Recycling of Flexible Polyurethane Foam by Split-Phase Alcoholysis: Identification of Additives and Alcoholyzing Agents to Reach Higher Efficiencies.

Split-phase alcoholysis of flexible polyurethane (PU) foam yields an apolar phase containing the recycled polyether polyol, and a lower, polar phase of the alcoholyzing agent and aromatic compounds. However, multiple purification steps are required to render the polyether polyol suitable for synthesis of new flexible PU foams; the unfavorable mass balance limits industrial applications. In this work, 2-pyrrolidone was identified as a performant additive for accelerating the dissolution and depolymerization process. By applying a lactam to PU foam in a weight ratio of 0.1:1, the glycol to PU foam weight ratio can be decreased from 1.5:1 to only 0.5:1, without loss of purity or yield of the recycled polyether polyol. Diglycerol was discovered as a novel, promising alcoholyzing agent; it allows the recycling of the polyether polyol in high purity (97 %) and excellent yields (98 %), and after a single washing with diglycerol, a sufficiently low hydroxyl value (61 mgKOH g-1 ) is reached. The recycled polyether polyol can replace the virgin polyether polyol (48 mgKOH g-1 ) for up to 50 % in the synthesis of new flexible PU foams with effects on the foam quality that stay within the limits of generally accepted specifications. A first step towards the valorization of the lower phase was also taken by applying hydrolysis of the newly formed carbamates to toluenediamines, which are readily reintegrated in new PU foams.

Protein-Rich Biomass Waste as a Resource for Future Biorefineries: State of the Art, Challenges, and Opportunities.

Protein-rich biomass provides a valuable feedstock for the chemical industry. This Review describes every process step in the value chain from protein waste to chemicals. The first part deals with the physicochemical extraction of proteins from biomass, hydrolytic degradation to peptides and amino acids, and separation of amino acid mixtures. The second part provides an overview of physical and (bio)chemical technologies for the production of polymers, commodity chemicals, pharmaceuticals, and other fine chemicals. This can be achieved by incorporation of oligopeptides into polymers, or by modification and defunctionalization of amino acids, for example, their reduction to amino alcohols, decarboxylation to amines, (cyclic) amides and nitriles, deamination to (di)carboxylic acids, and synthesis of fine chemicals and ionic liquids. Bio- and chemocatalytic approaches are compared in terms of scope, efficiency, and sustainability.

Synthesis and characterisation of alkyd resins with glutamic acid-based monomers.

Alkyd resins are versatile polymers which have applications in inks and various coatings like decorative paints. They are mainly composed of fatty acids, polyols and aromatic diacids. In this work, glutamic acid as well as N-acylated and N-alkylated derivatives there of were evaluated as bio-based substitutes for these aromatic diacid monomers in the synthesis of alkyd resins. The resins were characterised in terms of structure, molecular weight, viscosity, oxidative thermal stability and colour. N-Palmitoylglutamic acid dimethyl ester can be successfully incorporated when the polycondensation is performed in two steps. In this approach, the bio-based diacid monomer is only supplied in the second step, because the removal of water in the first step is essential to avoid hydrolysis of the monomer amide bond and the subsequent formation of pyroglutamate groups. The molecular weight, viscosity and oxidative thermal stability are lower than for conventional alkyd resins. The mechanism of the discolouration of alkyd resins during polymerisation is mediated by free radical species, which were generated easily in the presence of free amino groups and/or unsaturated fatty acids. Light-coloured resins could be obtained by using saturated fatty acids or radical scavengers during polymerisation.

Adsorption and Separation of Aromatic Amino Acids from Aqueous Solutions Using Metal-Organic Frameworks.

Metal-organic frameworks (MOFs) are investigated for the adsorption of aromatic amino acids l-phenylalanine (l-Phe), l-tryptophan (l-Trp), and l-tyrosine (l-Tyr) from aqueous solutions. After screening a range of water-stable MOFs, the hydrophobic Zr-MOF MIL-140C emerged as the best performing material, exhibiting uptakes of 15 wt % for l-Trp and 20 wt % for l-Phe. These uptakes are 5-10 wt % higher than those of large-pore zeolites Beta and Y. Both single-compound and competitive adsorption isotherms for l-Phe and l-Trp were experimentally obtained at the natural pH of these amino acid mixtures (pH 6.5-7) without additional pH modification. We find that the hydrophobic nature of MIL-140C and the capacity of l-Trp to form hydrogen bonds favor the uptake of l-Trp with its larger indole moiety compared to the smaller phenyl side group of l-Phe. On the basis of literature and vibrational analysis, observations of hydrogen-bonded l-Trp within the MIL-140C framework are evidenced by red- and blue-shifted -NH vibrations (3400 cm-1) in Fourier transform infrared spectroscopy, which were attributed to types N-Hl-Trp···πMIL-140C and N-Hl-Trp···OMIL-140C, respectively. MIL-140C is shown to be recycled at least three times for both aromatic amino acids without any loss of adsorption capacity, separation performance, or crystallinity. Desorption of aromatic amino acids proceeds easily in aqueous ethanol. Substantial coadsorption of negatively charged amino acids l-glutamate and l-aspartate (l-Glu and l-Asp) was observed from a model solution for wheat straw protein hydrolysate at pH 4.3. On the basis of these results, we conclude that MIL-140C is an interesting material for the recovery of essential aromatic amino acids l-Tyr, l-Phe, and l-Trp and of l-Glu and l-Asp from waste protein hydrolysates.

Ruthenium-catalyzed aerobic oxidative decarboxylation of amino acids: a green, zero-waste route to biobased nitriles.

Oxidative decarboxylation of amino acids into nitriles was performed using molecular oxygen as terminal oxidant and a heterogeneous ruthenium hydroxide-based catalyst. A range of amino acids was oxidized in very good yield, using water as the solvent.

Bio-based nitriles from the heterogeneously catalyzed oxidative decarboxylation of amino acids.

The oxidative decarboxylation of amino acids to nitriles was achieved in aqueous solution by in situ halide oxidation using catalytic amounts of tungstate exchanged on a [Ni,Al] layered double hydroxide (LDH), NH4 Br, and H2 O2 as the terminal oxidant. Both halide oxidation and oxidative decarboxylation were facilitated by proximity effects between the reactants and the LDH catalyst. A wide range of amino acids was converted with high yields, often >90 %. The nitrile selectivity was excellent, and the system is compatible with amide, alcohol, and in particular carboxylic acid, amine, and guanidine functional groups after appropriate neutralization. This heterogeneous catalytic system was applied successfully to convert a protein-rich byproduct from the starch industry into useful bio-based N-containing chemicals.