EFFECTS OF PROCESS PARAMETERS ON ISOBUTANE 2-BUTENE ALKYLATION USING A SOLID ACID CATALYST/

Alkylation processes based on solid acid catalysts have been studied w ith varying degrees of urgency for the last three decades. Work has fo cused on developing both catalysts and processes. Unfortunately, much of the catalyst development work was done under conditions where catal yst deactivation was rapid and possibly accelerated by the test equipm ent chosen to compare catalysts and conditions. Under these circumstan ces, the true performance of the catalyst for alkylation was not measu red. This paper reports a study of the effect of time-on-stream, olefi n concentration, feed olefin residence time, temperature, and catalyst loading for isobutane/2-butene alkylation using a continuous stirred reactor (CSR) system. A CSR system has been shown to give relatively c onstant activity over much greater times than conventional fixed-bed o r batch reactor systems. The effects of these parameters on olefin con version, useful catalyst lifetime and product quality are reported and initial rate constants, catalyst deactivation rates and an energy of activation for olefin conversion are calculated. In summary, these exp eriments show the dramatic effect of time-on-stream for the reaction o f isobutane and 2-butene, which exhibits four distinct stages of activ ity and selectivity. The first stage is the ''initial activity'', whic h is never actually observed due to experimental limitations but is im portant in kinetic treatment of the data. The second stage is the ''us eful lifetime of the catalyst'', which is characterized by high olefin conversion and relatively slow catalyst deactivation. The third stage is the ''rapid deactivation'' region where a rapid loss of catalyst a ctivity for olefin conversion coupled with a change in selectivity fro m C-5-C-8 products to C9+ products occurs. The fourth stage is where t he product of olefin conversion is primarily C9+ products and the deac tivation is again rather slow. These experiments also show that most c hanges in experimental conditions which increase the concentration of unreacted olefin (e.g., decreasing olefin conversion by increasing fee d olefin concentration, decreasing feed olefin residence time, etc.) d ecreases the catalyst lifetime and product quality. The experiments al so show that there is an optimum reaction temperature which balances t he low olefin conversion at low temperature and the high oligomerizati on activity at high temperature. A set of performance equations from k inetic parameters were derived to describe the conversion of 2-butene under various experimental conditions using a USY catalyst. These perf ormance equations allowed the calculation of initial conversion activi ty, change in conversion activity over time and an estimate of the use ful lifetime of the catalyst.