Polyoxometalates-Mediated Selectivity in Pt Single-Atoms on Ceria for Environmental Catalysis.

Optimizing the reactivity and selectivity of single-atom catalysts (SACs) remains a crucial yet challenging issue in heterogeneous catalysis. This study demonstrates selective catalysis facilitated by a polyoxometalates-mediated electronic interaction (PMEI) in a Pt single-atom catalyst supported on CeO2 modified with Keggin-type phosphotungstate acid (HPW), labeled as Pt1/CeO2-HPW. The PMEI effect originates from the unique arrangement of isolated Pt atoms and HPW clusters on CeO2 surface. Electrons are transferred from ceria support to the electrophilic tungsten in HPW clusters, and subsequently, Pt atoms donate electrons to the now electron-deficient ceria. This phenomenon enhances the positive charge of Pt atoms, moderating O2 activation and limiting lattice oxygen mobility compared to the conventional Pt1/CeO2 catalyst. The resulting electronic structure of Pt combined with the strong and local acidic environment of HPW on Pt1/CeO2-HPW leads to improved degradation of NH3, N2 selectivity in the NO conversion, and CO2 yield when inputting volatile organic compounds. This study sheds the light on the design of SACs with balanced reactivity and selectivity for environmental catalysis applications.

Phosphotungstic Acid as a Dechlorination Agent Collaborates with CeO2 for Synergistic Catalytic Elimination of NOx and Chlorobenzene.

The development of efficient technologies for the synergistic catalytic elimination of NOx and chlorinated volatile organic compounds (CVOCs) remains challenging. Chlorine species from CVOCs are prone to catalyst poisoning, which increases the degradation temperature of CVOCs and fails to balance the selective catalytic reduction of NOx with the NH3 (NH3-SCR) performance. Herein, synergistic catalytic elimination of NOx and chlorobenzene has been originally demonstrated by using phosphotungstic acid (HPW) as a dechlorination agent to collaborate with CeO2. The conversion of chlorobenzene was over 80% at 270 °C, and the NOx conversion and N2 selectivity reached over 95% at 270-420 °C. HPW not only allowed chlorine species to leave as inorganic chlorine but also enhanced the BroÌ·nsted acidity of CeO2. The NH4+ produced in the NH3-SCR process can effectively promote the dechlorination of chlorobenzene at low temperatures. HPW remained structurally stable in the synergistic reaction, resulting in good water resistance and long-term stability. This work provides a cheaper and more environmentally friendly strategy to address chlorine poisoning in the synergistic reaction and offers new guidance for multipollutant control.

Strong metal oxide-zeolite interactions during selective catalytic reduction of nitrogen oxides.

In response to the stricter EU VII emission standards and the "150 â„ƒ challenge", selective catalytic reduction by ammonia (NH3-SCR) catalysts for motor vehicles are required to achieve high NO conversion below 200 °C. Compounding metal oxides with zeolites is an important strategy to design the low-temperature SCR catalysts. Here, we original prepared Cu-SSZ-13 @ MnGdOx (Cu-Z @ MGO), which achieved over 90% NO conversion and 95% N2 selectivity at 150 â„ƒ. It has been demonstrated that a uniform mesoporous loaded layer of MGO grows on Cu-Z, and a recrystallization zone appears at the MGO-Cu-Z interface. We discover that the excellent low-temperature SCR activity derives from the strong metal oxide-zeolite interaction (SMZI) effects. The SMZI effects cause the anchor and high dispersion of MGO on the surface of Cu-Z. Driven by the SMZI effects, the Mn3+/Mn4+ redox cycle ensures the low and medium temperature-SCR activity and the Cu2+/Cu+ redox cycle guarantees the medium and high temperature-SCR activity. The introduction of MGO improves the reaction activity of -NH2 species adsorbed at Mn sites at 150 â„ƒ, achieving a cycle of reduction and oxidation reactions at low temperatures. This strategy of inducing SMZI effects of metal oxides and zeolites paves a way for development of high-performance catalysts.

Boosting Ozone Catalytic Oxidation of Toluene at Room Temperature by Using Hydroxyl-Mediated MnOx/Al2O3 Catalysts.

Ozone catalytic oxidation (OZCO) has gained great interest in environmental remediation while it still faces a big challenge during the deep degradation of refractory volatile organic compounds (VOCs) at room temperature. Hydroxylation of the catalytic surface provides a new strategy for regulating the catalytic activity to boost VOC degradation. Herein, OZCO of toluene at room temperature over hydroxyl-mediated MnOx/Al2O3 catalysts was originally demonstrated. Specifically, a novel hydroxyl-mediated MnOx/Al2O3 catalyst was developed via the in situ AlOOH reconstruction method and used for toluene OZCO. The toluene degradation performance of MnOx/Al2O3 was significantly superior to those of most of the state-of-the-art catalysts, and 100% toluene was removed with an excellent mineralization rate (82.3%) and catalytic stability during OZCO. ESR and in situ DRIFTs results demonstrated that surface hydroxyl groups (HGs) greatly improved the reactive oxygen species generation, thus dramatically accelerating the benzene ring breakage and deep mineralization. Furthermore, HGs provided anchoring sites for uniformly dispersing MnOx and greatly enhanced toluene adsorption and ozone activation. This work paves a way for deep decomposition of aromatic VOCs at room temperature.

Expediting Toluene Combustion by Harmonizing the Ce-O Strength over Co-Doped CeZr Oxide Catalysts.

Low-temperature catalytic degradation of volatile organic compounds (VOCs) by enhancing the activity of non-precious metal catalysts has always been the focus of attention. The mineralization of aromatic VOCs requires the participation of a large number of oxygen atoms, so the activation of oxygen species is crucial in the degradation reaction. Herein, we originally adjust the Ce-O bond strength in CeZr oxide catalysts by cobalt doping to promote the activation of oxygen species, thus improving the toluene degradation performance while maintaining high stability. Subsequent characterizations and theoretical calculations demonstrate that the weakening of the Ce-O bond strength increases the oxygen vacancy content, promotes the activation of oxygen species, and enhances the redox ability of the catalysts. This strategy also promotes the activation of toluene and accelerates the depletion of intermediate species. This study will contribute a strategy to enhance the activation ability of oxygen species in non-noble metal oxide catalysts, thereby enhancing the degradation performance of VOCs.

Boosting SO2-Resistant NOx Reduction by Modulating Electronic Interaction of Short-Range Fe-O Coordination over Fe2O3/TiO2 Catalysts.

SO2-resistant selective catalytic reduction (SCR) of NOx remains a grand challenge for eliminating NOx generated from stationary combustion processes. Herein, SO2-resistant NOx reduction has been boosted by modulating electronic interaction of short-range Fe-O coordination over Fe2O3/TiO2 catalysts. We report a remarkable SO2-tolerant Fe2O3/TiO2 catalyst using sulfur-doped TiO2 as the support. Via an array of spectroscopic and microscopic characterizations and DFT theoretical calculations, the active form of the dopant is demonstrated as SO42- residing at subsurface TiO6 locations. Sulfur doping exerts strong electronic perturbation to TiO2, causing a net charge transfer from Fe2O3 to TiO2 via increased short-range Fe-O coordination. This electronic effect simultaneously weakens charge transfer from Fe2O3 to SO2 and enhances that from NO/NH3 to Fe2O3, resulting in a remarkable "killing two birds with one stone" scenario, that is, improving NO/NH3 adsorption that benefits SCR reaction and inhibiting SO2 poisoning that benefits catalyst long-term stability.

Low-Temperature Combustion of Toluene over Cu-Doped SmMn2O5 Mullite Catalysts via Creating Highly Active Cu2+-O-Mn4+ Sites.

Catalytic combustion of volatile organic compounds (VOCs) at low temperatures is still an urgent issue to be solved. Herein, low-temperature combustion of toluene over Cu-doped SmMn2O5 mullite catalysts via creating highly active Cu2+-O-Mn4+ sites has been originally demonstrated. Cu-doped SmMn2O5 mullite catalysts exhibited 90% conversion of toluene at 206 °C and displayed robust stability even in the presence of water. It has been demonstrated that Cu doping created Cu2+-O-Mn4+ active composite sites that were more exposed after removing surface Sm species via acid-etching. Benefiting from this, the redox and oxygen activation ability of catalysts was significantly enhanced. The consumption of benzaldehyde and benzoic acid as intermediate species and the CO2 generation ability were apparently promoted, which were the direct reasons for the enhanced low-temperature combustion of toluene. This work provides novel ideas for the development of high-performance catalysts for low-temperature VOC combustion, which has great industrial application prospects.

Coking- and Sintering-Resistant Ni Nanocatalysts Confined by Active BN Edges for Methane Dry Reforming.

Methane dry reforming (MDR) has attracted significant attention for effectively consuming greenhouse gases and producing valuable syngas. The development of coking- and sintering-resistant catalysts is still a challenge. Herein, highly active Ni nanocatalysts confined by the active edges of boron nitride have been originally developed, and the coking- and sintering-resistant MDR mechanism has also been unraveled. The active edges of boron nitride consisted of boundary BOx species interact with Ni nanoparticles (NPs), which can contribute to the activation of both CH4 and CO2. The etching of BN is restrained under the buffer of boundary BOx species. Operando spectra reveal that the formation and conversion of active bicarbonate species is accelerated by the boundary BOx species. The complete decomposition of CH4 is suppressed, and thus the coke formation is restricted. The functional groups of active BN edges are confirmed to stabilize the Ni NPs and facilitate the MDR reaction. This work provides a novel approach for the development of coking- and sintering-resistant catalysts for MDR.

Self-Defense Effects of Ti-Modified Attapulgite for Alkali-Resistant NOx Catalytic Reduction.

Nowadays, the serious deactivation of deNOx catalysts caused by alkali metal poisoning was still a huge bottleneck in the practical application of selective catalytic reduction of NOx with NH3. Herein, alkali-resistant NOx catalytic reduction over metal oxide catalysts using Ti-modified attapulgite (ATP) as supports has been originally demonstrated. The self-defense effects of Ti-modified ATP for alkali-resistant NOx catalytic reduction have been clarified. Ti-modified ATP with self-defense ability was obtained by removing alkaline metal cation impurities in the natural ATP materials without destroying its initial layered-chain structure through the ion-exchange procedure, accompanied with an obvious enrichment of Brønsted acid and Lewis acid sites. The self-defense effects embodied that both ion-exchanged Ti octahedral centers and abundant Si-OH sites in the Ti-ion-exchange-modified ATP could effectively anchor alkali metals via coordinate bonding or ion-exchange process, which induced alkali metals to be immobilized by the Ti-ion-exchange-modified ATP carrier rather than impair active species. Under this special protection of self-defense effects, Ti-ion-exchange-modified ATP supported catalysts still retained plentiful acidic sites and superior redox ability even after alkali metal poisoning, giving rise to the maintenance of sufficient NHx and NOx adsorption and the subsequent efficient reaction, which in turn resulted in high NOx catalytic reduction capacity of the catalyst. The strategy provided new inspiration for the development of novel and efficient selective catalytic reduction of NOx with NH3 (NH3-SCR) catalysts with high alkali resistance.

Efficient NOx Abatement over Alkali-Resistant Catalysts via Constructing Durable Dimeric VOx Species.

The presence of alkali metals in flue gas is still an obstacle to the practical application of catalysts for selective catalytic reduction (SCR) of NOx by NH3. Polymeric vanadyl species play an essential role in ensuring the effective NOx abatement for NH3-SCR. However, polymeric vanadyl would be conventionally deactivated by the poison of alkali metals such as potassium, and it still remains a great challenge to construct robust and stable vanadyl species. Here, it was demonstrated that a more durable dimeric VOx active site could be constructed with the assistance of triethylamine, thereby achieving alkali-resistant NOx abatement. Due to the rational construction of polymerization structures, the obtained TiO2-supported cerium vanadate catalyst featured more stable dimeric VOx species and the active sites could survive even after the poisoning of alkali metal. Moreover, the depolymerization of VOx was suppressed endowing the catalysts with more Brønsted and Lewis acid sites after the poisoning of alkali metal, which ensured the efficient NOx reduction. This work unraveled the effects of alkali metal on the polymerization state of active species and opens up a way to develop low-temperature alkali-resistant catalysts for NOx abatement.

Synergistic Catalytic Elimination of NOx and Chlorinated Organics: Cooperation of Acid Sites.

The synergistic catalytic removal of NOx and chlorinated volatile organic compounds under low temperatures is still a big challenge. Generally, degradation of chlorinated organics demands sufficient redox ability, which leads to low N2 selectivity in the selective catalytic reduction of NOx by NH3 (NH3-SCR). Herein, mediating acid sites via introducing the CePO4 component into MnO2/TiO2 NH3-SCR catalysts was found to be an effective approach for promoting chlorobenzene degradation. The observation of in situ diffuse reflectance infrared Fourier transform (in situ DRIFT) and Raman spectra reflected that the Lewis acid sites over CePO4 promoted the nucleophilic substitution process of chlorobenzene over MnO2 by weakening the bond between Cl and benzene ring. Meanwhile, MnO2 provided adequate Brønsted acid sites and redox sites. Under the cooperation of Lewis and Brønsted acid sites, relying on the rational redox ability, chlorobenzene degradation was promoted with synergistically improved NH3-SCR activity and selectivity. This work offers a distinct pathway for promoting the combination of chlorobenzene catalytic oxidation and NH3-SCR, and is expected to provide a novel strategy for synergistic catalytic elimination of NOx and chlorinated volatile organic compounds.

SO2-Induced Alkali Resistance of FeVO4/TiO2 Catalysts for NOx Reduction.

Selective catalytic reduction of nitrogen oxides with ammonia (NH3-SCR) is an efficient NOx abatement strategy, but deNOx catalysts suffer from serious deactivation due to the coexistence of multiple poisoning substances such as K, SO2, etc. in the flue gas. It is essential to understand the interaction among various poisons and their effects on NOx abatement. Here, we unexpectedly identified the K migration behavior induced by SO2 over K-poisoned FeVO4/TiO2 catalysts, which led to alkali-poisoning buffering and activity recovery. It has been demonstrated that the K would occupy both redox and acidic sites, which severely reduced the reactivity of FeVO4/TiO2 catalysts. After the sulfuration of the K-poisoned catalyst, SO2 preferred to be combined with the surface K2O, lengthened the K-OFe and K-OV, and thus released the active sites poisoned by K2O, thereby preserving an increase in the activity. As a result, for the K-poisoned catalyst, the conversion of NOx increased from 21 to 97% at 270 °C after the sulfuration process. This work contributes to the understanding of the specific interaction between alkali metals and SO2 on deNOx catalysts and provides a novel strategy for the adaptive use of one poisoning substance to counter another for practical NOx reduction.

Efficient catalytic combustion of toluene at low temperature by tailoring surficial Pt0 and interfacial Pt-Al(OH)x species.

Exploring highly efficient and low-cost supported Pt catalysts is attractive for the application of volatile organic compounds (VOCs) combustion. Herein, efficient catalytic combustion of toluene at low temperature over Pt/γ-Al2O3 catalysts has been demonstrated by tailoring active Pt species spatially. Pt/γ-Al2O3 catalyst with low Pt-content (0.26 wt%) containing both interfacial Pt-Al(OH)x and surficial metallic Pt (Pt0) species exhibited super activity and water-resistant stability for toluene oxidation. The strong metal-support interaction located at the Al-OH-Pt interfaces elongated the Pt-O bond and contributed to the oxidation of toluene. Meanwhile, the OH group at the Al-OH-Pt interfaces had the strongest adsorption and activation capability for toluene and the derived intermediate species were subsequently oxidized by oxygen species activated by surficial Pt0 to yield carbon dioxide and water. This work initiated an inspiring sight to the design of active Pt species for the VOCs combustion.

Boosting Toluene Combustion by Engineering Co-O Strength in Cobalt Oxide Catalysts.

Exploring active and low-cost transition metal oxides (TMOs) based catalysts for volatile organic compounds (VOCs) abatement is vital for air pollution control technologies. Since 18 oxygen atoms are required for the complete mineralization of a toluene molecule, the participation of a large amount of active oxygen is a key requirement for the catalytic oxidation of toluene. Here, toluene degradation was improved by weakening the Co-O bond strength on the surface of cobalt oxide, so as to increase the amount of active oxygen species, while maintaining the high stability of the catalyst for toluene combustion. The bond strength of Co-O and the amount of surface active O2 was regulated by tuning the pyrolysis temperature. The catalyst's redox ability and surface oxygen species activity are improved due to the weakening of the Co-O bond strength. It has been demonstrated that active oxygen plays a crucial role in boosting toluene combustion by engineering Co-O strength in cobalt oxide catalysts. This work provides a new understanding of the exploration and development of high-performance TMO catalysts for VOCs abatement.

Fabrication of Pd3@Beta for catalytic combustion of VOCs by efficient Pd3 cluster and seed-directed hydrothermal syntheses.

Subnanometric Pd clusters confined within zeolite crystals was fabricated using zeolitic seeds with premade [Pd3Cl(PPh2)2(PPh3)3]+ clusters under hydrothermal conditions. Characterization of the Pd3@Beta catalysts indicate that the Pd clusters confined in the channels of Beta zeolite exhibit better dispersion and stronger interaction with the zeolite support, leading to stabilized Pd species after heat treatment by high temperature. In the model reaction of toluene combustion, the Pd3@Beta outperforms both zeolite-supported Pd nanoparticles prepared by conventional impregnation of Pd3/Beta and Pd/Beta. Temperatures for achieving toluene conversion of 5%, 50% and 98% of Pd3@Beta are 136, 169 and 187 °C at SV = 60 000 mL g-1 h-1, respectively. Pd3@Beta could also maintain the catalytic reaction for more than 100 h at 230 °C without losing its activity, an important issue for practical applications. The metal-containing zeolitic seed directed synthesis of metal clusters inside zeolites endows the catalysts with excellent catalytic activity and high metal stability, thus providing potential avenues for the development of metal-encapsulated catalysts for VOCs removal.

SO2-Tolerant Selective Catalytic Reduction of NO x over Meso-TiO2@Fe2O3@Al2O3 Metal-Based Monolith Catalysts.

It is an intractable issue to improve the low-temperature SO2-tolerant selective catalytic reduction (SCR) of NO x with NH3 because deposited sulfates are difficult to decompose below 300 °C. Herein, we established a low-temperature self-prevention mechanism of mesoporous-TiO2@Fe2O3 core-shell composites against sulfate deposition using experiments and density functional theory. The mesoporous TiO2-shell effectively restrained the deposition of FeSO4 and NH4HSO4 because of weak SO2 adsorption and promoted NH4HSO4 decomposition on the mesoporous-TiO2. The electron transfer at the Fe2O3 (core)-TiO2 (shell) interface accelerated the redox cycle, launching the "Fast SCR" reaction, which broadened the low-temperature window. Engineered from the nano- to macro-scale, we achieved one-pot self-installation of mesoporous-TiO2@Fe2O3 composites on the self-tailored AlOOH@Al-mesh monoliths. After the thermal treatment, the mesoporous-TiO2@Fe2O3@Al2O3 monolith catalyst delivered a broad window of 220-420 °C with NO conversion above 90% and had superior SO2 tolerance at 260 °C. The effective heat removal of Al-mesh monolithcatalysts restrained NH3 oxidation to NO and N2O while suppressing the decomposition of NH4NO3 to N2O, and this led to much better high-temperature activity and N2 selectivity. This work supplies a new point for the development of low-temperature SO2-tolerant monolithic SCR catalysts with high N2 selectivity, which is of great significance for both academic interests and practical applications.

NrF2/ARE and NF-κB pathway regulation may be the mechanism for lutein inhibition of human breast cancer cell.

AIM: Though lutein can inhibit cancer cell proliferation via alleviating oxidative injury, the molecular mechanisms of lutein involvement in the NrF2/antioxidant response element (ARE) and NF-κB pathways remain poorly understood. MATERIALS & METHODS: MTT, flow cytometry, quantitative real-time PCR (qRT-PCR) and western blot assays were performed. RESULTS: After treatment with lutein, breast cancer cell proliferation was significantly decreased in a dose-dependent manner. Lutein induced nuclear translocation and protein expression of NrF2, improved the expression of cellular antioxidant enzymes and attenuated reactive oxygen species levels. Moreover, lutein treatment decreased NF-κB signaling pathway related NF-κB p65 protein expression. CONCLUSION: The effect of lutein antiproliferation was mediated by activation of the NrF2/ARE pathway, and blocking of the NF-κB signaling pathway.

[Berberine inhibits cardiac fibrosis of diabetic rats].

Objective To explore the effect of berberine on cardiac fibrosis of diabetic rats by observing the expressions of serum transforming growth factor-ß1 (TGF-ß1), connective tissue growth factor (CTGF) , collagen type 1 (Col1) and collagen type 3 (Col3) in myocardial tissues of diabetic rats after berberine treatment. Methods The diabetic model was induced by intraperitoneal injection of streptococci (STZ). Forty-three diabetic rats were randomly divided into diabetic model group (n=9), berberine treated groups of different doses [50, 100, 150 mg/(kg.d), gavage administration for 12 weeks; n=9, 9, 8 respectively], and metformin group as positive control (n=8); other 8 normal rats served as a negative control group. After the last administration, fasting blood glucose, left ventricular systolic pressure (LVSP) and left ventricular end diastolic pressure (LVEDP) were measured; rats' heart were taken to calculate the heart mass index (HMI); ELISA was used to detect the serum levels of TGF-ß1 and CTGF; collagenous fibers in cardiac tissues were tested by Masson staining; collagen volume fraction (CVF) was measured by image analysis; Col1 and Col3 in cardiac tissues were determined by Western blotting. Results Compared with the normal control group, the fasting blood glucose, LVSP, LVEDP absolute value, HMI, the degree of cardiac fibrosis, the expressions of TGF-ß1, CTGF, Col1 and Col3 significantly increased in the model group. All indexes mentioned above were reduced obviously in berberine treated groups of 100 and 150 mg/(kg.d). Conclusion Berberine improves cardiac fibrosis in diabetic rats through down-regulating the expressions of TGF-ß1 and CTGF and reducing the synthesis and deposition of Col1 and Col3.

[Tripterygium wilfordii polyglycoside suppresses inflammatory cytokine expression in rats with diabetic nephropathy].

OBJECTIVE: To investigate the effects of Tripterygium wilfordii polyglycoside (TWP) on the expressions of nuclear factor kappa B (NF-κB), chemokine (C-C motif) ligand 5 (CCL5), tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6) and other inflammatory factors in diabetic nephropathy (DN) rats. METHODS: The diabetic model was induced by a single intraperitoneal injection of streptozotocin (STZ). The rats were randomly divided into three groups: normal control group, diabetic model group and TWP (1.8 g/kg.d) treatment group. Kidney index, blood glucose (BG), glycosylated hemoglobin (HbA1c), creatinine (Scr), blood urea nitrogen (BUN) and other biochemical criterions were measured after eight-week treatment. The concentration of high sensitive C-reactive protein (hs-CRP) in serum and IL-6, TNF-α, CCL5 in kidney homogenate were detected by ELISA. The pathological changes of kidney were observed by HE staining and the expression of NF-κB in kidney was tested by immunohistochemistry. RESULTS: Compared with the model group, TWP improved evidently the general situation of rats. The levels of BG, HbA1c, kidney index, Scr and BUN were reduced significantly (P<0.01) and the body mass was elevated significantly (P<0.01). Additionally, the content of hs-CRP in serum, the levels of IL-6, TNF-α, and CCL5 in kidney homogenate and the expression of NF-κB in kidney decreased obviously in TWP group compared with the model group(P<0.01). The pathological changes of kidney were also relieved by TWP treatment. CONCLUSION: TWP treatment could reduce the expressions of inflammation cytokines in serum and kidney and relieve the nephropathy in diabetic rats.

[Inhibitory effect of total glucosides of paeonia on the NF-κB/p65 protein expression in paws of RA rats].

AIM: To explore effects of total glucosides of paeonia (TGP)on the NF-κB/p65 protein expression in paws of rheumatoid arthritis (RA) rats, and the contents of serum TNF-α, IL-1ß and IL-10 in RA rats serum. METHODS: Type II collagen-induced arthritis model in SD rats was established. The expression of NF-κB/p65 proteins in rat, s paw tissues was detected by immunohistochemical staining. The contents of serum TNF-α, IL-1ß and IL-10 in RA rats were detected by ELISA. RESULTS: TGP could down-regulate the expression of NF-κB/ p65 protein and contents of TNF-α, IL-1ß and IL-10 in RA rats. CONCLUSION: The inhibitory effect of TGP on anti-inflammation maybe related to decreasing the expression of NF-κB/p65 protein and suppressing the production of TNF-α and IL-1ß in RA rats.