Catalytic flowsheets

Figure 13.5 shows a flowsheet for the manufacture of phthalic anhydride by the oxidation of o-xylene. Air and o-xylene are heated and mixed in a Venturi, where the o-xylene vaporizes. The reaction mixture enters a tubular catalytic reactor. The heat of reaction is removed from the reactor by recirculation of molten salt. The temperature control in the reactor would be diflficult to maintain by methods other than molten salt. 

Figure 2. Catalytic reforming flowsheet. (Used with permission of Simulation Sciences Inc.)...

Ethyl chloride (C2H5CI) can be manufactured by catalytically reacting ethanol and hydrochloric acid (El-Halwagi et al., 1996). Figiu 7.7 is a simplified flowsheet of... 

Figure 33.3. AspenPlus flowsheet of the catalytic reactive distillation process.

However, the chemical reactor still requires considerable thinking and hand calculations because there are few situations where databases exist on reaction kinetics. Especially for catalytic reactions, data either do not exist or are uniehable far from the conditions under which the data were obtained. The number of possibUities of catalyst chemical and geometrical properties are so large that no flowsheet programs can handle anything beyond extremely simple situations. 

Processes often differ in terms of the process conditions, e.g. high-pressure and low-pressure processes, or the type of reactor that is used, e.g. gas-phase catalytic reactor or liquid-phase CSTR. These differences should be clearly marked on both the simple block diagrams for each process and the detailed process flowsheets, they often determine which process route is ultimately selected. Many older, established processes were operated under conditions of high pressure or high temperature (mainly in the reactor), whereas the newer processes have often been improved by operation under less severe conditions. 

Figure 5.9 presents the flowsheet prior to heat integration. Fresh and recycled phenol is evaporated and mixed with hydrogen in the evaporator (Ev-1) at about 2 bar. The gas mixture enters the catalytic hydrogenation reactor (R-l). The inlet temperature should be kept strictly constant, in this case at 150°C, to avoid the... 

Figure 6.15 presents a compact flowsheet based on catalytic distillation, as simulated with Aspen Plus [9], Benzene and propylene are fed in countercurrent in... 

Figure 6.15 Flowsheet for cumene synthesis making use of catalytic distillation.

Figure 7.13 presents a simplified flowsheet, which concentrates the essential features the balanced VCM technology, as conceptually developed in the previous sections, but this time with the three plants and recycles in place chlorination of ethylene (Rl), thermal cracking of EDC (R2) and oxyclorinahon of ethylene (R3). As mentioned in Section 7.3, from plantwide control three impurities are of particular interest (I]) chloroprene (nbp 332.5 K), (12) trichloroethylene (nbp 359.9K), and (13) tetrachloromethane (nbp 349.8). I, and 12 are bad , since the first can polymerize and plug the equipment, while the second favors the coke formation by EDC pyrolysis. On the contrary, I3 has a catalytic effect on the VCM formation, in some patents being introduced deliberately. 

Equipment. In designing the apparatus to be used for the hydro-treating and hydrocracking of SRC, heavy reliance was placed on the petroleum-processing experience in the Houdry Division of Air Products. A continuous process development unit was designed and constructed to catalytically hydroprocess nominally 1 L/hr of SRC liquid. A simplified flowsheet of the unit appears in Figure 1. 

Fig. 3.1. Sulfur burning flowsheet - molten sulfur to clean dry 700 K S02, 02, N2 gas. The furnace is supplied with excess air to provide the 02 needed for subsequent catalytic oxidation of S02, to SO3. Table 3.1 gives industrial sulfur burning data.

Fig. 5.1. Spent sulfuric acid regeneration flowsheet. H2S04(f) in the contaminated spent acid is decomposed to S02(g), 02(g) and H20(g) in a mildly oxidizing, 1300 K fuel fired furnace. The furnace offgas (6-14 volume% S02, 2 volume% 02, remainder N2, H20, C02) is cooled, cleaned and dried. It is then sent to catalytic S02 + Vi02 —> S03 oxidation and H2S04 making, Eqn. (1.2). Air is added just before dehydration (top right) to provide 02 for catalytic S02 oxidation. Molten sulfur is often burnt as fuel in the decomposition furnace. It provides heat for H2S04 decomposition and S02 for additional H2S04 production. Tables 5.2 and 5.3 give details of industrial operations.

Fig. 9.1. Single contact H2SO4 making flowsheet. SO3 rich gas from catalytic SO2 oxidation is reacted with strong sulfuric acid, Reaction (1.2). The reaction consumes H20(f) and makes H2S04(f), strengthening the acid. Double contact H2SO4 making is described in Fig. 9.6. A few plants lower the SO2 content of their tail gas by scrubbing the gas with basic solution (Hay et al., 2003).

Description The flowsheet for an oxygen-based unit is one of several possible process schemes. Compressed oxygen, ethylene and recycle gas are mixed and fed to a multitubular catalytic reactor (1). The temperature of oxidation is controlled by boiling water in the shell side of the reactor. 

Fig. 2. Flowsheet of a typical FCCU. 1, riser 2, disengager 3, FFB regenerator 4, catalyst cooler 5, main fractionator 6, LCO stripper 7, HCO drum 8, accumulator I, fresh feed II, recycle feed III, slurry oil IV, LCO V, catalytic naphtha VI, rich gas VII, air VIII, flue gas IX, steam X, water/steam mixture XI, water.

Figure 3.17 Flowsheet of a waste plastic liquefaction plant based on thermal cracking and subsequent catalytic reforming [102]. (Reproduced by permission of the International Solid Waste Association (ISWA))...

There were 820 million pounds of phthalic anhydride produced in the United States in 1995. One of the end uses of phthalic anhydride is in the fiberglass of sailboat hulls. Phthalic anhydride can be produced by the partial oxidation of naphthalene in either a fixed or a fluidized catalytic bed. A flowsheet for die commercial process is shown in Figure P3-11. Here the reaction is carried out in a flxed-bed reactor with a vanadium pentoxide catalyst packed in 25 -mm-diameter tubes. A production rate of 31,000 tons pet year would require 15,000 tubes. 

The accompanying figure represents the schematic flowsheet of a distillation tower used to recover gasoline from the products of catalytic cracker. Is the problem completely specified, that is, is the number of degrees of freedom equal to zero for the purpose of calculating the heat transfer to the cooling water in the condenser ... 

Figure E5.8 is a hypothetical process used for demonstration by Diamond Shamrock Co. of their flowsheeting code PROVES. Makeup gas is compressed, combined with recycle gas, and fed, together with liquid raw material, into a three-phase, suspended bed catalytic reactor. The reactor is cooled by recirculating liquid through a heat reclamation steam generator. Reaction products are condensed and the pressure of the exit stream reduced in two stages. The gas from the first-stage separator is recirculated, whereas the liquid from the second-stage separator is fed into a distillation column. Pure product is withdrawn from the bottom of the column. The distillate is a by-product that is pumped to another plant.

The above flowsheet can be simplified tremendously by catalytic distillation. Figure 7.32 depicts a conceptual configuration. The RD column consists of a reactive zone at the top, and a distillation section at the bottom. The reaction mixture is sent to a purification column, from which ethylbenzene is obtained as top distillate. A side-stream containing PEB is sent to transalkylation for EB recovery. Obviously, the feasibility of this process depends largely on the availability of an active and selective catalyst. For zeolites the optimal operating conditions are about pressure around 3 MPa, temperature less than 200 °C, and reaction rate capable to give a space-time of 5 h" for almost complete ethylene conversion. 

The catalytic dealkylation of toluene to benzene involves recycling of unreacted toluene after removal of by-product phenylbenzene. Using the information shown on the process flowsheet (Figure 7.11) determine... 

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