| 1. |
- Umar, Yusuf, et al.
(författare)
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A renewable lignin-derived bio-oil for boosting the oxidation stability of biodiesel
- 2022
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Ingår i: Renewable Energy. - : Elsevier BV. - 0960-1481. ; 182, s. 867-878
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Tidskriftsartikel (refereegranskat)abstract
- The valorisation of lignin is being increasingly recognised to improve the economics of pulp and paper making mills. In the present study, an integrated lignin–glycerol valorisation strategy is introduced with an overarching aim for enhancing the process value chains. LignoBoost kraft lignin was subjected to base-catalysed depolymerisation using glycerol as a co-solvent. The generated bio-oil was used as a renewable additive to biodiesel for enhancing its oxygen stability. The influence of three independent parameters including temperature, time and glycerol amount on lignin depolymerisation was investigated. Response surface methodology was applied to design the experiments and to optimise the process for maximising the yield and antioxidant impact of bio-oil. The results showed that glycerol has a positive qualitative and quantitative impact on the produced bio-oil, where an enhancement in the yield (up to 23.8%) and antioxidant activity (up to 99 min induction period) were achieved using the PetroOxy method (EN16091). The addition of 1 wt% bio-oil to biodiesel has led to an improvement in the oxidation stability over a neat sample of up to ∼340%, making it compliant with European standard (EN14214). The proposed process presents a biorefinery paradigm for the integrated utilisation of waste cooking oil, lignin and glycerol.
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| 2. |
- Abdelaziz, Omar Y., et al.
(författare)
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On the Oxidative Valorization of Lignin to High-Value Chemicals : A Critical Review of Opportunities and Challenges
- 2022
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Ingår i: ChemSusChem. - : Wiley. - 1864-5631 .- 1864-564X. ; 15:20
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Forskningsöversikt (refereegranskat)abstract
- The efficient valorization of lignin is crucial if we are to replace current petroleum-based feedstock and establish more sustainable and competitive lignocellulosic biorefineries. Pulp and paper mills and second-generation biorefineries produce large quantities of low-value technical lignin as a by-product, which is often combusted on-site for energy recovery. This Review focuses on the conversion of technical lignins by oxidative depolymerization employing heterogeneous catalysts. It scrutinizes the current literature describing the use of various heterogeneous catalysts in the oxidative depolymerization of lignin and includes a comparison of the methods, catalyst loadings, reaction media, and types of catalyst applied, as well as the reaction products and yields. Furthermore, current techniques for the determination of product yields and product recovery are discussed. Finally, challenges and suggestions for future approaches are outlined.
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| 3. |
- Al-Rabiah, Abdulrahman A., et al.
(författare)
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Comparative Kinetic Analysis and Process Optimization for the Production of Dimethyl Ether via Methanol Dehydration over a γ-Alumina Catalyst
- 2022
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Ingår i: Chemical Engineering & Technology. - : Wiley. - 1521-4125 .- 0930-7516. ; 45:2, s. 319-328
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Tidskriftsartikel (refereegranskat)abstract
- Various kinetic models of methanol dehydration to dimethyl ether over a commercial γ-alumina catalyst were compared with a view to selecting the most appropriate model as a basis for process optimization. To achieve significant improvements in the conventional design, the Berčič-and-Levec kinetic model was employed and process intensification was applied to develop a more energy-efficient process, by enhancing the adiabatic reactor performance and maximizing the heat recovery from the highly exothermic reactor. The single-pass conversion of methanol was increased to 83 %, with an inlet temperature of 217 °C to the adiabatic reactor. Application of process intensification resulted in an improved flowsheet, which reduced the total energy requirements by 59.3 % and cut the CO2 emissions by 60.8 %.
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| 4. |
- Al-Rabiah, Abdulrahman A., et al.
(författare)
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Development of a Biomass Gasification Process for the Coproduction of Methanol and Power from Red Sea Microalgae
- 2022
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Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 15:21
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Tidskriftsartikel (refereegranskat)abstract
- In this study, an algae biomass gasification process using a dual fluidized bed with combined power and methanol cogeneration was developed. The gasification process was modeled using Aspen Plus and validated using experimental data of two microalgae species (Nannochloropsis oculata and Dunaliella salina) commonly found on the western coast of Saudi Arabia. The impacts of different operating conditions, including the gasifier temperature, steam-to-biomass ratio, and algae-char split ratio, on the compositions of four main gases (CO, CO2, CH4, and H2) were investigated. The results of the parametric studies indicated that the gasification temperature has a significant effect on the composition of the synthesis gas, where 700–850 °C was the ideal operating range for gasification. Altering the ratio of biomass to steam showed a slightly smaller effect on the synthesis gas composition. The char split ratio should be kept below 75% to ensure an adequate heat supply to the process. The proposed process successfully converted 45.7% of the biomass feed to methanol at a production capacity of 290 metric tons per day. On the other hand, 38 MW of electricity capacity was generated in the combined power cycle.
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| 5. |
- Polukeev, Alexey V., et al.
(författare)
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Combined Experimental and Computational Study of the Mechanism of Acceptorless Alcohol Dehydrogenation by POCOP Iridium Pincer Complexes
- 2022
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Ingår i: Organometallics. - : American Chemical Society (ACS). - 0276-7333 .- 1520-6041. ; 41:7, s. 859-873
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Tidskriftsartikel (refereegranskat)abstract
- Iridium pincer complexes of the type (POCOP)Ir (POCOP = 2,6-(tBu2PO)2C6H3) are very productive catalysts for dehydrogenation of secondary alcohols. To our surprise, we found that turnover frequencies demonstrated by (POCOP)IrH2 (IrH2) are higher in more dilute solutions of the catalyst, which triggered a mechanistic study of alcohol dehydrogenation by IrH2. Here, we provide strong evidence that acceleration by dilution is related to the rate-limiting mass transfer of hydrogen, which, so far, has not received much attention in the literature. Using experimental and computational methods, we show that dehydrogenation has two high-barrier steps, namely the reaction of IrH2 with alcohol to give (POCOP)IrH(OR) (IrH(OR)) and subsequent β-elimination in the latter. Depending on the alcohol and reaction conditions, IrH(OR) can be formed via an associative pathway that includes proton transfer to the hydride or a dissociative mechanism that involves hydrogen elimination from IrH2 to give a 14e (POCOP)Ir species. Rapid re-hydrogenation of IrH(OR) or the 14e (POCOP)Ir by dissolved hydrogen is responsible for the rate retardation in more concentrated solutions of the catalyst. The suggested mechanism gives a satisfactory quantitative description of the catalytic cycle, such that kinetic curves and reaction orders in the catalyst can be reproduced.
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| 6. |
- Robinson, Ada Josefina, et al.
(författare)
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Techno-economic optimization of a process superstructure for lignin valorization
- 2022
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Ingår i: Bioresource Technology. - : Elsevier BV. - 0960-8524. ; 364
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Tidskriftsartikel (refereegranskat)abstract
- Lignin, the most abundant aromatic biopolymer on Earth, is often considered a biorefinery by-product, despite its potential to be valorized into high-added-value chemicals and fuels. In this work, an integrated superstructure-based optimization model was set up and optimized using mixed-integer non-linear programming for the conversion of technical lignin to three main biobased products: aromatic monomers, phenol–formaldehyde resins, and aromatic aldehydes/acids. Several alternative conversion pathways were simultaneously compared to assess the profitability of lignins-based processes by predicting the performance of technologies with different TRL. Upon employing key technologies such as hydrothermal liquefaction, dissolution in solvent, or high-temperature electrolysis, the technical lignins could have a market value of 200 €/t when the market price for aromatic monomers, resins, and vanillin is at least 2.0, 0.8, and 15.0 €/kg, respectively. When lower product selling prices were considered, the aromatic monomers and the resins were not profitable as target products.
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