Effect of rhenium additives to alumina-platinum catalysts on the conversion of n-heptane

Abstract

IN ORDE~ to prepare gasoline with an octane number of 93 and more straightrun paraffin gasohnes were subjected to catalytic reforming at increased temperature and contact time. The following disadvantages normally characterize reforming of gasolines under strictly defined conditions with alumina-plat inum catalysts: low yield of reforming-gasoline (76-80%), relatively rapid coking o f the catalyst and consequently, short periods between regenerations and short general service life of catalysts. The development of stable catalysts is therefore of foremost significance for reforming plants using paraffin gasoline fractions with a high degree of aromatization. Reports on the development of "rheniforming"* [1-5] pubhshed in the literature are therefore of interest; according to these reports the addition of rhenium to an alumina-plat inum catalyst promotes more satisfactory dispersion of platinum and stabilization during operation. This appears likely since rhenium metal is highly heat resistant (m.p. 3170°). Considerable confusion is created by the report concerning the addition of rhenium to an aluminaplat inum catalyst which alters the selectivity of chemical reactions and reduces coke and gas yield. According to the authors, this is the reason why the apphcation of an alumina-plat inum-rhenium catalyst enables the process to be carried out at pressures which are reduced compared with those of ordinary reforming and with a 3 : 1 circulation of hydrogen and accordingly at approximately 50 % higher efficiency related to the raw material [5]. Results are given in this paper concerning the effect of rhenium additives on an alumina-plat inum catalyst for n-heptane conversion under impulse conditions.