METHANOL PRODUCTION VIA CATALYTIC CO2 HYDROGENATION

THE TRANSITION TOWARD SUSTAINABLE CHEMICAL PROCESSES HAS RENEWED GLOBAL INTEREST IN THE SYNTHESIS OF METHANOL FROM CO₂ AND RENEWABLE HYDROGEN, A ROUTE THAT SIMULTANEOUSLY ENABLES CARBON VALORIZATION AND THE PRODUCTION OF A KEY PLATFORM CHEMICAL. THIS WORK INVESTIGATES ADVANCED CATALYTIC SYSTEMS FOR CO₂ HYDROGENATION TO METHANOL, AIMING TO ENHANCE ACTIVITY AND SELECTIVITY UNDER MILDER CONDITIONS THAN THOSE TYPICALLY ADOPTED AT THE INDUSTRIAL SCALE. THE STUDY IS STRUCTURED INTO THREE INTEGRATED RESEARCH BLOCKS: (I) A SYSTEMATIC ANALYSIS OF CU/ZNO/AL₂O₃ (CZA) CATALYSTS PREPARED USING DIFFERENT PRECURSOR SALTS; (II) THE DESIGN OF CU-BASED CATALYSTS SUPPORTED ON OXYGEN-DEFECTIVE OXIDES; AND (III) THE EXPLORATION OF CU-MOF MATERIALS IN COLLABORATION WITH POLITECNICO DI TORINO. IN THE FIRST PART, CZA CATALYSTS SYNTHESIZED FROM NITRATE, ACETATE, AND CHLORIDE PRECURSORS WERE EXTENSIVELY CHARACTERIZED THROUGH XRD, RAMAN, UV–VIS, TPR, XPS, TPD, STEM, AND OTHER TECHNIQUES TO ELUCIDATE HOW PRECURSOR-DEPENDENT STRUCTURAL MODIFICATIONS AFFECT CATALYTIC BEHAVIOR. CATALYTIC TESTS CONDUCTED BETWEEN 1 AND 30 BAR REVEALED THAT CZA_NITRATE EXHIBITS SUPERIOR PERFORMANCE, ACHIEVING 100% METHANOL SELECTIVITY AT 180–200 °C UNDER ATMOSPHERIC PRESSURE AND MAINTAINING HIGH PRODUCTIVITY AT ELEVATED PRESSURES. CORRELATION BETWEEN COPPER SPECIES AND ACTIVITY DEMONSTRATED THAT THE ACTIVE PHASE CONSISTS OF INTERFACIAL CU–ZNO SITES RATHER THAN METALLIC CU, CONFIRMING LONG-DEBATED HYPOTHESES IN THE LITERATURE. HIGH-PRESSURE EXPERIMENTS FURTHER HIGHLIGHTED THE THERMODYNAMIC ADVANTAGES OF INCREASED PRESSURE, YIELDING SIGNIFICANT IMPROVEMENTS IN CONVERSION, SELECTIVITY, AND TOF. THE SECOND RESEARCH BLOCK FOCUSES ON CU CATALYSTS SUPPORTED ON BLACK TITANIA (BTIO₂), AN OXYGEN-DEFICIENT MATERIAL DESIGNED TO ENHANCE CO₂ ADSORPTION AND ACTIVATION. COMPARATIVE TESTS BETWEEN CATALYSTS CONTAINING PRISTINE AND REDUCED TITANIA CONFIRMED THAT OXYGEN VACANCIES ARE ESSENTIAL FOR CATALYTIC ACTIVITY. ALTHOUGH CHANGES IN COPPER LOADING PRODUCED ONLY MODERATE EFFECTS, THE INTRODUCTION OF ZNO CREATED ADDITIONAL INTERFACIAL SITES, FURTHER IMPROVING METHANOL FORMATION. PRESSURE WAS AGAIN IDENTIFIED AS A KEY PARAMETER, WITH SELECTIVITY MAXIMIZED AT MODERATE TEMPERATURES AND HIGH PRESSURES. THE FINAL PART EXAMINES CU-MOF CATALYSTS WITH VARYING COPPER LOADINGS. STRUCTURAL ANALYSES AND CATALYTIC TESTS SHOWED THAT THE 7.5CU_MOF SAMPLE OFFERS OPTIMAL PERFORMANCE, SELECTIVELY PROMOTING METHANOL FORMATION WHILE SUPPRESSING CO AND CH₄ PRODUCTION. TOF ANALYSES BASED ON CU(I) QUANTIFICATION VALIDATED THE EXISTENCE OF AN OPTIMAL COPPER CONTENT AND REVEALED DISTINCT STRUCTURE–PERFORMANCE RELATIONSHIPS GOVERNED BY THE DISTRIBUTION OF COPPER SPECIES WITHIN THE MOF FRAMEWORK. OVERALL, THIS WORK CLARIFIES FUNDAMENTAL ASPECTS OF CO₂ HYDROGENATION CATALYSIS AND PROVIDES RATIONAL DESIGN PRINCIPLES FOR DEVELOPING NEXT-GENERATION CATALYSTS. BY INTEGRATING INTERFACIAL ENGINEERING, VACANCY CREATION, AND MOF-BASED ARCHITECTURES, THE STUDY DEMONSTRATES PROMISING PATHWAYS TOWARD EFFICIENT METHANOL SYNTHESIS UNDER MORE SUSTAINABLE OPERATING CONDITIONS.