Power of Attorney for Ecovyst Inc. Director

This filing is an Exhibit 24.1, a Power of Attorney document, for Patti A. Humble, an officer and/or director of Ecovyst Inc. The document appoints Joseph S. Koscinski as attorney-in-fact to prepare and execute necessary SEC filings, including Forms 3, 4, and 5, related to Section 16 of the Securities Exchange Act of 1934. This grants Koscinski the authority to handle electronic filings, obtain necessary codes and passwords, and perform any actions deemed beneficial or legally required. The Power of Attorney remains effective until Humble is no longer required to file these forms, unless earlier revoked. The document was signed on May 8, 2026, with the signature date on the filing itself being May 26, 2026.