This paper studies two different multiplexing problems for Device to Device (D2D) asynchronous communications with different multi-carrier modulations. Several D2D pairs may be multiplexed on the same Resource Blocks (RB) if they are jointly able to reach a high Signal to Interference plus Noise Ratio (SINR). In asynchronous communications, inter-channel interference (ICI) is present on top of co-channel interference, and the multiplexing problem can consequently not be split per RB since RB are no longer orthogonal. In this paper, we derive the system model that takes into account ICI and then study the maximum multiplexing problem. Two heuristics based on the Frobenius and the infinity norms that lead to lower bounds on the multiplexing gain are proposed. Then, the maximum sum SINR problem is studied with the infinity norm, showing that higher rates are achieved with Filter Bank Multi-Carrier (FBMC) modulation than with Orthogonal Frequency Division Multiplex (OFDM).