STARTING POINT: (not sure how you are running your experiment exactly)
Assuming that you are at saturation concentration (i.e. zeroth order decomposition). The rate of reaction can be approximated by:
r = k(T)
Where k(T) is the rate constant which varies with time
Using the Arrhenius Law:
ln(k) = a + b/T
where a and b are constants defined by: a = ko (collision frequency), b = Ea/R (thermal activation energy)
Since the rate of reaction is the change in concentration with respect to time, collect the concentrations at each interval and define k by:
k = (C1 - C0)/30 (where C1 is the current measured concentration and C0 is the previous concentration).
Then plot ln(k) vs. 1/T to determine the rate of reaction at various temperatures.