Low-temperature Shift Catalyst Research Articles

Low-temperature shift DeNOx activity of Nanoflake V2O5 loaded WO3/TiO2 as NH3-SCR catalyst

Nanoflake V 2 O 5 loaded onto WO 3 /TiO 2 improves the low-temperature shift NH 3 -SCR catalytic activity. The low temperature shift phenomenon was obtained and dramatically shifted from 305 to 221 °C at GHSV 20000/h. • Crystalline Nanoflake (NF) V 2 O 5 loaded onto WO 3 /TiO 2 (NF V 2 O 5 -W/T) a low temperature-shift NH 3 -SCR catalyst has been prepared successfully. • NF V 2 O 5 -W/T showed 100 % NH 3 -SCR conversion efficiency at GHSV 20000/h was obtained and dramatically shifted from 305 to 221 °C according to the increase of NF V 2 O 5 loading contents (0.5 ∼ 3 wt%). • The low temperature shift phenomenon is due to the crystallinity, particle shape, size and oxidation state of (NF) V 2 O 5 loaded on W/T catalyst, compared with monodispersed and polymeric species of Im V 2 O 5 . Nanoflake V 2 O 5 supported on WO 3 /TiO 2 (NF V 2 O 5 -W/T) as a low temperature shift catalyst for selective catalytic reduction (SCR) of NO with NH 3 was prepared. The catalyst was compared with NH 4 VO 3 solution impregnated WO 3 /TiO 2 (Im V 2 O 5 -W/T) as a commercial catalyst. Dispersed 50 ∼ 200 nm NF V 2 O 5 slurry was bead-milled and exfoliated in ethanol along with the aggregated flake V 2 O 5 particles having 0.05 ∼ 1 µm crystal size. NF V 2 O 5 -W/T catalyst was designed and prepared with varying the loading amount of the dispersed NF V 2 O 5 slurry. To observe the low-temperature shift phenomenon of NF V 2 O 5 -W/T catalyst at GHSV 20000/h, a 100 % DeNOx conversion efficiency was obtained and dramatically shifted from 305 to 221 °C according to the increase of NF V 2 O 5 loading contents (0.5 ∼ 3 wt%), compare with Im V 2 O 5 -W/T. The DeNOx efficiency, along with temperature shift phenomenon of these catalysts was elucidated by the loading content, crystallinity and the V 4+ /V 5+ oxidation state ratio of V 2 O 5 loaded on W/T catalyst. It is thought that the crystalline species of NF V 2 O 5 loaded on W/T catalysts prepared in this work potentially meets their application to effectively decompose NOx at low temperature compared with monodispersed and polymeric species of Im V 2 O 5 .

Kinetics of facilitated transport of Zn(II) from leach liquor of spent LTS catalyst across bulk liquid membrane

A kinetic study on facilitated transport of Zn(II) from leach liquor of spent low-temperature shift catalyst (LTS) has been investigated. Primarily, the hydrometallurgical leaching of Zn and Cu from the spent LTS catalyst was performed. Moreover, the selective transport of Zn from leach liquor was facilitated by bis (2-ethylhexyl) phosphate (HDEHP) across bulk liquid membrane. The aqueous phase pH plays an important role in the selective transport of Zn from feed to stripping phase. It was observed that more than 90% of Zn was extracted at an aqueous phase pH of 3. The kinetics of the transport was analyzed using a kinetic law of two consecutive irreversible first-order reactions. Kinetic parameters such as k1, k2, Rm, tm, and flux values were evaluated by fitting the experimental data. The order of the flux for the transport of Zn(II) in three diluents was observed as dichloromethane > chloroform > carbon tetrachloride.

A Greener Approach to Extract Copper from Fertilizer Industry Spent Catalyst

Large quantities of catalysts after their useful life are discarded as waste material from fertilizer industry. Disposal of spent catalyst is a problem as it falls under the category of hazardous industrial waste due to its heavy metals concentration. This investigation applied a novel approach to extract copper from spent low-temperature shift catalyst (CuO–ZnO–Al2O3) using chelation process. Ethylenediaminetetraacetic acid (EDTA) was used as the chelating agent. Optimum parameters to extract 95% copper were found as: EDTA concentration 0.5 M, reaction temperature 100 °C, solid-to-liquid ratio 1:25 (g/ml), particle size 120 µm and reaction time 4 h. A kinetic analysis of the experimental data was done by shrinking core model which revealed the rate-controlling step of the leaching process as product layer diffusion. The activation energy calculated was 10.58 kJ/mol which supports leaching process to be the product layer diffusion controlled. The process adopted is eco-friendly as the EDTA was recovered after the extraction of copper from the spent catalyst and reused again. The recycled EDTA obtained after the extraction was characterized by NMR and SEM. The activity of the recycled EDTA was found to be consistent with the fresh EDTA.

Kinetic study on leaching of Zn and Cu from spent low-temperature shift catalyst (CuO/ZnO/Al2O3): application of taguchi design

The recovery of valuable metals from the spent catalysts has become a part of exhaustive research not only due to reducing the inventory cost of catalysts but also for minimizing the spent catalyst generation to prevent environmental pollution. In the present investigation, the kinetic study of the hydrometallurgical based leaching of Zn and Cu from the spent low-temperature shift catalyst (CuO/ZnO/Al2O3) have been performed. Additionally, the process parameters affecting the leaching process have been optimized by Taguchi’s orthogonal array design. The results of the kinetic analysis indicated that the leaching process was mainly controlled by the diffusion through the porous product layer. The activation energy for the leaching of Zn and Cu were estimated as 18.63 kJ/mol and 18.14 kJ/mol respectively. Quantitative leaching of Zn (96.71%) and Cu (94.82%) was observed under the optimum levels such as HCl concentration − 3 M, leaching time − 3 h, stirring speed—600 rpm, S/L − 0.01, particle size − 90 µm and temperature – 80 C.

Optimization of copper extraction from spent LTS catalyst (CuO–ZnO–Al2O3) using chelating agent: Box-behnken experimental design methodology

The objective of the present work is to investigate the extraction of copper from spent low temperature Shift catalyst using EDTA, as chelating agent and optimization of the parameters that influence the extraction of copper. Response surface methodology was applied for designing the experiment and to determine the optimal experimental conditions. Most influencing parameters such as concentration of EDTA, solid to liquid ratio and particle size of catalyst were optimized based on 3 factors 3 levels box behnken design which requires 15 run of experiments for designing a response surface. The high value of regression coefficient R 2 (0.981) indicates a good correlation between predicted and experimental response, which confirms the acceptability of the proposed model.The optimum conditions were found as—concentration of EDTA: 0.5889 M, solid to liquid ratio: 0.02 and particle size: 90 μm. Under these optimum conditions, the experimental value of extraction of copper was estimated as 94.5% which seems very close to predicted response.

Water gas shift reaction in a catalytic bubbling fluidized bed reactor

The water gas shift reaction in a catalytic bubbling fluidized bed reactor was investigated by using simulated syngas (40% H2, 40% CO and 20% CO2) for the pre-combustion CO2 capture and hydrogen production application. A commercial low temperature shift (LTS) catalyst with particle sizes of 200-300 μm was used to investigate the promotion effect by exchanging the fixed bed reaction with the fluidized bed reactor. The effects of the reactor temperature (180-400 °C), space velocity (800-4,800 cm3/h·g), and steam/CO ratio (1.0-2.5) on the CO conversion and syngas composition were determined, and the highest CO conversion was 86.8% at 300 °C with the LTS catalyst at a space velocity of 800 cm3/h·g and steam/CO ratio of 2.5. The experiments exhibited an improvement in activity and a conversion reached that given by equilibrium at temperatures over 300 °C. Also, the performance was much improved than that when a fixed bed system was used.

Deposition of Macro Porous Low Temperature Shift Catalysts Over a Micro-Channel Plate and Their Catalytic Activity

Deposition of Macro Porous Low Temperature Shift Catalysts Over a Micro-Channel Plate and Their Catalytic Activity

RANEY COPPER CATALYSTS FOR THE WATER-GAS SHIFT REACTION: CATALYST OPTIMISATION USING STATISTICAL METHODS

Statistically designed experiments were used to optimise a Raney copper catalyst system for the water-gas shift reaction by assessing a large number of variables which contribute towards catalytic activity and stability. A 2III II-7 fractional factorial design was employed to screen eleven preparation and four reaction process variables, of which the CO:H2O ratio, alloy particle size, caustic/soluble metal ratio and zincate leach concentration were found to significantly influence the long term final catalyst activity and the overall change in activity. A composite factorial design together with response surface methodology was used to optimise the three preparation variables with respect to maximum final activity and minimum change in activity. The results of these experiments showed that the interaction between alloy particle size and caustic/soluble metal ratio was significantly responsible for final activity. Catalyst deactivation, as measured by change in activity, was significantly influenced by the interaction of zincate concentration and the caustic/soluble metal ratio. At an operating temperature of 200°C, the optimum Raney copper catalyst of composition 48.8 weight percent Cu, 15.9 weight percent Zn and 33.1 weight percent Al demonstrated a higher specific activity than an industrial low temperature shift catalyst over 960 hours-on-stream under the same conditions. The above example of catalyst optimisation thus provides an excellent example of the advantages associated with this approach to catalyst experimentation.

Sulfide removal from seawater with waste catalysts

A comparative study was made in order to estimate the feasibility of using waste catalysts for low level sulfide removal from seawater polluted with sulfide under aerated and deaerated conditions. Six different waste catalysts were used from a typical petrochemical plant. A batch recycle reactor with a large recycle ratio was utilized for this purpose. It is found that low temperature shift catalyst has a superior scavenging efficiency for sulfide removal with an estimated sulfide half life of about ten minutes. Generally all the catalysts performed better than the homogeneous reaction. The presence of oxygen, can influence the effectiveness of these catalysts in removing sulfide. The sulfide reaction kinetic was zero order with respect to sulfide concentration and the batch recycle reactor containing the waste catalysts with large recycle ratio was shown to approximate ideal stirred tank reactor.

Hydrogen production by the catalytic steam reforming of methanol: Part 3: Kinetics of methanol decomposition using C18HC catalyst

AbstractThe rate of catalytic decomposition of methanol in the presence of steam has been studied using a commercial CuO‐ZnO‐Al2O3. low temperature shift catalyst from 150‐270°C at one atmosphere pressure in a fixed bed reactor. Mole ratios of steam to methanol of 0.66. 1.0 and 1.5 and catalyst mass to molar feed rate ratios of 25 to 1025 kg. s. mol −1 were utilized. The data were correlated and equations developed to successfully predict methanol conversions and carbon monoxide concentrations in the product gas stream over the temperature range studied. No evidence of mass transfer limitations was observed.

Chemical reaction and phase transformations of the components of low temperature shift catalyst in various atmospheres

The systems CuO−Al2O3 and ZnO−Al2O3, as model systems of low temperature shift catalysts, have been studied in the temperature interval 100–700°C. The changes of their phase composition and surface area, influenced by gas atmosphere have been studied by X-ray, IR analysis and low temperature nitrogen adsorption.

Hydrogen production by the catalytic steam reforming of methanol: Part 2: Kinetics of methanol decomposition using girdler G66B catalyst

AbstractThe rate of catalytic decomposition of methanol in the presence of steam has been studied using a commercial Girdler G66B CuO‐ZnO low temperature shift catalyst from 150 to 250°C at atmospheric pressure. The mole ratio of steam to methanol was varied from 0 to 1.5, and the feed rates covered the range from 300 to 1400 kg s/mol. The data were successfully correlated using a simple reaction network involving CH3OH, H2O, CO and H2. A conventional reversible reaction rate equation was used which included a resistance term for site blockage by a CO surface complex. The methanol decomposition rate constants showed satisfactory Arrhenius behaviour with an activation energy of about 96 kJ/mole.

Catalysis by a ruthenium complex heterogenized in faujasite-type zeolites: the water gas-shift reaction

The Ru(NH3)63+ complex, exchanged as such in faujasite-type zeolites, can be converted into another kind of complex of the form [Ru(NH3)x(OH)y(CO)z]n+ with n < 3; this complex has no homogeneous equivalent, it is stable up to 280 °C, is a very active catalyst for the water gas-shift reaction, and it exceeds the activity of a commercial copper based low-temperature shift catalyst.

Influences of Catalyst Formulation and Poisoning on the Activity and Die-Off of Low Temperature Shift Catalysts

Influences of Catalyst Formulation and Poisoning on the Activity and Die-Off of Low Temperature Shift Catalysts