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During the past two decades, new insights have driven the development and optimization of aminated materials as aldol condensation catalysts. Amines, either primary or secondary, facilitate the reaction via an enamine mechanism. If the spatial placement with respect to the amine allows it, weak acid sites such as silanols or hydroxyls, can cooperate as hydrogen bond donors and aid in proton transfer steps. Furthermore, the reaction environment, i.e., support and solvent and their mutual interactions, is also a key determining factor. In particular, co-feeding small amounts of water suppresses the formation of inhibiting and site-blocking species. However, silica-based materials are susceptible to hydrolysis. This led to the development of water tolerant (bio)polymer supported amine catalysts which also exhibit selective component enrichment properties, opening up opportunities for further catalyst development. [ABSTRACT FROM AUTHOR]

The development of cost effective and environmentally benign adsorbents for arsenic removal is absolutely required due to arsenic contamination of water sources in many regions around the globe. The use of materials which are locally available in the affected regions is important for successful implementation of the developed technologies in rural areas. In this regard, we treated volcanic rocks (red scoria and pumice) locally available in Ethiopia with an aluminum sulphate solution and evaluated these materials for their capacity to remove As(V) from aqueous systems. The adsorbents were characterized using ICP-OES, EDX, SEM and BET. The experimental sorption data fitted well a Freundlich isotherm and the pseudo-second-order model was found to be more suitable than the pseudo-first-order model to describe the adsorption kinetics. The Langmuir maximum adsorption capacity was 0.18 mg/g for aluminum-treated red scoria (Al-Rs) and 2.68 mg/g for aluminum-treated pumice (Al-Pu). The effect of pH, adsorbent dose, initial As(V) concentration and interfering ions on arsenic adsorption were studied. The leaching of aluminum from the adsorbent during the adsorption process was also investigated. Results of column experiments indicated that Al-Pu is suitable to treat low concentration of As(V) contaminated water. The Al-Pu adsorbent is recyclable with only about 9% loss of its original efficiency after the 3 rd adsorption cycle (99.5%–90.2%). The data obtained from both batch and column studies indicate that Al-Rs and Al-Pu remove As(V) effectively from aqueous systems, with the latter being more efficient. [ABSTRACT FROM AUTHOR]

Highlights: [•] Resin swelling determines active site accessibility and, hence, catalytic activity. [•] Gel resins outperform macroporous ones in ethyl acetate transesterification with methanol. [•] The kinetic model implicitly accounts for swelling by assuming full active site coverage. [•] Protonated ethyl acetate reaction with bulk methanol is rate determining. [•] The selected Eley–Rideal mechanism is independent of the resin used. [ABSTRACT FROM AUTHOR]

Abstract: The reaction kinetics of the liquid-phase transesterification of ethyl acetate with methanol to methyl acetate and ethanol have been investigated in a temperature range from 303.15K to 333.15K as a model reaction for the transesterification of triglycerides in the production of biodiesel. The reaction has been catalyzed by the acidic ion-exchange resin Lewatit K1221. The effect of the initial reactant molar ratio and the temperature on the reaction kinetics was investigated and kinetic models, based on pseudo-homogeneous (PH), Eley–Rideal (ER) and Langmuir–Hinshelwood (LH) mechanisms, were used to describe the reaction rate. Because of the pronounced non-ideality of the reaction mixture, the kinetics were expressed in terms of activities. Additional experiments, based on a D-optimum design of experiments, were performed to obtain more precise parameter estimates as required for final model discrimination. The kinetic model with the surface reaction of adsorbed methanol with ethyl acetate from the bulk as the rate-determining step according to an Eley–Rideal mechanism was found to best describe the observed kinetics. The corresponding rate equation agrees with a reaction mechanism in which physically adsorbed methanol reacts with protonated ethyl acetate. [Copyright &y& Elsevier]

In WWTP models, the accurate assessment of solids inventory in bioreactors equipped with solid-liquid separators, mostly described using one-dimensional (1-D) secondary settling tank (SST) models, is the most fundamental requirement of any calibration procedure. Scientific knowledge on characterising particulate organics in wastewater and on bacteria growth is well-established, whereas 1-D SST models and their impact on biomass concentration predictions are still poorly understood. A rigorous assessment of two 1-DSST models is thus presented: one based on hyperbolic (the widely used Takács-model) and one based on parabolic (the more recently presented Plósz-model) partial differential equations. The former model, using numerical approximation to yield realistic behaviour, is currently the most widely used by wastewater treatment process modellers. The latter is a convection-dispersion model that is solved in a numerically sound way. First, the explicit dispersion in the convection-dispersion model and the numerical dispersion for both SST models are calculated. Second, simulation results of effluent suspended solids concentration (XTSS,Eff), sludge recirculation stream (XTSS,RAS) and sludge blanket height (SBH) are used to demonstrate the distinct behaviour of the models. A thorough scenario analysis is carried out using SST feed flow rate, solids concentration, and overflow rate as degrees of freedom, spanning a broad loading spectrum. A comparison between the measurements and the simulation results demonstrates a considerably improved 1-D model realism using the convection-dispersion model in terms of SBH, XTSS,RAS and XTSS,Eff. Third, to assess the propagation of uncertainty derived from settler model structure to the biokinetic model, the impact of the SST model as sub-model in a plant-wide model on the general model performance is evaluated. A long-term simulation of a bulking event is conducted that spans temperature evolution throughout a summer/winter sequence. The model prediction in terms of nitrogen removal, solids inventory in the bioreactors and solids retention time as a function of the solids settling behaviour is investigated. It is found that the settler behaviour, simulated by the hyperbolic model, can introduce significant errors into the approximation of the solids retention time and thus solids inventory of the system. We demonstrate that these impacts can potentially cause deterioration of the predictive power of the biokinetic model, evidenced by an evaluation of the system's nitrogen removal efficiency. The convection-dispersion model exhibits superior behaviour, and the use of this type of model thus is highly recommended, especially bearing in mind future challenges, e.g., the explicit representation of uncertainty in WWTP models. [ABSTRACT FROM AUTHOR]

Currently, no mechanistic model is available in wastewater industry that can accurately describe the batch settling behaviour of activated sludge. Such a model, which is based on the fundamental mass and force balances for water and solids, is extended and applied in this work and excellently describes batch settling experiments for sludges originating from two different wastewater treatment plants. The mechanistic model contains a Kynch batch density function (hindered settling) and an effective solids stress function (compression). Initial settling velocities were obtained from detailed spatio-temporal dynamic solids concentration profiles measured with the aid of a radiotracer [De Clercq, J., Jacobs, J., Kinnear, D.J., Nopens, I., Dierckx, R.A., Defrancq, J., Vanrolleghem, P.A., 2005. Detailed spatio-temporal solids concentration profiling during batch settling of activated sludge using a radiotracer. Water Res. 39(10), 2125–2135]. Moreover, inverse modelling calculations were performed using the same data set. Both calculations showed that (1) the power function of Cole gave acceptable results and (2) a single effective solids stress function could be found when a time-dependent compression solids concentration was considered. This compression solids concentration is found just below the sludge blanket and is readily calculated from the solids concentration profiles. Given these time-evolutions, the effective solids stress values exhibit a uniform logarithmic relationship with the difference between the solids concentration and the compression solids concentration. The descriptive power of the model indicates a good potential for wider applicability of the model. [Copyright &y& Elsevier]

Abstract: In building and tuning good settling models for secondary clarifiers of wastewater treatment plants, there is a need for measured continuous solids concentration profiles during batch settling. Conventional measuring techniques have difficulties in recording this kind of data, either because they are invasive, or because of the low solids concentration and/or solids density of activated sludge. This paper investigates a novel non-invasive measurement technique borrowed from nuclear medicine, using a solids radiotracer and gamma cameras, to obtain solids concentration profiles during the batch settling of activated sludge, in a pilot-scale column with a height of 1m. The technique does not disturb the settling process, does not alter the settling characteristics, gives profiles every minute and every few millimeters, and is capable of measuring in a range of 0–25g/l with high accuracy. Dynamic solids concentration profile measurements were performed for sludges of different wastewater treatment plants, and at different initial concentrations. The results show a quantitative representation of the settling process, and reveal hindered and compression settling. [Copyright &y& Elsevier]

Size exclusion chromatography with total organic carbon detection (HPSEC-TOC) is a widely employed technique for characterizing aquatic natural organic matter (NOM) into high, medium, and low molecular weight fractions. This study validates the suitability of HPSEC-TOC for a simplified yet efficient routine analysis of freshwater and its application within drinking water treatment plants. The investigation highlights key procedural considerations for optimal results and shows the importance of sample preservation by refrigeration with a maximum storage duration of two weeks. Prior to analysis, the removal of inorganic carbon is essential, which is achieved without altering the NOM composition through sample acidification to pH 6 and subsequent N2-purging. The chromatographic separation employs a preparative TSK HW-50S column to achieve a limit of detection of 19.0 µgC dm−3 with an injection volume of 1350 mm−3. The method demonstrates linearity up to 10,000 µgC dm−3. Precision, trueness and recovery assessments are conducted using certified reference materials, model compounds, and real water samples. The relative measurement uncertainty in routine analysis ranges from 3.22% to 5.17%, while the measurement uncertainty on the bias is 8.73%. Overall, the HPSEC-TOC represents a reliable tool for NOM fractions analysis in both treated and untreated ground and surface water. [ABSTRACT FROM AUTHOR]

• Aminated silica catalysts deactivate due to water as solvent in the aldol reaction. • Water-stable PEG containing polymer resins have been functionalized with diamines. • The amine-PEG catalysts show a high activity for the aqueous aldol reaction. • In continuous-flow, the amine-PEG catalyst is stable for at least 8 h on-stream. Amine functionalized silicas have frequently been investigated as potential aldol reaction catalysts. However, active site leaching due to hydrolysis cannot be avoided, limiting the long-term stability of these catalysts in aqueous aldol reactions. Therefore, novel catalysts based on an organic resin have been developed starting from a suspension polymerized poly(ethylene glycol) methacrylate (PEGMA) hydrogel with poly(ethylene glycol) dimethacrylate (PEGDMA) as cross-linker. Amine functionalization was performed by chlorination of the terminal hydroxyl groups in the resulting PEGMA resin and subsequent nucleophilic substitution with an amine precursor, i.e. , ethylenediamine (EDA), N,N′-dimethylethylenediamine (DED), or methylamine (MA). The successful synthesis of the catalysts was confirmed by 13C NMR, FT-IR, and elemental CHN analysis. Performance evaluation in a batch reactor for the aqueous aldol reaction of acetone with 4-nitrobenzaldehyde resulted in a turnover frequency (TOF) of the PEGMA-EDA catalyst amounting to 6.3 ± 0.4 · 10−4 s−1, which is of the same order of magnitude as that of the corresponding state-of-the-art amine functionalized silica evaluated using hexane as solvent. The PEGMA-DED catalyst exhibited a somewhat lower TOF of 3.1 ± 0.2 · 10−4 s−1, while the PEGMA-MA catalyst did not exhibit any turnover, indicating that the secondary amine in the backbone of the active site in the PEGMA-EDA catalyst is inactive. Continuous-flow evaluation of the PEGMA-EDA catalyst in a packed-bed reactor indicated that, as opposed to a primary amine functionalized silica catalyst, a stable catalytic activity as a function of time on stream could be achieved for at least 8 h and, hence, that no deactivation has occurred in this timeframe. [ABSTRACT FROM AUTHOR]

Mesoporous MIL-101(Cr) is used as host for a ship-in-a-bottle type adsorbent for selective U(VI) recovery from aqueous environments. The acid-resistant cage-type MOF is built in-situ around N,N-Diisobutyl-2-(octylphenylphosphoryl)acetamide (CMPO), a sterically demanding ligand with high U(VI) affinity. This one-step procedure yields an adsorbent which is an ideal compromise between homogeneous and heterogeneous systems, where the ligand can act freely within the pores of MIL-101, without leaching, while the adsorbent is easy separable and reusable. The adsorbent was characterized by XRD, FTIR spectroscopy, nitrogen adsorption, XRF, ADF-STEM and EDX, to confirm and quantify the successful encapsulation of the CMPO in MIL-101, and the preservation of the host. Adsorption experiments with a central focus on U(VI) recovery were performed. Very high selectivity for U(VI) was observed, while competitive metal adsorption (rare earths, transition metals...) was almost negligible. The adsorption capacity was calculated at 5.32 mg U/g (pH 3) and 27.99 mg U/g (pH 4), by fitting equilibrium data to the Langmuir model. Adsorption kinetics correlated to the pseudo-second-order model, where more than 95% of maximum uptake is achieved within 375 min. The adsorbed U(VI) is easily recovered by desorption in 0.1 M HNO 3 . Three adsorption/desorption cycles were performed. [ABSTRACT FROM AUTHOR]

The carbamoylmethylphosphine oxide (CMPO) functionalized MIL-101(Cr) was investigated as a potential uranium scavenger. This metal--organic framework-based adsorbent shows very high selectivity toward uranium, as well as thorium, in competition with various rare earth metals. Furthermore, it showed rapid adsorption kinetics, in both batch conditions and a dynamic (column) setup. The adsorbent is fully regenerable, using oxalate solution. Fast elution kinetics in the column setup were observed during the regeneration. In addition, reusability studies were performed under dynamic conditions. Five consecutive adsorption/desorption cycles were carried out, showing a consistent 100% recovery, at pH 4, using 0.1 M oxalate solution as an effective stripping agent. Additionally, the successive use over various adsorption/desorption cycles with constant performance proves the high stability of this adsorbent in an acidic, aqueous environment. [ABSTRACT FROM AUTHOR]

A straightforward procedure to synthesize cysteine functionalized materials with tailored support properties has been developed. It allows tuning the hydrophobicity of the material via the incorporation of aliphatics, aromatics or silica in the framework structure. The aldol condensation of 4-nitrobenzaldehyde and acetone, as a probe reaction for the catalytic activity of the produced materials, exhibited a remarkable interplay between the reactant, solvent, traces of water and support hydrophobicity. A selective enrichment in the catalyst pores of specific bulk phase molecules is believed to be the key to achieve the targeted catalyst performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pd/AC has the highest depolymerization activity due to unique surface properties. • Adding Cu to a Pd/oxide support catalyst alters the catalyst's selectivity. • C=C bond hydrogenation of functional side chains leads to favorable monomer yields. • Parallel solvolytic and catalytic depolymerization due to size-exclusion phenomena. This study pioneers the exploration of the structure-performance relationship of 5 wt% Pd and PdCu catalysts on 3 supports (γ-Al 2 O 3 , SiO 2 , and activated carbon (AC)) in the mild reductive depolymerization (MRD) of Soda lignin. While all catalysts achieve similar final weight average molecular weight (Mw) reduction (≈ 85 %), Pd/AC and PdCu/AC show significant differentiation from solvolysis already after 2 h and 3 h, compared to 6 h and 20 h for Pd and PdCu on oxide supports. This study also highlights the importance of hydrogenation of C=C bonds in monomer side-chains for maximizing monomer yields. Particularly PdCu/SiO 2 is characterized by the lowest monomer yields (7 wt%) due to its low hydrogenation activity, while catalysts like Pd(Cu)/Al 2 O 3 , Pd/SiO 2 , and Pd/AC, with more expressed hydrogenation, achieve a total monomer yield of up to 14 wt%. Additional findings confirm that on γ-Al 2 O 3 , the co-impregnation of Cu and Pd leads to the formation of a chemical bond between Pd2+ and Cu1+, resulting in a new mixed metal oxide Pd-Cu–O phase. On SiO 2 , Pd2+ and Cu1+ do not form a chemical bond, however, the presence of Cu1+ in close proximity to Pd2+ significantly alters the selectivity of the PdCu/SiO 2 catalyst due to synergetic effects. PdCu/AC maintains similar selectivity to Pd/AC, except for reduced hydrogenation over time, due to the lack of interaction between Pd and Cu on the AC surface. This research also delves into the MRD mechanism of Soda lignin over Pd and PdCu catalysts, focusing on the β-O-4 linkage cleavage and the subtle differences in reaction pathways depending on the catalyst. These findings bridge gaps in understanding the MRD of actual lignin feedstocks, offering valuable insights for catalyst development and process optimization. [ABSTRACT FROM AUTHOR]

Lignin valorization and particularly its depolymerization into bio‐aromatics, has emerged as an important research topic within green chemistry. However, screening of catalysts and reaction conditions within this field is strongly constrained by the lack of analytical techniques that allow for fast and detailed mapping of the product pools. This analytical gap results from the inherent product pool complexity and the focus of the state‐of‐the‐art on monomers and dimers, overlooking the larger oligomers. In this work, this gap is bridged through the development of a quasi‐orthogonal GPC‐HPLC‐UV/VIS method that is able to separate the bio‐aromatics according to molecular weight (hydrodynamic volume) and polarity. The method is evaluated using model compounds and real lignin depolymerization samples. The resulting color plots provide a powerful graphical tool to rapidly assess differences in reaction selectivity towards monomers and dimers as well as to identify differences in the oligomers. [ABSTRACT FROM AUTHOR]

• First process simulation of a three step squalene recovery process • Comparison between olive, sunflower and soybean ODD for squalene recovery • Same process configuration for different feedstocks, ensuring flexibility The potential of squalene recovery from oil deodorizer distillates (ODD) via a combination of supercritical ethanol esterification, supercritical CO 2 -extraction and additional purification was assessed via detailed process simulations. The squalene yields and purity from olive, sunflower and soybean ODD were determined. The highest squalene yield and purity could be achieved starting from olive ODD (95 g squalene kg−1 ODD , 99 wt% pure), followed by soybean ODD (31 g squalene kg−1 ODD , 98 wt% pure) and sunflower ODD (24 g squalene kg−1 ODD , 98 wt% pure). Apart from squalene, two more value-added products can be produced, i.e., high purity ethyl esters (>88 wt%) and a mixture of tocopherols and sterols. On a scale of 1 kTonne ODD per year, all feedstocks demonstrate economical potential in Europe. Even more, a flexible process configuration could be designed which is suitable for the treatment of the different feedstocks. [ABSTRACT FROM AUTHOR]

• The leaching behaviour and mechanisms are elucidated via combined data analysis. • A homogeneous-heterogeneous catalytic system prevails for both NP catalysts. • The leaching pathway critically depends on the resin functionality. • Phenylpalladium(II)hydroxide complexes are proposed as the leached Pd2+ species. The Pd leaching behaviour of a strongly acid (Lewatit K2629) versus strongly basic (Lewatit MP500 OH) ion exchange resin supported Pd nanoparticle (Pd-NP) catalyst is elucidated in the Suzuki reaction between iodobenzene and phenylboronic acid with K 2 CO 3 as base in 1:1 (v/v) DMF/H 2 O at 40 °C. Reaction and leaching kinetic analyses combined with hot filtration tests indicated heterogeneous-homogeneous catalysis for both Pd-NP catalysts. More particularly, leaching experiments showed that for Pd-NP Lewatit K2629, Pd-NP as well as molecular Pd2+ leaching (as phenylpalladium(II)hydroxide complexes) occurred due to, respectively, the disturbance of the electrostatic NP stabilization by dissociated K 2 CO 3 and reaction with iodobenzene and hydroxide. For Pd-NP Lewatit MP500 OH, however, molecular Pd2+ leaching induced by iodobenzene, dominates. Hence, the resin functionality determines the contribution of each leaching pathway. Furthermore, at high conversions, Pd re-deposition occurred due to the decreased amount of leaching inducing reagents causing enlarged NPs in the resin which leached less in subsequent runs. [ABSTRACT FROM AUTHOR]

• Computational nucleophilicity probing of amines for the aldol reaction. • Trimethylborane (TMB) probes steric and electronic substituent effects on amines. • The experimental activity of hindered amines in the aldol reaction can be described. • New amine sites with an optimized TMB basicity are designed for the aldol reaction. Accessibility of the nucleophilic site in organocatalysts is essential to ensure adequate catalytic activity. Gas-phase trimethylborane (TMB) Lewis basicity and Brønsted proton basicity of several amine based organocatalysts have been calculated using the CBS-QB3 model chemistry. This TMB basicity scale can, as opposed to the proton basicity scale, account for steric effects encountered in the initial nucleophilic attack of the nitrogen free electron pair on a substrate. Since such a step is the first one in several amine catalyzed reactions, severe steric hindrance of the nucleophilic center would render the catalyst ineffective. Comparing the TMB basicity and proton basicity with the experimentally observed catalytic activity of both homogeneous and heterogeneously supported amine sites found in literature for the aldol reaction of acetone with 4-nitrobenzaldehyde showed that, due to the inclusion of these steric effects, the TMB basicity scale is a much better predictor of catalytic activity than the proton basicity. According to this computational Lewis basicity scale, potential steric hindrance in alternative nitrogen containing active sites was probed. This resulted in 3-propylpyrrolidine being proposed among the most promising monofunctional amine groups and 1-(methylamino)propan-2-ol among the most promising bifunctional amine-hydroxyl groups for heterogeneous aldol reaction catalysts. [ABSTRACT FROM AUTHOR]

Growing research on lignin depolymerization to functionalized bio-aromatics has necessitated dedicated analysis techniques. However, immense variability in molecular weight and functional groups of the depolymerization products impedes fast analysis of a large number of samples while remaining in-depth enough for catalyst screening or reaction condition optimization. While GPC-HPLC-UV/VIS has been a promising technique, up until now, the information it provides is largely qualitative. By enabling quantification of key monomeric products and through further reduction of overall analysis time, this study aims to increase the potential of GPC-HPLC-UV/VIS for fast and in-depth characterization of lignin depolymerization product pools. Analysis of selected samples, isolated from GPC-HPLC-UV/VIS analyses of lignin depolymerization product pools, with gas chromatography (GC) equipped with an Orbitrap high-resolution accurate mass spectrometer (Orbitrap-HR/AM-MS) is successful in identifying the main low monomeric products. Moreover, these identifications are further substantiated through GPC-HPLC-UV/VIS analysis of standards. Furthermore, straight forward quantification of these products directly within GPC-HPLC-UV/VIS is successfully developed with limits of detection ≤0.05 mmol/L, which is at least on par with more complex analysis techniques. Additionally, several different reversed phase columns are assessed to reduce 2nd dimension (2D) time and, hence, overall analysis time while maintaining the possibility for quantification. A reduction in overall analysis time of about 30% as compared to the state-of-the-art is achieved by using a YMC Triart BIO C4 column as 2D. Through the enhancements introduced in this study, GPC-HPLC-UV/VIS emerges as a unique technique for the analysis of lignin depolymerization product pools, which is capable of fast yet sufficiently in-depth analysis of a large volume of samples. This capability is indispensable for catalyst screening and fine-tuning reaction conditions. [Display omitted] • Analysis potential and speed of in-house GPC-HPLC-UV/VIS method improved. • Main lignin derived monomers identified via GC-Orbitrap-HR/AM-MS analysis. • Reduction in overall analysis time of 30% with alternative 2D column. • Quantification of monomers (LOD ≤0.05 mol L−1) with GPC-HPLC-UV/VIS developed. • Adaptability of GPC-HPLC-UV/VIS to intended purpose substantiated. [ABSTRACT FROM AUTHOR]

The reusability of methylaminopropyl active sites grafted on mesoporous amorphous silica, either with cooperative silanol groups or trimethylsilated, was assessed in the aldol reaction of acetone with 4-nitrobenzaldehyde. Raman, 13 C NMR, and UV–Vis spectroscopy demonstrated the presence of stable enamines on the spent catalysts. These enamines are produced as a side product from iminium intermediates in the catalytic cycle. Water co-feeding enhances the desorption of the iminium intermediates and, hence, suppresses the formation of these stable enamine species. The reusability of the cooperative catalyst increased to 70% with co-feeding 0.69 wt% water, while an almost complete reusability was achieved for the trimethylsilated catalyst. Continuous-flow experimentation showed that the cooperative effect of the silanol groups was lost during the first 7 h on-stream, yet activity losses continued, most likely due to silica hydrolysis. Activity losses persisted on the more hydrophobic trimethylsilated catalyst, but were significantly less pronounced. [ABSTRACT FROM AUTHOR]

An uncalcined HT supported Pd-NP catalyst was synthesized via co-precipitation, i.e., PdHT_100RED_20, and benchmarked against a Pd impregnated HT catalyst, i.e., Pd@HT_500RED_20. TEM analysis pointed out that the largest NPs (6.5 nm) were found in the co-precipitated catalyst because of its weaker steric NP confinement, compared to the benchmark catalyst (3.2 nm). The PdHT_100RED_20 had a significantly higher catalytic performance (60% conversion, 1.85% leaching) than Pd@HT_500RED_20 (19%, 0.98%) due to lack of calcination resulting in an ordered, and thus, more accessible HT structure in combination with its high support basicity. Both catalysts showed low Pd leaching confirming the suitability of HTs as NP support. Focusing on PdHT_100, the effect of the reduction temperature on the NP size and catalytic performance was investigated. NP size distribution analysis showed that the smallest NPs were found in PdHT_100RED_0 (5.3 nm), resulting in a higher catalytic performance (67%, 2.28%) when compared to PdHT_100RED_20 (6.5 nm). Performing the reduction at higher temperatures, i.e., at 60 °C (5.7 nm), caused an extremely low catalytic performance (13%, 0.20%) due to the less efficient reduction reaction with NaBH 4 at higher reduction temperatures. Reusing PdHT_100RED_20, a decrease in catalytic performance (45%) was observed. However, this decrease was less pronounced (50%) when a re-activation of the catalyst with Na 2 CO 3 between consecutive runs was performed. Moreover, it was shown that the leached Pd species were able to re-deposit onto the support if high conversions were obtained, and thus, an almost quantitatively recovery from the reaction mixture can be achieved with retention of its catalytic activity (>99%). [ABSTRACT FROM AUTHOR]

Tunable large pore soft templated mesoporous carbons (SMC) were obtained via the organic self-assembly of resorcinol/formaldehyde with the triblock copolymer F127 and by investigating the effect of carbon precursor to surfactant (p/s) ratio and carbonization temperature on the material characteristics. The p/s ratio and carbonization temperature were varied respectively from 0.83 to 0.25 and from 400 to 1200 °C. The resulting SMCs had various average pore sizes, tunable from 7 up to 50 nm. At lower p/s ratios, the pore size increased, pore size distributions broadened, and pore volumes increased. An increase of hydrophobicity was observed at elevated carbonization temperatures. A 2D hexagonal ordered SMC with a narrow pore size distribution was obtained at a ratio of 0.83. Lower ratios (0.5 and 0.25) transformed into disordered porous carbons containing micropores, mesopores, and even macropores. The SMCs were tested for adsorption of a large organic molecule, humic acid (HA), from water. The material characteristics that significantly affected HA adsorption capacity were pore size and mass % (wt %) carbon. The novel SMCs showed an unprecedented high adsorption of HA in the entire molecular weight distribution range. SMCs with large mesopores resulted in higher maximum adsorption capacities and improved HA adsorption kinetics compared to activated carbon. [ABSTRACT FROM AUTHOR]

Mesoporous carbons have been the subject of various studies, both fundamental and applied. Fundamental studies revealed numerous synthesis routes which can adjust material characteristics as specific surface area, pore volume, pore size or morphology and elemental composition. The indirect synthesis or hard template method was developed first. An extensive collection of template materials exist, which can be impregnated with carbon precursors to provide various hard templated mesoporous carbons with a precise control of mesoporosity and pore geometry. However, the more recent direct method or soft template method offers some specific advantages. By using the organic-organic self-assembly between polymerizable precursors and block copolymer surfactants as structure directing agents it is possible to obtain tunable morphology and surface properties, mechanical stability and reduce the number of synthesis steps, thereby decreasing synthesis cost and complexity. Applied studies valorize this wide variety of mesoporous carbons. Fine-tuning material characteristics as surface area, pore volume, pore size, morphology, chemical composition or possible post-modification or nanoparticle doping give rise to applications in catalysis, electrochemistry, energy storage, separation or adsorption. In adsorption, mesoporous carbons are considered as a new family of adsorbents challenging the well-known activated carbon by introducing the advantage of increasing pore size. This allows mesoporous carbons to adsorb larger molecules and enhance the adsorption kinetics. In this review we present the most recent achievements and advances in the synthesis of soft templated mesoporous carbons, with focus on pore size control, and their potential as a new family of carbon adsorbents. [ABSTRACT FROM AUTHOR]

Macroporous ion exchange resin supported palladium nanoparticle (Pd-NP) catalysts are prepared by an intermatrix synthesis. For the first time, the effect of resin functionality (weak acid, strong acid, strong base) on the NP size, their catalytic activity, and leaching is investigated in the Suzuki cross-coupling of iodobenzene and phenylboronic acid. Whereas the smallest NPs (1.34 nm) are found in the thiol Ambersep GT74 resin, the sulfonic acid Lewatit K2629 and quaternary amine Lewatit MP500 OH resins resulted in NPs of a similar size (2.42 and 2.59 nm, respectively). Despite their smaller size, the NPs on Ambersep GT74 exhibited the lowest conversion (21.6 %), which is attributed to a too strong coordination of the NPs by the thiol groups. The conversions obtained by using Lewatit K2629 (76.8 %) and Lewatit MP500 OH (94.2 %) were considerably higher, the excellent performance of the latter catalyst being ascribed to the promoting effect of the hydroxyl groups on the transmetallation and reductive elimination steps in Suzuki cross-coupling. No Pd leaching was observed when using Ambersep GT74 as the support, compared with Pd leaching amounting to 1.1 % and 4.8 % when using Lewatit MP500 OH and Lewatit K2629, respectively. Such low values indicate that ion exchange resins are ideal supports to stabilize the NPs. Particularly, the combination of high conversion and limited leaching on Lewatit MP500 OH opens up new perspectives for catalyzing Suzuki cross-coupling with a heterogeneous catalyst. [ABSTRACT FROM AUTHOR]

Mesoporous carbons were synthesized via both soft and hard template methods and compared to a commercial powder activated carbon (PAC) for the adsorption ability of bisphenol-A (BPA) from an aqueous solution. The commercial PAC had a BET-surface of 1027 m2/g with fine pores of 3 nm and less. The hard templated carbon (CMK-3) material had an even higher BET-surface of 1420 m2/g with an average pore size of 4 nm. The soft templated carbon (SMC) reached a BET-surface of 476 m2/g and a pore size of 7 nm. The maximum observed adsorption capacity (qmax) of CMK-3 was the highest with 474 mg/g, compared to 290 mg/g for PAC and 154 mg/g for SMC. The difference in adsorption capacities was attributed to the specific surface area and hydrophobicity of the adsorbent. The microporous PAC showed the slowest adsorption, while the ordered mesopores of SMC and CMK-3 enhanced the BPA diffusion into the adsorbent. This difference in adsorption kinetics is caused by the increase in pore diameter. However, CMK-3 with an open geometry consisting of interlinked nanorods allows for even faster intraparticle diffusion. [ABSTRACT FROM AUTHOR]

The synthesis of soft template mesoporous carbons was optimized with a Definitive Screening Design (DSD), a recently developed design of experiments (DOE) method. Such a design enables to investigate the effect of synthesis parameters including their interactions or quadratic effects, on the material properties. The mesopore formation was influenced mostly by the ratio precursor/surfactant, other significant effects were curing time and carbonization temperature. The micropore formation was significantly influenced by the curing time and the carbonization temperature. The DSD was used to optimize the mesoporous surface area which could improve its potential as adsorbent. Via a validation experiment, a material with optimal mesoporous surface area (393 m 2 /g) was synthesized, showing a total surface area of 712 m 2 /g and a large pore volume of 0.78 cm 3 /g. The different mesoporous carbons, synthesized according to the DSD, were tested for the adsorption of bisphenol A (BPA). This allowed to investigate the effect of material properties on the adsorption capacity, which varied between 12 and 163 mg/g. Via regression analysis, the mesoporous surface area and the carbon content of the mesoporous carbons were identified as the main factors influencing the adsorption of BPA. [ABSTRACT FROM AUTHOR]

[Display omitted] • n -Alkane hydrocracking is more negatively impacted with admixture of heavier cycloalkanes. • Cycloalkane adsorbs on metal sites more favorably than n -alkane with higher carbon number. • Larger alkanes impact cycloalkanes conversion only by preferred physisorption. Cycloalkanes are known to impact the metal–acid balance of the hydrocracking of n -alkanes with similar carbon number, however, how this impact varies with the carbon number of the components involved is still to be understood in more detail. For this purpose, the hydroconversion of n -octane and tert -butylcyclohexane, and n -decane and methylcyclohexane mixtures was investigated in this work over Pt/HUSY catalyst in both the ideal and the nonideal hydrocracking regime. Irrespective of the hydrocracking regime for pure n -octane, its conversion and isomer yields were significantly lowered upon admixture of tert -butylcyclohexane. On the other hand, n -octane admixture did not impact the tert -butylcyclohexane conversion nor its cyclic isomer yields. Upon methylcyclohexane admixture with n -decane, no impact was observed over the catalyst ensuring ideal hydrocracking of pure n -decane. Over the catalyst with significantly lower Pt loading, which does not ensure ideal hydrocracking of n -decane, methylcyclohexane lowered the n- decane conversion. A slightly negative impact of n -decane admixture on methylcyclohexane conversion was also observed. The observed effects are mainly attributed to the differences in adsorption strengths within the zeolite pores on top of differences in alkane and cycloalkane adsorption on the metal sites. [ABSTRACT FROM AUTHOR]

• Water and silanol effects on amine catalyzed aldol reactions are elucidated. • 2 water molecules are optimal for reactions involving a proton transfer. • 1 water molecule is sufficient to prevent site-blocking enamine species. • Silanols assist the amine in a similar but slightly more pronounced manner. • The effect of water is more pronounced in hexane as compared to DMSO. The experimentally observed effects of water, and the effects of silanol groups, on the liquid-phase amine-catalyzed aldol reaction of acetone with 4-nitrobenzaldehyde have been elucidated with a comprehensive theoretical model describing the reaction kinetics. The CBS-QB3 model chemistry is used, with bulk solvent effects accounted for according to COSMO-RS theory, and water molecules explicitly considered. Two promoting water molecules were found to be optimal in reducing the Gibbs free energy barriers for reactions involving a proton transfer, i.e., the carbinolamine and enamine formation steps, and the aldol product liberation step. The presence of one water molecule in the carbon-carbon coupling step was already sufficient to prevent the formation of a site-blocking enamine species, which would otherwise lead to deactivation of the amine. Compared to a single water molecule, isolated silanol groups were found to assist the amine in a similar and slightly more pronounced manner, resulting in overall lower barriers for all transition states. Promotion by two vicinal silanols resulted in even lower barriers. The effect of water was found to be more pronounced in apolar hexane as compared to DMSO, i.e., resulting in a less pronounced deactivation of the amine, and lower barriers for reactions where water is assisting in the transition state. [ABSTRACT FROM AUTHOR]

The effect of Ba, Ce, Cs and La as co-metals in Cu/γ-Al 2 O 3 catalysts for the hydrogenolysis of glycerol into 1,2-propanediol was investigated at industrially relevant reaction conditions over time. The addition of Ba or Ce increased the initial activity per Cu0 accessible site. Apart from Cs, the co-metals increased the selectivity towards 1,2-propanediol, up to 96% (Ba). The co-metals inhibited sintering and stabilized the Cu particle size during reaction, by decreasing the particle growth by a factor of 10. Overall, co-metals mainly influenced the selectivity and stabilized the Cu particle. Unlabelled Image • Ba-, Ce-, Cs- and La-doping stabilized the Cu0 particle size during the reaction. • Doping with Ba, Ce or Cs preserved the initial glycerol conversion. • Comparable 1,2-propanediol productivities to commercial catalyst wwas achieved under continuous liquid flow operation. • A selectivity of 96% for 1,2-propanediol was achieved with the Ba-doped catalyst. [ABSTRACT FROM AUTHOR]

A packed-bed plug-flow reactor, denoted as the lab-scale liquid-solid (LS)² reactor, has been developed for the assessment of heterogeneous catalyst deactivation in liquid-phase reactions. The possibility to measure intrinsic kinetics was first verified with the model transesterification of ethyl acetate with methanol, catalyzed by the stable commercial resin Lewatit K2629, for which a turnover frequency (TOF) of 6.2 ± 0.4 × 10−3 s−1 was obtained. The absence of temperature and concentration gradients was verified with correlations and experimental tests. The potential for assessing the deactivation of a catalyst was demonstrated by a second intrinsic kinetics evaluation where a methylaminopropyl (MAP)-functionalized mesoporous silica catalyst was used for the aldol reaction of acetone with 4-nitrobenzaldehyde in different solvents. The cooperative MAP catalyst deactivated as a function of time on stream when using hexane as solvent. Yet, the monofunctional MAP catalyst exhibited stable activity for at least 4 h on stream, which resulted in a TOF of 1.2 ± 0.1 × 10−3 s−1. It did, however, deactivate with dry acetone or DMSO as solvent due to the formation of site-blocking species. This deactivation was mitigated by co-feeding 2 wt % of water to DMSO, resulting in stable catalyst activity. [ABSTRACT FROM AUTHOR]