Catalysis Definitions and Calculation
SiliaCat Heterogeneous Catalysts are sol-gel silica-supported catalysts that can be used to replace homogeneous catalysts.
Usually, heterogeneous catalysts supported on a silica matrix are immobilized by post-modification of the inorganic support. These supports, however, present a high degree of leaching due to the poor stability of the immobilized phase. With SiliaCat Heterogeneous Catalysts, the ligand is directly cross linked in an organic-inorganic framework. This results a high degree of stability of the catalysts. Compared to homogeneous catalysts, SiliaCat exhibits a good reactivity and selectivity with one of the major advantages being that the catalyst is eliminated from the reaction mixture by a simple filtration. Forget your purification problems with our SiliaCat catalysts family.
The process for using SiliaCat Heterogeneous Catalysts is outlined in the scheme below.
What is a Turnover Number (TON)?
In catalysis, the term turnover number has two meanings: the number of moles of substrate that a mole of catalyst can convert before becoming inactivated and is the amount of substrate converted per the amount of catalyst used.
In theory, the Ideal catalyst would have an infinite turnover number and would never be consumed. In practice, turnover numbers begin at 100 and can go up to a million, more so in some cases.
What is a Turnover Frequency (TOF)?
A catalyst’s turnover frequency number, or turnover number per time unit, characterizes its level of activity. So the TOF is the total number of moles transformed into the desired product by one mole of active site per hour. The larger the TOF, the more active the catalyst.
TOF = TON/hour
How to Calculate the Amount of SiliaCat Needed Based on Mol %?
One mol % (1 mol %) means 0.01 molar equivalent. If 3 mmol of the substrate is used, then 0.03 mmol of SiliaCat catalyst is required. To determine the weight of the catalyst needed, simply divide this value by the loading of the catalyst. For example, SiliaCat DPP-Pd typical loading is 0.2 mmol/g, so 0.15 g is needed.
Solvent Molar Concentration
A 1.2 M solvent concentration means:
1.2 mmol of substrate per mL of solvent
(or 1.2 mol of substrate per L of solvent)
|Volume of solvent needed =
||mmol of substrate used
molar concentration desired
For example, if 3 mmol of the substrate is used, then, 2.5 mL of solvent is necessary to reach a 1.2 M concentration.