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By L. D. Haig

"The Texada Mill is a unique iron operation producing High Grade sinter iron concentrate and a by-product copper, gold, silver concentrate. The plant is complex and extremely flexible to handle the many varieties of ore. Two iron concentrates are made and blended. A coarse iron concentrate from primary grinding and a fine concentrate after rougher flotation to remove all the sulphides.All the tailings from iron processing are collected, dewatered, reground and floated for additional copper recovery.The entire milling operation has been carried out in all sea water for seven years and mixtures of sea, fresh, and reclaimed water for ten years prior to that.A very stable float results from the use of sea water at the natural pH8. Reagent Consumption is lower and Metallic Corrosion of mill liners and grinding media is actually less than local fresh water or mixtures of fresh and sea water.Marine growth in pipe lines can be periodically removed by violently bubbling high pressure air up through the water filled mains.Location:Texada Mines is located on tide water on the west side of Texada Island 100 miles northwest of Vancouver, B. C.The Island is served by a 30 car ferry, tug and barge and a scheduled air service from Vancouver to a company maintained air strip near the mine.The climate is moderate with about 30 inches of rain during the winter and relatively dry summers."

Jan 1, 1974

By Theodore H. Boggs

The battle of the gold standard is not limited to one country alone, or even to a single group of countries. It is being waged merrily in many important commercial and industrial quarters. Though it is not always a practical issue calling for immediate attention, it is none the less, quite widely, engaging the thought of bankers and other students of finance. The controversy arises, in the last analysis, because of the desire of men to secure a stable currency. There are two ways of restoring a reasonably stable currency system: (1) the re-establishment of the gold standard, or (2) the deliberate and artificial management of a paper currency. Both systems are well known. The gold standard was in use prior to the war in the principal commercial countries. A currency of inconvertible paper has been at times employed in the past in various countries; for example in Britain from 1797 to 1821, and in the United States from 1862 to 1879. The gold standard, as all are aware, implies the selection of gold as the standard of value. The unit of value is a fixed weight of gold and, so long as the standard remains unimpaired, all other means of payment are maintained at a parity with standard gold coins. And gold coins alone constitute the standard money, inasmuch as their value as bullion equals their value as coins. Under the gold standard this would not be true of any other form of money, although all other varieties of money, including bank notes, government notes and silver coins would be freely convertible into gold money. Strictly speaking, the gold standard also implies that the gold money in turn shall itself be freely convertible, through melting, into gold bullion and freely exportable.

Jan 1, 1925

By A. M. King, J. M. Neilsen

"Roughness at varying scales is an important component of the shear strength of discontinuities. Small scale roughness can be assessed in drillcore and through laboratory testing of drillcore derived samples. Large scale roughness, or waviness, also plays an important part in peak shear strength and a number of methods for its incorporation into defect plane strength models are presented.A number of methods for capturing waviness data from exposed faces are reviewed. A method is presented for deriving waviness from downhole televiewer data, which is shown to be significantly more accurate than structural data derived from core logging. The method is based on work undertaken in the highly anisotropic bedded units of the Hamersley Province, Western Australia where televiewer surveys are routinely undertaken. Values of waviness are derived through a review of variation in dip resolved in the direction of the slope face. This method allows design engineers to incorporate large scale roughness in defect plane shear strengths at the design stage.INTRODUCTIONThere are a number of constitutive models currently being applied by rock mechanics practitioners in calculating defect plane shear strength parameters, such as Patton, Barton – Bandis and Hencher [1, 2, 3]. Most of these shear strength determinations are typically undertaken by determining the base or residual friction angle, and applying corrections for small and large scale surface roughness."

Jan 1, 2015

By Roy T. Bowles

This paper focusses on technological developments which occurred in the village of Deloro, Ontario between 1868 and 1919. These developments illustrate the manner in which improved metallurgical processes linked Ontario mineral resources to industrial expansion. Overview of Deloro The village of Deloro is in Hastings county, about 5 miles from the village of Marmora, the site of the old Marmora iron works and the more recent Marmoraton iron mine. In this area, the Canadian Shield meets the Great Lakes lowlands. The first settlement in the vicinity occurred in the 1820s and was associated with the Marmora iron works. Settlement grew around agriculture. Gold was discovered in Hastings county in 1868. Deloro - the name derives from gold - developed as a concentrated settlement in proximity to several gold mines and the related processing activities. By 1901, substantial smelting works were successfully producing gold and arsenic from local ores. The village was developing as a company town within the framework of benevolent paternalism. For reasons associated with markets and with local ore supplies, the Deloro mills were idle for a period beginning in 1902. Developments in later periods connected Deloro to world events. In 1903, silver was discovered at Cobalt, Ontario. By 1907, M.J. O'Brien, who owned mines at Cobalt, had purchased the Deloro works and was using them to process Cobalt-area ores*.

Jan 1, 1999

By M. P. Tixier

Abstract In a review of the application of electrical logging in Canada, examples are .given of long and short distance correlations by means of the electrical logs. The use of MicroLogging for the determination of permeable and porous formations is explained. The question of log analysis for the quantitative determination of fluid saturation and porosity is .discussed. An example is provided to illustrate the significance of the resistivity gradient. The advantages of the new method of the Laterolog are shown, chiefly for the case of wells filled with high-salinity mud. Introduction Electrical logging techniques developed rapidly in Canada at the time an intensive drilling activity started for the exploitation of the Devonian series in Alberta, namely, at the beginning of 1947. The conventional service was soon thereafter supplemented with the latest technica1 improvements. Canada has been among the first regions to take advantage of MicroLogging*, which has proved a most powerful .tool for the investigation of permeable and porous formations; also, the more recent development known as the Laterolog has ?been introduced in Canada. The Laterolog provides a better determination of .the formations, particularly in the case of salty mud where the conventional logging is greatly handicapped. The various methods of electrical logging are now commonly known in oil industry and have been described in numerous publications ( 1) ( 2) (3).

Jan 1, 1951

By R. A. D. Pattrick, D. A. Polya, D. J. Marsh, J. -J. Bao

"The utility of high-density stream sediment and stream water sampling to the exploration for silver deposits was investigated by the study of the epithermal Ag-Au base-metal prospect at Lagalochan in western Scotland. The geology of Lagalochan is dominated by a calc-alkaline Caledonian intrusive complex emplaced into Dalradian Supergroup rocks (Harris et al., 1988a). The complex consists of subvolcanic porphyrytic rocks associated with intense hydrothermal alteration and brecciation. Early Cu-Ag-Mo-rich mineralization is found in the core of the complex with later Pb-Zn-Ag-Au-As-Sb-rich mineralization toward the margins (op. cit.).Stream sediment sample analysis spatially resolved the Cu-rich and Ag-rich mineralization. Ag and Cu anomalies relative to local background values were found in all size fractions analyzed (-125µm, +125 µm, +180 µm, +250 µm) but the more pronounced anomalies were found in the -125 µm fraction. The coarser fractions generally revealed more erratic but longer dispersion trails. The separation of Cu-rich and Ag-rich mineralization is also apparent in the distribution of relatively high dissolved Cu and Ag in stream waters, particular when expressed relative to the solute load as Cu/TDS and Ag/TDS.The mineralization at Lagalochan is indicated by Ag, Cu and Pb stream sediment and water concentrations that are anomalous with respect to local backgrounds, but are difficult to distinguish from regional backgrounds. This emphasizes the further potential of high-density stream water sampling,in particular, as a viable geochemical exploration tool on a sub-regional scale for epithermal depositsin relatively unpolluted upland terranes."

Jan 1, 1995

By W. M. Goodwin

The gold district of northwestern Quebec, though it has attracted such widespread attention during the past year, is still in the prospect stage throughout, and one must preface any remarks about it with the plain statement that its capacity to produce gold commercially is still subject to proof. However, this proof may be forthcoming any day, and from widely separated localities. Consequently it is of interest to note some of the features of the region and of the prospects now being developed. First I shall note the relation of this mining development to the province of Quebec and to the Dominion; then will follow a brief resume of the known geological facts; and finally I shall describe briefly some of the more advanced prospects developed during the past twelve-month. Those that have followed closely the fortunes of the new gold-field will find little that is new in what follows, but it may serve a useful purpose for others by bringing together scattered items of information and presenting them as a whole. GOLD MINING AND AGRICULTURE First let us consider the gold belt in its relation to the province of Quebec. Apart from the world-renowned asbestos camp south of the St. Lawrence, it is the only mineral development of major importance the province has experienced. It is the first important development in the province's vast area of Precambrian rocks, most of which remains as yet totally unexplored and unprospected. The relative importance of this first mining camp in northern Quebec cannot as yet be gauged, but it is bound to stimulate an active interest in the other mineral-bearing areas now known to exist, and in the vast unexplored spaces.

Jan 1, 1924

By K. Kawagishi, J. Ang, A. Sato, H. Harada

"We have recently proposed a new ""EQ Coating"" bond coat system to solve the problem of secondary reaction zone (SRZ) formation caused by bond coats applied on the hot section components of modem jet engines. A viable EQ coating alloy was previously found for a representative znd generation superalloy, TMS-82+. It would be ideal if the same could be done for a representative 5th generation superalloy, TMS-173. In this paper, we will show that the coating with the best oxidation resistance in the EQ system of TMS-173, although possessing considerably better resistance than TMS-173, did not have sufficient oxidation resistance. In order to improve the oxidation resistance of the EQ coating for TMS-173, we have ventured into ""Pseudo-EQ coatings"". A diffusion couple between the Pseudo-EQ coating and TMS-173, after 300hrs at 1100°C, had a 0-15µm IDZ, but no SRZ. A diffusion couple between a conventional coating and TMS-173 formed a 80-150 µm SRZ. After a 1 hr oxidation test at 1100°C, the PseudoEQ coating formed a thinner oxide layer than the EQ coating, but still contained NiO and spinel. Aerospace"

Jan 1, 2006

By D Maschemeyer

The cobalt production of the Chemical Metallurgical Division of Sherritt Gordon Mines Limited was supplemented, from May, 1962, to June, 1964, by processing 3,500 tons of a calcined cobalt-nickel concentrate. This paper describes the reduction roast -aqueous sulphuric acid leach process and the operating practices employed in recovering cobalt, nickel and copper from this oxidized by-product of a lead-copper operation. Incorporated in this paper is a description of how this process was integrated with the existing ammonia leach -hydrogen reduction process for the recovery of nickel and with the soluble cobaltic ammine process for the recovery of cobalt. Introduction T HE Chemical Metallurgical Division of Sherritt Gordon Mines Limited at Fort Saskatchewan, Alberta, has recently completed ten years of operation utilizing the ammonia leach process for the recovery of nickel, cobalt and copper from sulphide concentrates, matte and other materials amenable to this process. A continuing development program, along with the expansion of certain facilities, has enabled the refinery to attain a production rate of 31, 000,-000 pounds of nickel per year by hydrogen reduction. This represents an increase of approximately 85 per cent over the original design capacity of the plant.

Jan 1, 1965

By T. Liu, C. Shi, T. Fu, M. Zhong

Water inrush in coal mines is induced by the imbalance of the groundwater flow field and the engineering geo-mechanics field. Therefore, to prevent water inrush it is important to predict the critical hydraulic pressure of water inrush in coal seam floors. This paper will investigate a method for conducting theoretical forecasting of the critical hydraulic pressure of water inrush in coal seam floors by adopting the combination method of a genetic algorithm-neural network. First, the topology structure of a neural network (NN) based on genetic algorithms (GA) will be determined and then the critical pressure of water inrush in a coal seam floor using the chosen NN will be predicted. Finally, theoretical forecasting results will be compared with actual measurement results to determine the feasibility and applicability of this method.

Jan 1, 2008

By W. A. Alexander

Introduction In the course of a programme of research on beryllium in progress in these laboratories, knowledge of the recrystallization temperature became necessary. As the information is not available in the literature, the determination of this temperature for metallic beryllium was undertaken. By the reduction of grain size through working and recrystallization and the probable simultaneous induction of preferred orientation, it was hoped to improve the working properties of beryllium at lower temperatures. The recrystallization temperature is usually determined by observing the lowest temperature of annealing at which new crystals are formed in severely cold-worked metal or alloys. This temperature is profoundly influenced by the following factors: the purity of the metal, in the case of an element, or the composition of the alloy; the degree of straining or working; the temperature of straining; the original grain size; and the time held at the annealing temperature. The observed temperature is lowered by higher purity, more severe straining, lower temperature of working, smaller original grain size, and longer time of annealing. Beryllium presents special difficulties in that the percent elongation in tension is effectively zero, so that ordinary squeezing or rolling was not possible. A possible means of straining was suggested by the fact that indentation hardness tests could be made. It was known from earlier work that the metal could be worked at elevated temperatures, so that working at the lowest feasible temperature and quenching might also be a means of producing strain. The purity of the metal is also a point of some uncertainty in the case of beryllium. Losano has prepared 99.96% Be which appears to be the best reported. Distilled metal used in the present work approached this purity. However, by analogy with other metals, residual impurities may have a pronounced effect on the recrystallization. Further purification of beryllium would evidently entail considerable difficulties due to the highly reactive nature of the metal, and was not attempted.

Jan 1, 1947

By Trevor McGiddy

"Australia's prosperity relies significantly on income generated from exports of resources and agricultural products. In 1989-1990, coal was Australia's most valuable export commodity, contributing. A $5.7 billion or 14% of all export income.The abundance and quality of its coal resources and the proximity of Australia to the rapidly developing economies of Southeast Asia were significant factors that encouraged export-oriented growth and investment and will continue to do so. On the other hand, the 1980shighlighted the sensitivity of the industry to international changes in supply and demand, currency and socio-political forces.Following many years of disappointing returns for investors, mainly as a result of falling Australian dollar coal prices, resolve will be necessary to maintain competitiveness with resource-rich nations. In recent years, operators, unions and governments have begun to embark on a long overdue rationalization of domestic issues in a bid to increase productivity and reduce costs.The nature of mining operations is also changing; deeper surface mines and the growth of longwall mining will require the development of new technology and skills. Other challenges emerging from the international environmental debate will require that Australia responds appropriately to demands for cleaner fuels, energy efficiency and environmental responsibility.The future development of the Australian coal industry will therefore be influenced by its own ability to become more efficient and mature in the production of quality coal products and through rational international response to environmental questions."

Jan 1, 1992

By K. Huang

"Solvent extraction (SX) is one of the most effective techniques for the multi-metal separation. However, repetitive pre-treatment of feed-in solutions and/or multi-steps two phase equilibrating in conventional SX processes were always unavoidable due to the poor separation selectivity between those metals with similar physicochemical properties. In this paper, our recent efforts, aimed to develop a “Three Liquid Phase Extraction” (TLPE) strategy for one-step separation and selective enrichment of different metals respectively into three coexisted liquid phases, are reviewed. Various feasible “Three Liquid Phase Systems” (TLPS) are evaluated. The TLPE technique provides a potential possibility for multiphase extraction to separate multi-metals.INTRODUCTIONLiquid-liquid Solvent Extraction (SX) is one of the most effective techniques for metal separation and purification. Traditionally, extraction and separation of multiple valuable metals from the leaching solutions of complex ores, industrial wastes and byproducts have to face such difficulties that multiple target metals with similar physicochemical properties co-exist in the solutions, and therefore their mutual separation selectivities are very poor. In conventional organic-water two phase SX processes, repetitive pre-treatment of feed-in solutions including the adjustment of the solution acidity, removal of impurities and/or multi-step liquid-liquid two phase equilibration were always unavoidable (Wang and Chen, 2001). Only one of the target metals is obtained in each extraction step, therefore the whole separation processes for multi-metal separation are typically very long and costly.Liquid-liquid-liquid three phase extraction is a developing technique for separation of complex systems containing multiple target components (Tan, 2003; Shen, 2006; Yu, 2009). The technique is in fact a three-liquid-phase selectively partitioning of different target components through the control of phase-forming behaviors of extraction system to create a unique separation medium with three co-existed liquid phases. The separation selectivity of “Three-Liquid-Phase System” (TLPS) may derive from its three-layered liquid phases from up to down with different hydrophobic or hydrophilic environment, and therefore each phase has its own specific selectivity for dissolving of an individual component. In a well designed “Three-Liquid-Phase System” (TLPS), multiphase extraction and selective separation of different components respectively into three different liquid phases can be achieved by only one-step of extraction. Owing to its distinct advantages, “Three-Liquid-Phase Extraction” (TLPE) technique has found many potential applications in purification of various organic chemicals (Shen, 2007) and biological activities (Chen, 2002; Tan, 2006; Jiang, 2008), treatment of environmental wastewaters (Shen, 2006; Yu, 2009; Yu, 2010; He, 2012), extraction of valuable components in natural products (Liu, 2010) and separation of multi-metals in complex leaching solutions (Jin, 2009)."

Jan 1, 2012

By Juliana Parreira

The past decade shows record increases in global demand for minerals and metals with an accompanying significant decline in skilled personnel. Mining companies today are examining new technologies to maximize production, reduce costs, and create safer work conditions to deal with this shortfall. Automation of an open-pit mine haulage system is receiving attention as a beneficial option since it provides more consistent and efficient operation of mining equipment, it removes workers from potential danger, it reduces fuel consumption significantly reducing greenhouse gas (GHG) emissions, and it can help optimize vehicle repairs and equipment replacement because of more-predictable and better-controlled maintenance. This paper describes a simulation model under development using the EXTENDSIM software package to examine scale-up issues and constraints of autonomous vehicles in comparison to a manual system. The software can predict and manage Key Performance Indicators (KPIs), such as productivity, safety, cost, equipment failures, fuel consumption, and tire wear under different road and load conditions. By breaking-down the various systems of an autonomous haulage truck and simulating the overall haulage system using a Monte Carlo approach, the model becomes a flexible and powerful tool to use within a mining organization. Direct comparison to a manuallyrun system can be done to show the cost and operational benefits of automation. Project managers can use this tool to guide decision-making about possible application of autonomous haulage trucks at a specific mine site.

May 1, 2010

By Robert B. Parsons

"Although the April 19, 1983 federal budget appears to put greater emphasis on new or expanded government spending programs in an effort to get Canadians working again, the budget proposals contain a light sprinkling of tax changes which could be of some direct benefit to the mining industry.This month, Tax Notes examines some of the more important of these changes.IntroductionSome sectors of Canada's mining industry could benefit from the proposed income tax changes announced by Finance Minister Lalonde in delivering his budget address to the House of Commons on April 19, 1983. Improved depletion allowance rules, expanded investment tax credits, better use of business losses, and inflation proofing of personal capital gains on Canadian common shares are all part of the measures included in Mr. Lalonde's first budget to try to reinvigorate the battered Canadian economy.Improved DepletionUnder the Income Tax Regulations, a taxpayer who incurs Canadian exploration expense (and certain other eligible expenses) is permitted to deduct not only the full amount of the Canadian exploration expense (""CEE""), but also an additional allowance (the so-called earned depletion allowance) equal to one-third of the CEE. Thus, a taxpayer in certain circumstances can claim a deduction of $1.33 for each $1.00 of eligible expenditure, including CEE.Although CEE can be deducted from any source of the taxpayer's income (for example, from investment income, salary income, and so on), prior to budget date the earned depletion allowance was deductible only from the taxpayer's resource profits. This restriction on the deductibility of the earned depletion allowance substantially reduced the attraction of the allowance: few individual investors or investment companies, for example, have the required stream of resource profits, at least when the CEE or other eligible expenditure is made."

Jan 1, 1983

By J. W. Baker

"The Kerr-Addison mine is on the northeast shore of Larder Lake in the township of McGarry, District of Timiskaming, Ontario. It lies just south of the highway leading to the town of Kirkland Lake, 25 miles to the west.The property was first staked in the summer of 1906, by a party of prospectors led by a Dr. Reddick of Ottawa. Subsequent assessment work resulted in the erection of a 20-stamp mill in 1908. Gold from this mill was used in the first gold coins to be minted in Canada. The operation did not prove successful, however, and mining was suspended. In 1914 a consider-able amount of underground development was undertaken by the Associated Goldfields Co., without success.In 1936 Kerr-Addison Gold Mines Co. carried out large-scale sampling from four adits driven into the hillside at the mine. Results were not satisfactory, but it was decided to drill one last deep diamond drill hole from surface. The hole cut a wide section of gold ore. With this encouragement, further development outlined a large tonnage of ore, and a 500-ton mill was put into production in May, 1938. In 1939, its first full year, the mine produced 54,480 ounces of gold and 2,732 ounces of silver. By 1955 the mill had been expanded to a rate of 4,549 tons daily, and in this year 427,193 ounces of gold and 23,490 ounces of silver were produced.From 1938 to the end of 1955 the total production, from 17,473,797 tons milled, has been 3,607,462.74 ounces of gold (0.2064 ounces per ton), and 182,278.56 ounces of silver, with a total value of $131,073,037."

Jan 1, 1949

When underground extractions occur beneath or in close proximity to valleys and other forms of irregular surface topographic features, the observed vertical subsidence at the base of the valley is less than that would be expected in flat terrain, while the valley sides are observed to move inwards towards the centre of the valley. The reduction in subsidence at the bottom of the valley is referred to as upsidence and the convergence of two sides of the valley is termed valley closure. Research coupled with mining experience over the past few decades in Australia has identified valley closure subsidence as being very real and quite significant part of non-conventional subsidence effects, which always have adverse effects on natural features, with risks to water flow and aquatic ecosystems. In this paper, we describe a threedimensional numerical modelling approach to investigate the geomechanical mechanisms which cause the valley closure subsidence behaviour, using distinct element computer package 3DEC. The calibrated models can accurately predict subsidence and horizontal displacements, and they are subsequently extended to specifically study the effect of a series of mining geological and topographical factors on valley closure subsidence phenomenon, by developing a range of hypothetical scenarios. Previous analyses carried out using a two-dimensional numerical modelling technique have identified the potential parameters that affect the valley closure subsidence, which mainly include longwall position, horizontal stresses, valley sloping angle, and valley shape. Further three-dimensional analyses regarding the relationships between the major factors and valley closure subsidence are discussed in this paper. The results have significant implications with regard to both the underlying mechanisms that lead to this nonconventional subsidence behaviour, and how these should be incorporated in future valley closure subsidence prediction and mitigation of its impacts on natural features.

Jan 1, 2015

By Vincent Doyon

For several years, the GDD SSW EM Probe is being used in nickel?s mines in Canada and Brazil to define ore limits, reduce dilution and predict nickel grades. It is used with success to test most if not all percussion blast holes at all Falconbridge Mines in Sudbury and Raglan and all Inco?s Thompson mines. However, after testing the SSW Probe in other metal mines, we realized that EM conductivity does not define ore limits by testing blast holes for copper, zinc or gold. For non-conductive ores, no instrumentation is yet available on the market to reduce dilution, by outlining quickly and inexpensively the real shape of an orebody. To that effect, Instrumentation GDD Inc has developed a new revolutionary photonic probe that will make the reduction of dilution possible by probing blast holes. Once surveyed with the probe, a computer draws graphs of the ore grade as a function of depth for each blast hole. A contribution by Canada Economic Development made possible the development of this new technology. Canmet and Soredem also cautioned this technology developed by Instrumentation GDD Inc. This new photonic probe will allow: 1) to better understand the shape of the orebody 2) to raise the grade of the ore fed to the mill 3) a more complete extraction of the ore 4) to raise the competitiveness of mines

Oct 1, 2004

By Michel Dagbert

"This paper illustrates the different ways grade-tonnage curves can be generated f or a mineral deposit. It emphasizes systematic discrepancies between reality, estimates and actual production according to different estimation methods and grade control programs. It does not offer a universal solution to the prediction of grade-tonnage curves. Hopefully, it will inspire caution to mineral economists who use estimated grade and tonnage data in the establishment of an optimum cut-off grade for a mining operation.IntroductionThe value of a mineral development venture often depends on a grade-tonnage curve. Statistics can help. The idea is to divide mentally the orebody into small blocks called selective mining units or SMUs. A SMU is an idealized version of the quantity of rock the grade of which will be tested against the cut-off at the time of mining. It could be as small as a truck load or a shovel load in very selective operations like some uranium mines where radiometric probing of each truck or car is performed. More typically, in an open pit operation, it will be the smallest zone flagged as ore from blast hole data, e.g. a 5 m by 5 m by 10m block, if blast holes are on a 5 m grid and bench height is 10m. Having defined the SMUs, the grade-tonnage curve determination amounts to evaluating the grade distribution of all the SMUs that can be mined in the depo sit. If we know this distribution we simply apply the cut-off to it and we get the number of SMUs above the cut-off (i.e. ore tonnage) and their average grade. .Assessment of the grade distribution of SMUs from exploration drill hole data is not an easy exercise and much has been published on the subject (David, 1972; Marechal , 1972; Huijbregts, 1975; Marechal, 1975; Guibal and Touffait, 1982). In this paper, we use a gold mine example to illustrate the influence of SMU size on the results. With the same example we also show that ""common-sense"" methods of grade-tonnage curve determination can sometimes be misleading."

Jan 1, 1987

By Peter Claus

In the last years, supported gold catalysts with particle sizes smaller than 10 nm have attracted a lot of attention. While gold bulk metal is rather inert in chemical reactions and, thus, is of low interest for catalysis, highly dispersed gold particles supported on oxides as TiO2 or ZrO2 show surprisingly high activities in some reactions important for the chemical industry. The oxidation of carbon monoxide at low temperatures is mainly used as model reaction to study the unusual properties of gold catalysts [1]. On the other hand, to evaluate the catalytic potential of gold, other chemical reactions which allow to control also the selectivity have to be considered. The selective hydrogenation of ???-unsaturated aldehydes to allylic alcohols is of both commercial relevance (e.g. in fine chemical and pharmaceutical intermediate production) and specific scientific interest [2]. Note that thermodynamics favors hydrogenation of the C=C over the C=O group (stronger negative free reaction enthalpy of 35 kJ/mol), and for kinetic reasons the C=C bond is more reactive than the C=O group. Thus, in the presence of most of the conventional hydrogenation catalysts, based on Pt, Rh or Pd, -unsaturated aldehydes such as acrolein and crotonaldehyde are hydrogenated predominantly to the saturated aldehydes and only to a minor extent to unsaturated alcohols. Therefore, it is desirable to find catalysts which are able to control the intramolecular selectivity by hydrogenation preferentially the C=O group while keeping the olefinic double bond intact (Fig. 1).

Oct 1, 2003