The design and development of non-precious metal catalysts with excellent performance are of great significance for selective hydrogenation of acetylene from ethylene feedstock. In our previous research, a new active copper carbide (Cu x C) phase with high hydrogenation activity was synthesized by thermal treatment of acetylene-containing gas followed by hydrogen reduction. In the present work, a Zn-modified Cu x C-containing catalyst was prepared from the mixture of Cu(OH) 2 and Zn(OH) 2 by the same procedure to investigate the effect of Zn on the structure and catalytic performance of Cu x C. The addition of Zn helped to reduce the crystalline size of Cu x C and to increase the amount of Cu x C crystallites, resulting in enhanced hydrogenation activity in selective hydrogenation of acetylene. Specifically, the catalyst prepared under the optimal conditions exhibited remarkably excellent acetylene hydrogenation performance with complete acetylene conversion, low ethane selectivity (25%), and outstanding stability (>140 h) at 100 °C in the presence of large excess ethylene.
Continuous-flow processing is considered
as a disruptive technology
in the synthesis of active pharmaceutical ingredients and other fine
chemicals. However, it remains extremely challenging to immobilize
heterogeneous catalysts in the channels of microreactors in a facile
and flexible manner. In the present investigation, a polymer monolith
coiled copper reactor was fabricated by Cu-catalyzed polymerization
of acetylene at atmospheric pressure in the temperature range of 290–370
°C. The polymerization yielded a cotton-like structure of carbonaceous
fibers, which were able to assemble by themselves to form a monolith
inside the copper tube. The characterization results revealed that
unsaturated CC groups, which are favorable for post-surface
modification, were present on the carbonaceous fibers. After air oxidation
at 160 °C for 10 h, a fraction of the CC groups were
converted to CO groups. By strong interaction with CO
groups, Pd was immobilized in the polymer monolith by circulating
an ethanol solution of palladium acetate through the copper tube.
A 1000 mm-long monolith tube reactor with an inner diameter of 2 mm
with a Pd loading of 1.15 wt % was fabricated and used in the continuous
Suzuki–Miyaura coupling reaction. An ethanol–water (2:1
in volume) solution of iodobenzene (0.0125 M), phenylboronic acid
(0.0188 M), and potassium carbonate (0.0250 M) was used as the feed,
and the reaction took place at 100 °C and 1.0 MPa. The selectivity
to biphenyl was kept at >99% with complete conversion of iodobenzene
in a 100 h run.
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