Quantitative production of butenes from biomass-derived γ-valerolactone catalysed by hetero-atomic MFI zeolite

Tailoring the Brønsted acidity of Ti-OH species by regulating Pt-TiO2 interaction

Bifunctional catalysts comprising metal and acid sites are commonly used for many reactions. Interfacial acid sites impact intermediate reactions more than other sites. However, controlling the type and amounts of interfacial acid sites by regulating metal-support interaction (MSI) via traditional methods is difficult. Thus, the influence of MSI on interfacial acid sites remains unclear. We prepared Pt-mTiO2/α-Al2O3 (m represents the cycle number of TiO2) catalysts via atomic layer deposition (ALD). New Brønsted acid sites were generated via Pt-TiO2 interaction, and the acidity was precisely regulated by regulating Pt-TiO2 interaction by changing the TiO2 nanolayer thickness. We chose levulinic acid (LA) hydrogenation as a model reaction. The catalytic activity varied with the TiO2 nanolayer thickness and was linearly correlated with the Ti-OH species (Brønsted acid) content. Pt-40TiO2/α-Al2O3, with the highest acid site content of 0.486 mmol/g, exhibited the best catalytic activity. Hydrogen spillover and water dissociation at the Pt-TiO2 interface promoted Ti-OH species generation.

Sniffing Out the Sustainable Future: The Renewability Revolution in Fragrance Chemistry

In this review, the impact of the transition from today's resource-wasting petrochemical economy towards a 100/100 renewable and biodegradable future is discussed with respect to the fragrance families: "citrus", "green", "fruity", "floral", "floriental", "oriental", "woody", "chypre" and "fougère". After benchmark data on ingredients usage, definitions on biodegradation and sustainability are given. Celebrating the 150th anniversary of synthetic vanillin, its historic synthesis from renewable starting materials serves as introduction. In the grand scheme of things, citrus scents upcycled from the beverages industry, are already an ideal case for 100/100 with new opportunities for artificial essential oils. In the fruity domain, transparent and lactonic ingredients are available in a sustainable manner. However, in the domain of green odorants, there is a lack of green chemistry for important key materials. In the floral family, renewability is more critical than biodegradability, but cost is an issue. Thanks to Ambrox and maltol, florientals and orientals will persist, while woody notes severely lack an Iso E Super replacer. In the chypre genre, patchouli became the new moss, but more musks are increasingly in demand. With their high percentage of linalool and dihydromyrcenol, the construction of fougères could well become a precedent for other families, despite challenges in vetiver and salicylates. Still, the challenges exemplified here create immense opportunities for new perfumery materials.

Photocatalytic Dehalogenative Deuteration of Halides over a Robust Metal-Organic Framework

Deuterium labelling of organic compounds is an important process in chemistry. We report the first example of photocatalytic dehalogenative deuteration of both arylhalides and alkylhalides (40 substrates) over a metal-organic framework, MFM-300(Cr), using CD3 CN as the deuterium source at room temperature. MFM-300(Cr) catalyses high deuterium incorporation and shows excellent tolerance to various functional groups. Synchrotron X-ray powder diffraction reveals the activation of halogenated substrates via confined binding within MFM-300(Cr). In situ electron paramagnetic resonance spectroscopy confirms the formation of carbon-based radicals as intermediates and reveals the reaction pathway. This protocol removes the use of precious-metal catalysts from state-of-the-art processes based upon direct hydrogen isotope exchange and shows high photocatalytic stability, thus enabling multiple catalytic cycles.

Synthetic Control of the Defect Structure and Hierarchical Extra-Large-/Small-Pore Microporosity in Aluminosilicate Zeolite SWY

The SWY-type aluminosilicate zeolite, STA-30, has been synthesized via different routes to understand its defect chemistry and solid acidity. The synthetic parameters varied were the gel aging, the Al source, and the organic structure directing agent. All syntheses give crystalline materials with similar Si/Al ratios (6-7) that are stable in the activated K,H-form and closely similar by powder X-ray diffraction. However, they exhibit major differences in the crystal morphology and in their intracrystalline porosity and silanol concentrations. The diDABCO-C82+ (1,1'-(octane-1,8-diyl)bis(1,4-diazabicyclo[2.2.2]octan)-1-ium)-templated STA-30 samples (but not those templated by bisquinuclidinium octane, diQuin-C82+) possess hierarchical microporosity, consisting of noncrystallographic extra-large micropores (13 Å) that connect with the characteristic swy and gme cages of the SWY structure. This results in pore volumes up to 30% greater than those measured in activated diQuin-C8_STA-30 as well as higher concentrations of silanols and fewer Brønsted acid sites (BASs). The hierarchical porosity is demonstrated by isopentane adsorption and the FTIR of adsorbed pyridine, which shows that up to 77% of the BASs are accessible (remarkable for a zeolite that has a small-pore crystal structure). A structural model of single can/d6r column vacancies is proposed for the extra-large micropores, which is revealed unambiguously by high-resolution scanning transmission electron microscopy. STA-30 can therefore be prepared as a hierarchically porous zeolite via direct synthesis. The additional noncrystallographic porosity and, subsequently, the amount of SiOHs in the zeolites can be enhanced or strongly reduced by the choice of crystallization conditions.

Efficient Conversion of Lignin to Aromatics via Catalytic Fast Pyrolysis over Niobium-Doped HZSM-5

A niobium-doped HZSM-5 (H[Nb]ZSM-5) was prepared by a hydrothermal synthesis method. The morphology, phase structure, composition, pore structure, and acid content of the catalyst were characterized using a series of analysis techniques such as scanning electron microscope (SEM), energy-dispersive X-ray (EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption-desorption, and temperature programmed desorption measurements (NH₃-TPD). The H[Nb]ZSM-5 catalyst fully remained within the crystal framework and pore structure of HZSM-5. Meanwhile, introduction of niobium (V) endowed the catalyst with both Lewis acid and Bronsted acid sites. Catalytic fast pyrolysis (CFP) of alkali lignin was carried out through a pyrolysis and gas chromatography-mass spectrometry (Py-GC/MS) at 650 °C and atmospheric pressure. The results indicated that H[Nb]ZSM-5 can efficiently and selectively convert lignin into monoaromatic hydrocarbons (MAHs), compared to the control HZSM-5. Catalyzed by H[Nb]ZSM-5, the content of MAHs and aliphatic hydrocarbons reached 43.4% and 20.8%, respectively; while under the catalysis of HZSM-5, these values were 35.5% and 3.2%, respectively. H[Nb]ZSM-5 remarkably lowered the phenol content to approximately 2.8%, which is far lower than the content (24.9%) obtained under HZSM-5 catalysis.

Nature-inspired methylated polyhydroxybutyrates from C1 and C4 feedstocks

Polyolefin plastics are widely used due to their low cost and outstanding properties, but their environmental persistence presents a major societal challenge. Polyhydroxyalkanoates (PHA) are biodegradable substitutes for polyolefins, but their high cost and thermal instability are impediments to their widespread application. Here we report a series of methylated polyhydroxybutyrates, poly(3-hydroxy-2-methylbutyrate)s, which are structurally inspired by natural PHAs. The cis homopolymers exhibit tacticity-independent crystallinity, which allows for the discovery of high-melting, thermally stable and mechanically tough copolymers, and a full range of polyolefin-like properties can be further achieved by tailoring the cis/trans ratio of the repeating units. Moreover, these materials can be synthesized from inexpensive carbon monoxide and 2-butene feedstocks, and they can be chemically recycled or upcycled at their end of life. The versatile properties, abundant feedstocks and end-of-life utility of this family of polyesters will enable a powerful platform for the discovery of sustainable alternatives to polyolefin plastics.

Converting Non-strained γ-Valerolactone and Derivatives into Sustainable Polythioesters via Isomerization-driven Cationic Ring-Opening Polymerization of Thionolactone Intermediate

This contribution reports the efficient conversion of γ-valerolactone and its derivatives, abundant but unexplored renewable feedstocks, into sustainable and degradable polythioesters via the establishment of the first isomerization-driven ring-opening polymerizations (IROPs) of corresponding thionolactone intermediates. The key to this success relies on the development of a new simple and robust [Et₃ O]⁺ [B(C₆ F₅ )₄ ]^- cationic initiator which possesses high activity, exclusive selectivity, living nature, and broad scope of thionolactones. A complete inversion of configuration during IROP of enantiopure γ-thionovalerolactone is also disclosed, affording isotactic semicrystalline polythioesters (T_m =87.0 °C) with mechanical property compared well to the representative commodity polyolefins. The formation of a highly crystalline supramolecular stereocomplex with enhanced thermal property (T_m =117.6 °C) has also been revealed.

Sustainable product-based approach in the production of olefins using a dual functional ZSM-5 catalyst

Investigation of the current industrial processes, such as methanol to olefin (MTO) and hexane to olefin (HTO), in terms of green and sustainable chemistry approaches in order to design the process, catalyst and reactor from the beginning in such a way as to minimize environmental pollution is compulsory. Therefore, the synthesis of a group of multifunctional catalysts, which can be used simultaneously in both industrial processes to produce a variety of products, was studied. The effect of incorporation of different metals (Fe, Mn, Zn, Ga and Al) on the strengthening of each of the products was also studied. The investigation of reactor productivity (WHSV_HTO = 25) in HTO showed that the production efficiency of propylene in microchannels is higher than the ideal value for all samples, which is a significant improvement for sustainable approaches in future technologies. Considering the overall performances, Ga-ZM showed the best performance in both processes due to the high P/E ratio. The significant effect of Ga on the increasing of propylene was confirmed in MTO at 400 °C (P/E ≃ ∞), which indicated the dramatic effect of this metal in directing the reaction mechanism to an olefin-based cycle by converting almost all ethylene to propylene by methylation.

Bimetallic Aluminum- and Niobium-Doped MCM-41 for Efficient Conversion of Biomass-Derived 2-Methyltetrahydrofuran to Pentadienes

The production of conjugated C4-C5 dienes from biomass can enable the sustainable synthesis of many important polymers and liquid fuels. Here, we report the first example of bimetallic (Nb, Al)-atomically doped mesoporous silica, denoted as AlNb-MCM-41, which affords quantitative conversion of 2-methyltetrahydrofuran (2-MTHF) to pentadienes with a high selectivity of 91 %. The incorporation of Al^III and Nb^V sites into the framework of AlNb-MCM-41 has effectively tuned the nature and distribution of Lewis and Brønsted acid sites within the structure. Operando X-ray absorption, diffuse reflectance infrared and solid-state NMR spectroscopy collectively reveal the molecular mechanism of the conversion of adsorbed 2-MTHF over AlNb-MCM-41. Specifically, the atomically-dispersed Nb^V sites play an important role in binding 2-MTHF to drive the conversion. Overall, this study highlights the potential of hetero-atomic mesoporous solids for the manufacture of renewable materials.

Bimetallic Aluminum- and Niobium-Doped MCM-41 for Efficient Conversion of Biomass-Derived 2-Methyltetrahydrofuran to Pentadienes

The production of conjugated C4-C5 dienes from biomass can enable the sustainable synthesis of many important polymers and liquid fuels. Here, we report the first example of bimetallic (Nb, Al)-atomically doped mesoporous silica, denoted as AlNb-MCM-41, which affords quantitative conversion of 2-methyltetrahydrofuran (2-MTHF) to pentadienes with a high selectivity of 91 %. The incorporation of AlIII and NbV sites into the framework of AlNb-MCM-41 has effectively tuned the nature and distribution of Lewis and Brønsted acid sites within the structure. Operando X-ray absorption, diffuse reflectance infrared and solid-state NMR spectroscopy collectively reveal the molecular mechanism of the conversion of adsorbed 2-MTHF over AlNb-MCM-41. Specifically, the atomically-dispersed NbV sites play an important role in binding 2-MTHF to drive the conversion. Overall, this study highlights the potential of hetero-atomic mesoporous solids for the manufacture of renewable materials.

Metal Sites in Zeolites: Synthesis, Characterization, and Catalysis

Zeolites with ordered microporous systems, distinct framework topologies, good spatial nanoconfinement effects, and superior (hydro)thermal stability are an ideal scaffold for planting diverse active metal species, including single sites, clusters, and nanoparticles in the framework and framework-associated sites and extra-framework positions, thus affording the metal-in-zeolite catalysts outstanding activity, unique shape selectivity, and enhanced stability and recyclability in the processes of Brønsted acid-, Lewis acid-, and extra-framework metal-catalyzed reactions. Especially, thanks to the advances in zeolite synthesis and characterization techniques in recent years, zeolite-confined extra-framework metal catalysts (denoted as metal@zeolite composites) have experienced rapid development in heterogeneous catalysis, owing to the combination of the merits of both active metal sites and zeolite intrinsic properties. In this review, we will present the recent developments of synthesis strategies for incorporating and tailoring of active metal sites in zeolites and advanced characterization techniques for identification of the location, distribution, and coordination environment of metal species in zeolites. Furthermore, the catalytic applications of metal-in-zeolite catalysts are demonstrated, with an emphasis on the metal@zeolite composites in hydrogenation, dehydrogenation, and oxidation reactions. Finally, we point out the current challenges and future perspectives on precise synthesis, atomic level identification, and practical application of the metal-in-zeolite catalyst system.

Defect-Guided Synthesis of Hierarchical Sn-B-Beta Zeolite with Highly Exposed Sn Sites

Selectively anchoring active centers on the external surface for forming highly exposed acid sites is a highly desirable but challenging task in zeolite catalyst synthesis. Herein, a defect-guided etching-regrowth strategy is rationally designed for facilely positioning Sn Lewis acid sites on the outer surface of the Sn-B-Beta while fabricating a bifunctional hierarchical structure. The synthesis was conducted by hydrothermal treatment of the as-made B-Beta (uncalcined), which has intrinsic defects of the BEA structure, with Sn source and basic organic structure directing agent (SDA). Under a moderate SDA concentration, with blocked micropore channels, such SDA-triggered etching-regrowth will proceed along the defect defined pathway, which ensures Sn selectively anchored on the external surface. Moreover, this methodology has exclusively introduced tetrahedrally coordinated framework Sn with open Sn sites as the predominated species. Mono- and disaccharide isomerizations in ethanol over different Sn-Beta catalysts proved the prominent advantages of the hierarchical structure with highly exposed and synergetic acid sites.

Amberlyst-15 supported zirconium sulfonate as an efficient catalyst for Meerwein-Ponndorf-Verley reductions

The Meerwein-Ponndorf-Verley (MPV) reaction is an important chemoselective route for carbonyl group hydrogenation, and thus designing new and effective catalysts for this transformation remains important and challenging. In this work, a new sulfonate coordinated Zr(IV) catalyst was prepared by the coordination of Zr(IV) onto the sulfonate groups of Amberlyst-15, which can effectively catalyze the MPV reaction and quantitatively convert carbonyl compounds to the corresponding alcohols with high reactivity and stability. Detailed mechanistic investigations reveal that the catalytic performance of Zr-AIER can be attributed to the synergetic effect between Zr⁴⁺ and the sulfonate group, and the porous structure with high surface area.

Emerging Analytical Methods to Characterize Zeolite-Based Materials

Zeolites and zeolitic materials are, through their use in numerous conventional and sustainable applications, very important to our daily lives, including to foster the necessary transition to a more circular society. The characterization of zeolite-based materials has a tremendous history and a great number of applications and properties of these materials have been discovered in the past decades. This review focuses on recently developed novel as well as more conventional techniques applied with the aim of better understanding zeolite-based materials. Recently explored analytical methods, e.g. atom probe tomography, scanning transmission X-ray microscopy, confocal fluorescence microscopy and photo-induced force microscopy, are discussed on their important contributions to the better understanding of zeolites as they mainly focus on the micro- to nanoscale chemical imaging and the revelation of structure–composition–performance relationships. Some other techniques have a long and established history, e.g. nuclear magnetic resonance, infrared, neutron scattering, electron microscopy and X-ray diffraction techniques, and have gone through increasing developments allowing the techniques to discover new and important features in zeolite-based materials. Additional to the increasing application of these methods, multiple techniques are nowadays used to study zeolites under working conditions (i.e. the in situ/operando mode of analysis) providing new insights in reaction and deactivation mechanisms.

Combined spectroscopic and computational study for optimising catalyst design in hydrocarbon transformations

Molecular interactions of hydrocarbons within the confined pores of heterogeneous catalysts can influence reaction pathways, which play a crucial role in determining the overall efficacy of catalytic transformations. We probe...

Unravelling the one-pot conversion of biomass-derived furfural and levulinic acid to 1,4-pentanediol catalysed by supported RANEY® Ni-Sn alloy catalysts

Bimetallic Ni–Sn alloys have been recognised as promising catalysts for the transformation of furanic compounds and their derivatives into valuable chemicals. Herein, we report the utilisation of a supported bimetallic RANEY® nickel–tin alloy supported on aluminium hydroxide (RNi–Sn(x)/AlOH; x is Ni/Sn molar ratio) catalysts for the one-pot conversion of biomass-derived furfural and levulinic acid to 1,4-pentanediol (1,4-PeD). The as prepared RNi–Sn(1.4)/AlOH catalyst exhibited the highest yield of 1,4-PeD (78%). The reduction of RNi–Sn(x)/AlOH with H₂ at 673–873 K for 1.5 h resulted in the formation of Ni–Sn alloy phases (e.g., Ni₃Sn and Ni₃Sn₂) and caused the transformation of aluminium hydroxide (AlOH) to amorphous alumina (AA). The RNi–Sn(1.4)/AA 673 K/H₂ catalyst contained a Ni₃Sn₂ alloy as the major phase, which exhibited the best yield of 1,4-PeD from furfural (87%) at 433 K, H₂ 3.0 MPa for 12 h and from levulinic acid (up to 90%) at 503 K, H₂ 4.0 MPa, for 12 h. Supported RANEY® Ni–Sn(1.5)/AC and three types of supported Ni–Sn(1.5) alloy (e.g., Ni–Sn(1.5)/AC, Ni–Sn(1.5)/c-AlOH, and Ni–Sn(1.5)/γ-Al₂O₃) catalysts afforded high yields of 1,4-PeD (65–87%) both from furfural and levulinic acid under the optimised reaction conditions.

The RANEY® Ni–Sn(x) alloy catalysed the one-pot conversion of biomass-derived furfural and levulinic acid to allow remarkable yield of 1,4-pentanediol (up to 90%) under the mild reaction conditions.

Green Carbon Science: Efficient Carbon Resource Processing, Utilization, and Recycling Towards Carbon Neutrality

Green carbon science is defined as "Study and optimization of the transformation of carbon containing compounds and the relevant processes involved in the entire carbon cycle from carbon resource processing, carbon energy utilization, and carbon recycling to use carbon resources efficiently and minimize the net CO2 emission." [1] Green carbon science is related closely to carbon neutrality, and the relevant fields have developed quickly in the last decade. In this Minireview, we proposed the concept of carbon energy index, and the recent progresses in petroleum refining, production of liquid fuels, chemicals, and materials using coal, methane, CO2, biomass, and waste plastics are highlighted in combination with green carbon science, and an outlook for these important fields is provided in the final section.

Emerging heterogeneous catalysts for biomass conversion: studies of the reaction mechanism

The development of efficient catalysts to break down and convert woody biomass will be a paradigm shift in delivering the global target of sustainable economy and environment via the use of cheap, highly abundant, and renewable carbon resources. However, such development is extremely challenging due to the complexity of lignocellulose, and today most biomass is treated simply as waste. The solution lies in the design of multifunctional catalysts that can place effective control on substrate activation and product selectivity. This is, however, severely hindered by the lack of fundamental understanding of (i) the precise role of active sites, and (ii) the catalyst-substrate chemistry that underpins the catalytic activity. Moreover, active sites alone often cannot deliver the desired selectivity of products, and full understanding of the microenvironment of the active sites is urgently needed. Here, we review key recent advances in the study of reaction mechanisms of biomass conversion over emerging heterogeneous catalysts. These insights will inform the design of future catalytic systems showing improved activity and selectivity.

Construction of C-C bonds via photoreductive coupling of ketones and aldehydes in the metal-organic-framework MFM-300(Cr)

Construction of C-C bonds via reductive coupling of aldehydes and ketones is hindered by the highly negative reduction potential of these carbonyl substrates, particularly ketones, and this renders the formation of ketyl radicals extremely endergonic. Here, we report the efficient activation of carbonyl compounds by the formation of specific host-guest interactions in a hydroxyl-decorated porous photocatalyst. MFM-300(Cr) exhibits a band gap of 1.75 eV and shows excellent catalytic activity and stability towards the photoreductive coupling of 30 different aldehydes and ketones to the corresponding 1,2-diols at room temperature. Synchrotron X-ray diffraction and electron paramagnetic resonance spectroscopy confirm the generation of ketyl radicals via confinement within MFM-300(Cr). This protocol removes simultaneously the need for a precious metal-based photocatalyst or for amine-based sacrificial agents for the photochemical synthesis.

Selectively Producing Acetic Acid via Boric Acid-Catalyzed Fast Pyrolysis of Woody Biomass

Boric acid is recently proved to be a good substitute for conventional acidic catalytic materials. However, few studies used boric acid as a catalyst in biomass pyrolysis. This study focused on the catalytic effects of boric acid (BA) on pyrolysis behaviors of woody biomass. The birch wood flour (WF) was used as feedstock and treated by impregnation of boric acid solution. Both untreated and boric acid-treated samples (BW) were characterized by FTIR and SEM. Thermogravimetry (TG) and pyrolysis coupled with gas chromatography and mass spectrometry (Py-GC/MS) techniques were used for studying mass loss, composition, and distribution of evolved volatiles formed from pyrolysis process. Additionally, a small fixed-bed pyrolyzer with an amplificated loading amount was used to prepare liquid products, and further, GC/MS were used to analyze the composition of these liquid products. Different pyrolysis temperatures and boric acid/wood flour mass ratios were also studied. The main results are as follows. Boric acid infiltrated into both cell cavity and cell wall through impregnation treatment. FTIR analysis showed that boric acid reacted with wood flour to form B-O-C bond during the treatment. After the treatment of boric acid, the initial degradation temperatures and residual carbon contents were increased, while the maximum weight loss rates were decreased. Boric acid significantly altered the composition and distribution of volatile pyrolysis products of wood flour. It significantly increased the contents of small molecule compounds such as acetic acid and furfural but, decreased the contents of phenol derivatives with high molecular weights. And these changes became more pronounced as the temperature increased. When mass ratio of boric acid (BA) to wood flour (WF) was 2, the acetic acid accounted for 91.28% of the total product in the pyrolysis liquid, which was 14 times higher than that of untreated wood flour. Boric acid effectively catalyzed fast pyrolysis of woody biomass to selectively produce acetic acid

Control of zeolite microenvironment for propene synthesis from methanol

Optimising the balance between propene selectivity, propene/ethene ratio and catalytic stability and unravelling the explicit mechanism on formation of the first carbon–carbon bond are challenging goals of great importance in state-of-the-art methanol-to-olefin (MTO) research. We report a strategy to finely control the nature of active sites within the pores of commercial MFI-zeolites by incorporating tantalum(V) and aluminium(III) centres into the framework. The resultant TaAlS-1 zeolite exhibits simultaneously remarkable propene selectivity (51%), propene/ethene ratio (8.3) and catalytic stability (>50 h) at full methanol conversion. In situ synchrotron X-ray powder diffraction, X-ray absorption spectroscopy and inelastic neutron scattering coupled with DFT calculations reveal that the first carbon–carbon bond is formed between an activated methanol molecule and a trimethyloxonium intermediate. The unprecedented cooperativity between tantalum(V) and Brønsted acid sites creates an optimal microenvironment for efficient conversion of methanol and thus greatly promotes the application of zeolites in the sustainable manufacturing of light olefins.

Lower olefins are mainly produced from fossil resources and the methanol-to-olefins process offers a new sustainable pathway. Here, the authors show a new zeolite containing tantalum and aluminium centres which shows simultaneously high propene selectivity, catalytic activity, and stability for the synthesis of propene.

Investigations of Hydrocarbon Species on Solid Catalysts by Inelastic Neutron Scattering

The status of surface species on solid catalysts during heterogeneous catalysis is often mysterious. Investigations of these surface species are crucial to deconvolute the reaction network and design more efficient catalysts. Vibrational spectroscopy is a powerful technique to study the interactions between surface species and the catalysts and infrared (IR) and Raman spectroscopies have been widely applied to study reaction mechanisms in heterogeneous catalysis. However, IR/Raman spectra are difficult to model computationally and important vibrational modes may be IR-, Raman- (or both) inactive due to restrictions by optical selection rules. Inelastic neutron scattering (INS) is another form of vibrational spectroscopy and relies on the scattering of neutrons by the atomic nucleus. A consequence of this is that INS is not subject to any optical selection rules and all vibrations are measurable in principle. INS spectroscopy has been used to investigate surface species on catalysts in a wide range of heterogeneous catalytic reactions. In this mini-review, we focus on applications of INS in two important fields: petrochemical reactions and C1 chemistry. We introduce the basic principles of the INS technique, followed by a discussion of its application in investigating two key catalytic systems: (i) the behaviour of hydrocarbons on metal-oxide and zeolite catalysts and (ii) the formation of hydrocarbonaceous species on methane reforming and Fischer–Tropsch catalysts. The power of INS in studying these important catalytic systems is demonstrated.

A sustainable natural nanofibrous confinement strategy to obtain ultrafine Co3O4 nanocatalysts embedded in N-enriched carbon fibers for efficient biomass-derivative in situ hydrogenation

Both exploring high-performance catalytic materials with ultrafine active sites from sustainable feedstocks and selective transformation of bio-renewable carboxides are very significant and challenging topics. Herein, we utilized bacterial cellulose to construct highly dispersed Co3O4 nanocatalysts embedded within nitrogen-doped carbon nanofibers (NCNFs). Benefiting from the nanofibrous confinement strategy, a urea-assisted carbonation process and a mild nitrate decomposition process, the cobalt precursor was transformed into ultrasmall and homogeneous Co3O4 nanoparticles (NPs) of ca. 1.57 nm, which is to our knowledge the smallest value among the reported supported Co3O4 materials. The as-obtained Co3O4/NCNF exhibits superior catalytic activity for the selective hydrogenation of bioderived α,β-unsaturated aldehydes with 2-propanol as a H-source, yielding 90-100% conversion under mild conditions. Controlled experiments and detailed characterization revealed that the three-dimensional nanofibrous porous structure can be favourable for improved diffusion and mass transfer, while the uniform distribution of ultrafine Co3O4 NPs and urea-derived abundant basic sites exhibit synergism in the adsorption and activation of reactants, which contributes to excellent catalytic performance. This approach opens up a new way to the design and fabrication of highly dispersed nanocatalysts based on NCNF materials from sustainable natural polymers for biomass valorization.

Niobium Oxides as Heterogeneous Catalysts for Biginelli Multicomponent Reaction

This study reports a simple, reusable, and recoverable niobium-based heterogeneous catalysts for Biginelli multicomponent reactions. Different methods of catalysts preparation were investigated. For this purpose, HY-340 (Nb₂O₅·nH₂O) and Nb₂O₅ were chemically and/or thermally treated and investigated as catalysts for dihydropyrimidinones (DHPMs) production. The catalysts were characterized by scanning electron microscopy, high-resolution transmission electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, temperature-programmed desorption of NH₃, adsorption/desorption of N₂ at -196 °C, and thermogravimetric and differential thermal analysis. The characterization results showed that niobium oxides have the potential to be used as catalysts because of high crystallinity and large surface area. Among the tested catalysts, Nb₂O₅ chemically treated (Nb₂O₅/T) showed the best catalytic performance. In the absence of solvents, 94% yield of DHPMs was achieved. Also, Nb₂O₅/T can be reused three times without a significant yield decrease. Additionally, a feasible reaction pathway was suggested based on the Knoevenagel mechanism for DHPM synthesis using niobium-based catalysts.