X0306 4 2022-11-16 0 0001708035 Ecovyst Inc. ECVT 0001717992 Koscinski Joseph S. C/O ECOVYST INC. 300 LINDENWOOD DRIVE MALVERN PA 19355 0 1 0 0 See Remarks Common Stock 2022-11-16 4 M 0 19861 1.88 A 473947 D Stock Option (right to buy) 1.88 2022-11-16 4 M 0 4965 0.00 D 2017-11-01 2025-11-01 Common Stock 4965 0 D Stock Option (right to buy) 1.88 2022-11-16 4 M 0 4965 0.00 D 2019-11-01 2025-11-01 Common Stock 4965 0 D Stock Option (right to buy) 1.88 2022-11-16 4 M 0 9931 0.00 D 2019-11-01 2025-11-01 Common Stock 9931 0 D The shares reported on this Form 4 are subject to a lock-up agreement between the reporting person, Goldman Sachs & Co. LLC, Deutsche Bank Securities Inc. and Credit Suisse Securities (USA) LLC, dated November 14, 2022 (the "Lock-Up Date") pursuant to which the remaining shares reported in Table 1 of this Form 4 cannot be sold for 90 days following the Lock-Up Date. Vice President, Secretary, and General Counsel /s/ Joseph S. Koscinski 2022-11-18