Shell Catalysts Research Articles

Green, lipophilic and recyclable catalysts for the aerobic oxidation of alcohols

Lipophilic walnut shell and perlite-supported Palladium nanoparticles were found to be highly efficient recoverable solid catalyst for the aerobic oxidation of benzylic and aliphatic alcohols under air atmosphere in aqueous media. These catalysts were prepared by lipophilization of walnut shell powder and expanded perlite by Zycosil, followed by immobilization of nanoparticles without any external reducing agent. These catalytic systems provide benzylic and aliphatic aldehydes and ketones in high yields and selectivity by aerobic oxidation corresponding alcohols under air atmosphere. These reusable green catalysts were characterized by Fourier-transform infrared spectroscopy (FT-IR), atomic adsorption, N2 adsorption/desorption porosimetry and transmission electron microscope. It showed the isolated palladium 5–18 nm and 6–22 nm nanoparticles for Lipophilic walnut shell and perlite-based catalyst, respectively. Moreover, the cytotoxic potential of the preparation of lipophilic walnut shell powder and lipophilic expanded perlite against erythroleukemia K562 cancer cell lines and peripheral blood mononuclear cells as normal cells were evaluated.

Enhanced Selective Oxidation of Ammonia in a Pt/Al2O3@Cu/ZSM-5 Core–Shell Catalyst

The ammonia slip catalyst (ASC) is an essential final step in the emission control system and involves the selective oxidation of NH3 to N2. The state-of-the-art ASC has a dual-layer architecture c...

Nanoscale architecture of ceria-based model catalysts: Pt–Co nanostructures on well-ordered CeO2(111) thin films

We have prepared and characterized atomically well-defined model systems for ceria-supported Pt–Co core–shell catalysts. Pt@Co and Co@Pt core–shell nanostructures were grown on well-ordered CeO2(111) films on Cu(111) by physical vapour deposition of Pt and Co metals in ultrahigh vacuum and investigated by means of synchrotron radiation photoelectron spectroscopy and resonant photoemission spectroscopy. The deposition of Co onto CeO2(111) yields Co–CeO2(111) solid solution at low Co coverage (0.5 ML), followed by the growth of metallic Co nanoparticles at higher Co coverages. Both Pt@Co and Co@Pt model structures are stable against sintering in the temperature range between 300 and 500 K. After annealing at 500 K, the Pt@Co nanostructure contains nearly pure Co-shell while the Pt-shell in the Co@Pt is partially covered by metallic Co. Above 550 K, the re-ordering in the near surface regions yields a subsurface Pt–Co alloy and Pt-rich shells in both Pt@Co and Co@Pt nanostructures. In the case of Co@Pt nanoparticles, the chemical ordering in the near surface region depends on the initial thickness of the deposited Pt-shell. Annealing of the Co@Pt nanostructures in the presence of O2 triggers the decomposition of Pt–Co alloy along with the oxidation of Co, regardless of the thickness of the initial Pt-shell. Progressive oxidation of Co coupled with adsorbate-induced Co segregation leads to the formation of thick CoO layers on the surfaces of the supported Co@Pt nanostructures. This process is accompanied by the disintegration of the CeO2(111) film and encapsulation of oxidized Co@Pt nanostructures by CeO2 upon annealing in O2 above 550 K. Notably, during oxidation and reduction cycles with O2 and H2 at different temperatures, the changes in the structure and chemical composition of supported Co@Pt nanostructures were driven mainly by oxidation while reduction treatments had little effect regardless of the initial thickness of the Pt-shell.

Developing Cu-MOR@SiO2 Core–Shell Catalyst Microcapsules for Two-Stage Ethanol Direct Synthesis from DME and Syngas

Catalytic conversion of Syngas and dimethyl ether to ethanol is a green strategy of harnessing fine chemicals from nonpetroleum origins. In the process, catalyst deactivation coupled with higher by...

Hydrogen gas yield and trace pollutant emission evaluation in automotive shredder residue (ASR) gasification using prepared oyster shell catalyst

This work examines the hydrogen gas yield and trace pollutants partitioning in automobile shredder residue (ASR) catalytic gasification by fixed bed and fluidized bed gasifier with controlling at equilibrium ratio (ER) 0.2, temperature 900 °C, and 5%–15% prepared catalyst addition. Oyster shell (OS) is a valuable resource due to its higher calcium content that it could prepare as a catalyst for enhancing the hydrogen production in ASR gasification. In the case of the fixed bed gasifier experiments, the highest lower heating value (LHV) and syngas production were found at 900 °C and 10% OS catalyst addition. The maximum H2 and CO composition were 6.57% and 5.97%, respectively. The LHV of syngas was approximately 4.43 MJ/Nm3. The fluidized bed gasifier could provide a good ASR decomposition and heat transfer behavior. The syngas yield results indicated the maximum H2 and CO composition were 12.12% and 10.59%, respectively. It was obviously showed that the syngas production and energy conversion efficiency were enhanced by applying fluidized bed gasifier. The maximum produced gas LHV was 10.77 MJ/Nm3 as well as the cold gas efficiency (CGE) of produced gas was 71.62%. On the other hand, the volatile sulfur and chlorine speciation formed in ASR gasification were mainly partitioned in the solid and/or liquid phase. It implied that tested OS catalysts could inhibit the volatile sulfur and chlorine speciation emission in the produced gas as well as enhance the produced gas quality. In summary, this research could provide basic insight into enhanced syngas production and quality in ASR catalytic gasification using the prepared OS catalyst.

Magnetically recoverable Ir/IrO2@Fe3O4 core/ SiO2 shell catalyst for the reduction of organic pollutants in water

Ir/IrO2 nanoparticles have been immobilized on Fe3O4 core/ SiO2 shell via surface modified NH2 functional groups for the reduction of organic pollutants in water. Ir/IrO2@Fe3O4 core/ SiO2 shell catalyst showed excellent catalytic activity in the reduction of 4-nitrophenol, 4-nitroaniline and 2-nitroaniline with the rate constants of 1.32 min−1, 1.34 min−1 and 0.92 min−1 respectively. The reductions were carried out in presence of NaBH4 reducing agent at room temperature. The presence of Ir/IrO2 interfaces in the catalyst is believed to be responsible for its high catalytic activity. Moreover, the catalyst shows high stability and efficient recyclability.

Degradation of surfactant waste of leather tanning using Fe2O3/activated carbon catalyst

The development of the tannery industry in addition to being beneficial for the economic growth of the community also has a negative impact on the environment due to the disposal of waste produced. Components of waste produced from the leather tanning industry include residual protein and fat, surfactants, anti-bacterial, anti-fungal, coloring and tanning agents. One component that is found in surfactants and often pollutes waters is alkyl benzene sulfonate and linear alkyl benzene sulfonate surfactants. Alkyl benzene sulfonate (ABS) is an anionic surfactant that has a very long and branched carbon chain that is difficult to degrade by microorganisms in nature. Characterization and testing of the activity of porous/activated carbon catalysts will be carried out. The type of porous activated carbon used is coconut shell carbon with microspores character. The stages of this research consisted of the process of impregnation of iron oxide on porous carbon, the surfactant waste degradation process and the characterization of the catalysts produced. Based on the research that has been done, it can be concluded that the catalyst Fe2O3/coconut shell activated carbon is very effective to be applied for the degradation of surfactant waste. The degradation capacity of surfactant wastes increases with increasing concentration of active site Fe. The capacity of the surfactant waste degradation reaction using coconut shell catalyst at t = 3 hours for variations in the concentration of Fe 2%, 4% and 6% respectively 6.77 mmol/gram catalyst, 3.18 mmol/gram catalyst and 1.61 mmol/gram catalyst. The data show that the surfactant waste degradation reaction capacity increases with the increase in the composition of iron oxide added to the surface of the porous carbon support.

Catalytic Technologies for CO Hydrogenation for the Production of Light Hydrocarbons and Middle Distillates

In South Korea, where there are no resources such as natural gas or crude oil, research on alternative fuels has been actively conducted since the 1990s. The research on synthetic oil is subdivided into Coal to Liquid (CTL), Gas to Liquid (GTL), Biomass to Liquid (BTL), etc., and was developed with the focus on catalysts, their preparation, reactor types, and operation technologies according to the product to be obtained. In Fischer–Tropsch synthesis for synthetic oil from syngas, stability, CO conversion rate, and product selectivity of catalysts depends on the design of their components, such as their active material, promoter, and support. Most of the developed catalysts were Fe- and Co-based catalysts and were developed in spherical and cylindrical shapes according to the reactor type. Recently, hybrid catalysts in combination with cracking catalysts were developed to control the distribution of the product. In this review, we survey recent studies related to the design of catalysts for production of light hydrocarbons and middle distillates, including hybrid catalysts, encapsulated core–shell catalysts, catalysts with active materials with well-organized sizes and shapes, and catalysts with shape- and size-controlled supports. Finally, we introduce recent research and development (R&D) trends in the production of light hydrocarbons and middle distillates and in the catalytic processes being applied to the development of catalysts in Korea.

Core–Shell HZSM-5@silicalite-1 Composite: Controllable Synthesis and Catalytic Performance in Alkylation of Toluene with Methanol

HZSM-5@silicalite-1 catalysts were prepared by the hydrothermal method, and the structure, morphology, acidity and pore texture of core–shell catalysts were studied by XRD, SEM, TEM, NH3-TPD, Py-IR and N2 adsorption/desorption isotherms in detail. Their catalytic performances were tested in the alkylation reaction of toluene with methanol. The results showed that a coating layer was formed in the form of silicalite-1 on HZSM-5. NH3-TPD measurements indicated that HZSM-5@silicalite-1 contained less strong acid sites but more weak acid sites than the parent HZSM-5. The selectivity of p-xylene for toluene alkylation was approximately linear with the percentage of weak acid in total acid. Under the optimal reaction conditions, the conversion of toluene was 34.15%, and the selectivity of p-xylene was 96.77%.

Enhanced water oxidation performances of birnessite and magnetic birnessite nanocomposites by transition metal ion doping

Co2+ and Ni2+ doped layered birnessite and birnessite-manganese ferrite core–shell catalysts displayed enhanced chemical stability and performance in chemical and electrochemical water oxidation reactions.

Preparation of low carbon olefins on a core-shell K-Fe5C2@ZSM-5 catalyst by Fischer-Tropsch synthesis.

In this study, a core–shell catalyst based on Fe5C2@ZSM-5 (ZSM-5 capped Fe5C2 as active phase) is prepared by the coating-carbonization method for Fischer–Tropsch synthesis (FTS). Further, the designed ZSM-5 zeolites are utilized to screen the low carbon hydrocarbons from the products generated on the iron carbide active centre, and for catalytic disassembly of the long-chain hydrocarbons into low carbon olefins. Prior to utilization, the physical–chemical properties of the prepared catalysts are systematically characterized by various techniques of X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), Fourier transform infrared (FT-IR), and scanning electron microscopy (SEM) as well as transmission electron microscopy (TEM) observations, in addition to the effects of coating-carbonization, molecular sieve coating amount, and K-doping on core–shell iron-based catalysts. Next, the performance of Fischer–Tropsch synthesis is investigated in a micro-fixed bed reactor. The results manifest that, comparing with Fe5C2 and a supported Fe/ZSM-5 catalyst prepared by the traditional impregnation method, the core–shell Fe5C2@ZSM-5 catalysts show higher CO conversion rate, reaction activity and selectivity to low-carbon olefins. Comparatively, the Fe5C2@ZSM-5C catalyst prepared by carbonization after the coating method exhibited more surface area, smaller average pore size, and more reactive active sites, resulting in the improvement of screening of high carbon hydrocarbons and the enhancement of selectivity to low carbon olefins, in comparison to those prepared by the carbonization-coating method. In conclusion, the K-doping catalyst had significantly improved the reactive activity of the core–shell Fe5C2@ZSM-5 catalyst and the selectivity to low carbon olefins, while the CO conversion on K–Fe5C2@ZSM-20C still remained good.

Core-shell structured catalysts for thermocatalytic, photocatalytic, and electrocatalytic conversion of CO2.

Catalytic conversion of CO2 to produce fuels and chemicals is attractive in prospect because it provides an alternative to fossil feedstocks and the benefit of converting and cycling the greenhouse gas CO2 on a large scale. In today's technology, CO2 is converted into hydrocarbon fuels in Fischer-Tropsch synthesis via the water gas shift reaction, but processes for direct conversion of CO2 to fuels and chemicals such as methane, methanol, and C2+ hydrocarbons or syngas are still far from large-scale applications because of processing challenges that may be best addressed by the discovery of improved catalysts-those with enhanced activity, selectivity, and stability. Core-shell structured catalysts are a relatively new class of nanomaterials that allow a controlled integration of the functions of complementary materials with optimised compositions and morphologies. For CO2 conversion, core-shell catalysts can provide distinctive advantages by addressing challenges such as catalyst sintering and activity loss in CO2 reforming processes, insufficient product selectivity in thermocatalytic CO2 hydrogenation, and low efficiency and selectivity in photocatalytic and electrocatalytic CO2 hydrogenation. In the preceding decade, substantial progress has been made in the synthesis, characterization, and evaluation of core-shell catalysts for such potential applications. Nonetheless, challenges remain in the discovery of inexpensive, robust, regenerable catalysts in this class. This review provides an in-depth assessment of these materials for the thermocatalytic, photocatalytic, and electrocatalytic conversion of CO2 into synthesis gas and valuable hydrocarbons.

SiO2@MnO x @Na2WO4@SiO2 core-shell-derived catalyst for oxidative coupling of methane.

SiO2@MnOx@Na2WO4@SiO2 core–shell catalysts were prepared and their fabrication was confirmed using transmission electron microscopy. The formation of Mn-based nanosheets on the silica spheres is important for the deposition of nanoscopic Na2WO4. The SiO2@MnOx@Na2WO4@SiO2 core–shell catalysts were used for the oxidative coupling of methane at a temperature of 700–800 °C at which the nanostructures were completely destroyed. Although the core–shell structures did not survive the high-temperature oxidative coupling of methane, the selective production of olefins and paraffins can be attributed to highly dispersed Na2WO4 derived from confined core–shell structures.

Design of catalysts comprising a nickel core and ceria shell for hydrogen production from plastic waste gasification: an integrated test for anti-coking and catalytic performance

A novel core–shell catalyst with high coking resistance ability was applied for hydrogen production from plastic waste.

Plasmonically driven photocatalytic hydrogen evolution activity of a Pt-functionalized Au@CeO2 core–shell catalyst under visible light

Plasmonically driven photocatalytic hydrogen evolution activity of a Pt-functionalized Au@CeO2 core–shell catalyst under visible light was insightfully investigated for the first time.

An Na-modified Fe@C core-shell catalyst for the enhanced production of gasoline-range hydrocarbons via Fischer-Tropsch synthesis.

Although numerous studies have been conducted in the field of converting syngas to value-added fuels, selectively converting syngas to gasoline-range hydrocarbons (C5–12 hydrocarbons) remains a big challenge. Alkali metal (namely, K, Na and Li)-modified Fe@C core–shell catalysts were synthesized by a one-step hydrothermal method for Fischer–Tropsch synthesis. An optimized selectivity of 56% for the C5–12 hydrocarbons with a higher CO conversion of about 95% was obtained for the FeNa2.0@C catalyst compared to that for other alkali metal-modified Fe@C catalysts. According to the characterization results, the incorporation of alkali metals into Fe@C enhanced the conversion of FeCO3 to Fe3O4, which promoted the formation of the FTS active phase iron carbides. In particular, the strongest interaction of Fe–alkali metal and the highest amount of surface carbon layers were observed after adding an Na promoter into Fe@C in contrast to that observed for K and Li promoters, which strengthened the synergistic effect of Fe–Na metals and the spatial confinement of the core–shell structure, further improving the C5–12 hydrocarbon selectivity.

Metal–Organic Framework-Membranized Bicomponent Core–Shell Catalyst HZSM-5@UIO-66-NH2/Pd for CO2 Selective Conversion

In this study, a Zr-based metal–organic framework (MOF)-membranized bicomponent core–shell catalyst HZSM-5@UIO-66-NH2/Pd was produced. Monodispersed HZSM-5 zeolites acted as the core for the epitax...

CuO–MoO2–CeO2 yolk–albumen–shell catalyst supported on γ-Al2O3 for denitration with resistance to SO2

Development of denitration catalysts is highly important to controlling the level of NOx pollution. In this article, we report a novel CuO–MoO2–CeO2 catalyst with a yolk–albumen–shell structure supported on commercial γ-Al2O3 for the denitration study. The yolk catalyst CuO/γ-Al2O3 was first prepared with impregnation method by loading CuO on the γ-Al2O3 support, which provides a platform for further loading MnO, Cr2O3 or MoO2 as the albumen component. While measurements confirmed CuO–MoO2/γ-Al2O3 as the best choice, the final CuO–MoO2–CeO2/γ-Al2O3 yolk–albumen–shell catalyst was formed by loading CeO2 as the shell. The denitration performance of different catalysts in the presence or absence of SO2 was studied, followed by the investigation of denitration mechanism through XRD and SEM characterizations. The investigation reveals that the denitration performance of catalysts highly depends on their structures and compositions, which could be affected in the presence of SO2. In particular, the CuO–MoO2–CeO2/γ-Al2O3 catalyst, prepared under the conditions of roasting temperature of 400 °C, roasting time of 4 h and loading of 5%, shows outstanding SO2-resistance performance while its denitration efficiency is maintained between 81 and 83%.

Fish-Bone-Doped Sea Shell for Biodiesel Production from Waste Cooking Oil

Transesterification of waste cooking oil with methanol using calcined waste fish bone and sea shell catalyst was studied. An inexpensive and environmentally benign catalyst was prepared from waste fish bones (WFB) and Tellina tenuis shells (TTS), and the catalyst was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Brunauer–Emmett–Teller, X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS) techniques. From XRD, it was confirmed that the major phase of WFB was hydroxyapatite and calcium oxide was found to be the dominant fraction of calcined TTS. FTIR and SEM–EDS analysis of WFB confirmed the presence of hydroxyapatite exhibiting hexagonal structure. Different combinations of WFB and TTS have been developed to obtain novel catalyst composition. Above 94% conversion was reported with various combinations of WFB and TTS using 3 wt% catalyst, 12:1 molar ratio, 65 °C and 1.5 h.

Phosphotungstic Acid Supported on Magnetic Mesoporous Tantalum Pentoxide Microspheres: Efficient Heterogeneous Catalysts for Acetalization of Benzaldehyde with Ethylene Glycol

In this study, magnetically-recoverable core–shell catalysts with different amount of H3PW12O40 loading [Fe3O4@C@mTa2O5-NH2-PW12 (w%)] were prepared by the application of phosphotungstic acid supported on amino group functionalized magnetic core–shell mesoporous tantalum pentoxide microspheres. The prepared samples were characterized by FT-IR, N2-adsorption–desorption isotherms, TEM, SEM, Pyridine-IR analysis, XRD and magnetism. Fe3O4@C@mTa2O5-NH2-PW12 samples present both Bronsted and Lewis acidity, large BET surface area and high magnetization. The catalytic activity was evaluated by the acetalization of different aldehydes with diols, and the results show that Fe3O4@C@mTa2O5-NH2-PW12 (14.47%) catalyst exhibits the highest catalytic activity for acetalization of aldehydes with glycols with 94.5% conversion of benzaldehyde and 99% selectivity to benzaldehyde glycol acetal at 80 °C. The catalytic activity of the catalyst for acetalization is related to its total acidity and Bronsted–Lewis acid synergy. The catalyst Fe3O4@C@mTa2O5-NH2-PW12 can be easily recovered and reused for at least 5 times without obvious decrease of catalytic activity.