Reaction in Vessels

The mixture is heated, in the presence of the catalyst, and the reaction forms hydrocarbon vapours. In the presence of the catalyst, the long chains are broken and the molecules regroup into lighter hydrocarbon fractions and light gases, when cooled and condensed, the vapours attain the state of a light hydrocarbon fuel such as petrol. 

The vapours consist of two phases, condensable gases and noncondensable gases. 

---

This reaction, which proceeds in accordance with the equation S02C12 = S02 + Cl2, is not a homogeneous reaction in vessels of ordinary soda glass. Using vessels of Pyrex glass, however, D. F. Smith found that the reaction was... 

Second explosion limits and the slow reaction in vessels having very low surface destruction efficiencies for hydroperoxyl and hydrogen peroxide... 

In a semicontinuous or batch flow process, one or more ingredient is charged to the reactor, and the remaining components are added gradually. None of the reaction mixture is displaced through overflow. The total volume of a vessel usually increases as the reaction progresses, and the product is isolated at the end of the operation cycle. This type of operation is useful for exothermic reactions in vessels with limited heat transfer capacity. 

One of the methods of estimating the wall effect on a chemical reaction is to study the reaction in vessels with a different ratio S/V of the wall surface area to the reactor volume. If the reaction rate or composition of products depend on S/V, this is evidence that the reaction involves heterogeneous steps, i.e. such that occur at the reactor wall. 

Even so, the mixing rates will still be moderate, and will generally be slow compared to the rates of most chemical reactions. In vessels diat are not larger than say 5 m, circulation times on the order of 10 s may still be realized. 

Merging more than one operation into a single piece of equipment (e.g., feed preheating and reaction in the same vessel), providing these operations are not limiting the cycle time. 

This is a disproportionation reaction, and is strongly catalysed by light and by a wide variety of materials, including many metals (for example copper and iron) especially if these materials have a large surface area. Some of these can induce explosive decomposition. Pure hydrogen peroxide can be kept in glass vessels in the dark, or in stone jars or in vessels made of pure aluminium with a smooth surface. 

An even less complicated reaction vessel may be used for reactions in liquid amtnonia which produce only a small amount of "heat" over a relatively long period and which proceed under homogeneous conditions. The conversion can then be performed in a one-necked flask with a stopper + gas outlet or small hole. 

Reductive alkylations and aminations requite pressure-rated reaction vessels and hiUy contained and blanketed support equipment. Nitrile hydrogenations are similar in thein requirements. Arylamine hydrogenations have historically required very high pressure vessel materials of constmction. A nominal breakpoint of 8 MPa (- 1200 psi) requites yet heavier wall constmction and correspondingly more expensive hydrogen pressurization. Heat transfer must be adequate, for the heat of reaction in arylamine ring reduction is - 50 kJ/mol (12 kcal/mol) (59). Solvents employed to maintain catalyst activity and improve heat-transfer efficiency reduce effective hydrogen partial pressures and requite fractionation from product and recycle to prove cost-effective. 

Aqueous sulfamic acid solutions are quite stable at room temperature. At higher temperatures, however, acidic solutions and the ammonium salt hydroly2e to sulfates. Rates increase rapidly with temperature elevation, lower pH, and increased concentrations. These hydrolysis reactions are exothermic. Concentrated solutions heated in closed containers or in vessels having adequate venting can generate sufficient internal pressure to cause container mpture. An ammonium sulfamate, 60 wt % aqueous solution exhibits mnaway hydrolysis when heated to 200°C at pH 5 or to 130°C at pH 2. The danger is minimised in a weU-vented container, however, because the 60 wt % solution boils at 107°C (8,10). Hydrolysis reactions are ... 

Ferrovanadium can also be prepared by the thermite reaction, in which vanadium and iron oxides are co-reduced by aluminum granules in a magnesite-lined steel vessel or in a water-cooled copper cmcible (11) (see Aluminumand aluminum alloys). The reaction is initiated by a barium peroxide—aluminum ignition charge. This method is also used to prepare vanadium—aluminum master alloys for the titanium industry. 

Packed Red Reactors The commonest vessels are cylindrical. They will have gradients of composition and temperature in the radial and axial directions. The partial differential equations of the material and energy balances are summarized in Table 7-10. Example 4 of Modeling of Chemical Reactions in Sec. 23 is an apphcation of such equations. 

Topics that acquire special importance on the industrial scale are the quality of mixing in tanks and the residence time distribution in vessels where plug flow may be the goal. The information about agitation in tanks described for gas/liquid and slurry reactions is largely apphcable here. The relation between heat transfer and agitation also is discussed elsewhere in this Handbook. Residence time distribution is covered at length under Reactor Efficiency. A special case is that of laminar and related flow distributions characteristic of non-Newtonian fluids, which often occiu s in polymerization reactors. 

Although they are termed homogeneous, most industrial gas-phase reactions take place in contact with solids, either the vessel wall or particles as heat carriers or catalysts. With catalysts, mass diffusional resistances are present with inert solids, the only complication is with heat transfer. A few of the reactions in Table 23-1 are gas-phase type, mostly catalytic. Usually a system of industrial interest is liquefiea to take advantage of the higher rates of liquid reactions, or to utihze liquid homogeneous cat ysts, or simply to keep equipment size down. In this section, some important noncatalytic gas reactions are described. 

Vessel Filled with Reactive Gas Mixtures Most cases of damage arise not from the vessel failing at its normal operating pressure but because of an unexpected exothermic reaction occurring within the vessel. This usually is a decomposition, polymerization, deflagration, runaway reaction, or oxidation reaction. In assessing the damage... 

Inactive and/or wrong catalyst. Possibility for accumulation of reactant and subsequent runaway reaction in reactor or downstream vessel. Possibility of no reaction resulting in a waste disposal issue. 

Reactor contents inadvertently admitted to upstream feed vessel. Possibility of reaction in piping and vessel. 

Types of damage can be classified as uniform or localized metal removal, corrosion cracking or detrimental effects to the environment from the corrosion products. Local attack can take the form of shallow pits, pitting, selective dissolution of small microstructure regions of the material or cracking. Detrimental effects are certainly not the case with buried pipelines, but have to be considered for environments in vessels and containers. It is usual, where different results of reactions lead... 

Tipnis, S. K., Penny, W. R., and Fasano, J. B., An experimental investigation to determine a scale-up method for fast competitive parallel reactions in agitated vessels, AIChE Annual Meeting, St. Louis, November 1993. 

Domino reactions, in which a series of carefully planned reactions occurs in a single vessel, used to prepare complex biologically active organic compounds (Hall, 1994 Tietze, 1995). 

The photochemical addition of trifiuoroiodomethane to unsaturated systems has been thoroughly investigated by Haszeldine. Little use has been made of this reaction in the steroid field. Irradiation of the enol ether (64) in trifiuoroiodomethane containing pyridine in a quartz vessel furnishes in 60 %... 

---