| 1. |
- Tehrani, Ali, 1976, et al.
(författare)
-
Solubilization of hydrophobic dyes in surfactant solutions
- 2013
-
Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 6:2, s. 580-608
-
Forskningsöversikt (refereegranskat)abstract
- In this paper, the use of surfactants for solubilization of hydrophobic organic dyes (mainly solvent and disperse dyes) has been reviewed. The effect of parameters such as the chemical structures of the surfactant and the dye, addition of salt and of polyelectrolytes, pH, and temperature on dye solubilization has been discussed. Surfactant self-assemble into micelles in aqueous solution and below the concentration where this occurs-the critical micelle concentration (CMC)-there is no solubilization. Above the CMC, the amount of solubilized dye increases linearly with the increase in surfactant concentration. It is demonstrated that different surfactants work best for different dyes. In general, nonionic surfactants have higher solubilization power than anionic and cationic surfactants. It is likely that the reason for the good performance of nonionic surfactants is that they allow dyes to be accommodated not only in the inner, hydrocarbon part of the micelle but also in the headgroup shell. It is demonstrated that the location of a dye in a surfactant micelle can be assessed from the absorption spectrum of the dye-containing micellar solution.
|
|
| 2. |
- Eliasson Störner, Felicia, 1994, et al.
(författare)
-
Oxygen Carrier Aided Combustion in Fluidized Bed Boilers in Sweden - Review and Future Outlook with Respect to Affordable Bed Materials
- 2021
-
Ingår i: Applied Sciences (Switzerland). - : MDPI AG. - 2076-3417. ; 11:17
-
Forskningsöversikt (refereegranskat)abstract
- Oxygen carriers are metal oxide particles that could potentially enhance both fuel conversion and heat distribution in fluidized bed combustion, resulting in e.g., lowered emissions of unconverted species and better possibilities to utilize low‐grade fuels. A related technology based on fluidized beds with oxygen carriers can separate CO2 without large energy penalties. These technologies are called oxygen carrier aided combustion (OCAC) and chemical‐looping combustion (CLC), respectively. In the past few years, a large number of oxygen carriers have been suggested and evaluated for these purposes, many of which require complex production processes making them costly. Affordable metal oxide particles are, however, produced in large quantities as products and byproducts in the metallurgical industries. Some of these materials have properties making them potentially suitable to use as oxygen carriers. Uniquely for Sweden, the use of oxygen carriers in combustion have been subject to commercialization. This paper reviews results from utilizing low‐cost materials emerging from metallurgical industries for conversion of biomass and waste in semi‐commercial and commercial fluidized bed boilers in Sweden. The paper further goes on to discuss practical aspect of utilizing oxygen carriers, such as production and transport within the unique conditions in Sweden, where biomass and waste combustion as well as metallurgical industries are of large scale. This study concludes that utilizing metal oxides in this way could be technically feasible and beneficial to both the boiler owners and the metallurgical industries.
|
|
| 3. |
- González-Castaño, Miriam, et al.
(författare)
-
3D-printed structured catalysts for CO 2 methanation reaction: Advancing of gyroid-based geometries
- 2022
-
Ingår i: Energy Conversion and Management. - : Elsevier BV. - 0196-8904. ; 258
-
Forskningsöversikt (refereegranskat)abstract
- This work investigates the CO2 methanation rate of structured catalysts by tuning the geometry of 3D-printed metal Fluid Guiding Elements (FGEs) structures based on periodically variable pseudo-gyroid geometries. The enhanced performance showed by the structured catalytic systems is mostly associated with the capability of the FGEs substrate geometries for efficient heat usages. Thus, variations on the channels diameter resulted in ca. 25% greater CO2 conversions values at intermediate temperature ranges. The highest void fraction evidenced in the best performing catalyst (3D-1) favored the radial heat transfer and resulted in significantly enhanced catalytic activity, achieving close to equilibrium (75%) conversions at 400 °C and 120 mL/min. For the 3D-1 catalyst, a mathematical model based on an experimental design was developed thus enabling the estimation of its behavior as a function of temperature, spatial velocity, hydrogen to carbon dioxide (H2/CO2) ratio, and inlet CO2 concentration. Its optimal operating conditions were established under 3 different scenarios: 1) no restrictions, 2) minimum H2:CO2 ratios, and 3) minimum temperatures and H2/CO2 ratio. For instance, for the lattest scenario, the best CO2 methanation conditions require operating at 431 °C, 200 mL/min, H2/CO2 = 3 M ratio, and inlet CO2 concentration = 10 %.
|
|
| 4. |
- Lyngfelt, Anders, 1955
(författare)
-
Chemical Looping Combustion: Status and Development Challenges
- 2020
-
Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 34:8, s. 9077-9093
-
Forskningsöversikt (refereegranskat)abstract
- Because the CO2 capture is inherent in chemical looping combustion (CLC), thus ideally avoiding costly gas separation, this process has potential for uniquely low costs of CO2 capture. The review reports on operational experiences with different oxygen carriers in CLC pilot operation. Further, the application to solid fuels is discussed in terms of technology challenges, routes for upscaling to commercial size, downstream gas treatment, options for achieving adequate circulation, and the use of biofuels in CLC to reach negative emissions. It is concluded that the necessary elements for a scale-up are at hand. Oxygen carrier materials of low cost have been tested in extended operation and found to have reasonable performance with respect to reactivity and lifetime. Designs for large-scale units have been performed, indicating that the process is technically realistic and should have a low cost of CO2 capture. A scale-up strategy to minimize risk and costs has been suggested.
|
|
| 5. |
- Mattisson, Tobias, 1970, et al.
(författare)
-
Chemical-looping technologies using circulating fluidized bed systems: Status of development
- 2018
-
Ingår i: Fuel Processing Technology. - : Elsevier BV. - 0378-3820. ; 172, s. 1-12
-
Forskningsöversikt (refereegranskat)abstract
- In chemical-looping combustion (CLC), an oxygen carrier provides lattice oxygen for complete combustion of a fuel for heat and power production. The reduced metal oxide is then oxidized in a separate reactor. The combustion products CO 2 and H 2 O are obtained in pure form, without any nitrogen in the gas. As no gas separation work is needed, this could be a breakthrough technology for carbon capture (CCS). Normally, the fuel- and air-reactor are designed utilizing inter-connected fluidized beds. The same underlying reversible redox reactions of CLC can be used for other fuel conversion technologies. These include fluidized bed processes for gas, solid and liquid fuels for heat, power, syngas or hydrogen production. Some of these concepts were suggested as far back as the 1950's, while others have just recently been proposed. This paper will provide a review of some recent developments with respect to CLC with gaseous, liquid and solid fuels, with focus on operational experience. Today, more than 35 continuous units have been used worldwide, with over 9000 h of operational time. Although most experience has been reported for methane and natural gas, significant testing has now also been performed with various solid fuels. Some recent developments include i) shift from Ni-based materials to more benign metal oxide oxygen carriers, ii) use of different types of biomass and iii) operation at semi-commercial scale. Furthermore, this paper will also provide an overview some related technologies which also utilize oxygen carriers in interconnected fluidized beds: i) Chemical-looping gasification (CLG), ii) Chemical-looping reforming (CLR) and iii) Chemical-looping tar reforming (CLTR). In these processes, a pure syngas/hydrogen can be produced effectively, which could be utilized for chemical or fuel production.
|
|
| 6. |
- Sharma, Poonam, 1990, et al.
(författare)
-
Recent advances in hydrogenation of CO2 into hydrocarbons via methanol intermediate over heterogeneous catalysts
- 2021
-
Ingår i: Catalysis Science and Technology. - : Royal Society of Chemistry (RSC). - 2044-4753 .- 2044-4761. ; 11:5, s. 1665-1697
-
Forskningsöversikt (refereegranskat)abstract
- The efficient conversion of CO2 to hydrocarbons offers a way to replace the dependency on fossil fuels and mitigate the accumulation of surplus CO2 in the atmosphere that causes global warming. Therefore, various efforts have been made in recent years to convert CO2 to fuels and value-added chemicals. In this review, the direct and indirect hydrogenation of CO2 to hydrocarbons via methanol as an intermediate is spotlighted. We discuss the most recent approaches in the direct hydrogenation of CO2 into hydrocarbons via the methanol route wherein catalyst design, catalyst performance, and the reaction mechanism of CO2 hydrogenation are discussed in detail. As a comparison, various studies related to CO2 to methanol on transition metals and metal oxide-based catalysts and methanol to hydrocarbons are also provided, and the performance of various zeolite catalysts in H-2, CO2, and H2O rich environments is discussed during the conversion of methanol to hydrocarbons. In addition, a detailed analysis of the performance and mechanisms of the CO2 hydrogenation reactions is summarized based on different kinetic modeling studies. The challenges remaining in this field are analyzed and future directions associated with direct synthesis of hydrocarbons from CO2 are outlined.
|
|
| 7. |
- Gedde, Ulf W, et al.
(författare)
-
Mass and charge transport in polyethylene – Structure, morphology and properties
- 2023
-
Ingår i: Polymer. - : Elsevier BV. - 0032-3861 .- 1873-2291. ; 266
-
Forskningsöversikt (refereegranskat)abstract
- Polyethylene is a model for semicrystalline polymers that provides the option to vary crystallinity within wide ranges and then to establish relationships between structure and mass and charge transport properties. Three different topics are covered: diffusion of n-hexane in polyethylene, extensive penetrant uptake kinetics, swelling and the design of a novel sensor, and finally electrical conduction in polyethylene, a field important to modern distribution of electric power (HVDC). This feature article presents past and ongoing studies at KTH Royal Institute of Technology using a variety of experimental methods and computer-aided simulation and modelling.
|
|
| 8. |
- Lyseid Authen, Thea, 1993, et al.
(författare)
-
An overview of solvent extraction processes developed in Europe for advanced nuclear fuel recycling, Part 2 — homogeneous recycling
- 2022
-
Ingår i: Separation Science and Technology. - : Informa UK Limited. - 1520-5754 .- 0149-6395. ; 57:11, s. 1724-1744
-
Forskningsöversikt (refereegranskat)abstract
- The hydrometallurgical separation concepts for the recycling of irradiated nuclear fuels developed in Europe are presented and discussed. Whilst Part 1 of the review focused on concepts for heterogeneous recycling of minor actinides, this article focuses on group recycling of transuranic actinides, which would support homogeneous recycling scenarios. Most of these concepts were developed within European collaborative projects and involve solvent extraction processes separating all the actinides (U-Cm) in two cycles. The first cycle uses a monoamide extractant to recover uranium leaving all the transuranic actinides in the aqueous raffinate with the fission products. The second cycle aims for a group recovery of the transuranium elements and several strategies have been proposed for this stage. In this review article, the various solvent extraction processes are summarised and the key features of the process schemes are compared.
|
|
| 9. |
- Babain, V., et al.
(författare)
-
Fluorinated Diluents- A Review
- 2023
-
Ingår i: Solvent Extraction and Ion Exchange. - : Informa UK Limited. - 0736-6299 .- 1532-2262. ; 41:3, s. 253-291
-
Forskningsöversikt (refereegranskat)abstract
- The history of the development of fluorinated compounds as potential diluents in solvent extraction processes is described. Fluorinated diluents were first investigated in the former Soviet Union and later in the United States and Europe. Fluorinated diluents represent a class of compounds that can be used as primary diluents or as phase modifiers. They are of particular utility when extractant solubility is limited in traditional hydrocarbon diluents and a polar diluent is needed. The chemical and physical characterisitics of fluorinated diluents are provided for a broad range of compounds. Other properties such as toxidcity and resistance to radiolysis are described. Fluorinated compounds have been studied for over 40 years and have been used at industrial scale as a primary diluent for cesium and strontium extraction in Russia and as a phase modifer for an insustrial-scale cesium extraction process in the United States. The advantages and disadvantages of traditional hydrocarbon diluents are compared with chlorinated diluents, chlorinated and fluorinated diluents, and a number of different types of fluorinated diluents. Developing trends for teh use of fluorinated diluents in solvent extraction processes are discussed. This article should provide assistance to researchers investigating new or improved solvent extraction processes where traditional hydrocarbon diluents may not be appropriate.
|
|
| 10. |
- Marella, Eko Roy, et al.
(författare)
-
Engineering microbial fatty acid metabolism for biofuels and biochemicals
- 2018
-
Ingår i: Current Opinion in Biotechnology. - : Elsevier BV. - 0958-1669 .- 1879-0429. ; 50, s. 39-46
-
Forskningsöversikt (refereegranskat)abstract
- Traditional oleochemical industry chemically processes animal fats and plant oils to produce detergents, lubricants, biodiesel, plastics, coatings, and other products. Biotechnology offers an alternative process, where the same oleochemicals can be produced from abundant biomass feedstocks using microbial catalysis. This review summarizes the recent advances in the engineering of microbial metabolism for production of fatty acid-derived products. We highlight the efforts in engineering the central carbon metabolism, redox metabolism, controlling the chain length of the products, and obtaining metabolites with different functionalities. The prospects of commercializing microbial oleochemicals are also discussed.
|
|
