Reaction in an Integral Continuous Flow Fixed Bed Reactor

The selectivity to the a-terpinyl methyl ether increases within 9h TOS. However, the selectivity is lowered to 75% at 80 °C while at a lower temperature it increases to 95% during 9 h TOS. 

At the limonene conversion of about 60% and a reaction temperature decreased to 40 °C, selectivities higher than 95% are achieved. A temperature lower than 40 °C causes a noticeable decrease of the limonene conversion. In spite of this, selectivity to a-terpinyl methyl ether remains on the same level of about 95%. The product distribution is nearly the same as in the batch reactor. 

The chosen mass ratio between methanol and limonene of 2 1 is advantageous, because the feedstock and the products are well dissolved at this concentration. However, the excess of methanol can react with 1-methyl-4-[a-methoxyiso-propylj-1-cyclohexene to cis- or /ra 5-l,8-dimethoxy-p-menthane in a consecutive reaction. This reaction is strongly accelerated when the limonene conversion exceeds 90%. That consecutive reaction together with the decomposition of the desired product and other side reactions decrease the selectivity at a high limonene conversion. 

The selectivity to the a-terpinyl methyl ether increases with the reduction of the residence time. The experiments have revealed that not only higher reaction temperature and the limonene conversion above 90%, but also a longer contact time caused by a lower WHSV favor the consecutive reaction of the excess methanol with l-methyl-4-[a-methoxyisopropyl]-l-cyclohexene to cis- or trans-1,8-dimethoxy-p-menthane. 

The application of various linear, iso- and branched alcohols for the addition to limonene in the integral fixed bed reactor gives the same results as those in the batch reactor.  

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