The Heterogenization Of Sulfanilic And Sulfonic Acids And Their Catalytic Activity In The Liquidphase Alkylation Of Phenol
Loading...
Date
2011
Authors
Ali, Tammar Hussein
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
The new mesoporous silica modified with sulfanilic and sulfonic acids was
synthesized by using rice husk ash (RHA) as the silica source. The solid catalysts
were denoted as RHABzSO3H and RHAPrSO3H. The as-synthesized solid catalysts
showed good textural and structural properties. The high–angle XRD diffraction
pattern exhibited diffraction at 2θ which corresponds to amorphous silica. The
absence of sharp peaks suggests the material is not crystalline. The 29Si MAS NMR
showed the presence of T2, T3, Q3 and Q4 silicon centres. The 13C MAS NMR
confirmed that RHABzSO3H had three chemical shifts consistent with the three
carbon atoms of the propyl group and a series of chemical shifts consistent with
the presence of the aromatic ring. The activity of the catalysts for the tert-butylation
of phenol and some substituted phenols and derivatives of alcohol were observed
to be positively influenced with increasing reaction temperature. However, it
was negatively affected with increasing TBA: phenol molar ratio. The highest
catalytic conversion (98 %) was observed over RHAPrSO3H whereas highest
selectivity was for 2-tert-butylphenol followed by 4-tert-butylphenol. The activity of
the catalyst decreased in the order: phenol > o-cresol > m-cresol > p-cresol > 2-
propanol > benzyl alcohol. The homogenous sulfanilic acid (un-supported) was less
active compared to the heterogeneous catalyst. The catalysts were reused three times
in the tert-butylation of phenol at the optimum conditions without significant loss in
the activity.
Description
Keywords
Sulfanilic And Sulfonic Acids , Liquidphase Alkylation Of Phenol