TY - JOUR
T1 - The role
AU - Warzywoda, Juliusz
AU - Dixon, Anthony G.
AU - Thompson, Robert W.
AU - Sacco, Albert
AU - Suib, Steven L.
N1 - Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.
PY - 1996
Y1 - 1996
N2 - The role of the dissolution of silicic acid powders in alkaline aluminosilicate synthesis mixtures in the crystallization of mordenite was investigated. Three different as-received lots of silicic acid (Aldrich lots 01807PW (lot A), 04720KX (lot B), and 18913LY (lot C)) were used to synthesize mordenite from the same initial batch composition (4.32 Na2O : Al2O3 : 19 SiO2 : 293.6 H2O). Different overall crystallization times (lot A ≈ 10 h, lots B and C ≈ 28 h), conversion rates at the 50% point (lot A ≈ 44% h-1 lots B and C ≈ 12% h-1) and maximum crystal sizes (lot A = 10-15 μm, lot B = 35-40 μm, lot C = 30-35 μm) were observed. The prismatic crystal morphologies were the same in all cases. Heat treatment of as-received lots A and B in air at 550°C before syntheses resulted in about 6- and 2-fold decreases of mordenite conversion rates, respectively; and in about 6- and 2-fold increases of mordenite crystal sizes, respectively. Heat treatment of asreceived lot C in air at 850°C resulted in about a 6-fold decrease of mordenite conversion rate and in about a 6-fold increase of mordenite crystal size. Induction periods and overall crystallization times also increased in these cases. Large crystals of mordenite with sizes of up to 250 μm were obtained using lot C heat treated at 850°C. These results reflect different silica dissolution rates that were correlated with the variation of specific surface area and average pore diameter of silicic acid powders. The dissolution of silicic acid in the investigated crystallization of mordenite intervened in the rate-determining step for nucleation and growth of mordenite crystals.
AB - The role of the dissolution of silicic acid powders in alkaline aluminosilicate synthesis mixtures in the crystallization of mordenite was investigated. Three different as-received lots of silicic acid (Aldrich lots 01807PW (lot A), 04720KX (lot B), and 18913LY (lot C)) were used to synthesize mordenite from the same initial batch composition (4.32 Na2O : Al2O3 : 19 SiO2 : 293.6 H2O). Different overall crystallization times (lot A ≈ 10 h, lots B and C ≈ 28 h), conversion rates at the 50% point (lot A ≈ 44% h-1 lots B and C ≈ 12% h-1) and maximum crystal sizes (lot A = 10-15 μm, lot B = 35-40 μm, lot C = 30-35 μm) were observed. The prismatic crystal morphologies were the same in all cases. Heat treatment of as-received lots A and B in air at 550°C before syntheses resulted in about 6- and 2-fold decreases of mordenite conversion rates, respectively; and in about 6- and 2-fold increases of mordenite crystal sizes, respectively. Heat treatment of asreceived lot C in air at 850°C resulted in about a 6-fold decrease of mordenite conversion rate and in about a 6-fold increase of mordenite crystal size. Induction periods and overall crystallization times also increased in these cases. Large crystals of mordenite with sizes of up to 250 μm were obtained using lot C heat treated at 850°C. These results reflect different silica dissolution rates that were correlated with the variation of specific surface area and average pore diameter of silicic acid powders. The dissolution of silicic acid in the investigated crystallization of mordenite intervened in the rate-determining step for nucleation and growth of mordenite crystals.
KW - Crystallization kinetics
KW - Large zeolite crystals
KW - Mordenite
KW - Nucleation control
KW - Zeolite synthesis
UR - http://www.scopus.com/inward/record.url?scp=0030082552&partnerID=8YFLogxK
U2 - 10.1016/0144-2449(95)00101-8
DO - 10.1016/0144-2449(95)00101-8
M3 - Article
AN - SCOPUS:0030082552
VL - 16
SP - 125
EP - 137
JO - Zeolites
JF - Zeolites
SN - 0144-2449
IS - 2-3
ER -