Search

In designing effective catalysts, one must consider how to control the accessibility and activity of the active sites. Inspired by nature, we have leveraged the chemistry of thermoresponsive poly(N-isopropylacrylamide) (p-NIPAM) to tailor the extent of solvation of the transition state key surface reaction intermediates during the hydrogenation of nitrobenzene to aniline on Pd/SiO2. Detailed reaction kinetics, catalyst characterization, and NMR diffusion-ordered spectroscopy (DOSY)/nuclear Overhauser effect spectroscopy (NOESY) experiments indicate that nitrobenzene reduction is co-limited by both the formation and the hydrodeoxygenation of phenylhydroxylamine (PHA) to aniline (AN) precursor. Transition-state treatment of the kinetic data revealed that when the temperature is below the lower critical solution temperature (LCST) of p-NIPAM (32 °C), the apparent enthalpy of activation decreases 3-fold. This change was attributed to the drop in the apparent enthalpy of activation when the polymer was in a swollen state. A concomitant reduction in the apparent entropy of activation was obtained at these conditions, indicative of losses in the degree of freedom of the kinetically relevant intermediate (i.e., surface hydrogen). At temperatures above the LCST, it was possible to reverse these effects, leading to similar apparent activation energy as that observed in the Pd/SiO2 catalyst. These results establish the foundational work on the development of materials capable of taming the intrinsic activity of the active site in a fast, reversible manner. We envision that these results will facilitate the development of catalysts that can mimic the homeostatic behavior of enzymes, allowing more stable operation even when complex feedstocks are employed (e.g., biomass conversion and pollution control).

The predictability of pyrolysis yields and product composition of mixed plastics has been studied. To do so, pyrolysis of virgin polymers (HDPE, LDPE, PP, PS and PET) and eight individual sorting categories from a real waste DKR-350 stream (PE rigid/film, PP rigid/film, PET, PS, multilayer flexibles, and clogged materials) was performed in a batch reactor at 500 °C at laboratory scale. The obtained oil/wax, gas, and solid yields and the composition of oil/wax of those individual feedstocks were used as input of a superposition model to predict the corresponding pyrolysis yields and oil/wax composition of mixed feeds, which were later compared with the experimentally measured product yields from the pyrolysis of those mixed streams. This linear model predicts the oil/wax yield of the mixed streams to a reasonable extent, with a maximum yield deviation (overestimation) of 8 percentage points. However, the presence of significant amounts of PET (above 33 wt%) in the mixed plastic streams negatively impacts the production of the condensable product and promotes the formation of solid products beyond the expected predicted values. Quantification of the type of carbon (aliphatic, aromatic and carbonyl) present in all the oil/wax products was done using 13C NMR spectroscopy. A linear model could also predict the aliphatic carbon yield in the condensable product from plastic waste streams with high accuracy (maximum yield difference of 6 percentage points). However, the aromatic carbon yield could not be predicted, probably due to the observed behavior of PET, which interacts with other polymers to promote solid product formation.

Crotonic acid (CA) and trans-2-pentenoic acid (2-PA) can be obtained from renewable resources by pyrolysis of the bio-based poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) copolymer. In this study, direct pyrolysis of the PHBV-enriched biomass into CA and 2-PA was studied under an inert atmosphere and N2 carrier gas flow, aiming at obtaining high acid yields from mixed microbial cultures (MMCs). The highest yields of 80 ± 2% for CA and 67 ± 1% for 2-PA were obtained at conditions of 240 °C, 1 h, and 0.15 L/min nitrogen flow rate, corresponding to a mean hot vapor residence time of 20 s. A similar acid yield was achieved when the pyrolysis was performed under reduced pressure (150 mbar) instead of using nitrogen gas. The combined pyrolysis of extracted PHBV at 220 °C and 90 min with vapor fractionation by distillation resulted in yields of 81 and 92% for CA and 2-PA, respectively.

This paper presents a techno-economic model of two interconnected hybrid microgrids (MGs) whose electricity and thermal dispatch strategy are managed with Sequential Least Squares Programming (SLSQP) optimization technique. MGs combine multiple thermal and electric power generation, transmission, and distribution systems as a whole, to gain a tight integration of weather-dependent distributed renewable generators with multiple stochastic load profiles. Moreover MGs allow to achieve an improvement in the return of investment and better cost of energy. The first part of the work deals with a method to obtain an accurate prediction of climate variables. This method makes use of Fast Fourier Transform (FFT) and polynomial regression to manipulate climate datasets issued by the European Centre for Medium-Range Weather Forecasts (ECMWF). The second part of the work is focused on the optimization of interconnected MGs operations through the SLSQP algorithm. The objective is to obtain the best financial performance (IRR) when clean distributed energy resources (DERs) are exchanging both thermal and electric energy. SLSQP optimizes the energy flows by balancing their contribution with their nominal Levelized Cost of Energy (LCOE). The proposed algorithm is used to simulate innovative business scenarios where revenue streams are generated via sales of energy to end users, sell backs and deliveries of demand response services to the other grids. A business case dealing with two MGs providing clean thermal and electric energies to household communities nearby the city of Bremen (Germany) is examined in the last part of the work. This business case with a payback in two years, an internal rate of return (IRR) at 65% and a LCOE at 0.14 €/kWh, demonstrates how the interconnection of multiple hybrid MGs with SLSQP optimization techniques, makes renewable and DERs outcompeting and could strand investments in fossil fuel generation, shaping the future of clean energy markets.

The deposition of carbon from methane pyrolysis on various porous media was investigated at 950–1100 ◦C. 7 Types of unfunctionalized carriers were used, with pore sizes varying between 4 nm and 250 µm. Carbon deposition over time was measured in a single particle reactor. It was found that the porous samples can exhibit both an induction period as well as a gradual stop in carbon deposition. An induction period was observed for α-Al2O3 samples, but not for γ-Al2O3, SiC and C carriers. Hence, the slow start of the carbon deposition may be caused by substrate material. Furthermore, for all samples, an apparent maximum carbon loading was observed. It was confirmed that this is not caused by pore blockage, as significant surface area remains in these samples at the point of maximum carbon loading. In fact, it was found that fraction of pore volume filled at maximum loading, is a function of the initial pore diameter. The smaller pores fill to a lesser extent than the bigger pores. This maximum achievable carbon fraction was incorporated in a particle model. Using only the fraction of volume filled as a single parameter, the measured loading over time could be described.

The classic criteria to determine if a second-order irreversible gas–liquid reaction (AG+νBBL→νCCL) proceeds in the instantaneous regime are based on the Hatta number, HaA, and the infinite enhancement factor, EA,∞, i.e., HaA>2 and HaA≫EA,∞-1. There is no consensus, however, with respect to the latter threshold value and this work shows that it highly depends on the considered reactant concentrations and rate coefficients, in particular when the non-volatility assumption of the liquid phase component is relieved. Generalizing the original derivation yields an extended expression, which is condensed into a new dimensionless number, φA,∞, and allows to rewrite the second criterion as φA,∞>15, where [Formula presented]. Next, it is demonstrated that a breakthrough of the gas-phase reactant into the bulk-liquid is readily observed at high interface concentrations of the gas-phase reactant with respect to the bulk concentration of the liquid-phase reactant, even though the classic criteria have been met. Such a situation is quite common in the chemical industry, e.g., in case of the selective reactive removal of an impurity (BL) from a process stream containing a valuable product by a soluble gaseous component (AG). The root cause of this deviating behavior results from the position of the reaction plane and an additional criterion, φB,∞>15, is needed to resolve this. As such, the set of improved criteria are necessary and sufficient to describe the instantaneous regime for any position of the reaction plane. To conclude, a methodology is presented to apply the modified criteria to multiple parallel reactions, and the validity of these improved and generalized criteria is numerically demonstrated.

In support of the energy and feedstock transition, new concepts of producing chemical building blocks are necessary. While currently ethylene is mainly produced from fossil feedstocks, this paper explores its production via the electrochemical conversion of CO2. Different process routes were reviewed and a most promising route was selected based on Faradaic efficiency, current density, overpotential, and material availability. In this preferred route, syngas is produced electrochemically from CO2, which is then converted into methanol before the final conversion into ethylene and other high-value chemicals. On this preferred route, a design has been made which includes process design, unit design and a techno-economic evaluation, with CAPEX and OPEX included. Also the CO2 emission is evaluated and it was found that a net consumption of 2.5 ton CO2 per ton high-value chemical can be achieved. As expected, the investment and operational costs are very high with the applied price sets. However, when the electricity price decreases due to developments in renewable energy and a tax is implemented on CO2 emissions, this process can become economically viable and can contribute to CO2 emission reduction in view of climate change.

The conversion of herbaceous biomass to glycols via tungstate catalyzed hydrogenolysis is challenging owing to its high content of extractives, inorganics and S/N, compared with woody biomass. We tested the hydrogenolysis performance of hay in batch autoclave experiments in the presence of soluble sodium polytungstate and Raney Ni at 245°C, both in excess of catalyst as well as under catalyst-starving conditions. By this method, we found that additional tungstate and Raney Ni poisons, or at least their much higher concentrations, are present in the hay feedstock compared with woody biomass. It turns out that N- and in particular S-containing components present in hay are the root cause for deactivation of the hydrogenation catalyst. From the experimental data we have derived feedstock criteria for N and S that should be targeted in terms of catalyst consumption for operation in an industrially relevant window. These challenging criteria urge the development of effective pretreatments for S/N removal or the employment of S/N-tolerant catalysts in the field of catalytic biomass conversion.

The development of reactive-separation processes, in which products are separated from the reaction media (i.e., reactants and catalysts) in a single reaction unit, is of great interest in industry as energy-intensive separation processes can be obviated. One promising alternative to accomplish this process intensification is the utilization of biphasic emulsion systems, where products and reactants can be separated based on differences in solubility. Additionally, when solid nanoparticles with amphiphilic character and catalytic activity are employed in biphasic systems, it is possible to simultaneously stabilize the liquid–liquid interface and catalyze chemical reactions. This new technology leads to (a) increased interfacial area, (b) enhanced mass transfer of molecules between the two phases, (c) simplified reaction/separation processes by using a recoverable solid catalyst instead of surfactants, and (d) effective separation of products from the reaction mixture by differences in their water/oil solubility and thus avoiding distillation that leads to product decomposition. To this end, the present tutorial review explores the fundamentals of Pickering interfacial catalysis (PIC) and its application in biomass upgrading (upgrading of sugars and pyrolysis oil), biogas to liquid products via Fischer–Tropsch synthesis, and biodiesel production in the context of the United Nations sustainable development goals. We conclude this contribution with an outlook of the current bottlenecks in the commercial exploitation of the technology and the possible future directions in which PIC can be employed to facilitate the energy transition and the C-circular economy.

Developing strategies to boost the selectivity for furfural from biomass-based xylose is important for the development of green fuels and chemicals. This study explores the effects of ionic strength on the dehydration of xylose, starting from its phenylboronate diester (PBA2X), under biphasic conditions. Experimental results obtained from reactions at 200 °C in a 1:1 v/v organic-aqueous biphasic system (composed of either 1-methylnaphthalene or toluene and water at pH = 1 from H2SO4) indicate that increasing the ionic strength (by adding Na2SO4) from 0.1 to 6.1 M results in an increased xylose-to-furfural selectivity (from ∼70 to ∼90 mol %). This is partly due to the effect of salt on the partitioning of furfural, which is pushed into the organic phase, while the rate of furfural formation is enhanced, as reported in the literature. Remarkably, however, starting from PBA2X increases the xylose-to-furfural selectivity (88 mol %) beyond the level observed when starting from free xylose (75 mol %). Combined, these results indicate a synergic effect of the use of the PBA diester of xylose as the starting material, biphasic operation, and high ionic strength on the overall xylose-to-furfural selectivity. Based on these results, a process concept is proposed, which connects an extraction step, to retrieve xylose as the boronate diester from a xylose-rich biomass hydrolysate, to the selective furfural production at high-ionic strength under biphasic conditions. Such a process avoids addition of salt to the original biomass feed and thus combines the benefits and selectivity enhancements of ester formation, biphasic operation, and high ionic strength while allowing the recovery of the product and the closing of the process cycles. The validity of the process concept is supported by additional data on partitioning, losses, and product isolation, as well as an analysis of sustainability metrics.

This thesis concerned the capture of CO2 from the atmosphere, which is also referred to as Direct Air Capture, in a steam-assisted temperature-vacuum swing adsorption process (S-TVSA). Harvesting CO2 from air is a method to acquire a sustainable carbon source to be used as raw material in a net zero CO2 emissions scenario. The objective of this thesis is the design and optimization of a DAC process using supported-amine sorbents. The dilute nature of CO2 concentration in the atmosphere means that a huge amount of air must be processed. Efficient gas-solid contacting is therefore essential, which stands or falls with the design and operation of the gas-solid contactor. First, we compared and evaluated two operation modes of such a contactor: batch wise operation in a fixed bed or continuous operation in a cross-flow moving bed. The moving bed configuration showed a reduced capture efficiency compared to the fixed bed configuration. The design of a Direct Air Capture pilot unit with a design capacity of 1 kgCO2/d was an important objective within this thesis. Fixed bed technology with multiple parallel adsorption beds was chosen to achieve semi-continuous operation. For the pilot unit under optimized constant operating conditions, a productivity of 0.27 kgCO2/kgs/d with an energy duty of 14.5 MJ/kgCO2 was obtained. A dynamic model of this process was developed and validated with experimental data. This model is subsequently used for process optimization. Process optimization aims to minimize the cost of CO2 capture. Ambient conditions play an important role, because temperature and relative humidity influence the properties of the adsorbent. Therefore, the main objective of the optimization study is to evaluate the impact of climate conditions on the cost of CO2 capture. It was shown that climates with a higher average temperature are more beneficial for Direct Air Capture. Furthermore, varying seasonal conditions in temperate and continental climates require dynamic process control to minimize cost of Direct Air Capture.

There is a pronounced growth in industrial interest for renewable and environmentally sustainable pathways to produce chemicals. Driven by the desire to move away from linear economic models based on the supply of fossil fuel-based materials, renewable sources for chemicals are being explored. In this thesis, a multistep process to produce crotonic acid (CA) from a waste/wastewater is studied. CA is used in textile, cosmetic, painting, and coating applications and as building block in the synthesis of co-polymers, for example by copolymerization with vinyl acetate. Regardless of its wide range of application, the current production pathway of CA through a petrochemical route is neither renewable nor straightforward. Thus, this research was focused on providing a bio-based pathway to produce CA using a waste/wastewater as a feedstock. First, the waste/wastewater was subjected anaerobic fermentation to produce volatile fatty acids (VFAs). We examined adsorption as an affinity separation technique to recover these VFAs from the fermentation broth using a novel superparamagnetic polymer. Then, the VFAs were fed into an aerobic bio-reactor in which the microorganisms converted the VFAs into an intracellular co-polymer, called poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). After production of the PHBV, we investigated the application of bio-based solvents to extract the PHBV from the cells. Afterwards, the thermal degradation of PHBV towards CA was studied. Pyrolysis of the PHBV results in not only CA, but also in various side products. Therefore, the last step was focused on the purification of the produced bio-based CA.

A combination of molecular modelling and experiments was conducted to study the separation of acrylic acid and propionic acid through extractive distillation with polar aprotic entrainers. It was found that acrylic acid and propionic acid can be efficiently separated through extractive distillation with a polar aprotic entrainer, resulting in the entrainment of acrylic acid and making propionic acid the most volatile compound. Vapour-liquid equilibrium experiments were conducted with 25 wt% acrylic acid, 25 wt% propionic, and 50% wt% entrainer. Dimethyl sulfoxide (DMSO) was found to induce the highest relative volatility of 1.56 at 25 mbar, which agrees well with the predicted value of 1.66 using the simulation software COSMO-RS. The difference in pKa (ΔpKa = 0.63) between acrylic acid and propionic acid is the main cause for the enhanced relative volatility. The corresponding difference in hydrogen bonding strength was calculated using COSMO-RS to result in ΔE = 1.8 kJ/mol at 25 °C between acrylic acid and propionic acid with the total mixture. When dodecane was selected as an entrainer, acrylic acid became the most volatile compound instead of propionic acid. This is explained by the fact that propionic acid has two extra hydrogen atoms available to have a Van der Waals interaction with the carbon atoms of dodecane. The difference in total Van der Waals interaction between the two carboxylic acids in the mixture with dodecane is 1.34 kJ/mol at 25 °C. This difference results in a relative volatility of 0.91, which is too small to be exploited in a distillation process, and it was concluded that for this mixture, DMSO was the best entrainer in the study.

In this thesis, a framework is developed to find a pathway (economically and environmentally) for producing added-value products from several types of microalgae, considering the uncertain conditions of feedstocks. Three types of microalgae biorefineries (Cholera Vulgarise, Haematococcus Pluvialis, Nannochloropsis spp.) are considered that produce six added-value products (pigment, biodiesel, glycerol, omega-3, fertilizer, and biogas). To reach this goal three tasks are executed: 1) development of superstructure optimization framework for identifying promising production routes, 2) The systematic assessment of uncertainty throughout the decision process, and 3) the balancing of economic gains with environmental impact via a life cycle assessment (LCA). Results of optimizing the superstructure with MINLP model show that the type of microalgae does not influence the decision-making regarding the different processing steps and the optimized production pathway is: open pond, sedimentation and flotation, flocculation without any dryer, sonication, organic solvent pigment extraction, n-butanol solvent lipid extraction, lipid production, and anaerobic digestion. The annual profit of the Haematococcus Pluvialis biorefinery is highest with (62$/ kg of microalgae due to the high pigment price (3608.5 $/kg). This biorefinery produces approximately 500 t of pigment bioproducts from 24 Kt biomass by using 200 Kt of wastewater. The uncertain character of these feedstocks affects the annual profit and quantities of bioproducts of microalgae biorefineries. From a Monte Carlo simulation, the average profit margin of Haematococcus Pluvialis biorefinery (as highest profitable microalgae biorefinery) is 62.98 $/kg. This microalgae biorefinery has 80% probability of earning profit margin between 62.55 ($/kg) and 62.98 ($/kg), according to a cumulative distribution function curve. Furthermore, annual profit margin of microalgae biorefinery are reduced by approximately 50% when using actual sunshine duration in the Netherlands. The selected pathways from the superstructure optimization are used to compute the environmental impacts. LCA studies of these three microalgae biorefineries show that Nannochloropsis spp. biorefinery has the most different environmental impacts due to high productivity. The remnant treatment has the greatest impact on global warming, human toxicity, ecotoxicity, and acidification. Cultivation and harvesting have the most eutrophication impact.

Our two-part paper investigates the current status and future trends and suggests a framework for teaching of Process Systems Engineering (PSE) topics that addresses what should be taught and how these topics should be taught effectively in a classroom setting. This first part concerns the “what” – i.e., which specific key PSE topics should constitute the core requirement of chemical engineering education – either a BSc, but in many cases, an MSc, and which application areas should be included. We surveyed existing courses on novel aspects of PSE applications, as well as polling PSE stakeholders to ascertain their opinion of what is taught and the degree to which graduates skills match their expectations. Existing gaps and interesting prospects have been revealed by the surveys leading to suggestions for the future.

This study presents a superstructure framework to evaluate processing pathways for the production of omega-3 and pigments in an algae biorefinery. Different stages such as cultivation, harvesting, dewatering, drying, cell distribution, and extraction are considered as processing sections in this superstructure. To simplify and speed up modelling, each of these technologies is grouped in blocks. The superstructure framework is converted to a mixed-integer nonlinear programming (MINLP) model. It has more than 6.000 constraints/variables. The model is implemented in the Advanced Interactive Multidimensional Modelling System (AIMMS) software. The CPLEX and CONOPT are the selected solvers. The most promising pathways for three types of microalgae are proposed. These have differences in the dewatering section. Furthermore, the different pathways are compared in terms of cost and performance. The results show that the Haematococcus Pluvialis biorefinery leads to the highest profits due to pigments products' high amount and price.

This work presents a superstructure model with the objective to maximize the total profit of biodiesel production by reducing the production cost and increasing the value of the by-product glycerol. The heat integration of the superstructure model is a novel feature which allows further reduction of utility costs and energy consumption of the biodiesel separation. The superstructure model is used to optimize two biodiesel production scenarios from a conventional continuous stirred tank reactor (CSTR) and a membrane reactor (MR). The superstructure optimization is solved with Advanced Interactive Multidimensional Modeling System (AIMMS) software. The annual profit of the new optimized production pathway for the conventional reactor is 840,606 $. The biodiesel production pathway with the membrane reactor consumed 70% less energy than the conventional reactor. However, the production cost of the MR is nearly two times higher than the CSTR due to the low biodiesel yield of the membrane reactor. The results show the potential to improve traditional biodiesel production and make intensified production methods more viable with the superstructure optimization.

Processing pineapple field residues (PR), a significant waste from the pineapple industry, into multiple value-added products based on the biorefinery concept can reduce waste disposal and contribute to sustainable development goals. Although PR has been used to produce several added-value products, the production of ethanol, citric acid, and xanthan gum, with its economic feasibility at an industrial scale, has not been investigated so far. The present study evaluates the viability of a biorefinery process of PR by performing a comparative techno-economic analysis of three processing scenarios: (1) a whole biorefinery process that fully utilizes PR biomass and produces ethanol, citric acid, and xanthan gum (E + CA + XG) (2) a process that produces CA and XG, and (3) a process that produces only E. A plant capacity of 4 metric tons/hour was considered in the analysis to mimic an intensive pineapple plantation size. Each processing scenario was modeled using SuperPro Designer, and the economic performance was evaluated based on the internal rate of return (IRR), net present value (NPV), and payback period. Among the three scenarios, the whole biorefinery process (CA + XG + E) showed the highest techno- economic performance with the net present value (NPV), internal rate of return (IRR), and payback period of 122.3 million US-$, 34.8%, and 3.5 years, respectively, due to the diverse revenues and minimized waste disposal cost. On the other hand, the E plant showed the lowest economic performance with a negative NPV.

Widely available natural layered expandable clay minerals (smectites) can sorb carbon dioxide in their interlayer space under specific conditions and hence may show potential for gas separation or carbon sequestration processes. This work presents experimental adsorption and desorption measurements of gaseous, sub-critical carbon dioxide (p = 0.1 bar up to 20 bar, T = −20 °C up to 300 °C) on well-characterized anhydrous smectite (Wyoming montmorillonite) and focuses on the effect of the interlayer cation (size). Using seven alkali and alkaline-earth metal cations and three quaternary ammonium cations, a wide range of ionic radii are studied. Physisorption of CO2 in the interlayer space is confirmed via infrared spectroscopy measurements. The results show that optimally sized interlayer cations─comparable to the thickness of a carbon dioxide monolayer─open the interlayer space to make it easily accessible for CO2 up to 1.7 mmol g–1. In particular, Cs-exchanged and tetramethylammonium-exchanged montmorillonite facilitate the rapid sorption of carbon dioxide even at ambient pressure and temperature. These results provide valuable insights into the applicability of widely available natural adsorbent clays for carbon capture and sequestration for the mitigation of climate change.

In this thesis, experimental studies on biomass tars thermal cracking, in the temperature range of 1000 – 1200 °C and gas residence time of 4– 10 s, were carried out in three tar cracking reactor configurations, namely continuously stirred tank reactor (CSTR), packed bed reactor and plug flow reactor (PFR), to investigate the feasibility of reducing tar concentration below 150 mg/Nm3 after tar cracking. Tars were sampled with SPA methods and analyzed in GC/MS for quantification and characterization based on the number of aromatic rings in the tar components. It was observed that in CSTR configuration, the high degree of gas axial dispersion was significantly impacting the tar cracking extent, which was observed to be as high as 1100 mg/Nm3 at 1200°C and residence time of 8.3 s. Using alumina packing material with average diameter of 6 mm, lower gas axial dispersion was achieved and tar concentration was measured to be 575 mg/Nm3 at 1200 °C and shorter gas residence time (4.1 s). In PFR configuration from an initial tar concentration of 8500 mg/Nm3, tar concentration was measured to be 100 mg/Nm3 at 1160 °C and gas residence time of 8.1 s. Increasing the initial tar concentration to 20000 mg/Nm3, similar results were obtained at 1150°C. It was also observed that the main products of tar cracking were carbon, hydrogen gas, CO and CO2. Furthermore, the carbon formed after tar cracking significantly decreased at 1160°C, promoting formation of carbon monoxide, carbon dioxide and hydrogen gas. From the experiments, the apparent activation energy for biomass tar cracking was calculated to be 239 kJ/mol. A kinetic model based on the apparent kinetics of the lumped components and degree of axial dispersion based on the dimensionless Bodenstein (Bo) number, was developed to design a tar cracking unit for a 4 ton/h biomass gasification process.

This work presents an approach to optimize the scheduling and determine the requirements for power systems in the future electricity grid, taking into account the goals of the energy transition in Germany and neighboring countries under uncertain conditions. The value of stochastic solution (VSS) is used as a performance index to compare the deterministic and stochastic approaches. A VSS of up to €800 million of annual grid gross profit is calculated, clearly demonstrating the benefits a stochastic approach brings when determining the required infrastructure investments for the future electricity grid. Energy storage requirements are estimated while considering grid. For high load loss penalties, additional storage capacities of up to 42 GWh are calculated. The uncertainty in the electricity demand has the most expressive impact on grid operation costs, and is for this reason used to generate the scenario array for the stochastic simulations.

Salinity gradient energy, also known as Blue Energy, is the energy released from the mixing of two solutions with different salinity, such as seawater and river water. It is a renewable and sustainable energy source that integrates the hydrological cycle, having an important role in the transition to renewable and clean energy, without CO2 emissions. Reverse electrodialysis is the electro-membrane process used in this thesis to harvest the salinity gradient energy. In reverse electrodialysis, the concentration gradient across ion exchange membranes results in a potential difference over each membrane that can be collected. This thesis focuses on the trade-off between power density and energy efficiency harvesting, including the optimization of both parameters, and enhancing the process’ sustainability. Accordingly, the research aims to understand how electrode segmentation and multistage operation, using scaled-up stacks with artificial and natural seawater and river water can improve the obtained power density and energy efficiency, and aims to evaluate carbon-based slurries’ performance to replace the redox solution at the electrodes. The outcomes presented in this thesis result from both modelling, developed in Python, and experimental work. The experimental work was developed at the laboratory using artificial waters and at a pilot scale using natural waters at the Afsluitdijk, the Netherlands.

Lignocellulosic biomass is a valuable renewable resource that has the potential to be refined into multiple fractions of valuable biomaterials. Extracting and purifying lignin without compromising cellulose quality is a challenging goal. Deep Eutectic Solvents (DESs) have been reported as suitable delignification solvents, and for process development for cellulose extraction, lignin removal is essential. This work describes an investigation on continuous ultrafiltration (UF)-based diafiltration (DF) for recovering and purifying lignin dissolved in a DES-pulping stream comprising lactic acid and choline chloride following lignocellulose delignification. Experiments have been carried out in a stirred dead-end setup. The results indicate that lignin with a molecular weight of 200 g/mol or higher can be rejected by a polyethersulfone UF membrane with a molecular weight cutoff of 5000, reaching rejection values close to 0.85 for the feed solution with lignin concentration ranging from 4.5 to 30 g/L. It was discovered that membrane fouling and flux decline are DES concentration-dependent. A modeling approach was developed to predict the system size and operating conditions necessary to conduct the diafiltration process on a large scale, for which experimental data on lignin fouling at various feed concentrations and hydrodynamic flow characteristics were used. Based on the modeling results, lignin dissolved in DES-dark liquor (lignin-loaded DES) may well be separated and purified by a continuous UF-DF system.

Each of us should work to save the planet from the impending ecological disaster to the best of our abilities. As chemical engineering educators, this means recruiting the young people in our care to apply their skills to the same endeavour. This contribution presents two examples of activities currently in progress at the Technion, Israel and at the University of Twente, Holland, to achieve this aim. The first example concerns the setup of a fast moving consumer goods supply chain, balancing profit with environmental impact. The second example concerns the sustainable production of methanol from concentrated carbon dioxide streams and renewable hydrogen. These two examples illustrate how students can be motivated to design emission-free processes and are intended to feed a further discussion how sustainability can be structurally integrated in the chemical engineering curriculum.

Diisocyanates, a key monomer in polyurethane, are generally lost during recycling. Polyurethane alcoholysis to carbamate and subsequent cracking to isocyanate represents a promising, phosgene-free recycling route. This work reports the thermal and catalytic cracking of a model carbamate (Methyl N-phenyl carbamate, MPC) to isocyanate (Phenyl isocyanate). Multiple catalysts (ZnO, Bi2O3, Al2O3, and Montmorillonite K-10) were evaluated in a closed system (batch autoclaves) to decompose MPC at temperatures of 160–200 °C, with a thorough analysis of the products and high (≥90%) mole balance. The thermal reaction was very limited at these temperatures, whereas the catalytic reaction led mainly to aniline and urea and seemed to be dominated by water adsorbed on the catalyst surface.

This paper aims to contribute to the search for sustainable solutions for CO2 capture from industrial processes such as steelmaking. This is realized by exploring possibilities of a CO2 capture from blast furnace gas using clathrates and comparing this technique to conventional absorption with monoethanolamine (MEA). First a design with pure clathrate hydrates was made to act as a reference and aid to construct a more detailed model for the semiclathrate tetra-n-butyl ammonium bromide (TBAB). Herein the capture process was modeled as a crystallization process in a bubble column like crystallization vessel. It was found that the TBAB process suffers mostly from the low capacity which requires high volume flows. Because of the low temperature, large amounts of expensive refrigerants are required (>300 MW). Because of the high pressure, a large amount of electrical power is required as well (>80 MW). Overall, the process as designed here cannot compete with the conventional MEA process. However, several options were identified that could improve the process in such a way that it could become more feasible. These include an apparently higher capacity than estimated and the use of more stable semiclathrates, hence reducing the need for expensive refrigerants.

A comprehensive kinetic model describes the dehydration of xylose starting from the boronate diester-protected xylose (PBA2X). The model incorporates (de)esterification of PBA2X, partitioning, and xylose dehydration, and aims to evaluate the effects of the solvent system on these steps. The model explores the effect of the water contents in monophasic solvent systems, and that of ionic strength and mixing in biphasic aqueous–organic systems. At low water content, hydrolysis of PBA2X is the rate-limiting step, while xylose dehydration is fast. Conversely, in a monophasic three-solvent system, where the water content is higher, complete hydrolysis of the diester is achieved quickly. Under biphasic conditions, xylose dehydration is fast at high ionic strengths, but the slower partitioning/hydrolysis of PBA2X results in an overall slower furfural production. Furthermore, the observed different but high, constant xylose-to-furfural selectivities observed experimentally are tentatively ascribed to a higher order of parallel side-product formation.

This work presents a novel methodology for integrated multi-objective superstructure optimization and multi-criteria assessment. The method is tailored for sustainable process synthesis utilizing mixed-integer linear programming (MILP). The six-step algorithm includes 1) superstructure formulation, 2) criteria definition and implementation, 3) criteria weighting, 4) single-criterion optimization, 5) reformulation and 6) multi-criteria optimization. It is automated in the Open sUperstrucTure moDelingand OptimizatiOnfRamework (OUTDOOR) and tested on integrated power-to-X and biomass-to-X processes for methanol production. Three criteria are considered, namely net production costs (NPC), net production greenhouse gas emissions (NPE) and net production fresh water demand (NPFWD). The optimization indicates NPC of 1307 €/tMeOH with NPE of -2.23 tœ/tMeOH and NPFWD of -3.42 tH2c/tMeOH for an optimal trade-off plant. The plant configuration features low-pressure alkaline electrolysis for hydrogen supply, absorption-based CO2 capture and steam production from methanol purge gas for internal heat supply. Conducted variation and sensitivity analyses indicate that methanol costs can drop to about 500 €/tMeOH if electricity is free of charge, or to 805 €/tMeOH if biogas is available at large quantities, if a least-cost process layouts are considered. However, all performed multi-criteria analyses imply a robust optimal process design utilizing electricity-based methanol production.

In this study, the role of process systems engineering in enhancing the algae economy is highlighted. First, basic characteristics of the various strains of microalgae are presented. In addition, the beneficial extracted bioproducts and their applications are reviewed. Then, an overview of the various technologies available in each step of biorefinery to produce added-value products and biofuels from microalgae is provided. These technologies are compared in terms of required energy and efficiency. Different perspectives of the algae industry, from molecule to enterprises scale where process systems engineering can have a role, are addressed. Subsequently, the roles of process systems engineering in process and product design, process control, and supply chain of the algae biorefinery are discussed. It is found that process systems engineering can play an important role in the biobased economy, especially by applying sustainability and economic concepts in the decision-making process for selecting the best feedstock, processing pathways, and desired products. Tools such as market analysis, techno-economic analysis, life cycle assessment (LCA), and supply chain (SC) analysis can be applied to design sustainable algae biorefinery. There are, however, several challenges such as the lack of data, the complexity of optimization, and validation that should be addressed before using these tools.

This contribution presents the modelling and optimization strategy of the key intermediate processes in Power-to-X: water electrolysis and carbon capture. While the water electrolysis process is set to maximize the profit provided market data, the control structure in the capture process allows the production of the stoichiometric amount of carbon dioxide for further processing to methanol. The flexible operation of electrolyzers allowed efficient conversion of renewable energy into hydrogen with minimum grid compensation (around 4%). Furthermore, the capture process showed a favourable response to the fluctuating demand of CO2, with deviations lower than 1% over the simulated period. This optimization strategy represents a viable option for Power-to-X processes to cope with the fluctuations of volatile renewable energy.

The present study introduces a methodology to model electricity based hydrogen supply systems as a Mixed Integer Linear Programming (MILP) problem. The novelty of the presented approach lies especially in the linear formulations of the models for electrolysis and salt cavern storage. The proposed linear electrolysis model allows for an accurate consideration of operating limits and operating point-specific efficiencies, while the two-dimensional cavern model treats the cavern volume as a decision variable. The developed formulations are implemented in the open energy modeling framework (oemof) and applied to representative case studies with 2020 marginal conditions. Thereby, it has been confirmed that the individual consideration of power supply and hydrogen demand is crucial for optimal system design and operation. If electricity is drawn exclusively from the German grid, hydrogen costs of 2.67 € are identified along with an increased CO2 footprint compared to natural gas based hydrogen. By contrast, a significantly reduced CO2 footprint results from autarkic wind power supply at costs of at least 4.28 €. Further findings on autarkic operation include optimal ratios of electrolyzer and wind farm nominal power, as well as power curtailment strategies. Evidence is provided that salt cavern interim storage is beneficial. With grid connection, it serves to exploit electricity price fluctuations, while with renewable autarkic operation, it is essential to compensate for seasonal fluctuations in generation.

Process systems engineering (PSE) is a discipline that delivers tools for guided decision-making in the development of new processes and products. Proven successful in the pharmaceutical-, food- and water sectors, it has also breached the field of energy systems. The future energy systems aim to be more efficient, cost-effective, environmentally benign, and interconnected. The design and operation is extremely challenging for decision-makers, engineers, and scientists and here lies a crucial role for the process systems engineer.

Solar energy plays a crucial role in helping cities to decentralize energy production and thus decarbonize the energy mix. Reliable resource assessments are needed to support the deployment of solar power systems, especially in cities of developing countries where large solar potential remains untapped. The aim of this work is to assess the potential of rooftop solar photovoltaic (PV) in three populated cities in Ecuador's mainland (Quito, Guayaquil and Cuenca) and in the Galapagos Islands. The assessment involves (i) the estimation of the available rooftop area based on geographic information system data, (ii) the calculation of energy yield based on hourly satellite-derived irradiance and meteorological data, and (iii) the economic feasibility assessment in terms of levelized cost of electricity (LCOE) compared to representative electricity tariffs. In addition, a sensitivity analysis is carried out to assess the variability of the estimated technical and economic potential with respect to changes in the input parameters. The results reveal a total available rooftop area of about 144 km2, mainly concentrated in urban parishes. The estimated energy yield is 16.94 ± 3.38 TWh/a, which could cover almost twice the annual energy consumption in 2019 of the study areas. The economic assessment shows that the LCOE ranges between 7.65 and 21.12 USD cents/kWh. However, the comparison of LCOE against representative residential tariff suggests that rooftop PV technology is not cost-competitive under most of the financial scenarios. The findings from this study will be of interest for local authorities and other decision makers to design policies and financing strategies to increase the penetration of rooftop PV and thus exploiting the large potential assessed in the study areas. The described methodology can be used for assessing the potential in other regions of Ecuador and thereby support the diversification and decarbonization of the energy mix in the country.

In this study, the carbon capture, utilization, and sequestration (CCUS) supply chain network with real geographic locations of sources and sinks, and different CO2-based products for Germany is proposed here for the first time, because not yet investigated in the literature. The CCUS network is a large-scale comprehensive model which is used to meet the mandated target of CO2 emission reduction at different levels with a maximum profit. The novel CCUS infrastructure includes various stationary sources, capture processes, transportation modes, and sequestration and utilization sites. The results suggest that it is possible to reduce current CO2 emissions by 40-80% in Germany with the total annual costs ranging from 519.34 to 1372.03 billion euro while generating 681.55 to 1880.98 billion euro of revenue annually as a result of producing CO2-based chemical products including methanol, dimethyl ether, formic acid, acetic acid, urea, and polypropylene carbonate. Overall, the optimal CCUS systems achieve economic profits of 999.62-1568.17 euro per ton of CO2 captured and utilized. The CCUS model may be critical in aiding decision-makers to ascertain investment strategies for designing CCUS infrastructures.

Existing districts pose a particular challenge within the transition into a renewable energy system. Especially the heat supply requires innovative concepts. In many districts, renewable energy resources are limited, and district heat supply relies on energy imports from the upstream energy infrastructures, especially the gas and electricity grid. These upstream infrastructures are in an ongoing process of transformation into a renewable energy system with uncertain speed and depth. To design future-proof heat supply concepts, this work presents a scenario-based design approach considering different scenario paths for the upstream energy infrastructures as well as the development of the existing building stock. Therefore, a mixed-integer linear programming model is set up to optimize the energy converter and storage capacities of a generic district heat supply with respect to costs and emission. Additionally, three different refurbishment scenarios are considered for the existing buildings stock. From the results of the different scenarios, future-proof heat supply concepts are derived. The analysis shows that heat-pump capacities in combination with a thermal storage is of great importance for a future carbon-neutral heat supply. A combined heat and power unit helps to reduce emissions in short term. However, only if the gas network has a high share of renewable energies, this technology will compete with electricity based heating via heat-pumps. The results show that electrolysis is at least in short term not a viable option for designing a cost-efficient carbon-neutral district heat supply.

The work defines and discusses process intensification (PI) and digital twin (DT) as potential tools to accelerate the energy transition through their applications in the process industries. The PI technologies take advantage of innovative principles in equipment design and control to improve the physical process, while the DT offers the virtual model of the plant as an environment for production optimization. The effects of both tools on the energy transition are evaluated not only from the point of applications but also from the possibility of implementation and barriers in process industries. Although they are beneficial, the deployment of PI and DT requires not only infrastructure and capital investment but the knowledge and cooperation of different levels of plant personnel. Besides review of individual implementation, this work explores the concept of combining PI and DT which can make them the enabler of each other and bring a breakthrough in optimization of process design and control.

Publisher Copyright: © 2022 by the authors. The world is once again facing massive energy- and environmental challenges, caused by global warming. This time, the situation is complicated by the increase in energy demand after the pandemic years, and the dramatic lack of basic energy supply. The purely “green” energy is still not ready to substitute the fossil energy, but this year the fossil supplies are heavily questioned. Consequently, engineering must take flexible, adaptive, unexpected directions. For example, even the natural gas power plants are currently considered “green” by the European Union Taxonomy, joining the “green” hydrogen. Through a tight integration of highly intermittent renewable, or other distributed energy resources, the microgrid is the technology of choice to guarantee the expected impacts, making clean energy affordable. The focus of this work lies in the techno-economic optimization analysis of Combined Heat and Power (CHP) Multi-Micro Grids (MMG), a novel distribution system architecture comprising two interconnected hybrid microgrids. High computational resources are needed to investigate the CHP-MMG. To this aim, a novel nature-inspired two-layer optimization-simulation algorithm is discussed. The proposed algorithm is used to execute a techno-economic analysis and find the best settings while the energy balance is achieved at minimum operational costs and highest revenues. At a lower level, inside the algorithm, a Sequential Least Squares Programming (SLSQP) method ensures that the stochastic generation and consumption of energy deriving from CHP-MMG trial settings are balanced at each time-step. At the upper level, a novel multi-objective self-adaptive evolutionary algorithm is discussed. This upper level is searching for the best design, sizing, siting, and setting, which guarantees the highest internal rate of return (IRR) and the lowest Levelized Cost of Energy (LCOE). The Artificial Immune Evolutionary (AIE) algorithm imitates how the immune system fights harmful viruses that enter the body. The optimization method is used for sensitivity analysis of hydrogen costs in off-grid and on-grid highly perturbed contexts. It has been observed that the best CHP-MMG settings are those that promote a tight thermal and electrical energy balance between interconnected microgrids. The results demonstrate that such mechanism of energy swarm can keep the LCOE lower than 15 c€/kWh and IRR of over 55%. publishersversion published

Can process intensification change the future of biodiesel? presents the answers for improving biodiesel production with process systems engineering tools such as membrane reactor modeling and superstructure optimization. A novel membrane reactor model with dynamic functions of reversible and irreversible fouling and a new dynamic membrane cleaning model have been developed for biodiesel production. The models can be used to capture the cyclic behavior of the membrane reactor and identify an optimal operating cycle that balances cleaning costs and production capacity. The superstructure model is a network of different alternative options and brings the optimization of biodiesel production from equipment level to process level. An optimal route to produce biodiesel from tallow with reactive distillation and heterogenous acid catalyst is found by solving the superstructure optimization problem. The impacts of different uncertainties such as the prices of feedstock and products, and the production capacity on the total profit of a biodiesel refinery are analyzed. From the technical assessment with the superstructure, process intensification technologies such as reactive distillation are important for biodiesel production in particular and the process industry in general. The thesis discusses the potential of process intensification and digital twin applications in the energy transition of the process industries. The digital twin offers high quality and dynamic models which can be used to develop, test, and improve not only the process intensification designs but also their operating conditions. Therefore, the combination reduces the investments for prototypes and pilot plants as well as the costs of adjusting the physical equipment, allowing a prosperous future for biodiesel.

In this work, first steps towards an industrial application of methane pyrolysis are made. The overall goal of this work is two fold. First, it is aimed to demonstrate a continuous lab scale pyrolysis process. Second, it is aimed to identify the most important parameters affecting the viability of an industrial methane pyrolysis process. In chapter 2 an experimental method is developed in which the inherent methane pyrolysis and carbon deposition kinetics are measured on a single, nonporous, unfunctionalized α- Al2O3 particle. A fixed bed setup (gram C per day scale) was also used to characterize various aspects of methane conversion and side product formation. The gasification reactions are investigated using the same method as in chapter 3, again on nonporous, unfunctionalized α- Al2O3 particles. A method is presented to predict gasification rates as function of the pyrolysis conditions. In chapter 4, the deposition kinetics are expanded to various types of porous particles. The influence of particle characteristics on the carbon deposition within the particle were characterized. Additionally, mass transfer within the particle was investigated. Using this knowledge, a simple particle model was then presented. Using the information obtained in chapters 2-4, a continuous kg C per day lab scale setup was designed and constructed. Finally, in chapter 6 various industrial process configurations are evaluated. Using the knowledge obtained in all the earlier chapters, numerous reactor and process models were constructed. By evaluating the energy and carbon efficiencies of these processes, the most promising were selected and evaluated further. The important parameters driving the viability of these processes were presented. Lastly, a comparison to the industrial standard was presented.

Pyrolysis of a post-consumer plastic waste stream (DKR-350) has been performed at a laboratory scale in a fixed-bed reactor at 500 °C. DKR-350 is a complex mixture of post-consumer plastics comprising polyethylene, polypropylene, polystyrene, polyethylene terephthalate, clogged materials, multilayer flexibles, together with considerable amounts of biogenic and inorganic residues and halogens. The influence of different washing procedures on feedstock composition and pyrolysis product yields was investigated. Washing effectively lowers the biogenic, inorganic and halogen contents in DKR-350, though does not affect the yield of the desired oil/wax (66 to 69 wt%). 27% of the oil/wax lies in the boiling point range of naphtha and gasoline (< 200 °C). During pyrolysis, the oxygen content of the oil/wax is reduced to 8–14 wt%, compared to 10–16 wt% in the feed. Chlorine analysis revealed that most of the chlorine present in the feed is removed by washing. Nevertheless, the concentration of chlorine in the oil/wax is still high (>150 ppm), showing the presence of recalcitrant organochlorides in the feed. Thus, post-treatment is still required to upgrade it to feedstock for the production of fuels and/or chemicals.

This paper presents a method to determine the minimum amount of a catalyst needed to operate a heterogeneously catalyzed reactive distillation column based on kinetic and VLE data only, avoiding rigorous column simulations. Good initial estimates for catalyst loadings are rarely discussed, and shortcut methods are lacking. The described method determines the highest possible reaction rate using known kinetics and column stage temperatures obtained from ternary diagrams of the column top and bottom sections, neglecting the highest or lowest boiler of the column, respectively. The method was validated against several literature cases. From these cases, it could be determined that a conservative estimate for the amount of the catalyst in the early design phase is six times the minimum catalyst found using the method described. Additionally, the presented method provides information regarding the operability of the column, for example, related to catalyst deactivation.

2,5-Furan dicarboxylic acid (FDCA) is a promising intermediate for producing polyethylene furan dicarboxylate, an alternative to polyethylene terephthalate that combines a significantly lower greenhouse gas footprint with better mechanical and gas barrier properties. This work presents a process design and techno-economic evaluation for producing FDCA from non-edible biomass via the oxidation of furfural to furoate salt, and subsequent carboxylation to furandicarboxylate salt. Major technical uncertainties are associated with the possible polymerization of furfural in the oxidation step and the state of salt phase in the carboxylation step. Based on the furfural market price of $1400/ton this process requires a minimum selling price of 2000 ± 500 $/ton FDCA. To compete with purified terephthalic acid (PTA), it requires a premium of 100% for better performance and sustainability, or a combination of much cheaper furfural and a much lower capital expenditures (CAPEX).

BACKGROUND: Phenol is used as a raw material in the polycarbonate industry and as the incentive for bio-based plastics and products is increasing, so is the interest in and demand for bio-based phenols. In renewable phenol production processes based on biomass, impurities derived from the biomass, including other oxygenate compounds, are expected in the phenol containing solution. Vapor–liquid equilibrium (VLE) of phenol and 2-Octanone was studied and impact of impurities thereon to gain insights applicable for similar systems in biorefineries for renewable phenol production. RESULTS: For the binary mixture of phenol - 2-octanone azeotropic VLE behavior was found. The effects of ternary compounds on the molecular interactions between phenol and 2-octanone were studied using isothermal calorimetry (ITC) and molecular modelling (MM), and the impact on the VLE behavior was measured using an ebulliometer. CONCLUSION: It was found that the relative volatility could be improved by adding solvents that are polar and/or contain hydrogen bond accepting groups. Ketones and ethers most strongly improved the relative volatility of the binary mixture 2-octanone – phenol. Addition of a linear alkane, a repelling component especially for 2-octanone, strongly improved the relative volatility as well. ITC and MM results, providing heat of mixing and the interaction energy of mixture components, improved fundamental understanding of the molecular interactions between phenol, 2-octanone and ternary compounds, and supported the VLE findings.

We measured the reaction kinetics of the electrochemical reduction of CO2to formate on Pd/C and evaluated several proposed mechanisms, by comparing model-described and observed rates of formation of HCOO-and H2as a function of several parameters (pH2,pCO2, and potential). An α-/β-hydride mechanism, based on an α-hydride phase active for CO2reduction and a β-hydride Pd-phase active for hydrogen evolution, described the experimental data of our and other laboratories reported in the literature satisfactorily. After parametrization, using a data set including only H2, this mechanism also predicted the outcome of D2isotope labeling experiments correctly. Analyses of the results indicate that the α-/β-hydride ratio and hydride formation rate are key factors affecting the formate production rate and the selectivity, thereby identifying areas for further (spectroscopic) studies and mechanism validation.

Xylose is a promising feedstock for the fuel and chemical industry. We propose here an integrated process to recover and purify xylose from an acidic hydrolysate stream, e.g., coming from pretreated lignocellulose. This process consists of selectively extracting the xylose as the diboronate ester and back-extracting it into a clean aqueous solution. We report 85% xylose extraction efficiency using toluene/phenyl boronic acid in a single stage. We show that the extraction procedure is compatible with acidic and basic xylose feed (from pH 1 to 12), does not need a phase transfer agent (such as Aliquat), is strongly selective for xylose, and proceeds best with aromatic solvents. We demonstrate the structure of the diboronate ester by means of 2D-NMR and show evidence for the intermediate formation of a monoboronate ester. The release of xylose from the diboronate ester is explored, and an integrated process for xylose purification is proposed and its boundaries are discussed.

Short polyols, such as ethylene glycol (EG), are a popular target of catalytic hydrogenolysis of saccharides. However, studies on the use of untreated or pretreated lignocellulosic biomass as feedstock for polyol production are scarce. In this work, we have studied the impact of lignin on the catalytic hydrogenolysis of different biomass samples, targeting ethylene glycol. We first developed a hydrogenolysis protocol that is sensitive to lignin and feedstock impurities, such as ash and extractives. A matrix of biomass feedstocks with varying lignin content has been evaluated, by subjecting poplar, pine, and hay to solvent-based (water/ethanol/acetic acid) pretreatments and by preparing physical mixtures of pure microcrystalline cellulose with organosolv lignin. Lignin appeared to inhibit the activity of the hydrogenation catalyst, Raney-Ni, by hindering the formation of sugar alcohols in the presence as well as in the absence of the tungstate catalyst. However, lignin is not the root cause for the low EG yield typically obtained with untreated lignocellulose, as treated lignocellulose delivered high EG yields (30-35 wt %), irrespective of the lignin concentrations, which varied between 0 and 44 wt %, under identical demanding experimental conditions.

BACKGROUND: Although phenol is a key intermediate in the plastics and polycarbonate industry, it is also a toxic component that requires removal from dilute aqueous streams, potentially by liquid–liquid extraction (LLX). For LLX, cumene is suggested as a solvent as it is already present in processes in the polycarbonate industry. For the recovery of cumene from phenol by distillation, knowledge on vapor–liquid equilibrium (VLE) behavior is important, in combination with how this is affected by other components possibly present as an impurity or explicitly added as a solvent. This was investigated in this work. RESULTS: The binary cumene–phenol system shows a tangent pinch in the binary VLE diagram. Addition of a range of impurities and solvents showed that hydrogen bond accepting compounds strongly improve the relative volatility of the mixture, whereas dodecane, not capable of forming hydrogen bonds, has a negative effect on the relative volatility. CONCLUSION: Addition of polar components with hydrogen bonding abilities, i.e. ketones or ethers, affected the relative volatility of cumene over phenol the most positively. Combining two types of components results in similar effects, and clear synergistic effects could not be shown based on current VLE measurements. Addition of an apolar component in combination with polar components with hydrogen abilities had only a minor effect on the relative volatility.

The flexible operation of alkaline water electrolyzers enables power-to-x plants to react efficiently to different energy scenarios. In this work, a novel scheduling model for alkaline water electrolysis is formulated as a mixed-integer linear program. The model is constructed by implementing operational states (production, standby, idle) and transitions (cold/full startup, shutdown) as integer variables, while the power loading and hydrogen flowrate are set as continuous variables. The operational characteristics (load range, startup time, ramp rates) are included as model constraints. The proposed model allows finding optimal number of electrolyzers and production schedules when dealing with large data sets of intermittent energy and electricity price. The optimal solution of the case study shows a balance between hydrogen production, energy absorption, and operation and investment costs. The optimal number of electrolyzers to be installed corresponds to 54% of the ones required to absorb the highest energy peak, being capable of loading 89.7% of the available energy during the year of operation, with an overall plant utilization of 93.7% and 764 startup/shutdown cycles evenly distributed among the units.

Different strategies for sewage sludge management have been implemented to minimize the environmental impacts and benefit from the resources embedded in this waste stream. In that regard, Hydrothermal treatments (HTTs) of biomass can contribute generating high-value products (hydrochar) and enhancing biogas generation. In this work, different strategies were analysed for implementing HTTs at WWTPs considering the effect of 2 different process temperatures (160 and 250 °C) on different sewage sludge samples (primary, secondary and digestate sludge). Determination of carbon, nitrogen and phosphorus fate and mass and energy balances in hydrochar and process waters were carried out. HTT promoted solubilization of nitrogen, phosphorus and organic carbon up to 89%, 13% and 124% respectively. Moreover, biomethane yield increased up to 168% reaching methane concentrations up to 79% in the biogas. High heating values of hydrochars ranged from 12.0 to 18.2 MJ kg−1. The integration of HTT as an intermediate step between two-step anaerobic digestion process showed an increase in the net energy balance of up to 124% in comparison with the conventional anaerobic digestion process. Graphical Abstract

Economic expedience of waste heat recovery systems (WHRS), especially for low temperature difference applications, is often questionable due to high capital investments and long pay-back periods. By its simple design isobaric expansion (IE) machines could provide a viable pathway to utilize otherwise unprofitable waste heat streams for power generation and particularly for pumping liquids and compression of gases. Different engine configurations are presented and discussed. A new method of modelling and calculation of the IE process and efficiency is used on IE cycles with various pure and mixtures as a working fluid. Some interesting cases are presented. It is shown in this paper, that the simplest non-regenerative IE engines are efficient at low temperature differences between a heat source and heat sink. Efficiency of non-regenerative IE process with pure working fluid can be very high approaching Carnot efficiency at low pressure and heat source/heat sink temperature differences. Regeneration permits to increase efficiency of the IE-cycle to some extent. Application of mixed working fluids in combination with regeneration permits to significantly increase the range of high efficiencies to much larger temperature and pressure differences.