Ändra sökning
Avgränsa sökresultatet
1 - 21 av 21
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 1. Al-Sabahi, J.
    et al.
    Bora, T.
    Claereboudt, M.
    Al-Abri, M.
    Dutta, Joydeep
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Visible light photocatalytic degradation of HPAM polymer in oil produced water using supported zinc oxide nanorods2018Ingår i: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 351, s. 56-64Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Polymer flooding displacement ability during petroleum extraction from the earth's crust plays an important role in enhanced oil recovery processes. Produced water, as a byproduct, still contain high concentrations of petroleum hydrocarbons and partially hydrolyzed polyacrylamide (HPAM) which is a serious environmental concern. Remediating produced water economically is a big challenge for meeting the permissible discharge limits leading to failure in the effectiveness of the conventional water treatment technologies. Advanced oxidation processes (AOPs) are playing increasing role in the treatment of polluted water and is receiving much attention in recent times as a green and safer water treatment technology. Here we report a new approach to use vertically aligned zinc oxide nanorods (ZnO NRs) supported on substrates engineered for improving their visible light harvesting capacity for effective solar photocatalytic degradation of HPAM. The viscosity of collected oilfield produced water containing HPAM were found to be reduced dramatically when the samples are photocatalytically degraded using ZnO nanorod catalysts irradiated with simulated solar light showing a reduction of 51% within 6 h. With high pressure liquid chromatography 68, 62, 56 and 45% removal of 25, 50, 100 and 150 ppm HPAM, respectively, was demonstrated. The pH of the solution was observed to move to acidic region due to acetamide, nitrate, propionamide and acetic acid which are the intermediate byproducts formed during degradation as determined by mass spectrometry. Zinc oxide nanorod coatings showed about 74% removal efficiency over 5 cycles with less than 1.2% removal of zinc ions after 6 h of light irradiation.

  • 2.
    Ashour, Radwa M.
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Funktionella material, FNM. Nuclear Materials Authority, Egypt.
    El-sayed, R.
    Abdel-Magied, A. F.
    Abdel-khalek, A. A.
    Ali, M. M.
    Forsberg, Kerstin
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Resursåtervinning.
    Uheida, Abdusalam
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Funktionella material, FNM.
    Muhammed, Mamoun
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Funktionella material, FNM.
    Dutta, Joydeep
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Funktionella material, FNM.
    Selective separation of rare earth ions from aqueous solution using functionalized magnetite nanoparticles: kinetic and thermodynamic studies2017Ingår i: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 327, s. 286-296Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Separation of rare earth ions (RE3+) from aqueous solution is a tricky problem due to their physico-chemical similarities of properties. In this study, we investigate the influence of the functionalized ligands on the adsorption efficiency and selective adsorption of La3+, Nd3+, Gd3+ and Y3+ from aqueous solution using Magnetite (Fe3O4) nanoparticles (NPs) functionalized with citric acid (CA@Fe3O4 NPs) or L-cysteine (Cys@Fe3O4 NPs). The microstructure, thermal behavior and surface functionalization of the synthesized nanoparticles were studied. The general adsorption capacity of Cys@Fe3O4 NPs was found to be high (98 mg g−1) in comparison to CA@Fe3O4 NPs (52 mg g−1) at neutral pH 7.0. The adsorption kinetic studies revealed that the adsorption of RE3+ ions follows a pseudo second-order model and the adsorption equilibrium data fits well to the Langmuir isotherm. Thermodynamic studies imply that the adsorption process was endothermic and spontaneous in nature. Controlled desorption within 30 min of the adsorbed RE3+ ions from both Cys@Fe3O4 NPs and CA@Fe3O4 NPs was achieved with 0.5 M HNO3. Furthermore, Cys@Fe3O4 NPs exhibited a higher separation factor (SF) in the separation of Gd3+/La3+, Gd3+/Nd3+, Gd3+/Y3+ ions compared to CA@Fe3O4 NPs.

  • 3.
    Avila, Marta
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Burks, Terrance
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Akhtar, F.
    Department of Materials and Environmental Chemistry, Stockholm Universtiy, Stockholm, Sweden.
    Göthelid, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Materialfysik, MF.
    Lansåker, P. C.
    Department of Engineering Sciences, The Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Uheida, Abdusalam
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Surface functionalized nanofibers for the removal of chromium(VI) from aqueous solutions2014Ingår i: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 245, s. 201-209Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Polyacrylonitrile (PAN) nanofibers functionalized with amine groups (PAN-NH2) were prepared using a simple one-step reaction route. The PAN-NH2 nanofibers were investigated for the removal of chromium(VI) from aqueous solutions. The adsorption and the kinetic characteristics were evaluated in batch process. The adsorption process showed pH dependence and the maximum Cr(VI) adsorption occurred at pH = 2. The Langmuir adsorption model described well the experimental adsorption data and estimated a maximum loading capacity of 156 mg/g, which is a markedly high value compared to other adsorbents reported. The kinetics studies indicated that the equilibrium was attained after 90 min and the experimental data followed a pseudo-second order model suggesting a chemisorption process as the rate limiting step. X-ray Photoelectron Spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) revealed that the adsorption of Cr(VI) species on PAN-NH2 was facilitated through both electrostatic attraction and surface complexation. High desorption efficiency (> 90%) of Cr(VI) was achieved using diluted base solutions that may allow the reuse of PAN-NH2 nanofibers.

  • 4. Danwittayakul, S.
    et al.
    Dutta, Joydeep
    Center of Excellence in Nanotechnology, Asian Institute of Technology.
    Two step copper impregnated zinc oxide microball synthesis for the reduction of activation energy of methanol steam reformation2013Ingår i: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 223, s. 304-308Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cu/ZnO microball catalysts were prepared by a two-step process, where ZnO nanorods supports were first grown hydrothermally followed by the impregnation of copper nanoparticles. Catalytic activities for methanol steam reforming by using Cu/ZnO microball were found to increase with higher copper content. Addition of urea during the metal impregnation process was found to enhance the methanol steam reforming catalytic activity attributed to the larger surface area of the catalyst. Activation energies of synthesized catalyst and CuZnAl commercial catalyst were calculated from the Arrhenius plots of the rate of reaction and were found to affect hydrogen yield. The lowest activation energy of 4.74 kJ mol(-1) was achieved for the optimized catalyst which was half of the activation energy of commercial catalysts.

  • 5.
    Feng, Zhaoxuan
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Odelius, Karin
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Rajarao, Gunaratna Kuttuva
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi.
    Hakkarainen, Minna
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymerteknologi.
    Microwave carbonized cellulose for trace pharmaceutical adsorption2018Ingår i: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 346, s. 557-566Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A promising sustainable strategy to valorize cellulose to high-value adsorbents for trace pharmaceuticals, like diclofenac sodium (DCF), in the water is demonstrated. Carbon nanospheres (CN) as the DCF adsorbent were derived from cellulose through a one-pot microwave-assisted hydrothermal carbonization method. CN exhibited efficient DCF removal (100% removal of 0.001 mg/mL DCF in 30 s and 59% removal of 0.01 mg/mL DCF in 1 h). The adsorption kinetics and isotherm data were well-fitted with the pseudo-second-order kinetic model and Langmuir model, respectively. The adsorption process was endothermic and spontaneous as confirmed by the thermodynamic parameters. Multiple characterization techniques including SEM/EDS, FTIR, FTIR-imaging and zeta potential were applied to qualitatively investigate the adsorption process. π-π stacking and hydrogen bonding were proposed as the dominant adsorption interactions. CN also demonstrated effective adsorption capacity towards three other commonly-detected contaminants in the wastewater including ketoprofen (KP), benzophenone (BZP), and diphenylamine (DPA), each bearing partial structural similarity with DCF. The affinity of the contaminants towards CN followed the order DPA > BZP > DCF > KP, which could be explained by the different configurations and chemical units. It was speculated that for DCF and KP, the steric hindrance and electrostatic repulsion produced by dissociated carboxyl groups can impede the adsorption process as compared to DPA and BZP. This methodology could offer further insights into the drug adsorption on the cellulose-derived carbon adsorbents and the use of bioderived carbons for treatment of wastewaters contaminated with pharmaceuticals.

  • 6.
    Ghorbani, Morteza
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem, Medicinsk avbildning. Mechatronics Engineering Program, Faculty of Engineering and Natural Science, Sabanci University, 34956 Tuzla, Istanbul, Turkey.
    Araz, Sheybani Aghdam
    Faculty of Engineering and Natural Sciences, Sabanci University, Tuzla, Istanbul 34956, Turkey.
    Talebian, Moein
    Mechatronics Engineering Program, Faculty of Engineering and Natural Science, Sabanci University, 34956 Tuzla, Istanbul, Turkey.
    Kosar, Ali
    Mechatronics Engineering Program, Faculty of Engineering and Natural Science, Sabanci University, 34956 Tuzla, Istanbul, Turkey ; Sabanci University Nanotechnology Research and Application Center, 34956 Tuzla, Istanbul, Turkey ; Center of Excellence for Functional Surfaces and Interfaces for Nano-Diagnostics (EFSUN), Sabanci University, Orhanli, 34956 Tuzla, Istanbul, Turkey.
    Cakmak Cebeci, Fevzi
    Faculty of Engineering and Natural Sciences, Sabanci University, Tuzla, Istanbul 34956, Turkey ; Sabanci University Nanotechnology Research and Application Center, 34956 Tuzla, Istanbul, Turkey.
    Grishenkov, Dmitry
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem, Medicinsk avbildning.
    Svagan, Anna Justina
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Facile Hydrodynamic Cavitation ON CHIP via Cellulose Nanofibers Stabilized Perfluorodroplets inside Layer-by-Layer Assembled SLIPS Surfaces2019Ingår i: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The tremendous potential of “hydrodynamic cavitation on microchips” has been highlighted during recent years in various applications. Cavitating flow patterns, substantially depending upon thermophysical and geometrical characteristics, promote diverse industrial and engineering applications, including food and biomedical treatment. Highly vaporous and fully developed patterns in microfluidic devices are of particular interest. In this study, the potential of a new approach, which includes cellulose nanofiber (CNF)- stabilized perfluorodroplets (PFC5s), was assessed inside microfluidic devices. The surfaces of these devices were modified by assembling various sizes of silica nanoparticles, which facilitated in the generation of cavitation bubbles. To examine the pressure effects on the stabilized droplets in the microfluidic devices, the upstream pressure was varied, and the cavitation phenomenon was characterized under different experimental conditions. The results illustrate generation of interesting, fully developed, cavitating flows at low pressures for the stabilized droplets, which has not been previously observed in the literature. Supercavitation flow pattern, filling the entire microchannel, were recorded at the upstream pressure of 1.7 MPa for the case of CNF-stabilized PFC5s, which hardly corresponds to cavitation inception for pure water in the same microfluidic device.

    Publikationen är tillgänglig i fulltext från 2021-09-13 13:48
  • 7.
    Han, Tong
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Ding, Saiman
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik.
    Yang, Weihong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Catalytic pyrolysis of lignin using low-cost materials with different acidities and textural properties as catalysts2019Ingår i: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 373, s. 846-856Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Catalytic fast pyrolysis of lignin was performed using low-cost materials with different acidities and textural properties as catalysts in the present work. The main focus is to understand the role of low-cost catalysts in the fast pyrolysis of lignin. The four most commonly used low-cost catalysts, ilmenite (FeTiO3), bentonite (Al-Si-OH), activated carbon (AC) and red mud (RM), were selected. The results show that bentonite, red mud and activated carbon effectively enhance the dehydration reaction, which is regarded as the dominant way to eliminate oxygen during the pyrolysis process, due to the existence of strong acidic sites. However, only activated carbon is found to be effective in promoting the production of monocyclic aromatic hydrocarbons (MAHs). Two metallic catalysts, i. e., bentonite and red mud, have strong acidities but quite low surface areas and less porous structures. Therefore, the dehydrated intermediates produced are especially easy to repolymerize to form char or coke without the restriction of obtaining a porous structure during the pyrolysis process. Activated carbon has not only a certain acidity but also a rich porous structure. Lignin fast pyrolysis-derived oxygenates can diffuse and react on the well-dispersed active sites within the pores of activated carbons. The catalytic performance of the activated carbon are supposed to be determined by the pore size. Only pores of similar size to lignin fast pyrolysis-derived oxygenates (0.6-1 nm) seems to be effective for the production of MAHs. Pores larger or smaller than lignin fast pyrolysis-derived oxygenates both tend to cause coke deposition rather than MAHs formation.

  • 8.
    Karatzas, Xanthias
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Nilsson, Marita
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Dawody, Jazaer
    Lindström, Bard
    Pettersson, Lars J.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Characterization and optimization of an autothermal diesel and jet fuel reformer for 5 kW(e) mobile fuel cell applications2010Ingår i: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 156, nr 2, s. 366-379Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The present paper describes the characterization of an autothermal reformer designed to generate hydrogen by autothermal reforming (ATR) from commercial diesel fuel (similar to 10 ppm S) and jet fuel (similar to 200 ppm S) for a 5 kW(e) polymer electrolyte fuel cell (PEFC). Commercial noble metal-based catalysts supported on 900 cpsi cordierite monoliths substrates were used for ATR with reproducible results. Parameters investigated in this study were the variation of the fuel inlet temperature, fuel flow and the H2O/C and O-2/C ratios. Temperature profiles were studied both in the axial and radial directions of the reformer. Product gas composition was analyzed using gas chromatography. It was concluded from the experiments that an elevated fuel inlet temperature (>= 60 degrees C) and a higher degree of fuel dispersion, generated via a single-fluid pressurized-swirl nozzle at high fuel flow, significantly improved the performance of the reformer. Complete fuel conversion, a reforming efficiency of 81% and an H-2 selectivity of 96% were established for ATR of diesel at P=5kW(e), H2O/C = 2.5, O-2/C = 0.49 and a fuel inlet temperature of 60 degrees C. No hot-spot formation and negligible coke formation were observed in the reactor at these operating conditions. The reforming of jet fuel resulted in a reforming efficiency of only 42%. A plausible cause is the coke deposition, originating from the aromatics present in the fuel, and the adsorption of S-compounds on the active sites of the reforming catalyst. Our results indicate possibilities for the developed catalytic reformer to be used in mobile fuel cell applications for energy-efficient hydrogen production from diesel fuel.

  • 9.
    Kivisaari, Timo
    et al.
    KTH, Tidigare Institutioner, Kemi.
    Björnbom, Pehr
    KTH, Tidigare Institutioner, Kemi.
    Sylwan, Christopher
    KTH, Tidigare Institutioner, Kemiteknik.
    Jacquinot, B.
    Jansen, D.
    de Groot, A.
    The feasibility of a coal gasifier combined with a high-temperature fuel cell2004Ingår i: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 100, nr 03-jan, s. 167-180Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The purpose of the study presented in this paper was to find out the feasibility of integrating a 50MW fuel cell system, fed by gas from a coal gasifier. with an existing network for distribution of heat and power. The work presented is the results of the technical evaluation of a 50MW coal fired high-temperature fuel cell power plant. The overall system can be divided into four subsystems including: coal gasification, gas cleaning, power generation and heat recovery. The final system, a entrained flow gasifier combined with standard low-temperature gas cleanup and SOFC, resulted in an overall electrical efficiency of about 47%, and an overall efficiency close to 85%.

  • 10. Krawczyk, H.
    et al.
    Oinonen, Petri
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Jönsson, A. -S
    Combined membrane filtration and enzymatic treatment for recovery of high molecular mass hemicelluloses from chemithermomechanical pulp process water2013Ingår i: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 225, s. 292-299Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hemicelluloses with high molecular mass are needed for the manufacture of value added products such as food packaging barrier films. In this work such molecules were recovered from chemithermomechanical pulp (CTMP) process water using an innovative three-stage process comprising membrane separation and enzymatic treatment with laccase. Microfiltration followed by ultrafiltration was found to be a suitable combination in the first stage, providing a concentrated and purified hemicellulose fraction suitable for enzymatic treatment. In both membrane processes a high average flux (260 and 115 l/m(2) h) and a low fouling tendency were observed. A marked increase in the average molecular mass of hemicelluloses with bound lignin moieties was achieved by laccase treatment in the second stage. The enzymatically crosslinked hemicelluloses were finally recovered in the third stage using ultrafiltration. In the final high molecular mass solution the hemicellulose concentration was 54 g/l, the contribution of hemicelluloses to the total solids content 43%, and the viscosity of the solution 27 mPa s. The results demonstrate that a hemicellulose fraction of high quality can be produced from CTMP process water, and that this could constitute a suitable feedstock for the production of, for example, barrier films for renewable packaging.

  • 11. Lilja, J.
    et al.
    Warna, J.
    Salmi, T.
    Pettersson, Lars J.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Ahlkvist, J.
    Grenman, H.
    Ronnholm, M.
    Murzin, D. Y.
    Esterification of propanoic acid with ethanol, 1-propanol and butanol over a heterogeneous fiber catalyst2005Ingår i: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 115, nr 02-jan, s. 1-12Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Esterification kinetics of propanoic acid with ethanol, 1-propanol and butanol over a fibrous polymer-supported sulphonic acid catalyst (Smopex-101) was studied. Experiments were carried out in a batch reactor operating isothermally at three different temperatures: 60, 70 and 75 degrees C (80 degrees C for butanol) and with different initial molar ratios of propanoic acid and alcohol (1:1, 1:2 and 2:1). The fiber catalyst was active and stable in all the experiments. The experimental results were modeled according to a Langmuir-Hinshelwood model and with an advanced adsorption-based model. The activity coefficients were calculated according to the UNIFAC model. The activation energy of esterification of propanoic acid with ethanol was found to be 52.6 kJ/mol, 49.9 kJ/mol with 1-propanol and 47.3 kJ/mol with butanol. The kinetic model, which includes the adsorption of carboxylic acid and water combined with the activities of the species, explained the experimentally recorded concentrations well.

  • 12. Lindström, B.
    et al.
    Agrell, J.
    Pettersson, Lars J.
    KTH, Tidigare Institutioner                               , Kemiteknik.
    Combined methanol reforming for hydrogen generation over monolithic catalysts2003Ingår i: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 93, nr 1, s. 91-101Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An experimental investigation on hydrogen generation from methanol using monolithic catalysts is presented in this paper. The activity and carbon dioxide selectivity for the reforming of methanol over various binary copper-based materials, Cu/Cr, Cu/Zn and Cu/Zr, have been evaluated. The methanol reforming was performed using steam reforming and combined reforming (CMR, a combination of steam reforming and partial oxidation). The CMR process was carried out at two modes of operation: near auto-thermal and at slightly exothermal conditions. The catalysts have been characterized using BET surface area measurement, X-ray diffraction (XRD), temperature programmed reduction (TPR) and scanning electron microscopy (SEM-EDS). The results show that the choice of catalytic material has a great influence on the methanol conversion and carbon dioxide selectivity of the reforming reaction. The zinc-containing catalyst showed the highest activity for the steam reforming process, whereas the copper/chromium catalyst had the highest activity for the CMR process. The copper/zirconium catalyst had the highest CO2 selectivity for all the investigated process alternatives.

  • 13.
    Montecchio, Francesco
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik. KTH, Dept Chem Engn, SE-10044 Stockholm, Sweden..
    Altimira, Mireia
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Andersson, Anna
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik.
    Engvall, Klas
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Processteknologi.
    Fluid dynamics modelling of UV reactors in advanced oxidation processes for VOC abatement applications2019Ingår i: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 369, s. 280-291Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The present work focuses on the treatment of VOC emissions from industrial processes, since they represent a very severe environmental hazard. For removing the VOC, an AOP (Advanced Oxidation Process) stage based on UV light and ozone was considered, analyzing the methods for the unit scale-up. An innovative CFD (Computational Fluid Dynamics) model, combining UV irradiation, reaction kinetics and fluid dynamics, describing the behavior of UV reactors in the laboratory scale, was developed. This model was verified against experimental results, displaying good agreement. Therefore, we concluded the CFD model could adequately describe relevant features regarding the performance of UV reactors. After analyzing the laboratory reactors, two designed and scaled up prototypes, were simulated using the CFD model. While the first prototype has a standard lamps configuration, the second presents an innovative lamps distribution. As for the laboratory cases, the most relevant features in terms of irradiation and reaction were described for the prototypes, comparing their performance. We evaluated both the overall VOC conversion and VOC conversion per UV lamp, analyzing the energy efficiency of each configuration with adequately accuracy. Therefore, we conclude the developed CFD model to be an important tool for reactor scale-up as a result of the good prediction of experimental results and the accurate description of the governing phenomena. By using the developed model, the scale-up process of UV reactors can be quickly improved, by screening various configurations with the simulator before testing them, saving significant time and effort in the development of full-scale reactors.

  • 14.
    Montecchio, Francesco
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik.
    Bäbler, Matthäus
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik.
    Engvall, Klas
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik.
    Development of an irradiation and kinetic model for UV processes in volatile organic compounds abatement applications2018Ingår i: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 348, s. 569-582Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Air pollution from volatile organic compounds (VOCs) is one of the most important environmental hazards. Advanced oxidation processes (AOPs) with UV systems have been showing high potential for the abatement of VOCs. This work is aimed at modeling UV reactors for scaling-up AOPs from lab-scale to full-scale. The proposed model has a novel approach coupling the UV fluence rate to the photo-kinetic mechanism, for a robust understanding of the phenomena involved. The results show that the 185 nm wavelength is deeply absorbed within few centimeters by oxygen, while the 254 nm wavelength is weakly absorbed by the ozone generated in the reactor. Based on the fluence rate calculations, the reactions of ozone generation and depletion were modeled. The ozone net concentration was compared to the experimental results, for model verification. The model accurately predicts the effect of the airflow rate and reactor diameter for the tested cases. The acetaldehyde oxidation reaction was modeled using a simplified kinetic mechanism, using the experimental data of VOC conversion for a further model verification. The suggested reactor models accurately predicted the effect of airflow rate, while exhibiting limitations for the effect of different reactor diameters. Therefore, a computational fluid dynamics (CFD) investigation is needed for an accurate modeling of the VOCs oxidation reaction, implementing the developed analytical expression for reducing the computational workload. By combining the developed model with a CFD simulator, it would be possible to simulate several reactors, also at full-scale, for predicting their performance and identifying optimal configurations.

  • 15.
    Montecchio, Francesco
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Persson, Henry
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Engvall, Klas
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Delin, Jack
    Scandinavian Centriair AB, Sweden.
    Lanza, Roberto
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Development of a stagnation point flow system to screen and test TiO2-based photocatalysts in air purification applications2016Ingår i: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 306, s. 734-744Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An innovative system suitable for the abatement of VOCs (Volatile Organic Compounds), using photo catalysis under UV light, was designed and built. The design of the reactor is based on the stagnation point flow geometry and the fluid dynamics of the system was carefully investigated in order to avoid mass transfer limitations. The proportions of the elements in the reactor were adjusted in order to homogenize the UV irradiation on the catalyst surface. The supports used for the coating of the catalysts were aluminum plates in order to accurately reproduce industrial conditions. After each test, the catalytic plate was examined to evaluate the mechanical strength of the bonding between the catalyst powder and the metallic support. The coating proved to be sufficiently stable for tests in the designed set up. The potential scale-up of the features of the system was considered throughout the design and especially the power of the UV lamps was decided in order to be representative of the industrial cases. In order to evaluate the suitability of the system for catalysis investigations, various photocatalysts, both synthesized and commercial, were screened. Analyzing the activity results, using acetyl aldehyde as a model VOC, it was possible to evaluate clear differences between the samples and P90 proved to be the most active sample. All the aspects investigated in this work demonstrate that the design of the reactor is in accordance with the expectations and that the system is suitable for screening and testing of photocatalysts for VOCs removal applications.

  • 16.
    Nilsson, Marita
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Karatzas, Xanthias
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Lindström, Bård
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Pettersson, Lars J.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Assessing the adaptability to varying fuel supply of an autothermal reformer2008Ingår i: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 142, s. 309-317Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The present paper describes the study of an autothermal reformer and its fuel-flexible capabilities. Experiments have been performed in a reactor designed to generate hydrogen by autothermal reforming for a 1-5 kW(e) polymer electrolyte fuel cell. Both logistic fuels (diesel, gasoline, and E85) and alternative fuel candidates (methanol, ethanol, and dimethyl ether) were tested in the reformer. The same catalyst composition, Rh supported on Ce/La-doped gamma-Al2O3 and deposited on cordierite monoliths, was used for all fuels. The practical feasibility of reforming each fuel in the present reactor design was tested and evaluated in terms of fuel conversion and selectivity to hydrogen and carbon dioxide. Temperature profiles were studied both in the axial and radial direction of the reformer. It was concluded from the experiments that the reformer design was most suitable for use with hydrocarbon mixtures Such as diesel, gasoline, and E85, where it represents a good basis for an optimized multifuel-reformer design.

  • 17.
    Sebelius, Sara
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Le, Tan Thanh
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Pettersson, Lars J.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Lind, Hanna
    Identification of urea decomposition from an SCR perspective: A combination of experimental work and molecular modeling2013Ingår i: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 231, s. 220-226Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    For the automotive industry selective catalytic reduction (SCR) is the most effective way to get rid of poisonous nitrogen oxides (NOX) in the exhaust. Urea is used as precursor for the reducing agent ammonia. The stricter legislation on NOX emissions for heavy duty vehicles in Euro 6 makes it even more important to optimize the conversion of urea to ammonia.Competing with ammonia formation is the formation of two byproducts commonly observed in the SCR system, biuret and cyanuric acid. These byproducts are formed before the SCR catalyst in the trucks. In the literature different possibilities on the reaction pathway to biuret and cyanuric acid are described. The aim of this study is to understand which of these pathways that is more likely to occur.In this study, the decomposition and synthesis pathways from urea to biuret and cyanuric acid were identified by a combination of laboratory experiments and Density Functional Theory (DFT) calculations. This is the first DFT study on these reactions performed without the influence of a catalyst. Accordingly, this is a study of the reactions where they do occur, before and not over the catalyst. A new gas phase FTIR method for urea and its byproducts was developed.

  • 18.
    Shin, Sung-Ho
    et al.
    Korea Res Inst Chem Technol, Res Ctr Biobased Chem, Ulsan 44429, South Korea..
    Lee, Woojoo
    Korea Res Inst Chem Technol, Res Ctr Biobased Chem, Ulsan 44429, South Korea..
    Kim, Seon-Mi
    Korea Res Inst Chem Technol, Res Ctr Biobased Chem, Ulsan 44429, South Korea..
    Lee, Minkyung
    Korea Res Inst Chem Technol, Res Ctr Biobased Chem, Ulsan 44429, South Korea..
    Koo, Jun Mo
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Hwang, Sung Yeon
    Korea Res Inst Chem Technol, Res Ctr Biobased Chem, Ulsan 44429, South Korea.;Univ Sci & Technol, Adv Mat & Chem Engn, Daejeon 34113, South Korea..
    Oh, Dongyeop X.
    Korea Res Inst Chem Technol, Res Ctr Biobased Chem, Ulsan 44429, South Korea.;Univ Sci & Technol, Adv Mat & Chem Engn, Daejeon 34113, South Korea..
    Park, Jeyoung
    Korea Res Inst Chem Technol, Res Ctr Biobased Chem, Ulsan 44429, South Korea.;Univ Sci & Technol, Adv Mat & Chem Engn, Daejeon 34113, South Korea..
    Ion-conductive self-healing hydrogels based on an interpenetrating polymer network for a multimodal sensor2019Ingår i: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 371, s. 452-460Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Conductive self-healing polymer hydrogel and related soft sensor devices are receiving considerable attention from academia to industry because of their impacts on the lifetime and ergonomic design of soft robotics, prosthesis, and health monitoring systems. However, the development of such a material has thus far been limited considering performances and accessibility. Herein, robustness, self-healing, and conductivity for soft electronic skin are realized by an interpenetrating polymer network (IPN) system based on chemical/ionic cross-inked poly(acrylic acid) containing ferric ions, intercalated with physically cross-linked poly(vinyl alcohol). This IPN hydrogel successfully satisfies all three aforementioned capabilities; elongation at break greater than 1400%; recovery to original mechanical properties greater than 80% after 24 h; and 0.14 Sm-1 of ionic conductivity, which is electrically healable. Such ionic conductivity of hydrogels enables multimodal sensing capabilities, i.e., for strain, pressure, and temperature. Particularly, a uniquely designed dual sensor attached to a finger simultaneously detects mechanical folding and pressure changes independently and can undergo large deformation 1000 times repeated and heating up to 90 degrees C.

  • 19. Vrabel, P.
    et al.
    van der Lans, Rgjm
    van der Schot, F. N.
    Luyben, Kcam
    Xu, B.
    Enfors, Sven-Olof
    KTH, Tidigare Institutioner                               , Bioteknologi.
    CMA: integration of fluid dynamics and microbial kinetics in modelling of large-scale fermentations2001Ingår i: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 84, nr 3, s. 463-474Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Transport limitation is regarded as one of the major phenomena leading to process yield reduction in large-scale fermentations. Knowledge of both the fluid dynamics and the microbial kinetics is needed for understanding and describing situations in large-scale production bioreactors. Microbial kinetics of Escherichia coli including flow metabolism was determined in lab-scale batch and fed-batch experiments. The effect of high substrate fluctuations on metabolism was quantified in scale-down experiments. This knowledge was incorporated into a flow model based on the compartment model approach (CMA). The flow model was verified by mixing time experiments on aerated reactors mixed with multiple impellers at different regimes with liquid volumes 8-22 m(3). The integral model, predicting local glucose, acetate and biomass concentrations in different parts of the reactor, was compared to three large-scale fermentations performed in two different reactors. If lab-scale kinetics was used, the biomass prediction overestimated the biomass concentration. Lab-scale kinetics modified by the results of scale-down experiments incorporating the effect of substrate fluctuations gave a rather satisfying description of biomass concentration. Glucose gradients in different parts of the reactor and acetate produced as a result of overflow metabolism were predicted on a qualitative level. The simulations show that at present the decisive factor for a successful integration of fluid dynamics and microbial kinetics is the kinetics.

  • 20.
    Woldemariam, Daniel
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Kullab, Alaa
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Martin, Andrew
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Membrane distillation pilot plant trials with pharmaceutical residues and energy demand analysis2016Ingår i: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 306, s. 471-483Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, an air gap membrane distillation (AGMD) system at pilot scale is applied for purification of effluent from a municipal wastewater treatment plant. A district heating network (DHN) is considered as a heat source for the membrane distillation system. Removal performance of pharmaceutical residuals, specific heat demand, and economic assessments were analyzed on the membrane distillation plant. Almost all targeted pharmaceutical compounds were removed to a very high degree, often below the method detection limit. The heat requirement for the MD process could be sufficiently supplied by the low-temperature district heating return line. Specific heat demands for the AGMD ranges from 692 to 875 kWh/m3 without heat recovery and as low as 105 kWh/m3 when heat recovery is possible. Different approaches to integrating the MD within the DHN system were analyzed; the advantages and shortcomings of each are discussed with emphasis on the MD system’s capacity requirement and annual heat demand. The thermoeconomic analyses from this study presented the potential for energy optimization regarding heat recovery and module design improvement of the current MD equipment.

  • 21. Wågberg, Lars
    et al.
    Eriksson, J.
    New equipment for detection of polymer induced flocculation of cellulosic fibres by using image analysis - application to microparticle systems2000Ingår i: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 80, nr 03-jan, s. 51-63Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The present investigation has shown that the use of image analysis can be a very efficient way to study the state of flocculation of cellulosic fibres. By an FFT analysis of the grey-values of the collected images, of the flowing fibres, it was possible to evaluate both a degree of flocculation of the fibres and an average diameter of the formed flocs. Calibration with model flocs correlated very well with earlier published data.Investigations regarding flocculation of unbleached cellulosic fibres caused by a microparticle based retention aid, i.e. a combined addition of a high molecular mass cationic polyacrylamide (C-PAM) and a bentonite clay, and a site blocking polymer (SBP) (a dimethylamine epichlorohydrine condensate) were also conducted. The results from these measurements show that a preadsorption of the SEP to a surface coverage of 50% of the fibres (i.e. of its saturation adsorption) resulted in a higher degree of flocculation upon addition of the C-PAM of the microparticle based flocculant. This is probably due to a more extended conformation of the C-PAM out from the surface of the cellulosic fibers. These results were also in accordance with earlier published theories. A simultaneous addition of SEP and C-PAM in the microparticle system was not as efficient, regarding flocculation, as a pre-adsorption of the SEP. This can be explained by the fact that the way that both the SEP and the C-PAM are adsorbed is affected by the way the polymers are added. In accordance with earlier publishd data the results indicate that the adsorption of SEP is strongly affected by the presence of the C-PAM.The results nevertheless show that an addition of a SEP has a positive effect on microparticle based retention aids.Finally the present results clearly demonstrate that the polymer addition levels in flocculation studies (which are relevant for practical use) are comparably low compared with saturation adsorption on the fibres and the difference in flocculating ability of differently charged C-PAM is small, compared with their corresponding saturation adsorption. Further investigations in this area are strongly recommended.

1 - 21 av 21
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf