The paper investigates the basics for increasing the productivity of gas-phase catalytic oxidation processes effected in multi-tubular reactors due to their operation at more concentrated feedstock. Obviously, an increase in initial concentration of the oxidizable reagent seems very attractive, but it is associated with the need to modify the process parameters and/or technological chart in order to achieve the required performance figures. This often entails excessive formation of by-products and therefore overheating of the catalyst bed due to increased heat generation. The cumulative effect of many factors can prevent attaining an acceptably high conversion of feedstock and the yield of target products within a reasonable size of a multi-tubular reactor. The problems we studied are quite typical for highly exothermic catalytic oxidation processes, but are not widely discussed in the literature. On the example of nicotinic acid (NA) synthesis in multi-tubular reactor, we investigated the advantages of the process with elevated feed load (β-picoline), in comparison with the conventional conditions. On the basis of comprehensive process simulation supported by the experimental evidence, for the first time we have shown how the process should be operated to achieve a significant progress in the reactor performance and the target product yield. Our theoretical study showed that the rise in the initial β-picoline concentration from ∼0.8 to ∼3% accompanied by a relevant adjusting of the process parameters leads to a dramatic 1.5–2-fold gain in the specific productivity of catalyst; this could greatly improve the reactor capacity. Optionally, a given production capacity of multi-tubular reactor may be ensured by ∼2 times less number of tubes. Thus, the synthesis of NA at elevated initial feed of β-picoline shall be significantly enhanced in comparison with the conventional process.

本文研究了提高多管式反应器中气相催化氧化工艺生产率的基础，这些工艺是由于它们在更高浓度的原料下运行所致。显然，增加可氧化试剂的初始浓度似乎很有吸引力，但这与需要修改工艺参数和/或工艺图以实现所需的性能指标有关。这通常会导致副产物的过量形成，并因此由于增加的热量产生而使催化剂床层过热。在多管式反应器的合理尺寸内，许多因素的累积作用可能会阻止获得可接受的高原料转化率和目标产品的收率。我们研究的问题在高放热催化氧化过程中非常典型，但在文献中并未得到广泛讨论。在多管式反应器中合成烟酸（NA）的示例中，我们研究了与常规条件相比进料量增加（β-甲基吡啶）的方法的优势。在实验证据支持下的全面过程模拟的基础上，我们首次展示了应如何操作该过程以在反应器性能和目标产物收率上取得重大进展。我们的理论研究表明，β-甲基吡啶的初始浓度从〜0.8％升高到〜3％，同时对工艺参数进行了相应的调整，从而使催化剂的比生产率显着提高了1.5到2倍。这可以大大提高反应堆的容量。可选地，可以通过减少约2倍的管数来确保给定的多管反应器生产能力。因此，与常规方法相比，在β-甲基吡啶的初始进料增加时NA的合成将显着增强。