Endothermic conversion vapor

Warm clothing decreases convective heat loss in cold weather. Evaporative cooling occurs when perspiration is generated at the skin surface by the sweat glands (T Figure 5.19). Heat is removed from the body as the perspiration evaporates. Perspiration is predominantly water, so the process is the endothermic conversion of liquid water into water vapor ... 

Reaction 1 is highly exothermic. The heat of reaction at 25°C and 101.3 kPa (1 atm) is ia the range of 159 kj/mol (38 kcal/mol) of soHd carbamate (9). The excess heat must be removed from the reaction. The rate and the equilibrium of reaction 1 depend gready upon pressure and temperature, because large volume changes take place. This reaction may only occur at a pressure that is below the pressure of ammonium carbamate at which dissociation begias or, conversely, the operating pressure of the reactor must be maintained above the vapor pressure of ammonium carbamate. Reaction 2 is endothermic by ca 31.4 kJ / mol (7.5 kcal/mol) of urea formed. It takes place mainly ia the Hquid phase the rate ia the soHd phase is much slower with minor variations ia volume. 

Dehydrogenation. Before the large-scale availabiUty of acetone as a co-product of phenol (qv) in some processes, dehydrogenation of isopropyl alcohol to acetone (qv) was the most widely practiced production method. A wide variety of catalysts can be used in this endothermic (66.5 kj/mol (15.9 kcal/mol) at 327°C), vapor-phase process to achieve high (75—95 mol %) conversions. Operation at 300—500°C and moderate pressures (207 kPa (2.04 atm)) provides acetone in yields up to 90 mol %. The most useful catalysts contain Cu, Cr, Zn, and Ni, either alone, as oxides, or in combinations on inert supports (see Catalysts, supported) (13-16). 

Description The process consists of a reactor section, continuous catalyst regeneration (CCR) section and product-recovery section. Stacked radial-flow reactors (1) facilitate catalyst transfer to and from the CCR catalyst regeneration section (2). A charge heater and interheaters (3) achieve optimum conversion and selectivity for the endothermic reaction. Reactor effluent is separated into liquid and vapor products (4). The liquid product is sent to a stripper column (5) to remove light saturates from the C6 aromatic product. Vapor from the separator is compressed and sent to a gas recovery unit (6). The compressed vapor is then separated into a 95% pure hydrogen coproduct, a fuel-gas stream containing light byproducts and a recycled stream of unconverted LPG. 

In the second step, the dioxanes are vaporized, superheated, and then cracked on a solid catalyst (supported phosphoric acid) in the presence of steam. The endothermic reaction takes place a about 200 to 2S0°C and 0.1 to OJ. 10 Pa absolute. The heat required is supplied by the introduction of superheated steam, or by heating the support of the catalyst, which operates in a moving, fluidized or fixed bed, and, in this case, implies cyclic operation to remove the coke deposits formed. Isoprene selectivity is about SO to 90 mole per cent with once-through conversion of 50 to 60 per cent The 4-4 DMD produces the isoprene. The other dioxanes present are decomposed into isomers of isoprene (piperylene etc.), while the r-butyl alcohol, also present in small amounts, yields isobutene. A separation train, consisting of scrubbers, extractors and distillation columns, serves to recycle the unconverted DMD, isobutene and fonnol, and to produce isoprene to commercial specifications. 

If a batch reactor initially contains 500 lb of acetylated castor oil at 340°C (density 0.90) and the operation is adiabatic, plot curves of conversion (fraction of the acetylated oil that is decomposed) and temperature vs time. It is estimated that the endothermic heat effect for this reaction is 15,000 cal/g mole of acetic acid vapor. The acetylated oil charged to the reactor contains 0.156 g of equivalent acetic acid per gram of oil i.e., complete decomposition of 1 g of the oil would yield 0.156 g of acetic acid. Assume that the specific heat of the liquid reaction mixture is constant and equal to 0.6 Btu/(lb)(°F). Also assume that the acetic acid vapor produced leaves the reactor at the temperature of the reaction mixture. 

Design a reactor system to produce styrene by the vapor-phase catalytic dehydrogenation of ethyl benzene. The reaction is endothermic, so that elevated temperatures are necessary to obtain reasonable conversions. The plant capacity is to be 20 tons of crude styrene (styrene, benzene, and toluene) per day. Determine the bulk volume of catalyst and number of tubes in the reactor by the one-dimensional method. Assume that two reactors will be needed for continuous production of 20 tons/day, with one reactor in operation while the catalyst is being regenerated in the other. Also determine the composition of the crude styrene product. 

Description A heated mixture of ethanol vapor and steam is fed to an adiabatic dehydration reactor (1). The steam provides heat for the endothermic reaction and pushes the reaction to 99-"% conversion of ethanol with 99-"% selectivity to ethylene. Recovered H O is stripped of light ends (2) and recycled as process steam. Product ethylene is compressed and put through a water wash (3) before passing to the ethylene oxide reactor section. 

The enthalpy change for a reaction depends on the states of the reactants and products. If the product in Equation 5.18 were H20(g) instead of H20(/), AH would be —802 kJ instead of —890 kJ. Less heat would be available for transfer to the surroundings because the enthalpy of H20(g) is greater than that of H20(Z). One way to see this is to imagine that the product is initially liquid water. The liquid water must be converted to water vapor, and the conversion of 2 mol H20(() to 2 mol H20(g) is an endothermic process that absorbs 88 kJ ... 

The reaction will be carried out in an adiabatic packed bed. The reaction is endothermic, and cofeeding of hot water vapor into the bed is therefore applied. The conversion level tie = 0.45 is required. Determine the necessary bed length and the temperature of the outlet gas. 

Reactive distillation (RD) is one of the most important reactive separations with potential industrial applications. Here, both reaction and distillation take place within the same zone of a distillation column. It facilitates the instantaneous removal of products in pure form by using distillation principle. New vapor phase of products can be created by either using the heat of reaction in case of exothermic reactions, or by supplying external heat in case of endothermic reactions. Thus reactive distillation provides effective utilization of heat of reaction for product separation and thereby leads to significant reduction in utility consumption. In addition, in-situ removal of products results in improved conversions and yields in case of equilibrium limited reactions, thereby contributing significantly to the overall intensification of the existing process. 

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