The effect of the particle-number projection on the electric quadrupole moment (Q2) of even-even proton-rich nuclei is studied in the isovector neutron-proton (np) pairing case. As a first step, an expression of the electric quadrupole moment, which takes into account the isovector np pairing effect and which conserves the particle-number, is established within the Sharp-BCS (SBCS) method. This expression does generalize the one used in the pairing between like-particles case. As a second step, Q2 is calculated for even-even proton-rich nuclei using the single-particle energies of a Woods-Saxon mean-field. The obtained results are compared with the results obtained in the pairing between like-particles case. It is shown that the np pairing effect, as well as the projection one, is maximal when N=Z.
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