Bifunctional Au-Sn-SiO2 catalysts promote the direct upgrading of glycerol to methyl lactate.

Valuable alkyl lactates can be obtained from (waste) glycerol, through a two-step process that entails (i) the oxidation of glycerol to dihydroxyacetone (DHA) catalyzed by support Au nanoparticles and (ii) a rearrangement of DHA with an alcohol effectively catalyzed by Sn-based heterogeneous catalysts. To solve selectivity and processing issues we propose to run the process as a cascade reaction, in one step, and with a single bifunctional catalyst. Tackling the challenge associated with the preparation of such bifunctional catalysts, here, an aerosol-assisted sol-gel route is exploited. The catalysts feature small Au nanoparticles (3-4 nm) embedded at the surface of mesoporous Sn-doped silica microspheres. The preparation successfully leads to insert both active sites in their most active forms, and in close proximity. With the bifunctional catalysts, the yield for the final product of the cascade reaction (methyl lactate) is higher than the DHA yield when only the first reaction is carried out. This highlights a beneficial substrate channeling effect which alleviates side reactions. Interestingly, the bifunctional catalysts also markedly outcompeted mechanical mixtures of the corresponding monofunctional Au- and Sn-based catalysts. Thus, the spatial proximity between the two active sites in bifunctional catalysts is identified as a key to stir the cascade reaction towards high lactate yield.

Propylene Metathesis over Molybdenum Silicate Microspheres with Dispersed Active Sites.

In this work, we demonstrate that amorphous and porous molybdenum silicate microspheres are highly active catalysts for heterogeneous propylene metathesis. Homogeneous molybdenum silicate microspheres and aluminum-doped molybdenum silicate microspheres were synthesized via a nonaqueous condensation of a hybrid molybdenum biphenyldicarboxylate-based precursor solution with (3-aminopropyl)triethoxysilane. The as-prepared hybrid metallosilicate products were calcined at 500 °C to obtain amorphous and porous molybdenum silicate and aluminum-doped molybdenum silicate microspheres with highly dispersed molybdate species inserted into the silicate matrix. These catalysts contain mainly highly dispersed MoOx species, which possess high catalytic activity in heterogeneous propylene metathesis to ethylene and butene. Compared to conventional silica-supported MoOx catalysts prepared via incipient wetness impregnation (MoIWI), the microspheres with low Mo content (1.5-3.6 wt %) exhibited nearly 2 orders of magnitude higher steady-state propylene metathesis rates at 200 °C, approaching site time yields of 0.11 s-1.

Multifunctional, Hybrid Materials Design via Spray-Drying: Much more than Just Drying.

Spray-drying is a popular and well-known "drying tool" for engineers. This perspective highlights that, beyond this application, spray-drying is a very interesting and powerful tool for materials chemists to enable the design of multifunctional and hybrid materials. Upon spray-drying, the confined space of a liquid droplet is narrowed down, and its ingredients are forced together upon "falling dry." As  detailed in this article, this enables the following material formation strategies either individually or even in combination: nanoparticles and/or molecules can be assembled; precipitation reactions as well as chemical syntheses can be performed; and templated materials can be designed. Beyond this, fragile moieties can be processed, or "precursor materials" be prepared. Post-treatment of spray-dried objects eventually enables the next level in the design of complex materials. Using spray-drying to design (particulate) materials comes with many advantages-but also with many challenges-all of which are outlined here. It is believed that multifunctional, hybrid materials, made via spray-drying, enable very unique property combinations that are particularly highly promising in myriad applications-of which catalysis, diagnostics, purification, storage, and information are highlighted.

Leveraging Metal Nodes in Metal-Organic Frameworks for Advanced Anodic Hydrazine Oxidation Assisted Seawater Splitting.

Metal-organic frameworks (MOFs) show great promise for electrocatalysis owing to their tunable ligand structures. However, the poor stability of MOFs impedes their practical applications. Unlike the general pathway for engineering ligands, we report herein an innovative strategy for leveraging metal nodes to improve both the catalytic activity and the stability. Our electrolysis cell with a NiRh-MOF||NiRh-MOF configuration exhibited 10 mA cm-2 at an ultralow cell voltage of 0.06 V in alkaline seawater (with 0.3 M N2H4), outperforming its counterpart benchmark Pt/C||Pt/C cell (0.12 V). Impressively, the incorporation of Rh into a MOF secured a robust stability of over 60 h even when working in the seawater electrolyte. Experimental results and theoretical calculations revealed that Rh atoms serve as the active sites for hydrogen evolution while Ni nodes are responsible for the hydrazine oxidation during the hydrazine oxidation assisted seawater splitting. This work provides a paradigm for green hydrogen generation from seawater.

Engineering Amorphous/Crystalline Ru(OH)3/CoFe-Layered Double Hydroxide for Hydrogen Evolution at 1000 mA cm-2.

For large-scale industrial applications, it is highly desirable to create effective, economical electrocatalysts with long-term stability for the hydrogen evolution reaction (HER) at a large current density. Herein, we report a unique motif with crystalline CoFe-layered hydroxide (CoFe-LDH) nanosheets enclosed by amorphous ruthenium hydroxide (a-Ru(OH)3/CoFe-LDH) to realize the efficient hydrogen production at 1000 mA cm-2, with a low overpotential of 178 mV in alkaline media. During the continuous HER process for 40 h at such a large current density, the potential remains almost constant with only slight fluctuations, indicating good long-term stability. The remarkable HER performance can be attributed to the charge redistribution caused by abundant oxygen vacancies in a-Ru(OH)3/CoFe-LDH. The increased electron density of states lowers the charge-transfer resistance and promotes the formation and release of H2 molecules. The water-splitting electrolyzer with a-Ru(OH)3/CoFe-LDH as both an anode and a cathode in 1.0 M KOH demonstrates stable hydrogen production and a 100% faradic efficiency. The design strategy of interface engineering in this work will inspire the design of practical electrocatalysts for water splitting on an industrial scale.

Toward a Hydrogen-Free Reductive Catalytic Fractionation of Wheat Straw Biomass.

The reductive catalytic fractionation (RCF) of lignocellulosic biomass is an attractive method for the conversion of lignin toward valuable low-molecular weight aromatics. A limitation to the upscaling of such technology is represented by the use ofpressurized hydrogen gas. Here, the role of hydrogen gas within the RCF of wheat straw biomass is investigated. The use of H2 is shown to enhance lignin depolymerization, by virtue of an improved hydrogenolysis and hydrogenation of lignin fragments, with a yield of phenolic monomers that increased from ca. 12 wt % of acid-insoluble lignin in the initial biomass under inert atmosphere to up to ca. 25 wt % under H2 (in methanol, at 250 °C, with Ru/C). The adoption of methanol, ethanol or isopropanol as hydrogen-donor solvents was also investigated in the absence of H2 . Ethanol was found to give the highest yield of monophenolic compounds (up to ≈20 wt %) owing to a better balance between solvolysis, hydrogenolysis, and hydrogenation of lignin. Nevertheless, a substantial loss of the carbohydrate fraction was observed. The use of a lower temperature (200 °C) in combination with H3 PO4 resulted in an improved recovery of cellulose in the pulp and in the solubilization of hemicellulose and lignin, with the formation of monosaccharides (≈14 wt % of polysaccharides in the initial biomass) and phenolic monomers (up to 18 wt %, in the absence of H2 ). Overall, a tradeoff exists between the removal of H2 from the process and the production of low-molecular weight phenolics during RCF.

Key Parameters Impacting the Crystal Formation in Antisolvent Membrane-Assisted Crystallization.

Antisolvent crystallization is commonly used in the formation of heat-sensitive compounds as it is the case for most active pharmaceutical ingredients. Membranes have the ability to control the antisolvent mass transfer to the reaction medium, providing excellent mixing that inhibits the formation of local supersaturations responsible for the undesired properties of the resulting crystals. Still, optimization of the operating conditions is required. This work investigates the impact of solution velocity, the effect of antisolvent composition, the temperature and gravity, using glycine-water-ethanol as a model crystallization system, and polypropylene flat sheet membranes. Results proved that in any condition, membranes were consistent in providing a narrow crystal size distribution (CSD) with coefficient of variation (CV) in the range of 0.5-0.6 as opposed to 0.7 obtained by batch and drop-by-drop crystallization. The prism-like shape of glycine crystals was maintained as well, but slightly altered when operating at a temperature of 35 °C with the appearance of smoother crystal edges. Finally, the mean crystal size was within 23 to 40 µm and did not necessarily follow a clear correlation with the solution velocities or antisolvent composition, but increased with the application of higher temperature or gravity resistance. Besides, the monoclinic form of α-glycine was perfectly maintained in all conditions. The results at each condition correlated directly with the antisolvent transmembrane flux that ranged between 0.0002 and 0.001 kg/m2. s. In conclusion, membrane antisolvent crystallization is a robust solution offering consistent crystal properties under optimal operating conditions.

High-Entropy-Alloy Nanocrystal Based Macro- and Mesoporous Materials.

High-entropy-alloy (HEA) nanoparticles are attractive for several applications in catalysis and energy. Great efforts are currently devoted to establish composition-property relationships to improve catalytic activity or selectivity. Equally importantly, developing practical fabrication methods for shaping HEA-based materials into complex architectures is a key requirement for their utilization in catalysis. However, shaping nano-HEAs into hierarchical structures avoiding demixing or collapse remains a great challenge. Herein, we overcome this issue by introducing a simple soft-chemistry route to fabricate ordered macro- and mesoporous materials based on HEA nanoparticles, with high surface area, thermal stability, and catalytic activity toward CO oxidation. The process is based on spray-drying from an aqueous solution containing five different noble metal precursors and polymer latex beads. Upon annealing, the polymer plays a double role: templating and reducing agent enabling formation of HEA nanoparticle-based porous networks at only 350 °C. The formation mechanism and the stability of the macro- and mesoporous materials were investigated by a set of in situ characterization techniques; notably, in situ transmission electron microscopy unveiled that the porous structure is stable up to 800 °C. Importantly, this process is green, scalable, and versatile and could be potentially extended to other classes of HEA materials.

Hydrogen Borrowing: towards Aliphatic Tertiary Amines from Lignin Model Compounds Using a Supported Copper Catalyst.

Upcoming biorefineries, such as lignin-first provide renewable aromatics containing unique aliphatic alcohols. In this context, a Cu-ZrO2 catalyzed hydrogen borrowing approach was established to yield tertiary amine from the lignin model monomer 3-(3,4-dimethoxyphenyl)-1-propanol and the actual lignin-derived monomers, (3-(4-hydroxyphenyl)-1-propanol and dihydroconiferyl alcohol), with dimethylamine. Various industrial metal catalysts were evaluated, resulting in nearly quantitative mass balances for most catalysts. Identified intermediates, side and reaction products were placed into a corresponding reaction network, supported by kinetic evolution experiments. Cu-ZrO2 was selected as most suitable catalyst combining high alcohol conversion with respectable aliphatic tertiary amine selectivity. Low pressure H2 was key for high catalyst activity and tertiary amine selectivity, mainly by hindering undesired reactant dimethylamine disproportionation and alcohol amidation. Besides dimethylamine model, diverse secondary amine reactants were tested with moderate to high tertiary amine yields. As most active catalytic site, highly dispersed Cu species in strong contact with ZrO2 is suggested. ToF-SIMS, N2 O chemisorption, TGA and XPS of spent Cu-ZrO2 revealed that imperfect amine product desorption and declining surface Cu lowered the catalytic activity upon catalyst reuse, while thermal reduction readily restored the initial activity and selectivity demonstrating catalyst reuse.

Catalytic amination of lactic acid using Ru-zeolites.

In this work we investigate the synthesis of alanine from lactic acid, a biobased platform chemical, using ammonia as a nitrogen source and Ru/zeolite catalysts. We report a high alanine selectivity when using Ru/BEA of 80-93%. Reaction side products were identified as ethanol, propionic acid or propanamide and the reaction mechanism was investigated. We further optimised reaction conditions resulting in turn over numbers five times higher than previously reported and could reduce Ru leaching by 30-40%. However, leaching and catalyst stability remains a concern. Furthermore, we critically analyse the benefits of Ru/zeolites versus their stability under the basic, high temperature reaction conditions.

Hybrid chemoenzymatic heterogeneous catalyst prepared in one step from zeolite nanocrystals and enzyme-polyelectrolyte complexes.

The combination of inorganic heterogeneous catalysts and enzymes, in so-called hybrid chemoenzymatic heterogeneous catalysts (HCEHCs), is an attractive strategy to effectively run chemoenzymatic reactions. Yet, the preparation of such bifunctional materials remains challenging because both the inorganic and the biological moieties must be integrated in the same solid, while preserving their intrinsic activity. Combining an enzyme and a zeolite, for example, is complicated because the pores of the zeolite are too small to accommodate the enzyme and a covalent anchorage on the surface is often ineffective. Herein, we developed a new pathway to prepare a nanostructured hybrid catalyst built from glucose oxidase and TS-1 zeolite. Such hybrid material can catalyse the in situ biocatalytic formation of H2O2, which is subsequently used by the zeolite to trigger the epoxidation of allylic alcohol. Starting from an enzymatic solution and a suspension of zeolite nanocrystals, the hybrid catalyst is obtained in one step, using a continuous spray drying method. While enzymes are expectedly unable to resist the conditions used in spray drying (temperature, shear stress, etc.), we leverage on the preparation of "enzyme-polyelectrolyte complexes" (EPCs) to increase the enzyme stability. Interestingly, the use of EPCs also prevents enzyme leaching and appears to stabilize the enzyme against pH changes. We show that the one-pot preparation by spray drying gives access to hybrid chemoenzymatic heterogeneous catalysts with unprecedented performance in the targeted chemoenzymatic reaction. The bifunctional catalyst performs much better than the two catalysts operating as separate entities. We anticipate that this strategy could be used as an adaptable method to prepare other types of multifunctional materials starting from a library of functional nanobuilding blocks and biomolecules.

Correction: Hybrid chemoenzymatic heterogeneous catalyst prepared in one step from zeolite nanocrystals and enzyme-polyelectrolyte complexes.

[This corrects the article DOI: 10.1039/D0NA00834F.].

CO2 Hydrogenation to Methanol with Ga- and Zn-Doped Mesoporous Cu/SiO2 Catalysts Prepared by the Aerosol-Assisted Sol-Gel Process*.

The preparation of copper-based heterogeneous catalysts dedicated to the hydrogenation of CO2 to methanol typically relies on multi-step procedures carried out in batch. These steps are precisely tailored to introduce the active phase (Cu) and the promoters (e. g., zinc, gallium) onto a preformed support to maximize catalyst performance. However, each process step can be associated with the formation of waste and with the consumption of energy, thereby negatively impacting the environmental performance of the overall catalyst preparation procedure. Here, a direct and continuous production process is proposed for the synthesis of efficient catalysts for the CO2 -to-methanol reaction. Gallium- and zinc-promoted mesoporous Cu-SiO2 catalysts were prepared in one step by the aerosol-assisted sol-gel process. The catalysts consisted of spherical microparticles and featured high specific surface area and pore volume, with interconnected pores of about 6 nm. A strong promoting effect of Ga and Zn was highlighted, boosting the selectivity for methanol at the expense of CO. Upon calcination, it was shown that Cu species (initially trapped in the silica matrix) underwent a migration towards the catalyst surface and a progressive sintering. After optimization, the catalysts obtained via such direct, continuous, simple, and scalable route could compete with the best catalysts reported in the literature and obtained via multi-step approaches.

Continuous Flow Upgrading of Selected C2-C6 Platform Chemicals Derived from Biomass.

The ever increasing industrial production of commodity and specialty chemicals inexorably depletes the finite primary fossil resources available on Earth. The forecast of population growth over the next 3 decades is a very strong incentive for the identification of alternative primary resources other than petro-based ones. In contrast with fossil resources, renewable biomass is a virtually inexhaustible reservoir of chemical building blocks. Shifting the current industrial paradigm from almost exclusively petro-based resources to alternative bio-based raw materials requires more than vibrant political messages; it requires a profound revision of the concepts and technologies on which industrial chemical processes rely. Only a small fraction of molecules extracted from biomass bears significant chemical and commercial potentials to be considered as ubiquitous chemical platforms upon which a new, bio-based industry can thrive. Owing to its inherent assets in terms of unique process experience, scalability, and reduced environmental footprint, flow chemistry arguably has a major role to play in this context. This review covers a selection of C2 to C6 bio-based chemical platforms with existing commercial markets including polyols (ethylene glycol, 1,2-propanediol, 1,3-propanediol, glycerol, 1,4-butanediol, xylitol, and sorbitol), furanoids (furfural and 5-hydroxymethylfurfural) and carboxylic acids (lactic acid, succinic acid, fumaric acid, malic acid, itaconic acid, and levulinic acid). The aim of this review is to illustrate the various aspects of upgrading bio-based platform molecules toward commodity or specialty chemicals using new process concepts that fall under the umbrella of continuous flow technology and that could change the future perspectives of biorefineries.

Hollow zeolite microspheres as a nest for enzymes: a new route to hybrid heterogeneous catalysts.

In the field of heterogeneous catalysis, the successful integration of enzymes and inorganic catalysts could pave the way to multifunctional materials which are able to perform advanced cascade reactions. However, such combination is not straightforward, for example in the case of zeolite catalysts for which enzyme immobilization is restricted to the external surface. Herein, this challenge is overcome by developing a new kind of hybrid catalyst based on hollow zeolite microspheres obtained by the aerosol-assisted assembly of zeolite nanocrystals. The latter spheres possess open entry-ways for enzymes, which are then loaded and cross-linked to form cross-linked enzyme aggregates (CLEAs), securing their entrapment. This controlled design allows the combination of all the decisive features of the zeolite with a high enzyme loading. A chemo-enzymatic reaction is demonstrated, where the structured zeolite material is used both as a nest for the enzyme and as an efficient inorganic catalyst. Glucose oxidase (GOx) ensures the in situ production of H2O2 subsequently utilized by the TS-1 zeolite to catalyze the epoxidation of allylic alcohol toward glycidol. The strategy can also be used to entrap other enzymes or combination of enzymes, as demonstrated here with combi-CLEAs of horseradish peroxidase (HRP) and glucose oxidase. We anticipate that this strategy will open up new perspectives, leveraging on the spray-drying (aerosol) technique to shape microparticles from various nano-building blocks and on the entrapment of biological macromolecules to obtain new multifunctional hybrid microstructures.

Biocatalytic transamination in a monolithic flow reactor: improving enzyme grafting for enhanced performance.

Transaminases were immobilized onto macrocellular silica monoliths and used for carrying a continuous flow mode transamination reaction. Monoliths were prepared via an emulsion-templated sol-gel method and functionalised by amino-moieties (3-aminopropyl-triethoxysilane, APTES) in order to covalently immobilize the enzymes, using glutaraldehyde as a cross-linking agent. In order to obtain higher performance and improved reproducibility, we investigate the key parameters of APTES functionalisation and of enzyme grafting. Four functionalisation protocols were studied. We show that enhancing the homogeneity of the APTES grafting and controlling the moisture level during functionalisation led to a 3-fold increase in activity as compared to the previously reported data, and greatly improved the reproducibility. Additionally, we report a strong beneficial effect of running the enzyme immobilisation at room temperature instead of 4 °C, further enhancing the obtained activity. Finally, the popular method which consists of stabilizing the covalent attachment of the enzyme by reducing the imine bonds formed between the enzyme and the functionalised surface was investigated. We highlight a strong enzyme deactivation caused by cyanoborohydride, making this strategy irrelevant in this case. The improvements presented here led to more active macrocellular monoliths, of general interest for continuous flow mode biocatalysis.

Sustaining the Transition from a Petrobased to a Biobased Chemical Industry with Flow Chemistry.

In the current context of transitioning to more sustainable chemical processes, the upgrading of biobased platform molecules (i.e., the chemical transformation of widely available low molecular weight entities from biomass) is attracting significant attention, in particular when combined with enabling continuous flow conditions. The success of this combination is largely due to the ability to explore new process conditions and the perspective of facilitating seamless scalability while maintaining a small overall footprint. This review considers representative continuous flow processes which utilize a selection of currently popular platform molecules that target industrially relevant building blocks, including (a) commodity chemicals, (b) specialty and fine chemicals, and (c) fuels and fuel additives.

Novel ceramic paper structures for diesel exhaust purification.

The catalytic combustion of diesel soot is addressed with flexible and structured "paper catalysts". Two different series of catalysts were prepared either by drip impregnation or by a spray method to deposit a mixture of Co, Ba, and K or a mixture of Co and Ce onto SiO2-Al2O3 ceramic paper matrixes. In every case, CeO2 nanoparticles were added to bind the ceramic fibers. SEM images showed that the impregnation method generated catalytic particles concentrated as large chunks (> 10 µm), mainly at ceramic fiber crossings, whereas the spray method produced smaller catalytic particles (< 1 µm) well distributed throughout the ceramic paper. Besides, Co-Ba-K particles appeared better dispersed on the surface of ceramic fibers than Co-Ce due to the presence of K. Additionally, FTIR spectra showed the formation of O22- and O2- species associated with CeO2 (binder) on the samples containing potassium which gave the Co-Ba-K-ceramic paper good catalytic properties, thus making the Co-Ba-K drop impregnated the best catalyst both considering activity and stability. Successive temperature programmed oxidation (TPO) runs up to 700 °C caused the formation of cobalt silicates in the catalytic ceramic paper prepared by the spray method, as indicated by TPR. The formation of these species was probably favored by the smaller size of cobalt particulates and their higher dispersion in the catalysts prepared by the spray method. This provoked the partial loss of the redox properties of Co3O4. TPR experiments also indicated the formation of BaCoO3 in Ba-containing ceramic paper, which could help in maintaining the catalyst activity after several TPO runs through the capacity of this mixed perovskite-type oxide to trap and release NOx.

Thickness Characterization Toolbox for Transparent Protective Coatings on Polymer Substrates.

The thickness characterization of transparent protective coatings on functional, transparent materials is often problematic. In this paper, a toolbox to determine the thicknesses of a transparent coating on functional window films is presented. The toolbox consists of a combination of secondary ion mass spectrometry and profilometry and can be transferred to other transparent polymeric materials. A coating was deposited on designed model samples, which were characterized with cross-sectional views in transmission and in scanning/transmission electron microscopy and ellipsometry. The toolbox was then used to assess the thicknesses of the protective coatings on the pilot-scale window films. This coating was synthesized using straightforward sol-gel alkoxide chemistry. The kinetics of the condensation are studied in order to obtain a precursor that allows fast drying and complete condensation after simple heat treatment. The shelf life of this precursor solution was investigated in order to verify its accordance to industrial requirements. Deposition was performed successfully at low temperatures below 100 °C, which makes deposition on polymeric foils possible. By using roll-to-roll coating, the findings of this paper are easily transferrable to industrial scale. The coating was tested for scratch resistance and adhesion. Values for the emissivity (ε) of the films were recorded to justify the use of the films obtained as infrared reflective window films. In this work, it is shown that the toolbox measures similar thicknesses to those measured by electron microscopy and can be used to set a required thickness for protective coatings.

Aerosol processing: a wind of innovation in the field of advanced heterogeneous catalysts.

Aerosol processing is long known and implemented industrially to obtain various types of divided materials and nanomaterials. The atomisation of a liquid solution or suspension produces a mist of aerosol droplets which can then be transformed via a diversity of processes including spray-drying, spray pyrolysis, flame spray pyrolysis, thermal decomposition, micronisation, gas atomisation, etc. The attractive technical features of these aerosol processes make them highly interesting for the continuous, large scale, and tailored production of heterogeneous catalysts. Indeed, during aerosol processing, each liquid droplet undergoes well-controlled physical and chemical transformations, allowing for example to dry and aggregate pre-existing solid particles or to synthesise new micro- or nanoparticles from mixtures of molecular or colloidal precursors. In the last two decades, more advanced reactive aerosol processes have emerged as innovative means to synthesise tailored-made nanomaterials with tunable surface properties, textures, compositions, etc. In particular, the "aerosol-assisted sol-gel" process (AASG) has demonstrated tremendous potential for the preparation of high-performance heterogeneous catalysts. The method is mainly based on the low-cost, scalable, and environmentally benign sol-gel chemistry process, often coupled with the evaporation-induced self-assembly (EISA) concept. It allows producing micronic or submicronic, inorganic or hybrid organic-inorganic particles bearing tuneable and calibrated porous structures at different scales. In addition, pre-formed nanoparticles can be easily incorporated or formed in a "one-pot" bottom-up approach within the porous inorganic or hybrid spheres produced by such spray drying method. Thus, multifunctional catalysts with tailored catalytic activities can be prepared in a relatively simple way. This account is an overview of aerosol processed heterogeneous catalysts which demonstrated interesting performance in various relevant chemical reactions like isomerisation, hydrogenation, olefin metathesis, pollutant total oxidation, selective oxidation, CO2 methanation, etc. A short survey of patents and industrial applications is also presented. Our objective is to demonstrate the tremendous possibilities offered by the coupling between bottom up synthesis routes and these aerosol processing technologies which will most probably represent a major route of innovation in the mushrooming field of catalyst preparation research.