF) expression, and the extended Langmuir isotherm is used to describe adsorption equilibrium. The set of partial differential equations of dynamic model is solved by Crank-Nicolson method. The effect of equations of state is also studied and the best equation fitting the industrial data is selected. Also, concentration profile is presented versus bed length at various times. The influences of pressure, inlet concentration and bed height on the breakthrough time are also investigated. © 2010 Korean Institute of Chemical Engineers, Seoul, Korea.
Fluid Phase Equilibria (03783812)287(1)pp. 15-22
We present an approach based on the statistical associating fluids theory (SAFT) to predict the solubility of amino acids in aqueous and aqueous-electrolyte solutions. This approach can describe the association interactions and their effects on the solubility of amino acids. Using the experimental data of activity coefficients of amino acids in water, the parameters of SAFT model for amino acids are obtained. The solubility of several amino acids in the temperature range of 273.15-373.15 K is predicted. Results obtained from the model are in a good accordance with the experimental data. Also, we examine the effect of pH on the solubility of dl-methionine. Addition of an extra amino acid to the binary solution of amino acid + water makes the system more complex. To check the accuracy of model, we study the ternary solution of dl-serine + dl-alanine + water and dl-valine + dl-alanine + water. Predicted results depict that the proposed model has the ability to describe the ternary solution of amino acids, accurately. Finally, the solubility of amino acids in aqueous-electrolyte solutions is investigated. The long-range interactions caused by the presence of ions affects the solubility of amino acids, leading them to be salted in or out. To treat this kind of interaction, the restrictive primitive mean spherical approximation (RP-MSA) is coupled with the SAFT equation of state. The proposed model can accurately predict the solubility of amino acids in aqueous-electrolyte solutions. © 2009 Elsevier B.V. All rights reserved.
Koomesh (23453699)11(1)pp. 41-54
Introduction: Releasing crude oil in environment tends to some problems such as toxic effects, preventing oxygen exchange with aquatic environment, killing lived creatures in water and etc. Due to these problems, the biodegradation of floating crude oil by isolated microorganisms from environment contaminated by crude oil was studied . Material and Methods: in the first step of this study, by liner culture, microorganisms isolated from soil and waste water contaminated by oil. After isolation of microorganisms, the optimization of biodegradation process was performed by using Tagochi method. The tests were performed twice. Five factors in three various levels used in this optimization. These experiments perform duplicate and finally process by tagochi method for determination of optimum condition . Results and discussion: In this study 14 strains of microorganisms were isolated and purified form environment. All microorganisms were identified as bacteria. Among of those, the microorganism called A-14 had the best removal percentage of floating crude oil (about 89%). The emulsification test (E24) indicated that all isolated microorganisms in this study could produce biosurfactant. The optimum condition was obtained for pH equal 7, the volume percentage of crude oil in water equal 3, nitrogen concentration equal 1 mg/l and hydraulic retention time (HRT) equal 5 days. In the optimum condition the removal percent of crude oil was 93%. In this study crude oil with higher concentration was degraded in the time less than other similar previous researches.
Process Safety and Environmental Protection (17443598)86(3)pp. 208-212
Seven strains isolated from DSO (disulfide oil) contaminated soils. Among them, two strains had high potential to remove DSO from contaminated soils. These strains identified as Paenibacillus (a gram positive, nitrogen fixing spore, spore forming bacillus) and Rhodococcus (a gram positive, catalase positive, acid fast forming bacteria), by preliminary tests. The optimal conditions for DSO removal from contaminated soils were determined. The biotic depletion for Paenibacillus pre-grown in nutrient broth was 24.3% and for Rhodococcus was 19.3%. Bioremediation of DSO in soil was investigated by gas chromatography and UV-vis absorption spectroscopy techniques. The results showed that addition of water (20 μl/g soil) to soil is necessary for DSO removal by both strains and none of the strains could remove DSO in concentrations more than 30 μg/g soil. The results also showed that none of these strains could degrade DSO under anaerobic condition. © 2008 The Institution of Chemical Engineers.
Chemical Engineering Science (00092509)61(8)pp. 2675-2687
The performance of continuous solid state bioreactors having two different solid substrate flow patterns, namely plug flow and completely mixed flow, is quantified for both steady-state and transient operation using a simple mathematical model. The core assumption is that each substrate particle acts as an infinitesimal bioreactor. The residence time distribution of the particles is considered in the formulation of the equations for the mixed-flow bioreactor and the error that results from neglecting it is investigated by comparing the simulation results with those of a completely mixed, continuous bioreactor for submerged liquid fermentation (a chemostat). The model is extended to include autolysis, inter-particle inoculation and contamination. Plug flow is shown to have superior performance when high product concentration is needed, if autolysis or other undesirable late emerging phenomena occur, and when non-sterile fermentation using slow-growing microorganisms is undertaken. © 2005 Elsevier Ltd. All rights reserved.
