Reduced Nickel Catalyst Research Articles

Hydrogen production from cellulose using a reduced nickel catalyst

Cellulose, a major component of biomass, was gasified in hot-compressed water using a reduced nickel catalyst at different reaction temperatures from 200°C to 350°C. The reaction mixture was separated to gases, oil, char and water-soluble products to discuss reaction mechanism based on the product distribution. The water-soluble products were considered as intermediates, and the obtained hydrogen was consumed by methanation reaction. The following simplified reaction scheme was proposed: Cellulose → decomposition water-soluble products → Ni gasification gases (H 2+CO 2) → Ni methanation gases (CH 4+CO 2) The effect of supports was also examined. Supports showed the strong effect on the gas yield, and the catalytic activity depended on the overall catalyst size rather than the surface area.

98/03076 Hydrogen production from lignocellulosic materials by steam gasification using a reduced nickel catalyst

To screen for rapidly growing trees, lifetime growth histories of 160 species were estimated from data collected in a permanent 50 ha census plot in tropical moist forest in Panama. Most of the 160 species had never been studied before in detail, and newly encountered species with rapid growth might provide better techniques for reforesting degraded soils in Central America. To estimate lifetime growth, polynomial regressions were fitted to instantaneous growth rates expressed as a function of log-transformed diameter at breast height (dbh). These functions represent a differential equation in dbh, and explicit solutions for the equations provided dbh trajectories as a function of age (starting at 1 cm dbh, which was the smallest size included in the census). Dbh trajectories were calculated for 160 species, and full growth data are presented for the 28 species that ranked among the fastest 15 to reach a dbh of 10, 30, or 60 cm. Dbh trajectories based on growth of one standard deviation above the mean were also estimated for these species by fitting a polynomial regression to the residuals around the original regression. The fastest-growing tree in the 50 ha plot was the balsa, Ochroma pyramidale, which reached 10 cm in 5 years and 30 cm in 10. Cavanillesia platanifolia, Trema micrantha, Zanthoxylum belizense, and Vochysia ferruginea were the other top-ranking species. At mean growth, the top 15 ranking species required 5–25 years to reach 10 cm, 10–67 years to reach 30 cm, and 32–111 years to reach 60 cm, starting at 1 cm. At growth one standard deviation above the mean, the same species requried 4–18 years to reach 10 cm, 8–35 years to reach 30 cm, and 19–69 years to reach 60 cm dbh. We recommend that the little-known species from this list be further tested in reforestation trials.

Cellulose decomposition in hot-compressed water with alkali or nickel catalyst

Cellulose, a major component of woody biomass, was reacted in hot-compressed water using a sodium carbonate catalyst, a reduced nickel catalyst or no catalyst at different reaction temperatures from 200 to 350°C. The reaction mixture was separated into oil, gases, residue and aqueous phase to discuss the reaction mechanism based on the product distribution. Hydrolysis can play an important role in forming glucose/oligomer, and the obtained glucose/oligomer can decompose quickly to non-glucose aqueous products, oil, char and gases. Under the catalyst-free condition, the interpretation of the observation led to a simplified reaction scheme, which produced finally char and gases through oil as intermediates. With regard to the alkali catalyst, the observation suggested a role of the alkali catalyst in inhibiting the formation of char from oil (stabilization of oil); resulting in oil production. On the other hand, the nickel catalyst could catalyze the steam reforming reaction of aqueous products as intermediates and the methanation reaction.

98/02056 Hydrogen production from lignocellulosic materials by steam gasification using a reduced nickel catalyst

98/02056 Hydrogen production from lignocellulosic materials by steam gasification using a reduced nickel catalyst

Hydrogen Production from Cellulose in Hot Compressed Water Using Reduced Nickel Catalyst: Product Distribution at Different Reaction Temperatures.

Cellulose, a major component of woody biomass, was gasified in hot-compressed water using reduced nickel catalyst at reaction temperatures from 200 to 350°C. The product distribution was analyzed at different temperatures and reaction times. Cellulose decomposed to water-soluble products at first, and then, the water-soluble products reacted to form hydrogen and carbon dioxide. The obtained hydrogen was consumed by a methanation reaction to form methane. A reaction model for catalytic and noncatalytic cellulose decomposition is proposed.

Kinetic Model for Soybean Oil Hydrogenation Using Loop Reactor.

A kinetic model including isomerization of fatty acids for soybean oil hydrogenation considering the adsorption of fatty acids on the catalyst surface affecting the hydrogenation rate has been evaluated in this study. The hydrogenation of soybean oil was conducted in a 12 l loop reactor equipped with a venturi nozzle. A reduced nickel catalyst was adopted. The hydrogenation experiment was carried out an experimental design with respect to reaction temperature, flow rate of catalyst-oil mixture, hydrogen pressure and reaction time. Adsorption of fatty acids including trans-acids on the surface of the reduced nickel catalyst significantly affected the reaction rate of the hydrogenation. The adsorption equilibrium coefficients of linolenic and linoleic acids were much greater than those of oleic and elaidic acids, which indicated that the former acids were hydrogenated faster than the latter acids. The time course of fatty acid concentration calculated from the hydrogenation rate constant derived from the kinetic model proposed in this study was in good agreement with those obtained from experiments. The kinetic model explained the hydrogenation totally with consideration of trans-acid formation.

9-2.ニッケル触媒を用いた水溶液中でのセルロース及びコナラ木粉の熱化学反応による水素の製造(Session(9)バイオマス)

9-2.ニッケル触媒を用いた水溶液中でのセルロース及びコナラ木粉の熱化学反応による水素の製造(Session(9)バイオマス)

Hydrogen Production from Wet Cellulose by Low Temperature Gasification Using a Reduced Nickel Catalyst

Abstract Wet cellulose was gasified at 350 °C for 1 h in the presence of a reduced nickel catalyst under various operating pressures (8–18 MPa). Hydrogen was obtained specifically at high operating pressures of 17–18 MPa. Under the operating pressure of 18 MPa, the gas yield increased with catalyst loading and reached 91 wt% at the catalyst loading of 20 wt%. The gas consisted of hydrogen of 50 vol%, carbon dioxide of 40 vol% and methane of 10 vol%, which was equivalent to that the hydrogen of 70% in the cellulose was recovered as hydrogen gas.

Effect of Pressure on Low Temperature Gasification of Wet Cellulose into Methane Using Reduced Nickel Catalyst and Sodium Carbonate

Abstract A water slurry of cellulose was directly gasified to methane using a reduced nickel catalyst and sodium carbonate at 400 °C under pressure (9-28 MPa) for 1 h. Methane yield depended on operating pressure and the highest yield was 190 mg per 1 g cellulose at around 15 MPa This value was 1.5 times that in the literature.

ChemInform Abstract: Iron as a Catalyst for the Hydrogenation of Benzene

Abstract The activities are reported of reduced precipitated iron catalysts and promoted and unpromoted iron synthetic ammonia catalysts for benzene hydrogenation over the temperature range 380–473 K. Singly promoted iron (5.50% Al2O3) was the most active of the iron catalysts, being, at 450 K, some 22 times more active than unpromoted iron and some 4.5 times more active than iron prepared by NaOH precipitation of the hydroxide. The results with doubly promoted iron (2.29% Al2O3, 1.64% K2O) were somewhat equivocal in that benzene was more strongly absorbed on this catalyst and cracking was more extensive at all temperatures. Both iron nitride, Fe4N, and iron carbide, Fe2C, prepared by nitriding and carbiding reduced unpromoted iron showed no benzene hydrogenation activity. A reduced copper catalyst had, effectively, zero activity under these reaction conditions (~7:1 H2:C6H6). However, a reduced nickel catalyst was more than 4 times more active than singly promoted iron at 450 K and was able to maintain this higher activity for long contact periods. All of the iron catalysts showed a (frequently sharp) decrease in activity with time attributed to adsorption of hydrocarbon complexes which can under certain conditions lead to the formation of nuclei of an iron carbide.

Iron as a catalyst for the hydrogenation of benzene

The activities are reported of reduced precipitated iron catalysts and promoted and unpromoted iron synthetic ammonia catalysts for benzene hydrogenation over the temperature range 380–473 K. Singly promoted iron (5.50% Al 2O 3) was the most active of the iron catalysts, being, at 450 K, some 22 times more active than unpromoted iron and some 4.5 times more active than iron prepared by NaOH precipitation of the hydroxide. The results with doubly promoted iron (2.29% Al 2O 3, 1.64% K 2O) were somewhat equivocal in that benzene was more strongly absorbed on this catalyst and cracking was more extensive at all temperatures. Both iron nitride, Fe 4N, and iron carbide, Fe 2C, prepared by nitriding and carbiding reduced unpromoted iron showed no benzene hydrogenation activity. A reduced copper catalyst had, effectively, zero activity under these reaction conditions (~7:1 H 2:C 6H 6). However, a reduced nickel catalyst was more than 4 times more active than singly promoted iron at 450 K and was able to maintain this higher activity for long contact periods. All of the iron catalysts showed a (frequently sharp) decrease in activity with time attributed to adsorption of hydrocarbon complexes which can under certain conditions lead to the formation of nuclei of an iron carbide.

The Enantioface-differentiating (Asymmetric) Hydrogenation of the C=O Double Bond with Modified Raney Nickel. XXXVI. The Development of Modified Nickel Catalysts with High Enantioface-differentiating Abilities

Abstract Various types of modified nickel catalysts were prepared and their enantioface-differentiating (asymmetric) abilities were examined. It was found that the presence of aluminum or related metal compounds in the catalyst was unfavorable for the effective enantioface-differentiating catalyst. The modification with a solution containing tartaric acid and inorganic salt gave a high enantioface-differentiating ability to Raney nickel and reduced nickel catalyst. Among the modified nickel catalysts examined, the Raney nickel modified with tartaric acid and sodium bromide gave the best result with respect to the hydrogenation activity and enantioface-differentiating ability (optical yield 88%). NaBr adsorbed on Raney nickel was found to inhibit the nonenantioface-differentiating hydrogenation.

Adsorption and reaction of cyclopropane and hydrogen on nickel: Changes in selectivity with temperature

A comparative study was made of the cyclopropane chemisorption on pure nickel film surfaces and of the hydrogenation and hydrocracking of cyclopropane on both the films and a reduced nickel catalyst. In a range of higher coverages, the chemisorption of cyclopropane at 273 °K was accompanied by selfhydrogenation to propane, and, as a characteristic feature of the process on nickel, cracking to methane and ethane was also observed. Some further data concerning composition and properties of the chemisorbed layers are also given. Cyclopropane was reacted with hydrogen on nickel films in an UHV apparatus at 195 and 273 °K, and in the range of 300–600 °K using a microcatalytic-pulsed reactor coupled to a gas chromatograph. For the purpose of comparison, hydrocracking of propane was also investigated under the same conditions on the nickel powder catalyst. From the temperature variation of the product composition thus obtained, two types of cyclopropane cracking could be distinguished. With the low-temperature selective hydrocracking, the percentage of methane and ethane in overall product was constant over the range of 195–500 °K. Beyond this range the nonspecific hydrocracking began, characterized by the increasing proportion of cracking in products and by the prevalence of methane over ethane. No distinction could be made between the latter process and the propane or propylene hydrocracking. Some mechanistic consequences of the experimental findings are discussed. A concerted simultaneous splitting of two bonds in the chemisorbed cyclopropane ring is suggested as the reaction path for the low-temperature fragmentation.

Stereoselective hydrogenation of xylenes and their tetrahydro derivatives by a reduced nickel catalyst.

o-, m-, p-xylene and their tetrahydro derivatives were hydrogenated by a reduced nickel catalyst over the temperature range 150∼250°to investigate the mechanism of the stereoselective formation of cis and trans isomer in vapor phase. The selectivity for the formation of trans isomer was the greatest with p-xylene and the smallest with m-xylene. More than 50% trans isomer was produced with p- and o-xylene but not with m-xylene over the entire temperature range investigated. A similar result was obtained also for the hydrogenation of dimethylcyclohexenes. On the basis of these findings, the Horiuti-Polanyi-Siegel mechanism, as shown schematically in Fig. 6, was discussed taking into consideration various adsorbed types for the half-hydrogenated state. It was shown that the mechanism will meet some difficulties to account for the experimental results. On the other hand, the trans addition of hydrogen to π-allylic adsorbed species giving rise to trans isomer was considered to occur in particular at higher temperatures.

The Liquid-Phase Hydrogenation of Benzonitrile over a Nickel Catalyst.

The kinetics of liquid-phase hydrogenation of benzonitrile in the presence of a reduced nickel catalyst were studied at temperatures ranging from 70 to 100°C. The initial concentrations of benzonitrile in 250 ml methanol varied from 25 to 50g.Under given conditions, the absorption rate of hydrogen was first order in catalyst concentration. It was independent of the partial pressure of hydrogen and of the concentration of benzonitrile over a relatively low conversion range. The activation energy was calculated to be 8.8 Kcal/mol.The reactions to form Schiff-bases and secondary amines became evident when the absorption rate of hydrogen was low. Such reactions were markedly accelerated when the hydrogenation reaction was interrupted.Hydrogenation of benzonitrile was also studied in the presence of n-butylamine. The results indicated that when the absorption rate of hydrogen was high, the amine was involved in the formation of Schiff-bases as well as secondary amines only to a very slight extent. Upon interruption of the hydrogenation reaction, however, the presence of amine gave rise to the formation of mixed Schiff-bases.

The Liguid-Phase Hydrogenation of Isophthalonitrile over Nickel Catalysts

The kinetics of liquid-phase hydrogenation of isophthalonitrile in methanol-ammonia (1:1) in the presence of a reduced nickel catalyst and a Raney nickel catalyst were studied at temperatures ranging from 90 to 110°C.In the presence of a reduced nickel catalyst, the reactions proceeded in a stepwise manner, m-cyanobenzylamine being the intermediate. Under given conditions, the absorption rate of hydrogen was first order in catalyst concentration and agreed with the Langmuir-type rate equation for the partial pressure of hydrogen. At a partial pressure of hydrogen above 70 kg/cm2, the absorption rate was not affected by the partial pressure. The effects of isophthalonitrile concentration also agreed with the Langmuir-type rate equations. The adsorption of isophthalonitrile and m-cyanobenzylamine was relatively strong and their adsorption equilibrium constants almost comparable with each other. The specific rate constant for isophthalonitrile was almost three times as much as that for m-cyanobenzylamine. The activation energy for the reaction was calculated to be 12.8 kcal/mol.Similar reaction mechanisms can also be applied for the hydrogenation in the presence of a Raney nickel catalyst.

Mechanism of the deactivation of nickel catalysts by steam under pressure

1. An investigation was made into the deactivating effect of steam on nickel catalysts in the course of their preparation by reduction with hydrogen under pressure. 2. It was shown that pretreatment of a mixture of nickelous oxide and carrier (Al2O3, MgO) with steam under pressure results in the formation of catalysts of low activity. Similar treatment of a reduced carriersupported nickel catalyst has a very much smaller effect on activity. 3. It was shown that steam treatment of a coprecipitated mixture of nickelous oxide and alumina ( or magnesia) under pressure results in a far-reaching irreversible change, namely recrystallization with great reduction in specific surface. 4. It is evident that the deactivation of reduced nickel catalysts by steam in the course of their use is due to the formation of nickelous oxide films or phases that rapidly recrystallize and are reduced with difficulty with formation of coarsely dispersed nickel. It is probable that the mechanism here proposed is applicable also to the deactivation of iron catalysts by water vapor.

Kinetics of the methane‐steam reaction

AbstractA kinetic study was made of the reaction of steam and natural gas over a reduced nickel catalyst at a temperature range of 637° to 1,180°F.The rate of reaction is first order with respect to methane. The effect of temperature could be expressed by an Arrhenius type of equation. Both carbon monoxide and carbon dioxide are formed as primary reaction products.