High-Pressure Reaction Systems

ExxonMobil Chemical Company, On-line Raman analysis and control of a high pressure reaction system. Inventors D.G. Marrow and D.A. Yahn. 11 pp. (inch 3 fig.). Appl. 22 Jul 2005. Int. Cl. C08G 73/00. US Patent Application Publication 2007/0021586 A1... 

This reactor allows easy data collection for high-temperature, high-pressure reaction systems that have difficult flow properties. This includes reactants that are solid at room temperature or mixtures of solids and liquids. Typical reactions performed in autoclaves are coal liquefaction, petroleum residuals and coal liquids upgrading, and high molecular weight hydrogenation experiments. 

A more significant method for testing the agreement of the flow and static system results is to use the high-pressure flow system value of kx at 477 °C, and the static system value at 258 °C. These values give kx = 1.6 x 109 exp(—34,000IRT) sec-1. There is obviously a serious discrepancy between the two methods. A possible source of error in the static system work is the neglect of reaction (14)... 

The autoclave reactor is a small cylindrical reactor, built to withstand high pressures, used to evaluate the kinetics of high-temperature, high-pressure reactions and the production of small quantities of specialty chemicals. The reactor is typically packed with a supported catalyst, and reactant is added by injection. Pressure in the system is elevated by increasing the temperature of the autoclave. Additional pressure, if needed, can be obtained with the injection of additional gaseous reactant or an inert. 

CLOSED SYSTEM - no material is exchanged with the surroundings (e.g. autoclave - a sealed vessel for carrying out high pressure reactions). 

Processing equipment consists of the material conditioning system, the high-pressure metering system, the mixing head, and the mold carrier. Since the RIM process involves a chemical reaction in the mold after the intermediates have been mixed, it is necessary, if consistent parts are to be produced, that the material delivered to the mix head be consistent from shot to shot. 

It is possible that these represent secondary synthetic products, possibly from the reaction of the CO and H2 released, catalysed by the lunar fines84 These secondary reactions occur to a greater extent in the high pressure pyrolysis system this was tested by addition at 700 °C of CO and H2 to a previously pyrolysed lunar sample, traces of benzene being synthesised. 

Steam methane reforming is performed in a high-temperature, high-pressure reaction chamber typically operating between 1,250 to 1,575°C at pressures of 20 to 100 atmospheres. Materials issues are the same as those of high-temperature, high-pressure vessels where creep of corrosion-resistant materials is important for the containment vessel and durability of alumina, chromia, or SiC refractory lining materials is critical to the performance of the system. 

In addition to control of the product distribution, the attainment of much higher reaction rates is essential for practical use. Recently, the electrochemical reduction of COj with high current density has been studied by many researchers, e.g., using high pressure aqueous systems [7] and gas diffusion electrodes [8], We... 

Under some specific conditions, the formation of UV DBFs is worth considering. UV irradiation can cause a series of oxidation reactions, leading to the formation of oxidative by-products, especially if high-pressure UV systems are applied and the organic contents in the water are high (35). Some DBFs can be formed due to the production of powerful free radicals (e.g., OH-) in the water. The resulting concentrations and the types of DBFs depend on the concentrations of the organic substances (e.g., NOM) and the UV dose. 

However, there are many reactions in gas/liquid systems, in which a high gas throughput is not required e.g. because the micro-kinetics are rate-determining. In such circumstances the hollow stirrer due to its dual role as stirrer and gas pump is the stirrer type of choice, particularly in high pressure reaction engineering. 

The stored energy of high-pressure gas systems makes such reactions quite hazardous, and so they are performed on a small scale ca. 1 g). The maximum pressure available for each gas is dependent on the gas in question, as phases liquefy at different pressures. The upper limit of these reactions is 18 kbar (1.8 GPa) for argon-based vessels. Here it is the absolute pressure that is the important factor, and not the type of gas. 

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