The contact mass in the Rochow reaction was analyzed to understand catalyst deactivation during the reaction. Changes in crystalline structure, particle surface morphology, and the elemental composition of the contact mass were measured by XRD, SEM, EDX, and XRF, respectively, at four different reaction conversions. The results indicate that the main reason for contact-mass deactivation is copper enrichment on the surface of silicon. Coke deposition may hamper Cu diffusion and result in the copper enrichment.