UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2025 Ecovyst Inc. Delaware 81-3406833 (State or other jurisdiction of incorporation or organization) 600 Lee Road, Suite 200 Wayne, Pennsylvania 19087 (Address of principal executive offices) (Zip Code) (484) 617-1200 (Registrant's telephone number, including area code) 300 Lindenwood Dr ...