Mechanistic and Atomic-Level Insights into Semihydrogenation Catalysis to Light Olefins

Abstract

Semihydrogenations of alkynes and alkadienes to light olefins catalyzed by a heterogeneous catalyst are widely applied in the chemical industry, but it remains challenging to design high-performance catalysts for these processes. The well-developed synthesis methodologies, characterization techniques for catalyst structures, and theoretical calculations in recent decades render opportunities for understanding mechanisms and elaborating the structures of active sites at the atomic level. This Review summarizes recent advances in the mechanistic and atomic-level insights into semihydrogenation catalysis for alkynes and alkadienes to light olefins. The structure-sensitivity, information on active sites, and reaction kinetics are initially discussed to demonstrate the knowledge on the mechanistic and kinetics details of the hydrogenations of alkynes and alkadienes. We then introduce the regulations for the active sites, especially at the atomic level, based on three categories, i.e., site-isolation, local environment regulation, and oxygen vacancy and interfacial sites. Followed by the discussion on the conventional thermocatalytic hydrogenations, the emerging photocatalytic and electrocatalytic semihydrogenations of alkynes and alkadienes are further covered. Finally, we provide a brief overview on the current status of this field and a perspective for future study on the atomic-level design and regulation of catalysts for controlling the selectivity to target products.

Atomically dispersed Pt to boost adjacent frustrated Lewis pair for 2,6‐diamino‐3,5‐dinitropyridine hydrogenation

“…The adsorption behavior of the target product also plays crucial roles in determining the selectivity of hydrogenation, 48 and thus the adsorption of TAP on these three surfaces were also studied by DFT calculations. The calculated adsorption energy for TAP on the Pt‐In 2 O 3 ‐O v (111) surface is 2.17 eV, which is lower than those on the In 2 O 3 ‐O v (111) surface, suggesting that the presence of atomically dispersed Pt on the In 2 O 3 ‐O v (111) surface weakens the adsorption of TAP.…”

“…This unique adsorption configuration enables the selective activation of the nitro functional group against other functional groups, for example, amino groups, and thus high selectivity to TAP can be achieved. Similarly, the adsorption energy of DADNP on the Pt(111) surface (1.81 eV) is higher than on the In 2 O 3 -O v (111) surface (1.70 eV), which also agree well with the higher activity of the Pt n -In 2 O 3 catalyst than that of the In 2 O 3 catalyst.The adsorption behavior of the target product also plays crucial roles in determining the selectivity of hydrogenation,48 and thus the adsorption of TAP on these three surfaces were also studied by DFT calculations. The calculated adsorption energy for TAP on the Pt-In 2 O 3 -O v (111) surface is 2.17 eV, which is lower than those on theIn 2 O 3 -O v (111) surface, suggesting that the presence of atomically dispersed Pt on the In 2 O 3 -O v (111) surface weakens the adsorption of TAP.…”

Geometric and Electronic Effects in Hydrogenation Reactions

“…A kinetic approach is certainly valuable for a better mechanistic understanding of selective hydrogenation reactions, and furthermore favorable for rational catalyst design based on geometric and electronic modification. − The discussion that follows in this section will highlight several key aspects guarding the basic catalytic performance and enlightening some behaviors reflecting geometric and electronic effects.…”

Atomic Design of Alkyne Semihydrogenation Catalysts via Active Learning

“…Alkyne hydrogenation achieved on heterogeneous catalysts is extensively employed to exquisitely eliminate trace amounts of alkynes impurities remaining in the alkene feedstock, e.g., ethylene and propylene, primarily produced from naphtha steam cracking and alkane dehydrogenation processes. − Despite the substantial advance made over the past decades on the catalytic hydrogenations, achieving low-temperature reactivity while preserving high selectivity remains a great challenge. − Noble Pd catalyst precisely modified by Ag has been the predominant commercial catalyst for this process, but the selectivity to alkenes achieved to date still falls below the values as expected. This circumstance leaves a great deal of room for improvement in the design of alternative catalysts, especially in terms of selectivity and catalyst cost.…”