Saturated And Unsaturated Research Articles

Selective hydrogenation of unsaturated vinyl ethers in two‑chamber gauge‐reactor

A pressure gauge was incorporated into a two‐chamber glass H‐tube to continuously monitor the pressure inside a reactor when working with gases. The ex situ generated H2, D2, acetylene and CO2 were tested in pressure gauge reactors, and calibration curves were plotted. A series of unsaturated compounds with two or more double C=C bonds accessible for hydrogenation were synthesized for hydrogenation. The hydrogenation proceeded well due to constant pressure control, and the desired products were isolated in good yields. The same hydrogenation procedures were then carried out using steel autoclaves to verify the results and compare them. Surprisingly, almost the same results were obtained, confirming the effectiveness of self‐made glass reactors. The hydrogenation mechanism was further investigated using D‐labeled reagents. The kinetics of hydrogenation was studied both in manometric glass reactors and in steel autoclaves, which showed a similar nature of the main process in both reaction units. Thus, the created reactors can be effectively used in barometric transformations instead of steel autoclaves in appropriate cases.

Highly Conjugated Nanozyme with Non Coordination Saturation for Cascaded Enhanced POD Reaction Driving Antibacterial Therapy

AbstractThe misuse of antibiotics leads to emergence of drug‐resistant bacteria. Developing artificial nanozymes with high stability and excellent catalytic performance is desirable to substitute for antibiotics, but still remains huge challenge. Herein, the study reports a new strategy for cascaded enhanced peroxidase (POD) reaction driving antibacterial therapy via constructing 2D conjugated metal‐organic frameworks (MOFs) with non coordination saturation as nanozyme. It is demonstrated that the non coordination saturation Cu atom promotes the adsorption of H2O2, followed by the Cu‐HHTP MOFs with high conjugated structure can enhance the photogenerated electron transfer for ·OH generation in POD reaction. The sequential enhancement of substrate adsorption and decomposition endows the as‐made Cu‐HHTP MOFs with outstanding antibacterial property of >99.9999% elimination with a concentration only 1/133 that of traditional nanozyme. In addition, the study also certifies its excellent in vivo antimicrobial activity and biocompatibility, indicating the therapeutic potential for infections by drug‐resistant bacteria.

Enhancing Hydride Transfer in Catalytic Hydrogenation via σ-Electron-Induced Polarization of Imines.

In this study, we investigated the role of aluminum cations in facilitating hydride transfer during the hydrogenation of imines within the context of Noyori-type metal-ligand cooperative catalysis. We propose a novel model involving aluminum cations directly coordinated with imines to induce activation from the lone pair electron site, a phenomenon termed σ-induced activation. The aluminum metal-hydride amidate complex ("HMn-NAl") exhibits a higher ability of hydride transfer in the hydrogenation of imines compared to its lithium counterpart ("HMn-NLi"). Density functional theory (DFT) calculations uncover that the aluminum cation efficiently polarizes unsaturated bonds through σ-electron-induced activation in the transition state of hydride transfer, thereby enhancing substrate electrophilicity more efficiently. Additionally, upon substrate coordination, aluminum's coordination saturation improves the hydride nucleophilicity of the HMn-NAl complex via the breakage of the Al-H coordination bond.

The loss of dissolved organic matter from biological soil crust at various successional stages under rainfall of different intensities: Insights into the changes of molecular components at different rainfall stages

Biological soil crusts (BSCs) are typical covers in arid and semiarid regions. The dissolved organic matter (DOM) of BSCs can be transported to various aquatic ecosystems by rainfall-runoff processes. However, the spatiotemporal variation in quality and quantity of DOM in runoff remains unclear. Herein, four kinds of runoff plots covered by four successional stages of BSCs were set up on slopes, including bare runoff plot (BR), cyanobacteria crust covered runoff plot (CR), mixed crust covered runoff plot (MIR), and moss crust covered runoff plot (MOR). The quantity and quality of DOM in runoff during rainfall was investigated based on the stimulated rainfall experiments combined with optical spectroscopy and ultra-high resolution mass spectrometry analyses. The results showed that the DOM concentrations (i.e., 0.30 to 45.25 mg L−1) in runoff followed the pattern of MOR>MIR>CR>BR, and they were exponentially decreased with rainfall duration. The DOM loss rate of BR (8.26 to 11.64 %) was significantly greater than those of CR, MIR, and MOR (0.84 to 3.22 %). Highly unsaturated compounds (HUCs), unsaturated aliphatic compounds (UACs), saturated compounds (SCs), and peptide-like compounds (PLCs) were the dominated compounds of the water extractable DOM from the original soils. Thereinto, PLCs and UACs were more easily leached into runoff during rainfall. The relatively intensity of HUCs in runoff generally decreased with rainfall duration, while the relatively intensities of UACs, PLCs, and SCs slightly increased with rainfall duration. These findings suggested that the DOM loss rate was effectively decreased with the successional of BSCs during rainfall; meanwhile, some labile compounds (e.g., PLCs and UACs) were transported into various aquatic ecosystems by rainfall-runoff processes.

Dichlorocarbenation of polar olefins in conditions of microwave irradiation

Objectives. To evaluate the influence and efficiency of using microwave irradiation on the dichlorocarbenation of polar olefins. To determine the conditions (reaction time and process temperature) under which the maximum yield of target gem-dichlorocyclopropanes is achieved.Methods. The target compounds were obtained by classical methods of organic synthesis— acetalization of polyols and dichlorocarbenation of unsaturated compounds. The preparation of gem-dichlorocyclopropanes was carried out using the microwave activation method on a Sineo device (microwave system for organic synthesis, made in China). In order to determine the qualitative and quantitative composition of the reaction masses, gas–liquid chromatography (using the Kristall 2000 hardware complex), mass-spectroscopy (using Chromatek-Kristall 5000M device with NIST 2012), and nuclear magnetic resonance spectroscopy (using Bruker AM-500 device with operating frequencies of 500 and 125 MHz) were carried out.Results. Under microwave irradiation at 25°C for 2 h with the maximum yield (92–98%), the target substituted gem-dichlorocyclopropanes were obtained: 2-(2,2-dichloro-3-methylcyclopropyl)-1,3-dioxolane, 2-(2, 2-dichloro-3-phenylcyclopropyl)-1,3-dioxolane, 8,8-dichloro4-isopropyl-3,5-dioxabicyclooctane, diethyl-2,2-dichloro-3-phenylcyclopropane-1,1-dicarboxylate, and diethyl-2,2-dichloro-3isopropylcyclopropane-1,1-dicarboxylate.Conclusions. Under the conditions herein proposed, the use of the microwave stimulation method in the dichlorocarbenation of double C=C bonds containing polar substituents allows the reduce the temperature and reaction time to be significantly reduced, and the yield of target gem-dichlorocyclopropanes to be increased.

Cobalt/Photoredox Cooperative Catalysis‐Enabled Cycloaddition Reactions of 1,6‐Diynes and Related Compounds

AbstractCobalt catalysts have recently gained considerable attention as alternatives to catalysts based on precious transition metals such as Rh and Ir. Recently, Co/photoredox cooperative catalysis has emerged as a powerful tool that enables versatile transformations, including cycloaddition reactions of unsaturated compounds. In particular, 1,6‐diyne derivatives are fascinating substrates for these reactions because the corresponding exocyclic 1,3‐diene products can be further transformed into sp3‐rich carbocycles and heterocycles via functionalization of the diene moiety. The dual catalytic system can facilitate not only the cycloaddition based on the activation of the π‐bond only, such as alkyne cyclotrimerization, but also the cycloaddition involving σ‐bond activation. This Concept highlights the recent advances in Co/photoredox cooperative‐catalysis‐enabled cycloaddition reactions, focusing on the reactions of 1,6‐diyne substrates, which are difficult to perform when well‐defined cationic CoI catalysis is employed.

Description of Some Methodologies for the Synthesis of 1,4-Naphthoquinone Derivatives and Examples of their Biological Activity: A Review

Abstract: An alternative to finding new drugs for the treatment of various diseases is the chemical modification of the structure of compounds of natural origin. Among them, naphthoquinones are very interesting candidates, as they are antibacterial, antifungal, antiparasitic, and anticancer agents. Naphthoquinones are redox compounds that can accept one or two electrons, generating reactive oxygen species in the cell and producing cell apoptosis. Naphthoquinones are unsaturated compounds containing a dicarbonyl sequence in the para position, which is highly reactive. Several studies of the chemical modification of naphthoquinones, either of natural origin (such as lapachol or juglone) or synthetic origin, have demonstrated the great importance and versatility of this type of compound. Polyhydroxylated derivatives, amino, thioethers, and conjugated heterosystems (indole or pyrrole groups) have been synthesized. Depending on the type of derivative, their specific use against certain types of microorganisms or cancer cell lines has been demonstrated.

Synthesis and Properties of Photocurable Polymers Derived from the Polyesters of Glycerol and Aliphatic Dicarboxylic Acids.

The rapid development of 3D printing technology and the emerging applications of shape memory elastomer have greatly stimulated the research of photocurable polymers. In this work, glycerol (Gly) was polycondensed with sebacic, dodecanedioic, or tetradecanedioic acids to provide precursor polyesters with hydroxyl or carboxyl terminal groups, which were further chemically functionalized by acryloyl chloride to introduce sufficient, photocurable, and unsaturated double bonds. The chemical structures of the acrylated polyesters were characterized by FT IR and NMR spectroscopies. The photoinitiated crosslinking behavior of the acrylated polyesters under ultraviolet irradiation without the addition of any photoinitiator was investigated. The results showed that the precursor polyesters that had a greater number of terminated hydroxyls and a less branched structure obtained a relatively high acetylation degree. A longer chain of aliphatic dicarboxylic acids (ADCAs) and higher ADCA proportion lead to a relatively lower photopolymerization rate of acrylated polyesters. However, the photocured elastomers with a higher ADCA proportion or longer-chain ADCAs resulted in better mechanical properties and a lower degradation rate. The glass transition temperature (Tg) of the elastomer increased with the alkyl chain length of the ADCAs, and a higher Gly proportion resulted in a lower Tg of the elastomer due to its higher crosslinking density. Thermal gravimetric analysis (TGA) showed that the chain length of the ADCAs and the molar ratio of Gly to ADCAs had less of an effect on the thermal stability of the elastomer. As the physicochemical properties can be adjusted by choosing the alkyl chain length of the ADCAs, as well as changing the ratio of Gly:ADCA, the photocurable polyesters are expected to be applied in multiple fields.

Solvent-Free Synthesis Enables Encapsulation of Subnanometric FeOx Clusters in Pure Siliceous Zeolites for Efficient Catalytic Oxidation Reactions.

Metal/metal oxide clusters possess a higher count of unsaturated coordination sites than nanoparticles, providing multiatomic sites that single atoms do not. Encapsulating metal/metal oxide clusters within zeolites is a promising approach for synthesizing and stabilizing these clusters. The unique feature endows the metal clusters with an exceptional catalytic performance in a broad range of catalytic reactions. However, the encapsulation of stable FeOx clusters in zeolite is still challenging, which limits the application of zeolite-encapsulated FeOx clusters in catalysis. Herein, we design a modified solvent-free method to encapsulate FeOx clusters in pure siliceous MFI zeolites (Fe@MFI). It is revealed that the 0.3-0.4 nm subnanometric FeOx clusters are stably encapsulated in the 5/6-membered rings intersectional voids of the pure siliceous MFI zeolites. The encapsulated Fe@MFI catalyst with a Fe loading of 1.4 wt % demonstrates remarkable catalytic activity and recycle stability in the direct oxidation of methane, while also promoting the direct oxidation of cyclohexane, surpassing the performance of conventional zeolite-supported Fe catalysts.

Rational solvent selection for the preparation of industrial monolithic supported liquid-phase (SLP) olefin hydroformylation catalyst

Heterogenisation of the hydroformylation (HyFo) process converting C4 olefins and syngas (CO/H2) to n-pentanal can substantially reduce its carbon footprint by simplifying downstream processing. Current upscaling efforts include constructing a pilot plant containing a Rh-diphosphite-stabiliser supported liquid-phase (SLP) catalyst. The air-sensitive nature of the catalyst requires in-situ impregnation of the porous support material with the liquid phase components (Rh-precursor, ligand, stabiliser) entailing the use of large quantities of an organic solvent. Environment, health, and safety (EHS) as well as regulatory aspects prompt the search for an alternative to dichloromethane (DCM), which was used as standard solvent for lab-scale studies. To obtain alternatives to DCM, the replacement solvent methyl tert-butyl ether (MTBE) and in-silico screening of more than 5000 solvent candidates has been performed covering boiling points and solubility predictions by COSMO-RS as well as carcinogenicity- and mutagenicity predictions by quantitative structure–activity relationship (QSAR) models. The final list of solvent candidates contained unsaturated compounds (alkenes, alkynes) in addition to ether- and ester-functionalised solvents, which are typically recommended as DCM replacements. Sufficiently high solubilities of ligand and stabiliser to prepare the desired SLP catalyst were experimentally determined in the following solvents: methyl propionate (MP), dimethoxymethane (DMM), MTBE, tetrahydrofuran (THF) and DCM for benchmarking, and a monolithic SLP catalyst prepared with MTBE demonstrated to perform equally well in the HyFo reaction of 1-butene as the benchmark catalyst prepared using DCM solvent. Overall, the study demonstrates a practical approach for selecting solvents with a greener profile for making catalyst systems applicable for large-scale production.

Catalytic open metal sites in Ti-MOFs obtained through plasma treatment for oxidative desulfurization

Titanium-based metal–organic frameworks (Ti-MOFs) are known for their redox catalytic potential, inherently limited by coordination saturation. Defect engineering introduces the unsaturated metal sites, but introducing defects for improved performance is challenging due to titanium's hydrolysis tendency and the absence of stable Ti-clusters. This study employs an Ar plasma post-synthesis treatment, adjusting defect quantities by varying duration and intensity. The resulting plasma-induced defective MUV-10, with nearly 50 % missing linkers per cluster, displays heightened catalytic activity in oxidative desulfurization. This activity directly correlates with missing linker numbers, emphasizing the superior activity of defective open sites. Defect formation enhances intrinsic activity around unsaturated metal catalytic sites, rather than increasing active site density. This defect-generation method is adaptable to other Ti-MOFs and potentially to diverse MOFs.

Constructing surface oxygen defects at CuO–Co3O4 interface to boost toluene oxidation over CuO/Co3O4 catalysts

As a typical heterogeneous catalytic process, the catalytic combustion of toluene over Co3O4-based catalysts is strongly depends on the surface properties of catalysts, especially the concentration of surface oxygen defects. Here, a novel way was proposed to construct chemically bonded CuO–Co3O4 interface by chemical deposition of CuO onto Co3O4 nanoflowers. The interfacial refinement effect between CuO and Co3O4 support disrupted the ordered atomic arrangement and created countless unsaturated coordination sites at CuO–Co3O4 interface, inducing a significant generation of surface oxygen defects. Surface-rich oxygen vacancies enhanced the capacity of 20 %CuO/Co3O4–R to adsorb and activate oxygen species. Benefiting from this, 90 % toluene conversion was reached at 228 °C over 20 %CuO/Co3O4–R, which was much lower than that over 20 %CuO/Co3O4–S prepared by impregnation method and CuO/Co3O4-mix obtained by mechanically mixing way. In-situ DRIFTS analysis revealed that toluene could be directly decomposed into benzaldehyde at the highly defective CuO–Co3O4 interface, leading to toluene oxidation following the path of toluene → benzaldehyde → benzoate → maleic anhydride → water and carbon dioxide over 20 %CuO/Co3O4–R, which was significantly different from decomposition mechanism over 20 %CuO/Co3O4–S. Additionally, 20 %CuO/Co3O4–R displayed terrific recyclability and outstanding stability, showing good application potential.

Optimized crystalline/amorphous NiFeS@NiMoP on nickel foam as dual-functional electrocatalysts for urea-water splitting

Urea electrolysis is a potential choice for generating hydrogen (H2) to fuel several purified energy technologies. In practice, the strategy for designing a transition metal sulfides (TMSs) phosphides (TMPs) electrocatalyst coupled with interfacial engineering applied into hydrogen evolution reaction (HER) and urea oxidation reaction (UOR) is a extremely desirable and meaningful challenge. Herein, crystalline/amorphous heterostructure denoted as NiFeS@NiMoP/NF was made. Electrochemical tests show that：NiFeS@NiMoP/NF was active for both the HER and UOR process, which may due to the synergistic effect of Ni-based sulfides together with phosphides markely facilitated electron transfer and reaction kinetics and crystalline/amorphous structure provided ample unsaturated coordination configurations to enhance the adsorption of reactants. Impressively, NiFeS@NiMoP/NF displays comparatively low overpotential with value of 56.4 mV for HER and potential of 1.32 V for UOR to deliver the current density of 10 mA cm−2, and drives the overall splitting of urea-water electrolysis at 1.40 V in 1.0 M KOH +0.5 M urea at 10 mA cm−2. This approach may shed light on the designing and developing crystalline/amorphous bifunctional materials for energy conversion and application.

РАЗРАБОТКА МЕТОДА ИДЕНТИФИКАЦИИ И ОПРЕДЕЛЕНИЕ ЭФИРНОГО МАСЛА В ПОБЕГАХ ТУИ ЗАПАДНОЙ (THUJA OCCIDENTALIS)

The purpose of the study is to develop methods for identifying terpenoids and assessing the quantitative content of essential oil in the shoots of western thuja (Thuja occidentalis). The object of the study was samples of thuja occidentalis shoots. The raw materials were used fresh. To carry out qualitative reactions, well-known methods were selected that are most often used in the analysis of essential oil raw materials. Identification of essential oil components was carried out by TLC on Silufol plates. A solution of α-pinene was used as a standard. The quantitative content of essential oil in the raw materials was determined by steam distillation in accordance with the GPM method 1.5.3.00010.15 Determination of the content of essential oil in medicinal plant raw materials and medicinal herbal preparations. The authors proposed qualitative reactions for identifying terpenoids in raw materials, which can be used to form the “Authenticity” section for a new type of raw material - thuja occidentalis shoots. α-pinene was identified by TLC. A quantitative assessment of the essential oil content in raw materials was carried out. Qualitative reactions were experimentally selected to confirm the presence of terpenoids in alcoholic extracts from thuja occidentalis shoots, as well as for unsaturated compounds in essential oil obtained by steam distillation. Using TLC, α-pinene was identified in the analyzed samples. The presence of additional 8 adsorption zones in the essential oil samples was also revealed. Assessment of the quantitative content of essential oil in raw materials, carried out according to method 2 OFS.1.5.3.00010.15 “Determination of the content of essential oil in medicinal plant raw materials and medicinal herbal preparations.” The data obtained during the experiment allows us to recommend the inclusion of an essential oil content of at least 2.84% in the quality indicators of western thuja shoots.

Photoinduced [3 + 2] Cycloadditions of Aryl Cyclopropyl Ketones with Alkynes and Alkenes.

The five-membered ring skeleton is one of the most pivotal in the area of pharmaceutical and natural products. [3 + 2] cycloadditions of cyclopropyl and unsaturated compounds are a highly efficient and atom-economical way to build a five-member compound. The previous works about the kind of [3 + 2] cycloadditions usually utilized metal or organic small molecule catalysts. However, an ideal [3 + 2] cycloaddition reaction that smoothly happens without any additives and catalysts under mild conditions is underdeveloped. Hence, we report [3 + 2] cycloadditions of aryl cyclopropyl without any additives and catalysts under purple LED. In this method, a broad scope of cyclopropyl, alkyne, and alkene was very compatible, especially drug derivatives ibuprofen and Ioxoprofen, to obtain the corresponding cycloaddition product with a good yield up to 93%.

Solvent Effects on Heterogeneous Catalysis for the Selective Hydrogenation

AbstractSolvent effects add a new dimension for tuning the activity and selectivity of heterogeneous catalytic reactions, which is extensively employed in the hydrogenation of unsaturated compounds with multiple functional groups. In this concept, we briefly summarize recent developments on how the solvent effects affect the catalytic performance from the following aspects: 1) the polarity of the solvent can influence the interaction between the solvent and the reactant or intermediate; 2) the composition of mixed solvent can influence the reactivity of the reactant or intermediate; 3) solvent effect varies with the metal identity and support; 4) the solvent can induce surface modification of the supported catalysts. This summarization will provide insights into the rational development of efficient and selective heterogeneous hydrogenation catalytic system to realize the precise synthesis of desired chemicals.

Characterization and differentiation of dissolved organic matter in leachate derived from an old Japanese landfill site through Orbitrap mass spectrometry

AbstractElucidating the characteristics of dissolved organic matter (DOM) is crucial to assessing its impact on the bioavailability and mobility of pollutants in landfill leachate. This study reports a comprehensive 5–month investigation into the characteristics of DOM in leachate from an old Japanese landfill, collected at six different sampling points. The molecular composition, chemical properties, and structural characteristics of DOM were assessed using Orbitrap mass spectrometry and spectral analysis. The leachate DOM mainly consisted of CHO-containing molecules (58.5–88.9%), low-oxygen unsaturated phenolic compounds (40.5–54.0%), and aliphatic compounds (19.4–47.3%), with slight variation among sampling points. A significant portion of the nominal oxidation state of carbon was in the reduced zone (76.2–95.4%). The results underscore the distinct molecular composition of DOM in mature Japanese landfill leachate compared to young and mature leachates from other countries. Two of six sampling points, with notable differences in molecular characteristics, were compared and elucidated. The composition of landfill waste, rather than landfill age, was the main factor affecting the characteristics and differentiation of leachate DOM.

Selective Deep Hydrogenation of Acenaphthene to High‐Density Fuel On supported Ru Catalysts: The Role of Strong Metal‐Support Interaction

Developing high‐performance aviation fuel is highly desired for the rapid development of supersonic aircraft. Herein, selective deep hydrogenation of polycyclic aromatics to a high‐density fuel is developed over a Ru‐based catalyst. The influences of strong Ru‐support interaction on tailoring the reaction pathways of acenaphthene hydrogenation were investigated using different oxide supports (SiO2, CeO2, TiO2). Ru/CeO2 and Ru/TiO2 with strong SMSI possess abundant electron‐deficient Ruδ+ species which exhibit a good ability to promote H2 dissociation and increase the isomerization rate of saturated aromatic compounds. Due to the enhanced adsorption of aromatic molecules, Ru/CeO2 (1.30 μmol·min‐1·g‐1) exhibits superior catalytic activity in comparison to Ru/TiO2 (1.25 μmol·min‐1·g‐1) during acenaphthene hydrosaturation, while Ru/TiO2 exhibits the highest isomerization reaction rate (7.60 × 10‐2 μmol·min‐1·g‐1) because of its excellent hydrogen spillover ability and high content of Ruδ+ species. The best catalytic activity with 96% selectivity of ccc‐perhydroacenaphthene was achieved on Ru/TiO2, and an isomerization mechanism of perhydroacenaphthene isomers was proposed.

Grain‐Boundary‐Rich RuO2 Porous Nanosheet for Efficient and Stable Acidic Water Oxidation

RuO2 has been considered as the most likely acidic oxygen evolution reaction (OER) catalyst to replace IrO2, but its performance, especially long‐term stability under harsh acidic conditions, is still unacceptable. Here, we propose a grain boundary (GB) engineering strategy by fabricating the ultrathin porous RuO2 nanosheet with abundant of grain boundaries (GB‐RuO2) as an efficient acid OER catalyst. The involvement of GB induces significant tensile stress and creates an unsaturated coordination environment, effectively optimizing the adsorption of intermediates and stabilizing active site structure during OER process. Notably, the GB‐RuO2 not only exhibits a low overpotential (η10= 187 mV) with an ultra‐low Tafel slope (34.5 mV dec‐1), but also steadily operates for over 550 h in 0.1 M HClO4. Quasi in situ/operando methods confirm that the improved stability is attributed to GB preventing Ru dissolution and greatly inhibiting the lattice oxygen oxidation mechanism (LOM). A proton exchange membrane water electrolysis (PEMWE) using the GB‐RuO2 catalyst operates a low voltage of 1.669 V at 2 A cm‐2 and operates stably for 100 h at 100 mA cm‐2.

Orbital-scale understanding of the surface effect of the MgCl2 in the Ziegler–Natta catalyst for ethylene polymerization: A computational study

Ziegler-Natta catalyst is a widely used olefin polymerization catalyst in petrochemical industries. However, the role of each catalyst component is not clear due to the complexity of composition and structure. MgCl2 is a suitable support for Ziegler-Natta catalyst because its crystal structure is similar to that of TiCl3, and the surface effect of MgCl2 in Ziegler-Natta catalyst system was explored in ethylene polymerization at the orbital scale. A series of the stable surface-supported catalysts with unsaturated coordination Mg2+ were used to simulate the mechanism of ethylene polymerization by the periodic density functional theory. This study found that MgCl2 with different surfaces regulates the activity of the catalyst by adjusting the d band centre of the catalyst active centre. This concept can be used to explain the surface effect of support in general catalysts.