Search

Zirconia-supported vanadium–copper catalysts (VCux:yZr) were used for the oxidative depolymerization of softwood LignoBoost Kraft lignin (LB). Various VCux:yZr catalysts were prepared (x:y = 0:1, 1:4, 1:2, 3:4, 1:1, and 1:0) by incipient wetness impregnation, and reactions were performed in alkaline water at 150 °C under an O2 pressure of 5 bar for 10 min. 1H–13C HSQC NMR spectroscopy was used for product identification and quantification. The most promising catalyst was VCu1:2Zr, giving a total monomer yield of 9 wt% and the highest selectivity for vanillin (59%). This catalyst was characterized before and after use by N2 physisorption, XRD, TGA, SEM-EDS, and XPS. Cleavage of the main interunit linkages in LB, including the β-O-4 bonds and recalcitrant C–C bonds, was also observed. The findings of this study demonstrate the potential of the V–Cu/ZrO2 catalyst system in the production of value-added aromatics from technical lignin under relatively mild conditions. This would contribute to the more sustainable use of an underutilized side-stream in forest-based industries, provided catalyst reuse can be successfully demonstrated. [ABSTRACT FROM AUTHOR]

Crude Distillation Unit (CDU) represents significant challenge for retrofitting and energy optimisation as the most energy intensive consumer in a conventional crude oil refinery. Pinch Technology and its based-methodologies are found primary keys for decades to energy savings in refining industries for a range of common economic-based and environmental objectives or applications. Typical benefits in energy savings are reported within 20–40% of original designs. However, such savings are limited and questioned when modern refiners are dealt with. The current paper addresses the revamping of a modern refinery exhibiting an existing high energy efficiency (≈93%). This implies the maximum potential energy savings would only be 7% at current process conditions. The present research proposes an algorithm that tackles energy recovery of modern refiners, enabling additional savings beyond the energy targets set by the existing process. The algorithm starts by process simulation and validation against real plant data, followed by a network optimisation, e.g. stream splitting, to reach the energy targets set by Pinch Analysis. The energy targets are then moved to another lower level by performing potential process modifications to reduce the energy consumption further. Results showed that the current modern refinery unit could reach its energy targets by stream splitting modifications with hot energy savings of 2.69 MW. Process modifications resulted in additional energy savings of 31.3% beyond the current level of the existing plant alongside less than a year of payback period for estimated capital investment. An environmental assessment is performed, and comparable reductions were obtained with respect to greenhouse gas, with reduction in CO 2 emissions by 45.1%. The proposed retrofit methodology is applicable to minimising energy consumptions of refiners including modern units to achieve energy levels beyond energy targets by new process modifications. Image 1048 • A systematic approach for revamping an existing energy efficient refinery (≈93%). • A rigorous simulation model for a modern CDU with a maximum error 3%. • Additional energy savings beyond the Pinch limitation. • The novel applied process modifications led to 45% reduction in CO 2. [ABSTRACT FROM AUTHOR]

Lignin depolymerisation receives great attention due to the pressing need to find sustainable alternatives to fossil sources for production of fuels and chemicals. In this study, alumina-supported Cu–Mn and Ni–Mo catalysts were tested for oxidative depolymerisation of a technical lignin stream—sodium lignosulphonates—to produce valuable low-molecular-weight aromatics that may be considered for applications in the fuels and chemicals sector. The reactions were performed at elevated temperature and oxygen pressure, and the product mixtures were analysed by size exclusion chromatography, two-dimensional nuclear magnetic resonance spectroscopy and supercritical fluid chromatography mass spectrometry. The best performance was obtained with Cu–Mn/δ-Al2O3, which was thoroughly characterised before and after use by nitrogen physisorption, scanning electron microscopy, energy dispersive spectroscopy, powder X-ray diffraction, thermal gravimetric analysis, inductively coupled plasma optical emission spectrometry and X-ray photoelectron spectroscopy. Major products identified were vanillin, p-hydroxybenzaldehyde, vanillic acid and p-hydroxybenzoic acid as well as smaller aliphatic aldehydes, acids and lactones. [ABSTRACT FROM AUTHOR]

In recent years, much attention has been focused on the hydrogenolysis of biodiesel derived glycerol to other high value products for the sustainable development and efficient valorization strategies. In the present work, alumina-supported Ir catalyst was prepared by the incipient wetness impregnation method and tested in the glycerol hydrogenolysis reaction. The synthesized catalyst was characterized by neutron activation analysis, N2 physisorption, and H2 chemisorption techniques. The experiments standard conditions were 150 mL feed volume, 0.3 g catalyst, 1500 rpm stirring speed, and 5 wt% glycerol aqueous solution for 4 h. The effects of catalyst amount, temperature, hydrogen pressure, stirring speed, and solution pH on glycerol conversion and selectivity of the principal products obtained were also investigated. The glycerol conversion and the 1,2-propanediol selectivity varied from 4.9% to 22% and from 23.8% to 70.3%, respectively. It was found that the selectivity of 1,2-propanediol increased significantly with the increased alkalinity of the reaction medium. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 (Δ T = 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The simulation of existing crude oil distillation processes is distinctive and difficult owing to its complex nature and interactions, including variable feedstocks, highly integrated processes, tight cuts specifications, and environmental limitations. This study introduces a systematic simulation-based algorithm for retrofitting an existing crude distillation column. The algorithm accounts for all details of the associated heat recovery system. Both distillation unit and HEN (heat exchanger network) are addressed simultaneously in the simulation. The proposed procedure is applied to simulate an existing CDU (crude distillation unit) processing 100,000 bbl/d crude oil of an Arabian origin. The rigorous simulation model achieved can fully describe the existing plant performance, and for this it is thus validated with the actual data for column operation parameters, cuts flow and specification, and for all details of heat exchanger network. The results are found in a good agreement with the actual data. The model is then applied for optimisation and revamping projects to minimise the energy consumption and the amount of CO 2 emissions from the refinery. The advantage of the simulation model is its relevance to refining industries in performing any future revamping studies, modification tests, product changes, and capacity enhancement. [ABSTRACT FROM AUTHOR]

Lignocellulosic biomass has emerged as a potentially attractive renewable energy source. Processing technologies of such biomass, particularly its primary separation, still lack economic justification due to intense energy requirements. Establishing an economically viable and energy efficient biorefinery scheme is a significant challenge. In this work, a systematic approach is proposed for improving basic/existing biorefinery designs. This approach is based on enhancing the efficiency of mass and energy utilization through the use of a hierarchical design approach that involves mass and energy integration. The proposed procedure is applied to a novel biorefinery called Organocat to minimize its energy and mass consumption and total annualized cost. An improved heat exchanger network with minimum energy consumption of 4.5 MJ/kg dry biomass is designed. An optimal recycle network with zero fresh water usage and minimum waste discharge is also constructed, making the process more competitive and economically attractive. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Bio-additives from the base-catalysed depolymerisation of LignoBoost kraft lignin. • Effect of reaction variables on bio-oil yield and biodiesel oxidation stability. • Oxidation stability of biodiesel increased up to 340% by adding 1 wt% bio-additive. • An integrated biorefinery concept for valorising lignin and glycerol waste streams. [ABSTRACT FROM AUTHOR]

Background: Lignin is a potential feedstock for microbial conversion into various chemicals. However, the microbial degradation rate of native or technical lignin is low, and chemical depolymerization is needed to obtain reasonable conversion rates. In the current study, nine bacterial strains belonging to the Pseudomonas and Rhodococcus genera were evaluated for their ability to grow on alkaline-treated softwood lignin as a sole carbon source. Results: Pseudomonas fluorescens DSM 50090 and Rhodococcus opacus DSM1069 showed the best growth of the tested species on plates with lignin. Further evaluation of P. fluorescens and R. opacus was made in liquid cultivations with depolymerized softwood Kraft lignin (DL) at a concentration of 1 g/L. Size-exclusion chromatography (SEC) showed that R. opacus consumed most of the available lower-molecular weight compounds (approximately 0.1–0.4 kDa) in the DL, but the weight distribution of larger fractions was almost unaffected. Importantly, the consumed compounds included guaiacol—one of the main monomers in the DL. SEC analysis of P. fluorescens culture broth, in contrast, did not show a large conversion of low-molecular weight compounds, and guaiacol remained unconsumed. However, a significant shift in molecular weight distribution towards lower average weights was seen after cultivation with P. fluorescens. Conclusions: Rhodococcus opacus and P. fluorescens were identified as two potential microbial candidates for the conversion/consumption of base-catalyzed depolymerized lignin, acting on low- and high-molecular weight lignin fragments, respectively. These findings will be of relevance for designing bioconversion of softwood Kraft lignin. [ABSTRACT FROM AUTHOR]

The authors have retracted this article [1] because due to a mistake in the laboratory, SEC analyses of some of the lignin samples used had already been published as part of another article [2]. The data in the section "Characterization of depolymerized lignin streams" was therefore inaccurately presented as new, and part of the materials and methods section was incorrect. To avoid confusion this article has been retracted and the authors have been given the opportunity to resubmit their corrected data. All authors agree to this retraction. [ABSTRACT FROM AUTHOR]

Background: Lignin is a potential feedstock for microbial conversion into various chemicals. However, the degradation rate of native or technical lignin is low, and depolymerization is needed to obtain reasonable conversion rates. In the current study, base-catalyzed depolymerization—using NaOH (5 wt%)—of softwood Kraft lignin was conducted in a continuous-flow reactor system at temperatures in the range 190–240 °C and residence times of 1 or 2 min. The ability of growth of nine bacterial strains belonging to the genera Pseudomonas and Rhodococcus was tested using the alkaline-treated lignin as a sole carbon source. Results: Pseudomonas fluorescens and Rhodococcus opacus showed the best growth of the tested species on plates with lignin. Further evaluation of P. fluorescens and R. opacus was made in liquid cultivations with depolymerized lignin (DL) at a concentration of 1 g/L. Size exclusion chromatography (SEC) showed that R. opacus consumed most of the available lower molecular weight compounds (approximately 0.1–0.4 kDa) in the DL, but the weight distribution of larger fractions was almost unaffected. Importantly, the consumed compounds included guaiacol—one of the main monomers in the DL. SEC analysis of P. fluorescens culture broth, in contrast, did not show a large conversion of low molecular weight compounds, and guaiacol remained unconsumed. However, a significant shift in molecular weight distribution towards lower average weights was seen. Conclusions: Rhodococcus opacus and P. fluorescens were identified as two potential microbial candidates for the conversion/consumption of base-catalyzed depolymerized lignin, acting on low and high molecular weight lignin fragments, respectively. These findings will be of relevance for designing bioconversion of softwood Kraft lignin. [ABSTRACT FROM AUTHOR]

In the present contribution, concepts supporting a new analysis method to retrofit heat exchanger networks (HENs) are presented. The new graphical representation appears to be simple to use and needs no simulation tools or software packages to perform the retrofit calculations and is found valuable for conceptual applications. The temperature driving force new representation (TDF) is accordingly applied to an existing HEN in an Egyptian refinery to boost its energy efficiency and generate cost-effective opportunities. This refinery is the most recent unit installed in Egypt as it has been built in 1994. Since this refinery is very modern, its energy consumption exceeds the benchmark by only 21.5% which is relatively very low compared to its counterparts worldwide. The graphical revamping in application applied on the HEN shows savings of approximately 10.5% in the energy demand with minor structural modifications, achieving some 60% of the potential energy savings with respect to Pinch Analysis benchmarks. The modified preheat train only exceeds the benchmark by 8.8%. Implications and advantages of the new developed approach are also discussed, highlighting the merits of the proposed method. [ABSTRACT FROM AUTHOR]

[Display omitted] • Lignin valorization process superstructure optimized by mathematical modelling. • Performances of different biorefineries were assessed based on the type of technical lignin. • Phenol-formaldehyde resins revealed the highest costs and yields. • Vanillin production was a profitable option to valorize lignin. • Aromatic monomers can be an opportunity when their market price exceed 2.00€/kg. 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 %. [ABSTRACT FROM AUTHOR]

The aim of this work is to study the performance of nanoporous carbon membrane for hydrogen recovery from off-gas streams. The study is based on a rigorous mathematical model which can predict the performance of nanoporous selective surface flow (SSF) carbon membrane. Basically, the developed model is based on two transport mechanisms: the dusty gas flow through porous media and the surface adsorption-diffusion. The model was employed to simulate the hydrogen recovery from off-gas stream using SSF carbon membrane at different operating conditions. The separation performance of hydrogen-hydrocarbon mixture by nanoporous carbon membrane was evaluated and described. A comparison between the model simulation and the experimental data related to hydrogen recovery from off-gas streams shows good agreement. A parametric study is further carried out to show the effects of pressure at the membrane feed and permeate sides. The effects of flow-rate and type of sweep gas at the membrane permeate side on hydrogen recovery are also shown. SSF membrane illustrates a significant potential to be used for hydrogen recovery from refinery off-gas streams. [ABSTRACT FROM AUTHOR]

• Lignin solubilisation mechanism in pure solvents and mixtures elucidated. • Novel cost-effective and sustainable process developed for fractionating lignin. • Challenges of design and scale-up for integration into value chains identified. • Techno-economic and environment, health and safety metrics developed for benchmarking. The aim of this work is to develop a novel green solvent based sustainable process to refine lignin into low molecular weight (LMW) and high molecular weight (HMW) fractions. Lignin dispersity reduction were experimentally determined using four solvent mixtures, and benchmarked against eight pure solvents. Data outputs were used for modelling the integrated fractionation process. Dispersity reduction of up to 73% was achieved for the high value LMW fraction. Also, a 90% reduction of energy requirement was achieved with an optimized process incorporating a mechanical vapor compression system. This study showed that solvent mixtures involving water can significantly reduce the cost, environment, health and safety impacts of lignin fractionation. Techno-economic evaluation confirmed the economic viability of a large-scale process processing 50 tonne/day of lignin. [ABSTRACT FROM AUTHOR]