Synthesis of SAPO-34 templated by diethylamine: Crystallization process and Si distribution in the crystals

Liu, Guangyu; Tian, Peng; Zhang, Ying; Li, Jinzhe; Xu, Lei; Sun, Meng; Liu, Zhongmin

doi:10.1016/j.micromeso.2008.01.030

Cited by 126 publications

(111 citation statements)

References 38 publications

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“…This means that the occurrence of desalination phenomenon during the post treatment mainly removed Si atoms from Si-rich areas, which is contradictory to one common sense that oxalic acid is usually used as a dealumination reagent. Considering rough external surface of the treated samples and previous finding of 'Si enrichment on the SAPO-34 surface' [19], we can come to a conclusion that oxalic acid treatment caused an entire corrosion of external crystal surface, not merely occurring on the Si sites. Elemental analysis was used to detect the change of the sample compositions, and the results are presented in Table 2.…”

Section: Resultsmentioning

confidence: 62%

“…However, our previous results showed that the crystallization yield of SAPO-34 dropped with decreasing Si content in the synthesis gel, especially in the range of low Si content. And, the Si distribution in crystals was not homogeneous, showing a gradual increase from the core to the shell; i.e., the Si environment was only Si(4Al) in the initially formed core and other Si environments would appear with the growth of crystal size during the crystallization [19]. This implies the unnecessary to crystallize a special SAPO-34 catalyst with low Si content in order to obtain good MTO results.…”

Section: Introductionmentioning

confidence: 99%

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An effective route to improve the catalytic performance of SAPO-34 in the methanol-to-olefin reaction

Liu¹,

Tian²,

Xia³

et al. 2012

Journal of Natural Gas Chemistry

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Section: Resultsmentioning

confidence: 62%

Section: Introductionmentioning

confidence: 99%

An effective route to improve the catalytic performance of SAPO-34 in the methanol-to-olefin reaction

Liu¹,

Tian²,

Xia³

et al. 2012

Journal of Natural Gas Chemistry

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“…This is similar to what we have found in SAPO-34 crystals templated by diethylamine. 24 Moreover, the increase of solid yields and the heterogeneity of crystal sizes shown by SEM suggest the occurrence of secondary nucleation during the crystallization process. The newly formed crystals, possessing higher Si content in the core as compared with that of the original crystals, also have an increasing Si content from the core to the surface.…”

Section: Resultsmentioning

confidence: 98%

Investigation of the Crystallization Process of SAPO-35 and Si Distribution in the Crystals

Tian

et al. 2013

J. Phys. Chem. C

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“…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: 98%

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

158

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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Synthesis of SAPO-34 templated by diethylamine: Crystallization process and Si distribution in the crystals

Cited by 126 publications

References 38 publications

An effective route to improve the catalytic performance of SAPO-34 in the methanol-to-olefin reaction

An effective route to improve the catalytic performance of SAPO-34 in the methanol-to-olefin reaction

Investigation of the Crystallization Process of SAPO-35 and Si Distribution in the Crystals

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

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