Kinetic Study on the Effect of Chromium Addition to Ni-Based Catalysts for the Steam-CO2 Reforming of Methane.

In the present work, the kinetic effects of Ni-based catalysts containing various amounts of Cr on the steam-CO2 reforming (SCR) of methane were studied. Kinetic expressions for the SCR of methane over the Ni-based catalysts have been proposed using the power-law rate expression, based on the kinetic data obtained. In addition, the Arrhenius equation was used for calculating the activation energy. Analysis of the data revealed four simple results. Firstly, the partial pressure of CH4 exerts a major influence on the CH4 conversion rates. Secondly, the CH4 conversion rate is inversely proportional to the partial pressure of CO2. Thirdly, the partial pressure of steam has a very slight effect on the reaction rates. Finally, all the catalysts studied have similar apparent activation energies.

Carbon Deposition Onto Ni-Based Catalysts for Combined Steam/CO2 Reforming of Methane.

The present study was performed to suppress carbon deposition by Ce and Fe onto Ni-based catalysts in combined steam/CO2 reforming of methane (CSCRM), which is a process for producing synthesis gas (H2:CO = 2:1) for gas-to-liquids (GTL). The catalytic reaction was evaluated at 900 degrees C and 20 bar with a reactant feed ratio CH4:CO2:H20:Ar = 1:0.8:1.3:1 and gas hourly space velocity GHSV = 25,000 h(-1). The Ce and Fe modified Ni/gamma-A120, catalyst was characterized by BET surface area analysis, X-ray diffraction (XRD), H2 temperature-programmed reduction (TPR), H2 chemisorption, CO2 temperature-programmed desorption (TPD) and SEM. Ce- and Fe-modified Ni/Al2O3 catalysts exhibited remarkable activity and stability during the CSCRM over the course of 50 hours. It suggested that the Ni(12)-Ce(5)-Fe(5)/Al2O3 catalyst shows highly dispersed Ni particles with strong metal-to-support interaction (SMSI) as well as excellent catalytic activity.

Glycerol Steam Reforming Over Ni-Fe-Ce/Al2O3 Catalyst: Effect of Cerium.

In this work, hydrogen production from glycerol by steam reforming was studied using Ni-metal oxide catalysts. Ni-based catalyst becomes deactivated during steam reforming reactions because of coke deposits and sintering. Therefore, the aim of this study was to reduce carbon deposits and sintering on the catalyst surface by adding a promoter. Ni-metal oxide catalysts supported on Al2O3 were prepared via impregnation method, and the calcined catalyst was reduced under H2 flow for 2 h prior to the reaction. The characteristics of the catalysts were examined by XRD, TPR, TGA, and SEM. The Ni-Fe-Ce/Al2O3 catalyst, which contained less than 2 wt% Ce, showed the highest hydrogen selectivity and glycerol conversion. Further analysis of the catalysts revealed that the Ni-Fe-Ce/Al2O3 catalyst required a lower reduction temperature and produced minimum carbon deposit.

Kinetics for Steam and CO2 Reforming of Methane Over Ni/La/Al2O3 Catalyst.

Kinetic studies of mixed (steam and dry) reforming of methane on Ni/La/Al2O3 and Ni/La-Co (1, 3 wt%)/Al2O3 catalysts were performed in an atmospheric fixed-bed reactor. Kinetic parameters for the mixed reforming over these catalysts were obtained under reaction conditions free from heat and mass transfer limitations. Variables for the mixed reforming were the reaction temperature and partial pressure of reactants. The fitting of the experimental data for the rate of methane conversion, rCH4, using the power law rate equation rCH4 = k(PrCH4)α(PCO2)ß(PH2O)γ showed that the reaction orders α, ß, and γ are steady and obtained values equal to α = 1, ß = 0, and γ = 0. In other words, among CH4, CO2, H2O, and H2, only CH4 reaction orders were not zero and they were affected by the promoters. The apparent activation energy on catalysts Ni/La/Al2O3, Ni/La-Co (1)/Al2O3 and Ni/La-Co (3)/Al2O3 is 85.2, 93.8, and 99.4 kJ/mol, respectively. The addition of Co to Ni/La/Al2O3 was increased the apparent activation energy of the mixed reforming reaction. And the Ni/La-Co (3 wt%)/Al2O3 catalyst showed the highest reforming activity and apparent activation energy. The Co promoters can increase the apparent activation energy of mixed reforming of methane.

Effect of Bimetallic Ni-Cr Catalysts for Steam-CO2 Reforming of Methane at High Pressure.

The present work was to carry out the development of high performance Ni-based catalyst for Steam-CO2 reforming of methane (SCR) which is suitable for Fischer-Tropsch synthesis of GTL- FPSO (floating, production, storage and offloading) process. The bimetallic Ni-Cr catalysts were prepared by co-impregnation method. The Ni and Cr loading amount were fixed at 12 wt% and 3~7 wt%, respectively. The catalytic reaction was conducted at 900 °C and 20 bar with reactant feed ratio of CH4:CO2:H2O:Ar = 1:0.8:1.3:1 and GHSV = 25,000 h(-1). The Cr-modified Ni/γ-Al2O3 catalyst was characterized by BET surface area analysis, X-ray diffraction (XRD), H2-temperature programmed reduction (TPR), H2-chmisorption, CO2-temperature programmed desorption (TPD) and Transmission electron microscopy(TEM). To confirm the amount and type of the carbon deposition, the used catalysts were examined by Thermogravitic analysis (TGA) and Field emission-scanning microscopy/Energy dispersive X-ray analysis (FE-SEM/EDX). It was found that the bimetallic Ni-Cr catalyst exhibits highly dispersed Ni particles with strong metal-to-support interaction (SMSI) as well as excellent catalytic activity, resulting in the suppression of Ni sintering and carbon deposition.

Carbon Deposition from the CO2-Steam Reforming of Methane Over Modified Ni/γ-Al2O3 Catalysts.

The aim of this work is to study the catalytic activity and suppression of carbon deposition in the CO2-Steam reforming of methane (SCR) to develop a high performance catalyst for GTL-FPSO application which is required to high pressure (20 bar) for F-T synthesis. Ni/La-X(6)/Al2O3 (X = Ce, Mg, Zr) catalysts were prepared by the impregnation method. The catalytic reaction was studied in a fixed bed reactor system at high pressure. X-ray diffraction (XRD), BET specific surface area and H2-temperature programmed reduction (TPR) were used to observe the characteristics of the prepared catalysts. The carbon deposition and the carbon amount in the used catalysts were examined by SEM and TGA, respectively. As a result, it was found that the Ni/La-Mg(6)/Al2O3 catalyst showed the highest activity and high carbon resistance. The highest activity in Ni/La-Mg(6)/Al2O3 was attributed to the proper Mg loading. It also had the lowest Ni particle and formed relatively stable MgAl2O4, which have an effect on the catalytic activity.

The Influence of Promoter on Ni(15)/La(5)/γ-Al2O3 Catalyst in CO2-Steam Reforming of Methane to Syngas at High Pressure.

Catalysts were investigated with respect to catalytic activity and coke formation in combined steam and carbon dioxide reforming of methane to develop a highly active and stable catalyst for gas to liquid processes. Ni/La-X/Al2O3 (X = Co, Ce, Mo) catalysts were prepared by an impregnation method. The combined steam and carbon dioxide reforming of methane reaction were studied as a function of high pressure (20 bar) in a fixed bed reactor system. X-ray diffraction, BET surface area, and H2-temperature programmed reduction were used to observe the characteristics of the prepared catalysts. Coke formation of used catalysts was examined by scanning electron microscopy, transmission electron microscopy and the coke amount of used catalysts was measured by thermo gravimetric analysis. Catalysts with smaller particle size had a higher temperature of reduction, which had a positive effect on catalytic activity. The improvement in active site rise and dispersion and the lowest metal crystal size had an effect on catalyst activity. As a result, the Ni/La-Co/Al2O3 catalyst showed the highest activity at a reaction temperature of 800 degrees C and a reaction pressure of 20 bar.

Steam Reforming of Glycerol Over Nano Size Ni-Ce/LaAlO3 Catalysts.

In this work, hydrogen production from glycerol by Steam Reforming (SR) was studied by Ni-Ce catalysts supported on LaAlO3 perovskite in order to effect of the cerium loading amount and the reaction conditions. Nano size Ni-Ce/LaAlO3 catalysts were prepared by precipitation method. The structure of the catalysts was characterized by XRD analysis. The morphology, dispersion and the reduction properties of catalysts was examined by SEM, TEM, H2-chemisorption and TPR, respectively. It was found that 15 wt% Ni-5 wt% Ce/LaAlO3 catalyst showed the highest glycerol conversion and hydrogen selectivity. In addition, the catalyst also showed the high carbon dioxide selectivity and the lowest methane selectivity. The results indicate that the catalyst promotes methane reforming reaction. The highest activity in the 15 wt% Ni-5 wt% Ce/LaAlO3 was attributed to the proper cerium loading amount. Moreover, the lowest metal crystal size and rise in active site were found to have an effect on catalytic activity and hydrogen selectivity. The 15 wt% Ni-5 wt% Ce/LaAlO3 catalyst exhibited excellent performance with respect to hydrogen production at reaction temperature of 450 degrees C, at atmospheric pressure, 20 wt% glycerol solution and GHSV = 6,000 mL/g-cat x hr.

Dehydration of glycerol over niobia-supported silicotungstic acid catalysts.

Liquid-phase dehydration of glycerol to acrolein over nanosized niobia-supported silicotungstic acid catalysts was performed to investigate the effect of the silicotungstic acid loading on the catalytic performance of the catalysts. The catalysts were prepared by following an impregnation method with different HSiW loadings in the range of 10-50 wt%. The prepared catalysts were characterized by N2 physisorption, XRD, FT-IR, TPD of ammonia, and TGA. Dehydration of glycerol was conducted in an autoclave reactor under the conditions of controlled reaction temperatures under corresponding pressure. Increasing HSiW loading rapidly increased the acidity of HSiW/Nb205 catalyst and rate of glycerol conversion, but acrolein selectivity decreased due to enhanced deactivation of the catalyst by carbon deposit. Consequently, it was confirmed that catalytic activity for the dehydration of glycerol to acrolein was dependant on the acidity of catalyst and can be controlled by HSiW loading.

Aqueous phase reforming of glycerol over nanosize Cu-Ni catalysts.

In this work, hydrogen production from glycerol by aqueous phase reforming (APR) is studied by using nanosize Ni-Cu catalysts supported on LaAlO3 perovskite in order to investigate the effects of the copper loading amount and the reaction conditions. Nanosize copper-promoted nickel-based catalysts were prepared by the precipitation method. The structure of the nanosize catalysts is characterized by XRD analysis. The surface area, morphology, dispersion and reducibility of the nanosize catalysts is examined by BET, TEM and TPR, respectively. It was found that 15Ni-5Cu/LaAlO3 catalyst showed the highest glycerol conversion and hydrogen selectivity. The highest activity found in the 15Ni-5Cu/LaAlO3 was attributed to it having the proper copper loading amount. It also has the lowest metal crystal size and the highest surface area, which have an effect on the catalytic activity and hydrogen selectivity. The 15Ni-5Cu/LaAlO3 catalyst showed the best performance for hydrogen production at a reaction temperature of 250 degrees C, a reaction pressure of 20 bar and a feed rate of 5 ml/h.

Effect of ceria on hydrogen production by auto-thermal reforming of propane over supported nickel catalysts.

Autothermal reforming of propane was studied with respect to the addition of ceria to the supported Ni catalysts. Ni/Al2O3 catalysts showed a higher activity than Ni/MgAl catalysts. It was related to the ease of the catalyst reduction. Ni/Ce/MgAl and Ni/Ce/Al2O3 catalysts showed higher propane conversions and higher hydrogen yields. These were related to the particle size and the reducibilities of the catalysts. XRD analysis showed that the added CeO2 decreased the particle sizes of the supported Ni, but increased the amount of NiO on the catalyst surface, thus it improved the resistance to coking.

Steam reforming of glycerol for hydrogen production over supported nickel catalysts on alumina.

The experiment was carried out to produce hydrogen through steam reforming of glycerol over nano-sized Ni catalysts supported on alumina (Al2O3). The catalysts were characterized by BET surface area, metal dispersion, XRD, TPR, NH3-TPD and SEM. 15 wt% Ni/Al2O3 catalysts presented carbon nano fiber after the catalyst was used. However, when the Ni loading was higher than that of 15 wt%, the catalytic activity reduced, and the increase of the Ni particle size and the formation of graphitic carbon occurred. The Ni/SiO2(70)-Al2O3 with the high surface area and the small Ni particle size promoted the catalytic activity and could easily reduce from NiO to Ni, inhibiting the formation of NiAl2O4.

Studies on the dehydration of glycerol over niobium catalysts.

The dehydration of glycerol over nanosize niobium catalysts was conducted in a stainless steel autoclave reactor. The catalysts were prepared by the calcination of niobium oxalate between 200 and 700 degrees C. Catalysts were characterized by N2 Physisorption, XRD and TPD of ammonia to investigate the effect of the calcination temperature and water on catalytic performance, catalysts' structures and acidity. Acrolein was mainly produced about 51-71% with useful by-products such as acetaldehyde and methanol. Amorphous Nb2O5 catalysts calcined at 200-400 degrees C significantly showed higher conversion of glycerol than the crystallized Nb2O5 catalyst calcined at 500-700 degrees C. Also the conversion of glycerol and selectivity of acrolein was increased with increasing the acidity of catalyst, which can be controlled by calcination temperature.

Aqueous phase reforming of glycerol over the Pd loaded Ni/Al2O3 catalysts.

Bifunctional catalysts containing (0.5-1.5 wt%) palladium and 15 wt% of Nickel supported on gamma-Al2O3 were prepared via an impregnation technique and catalysts were characterzed by XRD BET surface area and SEM, respectively. The aqueous phase reforming of glycerol (APR) was conducted over alumina-supported catalysts at different reaction conditions for catalytic activity. Finally, we concluded that the 1.0 wt% Pd 15 wt% Ni/gamma-Al2O3 catalyst evidences higher conversion, hydrogen selectivity, lower alkane selectivity and CO production. This indicate that Pd loaded Ni/gamma-Al2O3 could be a potential catalyst for the APR of glycerol.

Autothermal reforming of propane over Ni-based hydrotalcite catalysts.

Ni-based hydrotalcite catalysts were investigated for ATR of propane in a fixed-bed flow reactor. The reactions were carried out with a H2O/C/O2 stream ratio of 3/1/0.73 at temperatures ranging from 300 to 700 degrees C. The solvents used in the manufacture of Ni-based catalysts noble metal/Ni/MgAl catalysts or substituted active material were changed in order to decrease the level of catalyst deactivation. The use of a mixture of ethanol and water during the formation of the Pd-Ni/MgAl catalyst produced a higher hydrogen yield than that using water only. In addition, the use of acetone in the synthesis of Ru-Ni/MgAl catalyst produced a higher hydrogen yield than using water only. This shows that the solvents used for the noble metals affect the degree of dispersion and particle size of the nickel and prevented carbon deposition resulting in the enhanced hydrogen selectivity and catalyst activity. Active metals were substituted during the preparation of hydrotalcite catalysts. Among the catalysts prepared with various ratio (Ni:Fe) tested at high temperature, the ratio, Ni:Fe = 75:25, showed best performance. There was less sintering of Ni particles due to substitution of the active metal at the optimal ratio.

Autothermal reforming of propane over Mg-Al hydrotalcite-like catalysts.

The performance of hydrotalcite-like catalysts in propane autothermal reforming for hydrogen production was studied in fixed-bed flow reactor. Hydrotalcite-like catalysts were synthesized by coprecipitation and modified co-precipitation by the impregnation method and those were promoted by the addition of noble metals. Reaction test results indicated that hydrotalcite-like catalysts of modified method were showed higher H2-yield than co-precipitation method because surface Ni particles of catalysts by modified method were more abundant. When added noble metals, the activity was enhanced because the size of nickel particles was decreased and degree of dispersion was increased. Also the carbon deposit is low after the reaction. When solvent of solution was changed, activity was increased. It is because degree of dispersion was increased.

Autothermal reforming of propane over hydrotalcite-like catalysts containing promotor.

Hydrotalcite-like catalysts were synthesized by co-precipitation and then these were promoted by the addition of noble metals, alkaline earth metals and ceria. Reaction tests were conducted using a feed of H2O/C/O2 = 3/1/0.37 at a temperature range from 300 degrees C to 700 degrees C. Catalysts were characterized by XRD, TEM, FESEM, TPR, and BET. Reaction test results confirmed an enhancement of the catalytic activity of the promotor-modified catalysts due to low carbon deposition. Among the alkaline earth metals tested, those with larger atomic number exhibited higher activity at a lower temperature range.

Production of hydrogen by autothermal reforming of propane over Ni/delta-Al2O3.

The performance of Ni/delta-Al2O3 catalyst in propane autothermal reforming (ATR) for hydrogen production was investigated in the present study. The catalysts were characterized using XRD, TEM, and SEM. The activity of the Ni/delta-Al2O3 catalyst manufactured by the water-alcohol method was better than those of the catalysts manufactured by the impregnation and chemical reduction methods. The Ni/delta-Al2O3 catalysts were modified by the addition of promoters such as Mg, La, Ce, and Co, in order to improve their stability and yield. Hydrogen production was the largest for the Ni-Co-CeO2/Al2O3, catalyst.