Designing circular waste management strategies:The case of organic waste in Amsterdam

Urban waste management is one of the most complex and urgent challenges that the society faces. In this paper, an innovative research methodology is proposed, introducing a systemic approach to circular waste management strategy‐making. Urban waste management is a complex system that needs to be tackled in a holistic, yet context‐specific manner. To produce truly integrative outcomes, this paper provides insight into the system as a whole, its components and the relationships between them, using specific tools, to form the basis for a circular strategy. A toolbox is presented for transforming the current linear and fragmented waste management processes into integrative and circular strategies. The proposed integrative methodology encompassing outline, multipillar mapping, and synthesis can be applied to different locations and waste streams. The concept is subsequently demonstrated through a case study focusing on the municipality of Amsterdam (the Netherlands) and the management of organic waste streams

Understanding the solar-driven reduction of CO2 on doped ceria

With the appropriate materials, one can construct redox cycles that use CO2 as the oxidant, generating CO as the product. Here, we investigate thermochemical cycles using doped ceria compounds as the oxygen exchange medium. Doped samples are prepared using La, Cr, W, Zr, V, Y, and Ti as dopants. Studying the redox kinetics, we show that doping the pure ceria with zirconium strongly increases overall CO production, albeit at lower reaction rates. This is because the CO2 reduction step is second-order with respect to Ce(III). Doping the fluorite lattice with zirconium cations decreases the number of Ce(III) ions at the surface, and consequently slows down the reaction. This result is counter-intuitive, since normally you would think that the more reduction, the better. But the reactivity towards CO2 is actually determined by the surface Ce(III) ions, and so migration of dopant ions on the surface reduces its reactivity, even though the bulk Ce(III) concentration is higher. Our results demonstrate the importance of understanding surface kinetics when designing oxygen exchange materials for solar reactors.We thank the Dutch National Research School Combination Catalysis (NRSC-C) for funding

Titania-catalysed oxidative dehydrogenation of ethyl lactate: effective yet selective free-radical oxidation

We research here the catalytic oxidative dehydrogenation of ethyl lactate, as an alternative route to ethyl pyruvate. Testing various solid catalysts (Fe2O3, TiO2, V2O5/MgO–Al2O3, ZrO2, CeO2 and ZnO), we find that simple and inexpensive TiO2 efficiently catalyses this reaction under mild conditions. Furthermore, molecular oxygen was used as the terminal oxidant. Importantly, this reaction runs well also using inexpensive commercial solvent mixtures. Both the desired reaction and the by-products formation follow a free-radical mechanism. Remarkably, adding activated carbon, a solid radical scavenger, hardly affects the catalytic activity, but enhances the product selectivity. This is because this solid radical scavenger hampers the formation of undesired products in solution, without suppressing the oxidation at the catalyst surface

Silica-supported sulfonic acids as recyclable catalyst for esterification of levulinic acid with stoichiometric amounts of alcohols

Converting biomass into value-added chemicals holds the key to sustainable long-term carbon resource management. In this context, levulinic acid, which is easily obtained from cellulose, is valuable since it can be transformed into a variety of industrially relevant fine chemicals. Here we present a simple protocol for the selective esterification of levulinic acid using solid acid catalysts. Silica supported sulfonic acid catalysts operate under mild conditions and give good conversion and selectivity with stoichiometric amounts of alcohols. The sulfonic acid groups are tethered to the support using organic tethers. These tethers may help in preventing the deactivation of the active sites in the presence of water

Enhancing catalytic epoxide ring-opening selectivity using surface-modified Ti3C2Tx MXenes

MXenes are a new family of two-dimensional carbides and/or nitrides. Their 2D surfaces are typically terminated by O, OH and/or F atoms. Here we show that Ti3C2Tx—the most studied compound of the MXene family—is a good acid catalyst, thanks to the surface acid functionalities. We demonstrate this by applying Ti3C2Tx in the epoxide ring-opening reaction of styrene oxide (SO) and its isomerization in the liquid phase. Modifying the MXene surface changes the catalytic activity and selectivity. By oxidizing the surface, we succeeded in controlling the type and number of acid sites and thereby improving the yield of the mono-alkylated product to >80%. Characterisation studies show that a thin oxide layer, which forms directly on the Ti3C2Tx surface, is essential for catalysing the SO ring-opening. We hypothesize that two kinds of acid sites are responsible for this catalysis: In the MXene, strong acid sites (both Lewis and Brønsted) catalyse both the ring-opening and the isomerization reactions, while in the Mxene–TiO2 composite weaker acid sites catalyse only the ring-opening reaction, increasing the selectivity to the mono-alkylated product.TKS was supported by the NWO TOP-PUNT Catalysis in Confined Spaces (Grant 718.015.004). EVRF and ASE acknowledge financial support by MINECO (Spain) through the projects MAT2017-86992-R and MAT2016-80285-P. VN and MWB thank NSF DMR 1740795 for financial support

Surface oxidation of Ti3C2Tx enhances the catalytic activity of supported platinum nanoparticles in ammonia borane hydrolysis

MXenes, first discovered in 2011, are two-dimensional transition metal carbides or nitrides. Because of their interesting electrical and optical properties, they are studied for applications in batteries, supercapacitors and electrocatalysis. However, MXenes are rarely used in heterogeneous catalysis and, to our knowledge, there are no reports on the use of oxidized MXenes in catalysis. Here we used Ti3C2Tx-derived materials as supports for platinum nanoparticles and studied their effectiveness for the hydrolysis of ammonia borane, which is a promising hydrogen carrier. Hydrogen can be released from ammonia borane through catalytic hydrolysis. Most heterogeneous catalysts reported for this purpose contain a noble metal supported on a metal oxide support. The interaction between the metal and the support is important in determining the catalytic performance. Our results show that the electronic environment of platinum can be modified by oxidising the surface of MXene, thus providing a new way of developing active catalysts. Oxidising agents such as water and ozone can be used for this purpose. This electronic modification enhances the catalytic activity of platinum for ammonia borane hydrolysis, which is relevant for other reactions related to energy production/storage.T K S was supported by NWO TOP-PUNT grant 718.015.004. Z S was supported by project LTAUSA19034 from Ministry of Education Youth and Sports (MEYS). E V R F and A S E would like to thanks financial support by MINECO (Spain) through the projects MAT2017-86992-R and MAT2016-80285-P

CO2 Hydrogenation at Atmospheric Pressure and Low Temperature Using Plasma-Enhanced Catalysis over Supported Cobalt Oxide Catalysts

CO2 is a promising renewable, cheap, and abundant C1 feedstock for producing valuable chemicals, such as CO and methanol. In conventional reactors, because of thermodynamic constraints, converting CO2 to methanol requires high temperature and pressure, typically 250 °C and 20 bar. Nonthermal plasma is a better option, as it can convert CO2 at near-ambient temperature and pressure. Adding a catalyst to such plasma setups can enhance conversion and selectivity. However, we know little about the effects of catalysts in such systems. Here, we study CO2 hydrogenation in a dielectric barrier discharge plasma-catalysis setup under ambient conditions using MgO, γ-Al2O3, and a series of CoxOy/MgO catalysts. While all three catalyst types enhanced CO2 conversion, CoxOy/MgO gave the best results, converting up to 35% of CO2 and reaching the highest methanol yield (10%). Control experiments showed that the basic MgO support is more active than the acidic γ-Al2O3, and that MgO-supported cobalt oxide catalysts improve the selectivity toward methanol. The methanol yield can be tuned by changing the metal loading. Overall, our study shows the utility of plasma catalysis for CO2 conversion under mild conditions, with the potential to reduce the energy footprint of CO2-recycling processes

Butane Dry Reforming Catalyzed by Cobalt Oxide Supported on Ti2AlC MAX Phase

MAX (M(n+1)AX(n)) phases are layered carbides or nitrides with a high thermal and mechanical bulk stability. Recently, it was shown that their surface structure can be modified to form a thin non-stoichiometric oxide layer, which can catalyze the oxidative dehydrogenation of butane. Here, the use of a Ti2AlC MAX phase as a support for cobalt oxide was explored for the dry reforming of butane with CO2, comparing this new catalyst to more traditional materials. The catalyst was active and selective to synthesis gas. Although the surface structure changed during the reaction, the activity remained stable. Under the same conditions, a titania-supported cobalt oxide catalyst gave low activity and stability due to the agglomeration of cobalt oxide particles. The Co3O4/Al(2)O(3)catalyst was active, but the acidic surface led to a faster deactivation. The less acidic surface of the Ti2AlC was better at inhibiting coke formation. Thanks to their thermal stability and acid-base properties, MAX phases are promising supports for CO(2)conversion reactions

Molybdenum Oxide Supported on Ti3AlC2 is an Active Reverse Water−Gas Shift Catalyst

MAX phases are layered ternary carbides or nitrides that are attractive for catalysis applications due to their unusual set of properties. They show high thermal stability like ceramics, but they are also tough, ductile, and good conductors of heat and electricity like metals. Here, we study the potential of the Ti(3)AlC(2 )MAX phase as a support for molybdenum oxide for the reverse water-gas shift (RWGS) reaction, comparing this new catalyst to more traditional materials. The catalyst showed higher turnover frequency values than MoO3/TiO2 and MoO3/Al2O3 catalysts, due to the outstanding electronic properties of the Ti3AlC2 support. We observed a charge transfer effect from the electronically rich Ti3AlC2 MAX phase to the catalyst surface, which in turn enhances the reducibility of MoO3 species during reaction. The redox properties of the MoO3/Ti3AlC2 catalyst improve its RWGS intrinsic activity compared to TiO2- and Al2O3-based catalysts

Understanding the oxidative dehydrogenation of ethyl lactate to ethyl pyruvate over vanadia/titania

We studied the vapour-phase oxidative dehydrogenation (ODH) of ethyl lactate with air to give ethyl pyruvate over V2O5/TiO2 catalysts in a fixed-bed reactor. The nature of the vanadia species is changed by varying the vanadium surface density, and the corresponding structure of the VOx species was determined by XRD, UV-vis spectroscopy, XPS and H2-TPR. Monomeric and isolated vanadia species dominate at lower vanadium surface densities. As the surface density increases, two-dimensional polyvanadates and bulk-like vanadia crystallites become predominant. The activity per vanadium decreases with increasing vanadium surface density, indicating that the monomeric VOx species is better for pyruvate production and that the V–O–Ti bonds play an important role in the ODH of ethyl lactate. This is also confirmed by the superior catalytic performance of V2O5/TiO2 compared to vanadium supported on MgO, Al2O3, ZrO2 and CeO2. In situ DRIFT spectroscopy coupled with mass analysis shows that the reaction can involve three possible adsorption modes of ethyl lactate on the V2O5/TiO2 surface. Under anaerobic conditions, 2-hydroxypropionate forms, giving ethyl acetate as the major product. Conversely, under aerobic conditions, oxygen that is chemisorbed on V2O5/TiO2 is active and easily replenished from the gas phase, converting the ethyl-propionate-2-oxide intermediate into ethyl pyruvate.WZ thanks the China Scholarship Council for a PhD fellowship. EVRF thanks Generalitat Valenciana (project PROMETEOII/2014/004) and Ministerio de Economía y Competitividad (Spain) for projects MAT2013-45008-P, MAT2016-81732-ERC and RYC-2012-11427. This work is part of the Sustainable Chemistry Research Priority Area of the UvA (http://suschem.uva.nl)