221
electron-attracting additives (e.g., phosphorus, oxygen, sulphur and chlorine) over
Pt and Rh catalysts influenced the activity and selectivity. Piperidine modified metal
site showed a decrease in the rate of hydrogenation of 1-butene and 1,3-butadiene
over the pure Pt/Rh catalysts. Selectivity for olefin formation from 1,3-butadiene
was increased on Pt surface, whereas selectivity change was negligible in case of Rh
surface. In case of electron attracting additives, for example, nitrogen compounds
increase the hydrogenation rate of 1,3-butadiene on an Rh catalyst. In case of Pt, an
increase in the selectivity for l-butene was observed and the direct formation of
butane is drastically reduced due to specific preference of 1,2-addition. In contrast
with pure geometric effects, no correlation was obtained with the electronic
properties of the additive. Sárkány (1995–1997) [69, 94, 95], in a series of 4 papers,
investigated the hydrogenation of 1,3-butadiene on catalysts prepared from the
different methods in the effects of various poisonings or adspecies. The presence
and formation of polyenes in the vicinity of metallic sites was due to the unusual
hydrogenation character of the Pd 2 Ni 50 Nb 48 ribbon. It was further confirmed by
Alves [28] that in the case of liquid-phase hydrogenation of 1,3-butadiene, 1-butene
in the presence of isoprene on a commercial Pd/Al 2 O 3 catalyst, concentration of
1-butene practically remains unchanged even when the liquid was almost depleted
from 1,3-butadiene. It was proven that the isoprene adsorption strength was higher
than that of 1-butene and lower than that of 1,3-butadiene. Hence, it was clear that
isoprene was a good option to use as an additive to improve the 1-butene selectivity
in 1-butene purification processes. Adspecies formed from n-butylamine on Cu/
SiO 2 seem to influence the competition between diene and n-butenes. The electronic
effect of the adspecies can be emphasized by the variation in the intrinsic
hydrogenation selectivity towards diene in presence of methanol. Preadsorption of
methanol on Cu/SiO 2 caused electronic modification of Cu sites (through
decomposition of methoxy species), and this increased the cis 2-butene. Formation
of 1-butene prevails on the sample reduced at 753 K, and this points to the facile
1,2-addition of hydrogen atoms to adsorbed diene. Improved 2-butene formation
rate over the Cu sites perturbed by alcohol appears to show that 1,4 addition
mechanism is preferred. These finding points to the formation of π-allyl or π, σ
bonded C 4 H 7 species rather than 1-butene isomerization in the gas phase or adsorbed
phase. Firmly held adspecies generated from butylamine or diene favour the
formation of alkene by the adsorption of n-butene. The presence of carbonaceous or
hydrocarbonaceous deposited on Pd/Ag catalyst increases the formation of butane.
Several authors [68, 69, 96] have proposed that carbonaceous overlayers present on
the catalyst surface play a key role in hydrogenation. Hydrocarbonaceous deposits
affect the competition between diene and n-butenes and therefore increases the
1-butene selectivity in the hydrogenation of 1,3-butadiene. Wu et al. [96] studied the
selectivity in the hydrogenation of 1,3-butadiene on using molybdenum nitride
catalyst and the observed high selectivity towards 1-butene is most likely due to the
weak interaction between 1,3-butadiene and nitrogen atoms present in the
molybdenum nitride catalyst surface. Silvestre-Albero and co-workers [65] reported
that small quantities of CO addition dramatically altered the selectivity over the
Pd(110) surface, i.e. the hydrogenation to n-butane was totally suppressed; however,
Selective Hydrogenation of 1,3-Butadiene to 1-Butene: Review on Catalysts, Selectivity…
electron-attracting additives (e.g., phosphorus, oxygen, sulphur and chlorine) over
Pt and Rh catalysts influenced the activity and selectivity. Piperidine modified metal
site showed a decrease in the rate of hydrogenation of 1-butene and 1,3-butadiene
over the pure Pt/Rh catalysts. Selectivity for olefin formation from 1,3-butadiene
was increased on Pt surface, whereas selectivity change was negligible in case of Rh
surface. In case of electron attracting additives, for example, nitrogen compounds
increase the hydrogenation rate of 1,3-butadiene on an Rh catalyst. In case of Pt, an
increase in the selectivity for l-butene was observed and the direct formation of
butane is drastically reduced due to specific preference of 1,2-addition. In contrast
with pure geometric effects, no correlation was obtained with the electronic
properties of the additive. Sárkány (1995–1997) [69, 94, 95], in a series of 4 papers,
investigated the hydrogenation of 1,3-butadiene on catalysts prepared from the
different methods in the effects of various poisonings or adspecies. The presence
and formation of polyenes in the vicinity of metallic sites was due to the unusual
hydrogenation character of the Pd 2 Ni 50 Nb 48 ribbon. It was further confirmed by
Alves [28] that in the case of liquid-phase hydrogenation of 1,3-butadiene, 1-butene
in the presence of isoprene on a commercial Pd/Al 2 O 3 catalyst, concentration of
1-butene practically remains unchanged even when the liquid was almost depleted
from 1,3-butadiene. It was proven that the isoprene adsorption strength was higher
than that of 1-butene and lower than that of 1,3-butadiene. Hence, it was clear that
isoprene was a good option to use as an additive to improve the 1-butene selectivity
in 1-butene purification processes. Adspecies formed from n-butylamine on Cu/
SiO 2 seem to influence the competition between diene and n-butenes. The electronic
effect of the adspecies can be emphasized by the variation in the intrinsic
hydrogenation selectivity towards diene in presence of methanol. Preadsorption of
methanol on Cu/SiO 2 caused electronic modification of Cu sites (through
decomposition of methoxy species), and this increased the cis 2-butene. Formation
of 1-butene prevails on the sample reduced at 753 K, and this points to the facile
1,2-addition of hydrogen atoms to adsorbed diene. Improved 2-butene formation
rate over the Cu sites perturbed by alcohol appears to show that 1,4 addition
mechanism is preferred. These finding points to the formation of π-allyl or π, σ
bonded C 4 H 7 species rather than 1-butene isomerization in the gas phase or adsorbed
phase. Firmly held adspecies generated from butylamine or diene favour the
formation of alkene by the adsorption of n-butene. The presence of carbonaceous or
hydrocarbonaceous deposited on Pd/Ag catalyst increases the formation of butane.
Several authors [68, 69, 96] have proposed that carbonaceous overlayers present on
the catalyst surface play a key role in hydrogenation. Hydrocarbonaceous deposits
affect the competition between diene and n-butenes and therefore increases the
1-butene selectivity in the hydrogenation of 1,3-butadiene. Wu et al. [96] studied the
selectivity in the hydrogenation of 1,3-butadiene on using molybdenum nitride
catalyst and the observed high selectivity towards 1-butene is most likely due to the
weak interaction between 1,3-butadiene and nitrogen atoms present in the
molybdenum nitride catalyst surface. Silvestre-Albero and co-workers [65] reported
that small quantities of CO addition dramatically altered the selectivity over the
Pd(110) surface, i.e. the hydrogenation to n-butane was totally suppressed; however,
Selective Hydrogenation of 1,3-Butadiene to 1-Butene: Review on Catalysts, Selectivity…