Ecovyst Inc

Report of Independent Registered Public Accounting Firm

To the Board of Directors and Stockholders of Ecovyst Inc.

Opinions on the Financial Statements and Internal Control over Financial Reporting

We have audited the accompanying consolidated balance sheets of Ecovyst Inc. and its subsidiaries (the “Company”) as of December 31, 2024 and 2023, and the related consolidated statements of (loss) income, of comprehensive (loss) income, of stockholders’ equity and of cash flows for each of the three years in the period ended December 31, 2024, including the related notes and schedule I – parent company financial information as of December 31, 2024 and 2023, and for each of the three years in the period ended December 31, 2024 listed in the accompanying index (collectively referred to as the “consolidated financial statements”). We also have audited the Company’s internal control over financial reporting as of December 31, 2024, based on criteria established in Internal Control - Integrated Framework (2013)issued by the Committee of Sponsoring Organizations of the Treadway Commission (COSO).

In our opinion, the consolidated financial statements referred to above present fairly, in all material respects, the financial position of the Company as of December 31, 2024 and 2023, and the results of its operations and its cash flows for each of the three years in the period ended December 31, 2024 in conformity with accounting principles generally accepted in the United States of America. Also in our opinion, the Company did not maintain, in all material respects, effective internal control over financial reporting as of December 31, 2024, based on criteria established in Internal Control - Integrated Framework (2013)issued by the COSO because a material weakness in internal control over financial reporting existed as of that date related to the ineffective design and maintenance of controls over ensuring the proportionate share of the earnings from the Zeolyst Joint Venture, an equity investee underlying the Company’s financial statements, are completely, accurately and timely recorded.

A material weakness is a deficiency, or a combination of deficiencies, in internal control over financial reporting, such that there is a reasonable possibility that a material misstatement of the annual or interim financial statements will not be prevented or detected on a timely basis. The material weakness referred to above is described in Management's Annual Report on Internal Control over Financial Reporting appearing under Item 9A. We considered this material weakness in determining the nature, timing, and extent of audit tests applied in our audit of the 2024 consolidated financial statements, and our opinion regarding the effectiveness of the Company’s internal control over financial reporting does not affect our opinion on those consolidated financial statements.

Basis for Opinions

The Company’s management is responsible for these consolidated financial statements, for maintaining effective internal control over financial reporting, and for its assessment of the effectiveness of internal control over financial reporting included in management’s report referred to above. Our responsibility is to express opinions on the Company’s consolidated financial statements and on the Company’s internal control over financial reporting based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) (PCAOB) and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audits to obtain reasonable assurance about whether the consolidated financial statements are free of material misstatement, whether due to error or fraud, and whether effective internal control over financial reporting was maintained in all material respects.

Our audits of the consolidated financial statements included performing procedures to assess the risks of material misstatement of the consolidated financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the consolidated financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the consolidated financial statements. Our audit of internal control over financial reporting included obtaining an understanding of internal control over financial reporting, assessing the risk that a material weakness exists, and testing and evaluating the design and operating effectiveness of internal control based on the assessed risk. Our audits also included performing such other procedures as we considered necessary in the circumstances. We believe that our audits provide a reasonable basis for our opinions.

Definition and Limitations of Internal Control over Financial Reporting

A company’s internal control over financial reporting is a process designed to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles. A company’s internal control over financial reporting includes those policies and procedures that (i) pertain to the maintenance of records that, in reasonable detail, accurately and fairly reflect the transactions and dispositions of the assets of the company; (ii) provide reasonable assurance that transactions are recorded as necessary to permit preparation of financial statements in accordance with generally accepted accounting principles, and that receipts and expenditures of the company are being made only in accordance with authorizations of management and directors of the company; and (iii) provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use, or disposition of the company’s assets that could have a material effect on the financial statements.

Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. Also, projections of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliance with the policies or procedures may deteriorate.

Critical Audit Matters

The critical audit matters communicated below are matters arising from the current period audit of the consolidated financial statements that were communicated or required to be communicated to the audit committee and that (i) relate to accounts or disclosures that are material to the consolidated financial statements and (ii) involved our especially challenging, subjective, or complex judgments. The communication of critical audit matters does not alter in any way our opinion on the consolidated financial statements, taken as a whole, and we are not, by communicating the critical audit matters below, providing separate opinions on the critical audit matters or on the accounts or disclosures to which they relate.

Goodwill Impairment Assessment — Advanced Materials & Catalysts Reporting Unit

As described in Notes 2 and 14 to the consolidated financial statements, the Company’s goodwill balance was $404.1 million as of December 31, 2024, and the goodwill associated with the Advanced Materials & Catalysts reporting unit was $77.5 million. Management is required to test goodwill associated with each of its reporting units for impairment at least annually and whenever events or circumstances indicate that it is more likely than not that goodwill may be impaired. Management performs its annual goodwill impairment test as of October 1. Goodwill is tested for impairment at the reporting unit level. If the carrying value of a reporting unit exceeds its fair value, an impairment charge is recognized. Management determined the fair value of its reporting units using both a market approach and an income, or discounted cash flow, approach. Management estimates reporting unit market approach fair value using publicly traded comparable company values and applies the selected market multiples to each reporting unit’s trailing twelve months adjusted earnings before interest, taxes, depreciation and amortization (EBITDA.) Management estimates reporting unit income-based fair value using the discounted cash flow approach, which requires use of significant assumptions including revenue growth rates, operating margin growth rates, the perpetual growth rate, and the discount rate.

The principal considerations for our determination that performing procedures relating to the goodwill impairment assessment of the Advanced Materials & Catalysts reporting unit is a critical audit matter are (i) the significant judgment by management when developing the fair value estimate of the Advanced Materials & Catalysts reporting unit; (ii) a high degree of auditor judgment, subjectivity, and effort in performing procedures and evaluating management’s significant assumptions related to market multiples, revenue growth rates, operating margin growth rates, and the discount rate; and (iii) the audit effort involved the use of professionals with specialized skill and knowledge.

Addressing the matter involved performing procedures and evaluating audit evidence in connection with forming our overall opinion on the consolidated financial statements. These procedures included testing the effectiveness of controls relating to management’s goodwill impairment assessment, including controls over the valuation of the Advanced Materials & Catalysts reporting unit. These procedures also included, among others (i) testing management’s process for developing the fair value estimate of the Advanced Materials & Catalysts reporting unit; (ii) evaluating the appropriateness of the market and income approaches used by management; (iii) testing the completeness and accuracy of underlying data used in the market and income approaches; and (iv) evaluating the reasonableness of the significant assumptions used by management related to market multiples, revenue growth rates, operating margin growth rates, and discount rate. Evaluating management’s assumptions related to revenue growth rates and operating margin growth rates involved evaluating whether the assumptions used by management were reasonable considering (i) the current and past performance of the Advanced Materials & Catalysts reporting unit; (ii) the consistency with external market and industry data; and (iii) whether the assumptions were consistent with evidence obtained in other areas of the audit. Professionals with specialized skill and knowledge were used to assist in evaluating (i) the appropriateness of the market and income approaches and (ii) the reasonableness of the market multiples and discount rate assumptions.

Investment Impairment Assessment — Zeolyst International

As described in Notes 2 and 10 to the consolidated financial statements, the Company’s investments in affiliated companies balance was $349.3 million as of December 31, 2024, of which a substantial portion related to the investment in Zeolyst International. Management evaluates the equity method investments for impairment whenever events or changes in circumstances indicate that the carrying amounts of such investments may be impaired. If a decline in the fair value of an equity method investment is determined to be other than temporary, a loss is recorded in earnings in the current period. During the year ended December 31, 2024, the Company recognized an impairment charge of $65 million on the investment in the Zeolyst Joint Venture, related to the investment in Zeolyst International, to reduce the carrying value of the investment to its estimated fair value. Management estimated the fair value of the investment using a combination of an income, or discounted cash flow approach, and market value approach. Management estimates investments in affiliated companies market approach fair value using publicly traded comparable company values and applies a control premium and the selected market multiples to the investment’s trailing twelve months adjusted EBITDA. Management estimates investments in affiliated companies income-based fair value using the discounted cash flow approach, which requires use of significant assumptions including revenue growth rates, operating margin growth rates, a perpetual growth rate, selling, general and administrative expenses growth rates, and a discount rate.

The principal considerations for our determination that performing procedures relating to the investment impairment assessment of Zeolyst International is a critical audit matter are (i) the significant judgment by management when developing the fair value estimate of the investment in Zeolyst International; (ii) a high degree of auditor judgment, subjectivity, and effort in performing procedures and evaluating management’s significant assumptions related to control premium, market multiples, revenue growth rates, operating margin growth rates, perpetual growth rate, selling, general and administrative expenses growth rates, and the discount rate; and (iii) the audit effort involved the use of professionals with specialized skill and knowledge. As described in the “Opinions on the Financial Statements and Internal Control over Financial Reporting” section, a material weakness was identified related to the Company’s accounting for the investment in the Zeolyst Joint Venture.

Addressing the matter involved performing procedures and evaluating audit evidence in connection with forming our overall opinion on the consolidated financial statements. These procedures included testing the effectiveness of controls relating to management’s investments in affiliated companies impairment assessment, including controls over the valuation of the investment in Zeolyst International. These procedures also included, among others (i) evaluating the Company’s accounting for its investment in Zeolyst International; (ii) testing management’s process for developing the fair value estimate of the investment in Zeolyst International; (iii) evaluating the appropriateness of the market and income approaches used by management; (iv) testing the completeness and accuracy of underlying data used in the market and income approaches; and (v) evaluating the reasonableness of the significant assumptions used by management related to control premium, market multiples, revenue growth rates, operating margin growth rates, perpetual growth rate, selling, general and administrative expenses growth rates, and discount rate. Evaluating management’s assumptions related to revenue growth rates, operating margin growth rates, and selling, general and administrative expenses growth rates involved evaluating whether the assumptions used by management were reasonable considering (i) the current and past performance of the Zeolyst International business; (ii) the consistency with external market and industry data; and (iii) whether the assumptions were consistent with evidence obtained in other areas of the audit. Professionals with specialized skill and knowledge were used to assist in evaluating (i) the appropriateness of the market and income approaches and (ii) the reasonableness of the control premium, market multiples, perpetual growth rate, and discount rate assumptions.

/s/PricewaterhouseCoopers LLP

Philadelphia, Pennsylvania

February 28, 2025

We have served as the Company’s auditor since 2015.