An experimental study of the kinetics of hydrogenation of butynediol has been reported using Pd-Zn-CaC03 catalyst in a slurry reactor. The effects of catalyst loading, butynediol concentration, Hz partial pressure, butenediol (product concentration, temperature, and agitation speed on the rate of hydrogenation have been studied using a stirred pressure reactor. The initial rate data showed that the rate is proportional to the square root of Hz pressure, while increase in butynediol concentration inhibited the reaction. A Langmuir-Hinshelwood-type rate model has been proposed based on these data and the kinetic parameters evaluated. The values of the activation energy E and the heat of adsorption of butynediol (-AH) evaluated were 38.30 kJ/mol and -9.87 kJ/mol, respectively.Batch reactor models were derived based on the rate expression obtained from the initial rate data for variable pressure as well as constant pressure conditions. The predictions of the model were compared with experimental data obtained over a wide range of conditions. The results agreed well within 5-7% error. Use of the pressure vs. time data for evaluation of kinetic and mass transfer parameters is also demonstrated.
SCOPEHydrogenation of butynediol is an industrially important reaction in the manufacture of cis-butenediol, which is a raw material for Endosulfan (insecticide) and vitamin Be. Generally, this reaction is carried out using supported Fe, Ni, or Pd catalysts in a slurry or a trickle-bed reactor. In order to selectively produce cis-butenediol, a modified catalyst has to be used such as Lindlar's catalyst (Pd-CaC03 poisoned with lead or zinc acetate). The purpose of the present work was to investigate the reaction kinetics of hydrogenation of butynediol to butenediol using Pd-Zn-CaC03 catalyst and application to modeling of a batch slurry reactor. Based on this catalyst, a process for butenediol has been developed in our laboratory. A process based on supported Fe catalyst is also described in the BIOS report of Appleyard and Gartshore (1946). The literature information on the reaction (Hoffman et al., 1976, Lindlar andDubuis, 1966; Wood and Ritz, 1976a,b; and Fakuda and Tokishige, 1958) is mostly patented, and practically no attempts to investigate the reaction kinetics have been made so far.In this work, the kinetic data were obtained using Pd-ZnCaC03 catalyst in a stirred slurry reactor operated under isothermal conditions. The effect of various parameters such as catalyst loading, agitation speed, butynediol concentration, partial pressure of Hz, butenediol concentration, and temperature has been investigated. The pressure vs. time data were obtained over a wide range of conditions and the kinetic anal-' ysis was carried out from the initial rates and the integral batch reactor data.Hydrogenation of butynediol is also an interesting threephase catalytic system and provides a good example to study the modeling and scale-up of a three-phase slurry reactor. Very few attempts to model the slurry reactors based on intrinsic kineti...
