An alumina-coated, egg-shell Pd/α-Al₂O₃@SiC catalyst with enhanced ethylene selectivity in the selective hydrogenation of acetylene

Abstract

5For the selective hydrogenation of acetylene to ethylene, the selectivity of Pd catalyst is crucial. However, palladium is present as skin distributed on the surface of Al 2 O 3 support. Pd active sites dispersed on the skin exhibited high activity for acetylene removal, which also inhibited over-hydrogenation of ethylene to ethane and formation of oligomeric species on the catalyst. Therefore, it is significant to accurately control the distribution range of Pd active sites on the support by a feasible route. Herein, we 10 demonstrated a facile approach to precisely control Pd active-site distribution range on the support. Onestep coating α-Al 2 O 3 layer was prepared directly on the outside surface of ring-like SiC substrate by spray-coating, which obtained an egg-shell α-Al 2 O 3 @SiC support. The thickness of α-Al 2 O 3 layer can be tuned from 50 µm to 300 µm freely. The newly designed α-Al 2 O 3 @SiC support was used in the selective hydrogenation of acetylene as catalyst body. As expected, the rational design of Pd catalyst with α-15 Al 2 O 3 @SiC composite material as support has the ability to achieve the higher ethylene selectivity than conventional extrusive pellet Pd catalyst. In this work, the ethylene selectivity of egg-shell Pd-Ag/α-Al 2 O 3 @SiC catalyst was 16% more than that of conventional pellet Pd-Ag/α-Al 2 O 3 catalyst when obtaining complete removal of acetylene in ethylene-rich stream. 65 achieve a feasible route to control Pd active-site distribution range on the support precisely, silicon carbide (SiC) as substrate was used to prepare α-Al 2 O 3 @SiC support as the catalyst support for the selective hydrogenation of acetylene to ethylene. SiC has admirable mechanical strength, superior thermal conductivity, 70 excellent chemical inertness and high resistance towards oxidation. And it will be a simple and inexpensive material compared to Al 2 O 3 . Moreover, SiC seems to be a potentially excellent functional material for various catalytic reactions, such as electrocatalytic reaction, 41,42 photocatalytic reaction, 43-46 75 Fischer-Tropsch synthesis 47-49 and Pt catalyst for fuel cell @SiC catalyst showed the higher ethylene selectivity than Pd-Ag/α-Al 2 O 3 catalyst when obtaining complete removal of acetylene in ethylene-rich stream.

Highly Dispersed PdNPs/α-Al2O3 Catalyst for the Selective Hydrogenation of Acetylene Prepared with Monodispersed Pd Nanoparticles

“…For supported Pd/Al 2 O 3 catalysts, isolated Pd active sites dispersed on the surface of the Al 2 O 3 support as egg-shell catalysts exhibited high activity for acetylene removal, which also inhibited the over-hydrogenation of ethylene to ethane. Therefore, it is significant to decrease Pd active site ensembles [5,7,11,16]. Figure 2a shows that the PdNPs on the PdNPs/α-Al 2 O 3 catalyst were smaller particles than those on the Pd/α-Al 2 O 3 catalyst ( Figure 2b).…”

“…For the selective hydrogenation of acetylene, supported Pd catalysts are used for the catalytic removal process. Therefore, supported Pd catalysts with low Pd loading still have attracted much attention in recent years [4][5][6][7][8][9][10]. The recent advance on supported Pd catalysts is to increase their ethylene selectivity and enhance their long-term stability.…”

Incorporating Pb2+ Templates into the Crystalline Structure of MnO2 Catalyst Supported on Monolith: Applications in H2O2 Decomposition

“…To achieve good adhesion of the Al 2 O 3 layer on the monolith substrate, 90% of the alumina powder diameters were less than 4 μm. 45 In this way, the surface of the square channel monoliths was fully covered by a layer of precursor, and then the support was withdrawn from the stock suspension. After that, the support was dried at 90 °C for 6 h in a vacuum oven and calcined at 700 °C for 3 h with a heating rate of 3 °C min –1 to eliminate the binder and impurities in a furnace.…”

Acetylene in Organic Synthesis: Recent Progress and New Uses

“…Tunable thickness of a support layer allows effective control of Pd penetration range and results in uniform lateral distribution of Pd active sites. Egg-shell Pd/α-Al 2 O 3 @SiC catalysts with the controlled thickness of support layer (50–300 μm, Figure 8 ) were obtained by a specifically developed procedure and tested in acetylene hydrogenation [ 252 ]. The catalysts had the same acetylene conversion but higher ethylene selectivity as compared with the conventional Pd-Ag/α-Al 2 O 3 catalyst.…”

“… ( a ) SEM image of Pd/α-Al 2 O 3 @SiC catalyst, ( b ) TEM image of Pd particles on Al 2 O 3 layer of Pd/α-Al 2 O 3 @SiC catalyst (reproduced with permission from [ 252 ]. Copyright 2016, the Royal Society of Chemistry).…”