Catalytic Route Research Articles

Cascade Conversion of CO2 to Ethylene Carbonate under Ambient Conditions.

Ethylene carbonate (EC) is the simplest cyclic carbonate with great industrial significance, most importantly as the vital electrolyte component for lithium-ion batteries. Its conventional synthesis generally involves the use of toxic precursors and requires elevated temperatures and pressures. Herein, we propose a cascade catalytic route for converting CO2 to EC under ambient conditions. Such a hybrid reaction scheme consists of the electrochemical reduction of CO2 to ethylene catalyzed by copper in a membrane electrode assembly reactor, the bromine-mediated conversion of ethylene to bromoethanol catalyzed by WO3 nanoarrays grown on carbon cloth, and the reaction between bromoethanol and CO2 to form EC. By separately optimizing individual catalytic steps and then integrating them together in series, we achieved the conversion of CO2 to EC at a good yield under room temperature and atmospheric pressure. Our study also represents the first demonstration about the successful synthesis of organic carbonates from CO2 as the exclusive carbon source.

In situ Generation of Cyclohexanone Drives Electrocatalytic Upgrading of Phenol to Nylon-6 Precursor.

Coupling in situ generated intermediates with other substrates/intermediates is a viable approach for diversifying product outcomes of catalytic reactions involving two or multiple reactants. Cyclohexanone oxime is a key precursor for caprolactam synthesis (the monomer of Nylon-6), yet its current production uses unsustainable carbon sources, noble metal catalysts, and harsh conditions. Herein, we report the first work to synthesize cyclohexanone oxime through electroreduction of phenol and hydroxylamine. The Faradaic efficiency reached 69.1 % over Cu catalyst, accompanied by a corresponding cyclohexanone oxime formation rate of 82.0 g h-1 gcat -1. In addition, the conversion of phenol was up to 97.5 %. In situ characterizations, control experiments, and theoretical calculations suggested the importance of balanced activation of water, phenol, and hydroxylamine substrates on the optimal metallic Cu catalyst for achieving high-performance cyclohexanone oxime synthesis. Besides, a tandem catalytic route for the upgrading of lignin to caprolactam has been successfully developed through the integration of thermal catalysis, electrocatalysis, and Beckmann rearrangement, which achieved the synthesis of 0.40 g of caprolactam from 4.0 g of lignin raw material.

In situ Generation of Cyclohexanone Drives Electrocatalytic Upgrading of Phenol to Nylon‐6 Precursor

AbstractCoupling in situ generated intermediates with other substrates/intermediates is a viable approach for diversifying product outcomes of catalytic reactions involving two or multiple reactants. Cyclohexanone oxime is a key precursor for caprolactam synthesis (the monomer of Nylon‐6), yet its current production uses unsustainable carbon sources, noble metal catalysts, and harsh conditions. Herein, we report the first work to synthesize cyclohexanone oxime through electroreduction of phenol and hydroxylamine. The Faradaic efficiency reached 69.1 % over Cu catalyst, accompanied by a corresponding cyclohexanone oxime formation rate of 82.0 g h−1 gcat−1. In addition, the conversion of phenol was up to 97.5 %. In situ characterizations, control experiments, and theoretical calculations suggested the importance of balanced activation of water, phenol, and hydroxylamine substrates on the optimal metallic Cu catalyst for achieving high‐performance cyclohexanone oxime synthesis. Besides, a tandem catalytic route for the upgrading of lignin to caprolactam has been successfully developed through the integration of thermal catalysis, electrocatalysis, and Beckmann rearrangement, which achieved the synthesis of 0.40 g of caprolactam from 4.0 g of lignin raw material.

Photoredox Oxidation of Alkanes by Monometallic Copper-Oxygen Complexes Using Visible Light Including One Sun Illumination.

Oxygenation of hydrocarbons offers versatile catalytic routes to more valuable compounds, such as alcohols, aldehydes, and ketones. Despite the importance of monometallic copper-oxygen species as hydroxylating agents in biology, few synthetic model compounds are known to react with hydrocarbons, owing to high C-H bond dissociation energies. To overcome this challenge, the photoredox chemistry of monometallic copper (pyrazolyl)borate complexes coordinated by chlorate has been explored in the presence of C1-C6 alkanes with BDEs ≥ 93 kcal/mol. Ethane is photooxidized at room temperature under N2 with yields of 15-30%, which increases to 77% for the most oxidizing tris(3,5-trifluoromethyl-pyrazolyl)borate complex (Cu-3). This complex also promotes the photooxidation of methane to methanol in significant yield (38%) when the photoredox reaction is run under aerobic conditions. Ligand modification alters the reaction selectivity by tuning the redox potential. The ability to activate 1° C-H bonds of C1-C6 alkanes using visible light is consistent with the photogeneration of a powerfully oxidizing copper-oxyl, which is supported by photocrystallographic studies of the tris(3,4,5-tribromopyrazolyl)borate chlorate complex. Mechanistic studies are consistent with the hydrogen atom abstraction of the C-H bond by the copper-oxyl intermediate. We demonstrate for Cu-3 with hexane as an exemplar, that the photoredox chemistry may be achieved under solar conditions of one-sun illumination.

Transformation of CO2 into value-added green hydrocarbon components through a modified catalytic route using biomass-generated graphene-based structures

Transformation of CO2 into value-added green hydrocarbon components through a modified catalytic route using biomass-generated graphene-based structures

Holistic approach for sequential transesterification and pyrolysis of microalgal biomass: Kinetic and thermodynamic analysis of pyrolysis using model-free and model-based approaches

Due to the renewability and sustainability, biofuels derived from algae are considered as competitive substitutes for fossil fuels. Present study investigated a holistic approach for sequential transesterification and pyrolysis of microalgal biomass, i.e. Chlorella minutissima. This study explores the complete utilization of algal biomass through sequential chemical (transesterification) and thermochemical (pyrolysis) processes. First, the lipids were extracted and converted to eco-friendly biodiesel using catalytic route. Then lipid-extracted microalgae were pyrolyzed via thermogravimetric analyzer at four heating rates, namely 5, 10, 20 and 30 °C/min. The model-free isoconversional Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (FWO), and Vyazovkin models were used to analyze the kinetics and thermodynamics of algal pyrolysis. The activation energy obtained for the pyrolysis of Chlorella minutissima utilizing KAS, FWO and Vyazovkin were 146.78, 148.86, 147.11 kJ/mol, respectively. Positive ΔH values from KAS, FWO, and Vyazovkin show an endothermic nature of the process. The mean ΔH was found to be 142.81, 143.97, and 142.82 kJ/mol, while the ΔG was 151.9, 152.20, and 161.40 kJ/mol, respectively for KAS, FWO, and Vyazovkin approaches, at 10 °C/min heating rate. Importantly, this study also revealed that the phase interfacial model was the most appropriate model to represent the degradation process using Coats-Redfern method at 5 oC

Towards Sustainable Production of Polybutylene Adipate Terephthalate: Non-biological Catalytic Syntheses of Biomass-derived Constituents.

Renewable chemicals, which are made from renewable resources such as biomass, have attracted significant interest as substitutes for natural gas- or petroleum-derived chemicals to enhance the sustainability of the chemical and petrochemical industries. Polybutylene adipate terephthalate (PBAT), which is a copolyester of 1,4-butanediol (1,4-BDO), adipic acid (AA), and dimethyl terephthalate (DMT) or terephthalic acid (TPA), has garnered significant interest as a biodegradable polymer. This study assesses the non-biological production of PBAT monomers from biomass feedstocks via heterogeneous catalytic reactions. The biomass-based catalytic routes to each monomer are analyzed and compared to conventional routes. Although no fully commercialized catalytic processes for direct conversion of biomass into 1,4-BDO, AA, DMT, and TPA are available, emerging and promising catalytic routes have been proposed. The proposed biomass-based catalytic pathways toward 1,4-BDO, AA, DMT, and TPA are not yet fully competitive with conventional fossil fuel-based pathways mainly due to high feedstock prices and the existence of other alternatives. However, given continuous technological advances in the renewable production of PBAT monomers, bio-based PBAT should be economically viable in the near future.

Tuning the morphology and textural properties of ZSM-5 additive for co-cracking of waste plastics with vacuum gas oil to light olefins

Typical cracking catalysts, called equilibrium catalyst (E-Cat) are ultra-stable Y (USY) zeolite often used with 15% commercial ZSM-5 zeolite additive (ZSM-5(COM)) to boost olefin yield. In this study, similar additive zeolites with different pore sizes and acidic character were synthesized by rapid ageing of precursor solution and used in the co-cracking of low-density polyethylene (LDPE) and heavy vacuum gas oil (HVGO). Three ZSM-5 zeolites additives with Si/Al ratio 25 (ZSM-5(25)), 50 (ZSM-5(50)) and 75 (ZSM-5(75)) were synthesized and combined with E-Cat to form E-Cat/ZSM-5(25), E-Cat/ZSM-5(50) and E-Cat/ZSM-5(75) respectively. The E-Cat/ZSM-5(50) has slightly better endothermic conversion (cracking) of a mixture of dissolved LDPE and HVGO into H2, C1 to C4 gases and C2-C4 light olefins (total conversion of E-Cat 80.0%, E-Cat/ZSM-5(COM) 75.0% and E-Cat/ZSM-5(50) 83.7% respectively), with different gas, liquid and coke distributions. The E-Cat/ZSM-5(75) has 81% conversion, and highest yield of light olefins (38.4%). Structural (surface area, pore size) and chemical (acid sites) characteristics of the synthetized ZSM-5(75) zeolite explain the observed higher light olefin selectivity by different and competing catalytic routes. The ZSM-5(75) has demonstrated to be a good zeolite additive for converting dissolved plastic in HVGO into light olefins.

A Perspective on Aldoximes as Platform Chemicals: Rethinking C‐N Bond Formation

Primary amines and nitriles play a central role in almost every branch of the chemical industry, and many synthetic strategies exist to obtain them. The major drawbacks of these existing approaches are low selectivities and highly toxic reagents like hydrogen cyanide. This article presents alternative catalytic routes based on aldoximes to address those challenges and outlines what needs to be done to implement aldoximes into a greener amine and nitrile production.

A Comparison of Monoglyceride Production from Microalgaelipids and Rapeseed Oil Catalyzed by Metal Oxides.

This manuscript reports for the first time a heterogenous catalytic route to monoglycerides (MAGs) from microalgal oil. Microalgae is an important biomass source with high-value applications, such as food ingredients with essential fatty acids. To date, the glycerolysis of microalgae has only been investigated for a microbial oil (Schizochytrium sp.) using enzyme catalysis. However, the use of enzymes on a large scale is currently economically impeditive and requires highly selective lipases. In this study, metal oxides were screened and the reaction conditions optimized for rapeseed oil. The optimized conditions were then used to investigate the production of MAGs from Scenedesmus sp. microalga. The most promising catalyst was found to be MgO/KOH, which gave a 44 % yield. Comparing two reaction systems (low temperature 70 °C/atmospheric pressure and high temperature at 200 °C/20 bar), it was found that the latter has a superior performance. Due to the stability of the product in air, the presence of an inert atmosphere is essential to achieve high yields.

Sustainable Aviation Fuel Molecules from (Hemi)Cellulose: Computational Insights into Synthesis Routes, Fuel Properties, and Process Chemistry Metrics.

Production of sustainable aviation fuels (SAFs) can significantly reduce the aviation industry's carbon footprint. Current pathways that produce SAFs in significant volumes from ethanol and fatty acids can be costly, have a relatively high carbon intensity (CI), and impose sustainability challenges. There is a need for a diversified approach to reduce costs and utilize more sustainable feedstocks effectively. Here, we map out catalytic synthesis routes to convert furanics derived from the (hemi)cellulosic biomass to alkanes and cycloalkanes using automated network generation with RING and semiempirical thermochemistry calculations. We find >100 energy-dense C8-C16 alkane and cycloalkane SAF candidates over 300 synthesis routes; the top three are 2-methyl heptane, ethyl cyclohexane, and propyl cyclohexane, although these are relatively short. The shortest, least endothermic process chemistry involves C-C coupling, oxygen removal, and hydrogen addition, with dehydracyclization of the heterocyclic oxygens in the furan ring being the most endothermic step. The global warming potential due to hydrogen use and byproduct CO2 is typically 0.7-1 kg CO2/kg SAF product; the least CO2 emitting routes entail making larger molecules with fewer ketonization, hydrogenation, and hydrodeoxygenation steps. The large number of SAF candidates highlights the rich potential of furanics as a source of SAF molecules. However, the structural dissimilarity between reactants and target products precludes pathways with fewer than six synthetic steps, thus necessitating intensified processes, integrating multiple reaction steps in multifunctional catalytic reactors.

Discovery of molecular ferroelectric catalytic annulation for quinolines

Ferroelectrics as emerging and attractive catalysts have shown tremendous potential for applications including wastewater treatment, hydrogen production, nitrogen fixation, and organic synthesis, etc. In this study, we demonstrate that molecular ferroelectric crystal TMCM-CdCl3 (TMCM = trimethylchloromethylammonium) with multiaxial ferroelectricity and superior piezoelectricity has an effective catalytic activity on the direct construction of the pharmacologically important substituted quinoline derivatives via one-pot [3 + 2 + 1] annulation of anilines and terminal alkynes by using N,N-dimethylformamide (DMF) as the carbon source. The recrystallized TMCM-CdCl3 crystals from DMF remain well ferroelectricity and piezoelectricity. Upon ultrasonic condition, periodic changes in polarization contribute to the release of free charges from the surface of the ferroelectric domains in nano size, which then quickly interacts with the substrates in the solution to trigger the pivotal redox process. Our work advances the molecular ferroelectric crystal as a catalytic route to organic synthesis, not only providing valuable direction for molecular ferroelectrics but also further enriching the executable range of ferroelectric catalysis.

Low-temperature dechlorination of polyvinyl chloride (PVC) for production of H2 and carbon materials using liquid metal catalysts.

Polyvinyl chloride (PVC) is ubiquitous in everyday life; however, it is not recycled because it degrades uncontrollably into toxic products above 250°C. Therefore, it is of interest to controllably dechlorinate PVC at mild temperatures to generate narrowly distributed carbon materials. We present a catalytic route to dechlorinate PVC (~90% reduction of Cl content) at mild temperature (200°C) to produce gas H2 (with negligible coproduction of corrosive gas HCl) and carbon materials using Ga as a liquid metal (LM) catalyst. A LM was used to promote intimate contact between PVC and the catalytic sites. During dechlorination of PVC, Cl is sequestrated in the carbonaceous solid product. Later, chlorine is easily removed with an acetone wash at room temperature. The Ga LM catalyst is reusable, outperforms a traditional supported metal catalyst, and successfully converts (untreated) discarded PVC pipe.

Biodiesel production using various methanol sources and catalytic routes: A techno-environmental analysis

The primary objective of this research is to investigate the biodiesel production via the transesterification reaction between triolein and methanol in the presence of a basic and acidic catalysts, namely sodium hydroxide and sulfuric acid, using CHEMCAD simulation software as a process modelling and simulation tool. Methanol, one of the raw-materials used in biodiesel manufacturing, was synthesized using reforming technology applied to: i) coke oven gas and carbon dioxide, and ii) glycerol that represents an important by-product of the biodiesel synthesis. Four different cases were developed and compared, with detailed operating parameters and equipment designs for each of the investigated scenarios. The production capacity was set to 1000.00 kg/h of biodiesel and a purity higher than 98 % was registered in all investigated cases. Based on the material and energy balances derived from modelling and simulation section, an environmental analysis using the Life Cycle Assessment methodology was performed with the aid of the GaBi software. Ten environmental impact categories (i.e., Global Warming Potential, Fossil Depletion Potential, Human Toxicity, Water Depletion, etc.) are generated and relevant discussions about the sub-processes that exhibit the highest influence are given. The environmental evaluation shows that the most environmentally friendly scenario consists of the methanol production using coke oven gas and carbon dioxide, and its subsequent utilization for the biodiesel production following the alkali catalysis. A scenario analysis regarding several electric and thermal energy sources (i.e., natural gas, biogas, biomass, grid mix) was performed. According to this scenario analysis, while evaluating the synthesis of biodiesel through the alkali catalysis pathway, using biomass as a renewable source improves the environmental performances across certain impact categories.

Discovery of a terpene synthase synthesizing a nearly non-flexible eunicellane reveals the basis of flexibility

Eunicellane diterpenoids, containing a typical 6,10-bicycle, are bioactive compounds widely present in marine corals, but rarely found in bacteria and plants. The intrinsic macrocycle exhibits innate structural flexibility resulting in dynamic conformational changes. However, the mechanisms controlling flexibility remain unknown. The discovery of a terpene synthase, MicA, that is responsible for the biosynthesis of a nearly non-flexible eunicellane skeleton, enable us to propose a feasible theory about the flexibility in eunicellane structures. Parallel studies of all eunicellane synthases in nature discovered to date, including 2Z-geranylgeranyl diphosphate incubations and density functional theory-based Boltzmann population computations, reveale that a trans-fused bicycle with a 2Z-configuration alkene restricts conformational flexibility resulting in a nearly non-flexible eunicellane skeleton. The catalytic route and the enzymatic mechanism of MicA are also elucidated by labeling experiments, density functional theory calculations, structural analysis of the artificial intelligence-based MicA model, and mutational studies.

Advancing Plastic Recycling: A Review on the Synthesis and Applications of Hierarchical Zeolites in Waste Plastic Hydrocracking

The extensive use of plastics has led to a significant environmental threat due to the generation of waste plastic, which has shown significant challenges during recycling. The catalytic hydrocracking route, however, is viewed as a key strategy to manage this fossil-fuel-derived waste into plastic-derived fuels with lower carbon emissions. Despite numerous efforts to identify an effective bi-functional catalyst, especially metal-loaded zeolites, the high-performing zeolite for hydrocracking plastics has yet to be synthesized. This is due to the microporous nature of zeolite, which results in the diffusional limitations of bulkier polymer molecules entering the structure and reducing the overall cracking of plastic and catalyst cycle time. These constraints can be overcome by developing hierarchical zeolites that feature shorter diffusion paths and larger pore sizes, facilitating the movement of bulky polymer molecules. However, if the hierarchical modification process of zeolites is not controlled, it can lead to the synthesis of hierarchical zeolites with compromised functionality or structural integrity, resulting in reduced conversion for the hydrocracking of plastics. Therefore, we provide an overview of various methods for synthesizing hierarchical zeolites, emphasizing significant advancements over the past two decades in developing innovative strategies to introduce additional pore systems. However, the objective of this review is to study the various synthesis approaches based on their effectiveness while developing a clear link between the optimized preparation methods and the structure-activity relationship of the resulting hierarchical zeolites used for the hydrocracking of plastics.

Simulation and conceptual design of an aniline production process from catalytic hydrogenation of nitrobenzene in ChemCAD

Aniline is a very important compound in organic chemistry, mainly used to synthesize polyurethane and its precursors. In the present work, the simulation and conceptual design of an aniline production process through the catalytic hydrogenation route of nitrobenzene was carried out using ChemCADÒ simulator. The simulated aniline production process consisted of a fired heater, a tubular reactor, several heat exchangers, a phase separator, a decanter, as well as two distillation columns. By means of the simulation, the temperatures, pressures, mass flowrates and enthalpies of the main intermediate and final streams were known, as well as the main operating and design parameters of some equipment. About 1,743 kg/h of aniline with a purity of 99.78% are produced at the top stream of the second distillation column, while about 49,881 kg/h of hydrogen are obtained as a by-product in the phase separator. In this work a first-of-its-kind ChemCAD simulation model was obtained in this work, which can be utilized for further optimization studies and tasks involving the increment of aniline purity, yields and productivity.

Ultrathin carbon film as ultrafast rechargeable cathode for hybrid sodium dual-ion capacitor

The development of electrochemical energy storage devices has a decisive impact on clean renewable energy. Herein, novel ultrafast rechargeable hybrid sodium dual-ion capacitors (HSDICs) were designed by using ultrathin carbon film (UCF) as the cathode material. The UCF is synthesized by a simple low temperature catalytic route followed by an acid leaching process. UCF owns a large adsorption interface and number of additional active sites, which is due to the nitrogen doping. In addition, there exists several short-range order carbons on the surface of UCF, which are beneficial for anionic storage. An ultrafast rechargeable remarkable performance, remarkable anion hybrid storage capability and outstanding structure stability is fully tapped employing UCF as cathode for HSDICs. The electrochemical performance of UCF in a half-cell system at the operating voltage between 1.0 and 4.8 V, achieving an admirable specific discharge capacity of 358.52 mAh·g−1 at 500 mA·g−1, and a high capacity retention ratio of 98.42% after cycling 2500 times at 1000 mA·g−1, respectively. Besides, with the support of ex-situ TEM and EDS mapping, the structural stability principle and anionic hybrid storage mechanism of UCF electrode are investigated in depth. In the full-cell system, HSDICs with the UCF as cathode and hard carbon as anode also presents a super-long cycle stability (80.62% capacity retention ratio after cycling 1300 times at 1000 mA·g−1).

Microwave-assisted catalytic gasification of mixed plastics and corn stover for low tar, hydrogen-rich syngas production

The challenge for efficient management of post-consumer plastic and biomass waste has grown over the past few decades due to their dramatic increases. In comparison to conventional gasification, microwave-assisted co-gasification of plastics and corn stover offers many benefits, including increased H2 yield and gas components compared to unfavorable char/tar. Nonetheless, for future commercialization of the process and ease of product separation, further reduction of the undesirable tar is necessary, which can be achieved over the catalytic route. In this work, we studied the catalytic effect of magnetite for microwave-assisted co-gasification of corn stover and plastic to make syngas with higher H2 and lower tar selectivity over non-catalytic conditions. A 1:1:1 ratio of plastic-corn stover-magnetite was used to evaluate the reaction parameters such as temperature, space velocity, heating media, and catalytic cycles under gasification conditions. In comparison with the microwave non-catalytic route, a 100% increase in the total H2 yield with 76% higher H2 production efficiency (mmol/kWh) was achieved in the presence of the magnetite catalyst, while reducing the overall tar formation from 9% to 2%. When magnetite was reduced in situ during the reaction, it coupled with microwave and delivered oxygen radicals that cracked down plastic and corn stover intermediates generated from the synergistic effect under microwave heating. Soon after the oxygen transfer process initiated, magnetite reached its final oxidation state consisting of microwave-active Fe and Fe3C phases that continued coupling with microwaves along with the generated graphitic carbon to maintain the heat necessary to further reduce the generated tar and make additional gaseous products, as confirmed by XRD, Raman, and TGA analyses.

5-Hydroxymethylfurfural and its Downstream Chemicals: A Review of Catalytic Routes.

Biomass assumes an increasingly vital role in the realm of renewable energy and sustainable development due to its abundant availability, renewability, and minimal environmental impact. Within this context, 5-hydroxymethylfurfural (HMF), derived from sugar dehydration, stands out as a critical bio-derived product. It serves as a pivotal multifunctional platform compound, integral in synthesizing various vital chemicals, including furan-based polymers, fine chemicals, and biofuels. The high reactivity of HMF, attributed to its highly active aldehyde, hydroxyl, and furan ring, underscores the challenge of selectively regulating its conversion to obtain the desired products. This review highlights the research progress on efficient catalytic systems for HMF synthesis, oxidation, reduction, and etherification. Additionally, it outlines the techno-economic analysis (TEA) and prospective research directions for the production of furan-based chemicals. Despite significant progress in catalysis research, and certain process routes demonstrating substantial economics, with key indicators surpassing petroleum-based products, a gap persists between fundamental research and large-scale industrialization. This is due to the lack of comprehensive engineering research on bio-based chemicals, making the commercialization process a distant goal. These findings provide valuable insights for further development of this field.