Catalytic Route Research Articles

Enhanced removal of COS from blast furnace gas via catalytic hydrolysis over Al2O3-based catalysts: Insight into the role of alkali metal hydroxide

As blast furnace gas (BFG) can cause air pollution, it is an effective route to convert BFG into a kind of energy. However, it is important to remove carbonyl sulfide (COS) from BFG before burning it. This can be done with catalytic hydrolysis which is considered as a high-efficient technology. In this work, a series of catalysts are prepared via impregnation method to remove COS, in which aluminum oxide (Al2O3) and alkali metal hydroxide (MOH, M = Li, Na and K) are used as base and active component, respectively. Compared with other prepared catalysts, Al2O3 modified with 10% KOH has better catalytic performance in removing COS. The characterization results imply that alkali metal plays a significant role in the enhancement of COS removal efficiency. The capacity of catalysts to adsorb COS is significantly improved with the modification of alkali metal. Moreover, few carbonate or bicarbonate species can be found on the surface of the catalyst during COS hydrolysis. Furthermore, the catalytic mechanism and degradation route of COS hydrolysis on Al2O3 modified with 10% KOH are explored.

Catalytic elemental sulfur-assisted methane activation at low temperature

Methane is the main component of natural gas, and the latter is a clean natural resource with an abundant reserve and wide distribution. Elemental sulfur is both naturally available on the earth and being artificially generated as a recalcitrant solid waste in chemical processes. The co-utilization of elemental sulfur and methane is thus of economic and environmental benefits. Here, a new catalytic route for elemental sulfur-assisted methane activation is demonstrated over metal-loaded zeolite catalysts at a low temperature of 400 °C. Over 10% methane conversion can be achieved even after the catalyst is recycled five times, and the selectivity is well controlled, generating over 90% C2-C4 hydrocarbons as the main products. Control experiments are employed to demonstrate the strategy developed for catalyst design, and a series of verification experiments accompanied by various catalyst characterizations are also performed to elucidate the involved reaction mechanism. The results are further substantiated by theoretical calculations for proposing the possible reaction network. It is suggested that the Langmuir-Hinshelwood surface reaction mechanism might be followed, in which elemental sulfur and methane are both adsorbed over the catalyst surface in a competitive way. When methane activation is triggered and significantly enhanced in the presence of sulfur, both surface reaction and gas-phase reaction can proceed, generating sulfides as complete oxidation products and light hydrocarbons as partial oxidation products, respectively. As a result, the product distribution can be well modulated by the adsorption properties of the charged catalyst. This process provides a transformative cost- and energy-effective way for the co-utilization of two low value-added feedstocks with unique advantages in the natural gas and petroleum industry.

Advances in Catalytic Routes for the Homogeneous Green Conversion of the Bio-Based Platform 5-Hydroxymethylfurfural.

5‐Hydroxymethylfufural (HMF) is an intriguing platform molecule that can be obtained from biomasses and that can lead to the production of a wide range of products, intermediates, or monomers. The presence of different moieties in HMF (hydroxy, aldehyde, furan ring) allows to carry out different transformations such as selective oxidations and hydrogenations, reductive aminations, etherifications, decarbonylations, and acetalizations. This is a great chance in a biorefinery perspective but requires the development of active and highly selective catalysts. In this view, homogeneous catalysis can lead to efficient conversion of HMF at mild reaction conditions. This Review discussed the recent achievements in homogeneous catalysts development and application to HMF transformations. The effects of metal nature, ligands, solvents, and reaction conditions were reported and critically reviewed. Current issues and future chances have been presented to drive future studies toward more efficient and scalable processes.

A Novel Catalytic Route to Polymerizable Bicyclic Cyclic Carbonate Monomers from Carbon Dioxide.

A new catalytic route has been developed for the coupling of epoxides and CO2 affording polymerizable six‐membered bicyclic carbonates. Cyclic epoxides equipped with a β‐positioned OH group can be transformed into structurally diverse bicyclic cyclic carbonates in good yields and with high selectivity. Key to the chemo‐selectivity is the difference between the reactivity of syn‐ and anti‐configured epoxy alcohols, with the latter leading to six‐membered ring carbonate formation in the presence of a binary AlIII aminotriphenolate complex/DIPEA catalyst. X‐ray analyses show that the conversion of the syn‐configured substrate evolves via a standard double inversion pathway providing a five‐membered carbonate product, whereas the anti‐isomer allows for activation of the oxirane unit of the substrate opposite to the pendent alcohol. The potential use of these bicyclic products is shown in ring‐opening polymerization offering access to rigid polycarbonates with improved thermal resistance.

A Novel Catalytic Route to Polymerizable Bicyclic Cyclic Carbonate Monomers from Carbon Dioxide

AbstractA new catalytic route has been developed for the coupling of epoxides and CO2 affording polymerizable six‐membered bicyclic carbonates. Cyclic epoxides equipped with a β‐positioned OH group can be transformed into structurally diverse bicyclic cyclic carbonates in good yields and with high selectivity. Key to the chemo‐selectivity is the difference between the reactivity of syn‐ and anti‐configured epoxy alcohols, with the latter leading to six‐membered ring carbonate formation in the presence of a binary AlIII aminotriphenolate complex/DIPEA catalyst. X‐ray analyses show that the conversion of the syn‐configured substrate evolves via a standard double inversion pathway providing a five‐membered carbonate product, whereas the anti‐isomer allows for activation of the oxirane unit of the substrate opposite to the pendent alcohol. The potential use of these bicyclic products is shown in ring‐opening polymerization offering access to rigid polycarbonates with improved thermal resistance.

Preparation of graphene-supported-metal-phthalocyanine and mechanistic understanding of its catalytic nature at molecular level

The fundamental mechanistic understanding of the working principle of metal phthalocyanine (MPc) + H2O2 system, at molecular level, is in its nascent stage. In this paper, a green strategy was employed for the immobilization of sulfonated cobalt phthalocyanine (CoPc) onto reduced graphene with assistance of bio-synthesized nanocellulose, and the resulting graphene-supported-CoPc (CoPc&G) was applied for the catalytic degradation of phenol solution with H2O2 as oxidant. More than 90% of phenol can be removed within 75 min, and the existence of graphene clearly has a positive effect on the catalytic activity. Theoretical calculations were conducted to unveil the catalytic nature of CoPc&G. H2O2 was favorably chemisorbed onto CoPc&G in the form of OOH−, hydroxyl radicals were favorably formed by homolytic cleavage of OO bonds, and ΔG value for the formation of reactive species was decreased with the existence of graphene. Density of states (DOS) analysis shows that graphene could effectively boost the electronic activity, reduce HOMO-LUMO gap, and strengthen the polarizability of the catalyst, thereby lower the free energy gap for the enhanced generation of reactive species. A detailed catalytic degradation route of phenol with CoPc&G + H2O2 system was established based on the combination of theoretical calculations and experimental results.

Biodiesel Production through Heterogeneous Catalysis Route: A Review

Depletion of oil reserves, increasing prices of petroleum products, and environmental concerns related to air pollution are the main driving forces for utilizing renewable energy resources to replace fossil fuels. Vegetable oils can be used to produce biodiesel. Biodiesel is obtained by transesterification of vegetable oil with alcohol using homogeneous or heterogeneous catalysts. Commercial homogeneous catalysts in the biodiesel production industry are facing challenges such as separation difficulties and severe corrosion which will lead to the increment of production and maintenance cost. Herein, this paper focuses on the comprehensive review of literature reported on the usage of heterogeneous catalyst used in biodiesel production. Compared to other commercial catalysts, the usage of heterogeneous catalyst possesses several advantages such as abundantly available, cheaper raw materials, reusable, non-toxic and biodegradable. Carbon material synthesized from biomass which acts as the efficient support for active sites due to its high porosity and surface area characteristic has been studied widely.

The Critical Role of βPdZn Alloy in Pd/ZnO Catalysts for the Hydrogenation of Carbon Dioxide to Methanol.

The rise in atmospheric CO2 concentration and the concomitant rise in global surface temperature have prompted massive research effort in designing catalytic routes to utilize CO2 as a feedstock. Prime among these is the hydrogenation of CO2 to make methanol, which is a key commodity chemical intermediate, a hydrogen storage molecule, and a possible future fuel for transport sectors that cannot be electrified. Pd/ZnO has been identified as an effective candidate as a catalyst for this reaction, yet there has been no attempt to gain a fundamental understanding of how this catalyst works and more importantly to establish specific design criteria for CO2 hydrogenation catalysts. Here, we show that Pd/ZnO catalysts have the same metal particle composition, irrespective of the different synthesis procedures and types of ZnO used here. We demonstrate that all of these Pd/ZnO catalysts exhibit the same activity trend. In all cases, the β-PdZn 1:1 alloy is produced and dictates the catalysis. This conclusion is further supported by the relationship between conversion and selectivity and their small variation with ZnO surface area in the range 6–80 m2g–1. Without alloying with Zn, Pd is a reverse water-gas shift catalyst and when supported on alumina and silica is much less active for CO2 conversion to methanol than on ZnO. Our approach is applicable to the discovery and design of improved catalysts for CO2 hydrogenation and will aid future catalyst discovery.

Catalytic Routes to Produce Polyphenolic Esters (PEs) from Biomass Feedstocks

Polyphenolic esters (PEs) are valuable chemical compounds that display a wide spectrum of activities (e.g., anti-oxidative effects). As a result, their production through catalytic routes is an attractive field of research. The present review aims to discuss recent studies from the literature regarding the catalytic production of PEs from biomass feedstocks, namely, naturally occurred polyphenolic compounds. Several synthetic approaches are reported in the literature, mainly bio-catalysis and to a lesser extent acid catalysis. Immobilized lipases (e.g., Novozym 435) are the preferred enzymes thanks to their high reactivity, selectivity and reusability. Acid catalysis is principally investigated for the esterification of polyphenolic acids with fatty alcohols and/or glycerol, using both homogeneous (p-toluensulfonic acid, sulfonic acid and ionic liquids) and heterogeneous (strongly acidic cation exchange resins) catalysts. Based on the reviewed publications, we propose some suggestions to improve the synthesis of PEs with the aim of increasing the greenness of the overall production process. In fact, much more attention should be paid to the use of new and efficient acid catalysts and their reuse for multiple reaction cycles.

Photothermal catalysis for CO2 conversion

The conversion of carbon dioxide into useful fuels or chemical feedstocks is of great importance for achieving carbon emission peak and carbon neutrality. The harvesting and conversion of solar energy will provide a sustainable and environmentally friendly energy source for human production and living. Very recently, photothermal catalysis has been proved to exhibit great advantages in reducing the reaction temperature, promoting the catalytic activity, and manipulating the reaction pathway in comparison with traditional thermal catalysis. In this review, we firstly introduced the fundamental mechanisms and categories of photothermal catalysis to understand the synergy or the difference between photochemical and thermochemical reaction pathways. Subsequently, the criteria and strategies for photothermal catalyst design are discussed in order to inspire the development of high-efficiency photothermal catalytic route by achieving intense absorption of broadband solar energy spectrum and high conversion capability of solar-to-heat. Recent progress in CO2 reduction achieved by photothermal catalysis was summarized in terms of production types. In the end, the future challenges and perspectives of photothermal catalytic CO2 reduction are presented. We hope that this review will not only deepen the understanding of photothermal catalysis, but also inspire the design, preparation and application of high-performance photothermal catalysts, aiming at alleviating non-renewable fossil energy consumption and carbon emissions for early carbon emission peak and carbon neutrality.

NbOx-Based Catalysts for the Activation of C-O and C-C Bonds in the Valorization of Waste Carbon Resources.

Escalating energy demand, the depletion of fossil fuels, and abnormal climate change are recognized as the key challenges in the 21st century. The valorization of biomass and plastic, representing the most abundant natural and man-made polymers, respectively, as alternatives to fossil fuel is one of the promising solutions to creating a carbon-neutral, waste-free society. Catalysis is an essential tool for manipulating energy transformations via bond-breaking and bond-forming principles. To producing chemicals and fuels via biomass valorization and plastic upcycling, the cleavage of C-O and C-C bonds is the major catalytic route, given that the two are mainly constructed by various interunit C-O and C-C linkages. In this work, a consensus concerning the catalytic mechanism is reached: the activities for the cleavage of C-O and C-C bonds highly depend on the catalyst ability to activate the C-O and C-C bonds. Among the catalysts reported, NbOx-based catalysts show a unique, superstrong ability to activate C-O and C-C bonds. While research on biomass valorization over NbOx-based catalysts maintains its momentum, plastic upcycling driven by an efficient NbOx-based catalyst capable of activating C-O and C-C bonds is quickly catching up. Therefore, deepening the understanding of NbOx-based catalysts for the activation of C-O and C-C bonds is of importance to further drive biomass valorization and plastic upcycling, even in many other related areas. Herein, we present progress on the activation of C-O and C-C bonds in waste carbon resources, with an emphasis on our own work in using NbOx-based catalysts. First, we introduce NbOx-based catalysts for the activation of C-O and C-C bonds in biomass with a special focus on explaining how NbOx-based catalysts activate C-O and C-C bonds and why NbOx-based catalysts can activate C-O and C-C bonds so efficiently. Then, unified descriptors to embody the abilities to extract O from oxygenated compounds and an adsorbed benzene ring, namely "oxygen affinity" and "benzene ring affinity", were defined to standardize C-O and Carom-Caliph activation chemistry. Furthermore, we highlight the emerging opportunities of NbOx-based catalysts for plastic upcycling by learning the wisdom accumulated from the activation of C-O and C-C bonds in biomass. Finally, our own insights into future recommendations in this promising field are provided.

Recent Advances in Transition Metal Catalyzed Synthesis of β‐Enaminones and β‐Enaminoesters

Abstractβ‐Enaminones and β‐enaminoesters are reactive and versatile building blocks in organic synthesis. The favorable structure of electron‐withdrawing carbonyl group or ester group and electron‐donating amino groups are respectively linked at both termini of a C=C double bond. In recent years, transition metal catalyzed synthesis of β‐enaminones and β‐enaminoesters have been widely explored and continuously reported. Thus, herein we intended to review the progress in transition metal catalytic routes to these useful synthetic intermediates, with a sequence of condensation of amines with β‐dicarbonyl compounds, aldol‐type addition of ketones to nitriles, N−H olefination of amines and sulfonamides, amination of propargyl alcohols and ynones, multi‐component reactions, and other reactions.

Diformylphloroglucinol derived imine based covalent organic frameworks (PHTA) as efficient organocatalyst for conversion of isocyanates to urea derivatives

New two-dimensional porous covalent organic frameworks (PHTA) with imine linkers have been synthesized and effectively utilized as metal free catalytic system for the synthesis of urea derivatives from a wide range of isocyanates under inert atmosphere. The material has been thoroughly characterized using powder XRD, HRTEM, FESEM, BET, FT-IR, XPS and a structure-activity relationship has been established. The imine based covalent organic framework owing to its highly conjugated system permits superior conduction efficiency of carriers, thereby exhibiting better performance and exceptional reusability and selectivity (> 99%) towards generation of urea derivatives from the corresponding isocyanates. At room temperature the solvent free catalytic process under nitrogen atmosphere requires short range of reaction duration (2 h) to produce high yields (84–96%) of ureaderivatives from respective isocyanates. The catalytic route of urea synthesis in presence of organocatalyst PHTA is suitably described by theoretical calculations (DFT) method. The heterogeneity and recyclability nature of the catalyst is checked for five cycles and the obtained result portrayed its good catalytic effectiveness.

Hierarchical Cu-Mn/ZSM-5 with boosted activity and selectivity for n-butylamine destruction: Synergy of pore structure and surface acidity

Adjusting the catalytic degradation route of nitrogen-containing VOCs (NVOCs) is still a challenge as both the oxidation and reduction reactions are simultaneously involved. Herein, a series of hierarchical Cu-Mn/ZSM-5 materials with different pore structures and surface acidities were prepared via an impregnation method and adopted for catalytic n-butylamine destruction. Experimental results show that the CuMn/Z-2 sample has the highest activity and N2 selectivity, over which n-butylamine can be totally decomposed at 280 °C with N2 selectivity over 82%. The superior catalytic performance of CuMn/Z-2 is owing to its developed porosity (accelerating the oxidation process and inhibiting organic byproducts formation) and weak acidity (slight adsorption of NH3 and preventing the formation of N2O). In situ DRIFTS reveal that the catalytic destruction of n-butylamine over Cu-Mn/ZSM-5 obeys two parallel pathways of n-butylamine adsorbed on acidic sites with C-N cleavage and n-butylamine adsorbed on metal sites and oxidized to amide before alcohol.

Complex Nanomaterials in Catalysis for Chemically Significant Applications: From Synthesis and Hydrocarbon Processing to Renewable Energy Applications

The world is rapidly changing, the resources are getting depleted, and the demand for newer technologies and products is increasing. To keep up with these new advances, highly efficient catalytic routes need to be taken to be sustainable and ensure a drawn-out existence of resources for future generations. Catalysis turns out to be a significantly important field of application when it comes to the era of nanoscience, where all devices and technologies are becoming smaller and smaller in size with improved properties. When deeming the usability of a catalyst, it is of paramount importance to have a good understanding of their properties and their synergistic effect on the other reagents in the reaction. Over the last decade, the field of nanocatalysis has grown rapidly, both in homogeneous and heterogeneous catalysis. Given that nanoparticles have a high surface-to-volume ratio when compared to bulk materials, they are appealing as catalysts. Catalysts accelerate and boost thousands of different chemical reactions on a daily basis, forming the foundation of the multibillion-dollar chemical industry worldwide, a pathway leading to green chemistry, and a novel, yet crucial, environmental protection technology. As a result, in this review, the use of nanocatalysts and the application of their special features in the renewable energy, hydrocarbon processing, and fine chemical synthesis sector was explored. A detailed explanation of the working mechanism of these nanocatalysts, starting from how they are synthesized to the effect of modification of their surface, has been put together. We have tried to collect all the current progresses in these three sectors to the best of our abilities. Furthermore, it is anticipated that this paper would be useful for future researchers and academicians wishing to contribute toward this subject of interest.

Hydrolysis of dimethyl terephthalate to terephthalic acid on Nb‐modified HZSM‐5 zeolite catalysts

AbstractBACKGROUNDWhether waste polyethylene terephthalate (PET) can be effectively recycled is one of the main challenges of the current environmental problems. The hydrolysis of dimethyl terephthalate (DMT) to terephthalic acid (TPA) over Nb‐modified HZSM‐5 zeolite was studied. Nb/HZSM‐5 zeolites with different loadings were prepared and characterized by X‐ray diffraction, X‐ray photoelectron spectroscopy, scanning electron microscopy, NH3‐temperature programmed desorption and pyridine adsorption infrared spectroscopy. The effects of different reaction conditions on the conversion of DMT and TPA yield were investigated.RESULTSThe yield of TPA strongly depends on the reaction conditions and the loading of Nb. The niobium phase exists in the form of Nb2O5 on the zeolite and interacts with the surface of HZSM‐5 to produce the active site of Brønsted acid. The yield of TPA is closely related to the concentration of Brønsted acid sites. On 0.6Nb/HZSM‐5 catalyst, the yield of TPA is highest, at about 94%.CONCLUSIONNb/HZSM‐5 catalyst has excellent catalytic activity and high stability for DMT hydrolysis. In addition, the product TPA prepared in this study can be directly applied to the current PET production supply chain, providing a promising catalytic route. © 2022 Society of Chemical Industry (SCI).

Lignin‐First Monomers to Catechol: Rational Cleavage of C−O and C−C Bonds over Zeolites

A catalytic route is developed to synthesize bio-renewable catechol from softwood-derived lignin-first monomers. This process concept consists of two steps: 1) O-demethylation of 4-n-propylguaiacol (4-PG) over acidic beta zeolites in hot pressurized liquid water delivering 4-n-propylcatechol (4-PC); 2) gas-phase C-dealkylation of 4-PC providing catechol and propylene over acidic ZSM-5 zeolites in the presence of water. With large pore sized beta-19 zeolite as catalyst, 4-PC is formed with more than 93 % selectivity at nearly full conversion of 4-PG. The acid-catalyzed C-dealkylation over ZSM-5 zeolite with medium pore size gives a catechol yield of 75 %. Overall, around 70 % catechol yield is obtained from pure 4-PG, or 56 % when starting from crude 4-PG monomers obtained from softwood by lignin-first RCF biorefinery. The selective cleavage of functional groups from biobased platform molecules through a green and sustainable process highlights the potential to shift feedstock from fossil oil to biomass, providing drop ins for the chemicals industry.

Photoreforming of plastic waste poly (ethylene terephthalate) via in-situ derived CN-CNTs-NiMo hybrids

Photoreforming of plastic waste is a novel approach, which can not only degrade plastic waste into valuable chemicals, but also produce high-energy-density hydrogen fuels. Here, we developed an in-situ derived carbon nitride-carbon nanotubes-NiMo hybrids via NiMo-assisted catalysis route, which works as an efficient and stable photocatalyst for plastics photoreforming. The strong π-π interaction between in-situ derived CNTs and CN promotes electron transfer, increases carrier lifetime and improves photocatalytic activity. The DFT calculations and single-particle PL quenching phenomenon confirmed the strong interface effect and charge transport for CN-CNTs-NM. In addition, the strong interaction between photocatalyst and ethylene glycol in plastics was observed in situ by single-particle PL. This work provides a smart strategy of utilizing in-situ derived π-π interaction as well as direct evidence of the charge transfer from the photocatalysts to ethylene glycol, which provides guidance for the rational design of highly efficient photocatalysts for plastics photoreforming.

Decrypting Catalytic NOX Activation and Poison Fragmentation Routes Boosted by Mono- and Bi-Dentate Surface SO32–/SO42– Modifiers under a SO2-Containing Flue Gas Stream

Decrypting Catalytic NO_<i>X</i> Activation and Poison Fragmentation Routes Boosted by <i>Mono</i>- and <i>Bi</i>-Dentate Surface SO₃^2–/SO₄^2– Modifiers under a SO₂-Containing Flue Gas Stream

Suitably Band-aligned MOF-Derived Ni2 P/MnO2 Heterostructure with Ni(I) Coordination Surface Sites for Self-Coupling of Aryl Halides to Biaryls.

An efficient photo-redox strategy for the aryl-aryl self-coupling of aryl halides through a heterogeneous catalysis route has been demonstrated. A coordinatively unsaturated Ni2 P surface with the enhanced photochemical property upon hetero-structuring with δ-MnO2 affects the organic transformation to biaryls with impressive yield and photo-conversion efficiency. The dual-role of the Ni2 P catalyst with its participation as the catalytic active surface and the photo-redox center distinguishes the organic transformation achieved herein with other catalytic and photocatalytic aryl-aryl self-coupling.