  In this paper we establish some convergence results for Riemann-Liouville,
Caputo, and Caputo-Fabrizio fractional operators when the order of
differentiation approaches one. We consider some errors given by $\left|\left|
D^{1-\al}f -f'\right|\right|_p$ for p=1 and $p=\infty$ and we prove that for
both Caputo and Caputo Fabrizio operators the order of convergence is a
positive real r, 0<r<1. Finally, we compare the speed of convergence between
Caputo and Caputo-Fabrizio operators obtaining that they a related by the
Digamma function.
