Dehydrogenative cyclization of 1,4-butanediol over copper-based catalyst

Chemical transformation of polyurethane into valuable polymers

Polyurethanes are an important class of synthetic polymers, widely used in a variety of applications ranging from everyday items to advanced tools in societal infrastructure. Their inherent cross-linked structure imparts exceptional durability and flexibility, yet this also complicates their degradation and recycling. Here we report a heterogeneous catalytic process that combines methanolysis and hydrogenation with a CO2/H2 reaction medium, effectively breaking down PU waste consisting of urethane and ester bonds into valuable intermediates like aromatic diamines and lactones. These intermediates are then converted into functional polymers: polyimide (PI), noted for its exceptional thermal and electrical insulation, and polylactone (P(BL-co-CL)), a biodegradable alternative to traditional plastics. Both polymers exhibit enhanced performance compared to existing commercial products. This approach not only contributes to the valorization of plastic waste but also opens new avenues for the creation of high-performance materials.

One-pot redox cascade paired electrosynthesis of gamma-butyrolactone from furoic acid

The catalytic valorisation of biomass to afford synthetically useful small molecules is essential for sustainable biorefinery processes. Herein, we present a mild cascaded electrochemical protocol for converting furoic acid, a common biomass-derived feedstock, into a versatile platform chemical, gamma-butyrolactone. In the platinum(+)|nickel(-) electrode paired undivided cell, furoic acid is electrochemically oxidised with 84.2% selectivity to 2(5H)-furanone, the olefin of which is then hydrogenated to yield gamma-butyrolactone with 98.5% selectivity. The final gamma-butyrolactone yield is 69.1% with 38.3% Faradaic efficiency and 80.1% carbon balance when the reaction is performed with 100 mM furoic acid at 80 °C at +2.0 VAg/AgCl. Mechanistic investigation revealed the critical temperature and electrolyte pH conditions that maximise the production and protection of the key intermediate, furan radical, promoting its transition to 2(5H)-furanone rather than self-polymerising. The reaction is scalable, as 2.1 g of 98.1% pure gamma-butyrolactone is isolated through a simple solvent extraction.

Renewable synthesis of γ-butyrolactone from biomass-derived 2-furanone using palladium supported on humin-derived activated carbon (Pd/HAC) as a heterogeneous catalyst

This work reports a high-yielding synthesis of γ-butyrolactone (GBL), a promising biofuel, renewable solvent, and sustainable chemical feedstock, by the catalytic hydrogenation of 2-furanone. 2-Furanone can be synthesized renewably by the catalytic oxidation of xylose-derived furfural (FUR). Humin, produced during the preparation of FUR from xylose, was carbonized to form humin-derived activated carbon (HAC). Palladium supported on humin-derived activated carbon (Pd/HAC) was used as an efficient and recyclable catalyst for hydrogenating 2-furanone into GBL. The process was optimized in various reaction parameters, such as temperature, catalyst loading, hydrogen pressure, and solvent. Under optimized conditions (RT, 0.5 MPa H₂, THF, 3 h), the 4% Pd/HAC (5 wt% loading) catalyst afforded GBL in an 89% isolated yield. Under identical conditions, an 85% isolated yield of γ-valerolactone (GVL) was obtained starting from biomass-derived angelica lactone. Moreover, the Pd/HAC catalyst was conveniently recovered from the reaction mixture and successfully recycled for five consecutive cycles with only a marginal decrease in the yield of GBL.

Kinetic Modeling for the Gas-Phase Hydrogenation of the LOHC γ-Butyrolactone–1,4-Butanediol on a Copper-Zinc Catalyst

Liquid organic hydrogen carriers (LOHCs) are an interesting alternative for hydrogen storage as the method is based on the reversibility of hydrogenation and dehydrogenation reactions to produce liquid and safe components at room temperature. As hydrogen storage involves a large amount of hydrogen and pure compounds, the design of a three-phase reactor requires the study of gas and liquid-phase kinetics. The gas-phase hydrogenation kinetics of LOHC γ-butyrolactone/1,4-butanediol on a copper-zinc catalyst are investigated here. The experiments were performed with data, taken from the literature, in the temperature and pressure ranges 200–240 °C and 25–35 bar, respectively, for a H2/γ-butyrolactone molar ratio at the reactor inlet of about 90. The best kinetic law takes into account the thermodynamic chemical equilibrium, is based on the associative hydrogen adsorption and is able to simulate temperature and pressure effects. For this model, the confidence intervals are at most 28% for the pre-exponential factors and 4% for the activation energies. Finally, this model will be included in a larger reactor model in order to evaluate the selectivity of the reactions, which may differ depending on whether the reaction takes place in the liquid or gas phase.

Copper–Zirconia Catalysts: Powerful Multifunctional Catalytic Tools to Approach Sustainable Processes

Copper–zirconia catalysts find many applications in different reactions owing to their unique surface properties and relatively easy manufacture. The so-called methanol economy, which includes the CO2 and CO valorization and the hydrogen production, and the emerging (bio)alcohol upgrading via dehydrogenative coupling reaction, are two critical fields for a truly sustainable development in which copper–zirconia has a relevant role. In this review, we provide a systematic view on the factors most impacting the catalytic activity and try to clarify some of the discrepancies that can be found in the literature. We will show that contrarily to the large number of studies focusing on the zirconia crystallographic phase, in the last years, it has turned out that the degree of surface hydroxylation and the copper–zirconia interphase are in fact the two mostly determining factors to be controlled to achieve high catalytic performances.

The selectively regulated vapour phase dehydrogenation of 1,4-butanediol to γ-butyrolactone employing a copper-based ceria catalyst

Copper-based ceria catalysts were synthesized for the dehydrogenation of 1,4-BDO to GBL and results exhibited a conversion of 93% and 98% selectivity with stable activity for up to 7 h.

Dehydrogenative coupling promoted by copper catalysts: a way to optimise and upgrade bio-alcohols

A one-pot one-step transformation of butanol into butyl butanoate takes place with excellent yield on a Cu/ZrO₂ catalyst.

Dehydrogenative lactonization of diols with a platinum-loaded titanium oxide photocatalyst

The Pt loaded rutile TiO₂ photocatalyst promotes the dehydrogenative lactonization of diols. The reaction rate is improved by the addition of Al₂O₃.

Unusual effect of cobalt on Cu–MgO catalyst for the synthesis of γ-butyrolactone and aniline via coupling reaction

Addition of cobalt to Cu–MgO catalyst elevated the yields of γ-butyrolactone and aniline significantly from 1,4-butanediol and nitrobenzene via hydrogenation and dehydrogenation coupling process.

Acceptorless dehydrogenative lactonization of diols by Pt-loaded SnO2 catalysts

SnO₂-supported platinum (Pt/SnO₂) effectively catalyzed the acceptorless dehydrogenative lactonization of benzylic and aliphatic diols under solvent-free conditions in N₂.

Upgrading of diols by gas-phase dehydrogenation and dehydration reactions on bifunctional Cu-based oxides

A bifunctional ZCuMgAl (Z = 0.3–61.2 wt.% Cu) catalyst converts biomass-derived diols into valuable hydroxyketones or saturated and unsaturated ketones and alcohols depending on the Cu loading.

Reduction of Aldehydes and Ketones by Transfer Hydrogenation with 1,4-Butanediol

1,4-Butanediol has been used as the hydrogen donor in transfer hydrogenation reactions. The equilibrium is driven by the formation of gamma-butyrolactone, and the diol is therefore not required in excess.