Abstract Hydrothermally synthesized ZSM-5 zeolites
using tetrapropyl-ammonium bromide (TPA-Br),
Xylitol (Xy) and tetrapropyl-ammonium bromide
+ Xylitol templates; those compared with that
of the parent having the same Si/Al molar ratio (64)
and purchased from Mobil, were characterized with
several physicochemical techniques including N2
adsorption, XRD, TG/DSC, FTIR and pyridine-
FTIR. The effect of various templates on the crystallinity,
crystallites size, surface properties and thermal
stabilities of the produced ZSM-5 were investigated.
ZSM-5 synthesized using TPA-Br + Xy; of
SBET = 393 m2 g–1, exhibited a crystallinity percentage
comprises of 142% when compared with that of
the parent (taken at 100% crystallinity) and measured
as well a crystallites size of 61 nm exceeding that
derived from Xy (41 nm) that measured the lowest
crystallinity percentages (71%), lowest SBET
(303 m2 g–1) and highest yield (65%) between all
samples. The former sample showed high thermal
stability (till 1,000 C) when compared with that
derived from TPA-Br, as illustrated from TG/DSC
thermograms that provided a criteria on decreasing
the pore radius as a result of enclosing appreciable
amounts of TPA+ and Xy inside narrow pores of
ZSM-5. This sample also indicated a hydrophobic
tendency when compared with that devoted from
TPA-Br. Pyridine adsorption measurements showed
that addition of Xy to TPA-Br stimulate the existence
of basic sites in addition to acidic ones (mainly
Bro¨ nsted ones) that was in the middle between that
derived from Xy and TPA-Br templates. More
infomations on the textural properties, morphologies,
vibrational tetrahedral co-ordination T(Si or Al)–O
modes and acidity were evaluated and discussed. |
