Selective hydrogenation of acetylene : fundamental elucidation by a combined experimental and theoretical approach

Abstract

Selective hydrogenation of acetylene in excess ethylene, which will selectively remove acetylene from ethylene, is of paramount significance in the petrochemical and polymer industries. The key issues in this process are activity, selectivity and green oil formation. In this thesis, first-principles calcu lations within the density functional theory (OFT) framework together with experimental methods are introduced to study this important process. The selective hydrogenation of acetylene to ethylene on several Pd surfaces and Pd surfaces with subsurface species as well as a number of Pd based alloys are investigated using OFT calculations to understand the acetylene hydrogenation activity, the selectivity of ethylene formation and the formation of butadiene, considered to be the precursor of green oil formation . The general trend of the activity, selectivity and butadiene formation over these catalysts are obtained and discussed . In order to understand the recently reported experimental results showing the promotion effects of Au on Ni and B on Pd, these systems are studied, and the activity and selectivity of acetylene hydrogenation and the 1,3 -butadiene formation over these surfaces are obtained and compared. Experimentally, the selective hydrogenation of acetylene is tested with Pd/Ah03, PdAglAl20 3 and Li2COr Pd/Ab03 catalysts under tail-end (TE) conditions, The performance of these catalysts are introduced and compared. Using several characterization techniques, the origin of the performance of these catalysts is understood. The development of the two-step model to determine the general adsorption energy window based on an understanding of the rate determining steps of reactant adsorption and desorption only, i.e. the Sabatier principle will also be presented in this thesis. Our work shows that the combination of OFT calculations and experimental methods is powerful to investigate chemical reactions occurring on surfaces, which are important in the area of heterogeneous catalysisEThOS - Electronic Theses Online ServiceGBUnited Kingdo