Batch autoclave reactor, catalytic

The study of catalytic reactions using a batch autoclave reactor has been criticized for long heat-up times and nonsteady-state catalyst activity. This catalyst-comparison study was carried out by injecting coal tar into a preheated autoclave containing precoked catalyst and hydrogen in order to eliminate long heat-up times. Nevertheless, the inherent differences in results between an autoclave and a trickle-bed reactor, which is widely used for hydrorefining of heavy liquids, exist still (5). 

The prafoimance of foe catalyst for foe CTA hj hopurification was evaluated in a batch autoclave r ictor under conditions similar to those in the indtistry. 90g of CTA containing about 3000 ppm o f 4-CBA and 240 ml of water were chaigrf to foe reactor with Ig catalyst loaded. Hydropurification of foe CTA was conducted at 280ti in foe reactor under stirring (800 rpm) and 0.7 MPa hydrogen pressure. Samples takra after 0.5 h of reaction were analyzed with HPLC [4]. The catalytic performance of foe Pd/CNF catalyst was characterized by 4-CBA s conversion. 

The most common heterogeneous catalytic reaction is hydrogenation. Most laboratory hydrogenations are done on liquid or solid substrates and usually in solution with a slurried catalyst. Therefore the most common batch reactor is a stirred vessel, usually a stirred autoclave (see Figure 2.1.1 for a typical example). In this system a gaseous compound, like hydrogen, must react at elevated pressure to accelerate the process. 

The catalytic ethylene oligomerization was performed in a 0.3 L well-mixed three-phase reactor operating in semi-batch mode, at constant temperature (70 or 150 °C) and pressure (4 MPa of ethylene) in 68 g of n-heptane (solvent). Prior to each experiment, the catalyst was successively pretreated, firstly in a tubular electrical furnace (550 °C, 8 h) and then in the oligomerization autoclave (200 °C, 3 h), under nitrogen flow at atmospheric pressure. After 30 min of reaction, the autoclave was cooled at -20 °C and the products were collected, weighted and analyzed by GC (FID, DB-1 60 m capillary column). 

Discontinuous (batch) processes are carried out in pressure vessels (autoclaves) where DMC is maintained as liquid by autogenous pressure. Instead, CF reactions at atmospheric pressure require that both DMC and the reagent(s) in the vapor phase come into contact with a catalytic bed a constraint that has spurred the development of new applications and alternative reaction engineering, namely, GL-PTC and the continuously fed stirred-tank reactor (CSTR). 

Flow reactors offer considerable advantages over sealed autoclaves for supercritical reactions. Not only do flow-reactors require a much lower volume than a batch reactor for a given throughput of material (with obvious safety advantages) but also it is much easier to optimise reaction conditions in a flow reactor. We have already reported [4,5] the use of a miniature flow-reactor for the photochemical preparation of unstable metal complexes. We are now extending these techniques to the study of thermal and catalytic reactions. As an initial stage we... 

Batch, semibatch, and continuous stirred tank reactors residence time 600 to 15,000 s (10 min to 4 h) heat of reaction primarily exothermic reaction rate slow to moderate. High-pressure autoclaves <100 L. Unique to semibatch phases liquid, gas-liquid, liquid-liquid, gas-liquid catalytic solid. Use where a batch operation is appropriate (Section 16.11.6.24), but one reactant (e.g., gas) needs to be added continuously or if the initial reaction rate is very high. Selectivity is best for parallel reactions. For more details, see CSTR, Section 16.11.6.26. 

The evaluation of catalytic hydrogenation was carried out in batch reactor of 450 mL and under pressure (Parr autoclave). To eliminate the diffusion effects, the reactor was equipped with double-helix stirring device at specific positions near the bottom and on the surface of the reactant (height of the liquid mixture). To visualization of the system. Figure 25.11 presents the reactor used for this example. 

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