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Polymeric materials play a key role in modern industry. Owing to outstanding and very versatile properties of polymers, they have rather quickly occupied the great niche of commodities. World plastic production is continuously growing from 1.7 Mton/year in 1950 to 288 Mton/year in 2012. Fossil sources are still required for production of the major part of polymers, as only 5% of chemicals are currently produced from renewable feedstocks. Nevertheless, the application of natural chemicals as feedstocks for the manufacture of polymers is steadily increasing. Different motivations induce such a high interest toward new biobased materials. First of all, the global depletion of petroleum resources and their uneven spread over the world stimulate the rational use of biomass as a renewable and ubiquitous resource. Additionally, overwhelming of dumps with nondegradable plastics causes serious ecological problems, stimulating the developments toward new biodegradable materials. Here we have to point at the distinction between the terms “biobased” and “biodegradable”. Biobased products are manufactured from renewable sources, but several examples of biobased and nonbiodegradable products, e.g., biopolyethylene, biopolyamide 11, exist. It should be noted that each new material has to be tested for biodegradability before it can be claimed to be so. For example, linear polymers produced from itaconic acid are biodegradable, but cross-linking of the polymer chains slows down the biodegradation

The depolymerization of lignocellulosic feedstock with a heterogeneous composition is a major challenge and usually leads to the formation of monosaccharides as the main products. Our work aims to convert such feedstocks into oligomeric glycans which are more valuable products compared to sugars, by using mechanocatalysis in a planetary ball mill as an effective conversion route. Herein, we utilized raw materials such as wheat straw, beet pulp, cocoa shells and apple pomace as residual natural raw materials from food and feed production. Reaction parameters such as rotational speed, acid content and milling duration were investigated and optimized towards a maximum amount of soluble species and a minimum of monosaccharides. The optimization of cellulose as a substrate resulted in a nearly fully soluble fraction containing oligomeric glycans. Based on these results the reaction parameters were transferred and further optimized for lignocellulosic feedstock. For wheat straw a solubility of over 90% was achieved comprising a mixture of oligomeric glycans as well as partially depolymerized lignin.

The thriving research and development in additive manufacturing and especially 3D printing in chemical engineering and heterogeneous catalysis enables novel and innovative approaches for the shaping of catalysts. In this work, tailor-made monoliths with complex transport pore channels are designed and printed by fused deposition modelling (FDM) from polystyrene filament. Subsequently, sulfonic acid groups are introduced by sulfonation for a catalytic functionalization of the structured monoliths’ accessible inner surface. As a catalytic test reaction, the aqueous phase hydrolysis of sucrose was chosen. For this reaction the functionalized monoliths exhibited a superior catalytic performance in both batch and continuous reaction mode in comparison to a macroporous sulfonic acid-functionalized ion exchange resin as commercial benchmark catalyst. This is due to the higher accessibility of the sulfonic acid groups on the surface of the monoliths’ pore channels and hence, enhanced effective reaction kinetics by decreased mass transfer limitations.

Despite the great potential of metal-organic frameworks (MOFs) in catalysis, industrial applications are still scarce. This is mainly due to a lack of performance when changing from idealized lab conditions towards realistic conditions of the actual application. In this work, we demonstrate the applicability and outstanding catalytic performance of an alumina-supported [Pd(2-pymo)₂]n MOF catalyst in the selective hydrogenation of acetylene to ethylene under industrial front-end conditions. It shows a competitive performance to an industrial benchmark catalyst and even exceeds it in terms of ethane selectivity due to the combination of well-defined isolated Pd active sites and synergies due to MOF-support-interactions. The high stability was proven for up to 60 h time-on-stream and supported by XPS and XRD structural analysis.

The catalytic conversion of biomass and biogenic platform chemicals typically requires the use of solvents. Water is present already in the raw materials and in most cases a suitable solvent for the typically highly polar substrates. Hence, the development of novel catalytic routes for further processing would profit from the optimization of the reaction conditions in the aqueous phase mainly for energetic reasons by avoiding the initial water separation. Herein, we report the amination of biogenic alcohols in aqueous solutions using solid Ru-based catalysts and ammonia as a reactant. The influence of different support materials and bimetallic catalysts is investigated for the amination of isomannide as a biogenic diol. Most importantly, the transferability of the reaction conditions to various other primary and secondary alcohols is successfully proved. Hence, water appears to be a suitable solvent for the sustainable production of biogenic amines and offers great potential for further process development.

Efficient base-modulated product selectivity in the aqueous-phase Ru/C-catalyzed reductive amination of 1,6-hexanediol (HDO) was reported by performing the reaction at mild conditions (463 K, 25 bar H2). High selectivity of amines could be controlled by the addition of different bases; for example, Cs2CO3 addition gave a high yield of 6-amino-1-hexanol (AH, 26%). However, the addition of Ba(OH)2 resulted in the formation of high yield of secondary amination products, hexamethylenediamine (HMDA, 34%) and azepane (26%). The hydroxide base, especially Ba(OH)2, aids in the initial conversion of HDO to AH by significantly decreasing the apparent activation energy from 68 to 48 kJ mol–1. A closer analysis of the formation of secondary products (azepane and HMDA) revealed a faster reaction between NH3 and the carbonyl-containing intermediate by the addition of Ba(OH)2 into the reaction solution.

Isosorbide is considered a versatile biogenic platform compound for the production of chemicals. The functionalization of its two hydroxyl groups is challenging since they exhibit a different configuration and thus, different reactivity as well as sterical accessibility. We investigated the formation of the respective tert-butyl ethers by an addition reaction of isosorbide to isobutene heterogeneously catalyzed by acidic ion exchange resins. An efficient liquid phase process under ambient conditions in a batch reactor has been developed. The reaction network was unravelled by detailed investigation of the reaction kinetics. Additionally, the feasibility of continuous processing was successfully demonstrated on the lab-scale applying a continuously stirred-tank reactor.

We report for the first time a metal-free heterogeneously catalyzed hydrogenation using a semi-solid frustrated Lewis pair (FLP). The catalyst consists of a solid polyamine organic framework and molecular tris(pentafluorophenyl)borane (BCF) that form a semi-immobilized FLP in situ in the catalytic hydrogenation of diethyl benzylidenemalonate. 11B NMR spectroscopy proves the successful hydrogen activation by the FLP. Furthermore, the B−N interactions between the polyamine and BCF are investigated by IR and solid state NMR spectroscopy. The FLP 1,4-diazabicyclo[2.2.2]octane (DABCO)/BCF, which combines the features of a FLP and a classical Lewis adduct, functions as molecular reference in both, catalysis and characterization. Furthermore, computational studies enable a better insight into the hydrogen activation through DABCO/BCF and polyamine/BCF.

The combination of the advantageous properties of molecular and solid catalysts is considered the “Holy Grail” in catalysis research. Great potential is provided by nanoporous polymers. Chemically well-defined moieties in combination with a high stability render these materials suitable as catalyst supports for liquid-phase and even aqueous-phase catalytic processes, especially regarding the transition from fossil resources to renewable resources. In this Minireview, recent developments are summarized, covering the three main approaches: solid metal-free organocatalysts, immobilized molecular catalyst species, and supported metal nanoparticles and clusters. Their potential is evaluated and the question as to whether nanoporous polymers can bridge the gap between homogeneous and heterogeneous catalysis is critically discussed.

Herein, we describe a one-step process for renewable aromatics from biomass-derived ketones over solid acid catalysts under liquid phase batch and flow conditions. The ion exchange resin was highly active for aromatics due to high acidic strength but leaching of acidic sites caused low stability. In contrary, zeolite HY showed a lower activity but higher stability in batch by regenerability and was stable in flow for 250 min-on-stream. HY is further applicable for the conversion of higher ketones (butanone and pentanone). This work contributes towards an industrially important aromatic production from biogenic ketones and thus an economical and sustainable process.

Aromatization of alkyl methyl ketones obtained from biorefinery streams is a viable and attractive catalytic pathway to renewable aromatics, precursors for various important monomers and chemicals. To achieve high catalytic activity and stability under continuous conditions, mesoporous amorphous silica-alumina (ASA) catalysts are studied for the acid-catalyzed self-condensation of biomass-derived acetone to mesitylene in solvent-free conditions using a fixed-bed reactor. The catalytic efficiency of ASA catalysts depends on their structure and intrinsic acidity. In comparison to pure alumina, ASA Siralox 30 exhibits a 2.2 times higher catalytic activity for acetone conversion and 3.8 times higher mesitylene yield, demonstrating the importance of Brønsted acid sites (BAS) generated in ASA catalysts. The detailed kinetic studies and catalyst characterization indicate that mesitylene formation is favored over BAS and that the formation rate is enhanced with the relative strength of BAS. We demonstrate here that Siralox 30 (total product selectivity = 66%, W/F = 12.5 gcat h mol⁻¹) is an adequate and highly active catalyst for the continuous mesitylene synthesis with remarkable long-term operational stability (>50 hours-on-stream).

We present new element organic frameworks based on Sn, Sb and Bi atoms connected via organic linkers by element-carbon bonds. The open frameworks are characterized by specific surface areas (BET) of up to 445 m² g⁻¹ and a good stability under ambient conditions resulting from a highly hydrophobic inner surface. They show good performance as heterogeneous catalysts in the cyanosylilation of benzaldehyde as a test reaction. Due to their catalytic activity, this class of materials might be able to replace common homogeneous element-organic and often highly toxic catalysts especially in the food industry.

The copper-catalyzed electrochemical CO2 reduction reaction represents an elegant pathway to reduce CO2 emissions while producing a wide range of valuable hydrocarbons. The selectivity for these products depends strongly on the structure and morphology of the copper catalyst. However, continued deactivation during catalysis alters the obtained product spectrum. In this work, we report on the stabilizing effect of three different carbon supports with unique pore structures. The influence of pore structure on stability and selectivity was examined by high-angle annular dark field scanning transmission electron microscopy and gas chromatography measurements in a micro-flow cell. Supporting particles into confined space was found to increase the barrier for particle agglomeration during 20 h of chronopotentiometry measurements at 100 mA cm−2 resembling long-term CO2 reduction conditions. We propose a catalyst design preventing coalescence and agglomeration in harsh electrochemical reaction conditions, exemplarily demonstrated for the electrocatalytic CO2 reduction. With this work, we provide important insights into the design of stable CO2 electrocatalysts that can potentially be applied to a wide range of applications.

Porous organic framework materials such as hypercrosslinked polymers (HCP) show a high chemical stability and dynamic behavior in a variety of solvents while their pore properties exhibit great potential for mixed matrix membrane (MMM) applications. However, their influence as porous filler in MMMs, especially for applications in liquid-phase filtration is still unexploited. Herein, we demonstrate an HCP-based MMM for molecular separation in the liquid phase by nanofiltration (NF). Depending on the solvent, the membrane changes its fractional free volume by shrinking or swelling. In connection to that, the pore size is also influenced, hence, providing a tunable permeance and molecular cut-off. The reduction of the pore volume and size directly correlates to the improvement of the NF performance, while the volume increase completely diminishes it. The extraordinary flexibility and high degree of crosslinking assure permanent porosity and render the dynamic behavior fully reversible. Thereby, a solvent-responsive “on” and “off” switching of the NF properties is enabled and was experimentally proven. Overall, this provides alternative strategies regarding the fouling and regeneration of membranes as well as the inhibition of pore blocking in membrane-derived processes by a tunable separation performance.

We present the synthesis and characterization of fluorinated polymers based on P, B, Si, Sn and Ge as heteroatoms via Grignard activation. The polymers are microporous with hydrophobic surfaces. The borate-based polymer was successfully applied as solid acid catalyst in the esterification of acetic acid with ethanol. Grignard synthesis of fluorinated nanoporous element organic frameworks based on the heteroatoms P, B, Si, Sn and Ge Recently, porous polymers have attracted considerable attention as highly versatile materials for adsorption, separation and storage of gases, in catalysis, for optoelectronic applications and energy storage. Especially, metal–organic frameworks (MOFs) and covalent organic frameworks (COFs) are of interest due to their high surface areas and pore volumes. In order to tune the surface polarity, porous ionic organic networks were reported. Depending on the desired properties such as porosity, polarity and functionality, these materials can be tailored for their application by varying the organic linker and connector element. The utilization of fluorinated linkers was reported for different MOFs and a COF, showing enhanced properties in terms of stability, hydrophobicity, gas affinity and selectivity in comparison to their non-fluorinated materials. In continuation of our work on element organic frameworks (EOFs) with P, Si and Sn as connector elements, here we present the synthesis and characterization of respective fluorinated porous polymers with P, B, Si, Sn and Ge as heteroatoms. The catalytic application of the borate based polymer as solid acid catalyst was demonstrated in the esterification of acetic acid with ethanol as test reaction. As the activation of the fluorinated biphenyl linker was not successful neither via lithiation as reported for the non-fluorinated linker nor via classical Grignard reaction, a magnesium-halogen exchange was applied. The linker 4,4′-dibromooctafluorbiphenyl was activated twofold with isopropylmagnesium

Oxymethylene ethers (OME) are considered as a low-emission additive or replacement to diesel fuel. They can be synthesized by different routes based on C₁ platform chemicals in different oxidation states. The challenge is to tune the acidic catalyst for the condensation reaction to a selectivity for a certain oligomeric fraction (OME₃₋₅) for optimal fuel properties. Herein, we report the use of heteropoly acids that showed an outstanding activity and selectivity for the production of the respective OME fraction under very mild reaction conditions. Trioxane and dimethoxymethane (OME₁) were used as substrates which are both products of the methanol value-added chain. Reaction parameters such as catalyst/substrate ratio and temperature could be reduced considerably due to a high catalytic activity and selectivity. Kinetic data were obtained experimentally and modelled to estimate the reaction rate, activation energy and pre-exponential factor as a solid basis for further reaction engineering.

Epimerization of sugars is a carbon-efficient route not only to produce rare carbohydrates but also to extend the product scope for chemical production in future biorefineries. Industrially available catalysts for epimerization are limited mainly to soluble Mo(VI) species as well as substrate-specific epimerases. Here we report highly active and selective tin-organic frameworks (Sn-OF) as solid catalysts for the epimerization of aldoses at the C-2 position, such as the conversion of glucose to mannose. The reaction proceeds via a carbon skeleton rearrangement, that is, through breaking of a C-2/C-3 carbon bond and formation of a C-1/C-3 bond. Partially hydrolyzed Ph₃Sn-OH sites were found to be the catalytically active centers. Our results suggest that the high catalytic activity of Sn-OFs for the epimerization is determined by (1) Lewis acidity of tin; (2) free Sn-OH groups; and (3) the high hydrophobicity of organic linkers applied in the aqueous solutions.

In biorefinery processes often the downstream processing is the technological bottleneck for an overall high efficiency. On the basis of recent developments, the selective liquid phase adsorption applying highly hydrophobic porous materials opened up new opportunities for process development. In this contribution, the efficiency of selective liquid phase adsorption is demonstrated for the separation and purification of itaconic acid from aqueous solutions for the first time. A wide range of different adsorbents was screened, revealing the surface polarity as well as textural properties as critical parameters for their performance. Adsorption from mixed solutions of itaconic acid and glucose exhibited extraordinary high selectivities for adsorbents with highly hydrophobic surfaces, especially certain activated carbons and hyper-cross-linked polymers. Evaluation of the pH dependence showed that the respective molecular species of itaconic acid/itaconate has a major impact on the adsorption performance. Additionally, experiments on a continuously operated fixed-bed adsorber were carried out, and the desorption behavior was evaluated. Overall, the technical feasibility of the selective adsorptive removal of itaconic acid from aqueous solutions with hydrophobic adsorbents is demonstrated as a model system for an alternative technology to conventional separation strategies in biorefinery concepts.

Synthesis of high-value-added chemicals from biomass and/or biomass-derived platform molecules is considered an important strategy to mitigate the global dependency on fossil resources and include renewable resources in a circular economy. In recent years, the synthesis of bio-based plastics has received significant attention as a potential alternative to conventional industrial processes. Thus, a lot of effort has been put into the development of not only different classes of biomonomers but also bio-based drop-in chemicals. Amine-derived molecules, especially alcohol-amines, diamines, and N-heterocyclic amines, are the most important classes of functional monomers for the production of polyamides, polyimides, polyurethanes, and polyureas. Additionally, these amines are extensively used in pharmaceuticals. In this review, we will give a concise overview of the up-to-date methods for the production of industrially important amines from biomass-derived oxygenates. Special attention will be given to the catalytic amination of biomass aldehyde- and alcohol-based oxygenates, reaction mechanism, catalyst stability, as well as their specific challenges and opportunities. We anticipate this critical and comprehensive review to provide detailed insights into the synthesis of bio-based amines and guide the development of effective greener synthetic methodologies.

The need for nontoxic, cheap, earth-abundant catalysts, which can be sustainably produced and implemented, is essential to many processes. In this work we present unsupported iron nanoparticles as an efficient catalyst for selective acetylene hydrogenation under industrially relevant front-end conditions. Additionally, the selectivity and the activity of this catalyst can be easily moderated by the addition of carbon monoxide. The iron nanoparticles were prepared in an environment completely free of water or air using condensed ammonia at −78 °C. State of the art X-ray diffraction and scanning electron microscopy were used to determine the crystal structure, morphology, and purity. The catalyst showed stable performance over several experiments and, other than an agglomeration of the unsupported and unstabilized particles, no changes to the catalyst were detected before and after the reactions.

The direct conversion of (bio)ethanol and CO₂ is a promising route to diethyl carbonate (DEC) since both reactants are cheap and originate from renewable resources in bioethanol production. In this work we present a detailed characterization and correlation between catalyst synthesis parameters and catalytic activity of pure ceria for DEC formation. An interaction between surface acidity and basicity as well as sufficiently high specific surface area is required for optimal catalytic activity which is obtained by using urea as the precipitation agent. Catalytic activity towards DEC formation is increased when adding both cerium nitrate solution and aqueous ammonia solution in a controlled manner at a pH of 10 at 50 °C for precipitation. When combining temperature-programmed desorption (TPD) experiments and catalytic testing, mainly weak basic sites appear to be relevant for the DEC formation.

The utilization of biomass is one of the major challenges for the transition from fossil to renewable resources. Often, the separation of the desired product from the reaction mixture is the most energy-intensive step. Liquid-phase adsorption is a promising separation technology that could significantly improve downstream processing in biorefineries. Highly hydrophobic adsorbents were applied for the separation of lactic acid (LA) from aqueous solutions and to avoid the formation of gypsum as a byproduct. High uptakes and selectivity were obtained in single-solute and co-adsorption experiments. Porous hyper-crosslinked polymers (HCP) and polymer-based spherical activated carbon performed best and showed excellent selectivity for the selective removal of LA. Desorption experiments revealed that HCP was the ideal adsorbent for the separation of LA from aqueous solution and enabled the production of gypsum-free LA.

Sulfonation is a versatile method for the production of acidic materials, e. g. for applications in catalysis. In this study different sulfonation techniques for the production of acidic ordered mesoporous materials are investigated. SBA-15-like mesoporous organosilanes bearing aromatic moieties are sulfonated in the liquid phase with oleum as well as in the gas phase under significantly milder conditions with sulfur trioxide. Functionalization via liquid phase sulfonation at elevated temperatures proceeds at the expense of partial or complete collapse of the pore system. In contrast, gas phase sulfonation with sulfur trioxide at ambient temperature allows for similar sulfonation yields, while maintaining the textural properties due to the milder reaction conditions. Overall, acid functionalization of mesoporous organosilica using a gas phase sulfonation route is reported for the first time, enabling both high acid capacities and preservation of the pore structure.