bluuebunny/crossref_metadata_2025 huggingface dataset:
Combustion of diesel spray injected into reacting atmosphere of propane-air homogeneous mixture
Authors: Lee J-H , Lida N
Published: October 2002

The effects of each reaction stage (low-temperature reaction, high-temperature reaction and post-combustion) of a homogeneous mixture (propane/air) on the ignition and combustion of a diesel spray were investigated using a rapid compression machine (RCM). The concentrations of formaldehyde (HCHO) and hydrogen peroxide (H2O2) were calculated in the low-temperature reaction using CHEMKIN. The correlation between soot formation and fuel injection timing was investigated in each reaction stage of the homogeneous mixture. When diesel fuel was injected during the low-temperature reactions, soot formation was more restrained than at any other reaction stage of the homogeneous mixture.
Analysis of the degree of constant volume and cooling loss in a spark ignition engine fuelled with hydrogen
Authors: Shudo T , Nabetani S , Nakajima Y
Published: October 2002

This study analyses factors influencing the thermal efficiency of a homogeneous charge spark ignition (SI) engine fuelled with hydrogen, focusing on the degree of constant volume and the cooling loss. The cooling loss from the burning gas to the cylinder walls in a homogeneous charge SI engine is quantitatively evaluated by analysing the cylinder pressure diagram and the exhaust gas composition. The degree of constant volume burning and the degree of constant volume cooling are also obtained by fitting the Wiebe function to the rate of heat release calculated using the cylinder pressure diagram. A comparison of combustion and cooling characteristics between hydrogen and methane combustion reveals that the cooling loss in hydrogen combustion is higher than that of methane combustion due to a thinner quenching distance and faster burning velocity for hydrogen combustion. It is also made clear that the higher cooling loss in hydrogen combustion results in lower thermal efficiency of hydrogen combustion as compared to that of methane combustion.
Estimation of cycle-resolved in-cylinder pressure and air-fuel ratio using spark plug ionization current sensing
Authors: Lee B , Guezennec Y G , Rizzoni G
Published: October 2002

In recent years, several new sensor technologies have been developed and implemented within automotive industries due to the increasing requirements for improved engine performance and emission reduction. It requires detailed and specified knowledge of the combustion process inside the engine cylinder along with a sophisticated technique in engine diagnostics and control. During the last few years, the ionization current signal detection has been the emerging technology in the new sensor developments, in which the spark plug is used as a combustion probe, to improve the performance and emissions of an automobile engine. In this paper, a novel methodology will be presented which allows the cycle-resolved as well as the mean-value estimation of the air-fuel ratio and in-cylinder pressure based on the ionization current signal measurements. The implementation details of this methodology as well as extensive results will be presented for a wide range of air-fuel ratios. The main advantage of this new approach to process the ionization signal is its strong potential for real-time estimation of the air-fuel ratio and combustion diagnostics of individual cylinders and engine cycles. All the complex physics during the actual events (combustion process, ion generation, engine dynamics, etc.) are automatically self-extracted by this technique from acquired data in an initial off-line mapping phase. Once this has been performed, the air-fuel ratio and in-cylinder pressure can easily be estimated for each individual cylinder and combustion event in real-time with few computational requirements. Hence, this methodology has a high potential for the real-time combustion diagnostics and engine control based on the air-fuel ratio and in-cylinder pressure, while eliminating the requirements for installing expensive air-fuel ratio and in-cylinder pressure sensors. The results indicate that estimation of the cycle-resolved air-fuel ratio and in-cylinder pressure is reasonably accurate and robust, despite the inherently noisy character of the ionization signals, with estimation errors typically in the order of 2 per cent or less, except for very fuel-rich conditions.
Mechanism of hydrocarbon reduction using multiple injection in a natural gas fuelled/micro-pilot diesel ignition engine
Authors: Micklow G J , Gong W
Published: October 2002

Research has shown that a large amount of natural gas (NG) is unburned at light loads in an NG fuelled/micro-pilot diesel compression ignition engine. A mechanism of unburned hydrocarbon (HC) reduction using multiple injections of micro-pilot diesel has been proposed in this paper. Multidimensional computations were carried out for a dual-fuel engine based on a modified CAT3401 engine configuration. The computations show that a split injection with a small percentage (e.g. 30 per cent of diesel in the second injection pulse) can significantly reduce HC, CO and NOx emissions. Based on parametric studies to optimize the timing of both of the injection pulses, HC emissions could be reduced by 90 per cent, with a reduction in CO emissions of 50 per cent and NOx emissions of 70 per cent in comparison to a single-injection pulse-base case configuration.
Diesel Combustion control in common rail engines by new injection strategies
Authors: Beatrice C , Belardini P , Bertoli C , Lisbona M G , Rossi Sebastiano G M
Published: October 2002

The improvements of the solenoid injector and of the electronic control unit of the present common rail (CR) injection system allow the use of multiple sequential injections. Thanks to this feature this advanced common rail system is capable of performing up to five consecutive injections in one engine cycle, thus improving control of the combustion process. In particular, at some operating conditions, activation of a small injection after the main one allows soot produced in the previous stages of the combustion process to be oxidized without increasing nitrogen oxide emissions. This paper describes the experimental results obtained with the application of a prototype of this advanced common rail system both to a Fiat 1.9 JTD eight-valve four-cylinder engine and to a single-cylinder prototype having the same combustion system and large optical access, allowing investigation of the injection and combustion processes. Multidimensional modelling of the combustion process and pollutant formation was also employed to interpret the trends observed in the experiments.
Break-up of liquid fuel films from the surfaces of the intake port and valve in port-fuel-injected engines
Authors: Koederitz K R , Evers M R , Wilkinson G B , Drallmeier J A
Published: October 2002

The atomization of liquid fuel films from the intake port and valve surfaces was investigated. The start-up mixture preparation condition for a port-fuel-injected (PFI) engine was considered in which fuel spray from the injector forms liquid films and puddles upon impact of the cold port and valve surfaces. These fuel films are then re-atomized as a result of aerodynamic and other forces as the intake valve opens. Little information is available on this re-atomization process, which can lead to large droplets and ligaments entering the combustion chamber, resulting in poor combustion. A steady flow axisymmetric valve chamber was used in conjunction with an optically accessible research engine to study this fuel film break-up in detail. Two general atomization forces were observed: Gravitationally (or mechanically) controlled and aero-dynamically controlled. Aerodynamic forces contributed to both ligament break-up and film shear break-up. The different modes of break-up were clearly correlated to air flow separation from the valve and port surfaces. A conceptual model of fuel film break-up from valve and port surfaces is given. The modes of film break-up in the engine were quite similar to those observed in the steady flow experiments. The exception was the presence of break-up due to valve motion. The intake manifold pressure strongly affected the amount of fuel build-up in the port, which in turn affected the fuel pooling and break-up. Injector targeting was also determined to affect the accumulation and atomization of liquid fuel.
Burning velocity measurements of methane-oxygen-argon mixtures and an application to extend methane-air burning velocity measurements
Authors: Rahim F , Elia M , Ulinski M , Metghalchi M
Published: October 2002

Burning velocities of methane-oxygen-argon mixtures have been measured in two matched constant-volume chambers, one spherical and one cylindrical. Burning velocities in the spherical chamber were determined from the pressure rise using a thermodynamic model based on the conservation of mass and energy. Photographic observations made through end windows in the cylindrical chamber at early times were used to study the effects of flame curvature and stretch on the flame speed under constant pressure conditions. The cylindrical chamber was also used to investigate flame shape, cracking and wrinkling. Substitution of argon for the nitrogen in air increased the range of pressure and temperature at which measurements could be made. A correlation for the burning velocity of methane-oxygen-argon mixtures has been developed for the range of pressures from 1 to 40 atmospheres, unburned gas temperatures from 298 to 650 K and fuel-air equivalence ratios from 0.8 to 1.2. Using this correlation and previous results for methane-air mixtures, the burning velocities of methane-air mixtures have been extended to higher temperatures. The results are compared to other experimental measurements and theoretical predictions.
Evaluation of temporal and spatial distribution of nanometric particles in a diesel engine by broadband optical techniques
Authors: Corcione F E , Merola S S , Vaglieco B M
Published: October 2002

In the last few years, there has been an increasing concern about the emissions of ultrafine particles in the atmosphere. A detailed study of the formation and oxidation of these particles in the environment of the diesel engine cylinder presents many experimental difficulties due to the high temperatures, pressures and extremely reactive intermediate species.

To allow investigation of the different phases of the diesel combustion process, high temporal and spatial resolution optical techniques were applied in the optically accessible chamber of a diesel engine at fixed engine speed and air-fuel ratio. Simultaneous extinction, scattering and flame chemiluminescence measurements from the ultraviolet to the visible region were carried out in order to study the diesel combustion process from the soot inception to the formation of soot particles, through the growth of their precursors. These species were characterized as carbonaceous nanometric structures and their sizes were evaluated by the Mie theory.
Analysis of diesel particulate: Influence of air-fuel ratio and fuel composition on polycyclic aromatic hydrocarbon content
Authors: Lombaert K , le Moyne L , Tardieu de Maleissye J , Amouroux J
Published: October 2002

Polycyclic aromatic hydrocarbons (PAH) are pollutants produced during the combustion process and are considered as soot precursors. PAH emissions are not presently regulated although they may have dangerous effects on human health. A comparison is presented here of the influence of engine parameters (air-fuel ratio and brake mean effective pressure) on the composition of par-ticulates. The effects of a water-fuel emulsion on PAH (commonly examined in large engines) are also studied in a 1.9 L commonrail diesel engine: 13 per cent of water added to the fuel decreases the PAH concentration in diesel soot by half. The PAH emissions during cold-start of an automotive diesel engine are also presented.
Polymerization of t-Butyl Vinyl Ether Mediated by an Aluminum Lewis Acid–TrF System and Its Complex Structure–Tacticity Correlation
Authors: Oishi Masataka , Yamamoto Hisashi
Published: October 2002

A variety of aluminum (aryloxide)s were used with triphenylmethyl fluoride (TrF) initiator for the isoselective cationic polymerization of t-butyl vinyl ether. This contribution discusses the relationship between polymer tacticity and counteranion structure, which changed according to the bulkiness, strength and chirality of the Lewis acid combined with TrF so as to make the ionic pair more interactive in the polymerization process. Newly developed organoaluminum activators, 15 and 22, showed mm = 55–57%, which is a more than 10% increase in mm compared with achiral aluminum compounds.
Simultaneous Removal of NO and N2O over Pd-ZSM-5 Catalysts and FT-IR Observations of their Decomposition Routes to N2
Authors: Izumi Yasuo , Kizaki Tetsuro , Aika Ken-ichi
Published: October 2002

Simultaneous removal of nitrogen monoxide and dinitrogen oxide with propene was investigated over Pd-H-ZSM-5 catalysts. Results were compared with reports of simultaneous removal of NO and N2O in the presence of O2 over Co-ZSM-5 and Fe-MFI. The N2O conversion was suppressed in the presence of NO, and the simultaneous removal rates were essentially the same as the NO conversion rates over Co-ZSM-5 and Fe-MFI. In contrast, the simultaneous removal in the presence of O2 was found to be accelerated over Pd-H-ZSM-5 and conventional Pd/SiO2 compared to the sum of the corresponding individual removal rates of NO and N2O. An intense FT-IR peak of NO±0 ligated to the Pd cation inside the ZSM-5 cage was observed at 1868 cm−1 in the promoted simultaneous removal reactions. Under the conditions for the individual removal of NO or N2O and the unpromoted simultaneous removal of NO + N2O, only a weak peak at 1842 cm−1 was observed. The oxygen atom that dissociates from N2O should be the key to promoted catalysis in the coexistence of NO and N2O in order to maintain the Pd cation site clear. The oxygen controls the concentration of surface carbonaceous species to effectively decompose NO, and so as not to inhibit the NO activation.
Supplement to ‘Third‐order transport due to internal waves and non‐local turbulence in the stably stratified surface layer’
Authors: Soomere Tarmo , Zilitinkevich Sergej S.
Published: October 2002

A linear theory of internal gravity waves (IGWs) is applied to consider the IGW‐induced vertical fluxes of kinetic energy, pressure and squared density (or buoyancy) in non‐turbulent stably stratified fluid characterized by the Brunt–Väisälä frequency, N. These fluxes are required in modelling distant links and non‐local transports in the atmosphere. Investigations of the vertical flux of kinetic energy have shown that this flux, caused by the wave component performing the most efficient vertical transport, is proportional to N3. As far as the authors know, the flux of the squared density fluctuations was not systematically investigated. It is shown to be proportional to N5. Copyright © 2002 Royal Meteorological Society.
Delegated Monitors, Large and Small: Germany's Banking System, 1800–1914
Authors: Guinnane Timothy W
Published: October 2002

Banks play a greater role in the German financial system than in those of the United States or Britain. Germany's large universal banks are admired by those who advocate bank deregulation in the United States. Others admire the universal banks for their supposed role in corporate governance and industrial finance. Many discussions distort the German banking system by overstressing one of several types of banks, and ignore the competition and cooperation between the famous universal banks and other banking groups. Tracing the historical development of the German banking system from the early nineteenth century places the large universal banks in context.
Evolution and Human Nature
Authors: Robson Arthur J
Published: October 2002

This paper considers how biological evolution shaped the elements of a simple but complete model of economic decision making. These elements are preferences, beliefs and rationality. Whereas Nature might impose preferences over consumption on the individual, Nature might optimally allow beliefs to be influenced by local knowledge and final choice to be flexible. This reinforces the usual approach. On the one hand, evolution also suggests that some extensions of this model are implausible; on the other, it suggests unexpected directions of generalization. In any case, evolution provides a basis for an overarching economic theory and maintains restrictions on this theory.
The Potential for a Russian State Oil Company: A Critical Analysis of the Russian Oil Business
Authors: Khartukov Eugene M.
Published: October 2002

After seven years of dramatic decentralization and dynamic privatization of Russia's oil industry from, which transformed the wholly state-run oil distribution system into the mostly privatized quasi-market “petropreneurship”, the pendulum of oil control has started to move back. However, despite the obvious need for a better regulated industry and the rising state-centric tendencies, the liberalization of the Russian oil market seems to have passed the point of no return, and the controversial issue of creating a national oil company (NOC) needs to be addressed not only from the political angle but also with regard of economic possibilities and the present market realities.
Model Simulation for Generation and Migration of Methane Hydrate
Authors: Katoh Arata , Nakayama Kazuo , Baba Kei , Uchida Takashi
Published: October 2002

A one-dimensional numerical simulation model has been developed to forecast the distribution of methane hydrate in the subsurface. The model includes the generation and migration of methane, and the process of methane-hydrate formation after sedimentation. The following processes are consideredfor each cell within the model;

1) Calculation of methane generated within the sediment 2) Process of migration of dissolved methane with compacting water 3) Process of migration of gaseous methane as a separate phase, by buoyancy 4) Evaluation of sealing capacity from the hydrostatic equilibrium equation 5) Calculation of the amount of methane hydrate formation from in-situ temperature and pressure

The model will predict the distribution of methane hydrate after applying the above processes for all the sediments.

We use this model to simulate the process of methane hydrate formation at ODP Leg 164 Site 997 at Blake Ridge, offshore Atlantic coast of the USA. At this location, the methane hydrate zone indicated by the bottom simulating reflector (BSR) is about 100 m shallower than the base of gas (methane) hydrate stability zone (BGHS) which is calculated from the model using measured temperatures and pressures. To explain this difference, the following hypotheses are proposed;

1) The BSR is a remnant of the past the BGHS that was created when temperature was higher or sea level was lower. 2) Methane hydrate is being generated between the BSR and the BGHS at present.

The model simulation indicates that analysis, based not only on present physical conditions but also on the geohistrical time scale, is necessary to explain the present day distribution of methane hydrate.
Thermal Focusing by Hydrate Accumulations
Authors: Lerche Ian
Published: October 2002

This paper examines the maximal extent of shallow thermal gradient distortions brought about by hydrate rich regions of finite lateral dimensions in sediments. In general, the anomalous gradient depends on both the thickness of the hydrate layer, the fraction of hydrate in the pore space and the lateral dimensions of the hydrate-bearing body. It is shown that it is difficult to obtain more than about a 5 to 10 percent change in the regional temperature gradient for hydrate fractions of up to 35%-near the maximum of observed values. The identification of hydrate bodies by use of shallow thermal gradient probes would, therefore, seem to be difficult but not impossible.
Oil Company Profitability: Observations on the Use of Oil Product Price Assessments and Associated Errors
Authors: Jenkins Gilbert
Published: October 2002

Oil companies often report the exact price obtained for crude oil sales. Furthermore, crude oil prices may be linked to the price of Brent crude oil which is actively and very transparently traded on the International Petroleum Exchange. Brent crude oil prices are reported worldwide electronically and in many newspapers on a daily basis.

Gas oil (No2. Fuel oil in the USA) is actively traded on the IPE and on NYMEX and the prices are also reported worldwide almost instantaneously. One grade of unleaded gasoline is traded on NYMEX but all other oil products do not have regulated and transparent markets.

The prices of these products are assessed by price reporters following daily discussions with active oil traders. Two prices are assessed and reported, the bid (low) and offer (high) even if no trade has taken place. The oil industry itself and oil products consumers make much use of these assessed prices. The object of this paper is to provide some statistical detail on the differences between various product price assessments made through 2000. From these differences, it is possible to provide an indication of the precision of oil product price assessments. However, it is doubtful if precision data based on a simple determination of the standard deviation of the differences between the assessment made by the various price reporting services would be of practical use.
A Structured Approach to LFS-Complaints in the Rotterdam Region of the Netherlands
Authors: Sloven Ing. Piet
Published: October 2002

In the working area of the DCMR Environmental Protection Agency (EPA) an increasing number of people have registered complaints because of low frequency sound (LFS). A ‘protocol of low frequency sound’ for use in the Rotterdam-area has been developed. The purpose of the approach on LFS is threefold: (1) to offer the several organisations involved a handle to work with, in order to clarify the nature of the LFS complaints and structure them in a procedure; (2) to register their experiences with LFS; (3) to possibly develop a policy on LFS. Conclusions are as follows. (a) The indications lead us to assume that LFS is a growing problem. (b) If the source is not found directly there are complex factors contributing to the LFS-annoyance. (c) Those whose quality of life and health are threatened by LFS need help. (d) The system introduced is a good start. (e) Periodic modifications should lead to an improvement in efficiency. (f) A necessary condition is a consistent, well-equipped and well balanced team of people with experience in handling LFS-complaints. (g) To improve the approach it is worthwhile gathering information from complaint handlers elsewhere.
The Microporosity of Activated Carbon Fibre KF1500 Assessed by Combined CO2 Adsorption and Calorimetry Techniques and by Immersion Calorimetry
Authors: Guillot A. , Stoeckli F. , Bauguil Y.
Published: October 2002

The microporous structure of the activated carbon fibre KF1500 was investigated by applying a new technique as presented here. This was based on a combination of high-pressure CO2 adsorption measurements between 253 K and 353 K with direct measurement of the differential heats of adsorption at 298 K at low and medium coverages.

The validity of this approach was tested by using two activated carbons which has been characterized previously by a variety of techniques, including immersion calorimetry. It appears that a combination of high-pressure adsorption and calorimetry with CO2 alone is a useful tool for the characterization of the whole range of microporosity. This approach confirms earlier observations, according to which the initial stage of adsorption by strongly activated carbons corresponds to adsorption on the walls of large micropores rather than to the primary filling of small micropores.
Oscillatory Adsorption as the Determinant of the Fluctuating Behaviour of Different Heterogeneous Systems
Authors: Patrylak Kazymyr , Patrylak Lyubov , Taranookha Oleg
Published: October 2002

Heterogeneous, catalytic oscillatory reactions as well as the oscillatory process of complex formation based on solid urea have been analysed in an attempt to ascertain the cause of such oscillatory mechanisms. In this context, oscillatory adsorption/desorption, phase transitions of the supported metal employed as the catalyst in the relevant oscillatory oxidation–reduction reactions as well as the reactions themselves have been considered.

Based on an analysis of two oscillatory systems, of which one (i.e. the oscillatory alkylation of isobutane with butenes on a metal-free zeolite catalyst) is not complicated by any phase transitions, whilst the other (i.e. the oscillatory formation of an urea–octane complex via the interaction of urea with a binary vapour mixture of octane and non-complex-forming hydrocarbons) is not complicated by any chemical reactions, it is possible to infer that the source of the oscillatory properties of heterogeneous systems which involve the chemical interaction of their components is oscillatory adsorption which occurs as an uncomplicated self-supporting process which appears to proceed without any increase in the entropy of the system.

The occurrence of oscillatory adsorption in a heterogeneous system leads to an oscillatory behaviour in the corresponding process, involving its simultaneous retardation in a similar manner as does the pendulum of a clock with respect to the untwisting of a spring or the oscillatory circuit of an electromagnetic system with respect to the discharge of a dry battery.
Enhanced Adsorption of Methanol by Oxidised Nutshell Carbon
Authors: Bailey Alan , Williams Mike , Dunne Lyndsay , Beames Lynne
Published: October 2002

A nutshell charcoal was oxidised and reduced and the effect of the treatments on the water adsorption isotherms and methanol vapour penetration noted. Oxidation with 6 M nitric acid increased the penetration times for methanol vapour in dry air, not by just raising the dynamic capacity at low concentrations but also by improving the kinetics of adsorption. Reduction caused the opposite effect. The improvement in the adsorption kinetics is thought to be due to surface diffusion on to the oxidised surface of the transport pores.
Porosity Characteristics of Activated Carbons Derived from Olive Oil Wastes Impregnated with H3PO4
Authors: Khalil Laila B. , Girgis Badie S. , Tawfik Tarek A.M.
Published: October 2002

Locally discarded olive oil waste was tested as a potential raw material for the preparation of activated carbons. Chemical activation by impregnation with H3PO4 was employed using acid solutions of varying concentration in the range 30–70% followed by thermal treatment at 500–700°C. The development of porosity was followed from an analysis of the nitrogen adsorption isotherms obtained at 77 K by applying standard BET and t-plot methods. Carbons with low to moderate surface areas (273–827 m2/g) and total pore volumes (0.27–0.69 ml/g), containing essentially micropores with diameters of 8.2 Å up to 12.4 Å were obtained. Increasing the concentration of impregnant led to the development of porosity with the optimum being attained at 60% H3PO4. Phosphoric acid is visualized as acting both as an acid catalyst promoting bond-cleavage reactions and the formation of new crosslinks and also as a reactant which combines with organic species to form phosphate and polyphosphate bridges which connect and crosslink biopolymer fragments. The present study suggests many applications for environmental pollution control, firstly by utilizing accumulating low-cost agricultural by-products and secondly by producing a multi-purpose high-capacity adsorbent useful in the remediation of micropollutants in various water courses.
Adsorption and Thermal Desorption Behaviour of Asphalt-like Functionalities on Silica
Authors: Park Sangkwon , Jo Myung-Chan , Park Jun-Boum
Published: October 2002

The adsorption and thermal desorption behaviours of seven model compounds containing asphalt-like functionalities were studied on silica. Adsorption isotherms of the model compounds were examined at 25°C and analyzed via the Langmuir isotherm. A series of temperature-programmed desorption (TPD) experiments was also conducted on the silica samples, the activation energy for desorption (Ed) being determined by conventional TPD analysis. The adsorption and thermal desorption behaviours were correlated in terms of the activation energy (Ed tot) for complete desorption. Dimethyl sulphoxide showed the strongest adsorption and the largest value for Ed tot, implying that the high energy consumption necessary to desorb such functionalities plays a key role in the durability of asphalt–aggregate bonding.
Adsorption of Copper Ions on to Tyre Rubber
Authors: Al-Asheh Sameer , Banat Fawzi
Published: October 2002

The adsorption capacity of untreated, chemically and physically activated tyre rubber towards Cu2+ ions was studied. A comparison between these three types of adsorbent was performed in terms of dynamic and equilibrium considerations. The adsorption capacity of physically activated rubber was (marginally) greater than that of chemically activated rubber which, in turn, was greater than that of the untreated materials. The effects of activation temperature and time were considered in the physical activation process. Up to 97% of the Cu2+ ions were adsorbed from aqueous solution when untreated, chemically or physically activated tyre rubber was employed as an adsorbent with initial metal concentrations of 20 mg/ml and 40 ppm, respectively. Increasing the adsorbent concentration resulted in a greater removal of metal ions from the aqueous solution, and increasing the Cu2+ ion concentration in the presence of a constant adsorbent concentration increased the metal ion loading per unit weight of the adsorbent. An increase in the initial pH value of the metal solutions enhanced the adsorption process with all three adsorbents tested. It was demonstrated that the Freundlich and Langmuir isotherms were capable of describing the adsorption of Cu2+ ions by the adsorbents under consideration reasonably well.
Catalytic Conversion of Ethanol over γ-Irradiated CuO/MgO
Authors: El-Shobaky H.G. , El-Boohy H.A. , Doheim M.M.
Published: October 2002

Copper oxide supported on MgO was prepared by the wet impregnation method using basic magnesium carbonate and copper nitrate. Thus, a known weight of basic magnesium carbonate was treated with a known amount of copper nitrate dissolved in the least amount of distilled water necessary to make a paste. The paste was dried and then precalcined for 5 h at 400°C, 500°C or 600°C, respectively. The solids obtained were exposed to different doses of γ-rays ranging between 0.2 MGy and 1.6 MGy. Catalytic conversion of ethanol was carried out at 250–400°C over various irradiated solids employing a micropulse technique. Other techniques used were nitrogen adsorption measurements at −196°C, IR spectroscopy and XRD measurements.

The results obtained revealed that all the catalysts investigated were selective towards dehydration, their activities decreasing slightly on increasing the precalcination temperature over the range 400–600°C. γ-Irradiation brought about a progressive decrease in their catalytic activities with a dose of 0.8 MGy being sufficient to effect a decrease of more than 90% in the initial value. The irradiated catalysts regained virtually all their initial activity upon increasing the γ-ray dose to 1.6 MGy.

These results were discussed in terms of the progressive removal of OH groups from the solid surface by exposure to γ-irradiation in the range 0.2–0.8 MGy. The attainment of the initial catalytic activity upon exposure to a dose of 1.6 MGy was attributed to the creation of surface OH groups due to the interaction between the catalyst samples and water liberated during the early stages of the dehydration reaction.
Some Surface and Catalytic Properties of V2O5–Cr2O3/SiO2, MoO3–Cr2O3/SiO2 and NiO–Cr2O3/SiO2 Ternary Solid Catalysts
Authors: Youssef A.M. , Ahmed A.I. , Samra S.E. , El-Assy N.B. , El-Sharkawy E.A.
Published: October 2002

Ternary vanadia–chromia/silica, molybdena–chromia/silica and nickel oxide–chromia/silica solid catalysts were prepared by the impregnation method. Their structural characteristics were examined using differential thermal analysis (DTA) and X-ray diffraction techniques. The catalytic activities of the prepared samples towards the conversion of isopropanol and cyclohexanol and the kinetics of these catalytic conversions were studied with the aid of a microcatalytic pulse technique. In addition, the surface acidities of selected samples were measured from the percentage of propene produced by the poisoned catalysts.

X-Ray diffraction and differential thermal analysis revealed that the only detectable phase was α-Cr2O3 with the presence of all other phases or spinel not being confirmed. The order of the surface acidities was found to lie in the sample sequence: 3 wt% V2O5–20 wt% Cr2O3/SiO2 > 3 wt% MoO3–20 wt% Cr2O3/SiO2 > 20 wt% Cr2O3/SiO2 > 3 wt% NiO-20 wt% Cr2O3/SiO2, all samples having been precalcined at 500°C.

Catalytic conversion of isopropanol gave propene and acetone, whereas cyclohexene, cyclohexanone and methylcyclopentene (as an isomerization product) were produced from the catalytic conversion of cyclohexanol. The catalytic activity was found to be influenced considerably by the type of impregnating ion employed and by the precalcination temperature, and hence by the surface acidity of the examined catalysts. On the other hand, the Bassett–Habgood and Kiperman equations could be applied in a satisfactory manner to the generation of the various reaction products. The calculated activation energies for the catalytic conversion of isopropanol and cyclohexanol were compared.
Physicochemical and Textural Characterization of Perchlorated and Persulphated Titania
Authors: Moussa Nabawaya A.
Published: October 2002

Samples of perchlorated and persulphated rutile were obtained by soaking the solid in aqueous solutions of HClO4 and (NH4)2S2O8 of 0.05 M, 0.10 M and 0.20 M concentration and characterized by XRD and FT-IR spectroscopic studies and by acidity and textural assessment. The XRD results indicated that the interaction of titania with the loaded anions, i.e. ClO−2 and S2O2-8, resulted in an increase in the volume of the unit cell mainly due to an increase in the c0 value of the tetragonal crystal lattice. The IR spectra showed that both ClO−2 and S2O2-8 anions were linked to the surface via bidentate bridging. Such behaviour created strong acidic sites as probed by pyridine (pKa = 5.3) whose number increased with increasing anion loading. The acidity of the perchlorated samples was higher than that of the persulphated materials. Textural analysis showed that the specific surface areas of both samples responded to the loading process to a lower extent than the total pore volume and correspondingly to the average hydraulic radius, since the latter changed in relation to the total pore volume.
Adsorption of Zinc and Copper Ions by the Solid Waste of the Olive Oil Industry
Authors: Al-Asheh Sameer , Banat Fawzi
Published: October 2002

The adsorption capacity of dried olive oil husks (SWOOI) for zinc ions (Zn2+) and copper ions (Cu2+) was studied. It was verified that the Freundlich and Langmuir isotherms describe the adsorption of Cu2+ and Zn2+ ions reasonably well. Up to 90% of Zn2+ ions and 80% of Cu2+ ions were adsorbed from aqueous solutions when the initial adsorbent and metal concentrations were 30 mg/ml and 20 ppm, respectively. An increase in the SWOOI concentration resulted in greater metal removal from the aqueous solution, and an increase in Zn2+ ion or Cu2+ ion concentration at constant SWOOI concentration increased the metal loading per unit weight of the adsorbent. An increase in the initial pH of the metal solutions enhanced the SWOOI adsorption process. The uptake of Zn2+ ions was also enhanced by decreasing the SWOOI particle size. The presence of a high concentration of soft ions (Na+) strongly suppressed the uptake of Zn2+ ions by SWOOI.
Adsorption Characteristics of CuII on to Industrial Wastewater Sludges
Authors: Weng Chih-Huang , Chiang Pen-Chi , Chang E.E.
Published: October 2002

Primary, activated and aerobically digested sludges from an industrial wastewater treatment plant were collected to investigate their adsorption characteristics towards CuII through the use of batch experiments. Results show that the CuII adsorption rate was fast and could be described by a modified Freundlich equation. The rate of adsorption decreased with increasing surface loading. It was observed that the pH value of the solution was the key factor affecting the adsorption characteristics. The Langmuir adsorption model described the equilibrium adsorption well. The sludge adsorption capacities of CuII were in the range 17–59 mg/g and were affected by the ionic strength. Values of ΔG0 ranging from −7.24 to −7.65 kcal/mol suggested that the adsorption is a physical process which is simultaneously enhanced by the electrostatic effect. The binding strength for CuII adsorption was proposed as: digested sludge > secondary sludge > primary sludge.
Preparation and Characterization of Cationized Cellulose for the Removal of Anionic Dyes
Authors: Hashem A. , El-Shishtawy Reda M.
Published: October 2002

The factors influencing the cationization of microcrystalline cellulose with 3-chloro-2-hydroxypropyl triethylammonium chloride in the presence of NaOH were investigated. The course of the reaction was followed by estimating the nitrogen content of the cationized product while its structural features were confirmed by IR analysis. The ability of cationized cellulose to adsorb anionic dyes, viz. Acid Orange 7, Direct Blue 75 and Direct Violet 31, was investigated at 25°C and 50°C. The equilibrium data obtained were fitted by the Langmuir and Freundlich isotherm models, allowing the corresponding adsorption parameters to be determined. The results showed that the adsorption capacity was dependent on the adsorbent, temperature, the nature of the dye and (to some extent) on van der Waals and hydrogen bonding. Cationized cellulose exhibited a much better adsorption capacity towards anionic dyes than cellulose.
The Surface Properties of Calcite: An Adsorption Model with Orbital Control
Authors: Nikolenko Nikolai V.
Published: October 2002

The energies of unoccupied and occupied orbitals were used as the correlation parameters between the electronic and adsorptive properties of organic molecules. A model describing the chemisorption of organic compounds on CaCO3 involving two types of interaction, i.e. two-electron, donor–acceptor interaction HOMO(adsorbent) → LUMO(adsorbate) and four-electron, three-orbital interaction HOMO(adsorbent) → {LUMO(adsorbate) + HOMO(adsorbate)}, was proposed. It was concluded that strengthening of the bond involved in chemisorption occurred if the energies of the occupied orbitals associated with the adsorbate and adsorbent were concurrent.
Effect of Polymer–Surfactant Adsorption on the Hindered Settling of a Mineral Suspension
Authors: Sadowski Zygmunt , Polowczyk Izabela
Published: October 2002

Competitive adsorption between anionic surfactant (SDS) and neutral poly(ethylene oxide) polymers (PEO) on carbonate mine tailings was investigated, with experiments being performed to check the order of reagent addition. The PEO adsorption plateaux were strongly affected by the presence of pre-adsorbed surfactant molecules, while surfactant adsorption increased in the presence of pre-adsorbed polymer. Polymer–surfactant interaction at the solid–liquid interface depended on the order of reagent addition which significantly affected the floc diameter. Increasing floc diameter was attributed to the formation of a polymer–surfactant complex on the solid surface.
Correlation between Adsorption and Porosity Properties of Alumina Samples as Obtained from Classical Adsorption and Thermal Analysis Methods
Authors: Płanda M. , Staszczuk P. , Pękalska J.
Published: October 2002

The thermodesorption of benzene and water from alumina samples saturated in vacuum desiccators was studied under quasi-equilibrium conditions. The Q-TG and Q-DTG curves obtained showed multi-step weight losses associated with the evaporation of liquid from pores and physisorbed liquid films from active centres of different energy. The adsorption/desorption isotherms of nitrogen on porous alumina samples were measured using sorptiomatic methods allowing the calculation of the corresponding pore size distribution functions. The water vapour sorption isotherms were measured gravimetrically employing an apparatus fitted with a McBain microbalance. A correlation between the porosity parameters and the volume of desorbed liquid is presented illustrating the good agreement obtained.
Studies of Some Properties and the Structure of Polyethylene Glycol (PEG) Macromolecules Adsorbed on a TiO2 Surface
Authors: Chibowski S. , Paszkiewicz M.
Published: October 2002

In the studies presented, the influence of the molecular weight of polyethylene glycol (PEG) on the adsorption and electrical properties at the metal oxide/polymer solution interface has been determined. The main factors responsible for the observed changes in the zeta potential and surface charge of titania were determined on the basis of the data obtained. It was demonstrated that changes in the ionic structure of the Stern layer depend on the molecular weight of PEG and its conformation. A possible mechanism for the changes in zeta potential both with pH and molecular weight was proposed on the basis of values of the surface charge difference (Δσ0) and the diffuse layer charge difference (Δσd) as determined in the presence and absence of the polymer. The thickness of the adsorption layer (δ) on the surface of titania was calculated from the zeta potential changes, both in the presence and absence of the polymer. A distinct influence of the PEG molecular weight was noted on the values of the adsorption layer thickness (δ) determined. The structures of the macromolecules in solution and at the solid/solution interface were compared and from the dependencies obtained some changes in the shape and dimensions of the polymer coils on passing from the bulk solution to the interface were proposed.
Carbon Deposition Studies in the Steam Reforming of Methane Using an Equilibrated Mixture
Authors: Stasińska Beata , Gołębiowski Andrzej , Stołecki Kazimierz , Borowiecki Tadeusz
Published: October 2002

Nickel catalysts are commonly used in many industrial processes including the hydrogenation, hydrotreatment, hydrogenolysis, methanation and steam reforming of hydrocarbons. One of the important problems associated with these processes is the coking of such catalysts and in the present paper a new technique for measuring the coking rate in the steam reforming of hydrocarbons is presented. The methodology employed eliminates objections raised concerning gravimetric methods which are most frequently employed in the study of the rate of coking of catalysts. Qualitative agreement between the results obtained using both methods was demonstrated for catalysts differing both in composition and texture. The new method allows a better characterization of the resistance towards coking of nickel on various supports and in the presence of various promoters.
Geochemistry and Utilization of Montmorillonitic Soil for Cationic Dye Removal
Authors: El-Shishtawy Reda M. , Melegy Ahmed A.
Published: October 2002

Geochemical studies of Egyptian soil-clay minerals from three different depths and their utilization as cationic dye adsorbents are presented. X-Ray diffraction patterns revealed that the dominant clay minerals in the studied samples were montmorillonite, kaolinite and illite. The ability of montmorillonitic soil samples to adsorb cationic dyes, namely Basic Blue 9 and Basic Red 18, was investigated at 30°C. The equilibrium adsorption data were well fitted to the Langmuir model and their parameters determined. The results showed that the adsorption capacity was dependent on the structure of the dyes and the geochemical features of the soil samples.
Firmly Adsorbed Ammonia and Pyridine Species at Activated Kaolinite Surfaces
Authors: Ahmet Tabak , Beytullah Afsin
Published: October 2002

Acid activation increases the protonated species on a kaolinite surface at the expense of coordinately bound NH3 entities. The presence of NH+4 ions on an activated sample is not proof of the presence of protonic acid centres alone since the added proton may have come from the residual water in the interlayer. Progressive dehydration of the surface results in a strong increase in chemisorbed NH3. However, the ‘ring frequency’ region of coordinately bound pyridine (Py) and of the pyridiniumion (Py+) indicates that the strong acid sites on activated kaolinite are of the Lewis type.
Experimental Studies of the Generalized Adsorption Isotherm for the Supercritical Region
Authors: Zhou Yaping , Zhou Li , Bai Shupei , Yang Bin
Published: October 2002

Some problems arise with the characteristic curve proposed by the Dubinin–Polanyi potential theory when this is applied to supercritical adsorption although, as an alternative, the generalized isotherm is capable of well modelling isotherms for different temperatures. In this paper, the general applicability of the generalized isotherm is demonstrated by the experimental adsorption data for N2 and CH4 on activated carbon and silica gel. It has been shown that although the prerequisite of an energetically uniform surface is not essential, the surface concentration is limited to a range beyond which the general isotherm cannot be constructed.
Adsorption of Textile Dyes on to Activated Carbons Synthesized from Solid Waste: Decolourizing Power in Relation to Surface Properties
Authors: El-Sharkawy E.A.
Published: October 2002

Powdered wood of Eucalyptus rostrata (Myrtaceae family) obtained as a solid waste was carbonized at 873 K in a nitrogen flow. The resulting products were activated with steam (CS), zinc chloride (CZ) and phosphoric acid (CA) to obtain three series of activated carbon. The textural properties, including surface area, mean pore radius and total pore volume, were examined from the low-temperature adsorption of nitrogen at 77 K. FT-IR spectroscopy and the base neutralization capacity were used for the detection of surface groups. The adsorption power of the prepared samples for the decolourization of Remazol Brilliant Blue (RBB) and New Coccine (NC) dyes, present as carcinogenic materials in wastewater, was studied at 296 K and 318 K, respectively.

FT-IR spectroscopy and the base neutralization capacities indicated the presence of carboxylic and phenolic groups on the carbon surfaces. The type and amount of activator employed had a considerable influence on the textural characteristics of the samples investigated. An increase in the activator/carbon ratio was also associated with the development of porosity and hence with an increase in the specific surface area. The Dubinin–Radushkevich (DR), Langmuir, Freundlich and Weber–Morris equations were all applied satisfactorily for the calculation of various adsorption parameters, e.g. Ym, a, KF and Eads. In addition, the enthalpy of adsorption was also calculated over the temperature interval 296–318 K.

It was found that the structures of the two dyes studied and the types and amounts of activators employed had a considerable influence on the adsorption parameters estimated.