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        <title>Ecovyst, Inc. Quarterly report pursuant to Section 13 or 15(d)</title>
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            <h3>Quarterly report pursuant to Section 13 or 15(d)</h3>
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                                <a class="menu-item " href="/sec-filings/all-sec-filings/xbrl_doc_only/824">Cover</a>
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                                <a class="menu-item " href="/sec-filings/all-sec-filings/xbrl_doc_only/825">Financial Statements</a>
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                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/825">CONDENSED CONSOLIDATED STATEMENTS OF INCOME</a></li>
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                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/828">CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/829">CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS??? EQUITY</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/830">CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS</a></li>
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                                <a class="menu-item current" href="/sec-filings/all-sec-filings/xbrl_doc_only/831">Notes to Financial Statements</a>
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                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/831">Background and Basis of Presentation</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/832">New Accounting Standards</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/833">Revenue from Contracts with Customers</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/834">Fair Value Measurements</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/835">Accumulated Other Comprehensive Income</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/836">Goodwill</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/837">Other Operating Expense, Net</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/838">Inventories</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/839">Investments in Affiliated Companies</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/841">Property, Plant and Equipment</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/842">Leases</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/843">Long-term Debt</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/844">Financial Instruments</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/845">Income Taxes</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/846">Benefit Plans</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/847">Commitments and Contingent Liabilities</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/849">Reportable Segments</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/850">Stock-Based Compensation</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/851">Earnings per Share</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/853">Supplemental Cash Flow Information</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/855">Subsequent Events</a></li>
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                                <a class="menu-item " href="/sec-filings/all-sec-filings/xbrl_doc_only/857">Accounting Policies</a>
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                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/857">Background and Basis of Presentation (Policies)</a></li>
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                                <a class="menu-item " href="/sec-filings/all-sec-filings/xbrl_doc_only/859">Notes Tables</a>
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                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/859">Revenue from Contracts with Customers (Tables)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/861">Fair Value Measurements (Tables)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/863">Accumulated Other Comprehensive Income (Tables)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/865">Goodwill (Tables)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/867">Other Operating Expense, Net (Tables)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/871">Inventories (Tables)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/873">Investments in Affiliated Companies (Tables)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/875">Property, Plant and Equipment (Tables)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/877">Leases (Tables)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/879">Long-term Debt (Tables)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/884">Financial Instruments (Tables)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/889">Benefit Plans (Tables)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/890">Reportable Segments (Tables)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/891">Stock-Based Compensation (Tables)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/892">Earnings per Share (Tables)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/894">Supplemental Cash Flow Information (Tables)</a></li>
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                                <a class="menu-item " href="/sec-filings/all-sec-filings/xbrl_doc_only/899">Notes Details</a>
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                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/899">Background and Basis of Presentation (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/900">New Accounting Standards (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/903">Revenue from Contracts with Customers (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/904">Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/906">Accumulated Other Comprehensive Income - Pre-tax and After-tax Components of Other Comprehensive Income (Loss) (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/907">Accumulated Other Comprehensive Income - Change by Component (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/908">Accumulated Other Comprehensive Income - Reclassifications out of AOCI (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/910">Goodwill (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/911">Other Operating Expense, Net (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/912">Inventories (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/914">Investments in Affiliated Companies - Ownership Percentage (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/915">Investments in Affiliated Companies - Summarized Income Statement (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/917">Investments in Affiliated Companies - Narratives (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/919">Property, Plant and Equipment (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/921">Property, Plant and Equipment - Narratives (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/923">Leases - Narratives (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/924">Leases - Right-of-Use Lease Assets and Lease Liabilities (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/926">Leases - Remaining Average Weighted Average Lease Term and Discount Rate (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/934">Leases - Lease Maturity Schedule - ASC 842 (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/936">Leases - Lease Maturity Schedule - ASC 840 (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/947">Leases - Other Lease Information (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/948">Long-term Debt (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/949">Long-term Debt - Narratives (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/951">Financial Instruments - Narratives (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/954">Financial Instruments - Fair Value (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/955">Financial Instruments - Effect on Other Comprehensive Income (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/956">Financial Instruments - Cash Flow Hedge Impact on Income Statement (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/957">Financial Instruments - Net Investment Hedge Impact on AOCI (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/958">Income Taxes (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/959">Benefit Plans - Net Periodic Pension Expense Benefit (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/961">Reportable Segments  - Summary Financial Information by Reportable Segment (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/965">Reportable Segments  - Reconciliation of Net Loss to Adjusted EBITA (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/968">Stock-Based Compensation - Narratives (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/971">Stock-Based Compensation - Schedule of RSU and PSU Activity (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/972">Earnings per Share - Reconciliation from Basic to Diluted Weighted Average Shares Outstanding (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/973">Earnings per Share - Reconciliation of Net Income (Loss) (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/974">Earnings per Share - Anti-dilutive Shares (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/975">Supplemental Cash Flow Information (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/976">Supplemental Cash Flow Information - Cash and Restricted Cash Reconciliation (Details)</a></li>
                                                                    </ul>
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                <h4>Financial Instruments</h4>
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