| dc.description.abstract | Ethylene, propylene and isobutylene are among the most important intermediates for the pro-duction for many chemical products in industry. These chemicals are mostly produced through catalytic dehydrogenation which has thermodynamic limitations in terms of performance. Membrane reactors provide a unique opportunity to overcome these limitation. In this work, MFI zeolite membrane reactor was used to perform ethane, propane, and isobutane dehydro-genation. For ethane, propane, and isobutane dehydrogenation, impact of impact of different operating conditions on reaction performance was studied. In packed bed reactor (PBR), ethane dehydrogenation and propane dehydrogenation reaction performance decreased with increase in reaction side pressure. However, for packed bed membrane reactor (PBMR) reaction perfor-mance increased with reaction side pressure. The maximum ethane conversion, ethylene selec-tivity and ethylene yields obtained were 29%, 97%, and 28%, respectively. Similarly, the high-est propane conversion, propylene selectivity and propylene yields obtained were 49%, 97%, and 47%, respectively. For the isobutane dehydrogenation the impact of operating conditions like temperature, sweep gas flow rate, and space velocity was examined. The highest isobutane con-version, isobutylene selectivity and isobutylene yield was 27%, 97% and 26% respectively. Also 1D plug flow reactor (PFR) model was developed for ethane, propane and isobutane dehydro-genation reaction. Model correctly predicted the conversion values and was also used to evalu-ate the conversion values beyond experimental conditions. However, dehydrogenation reaction in PBMR helped in overcoming thermodynamic limitations and also produced relatively purer products but still there is a need for further purification of these products. For further purifica-tion of products in propane dehydrogenation reaction, novel ZIF-8 membrane were synthesized for separating propylene/propane gas mixture. ZIF-8 membrane was synthesized on anodic alu-minum oxide (AAO) using secondary growth method. In this study, effect of seeding type, membrane synthesis time, and effect of zinc source was examined. It was found that silicalite seeding, 10 h synthesis time, and ZnCl₂ as precursor were the optimized conditions for ZIF-8 membrane synthesis and the reported separation factor for propylene/propane gas mixture was 170 and the corresponding propylene permeance was 0.9 × 10⁻⁸ mol m⁻² s⁻¹ Pa⁻¹. Silicalite seed-ing helped in better attachment of ZIF-8 layer to the support. Though, ZIF-8 membrane exhib-ited impressive propylene/propane separation performance but still there were inherent defects and pinholes in the ZIF-8 framework because of Zn vacancies. ZnO atomic layer deposition (ALD) was used to cure the defects in the membrane framework. After ALD, ZIF-8 membrane separation performance for propylene/propane gas mixture enhanced from 141 to 270 after two ALD cycles. Further ALD cycles only deposited ZnO on ZIF-8 pores and reduced separation factor for propylene/propane gas mixture. However, propylene and propane gas permeance de-creased monotonously with number of ALD cycles. | |
