Formaldehyde Synthesis by Methanol Oxidation Using Platinised Oxides Catalysts

The main purpose of this study is to investigate the performance of platinised
silicon dioxide and titanium (IV) oxide catalysts for oxidation of methanol to
formaldehyde at room temperature (25 °C). The reaction was carried out using 100 mL of
methanol (2.53 mol) in the presence of powdered (150 mg) catalyst. Samples were drawn
at time intervals of 0, 10 20, 60, 90 and 120 minutes and the reaction was conducted up to
120 hours. Formaldehyde concentrations were determined by reacting 5 ml sample
solution with the Hantzsch reagent. The complex formed in the samples were analysed
using a UV Spectrophotometer. The amountof formaldehyde formed depends on the type
of catalyst used. When 0.1 % Pt on silicon dioxide catalyst used, 0.012 mmol of
formaldehyde was formed from 2.53 mol methanol after 60 minutes of reaction. Whereas
using the 0.3 % Pt on silicon dioxide catalyst, 0.016 mmol of formaldehyde was formed.
In the presence of 0.1 %, 0.3 %, 0.5 % and 1.1 % Pt on titanium (IV) oxide catalysts,
0.020, 0.032, 0.044 and 0.020 mmol of formaldehyde was formed, respectively. The
percentage conversions of methanol using 0.1 %, 0.3 %, 0.5 % and 1.1 % Pt on titanium
(IV) oxide catalysts are 0.0008, 0.0013, 0.0017 and 0.0008 %, respectively. The activity
of the catalyst can be ranked in order of 0.5 % Pt on titanium (IV) oxide followed by 0.3
% Pt on titanium (IV) oxide, 0.1 % Pt on titanium (IV) oxide, 0.5 % Pt on silicon dioxide
and 0.5 % Pt on silicon dioxide. The titanium (IV) oxide provides better support for
platinum to create active sites for reactions. The best platinum loading is approximately
0.5 %. The formaldehyde yields were found to be decreased when elevating the reaction
temperatures from 30 °C to 40 °C. The activation energy is 34 kJ/mol and the
corresponding frequency factor is 0.26 (mol/L)"075s"1 for this reaction temperature range.
From the economic potential of view, the costs ofproduced catalysts are lower than silver
catalyst.