Reactors reactions

LDPE, also known as high pressure polyethylene, is produced at pressures ranging from 82—276 MPa (800—2725 atm). Operating at 132—332°C, it may be produced by either a tubular or a stirred autoclave reactor. Reaction is sustained by continuously injecting free-radical initiators, such as peroxides, oxygen, or a combination of both, to the reactor feed. 

Continuous-flow stirred-tank reactors ia series are simpler and easier to design for isothermal operation than are tubular reactors. Reactions with narrow operating temperature ranges or those requiring close control of reactant concentrations for optimum selectivity benefit from series arrangements. 

It is not possible, however, to calculate accurately actual gas composition by using the relationships of reactions (27-14) to (27-19) in Table 27-12. Since the gasification of coal always takes place at elevated temperatures, thermal decomposition (pyrolysis) takes place as coal enters the gasification reactor. Reaction (27-15) treats coal as a compound of carbon and hydrogen and postulates its thermal disintegration to produce carbon (coke) ana methane. Reaction (27-21) assumes the stoichiometiy of hydrogasifying part of the carbon to produce methane and carbon. 

In the gas-cooled reactor, reaction.between the coolant and the moderator results in formation of a proportion of carbon monoxide in the atmosphere. This gas can be carburising to nickel-base alloys but the results of tests in which CO2 was allowed to react with graphite in the furnace indicate that the attack on high-nickel alloys is slight, even at moderately high temperatures and is still mainly due to simple oxidation. 

A microchannel reactor for CO preferential oxidation was developed. The reactor was consisted of microchannel patterned stainless steel plates which were coated by R11/AI2O3 catalyst. The reactor completely removed 1% CO contained in the Ha-rich reformed gas and controlled CO outlet concentration less than Ippm at 130 200°C and 50,000h. However, CH4 was produced from 180"C and CO selectivity was about 50%. For high performance of present PrOx reactor, reaction temperature should be carefully and uniformly controlled to reach high CO conversion and selectivity, and low CH4 production. It seems that the present microchaimel reactor is promising as a CO removal reactor for PEMFC systems. 

Reactor type Electrochemical sheet micro flow reactor Reaction medium layer depth 600 pm... 

Micro reactors show, under certain conditions, low axial flow dispersion reactions with unstable intermediates can be carried out in a fast, stepwise manner on millisecond time-scales. Today s micro mixers mix on a millisecond scale and below [40]. Hence in micro reactors reactions can be carried out in the manner of a quench-flow analysis, used for determination of fast kinetics [93]. 

The predictive power of tendency models is obviously limited. However, the models can be useful in evaluation of the effect of changing heat-transfer conditions upon scale-up of reactors. Tendency models can be extremely useful for improvement and optimization of existing industrial reactors/reactions, especially for the improvement of the time-temperature policy and the policy of addition of component(s) to the reaction mixture. 

The forms of actual tracer response curves may be used to formulate models of the actual mixing processes in the reactor. One has, however, to be careful since the tracer response curve does not give a unique solution. It does, for example, not allow one to distinguish between early and late mixing, which may be important when used in the estimation of conversion in a particular reactor-reaction system. 

Hydrolytic Kinetic Resolution (HKR) of epichlorohydrin. The HKR reaction was performed by the standard procedure as reported by us earlier (17, 22). After the completion of the HKR reaction, all of the reaction products were removed by evacuation (epoxide was removed at room temperature ( 300 K) and diol was removed at a temperature of 323-329 K). The recovered catalyst was then recycled up to three times in the HKR reaction. For flow experiments, a mixture of racemic epichlorohydrin (600 mmol), water (0.7 eq., 7.56 ml) and chlorobenzene (7.2 ml) in isopropyl alcohol (600 mmol) as the co-solvent was pumped across a 12 cm long stainless steel fixed bed reactor containing SBA-15 Co-OAc salen catalyst (B) bed ( 297 mg) via syringe pump at a flow rate of 35 p,l/min. Approximately 10 cm of the reactor inlet was filled with glass beads and a 2 pm stainless steel frit was installed at the outlet of the reactor. Reaction products were analyzed by gas chromatography using ChiralDex GTA capillary column and an FID detector. 

In the chlorination of ethylene to produce dichloroethane (DCE), the conversion of ethylene is reported as 99.0 per cent. If 94 mol of DCE are produced per 100 mol of ethylene fed, calculate the overall yield and the reactor (reaction) yield based on ethylene. The unreacted ethylene is not recovered. 

Table 5 Hydrogenolysis of AcOBu on lRelPt(e,red) catalyst in SPR16 reactor. Reaction order for AcOBu and apparent activation energy.

Another synthesis technology which has just started to impact and change the way chemical synthesis is performed in many laboratories is microwave assisted organic synthesis. Using microwave reactors, reaction times often can be reduced from hours or days to minutes or even seconds. Selectivities and yields often can be increased drastically. Therefore, this technology has the potential to increase the output of chemical drug discovery units enormously. An important question in this field is how to scale up these transformations in microwave reactors up to kilogram scale. 

Fig. 5. Methane conversion and oxygen flux during partial oxidation of methane in a ceramic membrane reactor. Reaction conditions pressure, 1 atm temperature, 1173 K, feed gas molar ratio, CH Ar = 80/20 feed flow rate, 20 mL min-1 (NTP) catalyst mass, 1.5 g membrane surface area, 8.4 cm2 (57).

Batch microwave reactors, reactions in, 16 554-555 Batch mixers, 16 721 Batch mononitrotoluene process, 17 265 Batch multipurpose plants, for fine chemical manufacture, 11 427 Batch nitrobenzene process, 17 252 Batch-operated settling tanks, 22 59 Batch pilot plants, 19 458 Batch plants, certified, 20 703 Batch polymerization, of vinyl acetate, 25 608... 

Figure 11.26 Plot of the position sensitivity of the degree of conversion for a set of 48 bismuth-molybdate catalysts (same batch) in propylene to acrolein conversion in a Stage II 48-fold-screening reactor (reaction conditions 2% hydrocarbon in air at GHSV of 3000 h-1, column no. 8 contains only inert carrier material).

Year and reference Reactor/reaction Esterification, free EG Esterification, tlXi Polycondensation DEG formation AA formation 0 Diester group degradation 0 Polycondensation of vinyl groups ... 

The activated Ba(OH)2 was used as a basic catalyst for the Claisen-Schmidt (CS) condensation of a variety of ketones and aromatic aldehydes (288). The reactions were performed in ethanol as solvent at reflux temperature. Excellent yields of the condensation products were obtained (80-100%) within 1 h in a batch reactor. Reaction rates and yields were generally higher than those reported for alkali metal hydroxides as catalysts. Neither the Cannizaro reaction nor self-aldol condensation of the ketone was observed, a result that was attributed to the catalyst s being more nucleophilic than basic. Thus, better selectivity to the condensation product was observed than in homogeneous catalysis under similar conditions. It was found that the reaction takes place on the catalyst surface, and when the reactants were small ketones, the rate-determining step was found to be the surface reaction, whereas with sterically hindered ketones the adsorption process was rate determining. 

A stream of fully suspended fine solids (v = 1 mVmin) passes through two mixed flow reactors in series, each containing 1 m of slurry. As soon as a particle enters the reactors, conversion to product begins and is complete after two minutes in the reactors. When a particle leaves the reactors, reaction stops. What fraction of particles is completely converted to product in this system ... 

Fluidized bed reactors typrcally are vertical cylindrical vessels equipped with a support grid and feed sparger system for adequate fluidization and feed distribution, internal cooling coils for heat removal, and either external or internal cyclones to minimize catalyst carryover. Fluidizauon of the catalyst assures intimate contact between feed and product vapors, catalyst, and heat-transfer surfaces, and results in a uniform temperature within the reactor. Reaction heat can be removed by generating steam within the cooling coils or by some oilier heat-transfer medium. 

The most active formulation (ZSNbPt) was tested in a conventional reactor using as feedstream a mixture of light n-alkanes [n-pentane (20 wt%), n-hexane (60 wt.%) and n-heptane (20 wt%)] to simulate an industrial stream. Experiments were carried out in a conventional reaction system using a fixed-bed continuous -flow reactor. Reaction was carried out under the same conditions as the poisoning resistance experiments. The activity and selectivity of this catalyst (Fig. 5.13) have been compared with those obtained with sulfated zirconia impregnated with platinum (ZS). Fig. 5.13 represents the evolution of the conversion with reaction temperature. Clearly, the reactivity of the n-paraffm follows the order n-heptane > n-hexane > n-pentane for both catalysts, as expected when taking into account the adsorption heats of the different hydrocarbons [34]. 

---