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Catalyst-Free, Three-Component Synthesis of Amidinomaleimides
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3D printable polymer foams with tunable expansion and mechanical properties enabled by catalyst-free dynamic covalent chemistry
By leveraging dynamic phosphodiester bonds in 3D printed foams, enhanced expansion and strengths are achieved. Dynamic bonds enable higher crosslinking density and improved energy dissipation, resulting in versatile and high-performance materials.
Efficient low-temperature, catalyst-free dehydrogenation of alkanes
Steam cracking of ethane, a non-catalytic thermochemical process, remains the dominant means of ethylene production. The severe reaction conditions and energy expenditure involved in this process incentivize the search for alternative reaction pathways and reactor designs which maximize ethylene yield while minimizing cost and energy input. According to the present invention, ethylene yields as high as 68% were obtained with a quartz open tube reactor without the use of a catalyst or a cofed stream of oxidizing agents. The open tube reactor design promotes simplicity, low cost, and negligible coke formation. Reactor designs can be optimized to improve the conversion of ethane to ethylene via non-oxidative dehydrogenation, an approach which shows promise for decentralized production of ethylene from natural gas deposits.
Water-gas shift reaction in ceramic-carbonate dual-phase membrane reactor at high temperatures and pressures
Water-gas-shift (WGS) reaction is a critical step in integrated gasification combined cycles (IGCC) power plants with CO 2 capture. Membrane reactors made with a CO 2 -permselective ceramic-carbonate dual-phase (CCDP) membrane offers the potential to enhance hydrogen yield with simultaneous CO 2 capture for WGS reaction. The present work studies operation of WGS reaction in a tubular membrane reactor made of samarium-doped ceria infiltrated with lithium/sodium molten carbonate mixture. The WGS reaction was performed in the membrane reactor with and without a high-temperature WGS catalyst at 800–850 °C, feed pressure of 7 bar, the space velocity of 150–3000 h –1 , and a feed gas mixture of 45.7/13.1/41.3 mol% CO/CO 2 /N 2 with steam to carbon ratio of 4. The results show that the catalyst-free membrane reactor can convert 92% of carbon monoxide into CO 2 and H 2 and recover 29% CO 2 at 850 °C and a space velocity of 150 h –1 . However, in the catalyst-free membrane reactor, a significant amount of unwanted carbon deposition is observed. The side reactions can be minimized by reducing the operating pressure and increasing the operating temperature and space velocity, and completely avoided using a high-temperature catalyst at space velocity>500 h –1 . The membrane reactor with a WGS catalyst achieves CO conversion of about 85%, above the equilibrium conversion, and 40% CO 2 recovery without carbon deposition at high temperature and pressure. Finally, the membrane remains in the same structure and gas-tightness after the WGS reaction tests.
Heteroatom-Doped Flash Graphene
Heteroatom doping can effectively tailor the local structures and electronic states of intrinsic two-dimensional materials, and endow them with modified optical, electrical, and mechanical properties. Recent studies have shown the feasibility of preparing doped graphene from graphene oxide and its derivatives via some post-treatments, including solid-state and solvothermal methods, but they require reactive and harsh reagents. However, direct synthesis of various heteroatom-doped graphene in larger quantities and high purity through bottom-up methods remains challenging. Here, we report catalyst-free and solvent-free direct synthesis of graphene doped with various heteroatoms in bulk via flash Joule heating (FJH). Seven types of heteroatom-doped flash graphene (FG) are synthesized through millisecond flashing, including single-element-doped FG (boron, nitrogen, oxygen, phosphorus, sulfur), two-element-co-doped FG (boron and nitrogen), as well as three-element-co-doped FG (boron, nitrogen, and sulfur). Here, a variety of low-cost dopants, such as elements, oxides, and organic compounds are used. The graphene quality of heteroatom-doped FG is high, and similar to intrinsic FG, the material exhibits turbostraticity, increased interlayer spacing, and superior dispersibility. Electrochemical oxygen reduction reaction of different heteroatom-doped FG is tested, and sulfur-doped FG shows the best performance. Lithium metal battery tests demonstrate that nitrogen-doped FG exhibits a smaller nucleation overpotential compared to Cu or undoped FG. The electrical energy cost for the synthesis of heteroatom-doped FG synthesis is only 1.2 to 10.7 kJ g –1 , which could render the FJH method suitable for low-cost mass production of heteroatom-doped graphene.
Closed‐Loop Recyclable Vitrimer Plastics from PET Waste: A Design for Circularity
Plastics are essential to modern society, but their low recycling rates and inefficient end-of-life management pose a significant environmental challenge. Herein, the efficient strategy for upcycling postconsumer poly(ethylene terephthalate) (PET) waste into robust, closed-loop recyclable vitrimer plastics and composites is presented to address this issue. The catalyst-free aminolysis utilizes readily available amines to deconstruct diverse PET wastes into macromonomers, which are upcycled into vitrimers, exhibiting superior mechanical properties and exceeding the ultimate tensile stress and Young's Modulus of virgin PET by 80% and 150% respectively. These vitrimers exhibit excellent healability, shape memory, thermal reprocessability, and closed-loop chemical recyclability, enabling quantitative macromonomer recovery even from mixed plastic waste streams and glass/carbon fiber reinforced vitrimer (G/CFRV) composites. Furthermore, the vitrimer resin yields robust GFRV and CFRV composites with tensile strengths exceeding those of traditional epoxy composites by 100% and 80%, respectively, while maintaining complete chemical recyclability of both constituent materials. A preliminary technoeconomic analysis confirms the costeffectiveness and competitiveness of the facile PET deconstruction approach, which is potentially adaptable to other condensation polymers. Further, this study presents a facile approach to upcycling plastic waste into circular plastics and composites, offering a sustainable solution to global plastic waste management and fostering a circular economy.
Boosting the performances of protonic solid oxide fuel cells for co-production of propylene and electricity from propane by integrating thermo- and electro- catalysis
Protonic solid oxide fuel cells (p-SOFC) integrated with clean thermal energy sources are promising platforms for decarbonized chemical production in addition to power generation, such as on-purpose propylene production from propane dehydrogenation (PDH). The catalytic performance of the conventional nickel-cermet-based anode materials in p-SOFC for propane conversion is restrained by their low active surface area and proneness to coking. In this work, by integration of a highly efficient industry-relevant thermal catalyst PtGa/ZSM-5 for PDH reaction, we demonstrate that both the electrochemical and catalytic performance of the propane-fueled p-SOFC can be effectively enhanced. The PtGa catalyst integrated p-SOFC exhibits a peak power density of 93 mW cm -2 at 600°C, which is greater by about 100% and 50% than that without catalyst or with a perovskite-based (Pr 0.3 Sr 0.7 ) 0.9 Ni 0.1 Ti 0.9 O 3 (PSNT) catalyst layer, respectively. The PDH activity and olefin selectivity of the PtGa catalyst is also significantly higher than that of the PSNT catalyst. In addition, much improved coke tolerance and propylene selectivity (over 90%) compared to the catalyst-free Ni-cermet anode materials were achieved by integrating the industrial catalyst layer. The propane conversion can be further improved by an applied current density, whereas the olefin selectivity is almost unaltered. The excellent performance of the PtGa catalyst integrated p-SOFC is attributed to the high surface area, intrinsically high catalytic activity, selectivity, and anti-coking properties of the catalytic layer for propane conversion. In conclusion, this work provides a general approach and a case study for boosting the performances of p-SOFCs in chemical production by integrating thermo- and electro- catalysis.
Methane pyrolysis by Joule heating for graphitic carbon and hydrogen production
The global energy transition toward sustainability requires technologies that can decarbonize energy carriers and fuels while producing valuable materials. Methane, a primary component of natural gas, is both a high-energy-density fuel and a significant greenhouse gas. This study reports an approach for methane pyrolysis utilizing Joule heating within the deposition substrate to drive the endothermic reaction. With electric current passing through a resistive porous carbon cloth, heat is generated to break C-H bonds of methane molecules. Here, the decomposition of methane as it flows through the cloth results in hydrogen production and the formation of conformally layered graphite around the carbon fibers. The effects of input power, chamber pressure, feedstock flow rate, and process duration on hydrogen and graphite production are characterized via in situ mass spectrometry and laser absorption spectroscopy, resulting in methane conversion rates up to 88%, with hydrogen and carbon yields of 82% and 72%, respectively. Material characterization verifies uniform high-quality graphite deposition, with a Raman I D /I G ratio of 0.1 and 3.38 Å d-spacing. This Joule heating method for catalyst-free methane pyrolysis offers the potential for advancing hydrogen production technology by simultaneously producing valuable materials such as solid graphite, thus enhancing the economic viability of the fuel decarbonization process.
Exchangeable Liquid Crystalline Elastomers: Enabling Rapid Processing and Enhanced Actuation Stability through On-Demand Deactivation
Exchangeable liquid crystalline elastomers (xLCEs) bearing dynamic covalent bonds are promising candidates for soft actuators due to their unique capability to adjust both network structure and liquid crystalline (LC) alignment after polymerization. While current xLCEs with low exchange temperatures are convenient for processing, they suffer from issues such as creep and loss of LC alignment during repeated thermal actuation. Herein, we present an effective solution using dynamic anhydride chemistry within a thiol-ene-based xLCE. This approach enables a catalyst-free, low-temperature bond exchange of the xLCE after polymerization, allowing for the adjustment of LC orientation under mild conditions. More importantly, it enables on-demand deactivation of the bond exchange via anhydride hydrolysis, effectively eliminating creep and enhancing actuation stability for over 100 cycles. Furthermore, the hydrolysis process results in the formation of carboxylic acid groups, which can be converted into carboxylates via alkali treatment, thereby providing the xLCE with humidity responsiveness. Finally, these findings highlight the use of dynamic anhydride bonds in the fabrication and optimization of xLCEs with enhanced durability and functionality, which is expected to facilitate significant advancements in their applications in soft actuators and robotics.
Oxidative Functionalization of Long-Chain Liquid Alkanes by Pulsed Plasma Discharges at Atmospheric Pressure
In this work, we introduce the oxidation of long aliphatic alkanes using non-thermal, atmospheric plasma processing as an eco-friendly route for organic synthesis. A pulsed dielectric barrier discharge in He/O 2 gas mixtures was employed to functionalize n-octadecane. C 18 secondary alcohols and ketones were the main products, with an optimal molar yield of ~29.2%. Prolonged treatment resulted in the formation of dialcohols, diketones, and higher molecular weight oxygenates. Lighter hydrocarbon products and decarboxylation to CO 2 were also observed at longer treatment times and higher power inputs. A maximum energy yield of 5.48 × 10 –8 mol/J was achieved at short treatment times and high powers, associated with higher selectivity to primary oxygenates. Direct hydroxylation of alkyl radicals, as well as disproportionation reactions, are proposed as the main pathways to alcohols and ketones. The results hold promise for functionalizing long hydrocarbon molecules at ambient conditions using catalyst-free plasma discharges.
Direct Conversion of Ethane to Oxygenates, Ethylene, and Hydrogen in a Noncatalytic Biphasic Plasma Microreactor
We selectively upgrade ethane (C 2 H 6 ) to ethanol (C 2 H 5 OH), methanol (CH 3 OH), and acetic acid (CH 3 COOH) in a catalyst-free, continuous, argon/water biphasic plasma microreactor. The water (H 2 O) evaporates and electron- dissociates into OH· radicals. OH· recombines with alkyl radicals, produced via electron dissociation of ethane, to generate the oxygenates that absorb into H 2 O. A plasma-assisted path, reminiscent of the low-temperature thermocatalytic ethane steam reforming, leads to significant H 2 coproduction. The gaseous stream also comprises CO 2 and C 2 H 4 . Up to 1.3 and 1 μmol min –1 of liquid C 2 H 5 OH and CH 3 OH are attained, respectively. Compared to CO 2 -assisted ethane plasma conversion, which produces many oxygenates with low selectivity, the carbon selectivity can range from >70% C 2 H 5 OH, CH 3 OH, and CH 3 COOH to 60% C 2 H 4 . Furthermore, the low carbon footprint, electrified, modular, intensified process using a reactive evaporation and separation plasma could pave the way for the valorization of underutilized shale gas resources in remote areas.
Synthesis of Bio-Based Repairable Polyimines with Tailored Properties by Lignin Fractionation
Developing sustainable polymers with low-value lignin remains a challenge. Herein, lignin-containing repairable polyimines were synthesized with tailored properties using lignin fractionation. First, softwood Kraft lignin is fractionated into a more homogeneous fraction with a lower molecular weight and a higher OH content. Next, Kraft lignin and its fraction are esterified by levulinic acid to introduce active ketone groups and subsequently condensed with oleylamine (OAm) and bis(3-aminopropyl)-terminated polydimethylsiloxane (PDMS) via a catalyst-free Schiff-base reaction to form grafted lignin-OAm copolymers and cross-linked lignin-PDMS polymer networks (MKL-P and MFL-P), respectively. Results show that lignin-OAm polyimines can be self-repaired and hot reprocessed under pressure, while lignin-PDMS polyimines can be repaired with the assistance of a healing agent, heat, and pressure. Dynamic mechanical analyses demonstrate that the stress–relaxation behaviors of the polyimines follow the Arrhenius law under thermal-stress activation, indicating the occurrence of transimination. Moreover, compared with Kraft lignin, the lignin fraction ameliorates the grafting density of ketones and enhances the cross-linking density of lignin-PDMS polyimine networks. The higher cross-linking density of MFL-P leads to superior stress–relaxation activation energy, thermal stability, hydrophobicity, and light-shielding ability but inferior repairability and translucency. Finally, this work provides insights into the polymerization of lignin-based polymer networks and the potential application of lignin-PDMS polyimines for repairable, translucent, anti-UV, and hydrophobic coatings.
Dissolved Oxygen Redox as the Source of Hydrogen Peroxide and Hydroxyl Radical in Sonicated Emulsive Water Microdroplets
Sonicated emulsive water microdroplets (SEWMs) accelerate and enable a variety of catalyst-free chemical transformations. However, significant unanswered questions remain regarding the chemical intermediates they form and their possible redox origin. In this study, we identified dissolved O 2 as the primary originator of reactive oxygen species (ROS) such as OH• and H 2 O 2. We uncovered the role of dissolved O 2 redox by using a combination of microelectrochemical methods to detect H 2 O 2 , isotopic methods to identify the source of H 2 O 2 , and a combination of electron spin resonance and the DMPO spin trap to detect radicals such as OH•. Notably, we found that H 2 O 2 production is correlated with O 2 content via a reduction pathway enabled by a sufficiently large reducing power that can additionally generate H 2 and even perform Pb electroless deposition on Au and Cu metal substrates. Building on our findings, continuous O 2 bubbling of SEWMs showed accumulation of H 2 O 2 up to ∼88 mM in the aqueous phase within 1 h of sonication, demonstrating the scale-up promise of this method. Distinct to sonochemistry of a single phase, this study advances our understanding of the confluence of redox and chemical reaction mechanisms within SEWMs as a biphasic system. This insight paves the way for improving their reaction kinetics, yield, and selectivity, positioning these attractive redox microreactors as alternatives to traditional electrolyzers.
Selective electrified polyethylene upcycling by pore-modulated pyrolysis
Plastic waste is a increasing problem, accumulating in landfills and the environment. Pyrolysis is a promising and industrially relevant approach for transforming plastic waste into value-added chemicals. However, the selectivity and yield of traditional plastic pyrolysis are poor, with products featuring broad molar mass distributions. Here we report a highly selective, energy-efficient and catalyst-free pyrolysis method that can upcycle plastic into value-added chemicals via pore-modulated pyrolysis. Using a Joule-heated carbon column, we demonstrate the pivotal role of the reactor’s graded porous structure in decreasing the polydispersity of the reaction intermediates, enabling high product selectivity and yield. The decreasing pore size of the reactor modulates the mass transport in an apparent gating effect—preventing high-molar-mass species from exiting the reactor before sufficient pyrolysis has occurred. Using polyethylene as a model reactant, we demonstrate a high yield of 65.9 ± 5.2% and up to 80.8% selectivity toward value-added aviation fuel precursor (C8–C18 hydrocarbons) without the use of any catalysts.
Sustainable upcycling of polyethylene waste to compatibilizers and valuable chemicals
Controllable functionalization of polyethylene (PE) waste could generate new polymeric materials that are generally difficult to manufacture sustainably while also addressing the growing plastics waste problem. However, these modifications remain challenging due to the inherent stability of the PE backbone. Non-thermal atmospheric plasma enables molecular activation under mild conditions while utilizing renewable energy but is primarily employed for surface modification, as plasmas do not penetrate the bulk of materials. Herein, controllable bulk oxidative functionalization of PE wax (PEW) and low-density PE (LDPE) of varying molecular weights was achieved, with up to 6 mol% oxygen incorporation, by manipulating melt viscosity. This functionalization was accomplished either through temperature adjustment or by introducing a melt viscosity modifier, removable via simple extraction methods, to reduce LDPE viscosity, enhance diffusion and chain mobility, and enable bulk oxidation. The oxidized LDPE induces compatibilization in blends of poly(lactic acid) (PLA) and LDPE with improved interfacial adhesion and mechanical properties, such as a 70% increase in elongation-at-break values vs. the control. These findings pave the way for catalyst-free upcycling of direct plastics waste and plastics waste-derived products, enabling the creation of high-value products across various markets.
Electrochemical carbon deposition from CO 2 in molten carbonates: substrate-dependent growth
Electrochemical carbon deposition from molten carbonate salts using inert electrodes and no additional catalyst is systematically examined. At sufficiently cathodic potentials, carbon formation occurs within 30 min and transitions from substrate-dependent nucleation to carbon-on-carbon growth. Although deposits formed on either mild-steel or graphite cathodes exhibit comparable thicknesses and salt contents, their macrostructures differ, reflecting differences in early-stage growth rates and surface chemistry. Characterization by ICP-OES, Raman spectroscopy, SEM/EDS, synchrotron powder X-ray diffraction, and C K-edge X-ray absorption near edge structure reveals that the as-deposited carbon is predominantly disordered sp 2 -bonded material. However, post-treatment reveals latent turbostratic ordering in select samples, indicating that short-range order is established during deposition but is obscured by an entrained electrolyte and kinetically formed amorphous phases. No anode-derived contamination is detected, and carbon grown on graphite cathodes shows minimal metallic impurities. These results clarify the role of cathode surface chemistry and provide pathways for controlling electrode-derived impurity incorporation and carbon structure in catalyst-free molten carbonate systems.
Direct HCN synthesis via plasma-assisted conversion of methane and nitrogen
Hydrogen cyanide (HCN) is synthesized from ammonia (NH 3 ) and methane (CH 4 ) at ~1200°C over a Pt catalyst. Ammonia synthesis entails several complex, highly emitting processes. Plasma-assisted HCN synthesis directly from CH 4 and nitrogen (N 2 ) could be pivotal for on-demand HCN production. Here, we evaluate the potential of dielectric barrier discharge (DBD) N 2 /CH 4 plasma for decentralized catalyst-free selective HCN production. We demonstrate a single-step conversion of methane and nitrogen to HCN with a 72% yield at <300°C. HCN is favored at low CH 4 concentrations with ethane (C 2 H 6 ) as the secondary product. We propose a first-principles microkinetic model with few electron impact reactions. The model accurately predicts primary product yields and elucidates that methyl radical (·CH 3 ) is a common intermediate in HCN and C 2 H 6 synthesis. Compared to current industrial processes, N 2 /CH 4 DBD plasma can achieve minimal CO 2 emissions.