CeO2-supported noble metal catalysts show great application potential in the catalytic oxidation of volatile organic compounds and hazardous organic wastewater. In this paper, an efficient Ru/CeO2 catalyst is developed by combining the oxygen affinity of noble metals and the redox of supports for catalytic wet air oxidation (CWAO) of reconstituted tobacco wastewater. First, what factors affect the catalytic performance are studied by investigating the effect of supports (C, TiO2, Al2O3, and CeO2) and noble metals (Pt, Pd, and Ru) on the activity. Second, the catalytic performance of Ru/CeO2 is further enhanced by tuning the morphology of CeO2 supports. The results indicate that the Ru/CeO2-R (rod-like) catalyst is highly active and can reach a high TOC conversion of 97.6% at 220 °C in 1 h. In contrast, the TOC conversions of Ru/CeO2-MOF, Ru/CeO2-NP (nanoparticle), and Ru/CeO2-C (cube-like) are 93.3, 77.9, and 68.2%, respectively. Ru/CeO2-R also presented good stability. The TOC conversion can be maintained at approximately 85% in four consecutive cycles. The characterization results indicate that better Ru dispersion, higher Ce3+ content, more surface reactive oxygen species, electron transfer between Ru and CeO2-R, and oxygen transfer from CeO2-R to Ru are the main reasons for the best catalytic performance of the Ru/CeO2-R catalyst.

In this study, we utilized a sol-gel method to prepare Ni-HPW/SiO2 catalysts with varying citric acid (CA):Ni molar ratios ranging from 0 to 5.0. The catalysts demonstrated different levels of activity in the hydrogenation of ethylbenzene, which correlated to their respective CA:Ni ratios. Introducing citric acid in the preparation process of nickel-based catalysts yielded mesopore formation and reduced NiO particle size, producing a more uniform NiO dispersion on SiO2, which was confirmed by BET, XRD, and TEM analyses. The results of H2-TPR, H2-TPD, NH3-TPD, and Py-IR analyses suggested that the addition of citric acid augmented the interaction between phosphotungstic acid (HPW), Ni species, and SiO2. Citric acid improved Ni species and HPW dispersion, fostering increased HPW-Ni species formation. This, in turn, generated additional electron-deficient Ni ions, stemming from semi-reduced HPW-Ni species, which acted as Lewis acid sites, enhancing Ni+ species effectiveness in activating aromatic rings. The better-dispersed, non-HPW-bound NiO, which, upon complete reduction to Ni, led to a substantial rise in H2 bond cleavage, thereby facilitating more hydrogen spillover. Overall, the infusion of citric acid into fabricating Ni-HPW/SiO2 catalysts sparked a significant surge in their aromatic hydrogenation ability.

The potential for synthesizing cyclohexylbenzene through one-step hydroalkylation of benzene is significant, but the selectivity is hindered by the deep hydrogenation of benzene to cyclohexane. In this study, Ni-containing phyllosilicate (Ni PS) was incorporated between Ni nanoparticles and zeolite (HY) using the deposition–precipitation technique, thereby creating Ni/Ni PS/HY. A conventional Ni/HY catalyst was also prepared using the impregnation method for comparison. Ni/Ni PS/HY demonstrates outstanding catalytic performance even at a low temperature of 130 °C and a high WHSV of up to 42.21 h−1, achieving a benzene conversion of ∼25 % and a cyclohexylbenzene selectivity of ∼85 %, which remained stable for 300 h. By contrast, the conventional Ni/HY catalyst yields a mere 2.5 % benzene conversion under identical conditions. Comprehensive characterizations and density functional theory (DFT) calculations reveal that Ni PS plays crucial roles in the hydroalkylation of benzene to cyclohexylbenzene. The formation of Ni PS leads to high Ni dispersion, generating more active sites for hydrogenation. Concurrently, the robust interaction between Ni PS and Ni reduces the reactivity of adsorbed H species, impeding the deep hydrogenation of benzene to cyclohexane, while still effectively allowing the formation of cyclohexene. After being adsorbed by the strong acid sites within Ni PS, the intermediate cyclohexene can be smoothly transported through the mesoporous structure of Ni PS to HY for alkylation. All these factors culminate in the exceptional catalytic performance of Ni/Ni-PS/HY.

The hydroisomerization of n-hexadecane was investigated using bifunctional platinum catalysts supported on EU-1, ZSM-48, ZSM-23, ZSM-22, and ZSM-12 zeolites. These one-dimensional microporous zeolites were synthesized at 160 degree celsius with an Si/Al molar ratio of 60, and 0.5 wt% Pt was loaded onto them using the impregnation method. The findings indicate that Br & oslash;nsted acidity predominantly influences the conversion to n-hexadecane over 10 membered ring zeolites. Additionally, ZSM-12, characterized by a 12-ring channel, exhibits preferential activity in this regard. The apparent activation energy for the reactions increased from 81 kJ/mol (Pt/ZSM-23) to 134 kJ/mol (Pt/ZSM-48) across all tested catalysts. Pt/ZSM-22 demonstrated high selectivity towards mono-branched isomers, whereas Pt/ZSM-12 favored the formation of multi-branched isomers. The isomer selectivity trend was Pt/ZSM-22 > Pt/ZSM-12 > Pt/EU-1 > Pt/ZSM-48 > Pt/ZSM-23. Moreover, TG analysis of spent catalysts unveiled that coke formation on these zeolites was chiefly influenced by zeolite channel structure and Br & oslash;nsted acid content. The average coke selectivity followed this order: Pt/EU-1 > Pt/ZSM-12 > Pt/ZSM-48 > Pt/ZSM-22 > Pt/ZSM-23.

The potential for synthesizing cyclohexylbenzene through one-step hydroalkylation of benzene is significant, but the selectivity is hindered by the deep hydrogenation of benzene to cyclohexane. In this study, Ni-containing phyllosilicate (Ni PS) was incorporated between Ni nanoparticles and zeolite (HY) using the deposition-precipitation technique, thereby creating Ni/Ni PS/HY. A conventional Ni/HY catalyst was also prepared using the impregnation method for comparison. Ni/Ni PS/HY demonstrates outstanding catalytic performance even at a low temperature of 130 degrees C and a high WHSV of up to 42.21 h-1, achieving a benzene conversion of -25 % and a cyclohexylbenzene selectivity of -85 %, which remained stable for 300 h. By contrast, the conventional Ni/HY catalyst yields a mere 2.5 % benzene conversion under identical conditions. Comprehensive characterizations and density functional theory (DFT) calculations reveal that Ni PS plays crucial roles in the hydroalkylation of benzene to cyclohexylbenzene. The formation of Ni PS leads to high Ni dispersion, generating more active sites for hydrogenation. Concurrently, the robust interaction between Ni PS and Ni reduces the reactivity of adsorbed H species, impeding the deep hydrogenation of benzene to cyclohexane, while still effectively allowing the formation of cyclohexene. After being adsorbed by the strong acid sites within Ni PS, the intermediate cyclohexene can be smoothly transported through the mesoporous structure of Ni PS to HY for alkylation. All these factors culminate in the exceptional catalytic performance of Ni/Ni-PS/HY.

Hydrogen production from formaldehyde aqueous solution at room temperature shows a unique advantage regarding the bi-functional reaction route. MnO2 was reported to be an active catalytic material for this process, especially after coating with carbon composite for improved active site distribution. Here, we unravel that the conversion of formaldehyde can be treated as two tandem half-reactions: the oxidative dehydrogenation (ODH) of formaldehyde and the hydrogen evolution reaction (HER). 13-MnO2 in a physical mixture with carbon (i.e., XC-72R, graphene) enhances both formaldehyde conversion (from 13% to 19.5%) and hydrogen productivity (from 22.35 mu mol mg-1 h-1 to 33.86 mu mol mg-1 h-1) by a synergistic effect of the phase separation catalyst in terms of electron redistribution and transport over the active sites. The catalyst examination supported by DFT calculation shows relatively low activation energy and band gap of 13-MnO2 + C with a density of states spanning the Fermi level. The discovery of this novel synergistic catalytic effect: a phase separation catalyst with cooperative enhancement, provides new insight into the area of tandem catalysis.

Glycerol is a main by-product of biodiesel production, and its further processing is essential for the biorefinery. In this paper, a highly active and stable catalyst for the catalytic dehydration of glycerol to acetol is obtained by modifying a Cu-Zr (ZrO2 supported Cu) catalyst with Y2O3 using a co-precipitation method. It is found that the addition of Y2O3 effectively enhances the catalytic performance of Cu-Zr. Cu-Zr reaches the highest selectivity (82.4%) to acetol at 24 h. However, the selectivity decreases to 70.1% at 36 h. The conversion also decreases from 99.2 to 91.1%. Cu-Zr-Y exhibits very high activity and very good stability. During a 250 h reaction, no deactivation is observed, and the conversion and selectivity remains ~100% and ~85%, respectively. The catalysts are characterized by XRD, TEM, H2-TPR, and NH3-TPD. The results reveal that Y2O3 not only improves the dispersion of Cu and the acidity of the catalyst but also restrains the agglomeration of Cu particles and assists retaining the main structure of support under reaction conditions. The high dispersion, high acidity content, and stable structure contributes to the excellent catalytic performance of Cu-Zr-Y.

With the rapid growth of population and industrial production, wastewater pollution has become a major environmental issue. Wastewater pollution also poses a threat to water resources and human health. Catalytic wet-air oxidation (CWAO) is one of the most economical and environmentally friendly technologies, especially for the treatment of toxic and non-biodegradable pollutants in wastewater. Various heterogeneous catalysts have been reported for use in wastewater treatment; however, most of these catalysts are effective only under high temperatures and high pressures. The increasing demand for the removal of wastewater pollutants necessitates the development of low-temperature, high-efficiency catalysts for CWAO technology. To achieve this, the ability of the catalyst to activate O2 and transfer active oxygen species plays a key role in determining the catalytic performance. In this review, we summarize recent advances in various noble and non-noble metal catalysts, oxide catalysts and carbon catalysts for CWAO reactions, focusing on the positive effect of O2 activation and transfer on catalytic performance. We also propose future directions for developing novel CWAO catalysts by optimizing the catalyst's ability to activate O2 and transfer active oxygen species.

In diesel adsorption desulfurization, the coordination bonding between the adsorbent and sulfur compounds is interfered by aromatic compounds in diesel. Transition metal cation exchanged zeolites Y has exhibits exceptional anti-interference performance. In this work, the influence of electron configuration on coordination bonding is explored, specifically between the adsorbent and substrate, using both experimental and DFT theoretical methods. Initially, NiY, CuY and ZnY were synthesized and evaluated for their desulfurization performance in model solution (sulfur content: 25 ppmw dibenzothiophene [DBT]) with two toluene concentrations (1 w% and 3 w%). It is found that CuY showed the highest performance with retention rate at 70.2 %. Subsequently, DFT calculations revealed the binding energy between Cu(II) and DBT was -2.71 eV, higher than Ni(II) and Zn (II), and that between Cu(II) and toluene was -1.75 eV, lower than Ni(II) and Zn(II), indicating that the highest binding energy difference was responsible for the best adsorption capability. Apart from these, wave function analysis show the electron configuration between Cu(II) and DBT had the highest binding energy difference. Finally, the impact of electron configuration on adsorption performance is further investigated by modulating the electron configuration of Ni(II) to enhance/suppress its adsorption capability. According to the findings of this study, tuning the electron configuration is an effective strategy to develop materials in adsorptive desulfurization particularly for extra low sulfur content.

ZSM-22 zeolites were synthesized using different structure-directingagents (SDAs) with varying alkyl chain lengths, including n-alkyldiamines (DAB, DAH, DAO, and DAD) and lauryl amine(LA). The characteristics of the resulting samples (denoted as "Z-SDA")revealed that optimal elongation of SDA alkyl chains brought abouta decrease in crystallization time while retaining ZSM-22 crystalphase stability. The morphology and acidity of the samples variedas the alkyl chain length of the SDAs increased. The average crystallength ranged from 13 & mu;m to 250 nm, and the total acid contentshowed a downward trend, while each sample possessed nonlinear acidsite distributions. Additionally, ZSM-22-supported Pt catalysts wereobtained and probed using the n-hexadecane hydroisomerizationprocess. It was found that the activity and i-hexadecaneselectivity gradually increased with the alkyl chain length of theSDAs (C-4-C-10). Notably, Pt/Z-DAD achieved>70% yield under specific reaction conditions, which could be attributedto the abundant mesopore network and high proportion of weak Bronstedacid site distributions.

Abstract The stability of catalysts perhaps is the most important issue for catalysis whatever fundamental or application. This study evaluates the stability of MnOx-CeO2 catalysts in the oxidation of ethyl acetate by comparing the performance of fresh catalysts with those treated under high-temperature hydrothermal conditions (750 ℃ and 5% steam for 12 h). Three different methods, namely redox-precipitation (RH), co-precipitation (CP), and impregnation (IP), were used to synthesize the catalysts and adjust the Mn-Ce dispersion. The activity difference between the fresh and treated catalysts decreased in the following order: RH-MnCe > CP-MnCe > IP-MnCe. Based on detailed characterizations and density functional theory calculations, the molecular dispersion of MnCeOx in RH-MnCe is key to ensuring the collapse resistance of Ce-doped Mn3O4, which yields the highest activity during ethyl acetate oxidation. This finding is supported by experiments conducted on RH-MnCe with different Mn/Ce ratios. Although the introduction of Ce can enhance the stability of Mn3O4, it must be carefully controlled at a moderate level to enable recycling between MnO2/Mn3O4.

详细研究了层状双金属氧化物(LDO)制备方法对Pt/LDO催化剂进行催化湿式氧化(CWAO)处理甲醛废水性能的影响,并对制备的催化剂进行X射线衍射、透射电镜、N2 物理吸-脱附、H2 程序升温还原和X射线光电子能谱等表征.催化剂评价结果表明:在室温和低Pt负载量(质量分数 0.25%)的条件下,与Pt/LDO(P)(共沉淀法制备的LDO)相比,Pt/LDO(H)(水热法制备的LDO)催化剂具有更为优异的CWAO 处理甲醛废水的催化性能.在室温(30℃)下反应 5h,Pt/LDO(H)可将甲醛完全转化,且能将 84.1%的甲醛完全氧化为CO2;而在相同条件下,Pt/LDO(P)只能转化 63.8%的甲醛,且仅有 57.9%的甲醛被完全氧化为CO2.Pt/LDO(H)催化剂还具有良好的稳定性,在连续测试的 5 次反应内,保持高的甲醛转化率(约 100%)和总有机碳转化率(约 83%).表征结果显示,Pt/LDO(H)催化剂具有高的Pt分散性、强的金属-载体电子相互作用、丰富的表面氧物种、强的氧化能力和良好的抗流失性能,这是其具有优良催化性能的主要原因.

Catalytic wet air oxidation (CWAO) is a promising process for degrading phenol in wastewater to CO2 and H2O. To achieve an active and stable Pt catalyst working at lower temperature, efficient catalysts are here developed by building a Pt-M (M=Pb, Cu) alloy structure where Pt is mainly in the form of Pt0 while M is mainly in the form of M2+. Firstly, carbon supported Pt-Pb/XC-72R and Pt-Pb/EC-300 catalysts are prepared for CWAO of phenol wastewater. It is found that Pt-Pb/XC-72R is highly active and stable for CWAO of phenol even at 100 degrees C. The initial TOC conversion is 91.1% and can be maintained higher than 75% in five consecutive cycles. Contrarily, PtPb/EC-300 rapidly deactivates and TOC conversion decreased from 91.2% to 47.1% after five cycles. The characterization results indicate that two Pt-Pb alloy catalysts contained comparably high Pt0 concentration, which is responsible for the high activity. However, the Pb2+ concentration of Pt-Pb/XC-72R is much higher than that of Pt-Pb/EC-300, and higher Pb2+ concentration favors surface oxidation and keeps Pt0 from being oxidized during CWAO process, thus enhancing stability. For Pt-Pb/EC-300, both Pt0 and Pb0 are oxidized during the reaction, resulting in deactivation. To avoid using Pb in environmental considerations, the Pt-Pb is then replaced by Pt-Cu nanoparticles, where high catalytic activity and stability are maintained. More importantly, increasing Cu2+ can further enhance the catalytic performance. Tuning the second metal chemical state of Pt-based bimetallic alloy can be an effective approach to develop new catalysts for CWAO technology.

CeO2 plays an important role in heterogeneous catalysis,and its performance is highly dependent on the oxygen vacancies and surface defects,which can be easily tuned by manipulating the particle dimensions and morphology.In this article,we report a facile strategy to synthesize a new type of CeO2 with modified surface property which can improve its ability to active oxygen.The obtained ball-type 3D self-assemble CeO2(M-CeO2)is composed of large amounts of small 1D crystals which are strongly connected with each other.Detailed characterizations confirm its morphology,particle size and improved reduc-ibility with abundant fraction of Ce3+and more surface active oxygen when compared with CeO2-nanorods and CeO2-nanocubes.In the catalytic wet air oxidation(CWAO)of N,N-dimethylformamide,the total organic carbon(TOC)and total nitrogen(TN)conversion of M-CeO2 at 180 ℃ in 3 h are 68％and 46％,respectively,which are higher than that of CeO2-nanorods and CeO2-nanocubes.Besides,M-CeO2 pre-sents the lowest activation energy,which is related to its modified surface property.The good stability with consecutive four reactions of M-CeO2 in catalytic reactions suggests its potential application in CWAO processes for industrial wastewater treatment.

The study fabricated ZSM-22 zeolites with Ce/Al molar ratios ranging from 0 to 1, which were subsequently loaded with Pt to perform n-hexadecane hydroisomerization. Various methods, such as XRD, 29Si NMR, FTIR, UV-Vis, XPS, and H2-TPR, confirmed the direct evidence of Ce incorporation into the zeolite framework, and the framework Ce content was of a volcanic nature. Furthermore, the study observed successful manipulation of textural and acidity properties of the samples through variation of the Ce content, as shown by N2-physisorption, NH3-TPD, and Py-IR. Increasing Ce content led to retardation of micropore diffusion due to lower micropore volume and surface area, as well as an increase in the distribution of weak Bronsted acid sites, which suppressed outside-of-pore cracking reactions. These changes rendered improved i-hexadecane selectivity and catalyst stability for Pt/ZSM-22. At a Ce/Al molar ratio of 0.5 with a WHSV of 12 h-1, the high selectivity to monobranched isomers resulted in a yield exceeding 75 wt%.

In electrochemical alcohol oxidation reactions catalyzed by supported Pt-based nanoparticles, the catalytic performance is highly correlated with the electron density accumulated over the metal surface. This has been exemplified by a highly electronegative nature of Pt, affecting the catalytic performance by accumulating electrons generated over the oxidative reaction over the Pt surface. It was found that by alloying Cu (Cuσ+) to Pt makes the catalyst more active and robust due to the redox property of Cu(II)/Cu(0). Here, we show that oxidative pretreatment of the carbon support XC-72R with HNO3 or H2O2 can further boost the catalysis in alcohol oxidation. This is mainly explained by the enriched O-containing functional groups introduced to the support, which stabilize Cu(II) in the bimetallic Pt-Cu nanoparticle and enhance the hydrophilic wettability to adsorb more reactant molecules and hydroxide over the catalyst surface. The proposed catalytic system is applicable to a variety of substrates, i.e. methanol, ethanol, isopropanol and sorbitol. Our work signifies the importance of the support-modification in tuning the redox cycle over a bimetallic nanoparticle and thus enhancing the electrocatalytic oxidation reactions.

Correction for ‘Understanding the suppressive role of catalytically active Pt–TiO 2 interfacial sites of supported metal catalysts towards complete oxidation of toluene’ by Hanlei Sun et al. , J. Mater. Chem. A , 2022, 10 , 25633–25643, https://doi.org/10.1039/D2TA07555E.

Stereoselective hydrogenation of α‐pinene over heterogenous catalysts under solvent‐free conditions is promising for biomass conversion but challenging. Herein, we prepared the Ru‐NiO/Hβ catalysts using chemical reduction and galvanic replacement methods. With the increase of Ni content, the selectivity of cis‐pinane was significantly improved. A high conversion of 100 % and a high cis‐pinane selectivity of 98 % were achieved after 4 h reaction at 80 °C. It has been verified that the addition of Ni can adjust the ratio of Brønsted and Lewis acid, regulate the hydrogen spillover between Ru and support, change the adsorption site of substrate and form steric hindrance effect. All these contribute to the better selectivity of the catalyst. In addition, catalysts presented good stability in the 900 h test.

Phenol is one of the major hazardous organic compounds in industrial wastewater. In this work, a highly active Pt/TiO2 catalyst for catalytic wet air oxidation (CWAO) of phenol was obtained by supporting pre-synthesized Pt on TiO2. During the followed hydrogen reduction, strong hydrogen spillover occurred without the migration of TiO2 onto Pt. The reduced support then enhanced the electron transfer from TiO2 to Pt, increasing the percentage of partially negative Pt (Pt delta-), which has been confirmed by XPS. The strong EMSI made the obtained catalyst far more active than Pt/TiO2 prepared by impregnation method. The electron-enriched Pt/TiO2 achieved total organic carbon (TOC) conversion of 88.8% and TOF 149h(-1) at 100 degrees C and 2 MPa O-2, while conventional Pt/TiO2 gave TOC conversion of 39.5% and TOF 41 h(-1)- for CWAO of phenol. Our work indicates that the enhancement of EMSI between metal and support can be an effective approach to develop highly active catalysts for phenol treatment.