Abstract:This article presents the results of a comprehensive study of copper-exchanged mordenite samples prepared from its ammonia and protonated forms (Si/Al = 10) using two different ion exchange methods: conventional and microwave (MW)-assisted. The protonated H-MOR-10 sample was obtained by calcination of commercial NH4-MOR-10; in this case, a slight degradation of the mordenite framework was observed, but the resulting defects were partially restored after the first ion-exchange procedure of protons for copper io… Show more
“…This result is expected since the SSIE is the most convenient method for controlling the metal amount in the prepared solids, which is in perfect agreement with our previous works [12][13][14]. The ratio of the parent zeolite stated by Zeolyst (CBV024E, Si/Al=15) was decreased in the case of prepared catalysts and that can be attributed to the reproducibility of routine sequential syntheses which may vary from batch to batch [30].…”
Fe-Cu-ZSM-5 and Ce-Fe-Cu-ZSM-5 solids prepared using solid-state ion exchange method (SSIE) were tested in the NH 3 -SCR of NO reaction and were characterized using N 2 physisorption at 77 K, MAS 27 Al magnetic resonance, X-ray diffraction, scanning electron microscopy, EPR spectroscopy and transmission electron microscopy coupled to energy dispersive X-ray spectroscopy in order to follow the effect of Ce addition on the textural and structural properties of Fe-Cu-MFI system as well as the detection of the changes in local environment and state of iron and copper species, and the degradation of the zeolite texture and structure after a severe aging treatment at 850 °C for 5h. Fresh Ce-promoted sample showed better NO conversion up to 450 °C than unpromoted Fe-Cu-ZSM-5 catalyst. An activity loss was observed on aged catalysts, but remaining less pronounced for the catalyst 2 containing Ce. The changes in catalyst structure and texture did not occur during aging while a probable migration of metal active species and change in their coordination has occurred.
“…This result is expected since the SSIE is the most convenient method for controlling the metal amount in the prepared solids, which is in perfect agreement with our previous works [12][13][14]. The ratio of the parent zeolite stated by Zeolyst (CBV024E, Si/Al=15) was decreased in the case of prepared catalysts and that can be attributed to the reproducibility of routine sequential syntheses which may vary from batch to batch [30].…”
Fe-Cu-ZSM-5 and Ce-Fe-Cu-ZSM-5 solids prepared using solid-state ion exchange method (SSIE) were tested in the NH 3 -SCR of NO reaction and were characterized using N 2 physisorption at 77 K, MAS 27 Al magnetic resonance, X-ray diffraction, scanning electron microscopy, EPR spectroscopy and transmission electron microscopy coupled to energy dispersive X-ray spectroscopy in order to follow the effect of Ce addition on the textural and structural properties of Fe-Cu-MFI system as well as the detection of the changes in local environment and state of iron and copper species, and the degradation of the zeolite texture and structure after a severe aging treatment at 850 °C for 5h. Fresh Ce-promoted sample showed better NO conversion up to 450 °C than unpromoted Fe-Cu-ZSM-5 catalyst. An activity loss was observed on aged catalysts, but remaining less pronounced for the catalyst 2 containing Ce. The changes in catalyst structure and texture did not occur during aging while a probable migration of metal active species and change in their coordination has occurred.
“…Surprisingly, the H-MOR catalyst showed the opposite behavior: The lattice of the spent catalyst shrunk compared to the fresh H-MOR. We assume either that the adsorption of NH 3 and the amines at the strong acidic sites led to a contraction of the lattice similar to ion exchange experiments in H-MOR , or that dealumination through steaming, which is more significant for the H-MOR due to its high alumina content, is responsible for the decreased lattice spacing.…”
Mono-, di-, and trimethylamine are
the products of the successive
methylation of ammonia. Using narrow-pore acidic catalysts of the
CHA family like H-SAPO-34 or H-SSZ-13, the formation of the thermodynamically
but bulky trimethylamine can be suppressed due to steric effects;
thus, methylation is stopped at dimethylamine. In this work, the continuous
in situ removal of the byproduct water through the 4 Å wide pores
in an LINDE Type A (LTA) (grown on an α-Al2O3 support) membrane reactor further increased the selectivity
toward the economically desired product dimethylamine by 50%. This
experimental finding can be explained by the release of adsorbed water
blocking the catalytic site. Water removal through the hydrophilic
LTA zeolite membrane allows methanol to adsorb at the acidic catalyst
sites, which in turn accelerates the methylation rate of monomethylamine
to the desired product dimethylamine. Further methylation to trimethylamine
as the thermodynamically most favored product is not possible in narrow-pore
catalysts because of space restrictions, but it takes place in the
12-membered-ring H-Mordenite (H-MOR) catalyst.
“…A similar effect was also observed for a series of Cu/mordenite prepared via the traditional aqueous ion exchange. 35,36 By contrast, the lack of shifts of the diffraction patterns detected in the XRD results of fresh silicalite-1 and Cu/silicalite-1 indicated only copper oxides loaded into silicalite-1 via solid-state impregnation (Supporting Information, Fig. S7).…”
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