Periodic operation of catalytic reactors - introduction and overview

A review, with 89 refs., is presented on the subject of periodic operation of catalytic reactors by compn. forcing. Possible objectives of this mode of reactor operation are increased conversion, improved selectivity, reduced catalyst deactivation and insight into mechanisms of reactor models. Several forcing strategies may be used: manipulating one or more reactant concns., or interspersing pulses of inerts between pulses of reactants. These strategies are distinct from the variables in periodic operation, i.e., frequency, wave shape, amplitude, and phase lag. Lab.-scale equipment for periodic forcing makes use of single reactors along with the control of reactant and/or diluent flows. On an industrial scale, two catalyst beds are used, each operating with different feeds under different conditions. Catalyst transfers between the beds. A large literature has developed over the 25 yr since periodic operation was first proposed. [on SciFinder (R)

Periodic operation of catalytic reactors—introduction and overview

Fraternity homecoming displa

Scaling Parameters for Dynamic Diffusion-Reaction over Porous Catalysts

The effect of diffusion resistance in porous solid catalysts on reaction rate during periodic cycling of CO concentration is shown for CO oxidation over Pt/Al2O3 by numerical simulation. At some cycling frequencies, the average reaction rate during cycling is higher than the steady-state rate at the mean CO concentration, as expected for this nonlinear, reactant-inhibited reaction. In order to identify major aspects of dynamic diffusion-reaction behavior, a simple kinetic mechanism that shows the main features of CO oxidation and other reactions with significant inhibition by reactants is investigated. A single dimensionless parameter group, the dynamic diffusion coefficient, is added when going from steady-state to unsteady-state diffusion-reaction equations. In the dynamic diffusion coefficient, the rate at which the gas-phase reactant diffuses is reduced by the surface adsorption capacity of the catalyst. The frequency at which the peak average rate occurs is controlled by the dynamic diffusion coefficient

A novel carbon-based process for flue gas cleanup

The objective of this project is to demonstrate the preliminary technical and economic feasibility of a novel carbon-based process for removal of at least 95% SO{sub 2} and at least 75% NO{sub x} from coal combustion flue gas. In the process, flue gas leaving the electrostatic precipitator (ESP) is passed through a trickle bed of activated carbon catalyst employing a periodic flush of low strength sulfuric acid. The SO{sub 2} is oxidized to SO{sub 3} and removed as medium strength sulfuric acid. The SO{sub 2}-free flue gas is then mixed with NH{sub 3}, and the NO{sub x} in the gas is subjected to selective catalytic reduction (SCR) to N{sub 2} over a fixed-bed of activated carbon catalyst

A novel carbon-based process for flue gas cleanup

The objective of this project is to demonstrate the preliminary technical and economic feasibility of a novel carbon-based process for removal of at least 95% S0[sub 2] and at least 75 % NO[sub x], from coal combustion flue gas. In the process, flue gas leaving the electrostatic precipitator (ESP) is passed through a trickle bed of activated carbon catalyst employing a periodic flush of low strength sulfuric acid. The S0[sub 2] is oxidized to S0[sub 3] and removed as medium strength sulfuric acid. The S0[sub 2]-free flue gas is then mixed with NH[sub 3], and the NO[sub x] in the gas is subjected to selective catalytic reduction (SCR) to N[sub 2] over a fixed bed of activated carbon catalyst. In the previous four quarters, a detailed project management plan was prepared describing the experimental setup, work plan, and test plan. The experimental system was completed for SO[sub 2] conversion at Waterloo and for NO[sub x] conversion at Research Triangle Institute. Shakedown experiments were completed. The NO[sub x] removal performance of two additional modified carbon catalysts (MCCII and MCCIII) was studied. MCCII showed NO[sub 2] removal efficiency which was similar to that observed for MCCI. However, MCCIII was considerably less active for NO[sub x] removal. In the present quarter, further tests of MCCI were performed for SO[sub 2] removal with NO in the feed gas, except the reactor was operated at 130[degrees]C (instead of 80[degrees]C during previous tests). Tests were also performed with MCCII for NO removal with nominally 100 ppm SO[sub 2] in the feed gas

A novel carbon-based process for flue gas cleanup. Third quarterly technical progress report, January 1--March 31, 1992

The objective of this project is to demonstrate the preliminary technical and economic feasibility of a novel carbon-based process for removal of at least 95% SO{sub 2} and at least 75% NO{sub x} coal combustion flue gas. In the process, flue gas leaving the electrostatic precipitator (ESP) is passed through a trickle bed of achieved carbon catalyst employing a periodic flush of low strength sulfuric acid. The SO{sub 2} is oxidized to SO{sub 3} and removed as medium strength sulfuric acid. The SO{sub 2}-free flue gas is then mixed with NH{sub 3}, and the NO{sub x} in the gas is subjected to selective catalytic reduction (SCR) to N{sub 2} over a fixed bed of activated carbon catalyst. The experimental work is divided between Research Triangle Institute (RTI) and the University of Waterloo (Waterloo). RTI will conduct the NO{sub x} removal studies, whereas Waterloo will conduct the SO{sub 2} removal studies. The ultimate goal of the project is to demonstrate that the process can be reduce the cost of electricity by 20% over conventional SCR/flue gas desulfurization (FGD) processes. In the present quarter, the continuous SO{sub 2} analyzer system at Waterloo was completed. The SO{sub 2} removal factorial experiments were begun Waterloo with the BPL carbon at 21{degrees}C. Also, SO{sub 2} removal was tested on two catalyst at RTI at 80{degrees}C. NO{sub x} conversion was tested on a variety of catalysts at RTI. It was shown that the BPL carbon could remove over 95% SO{sub 2} at 21{degrees}C but would required several beds at space velocity in each bed of abut 1,500 scc/(cc{center_dot}h) to reduce SO{sub 2} from 2,500 ppm to 100 ppm. A modified carbon catalyst tested at RTI showed 99% SO{sub 2} removal at 80{degrees}C at 1,400 scc/(cc{center_dot}h). Also, it was possible to produce nearly 9 normal H{sub 2}SO{sub 4} by periodic flushing of this catalyst. The modified carbon catalyst also demonstrated removal of more than 80% NO{sub x}. 7 refs., 7 figs., 4 tabs

A novel carbon-based process for flue gas cleanup

The objective of this project is to demonstrate the preliminary technical and economic feasibility of a novel carbon-based process for removal of at least 95 % SO[sub 2], and at least 75 % NO[sub x] from coal combustion flue gas. In the process, flue gas leaving the electrostatic precipitator (ESP) is passed through a trickle bed of activated carbon catalyst employing a periodic flush of low strength sulfuric acid. The SO[sub 2] is oxidized to SO[sub 3] and removed as medium strength sulfuric acid. The SO[sub 2]-free flue gas is then mixed with NH[sub 3], and the NO[sub x] in the gas is subjected to selective catalytic reduction (SCR) to N[sub 2] over a fixed bed of activated carbon catalyst. In the previous six quarters, detailed project plans were prepared and experimental systems were commissioned. The SO[sub 2] removal factorial experiments with BPL carbon at 21[degrees]C are well underway at Waterloo. A modified carbon catalyst (MCCI) showed up to 99% SO[sub 2] removal in the presence of NO[sub x] over 10 multiple cycles at 80--130[degrees]C and 1400 scc/cc/h. Several catalysts were evaluated for NO[sub x] removal also. Promising modified carbon catalysts (MCCI, II and III) were tested. Some of these catalysts showed the potentialfor over 80% NO[sub x] removal at space velocities as high as 3000 scc/cc/h. Poisoning of NO[sub x] removal efficiency with SO[sub 2] in the feed was also studied. With over 100 ppm SO[sub 2] in feed, NO[sub x]removal efficiency remained steady for several hours. It declined from 79% removal to 66% removal over 24 hours. NO[sub x] removal experiments were performed with 5 different materials and the SO[sub 2] removalactivity of 2 catalysts was tested