| 1. |
- Abdelaziz, Omar Y., et al.
(författare)
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Biological valorization of low molecular weight lignin
- 2016
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Ingår i: Biotechnology Advances. - : Elsevier BV. - 0734-9750. ; 34:8, s. 1318-1346
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Forskningsöversikt (refereegranskat)abstract
- Lignin is a major component of lignocellulosic biomass and as such, it is processed in enormous amounts in the pulp and paper industry worldwide. In such industry it mainly serves the purpose of a fuel to provide process steam and electricity, and to a minor extent to provide low grade heat for external purposes. Also from other biorefinery concepts, including 2nd generation ethanol, increasing amounts of lignin will be generated. Other uses for lignin – apart from fuel production – are of increasing interest not least in these new biorefinery concepts. These new uses can broadly be divided into application of the polymer as such, native or modified, or the use of lignin as a feedstock for the production of chemicals. The present review focuses on the latter and in particular the advances in the biological routes for chemicals production from lignin. Such a biological route will likely involve an initial depolymerization, which is followed by biological conversion of the obtained smaller lignin fragments. The conversion can be either a short catalytic conversion into desired chemicals, or a longer metabolic conversion. In this review, we give a brief summary of sources of lignin, methods of depolymerization, biological pathways for conversion of the lignin monomers and the analytical tools necessary for characterizing and evaluating key lignin attributes.
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| 2. |
- Ahmed, Tamer S., et al.
(författare)
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Preparation of Al2O3/AlF3-Supported Ruthenium Catalysts for the Hydrogenolysis of Biodiesel-Derived Crude Glycerol
- 2016
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 55:19, s. 5536-5544
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogenolysis of biodiesel-derived glycerol to value-added chemicals has emerged as an innovative approach to biowaste valorization for a more sustainable society. In the present work, Ru catalysts on Al2O3/AlF3 supports with different AlF3 content were prepared by the aqueous incipient wetness method and tested in the reaction of glycerol hydrogenolysis for the first time. The prepared catalysts were characterized by neutron activation analysis, N2 physisorption, and H2 chemisorption techniques. The catalytic hydrogenation of crude glycerol was performed at a temperature of 473 K and a hydrogen pressure of 4.0 MPa, using a 5 wt % glycerol aqueous solution for 4 h with comprehensive characterization of liquid- and gas-phase products. Texture, structure, and activity of the prepared catalysts were significantly affected by the fluoridation. To understand the mechanism of possible reactions for glycerol hydrogenolysis better, the effects of pH and individual hydrogenolysis of most of the products of the glycerol reaction were investigated.
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| 3. |
- Al-Rabiah, Abdulrahman A., et al.
(författare)
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Effect of styrene-butadiene-styrene copolymer modification on properties of Saudi bitumen
- 2016
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Ingår i: Petroleum Science and Technology. - : Informa UK Limited. - 1532-2459 .- 1091-6466. ; 34:4, s. 321-327
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Tidskriftsartikel (refereegranskat)abstract
- This research investigates the effects of styrene-butadiene-styrene (SBS) copolymer and other plastomers on the behavior of Saudi bitumen. Three bitumen samples, extracted from three Saudi oil refineries, namely Ras Tanura, Riyadh, and Yanbu, were used in this study. The bitumen samples were mixed with different modifiers in various compositions, forming polymer modified bitumens (PMBs). Elasticity parameters, such as ductility and elastic recovery were measured and evaluated. Characteristics of raw bitumen were analyzed to observe the compatibility of bitumen with SBS and plastomers. Bitumen samples were suitable for SBS modification and SBS PMBs showed superior elasticity behaviors compared to plastomer blends.
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| 4. |
- Ali, Dalia A., et al.
(författare)
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Modelling of coal-biomass blends gasification and power plant revamp alternatives in Egypt's natural gas sector
- 2016
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Ingår i: Chemical Engineering Transactions. - 2283-9216. - 9788895608426 ; 52, s. 49-54
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Bokkapitel (refereegranskat)abstract
- Recently, there has been a growing research interest in the co-gasification of biomass with coal to produce syngas and electricity in a sustainable manner. Co-gasification technology do not only decrease potentially the exploitation of a significant amount of conventional coal resources, and thus lower greenhouse gases (GHG) emissions, but also boost the overall gasification process efficiency. In the present work, a rigorous simulation model of an entrained flow gasifier is developed using the Aspen Plus® software environment. The proposed simulation model is tested for an American coal and the model validation is performed in good agreement with practical data. The feedstocks used in the proposed gasifier model are dry Egyptian coal and a blend of an Egyptian coal and rice straw that is gathered locally. The proposed gasifier model mainly consists of three reactors. The first one is a yield reactor where the coal pyrolysis occurs, the second reactor is a stoichiometric reactor where the gasification reactions arise, and the third reactor is a Gibbs reactor where the water-gas and steam-methane reforming reactions take place. The influence of using a feed mixture of 90 % coal and 10 % rice straw on the gasifier efficiency is investigated. The developed model provides a robust basis for revamping of an existing Egyptian natural gas-based power plant to replace its standard fuel with a coal-rice straw blend, in case of low natural gas supply. The model is further employed to assess different revamping scenarios and alternatives within the natural gas power plant. For a dry blend of (90 % Egyptian coal and 10 % rice straw), the cold gas efficiency is estimated as 85.7 %, while for dry Egyptian it is calculated as 79.61 %. The revamped Egyptian natural gas power plant decreases the total annualized cost (TAC) by 52.7 % with respect to a new constructed integrated gasification combined cycle (IGCC) plant. Besides, the payback period decreases to 1.24 y rather than 12 y in case of the construction of a new IGCC power plant.
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| 5. |
- Gadalla, Mamdouh A., et al.
(författare)
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Conceptual insights to debottleneck the Network Pinch in heat-integrated crude oil distillation systems without topology modifications
- 2016
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Ingår i: Energy Conversion and Management. - : Elsevier BV. - 0196-8904. ; 126, s. 329-341
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Tidskriftsartikel (refereegranskat)abstract
- Heat exchanger network pinch sets the limitations of heat recovery for existing network topologies. Improving the heat recovery within a pinched-network is independent of the areas of individual exchangers present in the network, rather the topology of the network must be altered. Such a change in the topology can be very capital intensive and in many cases seems not easy to implement. This research aims to overcome the Network Pinch through proposing process operation changes, avoiding network topology alterations; hence, debottlenecks the heat-integrated systems towards further energy savings beyond the maximum heat recovery limitations. A new graphical representation is recently proposed to simulate existing preheat trains/networks with all energy equipment. The recent graphical representation is employed in this work to identify the pinching matches that limit heat recovery. Therefore, such graphs are key tools to identify potential process changes by which the Network Pinch is overcome. New graphs are constructed involving hot stream temperatures against cold stream temperatures. Existing exchangers are described by straight lines, with slopes related to flows of process streams and heat capacities. Exchanger matches touching the line where hot outlet stream temperature equals cold inlet stream temperature are pinching matches; this condition corresponds to absolute maximum heat recovery (ΔT = 0). Potential process changes within a distillation unit are identified to relax the Network Pinch and further heat recovery is maximised. The slope of such an exchanger match is decreased or the location of the pinching match is altered keeping the same slope. These changes are translated into process changes within the crude oil distillation unit. Accordingly, the process changes are determined based on which match is pinched besides its location within the network. An illustrative example shows that process changes overcome the Network Pinch and energy recovery is increased by 14% beyond the maximum level achieved for the existing process conditions. Capital investments imposed are minor compared with substantial energy cost savings.
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