(109f) Selective Synthesis of 1,3-Butadiene Via Chemo-Catalytic Conversion of 1,4-Butanediol over Modified and Unmodified HZSM-5 Zeolite Catalyst: A Thermokinetic Analysis

Vapour-phase dehydration of 1,4-butanediol (1,4-BDO) is a sustainable approach to produce 1,3-butadiene (BD), which is widely used as monomer of synthetic rubber among other polymers. The chemo-catalytic conversion of 1,4-BDO to value-added products were studied in presence of HZSM-5 zeolite catalysts in a atmospheric pressure operated downflow fixed bed reactor. Strong Brønsted acid sites in HZSM-5, determined via temperature-programmed analysis, promoted tetrahydrofuran (THF) as major product at lower temperatures (close to 95% selectivity). Selectivity to second dehydration products such as BD and propylene were influenced greatly by temperature and weight hour space velocity (around 40% combined selectivity observed at 723K). The selectivity to products varied with Si/Al ratio of HZSM5 species as well, as the B/L acid site ratio, examined by pyridine-FTIR analysis, altered with change in Si/Al ratio. Thermodynamic analysis via process modelling, and detailed kinetic study were also performed. The control experiments performed in lab scale suggested metal sites of HZSM5 species were responsible for competitive propylene formation with 1,3-BD by triggering undesired dehydroformylation side reactions and therefore basic modification were carried out to neutralize metallic sites.