Ethylene reactor performance

The effect of physical processes on reactor performance is more complex than for two-phase systems because both gas-liquid and liquid-solid interphase transport effects may be coupled with the intrinsic rate. The most common types of three-phase reactors are the slurry and trickle-bed reactors. These have found wide applications in the petroleum industry. A slurry reactor is a multi-phase flow reactor in which the reactant gas is bubbled through a solution containing solid catalyst particles. The reactor may operate continuously as a steady flow system with respect to both gas and liquid phases. Alternatively, a fixed charge of liquid is initially added to the stirred vessel, and the gas is continuously added such that the reactor is batch with respect to the liquid phase. This method is used in some hydrogenation reactions such as hydrogenation of oils in a slurry of nickel catalyst particles. Figure 4-15 shows a slurry-type reactor used for polymerization of ethylene in a sluiTy of solid catalyst particles in a solvent of cyclohexane. 

Simulation studies are also conducted for a dispersed PFR and a recycle reactor at 260 °C, 500 psig and feed with DCPD=0.32 mol/min, CPD=0.96mol/min and ethylene=3.2mol/min. Peclet number (Pe) or the recycle ratio is selected as a variable parameter for the dispersed PFR or for the recycle reactor, respectively. Conversion approaches to that of PFR over Pe=50 as can be seen in Fig.4. It is also worth mentioning that the reactor performance is improved with recycle if the residence time is low. 

As the temperature at which significant initiator decomposition takes place depends on the initiator itself, a successful operation of the reactor requires a proper choice of the initiator in many cases, suitable mixtures of different initiators are also used. The reactor performances are often enhanced by a proper use of multiple feed streams of cold ethylene and/or initiator (s). 

Note that the reactor is affected, even with a constant total acetic acid flow. Both the ethylene and the oxygen fresh feeds increase temporarily, indicating an increase (though not permanent) in reaction rate. This is due to complicated interactions within the process dealing with vaporizer performance, fresh acetic acid feed and bottoms temperatures, and the reactant concentrations as they affect reactor performance. 

In porous composite membranes, the support layer(s) can play an important role in the reactor performance. This, for example, is the case with consecutive reactions such as partial oxidations where intermediate products are desirable. Harold et al. [1992] presented a concept in which two reactants are introduced to a two-layer membrane system from opposite sides ethylene on the membrane side while oxygen on the support side. The mass transfer resistance of the support layer lowers the oxygen concentration in the catalytic zone and directs the preferred intermediate product, acetaldehyde, toward the membrane side. Thus the support layer structure enhances the yield of acetaldehyde. 

K. Comparing the reactor performance, it can be seen that - just as in the isothermal case - 7 to 8% higher conversion values are obtained with the simple ID model (Fig. 5.21b). This higher conversion is responsible for the increased hotspot temperature, and shows once more the limitations of the ID modeL The ethylene selectivity and also the conversion obtained by the 2D models are identical within 1%. 

Ragaini, V., De Luca, G., Ferrario, B., et al. (1980). A Mathematical Model for aTubular Reactor Performing Ethylene Oxidation to Ethylene Oxide by a Catalyst Deposited on MetaUic Strips, Chem. Eng. ScL, 35, pp. 2311-2319. 

In order to illustrate heat integration opportunities and thus also to estimate the utility savings potential, a background/foreground (BF) analysis of the two processes was performed. Figure 4.9 shows the BF analysis of the combined processes. It can be seen that there is an opportunity to recover 44.5 MW of excess heat in the ethanol dehydration process and deliver it to the ethanol production process. As mentioned previously, most of the excess heat at higher temperatures originates from the ethylene reactor effluent. The hot ethylene reactor effluent stream is cooled from 428 to 84 C and has a relatively... 

Ethylene oxide catalyst research is expensive and time-consuming because of the need to break in and stabilize the catalyst before rehable data can be collected. Computer controlled tubular microreactors containing as Httle as 5 g of catalyst can be used for assessment of a catalyst s initial performance and for long-term life studies, but moving basket reactors of the Berty (77) or Carberry (78) type are much better suited to kinetic studies. 

Oxychlorination of ethylene to dichloroethane is the first reaction performed in an integrated vinyl chloride plant. In the second stage, dichloroethane is cracked thermally over alumina to give vinyl chloride and hydrogen chloride. The hydrogen chloride produced is recycled back to the oxychlorination reactor. 

Removal of metal chlorides from the bottoms of the Hquid-phase ethylene chlorination process has been studied (43). A detailed summary of production methods, emissions, emission controls, costs, and impacts of the control measures has been made (44). Residues from this process can also be recovered by evaporation, decomposition at high temperatures, and distillation (45). A review of the by-products produced in the different manufacturing processes has also been performed (46). Several processes have been developed to limit ethylene losses in the inerts purge from an oxychlorination reactor (47,48). 

In well-established processes, like ethylene oxidation to ethylene oxide, quality control tests for a routinely manufactured catalyst can be very simple if the test is developed on the basis of detailed kinetic studies and modeling of the performance in a commercial reactor. Tests must answer questions that influence the economics of the commercial process. The three most important questions are ... 

Development of the first recycle reactor was one of the consequences of a challenging situation. The ethylene oxide process had reached a high level of sophistication and excellent performance after 25 years of continuous R D. To improve results achieved by so many excellent people over so many years was a formidable task. 

Alkanes and Alkenes. For this study, C150-1-01 and C150-1-03 were tested under primary wet gas conditions with ethylene, ethane, propylene, and propane being added to the feed gas. This study was made in order to determine whether these hydrocarbons would deposit carbon on the catalyst, would reform, or would pass through without reaction. The test was conducted using the dual-reactor heat sink unit with a water pump and vaporizer as the source of steam. All gas analyses were performed by gas chromatography. The test was stopped with the poisons still in the feed gas in order to preserve any carbon buildup which may have occurred on the catalysts. 

The photocatalytic experiments were performed in a horizontal quartz tube which it have TiOi. Illumination was provided by 500 W mercury lamps, located above the horizontal quartz tube. The reactant was 0.1% (v/v) ethylene in air. In case of Photo-Catalyst test, reactor effluent samples were taken at 30 min intervals and analyzed by GC. The composition of hydrocarbons in the feed and product stream was analyzed by a Shimadzu GC14B (VZIO) gas chromatograph equipped with a flame ionization detector. In all case, steady state was reached within 3 h. 

In summary, the results from the fixed bed reactor study provided evidence as to the effect of Au and KOAc on the performance of the catalyst, though, these experiments did not give any information on the perturbation of the reaction pathways with the addition of Au and KOAc. For this type of information, additional experiments were performed using the TAP reactor with 1,2 C-labeled ethylene used as an isotopic tracer of the kinetics. 

Activities of the catalysts were measured on a microreactor. About 3 g of catalyst was charged into a reactor and heat-treated in nitrogen at reaction temperature. Acetic acid was added to the process and the reaction was initiated by switching nitrogen to ethylene. Reaction product analyses were performed by an online gas chromatograph equipped with a flame ionization detector (Perkin Elmer Auto System II). 

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). 

Some experimental studies (1-7) have demonstrated the possibility of improving the performance of a catalytic reactor through cyclic operation. Eenken et al. (4) reported an improvement of 70% in conversion of ethylene to ethane under periodic operation. In a later article (2), they concluded that periodic operations can be used to eliminate an excessively high local temperature inside the catalytic reactor for a highly exothermic reaction. In our laboratory, Unni et al. (5) showed that under certain conditions of frequency and amplitude associated with the forced concentration cycling of reactants, the rate of oxidation of SC>2 over catalyst can be increased by as much as 30%. Re-... 

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