Systematic study of the crystallization process of CrAPO-5 using in situ high resolution X-ray diffraction

Abstract

a Chromium substituted nano-porous aluminophosphate (CrAPO-5) was investigated to discuss the effect of Cr 3+ ions on the crystallization kinetics and crystal structure parameters by in situ time-resolved high resolution X-ray powder diffraction (HRXRPD). Results showed that the introduction of Cr 3+ into pure AlPO 4 -5 influenced both the crystallization velocity and structural parameters of the resultant AFI. The presence of Cr 3+ ions can severely retard the crystallization of AFI. The more Cr 3+ ions in the gels, the stronger inhibitory effect would be. A kinetic analysis of the crystallization of CrAPO-5 was performed. A fair linear relationship between the activation energy and Cr 3+ content was concluded. The calculated Avrami exponent n was in the range of 1-1.4, implying a similar 1D growth mechanism to that of AlPO 4 -5.The extracted structural parameters showed obvious crystal expansion, which might be caused by the trapping of Cr 3+ ions in the framework. However, this influence on the structural parameters was limited.The a (¼b) parameters increased to a maximum with chromium content, which is similar to the influence on the crystal growing velocity. The grain size variation of AFI differed from other metal substituted aluminophosphate molecular sieves, which implied a different state of chromium in the AlPO 4 -5 framework. The time-resolved HRXRPD proves to be a direct and efficient method to reveal the influence of Cr 3+ ions on the crystallization and shows indirect evidence on the state of Cr 3+ in the crystalized CrAPO-5.

Conjugated Microporous Polymers for Catalytic CO2 Conversion

“…Owing to their ability to coordinate with the O atom of epoxides (Scheme 2‐i), Lewis acid metal sites such as Zn 2+ , Co 2+ , Al 3+ have demonstrated good performance in catalyzing the cycloaddition of CO 2 to epoxides. Numerous metalated CMPs with coordination units such as porphyrin, [ 76 ] salen, [ 9 ] pyridine [ 82 ] ( Figure ) have therefore been designed over the years to exploit this approach.…”

Highly efficient conversion of glycerol and t-butanol to biofuel additives over AlPO solid acid catalyst under microwave irradiation technique: kinetic study

“…The particle sizes (D) of all the samples were calculated from full-width at half-maximum intensity (FWHM) according to the Debye-Scherrer equation (from PXRD) [44]. i.e., particle size (D in nm), full-width at halfmaximum (FWHM = β), wavelength of X-ray (λ = 0.154 nm), diffraction angle (θ) and dimensionless factor (k = 0.94) which is nearly equal to unity.…”

“…In addition, clear cut small particle size and high surface area samples are attained in hot condition compared to the samples prepared in cold[27,40]. Thus, amorphous and mesoporous nature of the catalytic materials have been clearly shown by weak angle diffraction peaks of PXRD patterns.The particle sizes (D) of all the samples were calculated from full-width at half-maximum intensity (FWHM) according to the Debye-Scherrer equation (from PXRD)[44].…”