Zeolite-supported Catalysts Research Articles

Paving the way to transfer hydrogenation of CO2 with bio-derived glycerol over Ni supported zeolite catalysts

The CO2 transfer hydrogenation with bio-glycerol over a Ni-zeolite was systematically studied to produce formic and lactic acids. The alkaline hydrothermal reactions without a catalyst and with Ni-zeolite heterogeneous catalyst were explored, focusing on the effects of base types and concentrations, reaction atmosphere and temperature. In alkaline hydrothermal reactions without catalyst, NaOH demonstrated superior performance at 1 M. A Ni/NaZSM-5 catalyst showed astounding performance giving 9.3 mol-L−1-g−1 lactic acid and 6.5 mol-L−1-g−1 formic acid at 250 °C after 2 h. Notably, the zeolite showed resistance to the highly basic conditions of the reaction medium. For the first time, CO2 conversion in aqueous phase was reported addressing the complexity of CO2 solubility. A reaction network was proposed including the diverse glycerol transformations not yet studied for this system. Overall, this study sheds light on the understanding of this complex reaction system and the potential of Ni-supported zeolites for sustainable CO2 utilisation.

Selective cracking of light cycle oil to monoaromatics over non-noble bifunctional zeolite-supported Ni and NiW catalysts

The utilization of light cycle oil (LCO) for producing monoaromatics is investigated using bifunctional Ni and NiW catalysts supported on four different zeolites at atmospheric pressure without using external H2. The order of BTX yield for various feed compositions (2-methylnaphthalene, 2-methylnaphthalene + 9-methylanthracene, LCO) is: NiW/Beta > NiW/Y > Ni/Beta > NiW/Mordenite > Ni/Y > NiW/Mix > Ni/Mordenite > Ni/Mix, whereas the coke yield exhibits the reverse trend. The better performance of NiW-based catalysts is explained by the formation of NiW oxide species and their strong interactions with the support, as ascertained through H2-TPR, XPS, and UV-DRS. The higher moderate acidity, optimal balance between medium-strength Brønsted acid sites (BAS) and strong Lewis acid sites (LAS), and the higher hydrogen transfer index (HTI) in NiW-based catalysts, facilitate the selective cracking of LCO, resulting in the desired product yield. This study also establishes a strong correlation between the structural properties of various catalysts (pore diameter, surface area, pore volume, crystallite size) and the performance parameters, thus explaining the superior performance of Beta zeolite-supported catalysts for BTX production. Experiments with NiW/Beta and a physical mixture of W/Beta and Ni/Beta show the synergistic effect due to the co-presence of Ni and W. It is inferred that triaromatics are rapidly transformed to diaromatics, and the conversion of monoaromatics having two rings determines the BTX yield. LCO compounds are found to be the primary source for the formation of monoaromatics, while n-hexadecane (n-HD) is the hydrogen source. Reaction pathways for 2-methylnaphthalene and 9-methylanthracene conversion are presented based on detailed product characterization.

Enhanced Oxidation of p-Toluidine Using Supported Zeolite Nanoparticles.

Supported nanomaterials are becoming increasingly important in many industrial processes because of the need to improve both the efficiency and environmental acceptability of industrial processes. The unique properties of supported nanomaterials have attracted researchers to develop efficient catalytic materials in nanoscale. The extremely small size of the particles maximizes the surface area exposed to the reactant, allowing more reactions to occur. The environmental hazards resulting from the conventional manufacturing procedures for organic fine chemicals and intermediates by classical oxidation catalysis using mineral acids have forced chemical industries to seek less polluting processes. The present study aimed to oxidize p-toluidine by hydrogen peroxide in the presence of magnetite supported on nanocrystalline titanium silicalite-1 (M/NTS) zeolite at ambient temperature. The products detected are 4,4'-dimethylazobenzene as major product and 4,4'-dimethylazoxybenzene as minor product. Good selectivity, low cost, low wastage of materials and enhanced environmental friendliness of heterogeneous magnetite nanoparticle supported zeolite catalysts were observed. The effect of various reaction parameters such as mole ratio, catalyst weight and reusability of catalyst were studied. At the optimum reaction conditions, the oxidation activity of M/NTS catalyst was compared with M/NS catalyst, and it was found that titanium in the framework of M/NTS provided higher activity and selectivity.

Using ammonia solution to fabricate highly active Au/ uncalcined TS‑1 catalyst for gas-phase epoxidation of propylene

Reducing the Au particle size and increasing the number of defective Ti4+ species have been considered effective strategies to boost the catalytic performance of Au–Ti bifunctional catalysts used for propylene epoxidation utilizing H2 and O2. Consequently, the development of an effective method that can simultaneously achieve these goals is of significant scientific and industrial importance. Herein, we demonstrate, for the first time, that the simultaneous immobilization of small Au particles (approximately 1.6 nm) onto uncalcined titanium silicate-1 (i.e., TS-1-B) and facilitation of the formation of defective Ti4+ species can be achieved using a modified deposition–precipitation (DP) method utilizing ammonia solution as the precipitant. The as-synthesized catalyst exhibits a significantly enhanced propylene oxide (PO) formation rate combined with fascinating PO selectivity and hydrogen efficiency, which were better than the reference catalyst prepared via the DP urea (DPU) method and other reported Au/uncalcined TS-1 catalysts. The catalyst structure–performance relationship was established using multiple characterization studies. the ammonia treatment facilitates the hydrolysis of some of the ≡Ti-O-Si≡ bonds into defective Ti4+ species (i.e., Ti(OSi)3OH), which not only provides more active Ti4+ sites but also favors the uniform deposition of Au. This methodology and the insights stated herein may also be applicable for enhancing the dispersion of Au in a variety of zeolite-supported catalysts.

Low-Temperature Catalytic Ozonation of Multitype VOCs over Zeolite-Supported Catalysts.

Volatile organic compounds (VOCs) are an important source of air pollution, harmful to human health and the environment, and important precursors of secondary organic aerosols, O3 and photochemical smog. This study focused on the low-temperature catalytic oxidation and degradation of benzene, dichloroethane, methanethiol, methanol and methylamine by ozone. Benzene was used as a model compound, and a molecular sieve was selected as a catalyst carrier to prepare a series of supported active metal catalysts by impregnation. The effects of ozone on the catalytic oxidation of VOCs and catalysts' activity were studied. Taking benzene as a model compound, low-temperature ozone catalytic oxidation was conducted to explore the influence of the catalyst carrier, the active metal and the precious metal Pt on the catalytic degradation of benzene. The optimal catalyst appeared to be 0.75%Pt-10%Fe/HZSM(200). The catalytic activity and formation of the by-products methylamine, methanethiol, methanol, dichloroethane and benzene over 0.75%Pt-10%Fe/HZSM(200) were investigated. The structure, oxygen vacancy, surface properties and surface acidity of the catalysts were investigated. XRD, TEM, XPS, H2-TPR, EPR, CO2-TPD, BET, C6H6-TPD and Py-IR were combined to establish the correlation between the surface properties of the catalysts and the degradation activity.

Environmental assessment of carbon dioxide methanation process using mixed metal oxide and zeolite-supported catalysts by life cycle assessment methodology

Carbon dioxide methanation process is a well-known carbon dioxide utilization technology, not only on account of its ability to subside carbon dioxide in the atmosphere but also to produce methane, which is of serious industrial significance. Although this process is promising in terms of tackling greenhouse gases and global warming, it can, on the other hand, release toxic emissions into the atmosphere, rivers and soil during the process. At this point, life cycle environmental assessment emerges as a crucial tool to reveal the overall effects of this technology. This paper presents a life cycle assessment case study for carbon dioxide methanation process to evaluate all aspects of its environmental impacts. Different scenarios for this purpose were considered by changing catalyst types, namely, mixed metal oxide and zeolite-supported metal catalysts. The results showed that the toxic wastes formed and emissions released when using the Ni/Al 2 O 3 catalyst were less compared to the other cases. Not only did the change in material type in the catalyst affect the total emissions, but the catalyst conversion and selectivity had an influence on the life cycle impact of the system as well. Various power generation alternatives considering renewable and non-renewable sources were evaluated, while a combination of natural gas and wind turbines for the initial sources of power generation was found to perform better in terms of environmental impact. • CO 2 methanation on Ni/Al 2 O 3 catalyst is more environmentally-friendly. • Using natural gas for CO 2 capture emits fewer pollutants than using coal. • Conversion and selectivity factors can affect LCA results of a reaction-based process. • A mixture of natural gas power plants and wind turbines can reduce environmental impacts. • Perovskite solar cells show toxic effects on climate change and metal depletion.

Physicochemical Features and NH3-SCR Catalytic Performance of Natural Zeolite Modified with Iron—The Effect of Fe Loading

In modern dual-pressure nitric acid plants, the tail gas temperature usually exceeds 300 °C. The NH3-SCR catalyst used in this temperature range must be resistant to thermal deactivation, so commercial vanadium-based systems, such as V2O5-WO3 (MoO3)-TiO2, are most commonly used. However, selectivity of this material significantly decreases above 350 °C due to the increase in the rate of side reactions, such as oxidation of ammonia to NO and formation of N2O. Moreover, vanadium compounds are toxic for the environment. Thus, management of the used catalyst is complicated. One of the alternatives to commercial V2O5-TiO2 catalysts are natural zeolites. These materials are abundant in the environment and are thus relatively cheap and easily accessible. Therefore, the aim of the study was to design a novel iron-modified zeolite catalyst for the reduction of NOx emission from dual-pressure nitric acid plants via NH3-SCR. The aim of the study was to determine the influence of iron loading in the natural zeolite-supported catalyst on its catalytic performance in NOx conversion. The investigated support was firstly formed into pellets and then impregnated with various contents of Fe precursor. Physicochemical characteristics of the catalyst were determined by XRF, XRD, low-temperature N2 sorption, FT-IR, and UV–Vis. The catalytic performance of the catalyst formed into pellets was tested on a laboratory scale within the range of 250–450 °C using tail gases from a pilot nitric acid plant. The results of this study indicated that the presence of various iron species, including natural isolated Fe3+ and the introduced FexOy oligomers, contributed to efficient NOx reduction, especially in the high-temperature range, where the NOx conversion rate exceeded 90%.

A low temperature catalytic combustible gas sensor based on Ru supported zeolite catalyst films

• The zeolite supported noble metal catalysts prepared by wet impregnation method can effectively improve the catalytic activity of combustible gases CO and H 2 . • The catalytic sensor prepared by using noble metal catalyst supported by zeolite as sensitive material has high gas-sensitive response to combustible gases H 2 and CO. • The sensor has good response and linearity to combustible gases, good repeatability, high stability. Catalyst based on Ru loaded HZSM5 zeolite is prepared by a wet impregnation method, which is screen printed onto alumina substrates and serves as sensitive materials for the catalytic combustion sensor. The results show that Ru-HZSM5 catalyst has a high catalytic activity to combustible gases such as hydrogen (H 2 ) and carbon monoxide (CO) at low temperature. However, a poor dispersion of Ru reduces the catalytic activity of the catalyst when the Ru loading is too high. It is due to the pore structure of the sensitive material which facilitates the acquisition of high dispersion characteristics and gas selective regulation. The catalytic sensor based on Ru-HZSM5 also has high selectivity for combustible gases. Due to the low operating temperature, the sensor has a high selectivity for combustible gases and no cross-response to interfering gases such as ammonia (NH 3 ) and volatile organic compound (VOCs). Therefore, the catalytic type gas sensor with low power consumption and good selectivity can be used for monitoring CO, H 2 and other combustible gases. The Ru supported zeolite catalyst was prepared by wet impregnation method, and a catalytic combustion sensor was fabricated by screen printing. The results show that the catalytic activity of the catalyst was closely related to the Ru loading and operating temperature. The response of the catalytic sensor increases linearly with the concentration of the combustible gas. The preparation of Ru supported HZSM5 catalyst by wet impregnation is a very effective technology. The catalytic activity of the sensitive material is significantly promoted by the noble metal Ru highly loading in the catalyst. The response to different concentrations of combustible gas H 2 also proves the loading relationship of Ru on zeolite surface.

Stable Palladium Oxide Clusters Encapsulated in Silicalite-1 for Complete Methane Oxidation

Zeolite-supported metal catalysts are widely employed in a number of chemical processes, and the stability of the catalytically active species is one of the most critical factors determining the reaction performance. A good example is the Pd/zeolite catalyst, which provides high activity for methane oxidation but deactivates rapidly under the reaction conditions due to palladium nanoparticle sintering. Although coating the metals with thin shells of porous materials is a promising strategy to address the sintering of metals, it is still challenging to fix small metal particles completely inside zeolite crystals. Here, using an amine-based ligand to stabilize palladium during the zeolite synthesis, we realize the exclusive encapsulation of highly dispersed palladium oxide clusters (1.8–2.8 nm) in the microporous channels and voids of the nanosized silicalite-1 crystals. The synthesis conditions of the zeolite-supported catalyst influence the encapsulation degree and the size distribution of metal particles. Thanks to the encapsulation effect of small palladium oxide clusters, together with the inherent properties of silicalite-1 such as low acidity, high hydrophobicity, and high hydrothermal stability, the optimized Pd@silicalite-1 catalyst outperforms the traditional Pd-based catalysts prepared by wetness impregnation, exhibiting both high activity and better stability in the lean methane oxidation reaction.

(Invited) Synthesis and Characterizations of Various Van Der Waals Hetero-Nanotubes Based on Single-Walled Carbon Nanotubes

We have successfully realized the synthesis of one-dimensional (1D) van der Waals heterostructures with single-walled carbon nanotube (SWCNT) as a template. A typical 1D heterostructure is composed of SWCNT, boron nitride nanotube (BNNT), and molybdenum disulfide nanotube (MoS2NT), coaxially grown by serial chemical vapor deposition (CVD) steps [1]. Isolated SWCNTs, BN-CVD at high temperatures such as 1100 °C from ammonia borane, and MoS2-CVD from MoO3 and Sulfur are original key requirements. Recently, we have achieved the additional CVD growth of carbon nanotubes from ethanol-CVD. We can remove SWCNT from SWCNT@BNNT by gentle oxidation process because BNNT is thermally more stable than SWCNT [2]. By comparing optical properties of BNNT@MoS2NT and SWCNT@BNNT@MoS2NT, we found the strong photoluminescence (PL) from monolayer MoS2NT of BNNT@MoS2NT and the exciton energy transfer between SWCNT and MoS2NT through thin BNNT for SWCNT@BNNT@MoS2NT [2]. We expect to prove the inter-tube excitons from the ultrafast optical spectroscopy [3]. We can realize various hetero-nanotubes in different morphologies such as SWCNT thin film, pillar-suspended SWCNT, chirality separated SWCNT deposited on TEM grid, and bulk SWCNTs grown on zeolite-supported catalysts [4]. Simply with SWCNT@BNNT in a thin film form, the enhanced thermal conductance [5] is very promising for macroscopic applications of heterostructures. Because BNNT coating over SWCNT film will not influence the transparency in the visible range, those films are immediately applicable for a saturable absorber in mode-lock fiber lasers. In order to fabricate a practical electronic or optoelectronics devices, micro-meter long 1D van der Waals heterostructure SWCNT@BNNT@MoS2NT were prepared between Si pillars. After transferring to SiO2 substrates and fabricating metal electrodes, we have examined various device characteristics. The naturally p-doped SWCNT and n-type MoS2NT becomes a radial semiconductor–insulator–semiconductor (S-I-S) heterojunction diode [6]. Optoelectronic and electronic properties of such devices will be discussed.Part of this work was supported by JSPS KAKENHI Grant Numbers JP18H05329, JP20H00220, and by JST, CREST Grant Number JPMJCR20B5, Japan.

Preparation of Nickel Oxide Supported Zeolite catalyst (NiO/Na-ZSm-5) for Asphaltene Adsorption: A Kinetic and Thermodynamic Study

One of the important issues in oil industry is related to asphaltene precipitation during different stages, and using nanoparticles is known as a common method for solving this problems. Although nickel oxide and zeolite have been addressed in previous researches for solving asphaltene precipitation problem, Using NiO/Na-ZSm-5 (the main goal of this study) has not been developed for solving relevant asphaltene precipitation problem. The crystalline structure and morphology of the synthesized nanoparticles have been analyzed with the help of XRD, SEM, FTIR and EDX. Results show that the nanoparticles were well synthesized and after synthesis with a diameter of 13.6 nm. The EDX analyses also approved that an amount of asphaltene was adsorbed by the sorbent. Asphaltene adsorption experiments were carried out at various asphaltene concentrations and different temperatures and the effect of different variables of initial asphaltene concentrations, temperature and ratio of heptane to toluene were evaluated on asphaltene adsorption rate. The results indicate that with an increase in the initial asphaltene concentration from 25 to 2000 ppm, the asphaltene adsorption rate in zeolite increases. In concentrations less than 500 ppm, a rise in temperature results in reduced asphaltene adsorption, while at concentrations higher than 500 ppm, with a rise in temperature from 25°C to 55°C, asphaltene adsorption capacity on zeolite increases. Also greater adsorption has been observed for Heptane/Toluene=0.4 with q=25.17 mg/g. For determining the kinetic mechanism of this process, the experimental data were adapted according to Lagrangian pseudo-first and second-order models. The Langmuir and Freundlich adsorption isotherms were evaluated, in which the isotherms resulting from the Langmuir isotherm model were of adequate conformity. This indicates that adsorption at the homogenous level occurred with single-layered coating. In the final step, after evaluating the thermodynamic conditions, the spontaneity of the asphaltene adsorption process was proven.

Synthesis of light olefins from syngas over zeolite-supported Fe catalyst

Synthesis of light olefins from syngas over zeolite-supported Fe catalyst

Highly Selective Hydrodeoxygenation of Dibenzofuran into Bicyclohexane over Hierarchical Pt/ZSM-5 Catalysts

Fabricating zeolite-supported catalysts with excellent catalytic performance for hydroconversion of bio-oils into high-quality fuels is still a great challenge. Herein, hierarchical ZSM-5 zeolites ...

Regeneration mechanism of a deactivated zeolite-supported catalyst for the combustion of chlorinated volatile organic compounds

Industrial catalysis is confronted with the common problem of catalyst deactivation.

Synthesis of Ni-Modified ZSM-5 Zeolites and Their Catalytic Performance in n-Octane Hydroconversion.

Ni-modified ZSM-5 zeolites with different nickel contents were successfully prepared by the in situ synthesis method and the impregnation method. The synthesized samples were characterized by XRD, SEM, N2 adsorption–desorption isothermals, and Py-FTIR. The characterization results show that both the textural properties and crystallization of Ni-modified ZSM-5 zeolites were preserved well, and their acidic properties can be modulated after nickel modification. The corresponding NiMo catalysts supported on Ni-modified ZSM-5 zeolites were prepared by the incipient wetness co-impregnation method, and their catalytic performances were evaluated in n-octane hydroconversion. Compared to the those modified by the in situ synthesis method, ZSM-5 zeolite-supported catalysts modified by the impregnation method exhibit higher stability and higher isomerization selectivity. This is due to the synergistic effect between Brønsted acid sites and Lewis acid sites on the Ni-modified ZSM-5 zeolites, especially for the NiMo/1Ni-Z5 catalyst.

A low temperature catalytic-type combustible gas sensor based on Pt supported zeolite catalyst films

In this study, a catalytic-type combustible gas sensor was fabricated by the screen-printing method. Pt supported catalysts (Pt-HZSM5) were prepared by a wet impregnation method using HZSM5 zeolite as support. It was found that Pt-HZSM5 catalysts have a highly catalytic activity to H2 and CO at low temperatures and a selectively and fully combustible was observed at only 150 °C. A good dispersion state of Pt nanoparticles on HZSM5 zeolite particles was beneficial for the catalytic oxidization of CO and H2. However, a high loading amounts lead to a poor dispersion state and a weak catalytic activity. The thick film sensor based on Pt-HZSM5 catalyst was found to be highly sensitive to combustible gas with a good linearity up to 2% and a limitation of detection (LOD) around 50 ppm. Due to the low operation temperature, a highly selectivity was obtained for CO and H2 and no cross-sensitivity to interfering gases such as CH4 and VOCs. It was indicated that the present developed catalytic-type gas sensors could be used for the leakage detection and monitor for H2 and CO with a low power consumption and a good selectivity.

Boosting Ni Dispersion on Zeolite-Supported Catalysts for CO2 Methanation: The Influence of the Impregnation Solvent

In this work, an enhancement of Ni0 particle dispersion over zeolite-supported catalysts was intended by tuning the impregnation solvent. For this purpose, a series of 15 wt % Ni catalysts supporte...

Effect of support acidity during selective hydrogenolysis of glycerol over supported palladium-ruthenium catalysts.

We report the role of the acidity of support during the selectivity hydrogenolysis of glycerol over supported bimetallic palladium-ruthenium (PdRu) catalysts. The PdRu nanoparticles were supported on a series of metal oxides and zeolitic supports via the modified impregnation method and tested for the liquid-phase hydrogenolysis of glycerol using gaseous hydrogen. The relative acid site densities of selected catalysts were determined by ammonia temperature-programmed desorption and pyridine desorption experiments. Based on these studies, we report a direct correlation between the catalytic activity (conversion and 1,2 propane diol yield) and two different acid sites (strong acid sites and very strong acid sites). Besides zeolite-supported catalysts, TiO2 supported PdRu nanoparticles exhibit moderate catalytic activity; however, this catalyst shows high selectivity for the desired C-O bond cleavage to produce C3 products over the undesired C-C bond cleavage to produce < C3 products. This article is part of a discussion meeting issue 'Science to enable the circular economy'.

Isostructural Atomically Dispersed Rhodium Catalysts Supported on SAPO-37 and on HY Zeolite.

Zeolites are widely applied supports for metal catalysts, but molecular sieves with comparable structures-silicoaluminophosphates (SAPOs)-have drawn much less attention and been overlooked as supports for atomically dispersed metals. Now, we report SAPO-37 as a support for atomically dispersed rhodium in rhodium diethylene complexes, made by the reaction of Rh(η2-C2H4)2(acetylacetonate) with the support and anchored by two Rh-O bonds at framework tetrahedral sites, as shown by infrared and extended X-ray absorption fine structure spectra. The ethylene ligands were readily replaced with CO, giving sharp νCO bands indicating highly uniform supported species. A comparison of the spectra with those of comparable rhodium complexes on zeolite HY shows that the SAPO- and zeolite-supported complexes are isostructural, providing an unmatched opportunity for determining support effects in catalysis. The two catalysts had similar initial room-temperature activities per Rh atom for ethylene conversion in the presence of H2, but the SAPO-supported catalyst was selective for ethylene hydrogenation and the zeolite-supported catalyst selective for ethylene dimerization; correspondingly, the catalyst on the SAPO was more stable than that on the zeolite during operation in a flow reactor.

Metal encapsulation in zeolite particles: A rational design of zeolite-supported catalyst with maximum site activity

Zeolite-supported metal catalysts have been proven effective in many important catalytic reactions, such as hydrogenation, Fisher-Tropsch synthesis, automobile exhaust catalysis, selective catalytic reduction and many others. Despite the successful preparation of the catalyst through widely adopted methods, including ion exchange and impregnation, the metal dispersion over the zeolite is lack of control with high randomness. This renders the so-called “catalytic performance” an overall contribution from the metal sites located inside the zeolite micropores and those located on the external surface. This is exceptionally true for small to medium pore zeolites with typical free apertures of 0.3–0.6 nm (such as LTA and MFI). A more rational design of zeolite-supported metal catalysts is by encapsulating the metal nanoparticles or clusters within zeolite pores prior to the zeolite formation. Encapsulation of metals in zeolite prevents them from sintering and sulphur poisoning by cage confinement and molecular exclusion (via well-defined pore size and shape), respectively. This paper gives a new perspective on using metal clusters and nanoparticles as catalysts and the design of an effective zeolite-supported catalytic system.