The manufacturer of Hastelloy reactors explains why high-pressure reactors are operating more slowly.

　   Hastelloy Reactor The manufacturer explains why the high-pressure reactor is operating more slowly.

　　Hastelloy Reactor Manufacturer: What are the potential reasons for the slow reaction rate in high-pressure reactors?

　　The high-pressure reactor is a special piece of equipment and should be installed in a high-pressure operating room that meets explosion-proof requirements. Like other equipment, the high-pressure reactor employs a conical sealing surface contact via a sealing ring; tightness is achieved by tightening the main bolts to press the components together. A common issue encountered during operation is slow reaction rates. Even after the reaction has stopped, the catalyst must be filtered out, and fresh catalyst must be added to the filtrate before the reaction can resume. Let’s briefly analyze the reasons behind this slow reaction rate—for your reference.

　　 Hastelloy Reactor Manufacturer: Impurities

　　The impurities include carbides, insoluble substances, metal ions, and tar—none of which contain low-molecular-weight impurities, isomers, or residual solvents. Rhenium generally exhibits strong resistance to poisoning; however, the primary target of poisoning is palladium-on-carbon. Carbides mainly consist of various sulfur- and phosphorus-containing compounds in different chemical forms. The pathways through which carbides enter the system include raw materials, solvents, reaction vessels, and gases. Insoluble substances are primarily inorganic compounds or polymers that tend to accumulate on the catalyst surface, blocking active reaction sites and slowing down the reaction. Metal ions—including heavy metals, copper ions, mercury ions, lead ions, and cadmium ions—react with the catalyst, also leading to a slowdown in the reaction rate. The mechanism of action of tar is similar to that of insoluble substances, and it may even form during the reaction itself; therefore, reaction conditions should generally not be set too high. It is difficult to identify impurities using instrumental analysis alone, and their presence can only be confirmed through experimental verification—yet this aspect is often easily overlooked in catalytic hydrogenation processes.

　　 Hastelloy Reactor Manufacturer: Stirred Type

　　The primary purpose of stirring is to ensure thorough mixing of the catalyst at the bottom of the reactor. Since hydrogen has low solubility in the solvent, it typically exists in the reaction system as a gas. The raw materials are dissolved in the solvent and remain in liquid form. The catalyst, being a solid, facilitates the reaction at its surface on a microscopic level. Effective stirring enables gaseous hydrogen and the raw materials to rapidly pass over the catalyst surface, where the reaction takes place, while simultaneously removing the reaction products. In small-scale laboratory experiments, magnetic stirrers are often used because they handle small volumes and, due to the magnetic field's grinding action on the catalyst particles, reactions tend to proceed quickly. During pilot-scale trials, propeller-type impellers prove particularly effective for low-pressure mixing systems. However, since rhenium is relatively heavy, its behavior is significantly influenced by the stirring conditions. By contrast, palladium-on-carbon catalysts, where the palladium metal is adsorbed onto activated carbon, exhibit relatively less sensitivity to stirring effects. In industrial-scale production, where the scale is much larger and stirring efficiency tends to be lower, reactions generally proceed more slowly than in the pilot-scale tests. Traditional anchor-type impellers used in pilot-scale operations lack directional specificity and can mix effectively in either direction. In contrast, propeller-type impellers are directional; they achieve optimal mixing performance only when rotated in the correct direction—reversing the direction drastically reduces their effectiveness.

　　 Hastelloy Reactor Manufacturer: pH value

　　This factor is a critical one that is often overlooked when optimizing catalytic hydrogenation processes. The pH value influences the reaction rate by affecting catalytic activity: rhenium exhibits high activity under alkaline conditions but low activity under acidic conditions. Adding amine compounds can increase the alkalinity of the reaction medium. On the other hand, palladium shows high activity under acidic conditions but low activity under alkaline conditions; however, adding acetic acid can enhance the acidity of the reaction medium. It’s important to note that the acidity and alkalinity should not be excessively high, and strong acids or strong bases must be avoided, as they could compromise equipment stability and affect subsequent processing steps. The above discussion provides an introduction to the issue of slow reaction rates in high-pressure reactors and serves as a reference for further consideration.