Hydrogenation reactor conditions

The reactor operates at a temperature 270 °C and a pressure of 2.5 bara. The reactor diameter is 10 m. Hydrogen is used in large excess in the reaction, and for the purposes of this exercise the properties of the gas may be taken as those of hydrogen at the reactor conditions. The density of the catalyst particles is 1800 kg/m3. 

The first reaction produces methanol with a low hydrogen consumption, but evolves significantly greater amounts of heat. The second reaction evolves less heat, but consumes more hydrogen and produces the byproduct steam. Thermodynamically, low temperatures and high pressures favor methanol formation. The reactions are carried out with copper-containing catalysts with typical reactor conditions of 260°C and 5 MPa (Probstein and Hicks, 1982). 

In Figure 2-7, toluene is fed into a heated reactor containing the catalyst in a fixed bed. A small amount of hydrogen is pumped in to keep carbon deposition on the catalyst to a minumum. The reactor conditions are in the 650—950°C and 150—500 psi ranges. The effluent is cooled then the hydrogen is recovered and recycled The rest of the effluent is then triple... 

A severely weathered bituminous coal from eastern Canada was treated by thermal hydrogenation under various reactor conditions. The coking properties of this coal were found to be restored under appropriate hydrogenation conditions. The semi-coke of the hydrogenated coal exhibited an anisotropic coke structure. The size of the anisotropic domains in the semi-coke was found to depend on reactor temperature and hydrogen pressure during hydrogenation. 

Another coke formed in a FCC unit is occluded or residual coke. In a commercial unit this coke corresponds to coke formed on catalyst porosity and its content depends on textural properties of the catalyst (pore volume and pore size distribution) and the stripping system capacity in the reaction section. Finally on the FCC catalyst rests some high-molecular weight of nonvaporized hydrocarbons. These molecules do not vaporize or react at the reactor conditions and accumulate in the catalyst pores like a soft carbonaceous residue with high hydrogen content. 

A reactor was charged with 1000 ml hexane and a specified amount of the step 5 catalyst and triethylaluminum so that the Al/Ti ratio was at 200. The reaction temperature was raised to 75 °C and a sufficient amount of hydrogen gas necessary to provide a molar ratio of hydrogen/ethylene of 0.2/0.8 for the low-hydrogen level condition and 0.7/0.3 for the high-hydrogen level added so that a total pressure of... 

Of the technological modifications, Fischer-Tropsch synthesis in the liquid phase (slurry process) may be used to produce either gasoline or light alkenes under appropriate conditions249,251 in a very efficient and economical way.267 The slurry reactor conditions appear to establish appropriate redox (reduction-oxidation) conditions throughout the catalyst sample. The favorable surface composition of the catalyst (oxide and carbide phases) suppresses secondary transformations (alkene hydrogenation, isomerization), thus ensuring selective a-olefin formation.268... 

Concerning activity, most studies focus on intrinsic (chemical) kinetics, with little consideration to the apparatus and its possible physical limitations. In fact,the design and selection of a catalytic hydrogenation reactor (hydrogenator) is not a trivial problem at all, owing to the broad range of process conditions encountered. 

The size of the bubbles produced in the reactor and the gas volume fraction will depend on the agitation conditions, and the rate at which fresh hydrogen is fed to the impeller, as shown in Fig. 4.20. (Some hydrogenation reactors use gas-inducing impellers to recirculate gas from the head-space above the liquid while others use an external compressor.) For the purposes of the present example, the typical values, db = 0.8 mm and eg m 0.20, will be taken. Also dependent to some extent on the agitation conditions are the values of the transfer coefficients kL and k, although these will depend mainly on the physical properties of the system such as the viscosity of the liquid and the diffusivity of the dissolved gas. The values taken here will be kL = 1.23 x 10 5 m/s and k, = 0.54x 10"3 m/s. 

Method of Operation. The catalyst was activated in the reactor by first calcining at 232.2 C (450 F) and then sulfiding with a mixture of 5.14 volume percent H2S in H2. The reactor was then brought to the operating conditions and the flow of hydrogen and oil started. After about 32 hours of operation for catalyst stabilization, representative product oil samples were taken at specified reactor conditions. The product oil samples were analyzed for sulfur and nitrogen contents with the help of a Leco Model 634-700 automatic sulfur analyzer and Perkin Elmer Model 240 elemental analyzer, respectively. 

HYDROGEN TRANSFER INDEX (HTI1 TEST In this test, 0.5 /xL pulses of 1-hexene feed were carried from a heated sampling valve into a fixed-catalyst bed in a stainless steel reactor by a nitrogen carrier stream at 800 mL/min. (at STP). The catalyst was -250 mesh and diluted with alumina of the same mesh size plus 80-100 mesh acid-washed Alundum. Reactor pressure was controlled by an Annin valve. The effluent stream went to the injector splitter of a gas chromatograph. The reactor conditions included a catalyst temperature of 221°C and 3.45 MPa total pressure. 

In adiabatically operated industrial hydrogenation reactors temperature hot spots have been observed under steady-state conditions. They are attributed to the formation of areas with different fluid residence time due to obstructions in the packed bed. It is shown that in addition to these steady-state effects dynamic instabilities may arise which lead to the temporary formation of excess temperatures well above the steady-state limit if a sudden local reduction of the flow rate occurs. An example of such a runaway in an industrial hydrogenation reactor is presented together with model calculations which reveal details of the onset and course of the reaction runaway. 

The CO-hydrogenation reaction, or Fischer-Tropsch (F-T) synthesis reaction, has been thoroughly investigated since its discovery fn the 1920 s [1]. A range of catalysts has been shown to be active for hydrocarbon synthesis and iron [2] and cobalt [3] have found commercial applications in this field. A variety of reactors have been developed to optimize the synthesis reaction [4]. Variations of reactor conditions have been shown to maximize specific products from the broad range of products produced in the reaction [5). 

The gas (mainly hydrogen) flow rate can be taken as 0.75 m3 h 1 at the operating conditions and the slurry flow rate is 100 lbm h l. Assume all other reactor conditions to be the same as those used in the previous illustration. For part (c) take the molecular diffusivity in the liquid phase to be I0-3 cm2 s-1. 

Figure 2 (a) Deactivation of Pt/silica (D) in isothermal cyclohexene hydrogenation under conditions mentioned in the text in the reactor shown in (b). (c) Ruidised bed reactor in which entered at 1 and passed by 1.7%Pt/alumina pellets and fluidised 3g silica-alumina powder thereon (which also received QHiq/Nj entering at a low rate at 2) in which the activity of the silica-alumina shown in (d) was recorded at 323K. These data were measured in the absence (O ) and the presence ( C first run 9 second run) of the Pt/alumina pellets, and after the removal of these pellets ( ). The dependence of the activity (d) of this silica-alumina on the weight of pellets used in retesting is shown in (e)... 

The reaction between hydrogen atoms and hydrazine in a flow system has been investigated by Schiavello and Volpi . Hydrogen atoms produced in a micro-wave discharge were flowed into a vessel along with N2H4, under stirred reactor conditions. Under steady-state conditions the reactor vessel was sampled through a pin hole leak (25 /rm diameter) which led directly to a mass spectrometer ion source. 

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