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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/1499">Cover</a>
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                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1499">Document and Entity Information</a></li>
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                                <a class="menu-item " href="/sec-filings/all-sec-filings/xbrl_doc_only/1500">Financial Statements</a>
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                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1500">CONDENSED CONSOLIDATED STATEMENTS OF INCOME</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1501">CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1502">CONDENSED CONSOLIDATED BALANCE SHEETS</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1503">CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS??? EQUITY</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1504">CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS</a></li>
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                                <a class="menu-item " href="/sec-filings/all-sec-filings/xbrl_doc_only/1505">Notes to Financial Statements</a>
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                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1505">Background and Basis of Presentation</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1506">New Accounting Standards</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1507">Revenue from Contracts with Customers</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1508">Fair Value Measurements</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1509">Stockholders&#039; Equity</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1510">Asset Swap Transaction</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1511">Sale of Product Lines</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1512">Goodwill</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1513">Other Operating Expense, Net</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1514">Inventories, Net</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1515">Investments in Affiliated Companies</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1516">Property, Plant and Equipment</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1517">Long-term Debt</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1518">Financial Instruments</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1519">Income Taxes</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1520">Benefit Plans</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1521">Commitments and Contingent Liabilities</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1522">Reportable Segments</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1523">Stock-Based Compensation</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1524">Earnings per Share</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1525">Supplemental Cash Flow Information</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1526">Subsequent Events</a></li>
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                                <a class="menu-item " href="/sec-filings/all-sec-filings/xbrl_doc_only/1527">Accounting Policies</a>
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                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1527">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/1528">Notes Tables</a>
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                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1528">Revenue from Contracts with Customers Revenue from Contracts with Customers (Tables)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1529">Fair Value Measurements (Tables)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1530">Stockholders&#039; Equity (Tables)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1531">Asset Swap Transaction (Tables)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1532">Goodwill (Tables)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1533">Other Operating Expense, Net (Tables)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1534">Inventories (Tables)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1535">Investments in Affiliated Companies (Tables)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1536">Property, Plant and Equipment (Tables)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1537">Long-term Debt (Tables)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1538">Financial Instruments (Tables)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1539">Benefit Plans (Tables)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1540">Reportable Segments (Tables)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1541">Stock-Based Compensation (Tables)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1542">Earnings per Share (Tables)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1543">Supplemental Cash Flow Information (Tables)</a></li>
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                                <a class="menu-item current" href="/sec-filings/all-sec-filings/xbrl_doc_only/1544">Notes Details</a>
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                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1544">Background and Basis of Presentation (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1545">Disaggregated Revenue (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1546">Contract Assets and Liabilities (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1547">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/1548">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/1549">Change by Component (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1550">Reclassifications out of AOCI (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1551">Stock Repurchase Program (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1552">Asset Swap Transaction (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1553">Sale of Product Lines (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1554">Goodwill (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1555">Other Operating Expense, Net (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1556">Inventories (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1557">Ownership Percentage (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1558">Summarized Income Statement (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1559">Investments in Affiliated Companies Narrative (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1560">Property, Plant and Equipment (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1561">Property, Plant and Equipment Narrative (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1562">Long-term Debt (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1563">Long-term Debt Narrative (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1564">Financial Instruments Narrative (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1565">Fair Value (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1566">Effect on Other Comprehensive Income (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1567">Cash Flow Hedge Impact on Income Statement (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1568">Net Investment Hedge Impact on AOCI (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1569">Income Taxes (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1570">Net Periodic Pension Expense Benefit (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1571">Summary Financial Information by Reportable Segment (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1572">Reconciliation of Net Income to Segment Adjusted EBITDA (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1573">Stock-Based Compensation Narrative (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1574">Performance Stock Units Assumptions and Methodology (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1575">Schedule of RSU and PSU Activity (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1576">Reconciliation from Basic to Diluted Weighted Average Shares Outstanding (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1577">Calculation of Basic and Diluted Earnings per Share (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1578">Anti-dilutive Shares (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1579">Supplemental Cash Flow Information (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1580">Cash and Restricted Cash Reconciliation (Details)</a></li>
                                                                            <li><a href="/sec-filings/all-sec-filings/xbrl_doc_only/1581">Subsequent Events (Details)</a></li>
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                <h4>Schedule of RSU and PSU Activity (Details)</h4>
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