The kinetics of acetylene hydrogenation in the presence of a large
excess of ethylene was studied
in a laboratory flow reactor. Experiments were carried out using a
Pd/α-Al2O3 commercial
catalyst and a simulated cracker gas mixture
(H2/C2H2 = 50; 60%
C2H4; 30% H2, and traces
of
CO), at varying temperature (293−393 K) and pressure (2−35 atm).
Competing mechanisms
for acetylene and ethylene hydrogenation were formulated and the
corresponding kinetic
equations derived by rate-determining step methods. A criterion
based upon statistical analysis
was used to discriminate between rival kinetic models. The
selected equations are consistent
with the adsorption of C2H2 and
C2H4 in the same active sites followed by
reaction with adsorbed
hydrogen atoms to form C2H4 and
C2H6 in a one-step process. Good agreement
between computed
and experimental results was obtained using a nonisothermal reactor
model that takes into
account the existence of external temperature and concentration
gradients. The derived kinetic
equations together with a pseudohomogeneous model of an integral
adiabatic flow reactor were
employed to simulate the conversion and the temperature profiles for a
commercial hydrogenation
unit.
Equilibrium and kinetic data for propane and propylene adsorption in pellets (Grace Davison)
and crystals (PQ Corp.) of 5A zeolite are presented in the temperature range 323−423 K. The
pellet adsorption loading measured by gravimetry is 1.7 mmol/g for propylene and 1.3 mmol/g
for propane at 100 kPa and 423 K. The selectivity for propylene increases with temperature
and is in the range 1.08−1.35 at 100 kPa, being higher at lower pressures. The kinetic data
measured by zero-length-column (ZLC) chromatography indicate that the transport of sorbate
in the pellets is controlled by macropore diffusion; pore diffusivities are in the range 0.018−0.027 cm2/s for both gases. Crystal diffusivities are in the range (1.1−7.2) × 10-11 cm2/s for
propane and (0.2−6.2) × 10-11 cm2/s for propylene.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.