| 1. |
- Hosseini, Seyedehsan, 1994, et al.
(författare)
-
Alkyl ketene dimer modification of thermomechanical pulp promotes processability with polypropylene
- 2024
-
Ingår i: Polymer Composites. - 1548-0569 .- 0272-8397. ; 45:1, s. 825-835
-
Tidskriftsartikel (refereegranskat)abstract
- Alkyl ketene dimers (AKDs) are known to efficiently react with cellulose with a dual polarity in their structure: a polar component and a nonpolar component. AKD of three different carbon chain lengths, 4, 10, and 16 carbons have been synthesized, and thermomechanical pulp (TMP) fibers were modified by them. The modification of TMP fibers with AKD resulted in an increased water contact angle, showing the presence of the AKDs on the TMP fibers and a new carbonyl peak in the IR spectra, suggesting modification of the TMP fibers with AKD groups. Calculating the Hansen solubility parameters of AKD and AKD conjugated to TMP in polypropylene (PP) indicates improved compatibility, especially of longer chain AKD and TMP AKD. The rheological studies of the composites showed that the AKD with the longest carbon chain decreases the melt viscosity of the PP-TMP-AKD composite, which combined with the shape and the color of the extruded composite filaments indicates improved flow properties and reduced stress build up during processing. The research findings demonstrate the ability of AKD to enhance the dispersibility and compatibility of natural fibers with PP.
|
|
| 2. |
- Zhou, Ming, et al.
(författare)
-
Oligoamine ionic liquids supported on mesoporous microspheres for CO2 separation with good sorption kinetics and low cost
- 2020
-
Ingår i: Journal of CO2 Utilization. - : Elsevier. - 2212-9820 .- 2212-9839. ; 39
-
Tidskriftsartikel (refereegranskat)abstract
- Ionic liquids display good CO2 absorption capacity but poor absorption kinetics and high costs. In the present work, we show that these problems can be solved by impregnating the new low cost ionic liquid pentaethylenehexammonium chloride [PEHA][Cl] and the corresponding amine precursor on a low cost mesoporous microsphere support. Nitrogen adsorption/ desorption, high-resolution SEM and thermogravimetric analysis were employed to analyze the structural and thermal properties of the prepared sorbents. The CO2 adsorption and desorption performance was studied by column experiments and mathematical models were fitted to the data. The results showed that sorbents displayed excellent sorption kinetics and capacity, comparable to the best reports in the literature. In addition, the sorbents could be regenerated and displayed high thermal stability. Finally, the costs of the sorbents developed in the present work is much lower than previously reported sorbents. Therefore this novel supported IL system could be promising for industrial CO2 removal and recovery applications.
|
|
| 3. |
- Yu, Xiaowen, et al.
(författare)
-
Hydrogen Evolution Linked to Selective Oxidation of Glycerol over CoMoO4—A Theoretically Predicted Catalyst
- 2022
-
Ingår i: Advanced Energy Materials. - : Wiley. - 1614-6832 .- 1614-6840. ; 12:14
-
Tidskriftsartikel (refereegranskat)abstract
- Electrochemical valorization of biomass waste (e.g., glycerol) for production of value-added products (such as formic acid) in parallel with hydrogen production holds great potential for developing renewable and clean energy sources. Here, a synergistic effort between theoretical calculations at the atomic level and experiments to predict and validate a promising oxide catalyst for the glycerol oxidation reaction (GOR) are reported, providing a good example of designing novel, cost-effective, and highly efficient electrocatalysts for producing value-added products at the anode and high-purity hydrogen at the cathode. The predicted CoMoO4 catalyst is experimentally validated as a suitable catalyst for GOR and found to perform best among the investigated metal (Mn, Co, Ni) molybdate counterparts. The potential required to reach 10 mA cm−2 is 1.105 V at 60 °C in an electrolyte of 1.0 ᴍ KOH with 0.1 ᴍ glycerol, which is 314 mV lower than for oxygen evolution. The GOR reaction pathway and mechanism based on this CoMoO4 catalyst are revealed by high-performance liquid chromatography and in situ Raman analysis. The coupled quantitative analysis indicates that the CoMoO4 catalyst is highly active toward C—C cleavage, thus presenting a high selectivity (92%) and Faradaic efficiency (90%) for formate production.
|
|
| 4. |
- Zacharias, Savannah C., et al.
(författare)
-
Exploring Supramolecular Gels in Flow-Type Chemistry-Design and Preparation of Stationary Phases
- 2021
-
Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 60:28, s. 10056-10063
-
Tidskriftsartikel (refereegranskat)abstract
- Two major challenges facing chemical synthesis are product isolation and catalyst recovery. One method to overcome these challenges is to perform the synthesis in a flow system with a catalytic stationary phase. However, the polymeric catalytic materials used in flow systems are often laborious to produce. In this study, we investigate a novel supramolecular gel as a catalytic stationary phase material. The gel is based on a modular, easy to synthesize, oxotriphenylhexanoate (OTHO) gelator comprised of a catalytic unit designed to catalyze the Knoevenagel reaction. The catalytic organogel enhances the rate of product formation and can be reused five times. Use of the OTHO to construct catalytic gels is a flexible technique that can be utilized to improve product isolation and reduce wastage of the catalyst.
|
|
| 5. |
- Öhman, Sebastian, 1991-, et al.
(författare)
-
Selective kinetic growth and role of local coordination in forming Al2TiO5-based coatings at lower temperatures
- 2021
-
Ingår i: Materials Advances. - : Royal Society of Chemistry. - 2633-5409. ; 2:17, s. 5737-5751
-
Tidskriftsartikel (refereegranskat)abstract
- Negative thermal expansion is an elusive property found among certain materials, whose potential applications have remained limited due to the many challenges faced in their synthesis. Herein, we report the successful formation of aluminium titanate-based coatings (Al2TiO5), a material renowned for its low-to-negative thermal expansion, by the co-deposition of aluminium-isopropoxide and titanium-isopropoxide in a hot-wall chemical vapour deposition instrument. While coatings grown at 450 °C were amorphous as-deposited, a short-range order into the Al2TiO5-phase was found and analysed by using Raman spectroscopy. Upon subsequent annealing at 700 °C for 3 hours, crystalline coatings were achieved without forming any binary phases. The selective synthesis of the Al2TiO5 phase is ascribed to the precursors’ inherent chemical similarities, resulting in a kinetic targeting of this phase and a short-range homogeneity, entailing its preferred crystallisation. The role of local coordination is expressed by demonstrating the formation of intergrowth phases ascribed to lower coordinating interstices in the compound. Both the formation and crystallisation temperatures reported herein, as well as the timescales needed for the synthesises, are considerably lower than any conventional adopted solid-state techniques used so far to attain the Al2TiO5 phase.
|
|
| 6. |
- Ge, Yaxin, et al.
(författare)
-
Effects of used bed materials on char gasification : Investigating the role of element migration using online alkali measurements
- 2022
-
Ingår i: Fuel processing technology. - : Elsevier. - 0378-3820 .- 1873-7188. ; 238
-
Tidskriftsartikel (refereegranskat)abstract
- Online alkali measurements using surface ionization are employed to study alkali release during heating of used industrial fluidized bed materials and gasification of biomass-based char and bed material mixtures. The alkali release from the bed materials starts at 820 °C and increases with temperature, the time a bed material has experienced in an industrial process, and in the presence of CO2. Online alkali measurement during heating of char mixed with used bed material shows significant alkali uptake by the char. Complementary SEM-EDS studies confirm the alkali results and indicate that other important inorganic elements including Si, Mg, and Ca also migrate from the bed material to the char. The migration of elements initially enhances alkali release and char reactivity, but significantly reduces both during the final stage of the gasification. The observed effects on char gasification become more pronounced with increasing amount of bed material and increasing time the material experienced in an industrial process. The ash-layer on the used bed material is concluded to play an important role as a carrier of alkali and other active components. The char and bed material systems are closely connected under operational conditions, and their material exchange has important implications for the thermal conversion.
|
|
| 7. |
- Mukesh, Chandrakant, et al.
(författare)
-
Production of C-14 Levulinate Ester from Glucose Fermentation Liquors Catalyzed by Acidic Ionic Liquids in a Solvent-Free Self-Biphasic System
- 2020
-
Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 5:10, s. 4828-4835
-
Tidskriftsartikel (refereegranskat)abstract
- Herein, we present the C-14 levulinate ester of 2,3-butanediol as the product of sugar fermentation liquors. The designed Brønsted acidic ionic liquid (BAIL) catalysts enable self-induced phase separation with ester products, and the role of anions has been investigated. Esterification reactions were carried out by 2,3-butanediol (2,3-BDO) and levulinic acid in solvent-free media and low temperatures (60–105 °C). For comparison, sulfuric acid, amberlite IR-120, and sulfonic acid-functionalized pyridinium ionic liquids with different anions were utilized as a catalyst upon esterification reaction. The diester product, namely, butane-2,3-diyl bis(4-oxopentanoate), was formed with a good yield (85%) and selectivity (85%) after complete conversion of 2,3-BDO in 24 h at 80 °C. The low yield (8%) of the monoester was observed. The monoester and diester were separated by a liquid–liquid extraction method. The ester products were characterized by various instrumental techniques such as 1H and 13C NMR, GC–FID, LC–MS, and FT-IR spectroscopy. The Hammett acidity functions of BAILs were determined from UV–vis spectroscopy. The catalyst was successfully recycled and reused in the processes. The spent BAILs were reused in six consecutive cycles with only a ∼7% diminished diester yield and selectivity. The produced levulinate ester will be useful as biofuel additives, solvents, plasticizers, and other applications.
|
|
| 8. |
- Purnomo, Victor, 1992
(författare)
-
Behavior of iron-based oxygen carriers at deep reduction states
- 2024
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Oxygen carriers have an important role as bed materials in both common circulating fluidized bed combustion unit (also known as oxygen-carrier-aided combustion, OCAC) and in various chemical looping processes. Contrary to conventional bed materials, e.g., sand, oxygen carriers are capable of transferring both oxygen and heat. This makes it possible to produce nitrogen-free product gas streams (in the case of chemical looping processes) and achieve a higher fuel conversion. Having been studied for almost three decades, various oxygen carriers show their own pros and cons depending on the processes for which they are intended to be used. Most of the published studies before this doctoral thesis focused on the reactivity and utilization of oxygen carriers in chemical looping combustion (CLC), where a complete fuel conversion is always desired. Nevertheless, this is not the case in, for example, chemical looping gasification, reforming, and water splitting, where only partial fuel oxidation is necessary, and the produced flue gases are the desired products. In such processes, the oxygen carriers can be exposed to a higher reduction degree than it would be in CLC or OCAC. This warrants further investigations into the deep reduction states of relevant oxygen carriers, which are expected to encounter inevitable performance issues under such a harsh environment. In this thesis, some aspects related to the physical performance and properties of various iron-based oxygen carriers in the occurrence of deep reduction states are examined and presented. The first part of the thesis focuses on the fluidization performance, attrition resistance, and particle size and shape analysis. This part is important mainly for assessing material stability. Iron-based oxygen carriers typically tend to encounter bed defludization at a high degree of reduction. The outward migration of iron into the particle surface, which typically creates a FeO/Fe layer, likely causes defludization. Furthermore, the oxidation state of oxygen carriers does affect the attrition resistance of iron oxygen carriers to varying extents. The results indicate that the presence of Fe-Ti and Fe-Si combinations contribute to a generally stable and low attrition rate, while an Fe-Ca system exhibits a decreasing attrition rate. In addition, the influence of exposure to redox cycles and oxidation degree on the size and shape of oxygen carrier particles seems to be minimal. The oxygen carrier particles generally have a high sphericity but are slightly elongated. Reactivity and fuel conversion are the other focuses of this thesis. These have main implications for engineering design but also for material screening. The apparent kinetic study of oxygen carrier performed in this thesis demonstrates that the changing grain size (CGS) model is applicable to predict the reactivity of three iron oxygen carriers in the presence of CO, H2, and CH4. This applies even at lower oxidation degrees (3 – 5 wt.% reduction), where the reactivity of oxygen carriers has generally decreased. Finally, the gasification rate of pine forest residue char remains at similar levels when using either ilmenite or iron sand as the oxygen carrier.
|
|
| 9. |
- Serafin, Jarosław, et al.
(författare)
-
Biomass waste fern leaves as a material for a sustainable method of activated carbon production for CO2 capture
- 2023
-
Ingår i: Biomass and Bioenergy. - 1873-2909 .- 0961-9534. ; 175
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, we report the use of activated carbon synthesized from a sustainable material - fern leaves - as a sorbent for carbon dioxide capture applications. The resource-friendly technology for activated carbon production was applied and described. The activated carbons were prepared by chemical and physical activation and carbonization at the same time at the temperature range of 500–900 °C. This method reduces energy consumption and resources. KOH and CO2 were used as activating agents. The evaluation of the CO2 adsorption ability of the activated carbon was supported by different methods including: elemental analysis using X-ray fluorescence spectroscopy, ash content, surface area and porosity measurements, Raman spectroscopy, X-ray spectroscopy and scanning electron microscopy. Results indicated that the optimum temperature of the synthesis was 700 °C. The highest achieved adsorption of CO2 was equal to 6.77 mmol/g and 3.58 mmol/g at 0 °C and 25 °C, respectively. The activated carbons synthesized from fern leaves showed high CO2 adsorption and selectivity. Moreover, the abundance and low cost of fern leaves make them very promising carbon sources for CO2 sorbents production.
|
|
| 10. |
- Stedt, Kristoffer, 1991, et al.
(författare)
-
Post-harvest cultivation with seafood process waters improves protein levels of Ulva fenestrata while retaining important food sensory attributes
- 2022
-
Ingår i: Frontiers in Marine Science. - : Frontiers Media SA. - 2296-7745.
-
Tidskriftsartikel (refereegranskat)abstract
- Seaweed aquaculture can provide the growing human population with a sustainable source of proteins. Sea-based cultivation is an effective method for farming seaweeds on a large scale and can yield high biomass output. However, the quality and biochemical composition of the biomass is seasonally dependent, which limits the harvests to certain periods of the year. Here we show the possibility to extend the sea-based cultivation season of Ulva fenestrata when aiming for high protein levels, by post-harvest treatment in herring production process waters. We harvested U. fenestrata at an optimal period in terms of yield, but suboptimal in terms of protein content. We then cultivated the seaweed in onshore tank systems with the nutrient-rich process waters for 14 days. We monitored biomass yield, crude protein content, amino acid composition, and content of the health concerning metals arsenic, mercury, lead, and cadmium, as well as the sensory properties of the dried biomass. After cultivation in the process waters, biomass yields were 30 - 40% higher (210 – 230 g fresh weight) compared to in seawater (160 g fresh weight). Also, the crude protein and amino acid content increased three to five times in the process waters, reaching 12 - 17 and 15 – 21% dry weight, respectively. The protein enriched biomass followed food graded standards for heavy metal content, and consumption of the biomass does not exceed health based reference points. Additionally, no sensory attributes regarded as negative were found. This rapid, post-harvest treatment can help extend the cultivation season of sea-based seaweed farms, maximizing their output of sustainable proteins.
|
|
