Structure of an aluminosilicophosphate

Ito, Muneyuki; Shimoyama, Yuhei; Saito, Yoshihiko; Tsurita, Y.; Otake, M.

doi:10.1107/s010827018500912x

Cited by 55 publications

(45 citation statements)

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“…In the literature there are two ways for labeling the oxygen atoms within the chabazite topology. [50,51] We use the labeling applied in references [52][53][54][55] as illustrated in Figure 1. Three sites are part of an eight-membered ring connecting two cages, whereas the fourth oxygen atom, O(3), is attached to a six-membered ring and is only in contact with one cage.…”

Section: Resultsmentioning

confidence: 99%

Theoretical Simulations Elucidate the Role of Naphthalenic Species during Methanol Conversion within H‐SAPO‐34

Hemelsoet

Nollet

Speybroeck

et al. 2011

Chemistry A European J

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The role of naphthalenic species during the methanol-to-olefins (MTO) process in a silicoaluminophosphate zeolitic material exhibiting the chabazite topology (H-SAPO-34) has been studied from first principles. These species could either act as active olefin-eliminating compounds or as precursors for deactivating species. Results incorporating van der Waals contributions for finite large clusters point out that successive methylation steps of naphthalenic compounds are feasible. The calculated intrinsic activation barrier is relatively independent of the number of methyl groups already attached on the aromatic compound and is approximately 140 kJ mol(-1). The influence of the composition of the catalyst and hence the acidic strength on the intrinsic chemical kinetics was investigated in detail through comparison with the isostructural high-silicon material. Apparent chemical kinetics, starting from adsorbed methanol on the acid site, were also computed. The initiation steps of the side-chain route starting from a trimethylated naphthalenium ion were also examined. The actual side-chain methylation exhibits a high barrier and hence this mechanism involving methylated naphthalenes is not expected to be an active ethene-eliminating route in H-SAPO-34.

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Section: Resultsmentioning

confidence: 99%

Theoretical Simulations Elucidate the Role of Naphthalenic Species during Methanol Conversion within H‐SAPO‐34

Hemelsoet

Nollet

Speybroeck

et al. 2011

Chemistry A European J

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“…Coordinates for the water atoms O9-O16 in this zeolite, with occupancies ranging from 0.03 to 0.25, are given by Ito et al (1985) in a supplementary publication. Table S38 shows that all other atoms they reported refined to positions for which Á < $ 0.16 Å < $ u eq with respect to R3.…”

Section: H 3 O + áAl 4 Sip 3 O 16mentioning

confidence: 99%

Systematic prediction of new ferroelectrics in space group R3. I

Abrahams

2006

Acta Crystallogr Sect B

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Release 2005/1 of the Inorganic Crystal Structure Database contains 158 entries under the space group R3. The first 81 together with 15 related entries include 52 different structure types, 10 of which represent families that have two or more isostructural members. There are 18 types that satisfy the structural criteria for ferroelectricity with a confidence level that necessarily depends upon the reliability of each structural determination. Among them, (LiTaO3)9.Ta2O5 and the CsCd(NO2) family are known ferroelectrics. The remaining 16 include the high-intensity higher-order harmonic generator II-BaB2O4, not previously recognized as ferroelectric. The other predicted ferroelectrics are Te(OH)6.NaF, the MgSO3.6H2O family, Li3P3O9.3H2O, SeNbF9, Al2(H2PO4)3PO4.6H2O, [Cr(OCN2H4)6].[(Co(NH3)2(NO2)4]3.(H2O)(1.5)], NaZnBr3.5H2O, III-Ag3SI, Tl2S, the Ba3Yb4O9 family, the Fe(10.7)Ru(1.3)As5 family, Sr17Ta10S42, Pb8Sb3 and the Sc7I12C family. Six structures reported in the space group R3 most likely exhibit mirror symmetry, with three experimental confirmations. The other 19 structures are most likely nonpolar, with six experimental confirmations. The capacity for physical property prediction by the remaining ten structures is shown to be in doubt. Thus, 46% of the present 52 inorganic structure types initially determined in the space group R3 and 35% of those currently assigned to R3 more likely exhibit an additional inversion center, mirror or glide plane, strongly exceeding the recently reported error rate of approximately 11% in organic structures.

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“…The acid strength of the catalysts was thus estimated based on the rate of n-butane cracking at 773 K at an n-butane pressure of 4.0 kPa 50) . The cracking of nbutane is a typical reaction that proceeds on Brønsted acid sites, and it is natural that the reaction rate would increase with acid strength.…”

Section: Effect Of Acid Strength On Selectivity Formentioning

confidence: 99%

Propene Production from Ethene and Methane Using Silver- and Proton-exchanged Zeolite Catalysts

Inazu

Koyama

Miyaji

et al. 2008

J. Jpn. Petrol. Inst.

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Two new methods for the catalytic synthesis of propene using solid acid catalysts are presented. The first approach is a new method for the activation of methane, involving conversion of methane to propene over silverexchanged zeolite in the presence of ethene. In the second method, ethene conversion proceeds directly and selectively over proton-exchanged zeolite under the control of a molecular sieving effect.The heterolytic dissociation of methane over silver cationic clusters (Agn ＋ ) in Ag ＋ -exchanged zeolites, leading to the formation of silver hydride (Agn _ H) and CH3 δ＋ species, which reacts with ethene to form propene around 673 K. Using 13 C-labeled methane as a reactant, propene is shown to be a primary product from methane and ethene. Thus, a significant proportion of propene was singly 13 C-labeled ( 13 CC2H6). Under these reaction conditions, H ＋ -exchanged zeolites, such as H _ ZSM-5 do not catalyze the methane con version, only ethene being converted into higher hydrocarbons, such as propene. Ethene is selectively converted to propene over SAPO-34 at 723 K with a yield of 52.2％ and selectivity of 73.3％ at ethene conversion of 71.2％. The high and selective propene yields achieved over SAPO-34 can be attributed to a shape selectivity effect of the small-pore SAPO-34.

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Structure of an aluminosilicophosphate

Cited by 55 publications

References 0 publications

Theoretical Simulations Elucidate the Role of Naphthalenic Species during Methanol Conversion within H‐SAPO‐34

Theoretical Simulations Elucidate the Role of Naphthalenic Species during Methanol Conversion within H‐SAPO‐34

Systematic prediction of new ferroelectrics in space group R3. I

Propene Production from Ethene and Methane Using Silver- and Proton-exchanged Zeolite Catalysts

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