Synthesis of SAPO-34: high silicon incorporation in the presence of morpholine as template

Prakash, Anand; Unnikrishnan, Sneha

doi:10.1039/ft9949002291

Cited by 184 publications

(169 citation statements)

References 4 publications

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“…7). At 10 h, four weak resonance signals appeared at À94.4, À99.6, À104.3 and 109.8 ppm, which can be assigned to Si(3Al), Si(2Al), Si(1Al) and Si(0Al), respectively, [13][14][15] suggesting that small amount of Si atoms are incorporated into the SAPO-34 framework by the substitution mechanism in this stage.…”

Section: Nmr Analysismentioning

confidence: 99%

“…27 Al NMR showed a typical NMR peak at 38 ppm due to aluminum in tetrahedral environment of the SAPO-34 framework. 31 P and 29 Si NMR each showed a single resonance at À27.4 and À90.5 ppm, respectively, typical of P(Al) and Si(4Al) environments in the SAPOs [14,15,[20][21][22][23]. With the consumption of the amorphous materials with time, the resonance peaks of tetrahedral aluminum, P(Al) and Si(Al) in the SAPO-34 lattice increased rapidly with the decrease of the resonance peaks of the amorphous materials, indicating higher crystallinity of the samples.…”

Section: Infrared Spectral Analysismentioning

confidence: 99%

“…4. The various vibration frequencies (Table 1) have been assigned, based on relevant reports [14,15].…”

Section: Infrared Spectral Analysismentioning

confidence: 99%

“…The Brønsted acid sites of SAPO-34 are attributed to the introduction of Si atoms into the neutral AlPO 4 -34 framework. From the viewpoints of the references [12][13][14][15][16], it is proposed that Si atoms incorporate into the AlPO 4 -34 structure by two different substitution mechanisms: the first, denoted as SM1, is that the Si substitution for phosphorus form Si(4Al) entities, which gives rise to negative charges for forming Brønsted acid sites; the second mechanism (SM2) is the double substitution of neighboring aluminum and phosphorus by two silicon atoms to form Si(nAl) (n ¼ 3-0) structures, which leads to the formation of stronger Brønsted acid sites. The structure, acidity and catalytic property of SAPO-34 depend on the number and distribution of Si in the framework [16][17][18], which is closely related to the synthesis process, i.e., to the crystallization and Si incorporation mechanisms.…”

Section: Introductionmentioning

confidence: 99%

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Crystallization and Si incorporation mechanisms of SAPO-34

Tan

Liu

Bao

et al. 2002

Microporous and Mesoporous Materials

284

193

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Section: Nmr Analysismentioning

confidence: 99%

Section: Infrared Spectral Analysismentioning

confidence: 99%

“…4. The various vibration frequencies (Table 1) have been assigned, based on relevant reports [14,15].…”

Section: Infrared Spectral Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Crystallization and Si incorporation mechanisms of SAPO-34

Tan

Liu

Bao

et al. 2002

Microporous and Mesoporous Materials

284

193

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“…31 P MAS NMR indicates a single signal at -28 ppm indicative of one distinguishable type of tetrahedral phosphorous (see Figure 12A). 27 Al MAS NMR spectrum exhibits a strong peak at 35 ppm, which corresponds to Al in tetrahedral environments in the framework, [18] while the signal at 10 ppm has been assigned to five-coordinated aluminium in the framework of SAPO-34 with water molecules (see Figure 12B). [19] Finally, 29 Si MAS NMR spectrum indicates that part of silicon atoms are selectively replacing phosphorous atoms in the framework (see signal at -91 ppm in Figure 12C), while the signal at -111 ppm reveals that Si-rich domains are also present in the final solid.…”

Section: 3-direct Synthesis Of Cu-sapo-34 Using Different Amounts mentioning

confidence: 99%

Rational direct synthesis methodology of very active and hydrothermally stable Cu-SAPO-34 molecular sieves for the SCR of NOx

Martínez-Franco

Moliner

Franch

et al. 2012

Applied Catalysis B: Environmental

159

103

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A one-pot direct synthesis of Cu-SAPO-34 has been achieved that allows more than 90% yield in the material synthesis. By this method it is easy to control the Cu-loading in the Cu-SAPO-34. It is presented that a maximum in hydrothermal stability with very high activity for NOx SCR with NH 3 is obtained for an optimum Cu loading. KeywordsOne-pot synthesis, silicoaluminophosphate, SAPO-34, selective catalytic reduction (SCR), nitrogen oxides (NOx) Highlights-Rational direct synthesis of Cu-SAPO-34 by using the co-directing templates.-Easy control of Cu-loading in Cu-SAPO-34 materials, and very high solid yields.-High activity and stability for SCR of NOx. In fact, the SCR of NOx experiment described by Xiao was performed on the sample with Si/Al ratio of 4.1 under mild conditions (low space velocity), and the stability of the synthesized samples under hydrothermal treatments was not studied. In addition to SSZ-13, the chabazite molecular sieve can be synthesized as silicoaluminophosphate form, . Cu-exchanged SAPO-34 has also been shown as a very stable and active material for SCR of NOx [14]. In the last years, some groups have attempted the direct preparation of Cu-SAPO-34 in order to achieve an inexpensive and more efficient synthetic route for this metal-substituted material [15].In those cases morfoline and copper oxide were used as organic structure directing with the tetraethylenepentamine (TEPA, 99%wt, Aldrich). This mixture was stirred for 2 hours until complete dissolution. Secondly, distilled water and phosphoric acid (85% wt, Aldrich) were added and stirred during 5 minutes. Third, alumina (75%wt, Condea) 7 and silica (Ludox AS40 40%wt, Aldrich) sources were introduced in the gel mixture.Finally, diethylamine (DEA, 99%wt, Aldrich) and SAPO-34 seeds (5%wt of expected final yield), if required, were added in the gel, and the mixture was stirred during 30 minutes. The resulting gel was transferred to an autoclave with a Teflon liner, and heated at 150ºC under static conditions during the required time (see experimental conditions for each sample in Table 1, Table 3, or Table 4). Crystalline products were filtered and washed with abundant water, and dried at 100ºC overnight. The samples were calcined at 550ºC in air to properly remove the occluded organic species. washed with distilled water, and dried at 100ºC overnight. The sample was calcined at 550ºC in air to remove the occluded organic species.In order to perform the Cu ion exchange on this SAPO-34 material, the calcined sample was first washed with NaNO 3 (0.04M), and afterwards, the sample was exchanged at room temperature with a Cu(CH 3 CO 2 ) 2 solution (solid/liquid ratio of 10g/L). Finally, the sample was filtered and washed with distilled water, and calcined at 550ºC for 4 h. 2.2.-CharacterizationX-ray diffraction (XRD) measurements were performed on a multisample Philips X'Pert diffractometer equipped with a graphite monochromator, operating at 40 kV and 45 mA, and usig Cu K α radiation (λ = 0,1542 nm).The chemical analyses were car...

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Direct Crystallization of Silicoaluminophosphates onto the Surface of Open‐Celled SiC Foam

2014

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Silicoaluminophosphates of the framework types CHA (SAPO-34) and AFI (SAPO-5) are deposited onto the surface of open-celled ceramic SiC foam monoliths by direct crystallization. Therefore, a conventional hydrothermal synthesis is carried out in the presence of SiC foam monoliths with pore densities of 10 and 30 PPI, respectively. Moreover, the crystallization time is varied to determine its effect on the coating produced. In all cases, the direct crystallization of the respective SAPO material is successful. Irrespective of the pores density of the ceramic foam a variation of the crystallization time (SAPO-5: 20 h/30 h, SAPO-34:30 h/45 h) does not show any influence on the thickness of the layers produced as suggested by optical microscopy. However, in the case of SAPO-34 these layers are clearly thicker than the layers of SAPO-5, which leads to a partial blockage of the pores of the ceramic foam with a pore density of 30 PPI. As proved by N 2 -sorption measurement, the coatings offer BET surface areas comparable with those reported for pure powder samples.

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Synthesis of SAPO-34: high silicon incorporation in the presence of morpholine as template

Cited by 184 publications

References 4 publications

Crystallization and Si incorporation mechanisms of SAPO-34

Crystallization and Si incorporation mechanisms of SAPO-34

Rational direct synthesis methodology of very active and hydrothermally stable Cu-SAPO-34 molecular sieves for the SCR of NOx

Direct Crystallization of Silicoaluminophosphates onto the Surface of Open‐Celled SiC Foam

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