Phthalic anhydride reactor

T emperalufe can be Ftermined by m ns of this simplified procedure. Problem 13-6 illustrates calculations for a phthalic anhydride reactor. The oxidation of naphthalene has a high heat of reaction, so that the size of the catalyst tubes is a critical point in the design. 

Figure 9.3 Maximum centerline temperature for a phthalic anhydride reactor for Twaii = 640 K and inlet temperatures of 500 and 600 K.

Gibson, S.B., 1976. The design of new chemical plant using hazard analysis. Process Industry Hazards, Symposium Series No. 47. 135 (IChemE. Rugby. UK). HSE, 1992, Tolerability of Risk from Nuclear Power Stations, revised edition. Pantony, M.F.. Scilly. N.F. and Barton. J.A.. 1989. Safety of exothermic reactions a UK strategy, Int Symp on Runaway Reactions. 504—524 (CCPS, AIChE. USA). Kauffman, D. and Chen, H-J.. 1990, Fault-dynamic modelling of a phthalic anhydride reactor, J Loss Prev Process hid. 3 386-394. 

Johnsson et al. (1987) have shown examples of verification of a model for a 2.13 m diameter industrial phthalic anhydride reactor. Several bubbling bed models gave good overall prediction of conversion and selectivity when proper reaction kinetics were used. The results were shown to be quite sensitive to the bubble diameter. The comparison was a good check of the models for the reaction kinetics, but the reactor model required accurate bubble size estimates obtained from measurements of overall bed density in the reactor. 

Figure 4 Badger phthalic anhydride reactors. (From Miseralis et al., 1991.)...

The difficulties in the evaluation of the experiments depend strongly on the mathematical model which has to be chosen. The evaluation is certainly more complicated if the reactor must be described by a two-dimensional model because of steep radial temperature gradients as we have observed it in the phthalic anhydrid reactor. 

The reaction uses a fixed-bed vanadium pentoxide-titanium dioxide catalyst which gives good selectivity for phthalic anhydride, providing temperature is controlled within relatively narrow limits. The reaction is carried out in the vapor phase with reactor temperatures typically in the range 380 to 400°C. 

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. 

Toluene hydrodealkylation to benzene and methane Phthalic anhydride by air oxidation of naphthalene Trickle bed reactor for hydrodesulfurizatiou... 

Gasoline accumulator Solvents Storage vessels Lube oil refining Polyethylene gas vents Styrene Copper naphthenates Insecticides Phthalic anhydride Resin reactors Ammonia Chlorine solutions Dry cleaning Degreasers Tar dipping Kraft paper... 

Subject to resolution of these concerns, scaling in parallel has no obvious limit. Multitubular reactors with 10,000 tubes have been built, e.g., for phthalic anhydride oxidation. 

An alternative route to phthalic anhydride is the partial oxidation of naphthalene. The heat of reaction is — 430 kcal/mol. This reaction can be performed using a promoted V2O5 catalyst on silica, much like that considered in Example 9.1. Suppose In(fik) = 31.6800—19,100/T for the naphthalene oxidation reaction and that the subsequent, complete oxidation of phthalic anhydride follows the kinetics of Problem 9.3. Suppose it is desired to use the same reactor as in Example 9.1 but with a,>, = 53g/ m. Determine values for and T aii that maximize the output of phthalic anhydride from naphthalene. 

The reaction between mono-octyl phthalate and i5tMx tanol (see Fig. 5.4-25) in the presence of a homogeneous catalyst (rert-butyl titanate) was studied in a batch reactor (Szarawara et al., 1991). This is the second step of the reaction between phthalic anhydride and o-octanol. First the ring is opened and mono-octyl phthalate is formed. Water is removed by evaporation as it is formed. The reaction was carried out at 174 °C. The initial concentration of mono-octyl phthalate was cpno = 1.85 mol/L and the ratio of initial concentrations of iio-octanol to mono-ooctyl phthalate coc.o/cph,o = 1.4. The reaction was... 

Ortho-xylene (A) is oxidised to phthalic anhydride (B) in an ideal, continuous flow tubular reactor. The reaction proceeds via the complex consecutive parallel reaction sequence, shown below. The aim of the reaction is to produce the maximum yield of phthalic anhydride and the minimum production of waste gaseous products (C), which are CO2 and CO. 

Figure 5.76. The fixed-bed reactor and the reaction scheme. Symbols A = o-xylene, B phthalic anhydride, C = waste gaseous products (CO2 and CO).

NON-ISOTHERMAL FIXED BED REACTOR OXIDATION OF 0-XYLENE TO PHTHALIC ANHYDRIDE STEADY-STATE AXIAL TEMPERATURE AND CONVERSION CONSTANT 6=4684 superf. mass velocity [kg/m2 h]... 

Fluidized bed reactors were first employed on a large scale for the catalytic cracking of petroleum fractions, but in recent years they have been employed for an increasingly large variety of reactions, both catalytic and non-catalytic. The catalytic reactions include the partial oxidation of naphthalene to phthalic anhydride and the formation of acrylonitrile from propylene, ammonia, and air. The noncatalytic applications include the roasting of ores and Tie fluorination of uranium oxide. 

This chapter contains a discussion of two intermediate level problems in chemical reactor design that indicate how the principles developed in previous chapters are applied in making preliminary design calculations for industrial scale units. The problems considered are the thermal cracking of propane in a tubular reactor and the production of phthalic anhydride in a fixed bed catalytic reactor. Space limitations preclude detailed case studies of these problems. In such studies one would systematically vary all relevant process parameters to arrive at an optimum reactor design. However, sufficient detail is provided within the illustrative problems to indicate the basic principles involved and to make it easy to extend the analysis to studies of other process variables. The conditions employed in these problems are not necessarily those used in current industrial practice, since the data are based on literature values that date back some years. 

PHTHALIC ANHYDRIDE PRODUCTION VIA THE CATALYTIC OXIDATION OF NAPHTHALENE IN A FIXED BED REACTOR... 

Re Design Specifications for Phthalic Anhydride Production in a Fixed Bed Reactor A proposed expansion of the corporation s vinyl plastics operation will require a commitment by the company to produce its own plasticizer. Our long range planning group has suggested that 6 million pounds per year of new phthalic anhydride capacity would meet our internal needs and projected increases in demand from current customers. 

However, in order to design a reactor for phthalic anhydride production, the reaction rate constants for the temperature range of interest are such that the following simplified set of reactions has been suggested as appropriate (6, 7). 

The reactions are highly exothermic and very rapid. Consequently conventional practice in the design of fixed bed reactors for phthalic anhydride production has been based on the use of multitube reactors to ensure good heat transfer and good temperature control. These are required to ensure good selectivity. Often a thousand or more small diameter tubes may be... 

Phthalic Anhydride Production Via the Catalytic Oxidation of Naphthalene in a Fixed Bed Reactor... 

Your assignment is to use the data and assumptions listed below to prepare a preliminary reactor design in which particular emphasis is placed on the variation of the maximum yield of phthalic anhydride with feed temperature. 

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