Catalyst reactor conditions

Figure 19. Battelle s methanol specific reforming catalyst. Reactor conditions atmospheric pressure, reactant feed 50 50 by weight methanol and water mixture, 24 000— 50 000 ii GHSV. The conversion was reported as moles methanol reacted/moles methanol fed. (Reprinted with permission from ref 91. Copyright 2002 Elsevier.)...

Only the surface layers of the catalyst soHd ate generaHy thought to participate in the reaction (125,133). This implies that while the bulk of the catalyst may have an oxidation state of 4+ under reactor conditions, the oxidation state of the surface vanadium may be very different. It has been postulated that both V" " and V " oxidation states exist on the surface of the catalyst, the latter arising from oxygen chemisorption (133). Phosphoms enrichment is also observed at the surface of the catalyst (125,126). The exact role of this excess surface phosphoms is not weH understood, but it may play a role in active site isolation and consequently, the oxidation state of the surface vanadium. 

Shell Higher Olefins Process (SHOP). In the Shell ethylene oligomerization process (7), a nickel ligand catalyst is dissolved in a solvent such as 1,4-butanediol (Eig. 4). Ethylene is oligomerized on the catalyst to form a-olefins. Because a-olefins have low solubiUty in the solvent, they form a second Hquid phase. Once formed, olefins can have Htfle further reaction because most of them are no longer in contact with the catalyst. Three continuously stirred reactors operate at ca 120°C and ca 14 MPa (140 atm). Reactor conditions and catalyst addition rates allow Shell to vary the carbon distribution. 

Catalyst Effectiveness. Even at steady-state, isothermal conditions, consideration must be given to the possible loss in catalyst activity resulting from gradients. The loss is usually calculated based on the effectiveness factor, which is the diffusion-limited reaction rate within catalyst pores divided by the reaction rate at catalyst surface conditions (50). The effectiveness factor E, in turn, is related to the Thiele modulus,

first-order rate constant, a the internal surface area, and the effective diffusivity. It is desirable for E to be as close as possible to its maximum value of unity. Various formulas have been developed for E, which are particularly usehil for analyzing reactors that are potentially subject to thermal instabilities, such as hot spots and temperature mnaways (1,48,51). 

The U.S. Department of Energy has funded a research program to develop the Hquid-phase methanol process (LPMEOH) (33). This process utilizes a catalyst such as copper—zinc oxide suspended in a hydrocarbon oil. The Hquid phase is used as a heat-transfer medium and allows the reaction to be conducted at higher conversions than conventional reactor designs. In addition, the use of the LPMEOH process allows the use of a coal-derived, CO-rich synthesis gas. Typical reactor conditions for this process are 3.5—6.3 MPa (35—60 atm) and 473—563 K (see Methanol). 

Under polymerisation conditions, the active center of the transition-metal haHde is reduced to a lower valence state, ultimately to which is unable to polymerise monomers other than ethylene. The ratio /V +, in particular, under reactor conditions is the determining factor for catalyst activity to produce EPM and EPDM species. This ratio /V + can be upgraded by adding to the reaction mixture a promoter, which causes oxidation of to Examples of promoters in the eadier Hterature were carbon tetrachloride, hexachlorocyclopentadiene, trichloroacetic ester, and hensotrichloride (8). Later, butyl perchlorocrotonate and other proprietary compounds were introduced (9,10). 

General. The flame-sprayed Raney nickel catalyst was used in exexperiments HGR-10, HGR-12, and HGR-14, the pelleted precipitated catalyst in experiment HGR-13. Reactor conditions as a function of... 

Experiment HGR-14. The reactor was packed with 2 ft of parallel plates sprayed with Raney nickel (Table I) catalyst spraying and activation were as described under catalyst preparation. Operating conditions were practically the same as in experiment HGR-13 except for the periodic changes in the CGR ratio (see Figure 8 for reactor conditions and Figure 9 for product gas characteristics). 

Table II summarizes the yields obtained from the CONGAS computer output variable study of the gas phase polymerization of propylene. The reactor is assumed to be a perfect backmix type. The base case for this comparison corresponds to the most active BASF TiC 3 operated at almost the same conditions used by Wisseroth, 80 C and 400 psig. Agitation speed is assumed to have no effect on yield provided there is sufficient mixing. The variable study is divided into two parts for discussion catalyst parameters and reactor conditions. The catalyst is characterized by kg , X, and d7. Percent solubles is not considered because there is presently so little kinetic data to describe this. The reactor conditions chosen for study are those that have some significant effect on the kinetics temperature, pressure, and gas composition.

The surface transformations of propylene, allyl alcohol and acrylic acid in the presence or absence of NHs over V-antimonate catalysts were studied by IR spectroscopy. The results show the existence of various possible pathways of surface transformation in the mechanism of propane ammoxidation, depending on the reaction condition and the surface coverage with chemisorbed NH3. A surface reaction network is proposed and used to explain the catalytic behavior observed in flow 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 performance of most catalysts deteriorates with time3-5. The rate at which the deterioration takes place is not only an important factor in the choice of catalyst and reactor conditions but also the reactor configuration. 

We evaluated a number of potential catalysts and conditions using xylitol as a model compound in a batch reactor. A catalyst was selected from this initial screening and examined in a continuous trickle-bed reactor to develop operating conditions. Finally, as resources allowed, the catalyst was evaluated in a trickle bed reactor to gain a concept of potential catalyst lifetime. 

Commercially available processes for resid HCK deal with catalyst life cycle issues by the use of different catalyst/reactor/configuration arrangements. In Ref. [142], Morel et al. discuss the performance and features of these arrangements. A summary of conditions for each reaction system is collected in Table 11. 

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). 

Graver, V., Zhan, X., Engman, J., Robota, H. J., Suib, S. L., and Polverejan, M. 2004. Deactivation of a Fischer-Tropsch catalyst through the formation of cobalt carbide under laboratory slurry reactor conditions. Prepr. Pap.-Am. Chem. Soc. Div. Pet. Chem. 49 192-94. 

In this work we attempt to measure kinetics data in a time short compared with the response time of the catalyst stoichiometry. An alternative is to measure kinetics in a true steady state, i.e., to increase the line-out time at each reactor condition until hysteresis is eliminated. The resulting apparent reaction orders and activation energies would be appropriate for an industrial mathematical model of reactor behavior. 

There is a need for low-cost methane steam reforming catalysts that are active at low temperature and resistant to coke formation under membrane reactor conditions. Low-cost (Ni-based) catalysts are also needed that can withstand regeneration conditions in a sorption-enhanced reformer. 

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... 

The dimerization (Aldol condensation) takes place at temperatures of 175—250°F in the presence of a dilute solution of sodium hydroxide. After the reaction, the mixture is passed to a separator tank where the dimer is separated then sent to a reactor to be hydrogenated over a nickel catalyst. Reaction conditions have temperatures of 300°F and 2500 psi. Distillation of the effluent gives purified 2-EH in 95% yield. 

---