Wet Ion Exchange Research Articles

Cu, Co, or Ni species in exchanged Y zeolite catalysts and their denitration performance for selective catalytic reduction by ammonia

Identifying the role of Cu, Co, or Ni species in exchanged zeolite catalysts by different preparation methods has been widely concerned for selective catalytic reduction by ammonia (NH3-SCR). Here, we found that ammonia wet ion exchange method (AWIE) was useful for increasing ionic species and improving ion polymerization degree in traditional NaY (Si/Al = 2.5) zeolites. Cu, Co, and Ni substituted Y zeolite prepared by AWIE method achieved better SCR performance than those by conventional wet ion exchange method (CWIE). Meanwhile, the coordination states and chemical environments of Cu, Co, and Ni exchanged species influenced the redox and adsorption properties of catalysts. Cu-NH3-IE catalyst had a wider SCR temperature window than Co-NH3-IE and Ni-NH3-IE catalysts owing to its more stable NH3 adsorption, lower temperature, and smaller area of reduction peak. We proposed that the balance of NH3 adsorption and oxidation in thermodynamics and kinetics was the key for high N2 selectivity. This work provided a new idea for modifying the active sites of zeolite catalysts to achieve high activity and N2 selectivity in a broad temperature window.

Role of Al pairs on effective N2O decomposition over the ZSM-5 zeolite catalyst

Series of ZSM-5 zeolites with diverse contents and locations of Al pairs were synthesized, and Co2+ ions were subsequently anchored at the Al pairs of ZSM-5 zeolites by wet ion-exchange with H protons. The Co-ZSM-5 sample derived from the mixtures of AlCl3 and TEOS of Si/Al=30.3 showed the best deN2O performance. Analysis on Co (Ⅱ) ion exchange capacity demonstrated the content of Al pairs followed the sequence: AlCl3 (0.84) > Al(NO3)3 (0.73) > aluminum isopropoxide (0.65) and TEOS (0.84) > silicic acid (0.57). More Al pairs coordinated with protons or cobalt ions were essentially associated with better performances for N2O catalytic dissociation. Moreover, Si source had a significant effect on the location of Al pairs determined by UV–vis–DRS of bare Co (Ⅱ), Al pairs of ZSM-5 zeolite synthesized from TEOS were enriched in the sinusoidal channel (γ site), whereas those synthesized from silicic acid were concentrated in the channel intersections (6-MRs β site). The theoretical calculation revealed that the O2 desorption at γ-site Co2+ of ZSM-5 zeolite required to overcome less energy barrier (23.8 kcal/mol) than that at β-site one.

Selective Catalytic Reduction of N2O by CO over Fe-Beta Zeolites Catalysts: Influence of Iron Species Distribution

In this paper, selective catalytic reduction (SCR) of N2O by CO was investigated over Fe-beta zeolites catalysts. The catalysts were prepared by wet ion-exchange (IE), impregnation (IM) and solid state ion-exchange (SSIE) methods. These catalysts were characterized by XRD, UV–vis DR spectroscopy, H2-TPR, TPD and in-situ DRIFTS. At 350 °C, more than 90% N2O conversion could be obtained over the Fe-beta-IE catalyst. The activity for N2O removal of Fe-beta-IE was higher than Fe-beta-IM and Fe-beta-SSIE catalysts. The UV–vis spectra showed that 84.2% of isolated Fe(III) ion appeared on Fe-beta-IE catalyst. It indicated that the isolated Fe(III) ions might be considered as the active sites for N2O reduction. Besides, in the presence of H2O, the activities in CO-SCR for N2O removal over Fe-beta catalysts were inhibited, which might be due to the hydroxylation deactivation of iron species and excess accumulation of carbonates.

Synthesis of Co/Mesoporous Silica-Alumina Catalyst from Sidoarjo Mud Templated by Bovine Bone's Gelatin for Hydrocracking of Waste Lubricant

The synthesis of Co/Mesoporous Silica-Alumina (MSA) catalyst from Sidoarjo mud templated by bovine bone’s gelatin for hydrocracking of waste lubricant has been done. The gelatin was obtained from bovine bone by the combination method of acids (CH 3 COOH 4% and HCl 1 M) and base (NaOH 0.1 M). The silica was obtained from Sidoarjo mud using the batch method (distilled water, HCl 6 M, and NaOH 6 M). The synthesis of MSA was carried out using silica from Sidoarjo mud with the variation of Si/Al of 25, 50, and 100, respectively, using gelatin as a template to produce MSA(25), MSA(50), and MSA(100); and was then analyzed by FTIR and acidity test. The MSA with the highest acidity and optimum thermal stability (MSA(x)) was analyzed by GSA and TEM. The cobalt metal from Co(NO 3 ) 2 ·6H 2 O as salt precursor was loaded to the MSA(x) using the Wet Impregnation (WI) and Ion Exchange (IE) method. The Co/SAM(x) was tested as a catalyst for hydrocracking of waste lubricant oil. The results showed that the MSA(100) has the highest acidity and optimum thermal stability with an average pore diameter of 3.37 nm, the pore volume of 0.87 cm 3 g –1 , and a surface area of 230.73 m 2 . The cobalt metal content loaded on the MSA(100) by WI and EI method was 0.50% and 0.15 wt.%, respectively. The hydrocracking of lubricant oil using Co/MSA(100)WI catalyst yielded a liquid fraction of 39.20 wt.% with selectivity for gasoline and diesel fraction of 29.30 and 9.48 wt.%. The Co/MSA(100)IE catalyst produced a liquid fraction of 28.10 wt.% with selectivity for gasoline and diesel fraction of 22.70 and 5.32 wt.%.

Zinc Oxide/ Silver Sulfide (ZnO/Ag<sub>2</sub>S) Core-Shell Type Composite for Wide Range Absorption of Visible Spectra: Synthesis and Characterization

This work presents the synthesis of zinc oxide /silver sulfide (ZnO/Ag2S) core/shell type composite; using combined wet chemical precipitation method and ion exchange mechanism; for wide range absorption of visible spectra by the composite. Synthesis is performed in three steps. In the first step; ZnO nanoparticles (nanocores) are produced, in the second step; ZnS layer is deposited over ZnO nanocores and in the third step; Zn from ZnS is replaced by Ag to form Ag2S shell over ZnO; using ion exchange mechanism. The presence of reflection peaks of ZnO and Ag2S in XRD spectra confirms the formation of ZnO/Ag2S composite. SEM image of ZnO shows the formation of near spherical ZnO nanoparticles of diameter in range 256nm to 584nm with a smooth surface, while SEM image of ZnO/Ag2S composite shows the formation of Ag2S layer over ZnO cores as indicated by rougher and contrasted surface as compared to bare ZnO cores. Also, the size of composite particles became larger than ZnO nanocores (100µm-200µm), which further confirms the formation of Ag2S shell over ZnO nanocores. The optical absorption spectrums of both ZnO and ZnO/Ag2S composite clearly indicate that synthesized composite absorb strongly in UV to IR region of the electromagnetic spectrum as compared to ZnO nanocores; which absorb only in UV region. Therefore, the synthesized composite could be used as a photovoltaic material.

Geopolymer technology for the solidification of simulated ion exchange resins with radionuclides

In this study, geopolymer was applied to convert ion exchange resins contaminated with radionuclides into a solid waste form. Geopolymer has superior properties to enable the encapsulation of spent resins. The allowable limit of resin content in the converted waste form was analyzed to evaluate the solidification capability of geopolymer. The encapsulation of ion exchange resins into solid waste form was conducted using geopolymer prepared with ground granulated blast furnace slag and alkaline solution in an ambient atmosphere, with the addition of wollastonite powder to adjust its mechanical properties. The physical and mechanical properties of the converted solid wastes prepared using different resin content ratios and various SiO2/Na2O molar ratios were tested. The results indicate the wet ion exchange resin (the moisture content in the resin is 51%) content and the compressive strength of the solid resin waste were measured as 45 wt% and 8.5 MPa, respectively. The morphology and mineral phases of the formed solid wastes were characterized using SEM and EDS. The mechanical performance test results proved the formed solid wastes could comply with the fuel cycle and material administration standards ruled by the Atomic Energy Council of Taiwan. These results suggest that this blast furnace slag-based geopolymer is a promising matrix material for the solidification of radioactive wastes.

Polynuclear Co-oxo cations in the catalytic oxidation of CO on Co-modified ZSM-5 zeolites

Structure, reducibility and catalytic activity in the oxidation of CO were studied for Co-modified ZSM-5 zeolites (Co/Al = 0.1–0.9) prepared via impregnation, solid-state and wet ion exchange. According to TEM, XPS, DRIFTS, UV–vis-DRS, H2 -TPR and in situ CO- reduction studies the synthesis method and the Co content affect the surface distribution of Co as Со2+ ions, cationic oxo-complexes and highly dispersed CoxOy species. The oxidation of CO by oxygen was studied at 50–450 °C in pulse and flow regimes at the 2:1 and 1:1 CO:O2 ratios. Co-zeolites prepared by impregnation were the most active in the oxidation of CO. It was proposed that oxo cations [CoxOy]n+ (n = 1, 2) with Co(III) prevailing in their structure play a crucial role in CO adsorption and catalytic oxidation. The new absorption band at 2215 cm−1 attributed to CO adsorbed on the Co(III) located in oxo cations was found. These oxo-cations contain a mobile oxygen atoms and, thus, can be easily reduced to the catalytically active Сo3+/Сo2+and Сo2+/Сo+ pairs stabilized in zeolites. In contrast to the supported catalysts based on Co3O4, the activity of Co-ZSM-5 increased during the reaction, and the light-off T50 drifted to 120 °C.

An efficient Co-ZSM-5 catalyst for the abatement of volatile organics in air: effect of the synthesis protocol

Co supported on ZSM-5 (Co-ZSM-5) catalysts was synthesized by wet ion exchange (WIE), impregnation (IM), and in situ hydrothermal (IHT) methods. Their adsorptive catalytic activities for the removal of VOC’s [Benzene, Toluene, Ethylbenzene and Toluene (BTEX)] in air were tested. The physicochemical properties were investigated by XRD, FTIR, SEM, XPS, and low-temperature N2 adsorption. The results indicate that the catalytic performance of Co-ZSM-5 for VOC’s abatement is effective and the synthesis methods reasonably influence the catalytic activity of Co-ZSM-5. Among three samples prepared by three different methods, the catalyst synthesized by the hydrothermal method possesses the highest adsorptive catalytic activity for BTEX oxidation. The optimized contact time was 60 min. The catalytic activities of the prepared catalysts are varied in the order of IHT > IM > WIE based on the combined removal capacity 59.24 > 34.46 > 23.82 (mg/g). For the Co-ZSM-5 WIE catalysts, the procedure has an evident effect on their catalytic performance. For example, the WIE catalysts prepared with cobalt chloride (II) by ion exchange have a higher acidity and surface area than the catalyst prepared with cobalt chloride (II) by impregnation method but less cobalt content. The excellent performance of IHT catalysts may be endorsed to the better availability of the oxidized form (Co3+), due to high content, higher surface area and acidity. Moreover, the Co-ZSM-5 catalyst synthesized by the IHT method shows high stability after being used.

Influence of the nature and environment of manganese in Mn-BEA zeolites on NO conversion in selective catalytic reduction with ammonia.

Manganese-containing BEA zeolites, MnxSiBEA (x = 1-4 wt%) and Mn(I.E.)AlBEA, were prepared by a two-step post-synthesis method and a conventional wet ion-exchange, respectively, and applied as catalysts in the selective catalytic reduction of NO with ammonia (NH3-SCR). The physicochemical analysis of zeolite properties by high-energy-resolution fluorescence-detected XANES (HERFD-XANES) and X-ray emission spectroscopy (XES) uncovered that the coordination, geometry and oxidation state of Mn species are strongly related to the preparation method. Additionally, the study of catalyst acidity by FTIR spectroscopy with CO and pyridine probe molecules provided important insight into the number and type of acidic centres present on the catalyst surface. The catalytic results revealed that NO conversion depended on the state and content of Mn. The zeolites obtained by the two-step post-synthesis method and with a low Mn content were very active in the medium temperature range (NO conversion ∼100%) with simultaneous high selectivity to N2 due to the presence of isolated, framework Mn(iii) and Mn(ii) species. The N2O formation was especially high in the case of catalysts containing extra-framework polynuclear Mn species and negligible in the case of Mn(I.E.)AlBEA containing predominantly isolated, extra-framework Mn(ii) species.

Esterification of oleic acid with ethanol in the presence of Amberlyst 15

Biodiesel is a promising cleaner burning, less toxic and renewable energy carrier. It is made primarily by transesterification of refined vegetable oils, but biodiesel from these sources are becoming more expensive. Therefore, alternative raw materials are being evaluated, but a major difficulty in the production of biodiesel from these alternative feedstocks is the high concentrations of free fatty acids. This is mainly due to the saponification reaction which occurs with the most commonly used alkali catalysts. Therefore in this work a parameter screening of the esterification of oleic acid, a free fatty acid, with ethanol in the presence of the heterogeneous acid catalyst Amberlyst 15 wet ion exchange was conducted with the intent to produce biodiesel. The parameters screened were reaction temperature, catalyst amount and the ratio between moles of alcohol and moles of fatty acid while the reaction time was set to 6 h. It was found that higher temperature and catalyst amounts increased conversion; however, the ratio between moles of alcohol and moles of fatty acid that gave the highest final conversion was 1:1. The highest Biodiesel yield obtained was 53%. In addition a reuse test of the catalyst was in order to test its recyclability; however, the catalyst presented a reduction in its activity after a single use.

Zn‐HZSM‐5 catalysts for methane dehydroaromatization

The nature of the active species in Zn‐containing HZSM‐5 catalysts was investigated by preparing Zn‐HZSM‐5 via three different synthetic approaches: wet ion exchange, wet impregnation, and core–shell synthesis. By investigating the impact of the preparation methods on the distribution of Zn species, and studying the catalytic performance of the resulting materials in methane dehydroaromatization (DHA), it was shown that metallic Zn0 nanoclusters inside the zeolite micropore constituted the most active species for DHA, but get irreversible loss from the catalyst via evaporation at the high‐temperature conditions of DHA. In contrast, Zn2+ anchored at the exchange sites of the zeolite were the most stable species, but provided little to no aromatization activity. As a result, and counter to previous reports in the literature, it was concluded that Zn/HZSM‐5 was not a suitable catalyst for non‐oxidative methane dehydroaromatization. Nonetheless, the study confirmed that well‐dispersed metal species inside the zeolitic micropores were critical for aromatization activity of zeolite‐based catalysts. © 2016 American Institute of Chemical Engineers Environ Prog, 35: 334–344, 2016

Catalytic decomposition of N2O over Fe-ZSM-11 catalysts prepared by different methods: Nature of active Fe species

A series of Fe-ZSM-11 catalysts were prepared by different methods and tested in N2O decomposition. First, Fe-ZSM-11 catalysts with different Si/Al ratios (15, 25, 36) were prepared by wet ion exchange. The Fe content and catalytic activity were highest for the catalyst with Si/Al ratio 15. Additional Fe-ZSM-11 catalysts with higher Fe contents were prepared by semicontinuous ion exchange or by using alkaline-treated ZSM-11 as the precursor for wet ion exchange. While the catalyst prepared by semicontinuous ion exchange showed low activity, the catalyst prepared using alkaline-treated ZSM-11 turned out to be the most active in this study. Relevant characterization was conducted using X-ray diffraction, X-ray fluorescence, inductively coupled plasma, N2 adsorption–desorption, scanning electron microscopy, transmission electron microscopy, ultraviolet–visible spectroscopy, 57Fe Mössbauer spectroscopy, magnetization tests, and X-ray photoelectron spectroscopy. Our data indicate that small FeOx nanoparticles and large iron oxide particles are the predominant Fe species, and small FeOx nanoparticles with low nuclearity are the active Fe species.

CoZSM-11 catalysts for N2O decomposition: Effect of preparation methods and nature of active sites

CoZSM-11 catalysts prepared using different methods (i.e., wet ion exchange, buffered ion exchange, semi-continuous ion exchange, and impregnation) were tested in N2O decomposition. For CoZSM-11 catalysts prepared by wet ion exchange, the activity increased with the decrease of the Si/Al ratio. Even higher activities can be achieved using catalysts prepared by buffered ion exchange or semi-continuous ion exchange. In contrast, CoZSM-11 prepared by impregnation was the least active. The catalysts were characterized by XRD, N2 sorption, ICP, 27Al MAS NMR, H2-TPR, XPS, and UV–vis DRS. It was concluded that isolated Co2+ cations, in particular α-type Co2+, were active sites, whereas the CoOx species obtained by impregnation was much less active. The catalytic performance of CoZSM-11 and CoZSM-5 was compared as well.

Effective catalytic decomposition of nitrous oxide over highly active and stable bimetallic CoIn-mordenite zeolite

In this study, a bimetallic CoIn-mordenite (MOR) catalyst was prepared via simple wet ion exchange, and its ability to decompose nitrous oxide (N2O) was examined. The incorporation of a trace amount of In into Co-MOR catalyst greatly enhanced its catalytic activity and stability. CoIn-MOR decomposed more than 90% of N2O at 450 °C under simulated conditions of typical nitric acid emissions, and high activity was maintained for longer than 100 h under these strict conditions. The excellent activity of the bimetallic CoIn-MOR catalyst was attributed to strong synergistic effect between In and Co, which re-located cobalt oxides into β ion exchange sites. Those β-type Co ions are the most active sites for N2O decomposition due to the cooperation of N2O splitting by two neighboring Co ions in MOR. Higher amount of surface NOx species are in situ formed, which facilitate the removal of atom O and result in NO-assisted N2O decomposition and greatly improves the activity. Moreover, extended X-ray absorption fine structure analysis indicated that β-type Co ions exhibited stronger coordination to framework oxygens after. In addition, preventing their migration into CoOx clusters. Thus, high activity was maintained.

Fe‐Beta catalysts prepared by heating wet ion exchange and their catalytic performances on N2O catalytic decomposition and reduction

ABSTRACTA heating wet ion exchange method was successfully used to synthesize Fe‐beta catalysts by controlling preparation conditions. The iron loading of Fe‐beta catalysts increased from 0.88% to 16.56% with raising the ion exchange temperature from 20 to 90 °C. Their catalytic activities for N2O decomposition and N2O reduction by NH3 were evaluated. The activity results show that the catalyst prepared at 80 °C (Fe‐beta‐80 °C) could achieve complete N2O decomposition at 480 °C and N2O reduction by NH3 at 375 °C. The iron species of catalysts were further characterized by X‐ray diffraction, transmission electron microscopy (TEM), UV–vis, H2 temperature programmed reduction, and NH3 temperature programmed desorption techniques. The characterization results indicate that related high content of isolated Fe3+ ions and oligonuclear Fe3+xOy clusters existed in the Fe‐beta‐80 °C catalyst, which contributed to the high catalytic activity. Moreover, after the reaction of more than 100 h, Fe‐beta‐80 °C catalyst has no obvious deactivation under simulated emission conditions. The presence of O2 (5%) reduced N2O conversion only to a small extent, whereas NO (1000 ppm) promoted the N2O decomposition over Fe‐beta‐80 °C. © 2013 Curtin University of Technology and John Wiley & Sons, Ltd.

Direct Decomposition of N2O Emitted from Nitric Acid Plant Tail Gases Using Noble Metal Supported Mordenite-Zeolite Catalysts∗

Abstract Mordenite based catalysts for direct decomposition of N2O have been successfully prepared and their direct decomposition performance characterized at the operating temperature of 300–400 °C commonly encountered in the nitric acid plants tail gases. The catalyst was prepared in 2 steps: 1. Precursor wet ion exchange, 2. Precursor impregnation. In addition to the previous contribution, it is shown here that the bimetallic Rh-, Pd-, Ir-Fe-MOR catalysts thus prepared exhibited an excellent N2O decomposition performance: total conversion efficiency of Rh-Fe-MOR catalyst has been achieved at 400 °C and between 7500 h−1 and 10 000 h−1 space velocity.

Fabrication and Characterization of Bimetallic Mordenite-Zeolite Catalysts for Low Temperature Direct Decomposition of N2O Emitted from Nitric Acid Plants∗

Abstract In this research, the mordenite based catalysts for direct decomposition of N2O have been prepared and characterized for their direct decomposition performance at the operating temperature of 300–550 °C commonly encountered in the nitric acid plants tail gases. The zeolite catalyst was prepared by 2 steps: 1. Precursor wet ion exchange, 2. Precursor impregnation. The bi-metallic catalyst thus prepared shows an excellent N2O decomposition performance. The total conversion efficiency of Pt-Fe-MOR catalyst has been achieved at 390 °C. XPS analysis confirmed platinum on mordenite supports in two forms: PtO and PtO2 species interact with oxygen ions at the metal/support interface. Deposition of Pt as a promoter on the surface of Fe-mordenite results in a considerable enhancement of catalytic activity.

Study on Catalytic Decomposition of N<sub>2</sub>O over Modified Zeolites

A series of Beta, ZSM-5 and MCM-22 zeolites modified with metal ions (such as Fe 3+ , Co 2+ , Ce 3+ , Ni 2+ and Cu 2+ ) for catalytic decomposition of N2O were prepared by using wet ion exchange method. The effects of different metal ions, the contents of metal ions and silicon aluminum ratio on catalytic decomposition activities of N2O were investigated, respectively. The results indicated that Beta with a SiO2/Al2O3=30 and 1% Fe 3+ have better catalytic decomposition activities to N2O, the completed catalytic decomposition temperature to 35% N2O in the condition of 4000 h-1 GVSH is 350 0 C.

Investigation of nitrous oxide decomposition over highly active and stable bimetallic CoFe-MOR zeolite catalyst: effective removal and mechanism study

In this study, monometallic Co-mordenite (MOR) and bimetallic CoFe-MOR catalysts were prepared via simple wet ion exchange and tested for N2O decomposition. Strong promotion effect of Fe on the activity and stability of Co ions in the zeolites was observed. To investigate the origin of this promotion effect, X-ray diffraction, H2-temperature programmed reduction, UV-Vis spectroscopy, extended X-ray absorption fine structure analysis, and N2O temperature-programmed desorption were used to characterize the bimetallic and monometallic catalysts. The characteristic results indicated that higher contents of Co ions located at β sites after Fe addition provided cooperation on N2O splitting by two neighboring Co ions. Consequently, a greater amount of surface NOx species were formed in situ and were more strongly bonded to the catalyst, facilitating the removal of O and increasing the activity. Moreover, extended X-ray absorption fine structure analysis indicated that β-type Co ions exhibited stronger coordination to framework oxygen after Fe addition, and higher exchange level was obtained in the bimetallistic CoFe-MOR. Both of them contribute to prevent the relocation of Co2+ ions to form cobalt oxides, thus, high activity was maintained. Consequently, the CoFe-MOR catalyst demonstrates a superior catalytic activity and a high durability in N2O decomposition, showing great potential as a cost-effective catalyst for N2O elimination in future applications.

N2O catalytic reduction by NH3 over Fe-zeolites: Effective removal and active site

A series of Fe exchanged zeolites (MOR, USY, BEA and ZSM-5) were prepared by wet ion exchange and tested for N2O catalytic reduction by NH3. Fe-MOR exhibits the highest activity and this is attributed to its highest content of isolated Fe3+ ions and little Fe(III)xOy clusters, since isolated Fe3+ ions are the active species for N2O reduction while Fe(III)xOy clusters inhibit N2O dissociation due to strong NH3 adsorption. Moreover, Fe-MOR not only achieved N2O and NO simultaneously reduction at a very low temperature (700 K) but also showed good durability under simulated conditions at a typical nitric acid plant.