Bio-butanol is an attractive substitute for fossil-based fuels and platform chemicals. It can be produced from renewable resources by the so-called acetone-butanol-ethanol (ABE) fermentation. However, this process severely suffers from product inhibition, leading to low productivities and low final mixture concentrations (typically < 20g/l). Product inhibition can be relieved by combining the fermentation with a gas stripping process. Although butanol is efficiently stripped from the fermentation medium, it still exists within the stripping gas as a mixture with acetone, ethanol and water, requiring further purification. This is conventionally performed via distillation. Unfortunately, this distillation process requires a large amount of energy, making the butanol production process uneconomical. Among the alternatives for the traditional distillation, adsorption on porous materials has been identified as the most energy-efficient technique1. From that perspective, we studied different microporous zeolites that allow a full recovery and purification of the produced butanol from the stripping gas via adsorption. These zeolites were characterised by measuring (static) batch adsorption isotherms and performing (dynamic) fixed-bed separation experiments using vapor mixtures. An all-silica zeolite (ITQ-29) with a LTA topology showed to have a high adsorption capacity for butanol. Fixed-bed experiments revealed the high selectivity of this material for butanol over acetone, ethanol and water. Two other zeolites, Si-CHA and SAPO-34, both possessing a CHA topology, were also studied on their selectivity for the different vapor phase components. The small pore size of these zeolites led to the exclusion of acetone and butanol, whereas ethanol and water could adsorb. The all-silica, apolar Si-CHA zeolite showed a higher selectivity towards ethanol compared to the more polar SAPO-34 zeolite. Since a small amount of ethanol and water co-adsorbed on ITQ-29, these zeolites were used to further purify the butanol adsorbed on ITQ-29. During the regeneration phase of ITQ-29, an adsorption column containing a CHA-type zeolite was placed in series to further purify the desorbing butanol. Using this combined adsorption/regeneration process, 99% of the butanol adsorbed on ITQ-29 could be recovered at a purity of > 99.5 mole%. (1) Qureshi, N.; Hughes, S.; Maddox, I.; Cotta, M. Bioprocess Biosyst. Eng. 2005, 27 (4), 215–222.
Original languageEnglish
StatePublished - 9 Jun 2017
Event13th International Conference on Renewable Resources and Biorefineries - Wroclaw, Poland

Conference

Conference13th International Conference on Renewable Resources and Biorefineries
CountryPoland
CityWroclaw
Period7/06/179/06/17

ID: 30458734