Search

In this work, a comprehensive process simulation was developed to study and predict the pyrolysis of linear low-density polyethylene (LLDPE) in a fluidized bed reactor (FBR). The comprehensive simulation operated at 600 and 700 °C to investigate the pyrolytic oil and wax yields. These products were chosen as they mimic fuel range products available as a renewable fuel and energy source. The results showed that the oil yield decreased from 600 to 700 °C. This is because of an increase in the polyolefin polymer matrix’s vibration leading to an increase in temperature and absorbed thermal energy. In addition, there is a higher gas yield produced and negligible wax formation at 700 °C, which is beneficial in controlling accrued plastic waste (PW), of which polyethylene (PE) represents a vast proportion of via thermo-chemical conversion (TCC) technologies. The detailed process simulation was compared with experimental data under the same technology and operating conditions, and it was found that less than 10% discrepancy was observed between the two sets of data, suggesting a good validation between the two studies. Further studies showed that the diesel fuel lumped hydrocarbon (HC) range (C10-C19) was between 40 and 63% in the pyrolysis oil yield obtained. Moreover, the temperature profiles and fluidized bed distributor parameters were compared and investigated. The current simulation has proven that it can successfully predict the pyrolysis of LLDPE in an FBR.

The selective deoxygenation of palm oil to produce green diesel has been investigated over Ni catalysts supported on ZrO2 (Ni/Zr) and CeO2–ZrO2 (Ni/CeZr) supports. The modification of the support with CeO2 acted to improve the Ni dispersion and oxygen lability of the catalyst, while reducing the overall surface acidity. The Ni/CeZr catalyst exhibited higher triglyceride (TG) conversion and yield for the desirable C15–C18 hydrocarbons, as well as improved stability compared to the unmodified Ni/Zr catalyst, with TG conversion and C15–C18 yield remaining above 85% and 80% respectively during 20 h of continuous operation at 300 oC. The high C17 yields also revealed the dominance of the deCOx (decarbonylation/decarboxylation) pathway. A fully comprehensive process simulation model has been developed to validate the experimental findings in this study, and a very good validation with the experimental data has been demonstrated. The model was then further utilised to investigate the effects of temperature, H2 partial pressure, H2/oil feed ratio and LHSV. The model predicted that maximum triglyceride conversion was attainable at reaction conditions of 300 °C temperature, 30 bar H2 partial pressure, H2/oil of 1000 cm3/cm3 feed ratio and 1.2 h−1 LHSV., MAG and NDC gratefully acknowledge that this researched was co-financed by Greece and the European Union (European Social Fund-ESF) through the Operational Programme “Human Resources Development, Education and Lifelong Learning” (MIS-5050170). KP and SA acknowledge the financial support from the Abu Dhabi Department of Education and Knowledge through the grant AARE-2019-233 and the support from Khalifa University through the grant RC2-2018-024. VS acknowledges the ICTS ELECMI-LMA for offering access to their instruments and expertise.

Climate change, the greenhouse effect and fossil fuel extraction have gained a growing interest in research and industrial circles to provide alternative chemicals and fuel synthesis technologies. Carbon dioxide (CO2) hydrogenation to value-added chemicals using hydrogen (H-2) from renewable power (solar, wind) offers a unique solution. From this aspect this review describes the various products, namely methane (C-1), methanol, ethanol, dimethyl ether (DME) and hydrocarbons (HCs) originating via CO2 hydrogenation reaction. In addition, conventional reactor units for the CO2 hydrogenation process are explained, as well as different types of microreactors with key pathways to determine catalyst activity and selectivity of the value-added chemicals. Finally, limitations between conventional units and microreactors and future directions for CO2 hydrogenation are detailed and discussed. The benefits of such set-ups in providing platforms that could be utilized in the future for major scale-up and industrial operation are also emphasized.

Nanoparticles are being used in the CO2 solvents to improve the capture performance. Herein, a 2D model is proposed to study the CO2 capture performance from a gaseous mixture using a hollow fiber membrane contactor (HFMC). Both water-based nanofluids of carbon nanotubes (CNT) and SiO2 are deployed as the carbon absorbents. It is verified that Brownian motion and grazing effect are the major reasons to enhance the mass transfer of nanofluids. The simulation findings show that the modeling data conform well with the experimental studies. The root-mean-square errors for SiO2 nanofluid and CNT nanofluid are 2.37% and 2.56%, respectively. When the amounts of nanoparticles increase between 0.02 and 0.06 wt%, CO2 capture efficiencies of SiO2 and CNT nanofluids increase by 7.92% and 13.17%, respectively. Also, the CNT nanofluid has a better capture performance than the SiO2 nanofluid. Furthermore, research is conducted into how membrane characteristics affect HFMC performance. It is indicated that increasing the membrane porosity and decreasing the membrane tortuosity have a positive impact on the capture efficiency. This work demonstrates the potentials in the use of nanoparticles in CO2 solvents and provides a solid theoretical basis for nanofluids to significantly enhance gas absorption.

In response to the growing trend of greenhouse gas emissions from the production and use of conventional fuels, COx free hydrogen generation is introduced as an alternative and efficient energy carrier. Due to hydrogen's storage challenges, is more efficient to be produced on-site by other chemical compounds for fuel cell applications. This work outlines the production of hydrogen (H2) from ammonia (NH3) and hydrous hydrazine (N2H4·H2O) catalytic decomposition. Both substances are giving nitrogen (N2) as a by-product, which is not toxic. Moreover, heterogeneous catalysts that were studied through the years are presented. Lastly, a reactoristic view of the ammonia decomposition is provided with different reactors such as catalytic membrane reactors (CMRs), fixed-bed reactors (FBRs) and micro-reactors (MRs) for the evaluation of their performance.

Electronic waste (e-waste) has become one of the major causes of environmental concerns due to its large volume, high generation rate and toxic environmental burdens. Recent estimates put e-waste generation at about 54 million tonnes per annum with figures reaching approximately 75 million tonnes per annum by 2030. In this manuscript, the state-of-the-art technologies and techniques for segregation, recovery and recycling of e-waste with a special focus on the valorisation aspects of e-plastics and e-metals which are critically reviewed. A history and insight into environmental aspects and regulation/legislations are presented including those that could be adopted in the near future for e-waste management. The prospects of implementing such technologies in the State of Kuwait for the recovery of materials and energy from e-waste where infrastructure is lacking still for waste management are presented through Material Flow Analysis. The information showed that Kuwait has a major problem in waste accumulation. It is estimated that e-waste in Kuwait (with no accumulation or backlog) is generated at a rate of 67,000 tpa, and the imports of broadcasting electronics generate some 19,428 tonnes. After reviewing economic factors of potential recovered plastics, iron and glass from broadcasting devices in Kuwait as e-waste, a total revenue of $399,729 per annum is estimated from their valorisation. This revenue will open the prospect of ventures for other e-waste and fuel recovery options as well as environmental benefits and the move to a circular economy.

The need to replace fossil fuels with sustainable alternatives has been a critical issue in recent years. Hydrogen fuel is a promising alternative to fossil fuels because of its wide availability and high energy density. For the very first time, novel microreactor configurations for the formic acid decomposition have been studied using computational modeling methodologies. The decomposition of formic acid using a commercial 5 wt % Pd/C catalyst, under mild conditions, has been assessed in packed bed, coated wall, and membrane microreactors. Computational fluid dynamics (CFD) was utilized to develop the comprehensive heterogeneous microreactor models. The CFD modeling study begins with the development of a packed bed microreactor to validate the experimental work, subsequently followed by the theoretical development of novel microreactor configurations to perform further studies. Previous work using CFD modeling had predicted that the deactivation of the Pd/C catalyst was due to the production of the poisoning species CO during the reaction. The novel membrane microreactor facilitates the continuous removal of CO during the reaction, therefore prolonging the lifetime of the catalyst and enhancing the formic acid conversion by approximately 40% when compared to the other microreactor configurations. For all microreactors studied, the formic acid conversion increases as the temperature increases, and the liquid flow rate decreases. Further studies revealed that all microreactor configurations had negligible internal and external pore diffusion resistances. The detailed models developed in this work have provided an interesting insight into the intensification of the formic acid decomposition reaction over a Pd/C catalyst.

Plastics are abundant and have a high energy content making their use in energy applications attractive. This article presents a review on plastic waste (PW) management by pyrolysis and gasification, which are two types of thermochemical conversion (TCC) techniques. The conversion of PW and the application of its converted products are important steps toward reducing reliance on fossil fuels, enhancing closed-loop recycling of materials and the circular economy. The review presented herein also focuses on product distribution and yields with emphasis on the energy content and potential integration to energy systems and grids. It is found that pyro-oils have properties similar to conventional fuels such as diesel and can partially substitute for fossil fuels. In fact, the energy content of PW pyro-oils obtained by various researchers range from 41.10−46.16 MJ kg−1 , which is close to the heating values of conventional fuels and thus are potential candidates for fuel applications. Typical treatment post-conversion is also conducted to maintain the quality of the oil produced and the removal of sulfur content to conform with market standards. On the other hand, syngas produced during gasification possesses a lower potential for fuel applications as its energy content may reach values as low as 20 MJ kg−1 in comparison to pyro-oil. However, depending on the process conditions, it is possible to increase the energy content to values of over 40 MJ kg−1 . Additionally, syngas is the building block for many valuable chemicals. With appropriate treatment, the syngas obtained from the gasification of PW can be used in gas engines and can be converted to commercial products such as liquid fuels via the Fischer−Tropsch synthesis. This review also highlights some available commercial-scale plants for the TCC of PW and real-life application of their obtained products. It is noted that the integration of the processes to energy systems is technically and economically feasible. Real-life applications of products obtained from the pyrolysis and gasification of PW in different parts of the world are also discussed. The produced fuels have been used in cooking stoves and burned in a gas turbine, internal combustion engine, and direct injection diesel engine.

With fossil fuel being the major source of energy, CO2 emission levels need to be reduced to a minimal amount namely from anthropogenic sources. Energy consumption is expected to rise by 48% in the next 30 years, and global warming is becoming an alarming issue which needs to be addressed on a thorough technical basis. Nonetheless, exploring CO2 capture using membrane contactor technology has shown great potential to be applied and utilised by industry to deal with post- and pre-combustion of CO2. A systematic review of the literature has been conducted to analyse and assess CO2 removal using membrane contactors for capturing techniques in industrial processes. The review began with a total of 2650 papers, which were obtained from three major databases, and then were excluded down to a final number of 525 papers following a defined set of criteria. The results showed that the use of hollow fibre membranes have demonstrated popularity, as well as the use of amine solvents for CO2 removal. This current systematic review in CO2 removal and capture is an important milestone in the synthesis of up to date research with the potential to serve as a benchmark databank for further research in similar areas of work. This study provides the first systematic enquiry in the evidence to research further sustainable methods to capture and separate CO2.

End of life single-use items such as carrier bags constitute a large proportion of the litter found in marine and terrestrial environments. The main objective of the current work was to investigate the response of an oxo-biodegradable commercial plastic film product to photo-degradation using accelerated weathering, verifying the claim of its biodegradability and suitability as an eco-friendly product. This study is also geared towards the appropriateness of such products to reduce plastic waste accumulation in urban environments. The film samples were exposed to weathering as a means to determine the impact of UV induced oxo-biodegradation. Haze (%), light transmission (%) and the total change in colour (ΔE) were measured as indicators to the degradation profile of the polymeric materials, in addition to tensile pull mechanical properties and thermal stability. The melting peak indicates the melting point (Tm) of the polymer and with exposure to weathering it showed a slight decrease from 105 to 102 °C indicating that biodegradation mechanisms were triggered to a certain extent. The reduction in strain at rupture was also indicative for a loss in crystalline structure, coupled with Young’s modulus increase throughout the weathering exposure tests. Therefore, the material studied could be a candidate to mitigate the accumulation of plastic waste in open environments based on the results of this study whilst regulating controlled substances.

Microplastics (MPs) have been recognised as a persistent pollutant within environmental sinks, classed as a pollutant of priority in the Basel, Rotterdam and Stockholm (BRS) Conventions. In this work, we relate one of the longest COVID-19 recent pandemic lockdowns enforced in the State of Kuwait to the plastic waste generation and MPs accumulation which were released from a selected site known for leisure and fishing activities on the Northwestern part of the Arabian/Persian Gulf. After 15 days from the release, the coverage area was the widest for the distribution and transport plume of MPs. The particles were retained at known areas for fishing activities in Kuwait and were controlled by the hydrodynamics of the modelling configuration rather than the MPs release strength (i.e., number of particles). Moreover, during the period between January to April 2020; the MPs covered almost a double dispersed area which was linked to the hydrodynamics of the release model exercise. Generally, the most affected areas of the MPs distribution were along the Kuwait City coastline and the COVID-19 lockdown measures didn't affect the MPs particle distribution as much as environmental conditions.

Ni-based catalysts supported on sol-gel prepared Pr-doped CeO2 with varied porosity and nanostructure were tested for the CO2 methanation reaction. It was found that the use of ethylene glycol in the absence of H2O during a modified Pechini synthesis led to a metal oxide support with larger pore size and volume, which was conducive toward the deposition of medium-sized Ni nanoparticles confined into the nanoporous structure. The high Ni dispersion and availability of surface defects and basic sites acted to greatly improve the catalyst’s activity. CFD simulations were used to theoretically predict the catalytic performance given the reactor geometry, whereas COMSOL and ASPEN software were employed to design the models. Both modelling approaches (CFD and process simulation) showed a good validation with the experimental results and therefore confirm their ability for applications related to the prediction of the CO2 methanation behaviour., AIT, NDC and MAG acknowledge support of this work by the project “Development of new innovative low carbon energy technologies to improve excellence in the Region of Western Macedonia” (MIS 5047197), which is implemented under the Action “Reinforcement of the Research and Innovation Infrastructure” funded by the Operational Program "Competitiveness, Entrepreneurship and Innovation" (NSRF 2014–2020) and co-financed by Greece and the European Union (European Regional Development Fund). AGSH, AAD and KP acknowledge support from Khalifa University through the grant RC2–2018-024. Additional partial support has been provided by the Abu Dhabi Award for Research Excellence (AARE) 2019 through project AARE19–233. VS acknowledges the ICTS ELECMI-LMA for offering access to their instruments and expertise.

The use of hydrogen as a renewable fuel has attracted great attention in recent years. The decomposition of formic acid under mild conditions was investigated using a 2%Pd6Zn4 catalyst in a batch reactor. The results showed that the conversion of formic acid increases with reaction temperature and with the formic acid concentration. A process-simulation model was developed to predict the decomposition of formic acid using 2%Pd6Zn4 in a batch reactor. The model demonstrated very good validation with the experimental work. Further comparisons between the 2%Pd6Zn4 catalyst and a commercial Pd/C catalyst were carried out. It was found that the 2%Pd6Zn4 demonstrated significantly higher conversions when compared with the commercial catalyst., The authors thank London South Bank University; School of Engineering for the PhD fund that supports the work of Sanaa Hafeez.

Carbon dioxide (CO2) is one of the major atmospheric greenhouse gases (GHG). The continuous increase of CO2 concentration and its long atmospheric lifetime may cause long-term negative effects on the climate. It is important to develop technologies to capture and minimize those emissions into the atmosphere. The objective of this work is to design and study theoretically and experimentally a numbering-up/scale-out membrane microreactor in order to be used as a capture system. The main aim of the work is to obtain an even flow distribution at each plate of the reactor. Nearly uniform flow distribution was achieved at each layer of the numbering-up microreactor according to the carried-out CFD models. The maximum difference between the average velocities was less than 6% for both gas and liquid flows. To obtain better flow distribution into the microreactor, the radius of the inlet/outlet tube was optimized. Results from CFD and experimental simulations do not match, and slightly maldistribution in achieved in the experimental system due to phase breakthrough and imperfections on the fabrication of the plates. Moreover, comparing the single channel microreactor to the scale-out microreactor, the latter showed poorer performance on CO2 removal while expecting the reactors to have similar performance. By installing inserts with different channel widths, the experimental results were identical to the original case.

A computational fluid dynamics (CFD) model was derived and validated in order to investigate the hydrodeoxygenation reaction of 4-propylguaiacol, which is a lignin-derived compound present in bio-oil. A 2-D packed bed microreactor was simulated using a pre-sulphided NiMo/Al2O3 solid catalyst in isothermal operation. A pseudo-homogeneous model was first created to validate the experimental results from the literature. Various operational parameters were investigated and validated with experimental data, such as temperature, pressure and liquid flow rate, and it was found that the CFD findings were in very good agreement with the results from the literature. The model was then upgraded to that of a detailed multiphase configuration, and phenomena such as internal and external mass transfer limitations were investigated, as well as reactant concentrations on the rate of 4-propylguaiacol. Both models were in agreement with the experimental data, and therefore confirm their ability for applications related to the prediction of the behaviour of bio-oil compound hydrodeoxygenation.

The year 2020 has been noted to be one of major calamity the world over, in which the majority of efforts in research and development have been dedicated towards combating the threat of the novel Coronavirus (COVID-19). Ever since the announcement of COVID-19 as a pandemic, such efforts were dedicated towards the research of its spread and vaccination. Yet still, the world might reach a resolution via an environmental solution that various entities have overlooked, with a plethora of environmental benefits vis-à-vis waste management. In this short communication, the possibility of using plastic solid waste as a substrate to employ copper, and copper alloys and their nanocomposite nanopowders to be used as permanent surface protective coats, is presented. The fact that we present such materials to be of waste origin, is an added value advantage to their beneficial advantage of developing various commodities and products that could be used in our daily lives. Furthermore, the fact that such recyclable materials are susceptible to antiviral properties and chemicals, is an added value that we should not neglect.

For the first time, a fully comprehensive heterogeneous computational fluid dynamic (CFD) model has been developed to predict the selective catalytic deoxygenation of palm oil to produce green diesel over an Ni/ZrO2 catalyst. The modelling results were compared to experimental data, and a very good validation was obtained. It was found that for the Ni/ZrO2 catalyst, the paraffin conversion increased with temperature, reaching a maximum value (&gt, 95%) at 300 °C. However, temperatures greater than 300 °C resulted in a loss of conversion due to the fact of catalyst deactivation. In addition, at longer times, the model predicted that the catalyst activity would decline faster at temperatures higher than 250 °C. The CFD model was able to predict this deactivation by relating the catalytic activity with the reaction temperature.

Smart Separations Limited (SSL) is a UK-based start-up who have developed a ceramic membrane with micron-sized conical pores distinct to the cylindrical pores typically used for filtration. This new technology has the potential to be highly beneficial to many applications. However to realize its potential, a comprehensive analysis of the performance and efficiency of the membrane is vital. We use mathematical modelling to explore and quantify the behaviour and performance of the membrane and its link to the underlying pore structure. We derive a reduced model based on the slenderness of the membrane pores that allows us to predict the flux through the membrane, the optimal pore shape that maximizes the amount of contaminant that is trapped. The outcomes of this work provide a first step to providing the key modelling insight that will allow SSL to take this new technology to market.

The use of hydrogen as a renewable fuel has gained increasing attention in recent years due to its abundance and efficiency. The decomposition of formic acid for hydrogen production under mild conditions of 30 °C has been investigated using a 5 wt.% Pd/C catalyst and a fixed bed microreactor. Furthermore, a comprehensive heterogeneous computational fluid dynamic (CFD) model has been developed to validate the experimental data. The results showed a very good agreement between the CFD studies and experimental work. Catalyst reusability studies have shown that after 10 reactivation processes, the activity of the catalyst can be restored to offer the same level of activity as the fresh sample of the catalyst. The CFD model was able to simulate the catalyst deactivation based on the production of the poisoning species CO, and a sound validation was obtained with the experimental data. Further studies demonstrated that the conversion of formic acid enhances with increasing temperature and decreasing liquid flow rate. Moreover, the CFD model established that the reaction system was devoid of any internal and external mass transfer limitations. The model developed can be used to successfully predict the decomposition of formic acid in microreactors for potential fuel cell applications.

The motivation for this work stems from the increased number of high-rise buildings/skyscrapers all over the world, and in London, UK, and hence the necessity to see their effect on the local environment. We concentrate on the mean velocities, Reynolds stresses, turbulent kinetic energies (TKEs) and tracer concentrations. We look at their variations with height at two main locations within the building area, and downstream the buildings. The pollution source is placed at the top of the central building, representing an emission from a Combined Heat and Power (CHP) plant. We see how a tall building may have a positive effect at the lower levels, but a negative one at the higher levels in terms of pollution levels. Mean velocities at the higher levels (over 60 m in real life) are reduced at both locations (within the building area and downstream it), whilst Reynolds stresses and TKEs increase. However, despite the observed enhanced turbulence at the higher levels, mean concentrations increase, indicating that the mean flow has a greater influence on the dispersion. At the lower levels (Z &lt, 60 m), the presence of a tall building enhanced dispersion (hence lower concentrations) for many of the configurations.

CO2 absorption in solutions of sodium hydroxide (NaOH) was performed in three membrane/mesh microstructured contactors: a single-channel polytetrafluoroethylene (PTFE) membrane contactor, a nickel mesh contactor and an eight-channel PTFE membrane contactor. A membrane/mesh was used to achieve gas/liquid mass transfer without dispersion of one phase within the other. The PTFE membrane consisted of a pure PTFE layer 20 μm thick laminated onto a polypropylene (PP) layer of 80 μm thickness. The pure PTFE layer contained pores of ~0.5 to 5 μm diameter and was hydrophobic, while the PP layer consisted of rectangular openings of 0.8 mm×0.324 mm and was hydrophilic. The nickel mesh was 25 μm thick and contained pores of 25 μm diameter and was hydrophilic. Experiments were performed with a 2 m NaOH solution and an inlet feed of 20 vol % CO2/N2 gas mixture. Numerical simulations matched reasonably well the experimental data. CO2 removal efficiency increased by increasing the NaOH concentration, the gas residence time and the exchange area between gas and liquid. Higher removal of CO2 was achieved when the PP was in the gas side rather than in the liquid side, due to lower mass transfer resistance of the gas phase. For the same reason, CO2 removal efficiency was higher for the eight-channel PTFE contactor compared to the nickel mesh contactor. Average CO2 flux was higher for the eight-channel contactor (8×10−3 mol/min·cm2 with PP on the gas side) compared to the nickel mesh contactor (3×10−3 mol/min·cm2) for the same gas and liquid residence times. The eight-channel PTFE membrane contactor removed around 72% of CO2 in 1.2 s gas residence time, demonstrating the potential for CO2 absorption using flat membrane contactors.

The demand for energy is continuously increasing worldwide. This places a constant strain on the production and availability of fossil fuels on which most current energy sources are based. Thus, alternative sources of energy (non-fossil based) are urgently needed to produce liquid fuels. However, conventional technologies and reactors used for these alternative processes have been associated with low mass and heat transfer rates, long reaction times and extreme temperatures and pressures. To address these limitations, microreactors have been developed and utilised over the past decade, and have been proven to increase product yields and reduce residence time and product selectivity when compared to conventional reactors. This paper provides an in-depth review of the liquid fuel production routes over the last decade, and highlights the advantages of microreactors that have been successfully employed to overcome some of the issues faced with conventional bulk reactors.

Population growth has led to higher consumption of fossil fuel, and subsequently to a major increase of greenhouse gases emissions to the atmosphere, thus inducing global warming. Fossil fuel supplies are depleting, and the price of these fuels is increasing. Moreover, there are concerns about related emissions of toxic pollutants such as sulphur dioxide and aromatic hydrocarbons. Here, we review alternative fuel technologies. We focus on how membrane reactors improve the existing production processes of renewable fuels. Advantages and environmental benefits of membrane reactors are compared to the conventional techniques. Membrane reactors have been applied successfully to improve biodiesel, hydrogen and Fischer–Tropsch synthesis. Membranes help the conversion of products, whilst shifting the equilibrium of the reaction and reducing undesired by-products. Membrane reactors also overcome immiscibility issues that hinder conventional reactor processes. Overall, membrane reactors reduce cost and energy needed for the treatment of wastewater from fuel production. Funding text The authors would like to thank London South Bank University, School of Engineering, for the PhD funding support.

In this communication, we discuss various production methods as potential venues targeted towards alternative fuel generation. These will revolve around the Fischer–Tropsch (FT) process and biodiesel and hydrogen generation techniques. The implementation of membrane reactors in the production of fuels will be shown and discussed; and their advantages will be detailed. The main routes of hydrogen production are also detailed, which include autothermal reforming and biological process. This was done to compare the main advantages of various techniques for the production of hydrogen, as it is noted to be the most desired utility fuel that can serve various purposes. The application of membranes also facilitates an increase in the conversion of desired products while shifting the equilibrium of the reaction and reducing undesired by-products. Membrane reactors also overcome immiscibility issues that hinder conventional reactor processes. Membrane reactors are also demonstrated to reduce the difficulty in separating and purifying impurities, as they couple separation and reaction in one process. This shows drastic economic and energy requirement reductions in the amount of wastewater treatment associated with conventional fuel production reactor. Emphasis is also paid to catalytic membranes used for the production of biodiesel, which can also remove glycerol from the product line as an added advantage.

© 2018, The Author(s). A catalytic membrane reactor with a Au–Pd catalyst, impregnated at the inner side of the membrane, was studied in the catalytic oxidation of benzyl alcohol in flow. The reactor comprised of four concentric sections. The liquid substrate flowed in the annulus created by an inner tube and the membrane. The membrane consisted of 3 layers of α-alumina and a titania top layer with 5 nm average pore size. Oxygen was fed on the outer side of the membrane, and its use allowed the controlled contact of the liquid and the gas phase. Experiments revealed excellent stability of the impregnated membrane and selectivities to benzaldehyde were on average > 95%. Increasing the pressure of the gas phase and decreasing liquid flowrates and benzyl alcohol concentration resulted in an increased conversion, while selectivities to benzaldehyde remained constant and in excess of 95%. ispartof: TOPICS IN CATALYSIS vol:62 issue:17-20 pages:1126-1131 ispartof: location:ENGLAND, Abingdon status: published

Industrial solid waste management encompasses a vital part of developed and developing countries strategies alike. It manages waste generated from vital industries and governs the hazardous waste generated as a major component of integrated waste management strategies. This article reviews the practices that govern the management approaches utilized in the developed world for industrial spent catalysts. It critically assesses the current situation of waste management within the developing world region focusing on the industrial waste component, in a novel attempt to crucially develop a strategy for a way forward based on best practices and future directions with major European industries. The review also draws parallels with European countries to compare their practices with those of the State of Kuwait, which rely solely on landfilling for the management of its industrial waste. Spent catalysts recovery methods are discussed at length covering conventional methods of valuable metals and chemicals recovery (e.g., hydrometallurgical, solid–liquid and liquid–liquid extraction) as well as biological recovery methods. A major gap exists within regulations that govern the practice of managing industrial waste in Kuwait, where it is essential to start regulating industries that generate spent catalysts inview of encouraging the establishment of valorization industries for metal and chemical recovery. This will also create a sustainable practice within state borders, and can reduce the environmental impact of landfilling such waste in Kuwait. Industrial solid waste management encompasses a vital part of developed and developing countries strategies alike. It manages waste generated from vital industries and governs the hazardous waste generated as a major component of integrated waste management strategies. This article reviews the practices that govern the management approaches utilized in the developed world for industrial spent catalysts. It critically assesses the current situation of waste management within the developing world region focusing on the industrial waste component, in a novel attempt to crucially develop a strategy for a way forward based on best practices and future directions with major European industries. The review also draws parallels with European countries to compare their practices with those of the State of Kuwait, which rely solely on landfilling for the management of its industrial waste. Spent catalysts recovery methods are discussed at length covering conventional methods of valuable metals and chemicals recovery (e.g., hydrometallurgical, solid-liquid and liquid-liquid extraction) as well as biological recovery methods. A major gap exists within regulations that govern the practice of managing industrial waste in Kuwait, where it is essential to start regulating industries that generate spent catalysts in-view of encouraging the establishment of valorization industries for metal and chemical recovery. This will also create a sustainable practice within state borders, and can reduce the environmental impact of landfilling such waste in Kuwait.

The increasing manufacturing of plastics increases the waste streams generated. The most popular way to treat the plastic that cannot be recycled is to use energy recovery methods or to landfill the waste. As plastic is non-biodegradable, landfilling causes vast environmental problems and therefore waste polymer energy recovery technique are of great importance. Pyrolysis has advantages as all mixed plastics can be reduced back to petrochemicals. Fluidized beds have useful characteristics for energy recovery. They have an economic advantage in industrial operations due to low maintenance costs compared to other reactors. Fluidizing beds provide flexibility in the operation that makes it possible to use various fluidizing agents and process conditions. Fluidizing beds were identified to be the best reactors for the catalytic plastic pyrolysis as they provide large contact surface for the reaction to happen. The fluidizing beds have some limitations; the bed particles can erode the walls of the vessels and the beds are sensitive to fibres, high amounts of metals and fillers. Long term stable operation of the fluidized bed can worsen the quality of the fluidization and some operation conditions may cause defluidization. The paper reviewed the use of fluidization for energy recovery, discussed its advantages and limitations. The fluidizing beds are promising reactors for the energy recovery due to the flexibility of the operation. However, further investigation is required to understand and improve the quality of fluidization, ways to avoid defluidization and parameters affecting the performance of the fluidized beds for the energy recovery

A flat Teflon AF-2400 membrane microchannel reactor was experimentally and theoretically investigated for aerobic oxidation of benzyl alcohol on a 5 wt% Ru/Al2O3 catalyst. The reactor consisted of gas and liquid channels (75 mm (L) × 3 mm (W) × 1 mm (D)), separated by a 0.07 mm thick semipermeable Teflon AF-2400 flat membrane, which allowed continuous supply of oxygen during the reaction and imultaneously avoided direct mixing of gaseous oxygen with organic reactants. A catalyst stability test was first carried out, and the experimental data obtained were used to estimate the kinetics of benzyl alcohol oxidation with a 2D reactor model. Using these kinetics, predictions from the 2D reactor model agreed well with the experimental data obtained at different liquid flow rates and oxygen pressures. The mass transfer and catalytic reaction in the membrane microchannel reactor were then theoretically studied by changing the membrane thickness, the liquid channel depth, and the reaction rate coefficient. Oxygen transverse mass transport in the catalyst bed was found to be the controlling process for the system investigated, and decreasing the liquid channel depth is suggested to improve the oxygen supply and enhance the benzyl alcohol conversion in the membrane reactor.

Plastic plays an important role in our daily lives due to its versatility, light weight and low production cost. Plastics became essential in many sectors such as construction, medical, engineering applications, automotive, aerospace, etc. In addition, economic growth and development also increased our demand and dependency on plastics which leads to its accumulation in landfills imposing risk on human health, animals and cause environmental pollution problems such as ground water contamination, sanitary related issues, etc. Hence, a sustainable and an efficient plastic waste treatment is essential to avoid such issues. Pyrolysis is a thermo-chemical plastic waste treatment technique which can solve such pollution problems, as well as, recover valuable energy and products such as oil and gas. Pyrolysis of plastic solid waste (PSW) has gained importance due to having better advantages towards environmental pollution and reduction of carbon footprint of plastic products by minimizing the emissions of carbon monoxide and carbon dioxide compared to combustion and gasification. This paper presents the existing techniques of pyrolysis, the parameters which affect the products yield and selectivity and identify major research gaps in this technology. The influence of different catalysts on the process as well as review and comparative assessment of pyrolysis with other thermal and catalytic plastic treatment methods, is also presented.

The city of London, UK, has seen in recent years an increase in the number of high-rise/multi-storey buildings (“skyscrapers”) with roof heights reaching 150 m and beyond, with the Shard being a prime example with a height of ∼310 m. This changing cityscape together with recent plans of local authorities of introducing Combined Heat and Power Plant (CHP) led to a detailed study in which CFD and wind tunnel studies were carried out to assess the effect of such high-rise buildings on the dispersion of air pollution in their vicinity. A new, open-source simulator, FLUIDITY, which incorporates the Large Eddy Simulation (LES) method, was implemented; the simulated results were subsequently validated against experimental measurements from the EnFlo wind tunnel. The novelty of the LES methodology within FLUIDITY is based on the combination of an adaptive, unstructured, mesh with an eddy-viscosity tensor (for the sub-grid scales) that is anisotropic. The simulated normalised mean concentrations results were compared to the corresponding wind tunnel measurements, showing for most detector locations good correlations, with differences ranging from 3% to 37%. The validation procedure was followed by the simulation of two further hypothetical scenarios, in which the heights of buildings surrounding the source building were increased. The results showed clearly how the high-rise buildings affected the surrounding air flows and dispersion patterns, with the generation of “dead-zones” and high-concentration “hotspots” in areas where these did not previously exist. The work clearly showed that complex CFD modelling can provide useful information to urban planners when changes to cityscapes are considered, so that design options can be tested against environmental quality criteria. This study shows how the presence of tall buildings affects the dispersion of air pollutants within a small neighbourhood, and how concentration hotspots can be generated in areas which were previously pollution- free.

Stripping of acetone from water utilizing nitrogen as a sweeping gas in co-current flow was conducted in a microfabricated glass/silicon gas-liquid contactor. The chip consisted of a microchannel divided into a gas and a liquid chamber by 10 μm diameter micropillars located next to one of the channel walls. The channel length was 35 mm, the channel width was 220 μm and the microchannel depth 100 μm. The micropillars were wetted by the water/acetone solution and formed a 15 μm liquid film between them and the nearest channel wall, leaving a 195 μm gap for gas flow. In addition, acetone stripping was performed in a microchannel membrane contactor, utilizing a hydrophobic PTFE membrane placed between two microstructured acrylic plates. Microchannels for gas and liquid flows were machined in the plates and had a depth of 850 μm and 200 μm respectively. In both contactors the gas/liquid interface was stabilized: in the glass/silicon contactor by the hydrophilic micropillars, while in the PTFE/acrylic one by the hydrophobic membrane. For both contactors separation efficiency was found to increase by increasing the gas/liquid flow rate ratio, but was not affected when increasing the inlet acetone concentration. Separation was more efficient in the microfabricated contactor due to the very thin liquid layer employed.

© 2018 The Royal Society of Chemistry. Molecular oxygen is without doubt the greenest oxidant for redox reactions, yet aerobic oxidation is one of the most challenging to perform with good chemoselectivity, particularly on an industrial scale. This collaborative review (between teams of chemists and chemical engineers) describes the current scientific and operational hurdles that prevent the utilisation of aerobic oxidation reactions for the production of speciality chemicals and active pharmaceutical ingredients (APIs). The safety aspects of these reactions are discussed, followed by an overview of (continuous flow) reactors suitable for aerobic oxidation reactions that can be applied on scale. Some examples of how these reactions are currently performed in the industrial laboratory (in batch and in flow) are presented, with particular focus on the scale-up strategy. Last but not least, further challenges and future perspectives are presented in the concluding remarks. crosscheck: This document is CrossCheck deposited identifier: Simon Kuhn (ORCID) copyright_licence: The Royal Society of Chemistry has an exclusive publication licence for this journal copyright_licence: This article is freely available. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence (CC BY 3.0) history: Received 30 August 2016; Accepted 13 September 2016; Advance Article published 22 September 2016; Version of Record published 22 November 2016 ispartof: Reaction Chemistry & Engineering vol:1 issue:6 pages:595-612 status: published

CO 2 absorption in sodium hydroxide and diethanolamine solutions was investigated in a silicon nitride mesh contactor. Mesh contactors allow two phases to come into direct contact with each other, for the purpose of mass transfer between them without dispersing one phase into the other. The 1 μm thick silicon nitride mesh, containing a high density of uniform 0.5 μm pores, facilitated the stabilization of the gas liquid interface at its pores. Experimental results were obtained for 2 M NaOH or 2 M DEA solutions and 20% vol. CO 2 /N 2 inlet concentrations, with a fixed inlet molar ratio CO 2 :NaOH of 0.4. Results showed that 23% of the CO 2 contained in the inlet stream was removed within 0.5 s experimental gas residence time. CO 2 removal efficiency was higher when NaOH was used for absorption as compared to DEA. Experiments were also conducted with different mesh/membrane contactors: a PTFE membrane (thickness 20 μm, pore size 0.5–5 μm), a Ni-25 mesh (thickness 25 μm, pore size 25 μm) and a Ni-5 mesh (thickness 5 μm, pore size 5 μm). The silicon nitride mesh demonstrated the best performance primarily due to its small thickness.

Stripping of acetone from isopropanol utilizing nitrogen as a sweeping gas was conducted in gas/liquid contactors with slit type microchannels and containing flat sheet, metal and Teflon tortuous pore membranes or microfabricated metal meshes with straight pores. The contactor consisted of parallel metal plates, gaskets, and the membrane or the microstructured mesh so that passages for gas and liquid phases were formed. These slit type microchannels were 200 μm thick for both gas and liquid phases. All the membranes/meshes were wetted by the isopropanol solution. Breakthrough of one phase into the other was successfully described if contortion of the gas/liquid interface was considered at the pore ends. Various conditions during acetone stripping were investigated such as membrane type, gas and liquid flowrates and inlet acetone concentration. A contactor employing a Micro-Etch metal mesh with 76 μm openings and thickness of 50 μm offered the lowest mass transfer resistance and resulted to the best acetone stripping performance. The separation efficiency increased by increasing the gas/liquid flowrate ratio, but was not affected when increasing the inlet acetone concentration. Good agreement between the experiments and an one-dimensional model with no adjustable parameters was observed.

Carbon dioxide absorption in sodium hydroxide solution was studied in a metal mesh microstructured reactor. The reactor comprised of a microstructured metal mesh placed between two acrylic plates. Channels were machined in the plates with 0.85 mm and 0.2 mm depth forming the areas where gas and liquid flowed, respectively. The reactor was 192 mm × 97 mm (length × width). Experimental data were obtained for 2 M NaOH and 20 vol % CO2 inlet concentrations, for various liquid and gas flow rates, while keeping the molar flow rate ratio CO2/NaOH at 0.6. Results showed that in less than 1.2 s gas residence time approximately 30% of the carbon dioxide was removed. A two-dimensional model of the reactor where the solid area of the mesh was neglected and its percentage open area was used to modify the effective length of the reactor (segregated model) was formulated. This model's predictions gave better agreement with the experimental results compared to a pseudohomogeneous model where the diffusivities in the mesh were approximated with effective diffusivities based on mesh percentage open area. The model indicated that carbon dioxide was consumed within a short distance from the gas-liquid interface and the main mass transfer resistance was located in the mesh. Increasing the open area of the mesh increases CO2 removal as observed both theoretically and experimentally.

© 2015 American Chemical Society. A Teflon AF-2400 tube-in-tube microreactor is investigated for the continuous, solvent-free, catalytic oxidation of benzyl alcohol with oxygen. The semipermeable Teflon AF-2400 tube acts as the interface between the gaseous oxidant and the liquid substrate. Because of the inherent safety of this contacting method, the use of pure oxygen is possible. The semipermeable tube was packed with 1 wt % Au-Pd/TiO2 catalyst particles and placed inside a PTFE tube to provide an annular region which was pressurized with pure oxygen. This design allowed continuous penetration of oxygen through the inner tube during the reaction, resulting in higher oxygen concentration in the catalyst bed and significantly improved conversion compared to a reactor operating with an oxygen presaturated feed. The amount of oxygen available for reaction in the tube-in-tube microreactor was 2 orders of magnitude higher than that in a nonpermeable reactor with oxygen presaturated feed. The semipermeable tube reactor performance in terms of both conversion and selectivity was enhanced by increasing the gas pressure, the catalyst contact time and by dilution of the catalyst. The highest conversion of benzyl alcohol obtained for the range of conditions investigated was 44.1%, with 73.0% selectivity to benzaldehyde, at 120 °C; catalyst contact time, 115 gcat·s/galcohol; and catalyst dilution factor, 4. ispartof: Industrial & Engineering Chemistry Research vol:54 issue:16 pages:4183-4189 status: published

Absorption of carbon dioxide (CO2) in aqueous solutions of monoethanolamine (MEA) and diethanolamine (DEA) was performed in a flat membrane microstructured contactor. The contactor had dimensions 192 mm × 97 mm (length × width). Liquid and gas flowed in channels of 0.2 mm and 0.85 mm depth, respectively, separated by a supported polytetrafluoroethylene (PTFE) membrane of 20 μm thickness containing 0.5-5 μm openings. The function of the membrane was to bring into direct contact the two phases (gas and liquid) without dispersing one phase into the other. Experiments were conducted with 1.6 M MEA and 1.6 M DEA solutions and 20 vol% CO2/N2 inlet concentration, with a fixed inlet molar ratio CO2/amine of 0.5 at room temperature. Substantial CO2 absorption was observed for gas residence time below 0.2 s. A mathematical model with no adjustable parameters was used to simulate the contactor, and experimental results were compared to model predictions in terms of CO2 removal efficiency. The model showed satisfactory agreement with experimental data. Both model and experimental results showed that MEA solution absorbed more CO2 than DEA. CO2 removal increased by increasing the contact area between gas and liquid, using an 8-channel PTFE membrane microstructured contactor.

The ozonolysis of several organic substrates to give carbonyl compounds, carboxylic acids and nicotinic acids in flow using a standard lab-scale flow system equipped with a cooled flow cell was examined. Alkyl and aryl alkenes showed good conversion (49-99%) to the corresponding aldehydes and ketones utilising an "in flow" quench of triphenylphosphine. The ozonolysis of either 2 or 3-substituted furans obtained furnished a variety of carboxylic acids including the pharmaceutically important oxetane-3-carboxylic acids in two steps from furan and oxetan-3-one. Substituted benzoic acids were generated with high yields in two steps from aryl iodides. The non-selective ozonolysis of quinolines is known to give 2,3-dicarbonyl substituted pyridines, herein we report the selective ozonolysis of 8-hydroquinoline to give 3-[(1E)-3-oxoprop-1- en-1-yl]pyridine-2-carboxylic acid using flow techniques.