Showing papers on "Calcium oxide published in 1974"

The reactivity of calcium oxide towards carbon dioxide and its use for energy storage

Abstract: By using calcium carbonate powder of particle size ∼ 10 nm (and therefore of high surface area) it has been shown that the reaction CaCO3 ⇄ CaO + CO2 can be made almost wholly reversible. A reactivity of 93% was achieved, (i.e. 93% of the calcium oxide reacted with carbon dioxide) and this was maintained for 30 24-h decomposition-back reaction cycles at 629 °C with no detectable decrease. This material has an energy storage capacity of 200 Wh/lb, but only about 1 kWh/ft.3 When this calcium carbonate was pressed, however, to increase its bulk density (from 0.1 to ∼ 1 g/ml) there was a large decrease in its surface area and a smaller decrease in its reactivity on undergoing a few decomposition and back reaction cycles. Scaling up of the sample size from 20 mg to 10 g only had a small (× 3) effect on the rates of decomposition and back reaction.

Use of the Langmuir method for kinetic studies of decomposition reactions: calcite (CaCO3)

Abstract: The Langmuir method for measurement of vapour pressures has been tested for use in studies of decomposition reactions. The isothermal weight loss in vacuum from cleavage (10text-decoration:overline11) planes of calcite (CaCO3) single crystals was measured continuously at temperatures from 934 to 1013 K. The rate was constant until approximately 80% of a 1 mm slice had decomposed. The apparent activation enthalpy was 205 kJ (49 kcal) mol–1. Micrographic examination showed an approximately 30 µm thick layer, probably a metastable form of calcium oxide, separating the calcite from the growing layer of oriented stable calcium oxide. The 30 µm layer yielded a single X-ray diffraction peak which was displaced slightly from the strongest (220) peak of the oriented normal calcium oxide. Lower apparent activation enthalpies measured in previous studies of calcite decomposition in inert atmospheres are suggested to result either from partial diffusion control of the process or from catalysis of the direct formation of normal calcium oxide by carbon dioxide or a component of the system atmosphere. The ratio of the measured decomposition rate in vacuum to the maximum rate, which can be calculated from the Hertz–Knudsen–Langmuir equation, is suggested to be a useful parameter in correlating and predicting decomposition reaction rates.

Solar heating system

Abstract: A solar heating method and apparatus including a system for storing solar heat is provided for heating a house, building or other area. A chamber is filled with calcium oxide which is fed on demand to a tank of water where it converts to calcium hydroxide releasing energy which heats the water. Heat from the water is removed through a heat exchanger for heating a building, or the like, and the calcium hydroxide is de-watered utilizing a solar heater which converts the calcium hydroxide back to calcium oxide. The calcium oxide is transferred back into the calcium oxide storage container.

Method of rendering waste substances harmless

Abstract: A method for rendering harmless an oily waste material comprising mixing an alkaline earth metal oxide with a surface active agent which delays reaction between the alkaline earth metal oxide and water, combining the mixture with said oily material, and reacting the alkaline earth metal oxide charged with the waste material with approximately the stoichiometric amount of water to convert the alkaline earth metal oxide to the hydroxide. The alkaline earth metal oxide is preferably calcium oxide and advantageously it is also mixed with a hydrophobizing agent prior to mixture with the oily waste material. The proportions are desirably such that the end product is a solid which can be used as a lining in road construction and at dump sites.

Shaped zirconium oxide bodies of high strength

Abstract: Shaped bodies of zirconium oxide of high mechanical strength can be prepared by sintering a pulverulent mixture of 30% to 90% monoclinic zirconium oxide, 7.8% to 69.5% zirconium oxide conventionally stabilized by bound oxides of metals having an ionic radius similar to that of zirconium, and 0.5% to 2.2% magnesium oxide and/or calcium oxide at above 1,600*C, the combined amount of the stabilizing oxide and of the magnesium and/or calcium oxide in the sintered body being 2.5% to 3.5%.

Catalysts and methods of making

Abstract: A sintered catalyst article is prepared by: molding into a shaped article and aging (I) either A. a refractory powder of calcium aluminate substantially free of silicon dioxide, alone, or B. a homogenous mixture of 1. said refractory powder and 2. at least one member selected from the group consisting of aluminum oxide, calcium oxide, beryllium oxide, magnesium oxide, strontium oxide and a compound which is converted by heating to one of said oxides; (II) sintering said molded and aged article at a temperature above 1150°C; the thus sintered catalyst article containing 10 to 60 wt. percent of calcium oxide, 30 to 90 wt. percent of aluminum oxide, 0 to 30 wt. percent of at least one oxide selected from the group consisting of beryllium oxide, magnesium oxide and strontium oxide, and less than 0.2 wt. percent of silicon dioxide.

Studies on the system sodium oxide-calcium oxide-silica-water

Abstract: In hydrothermal reactions of lime and quartz with water or aqueous NaOH at 150 °C or 180 °C and Ca: Si = 0.83, the rate of reaction of the quartz increases with NaOH concentration. At 180 °C and Ca: Si = 0.83, the conversion into tobermorite of the semi-crystalline calcium hydrosilicate initially formed occurs more slowly at NaOH concentrations of 0.15–2.00 M (NaOH: SiO2 = 0.05 to 0.63) than in water or 5 M-NaOH. With long reaction times at 180 °C and Ca: Si = 0.83, increasing NaOH concentration causes pectolite to replace xonotlite as the main product. At very low water contents, NaCaHSiO4 is formed; this compound is conveniently made by grinding together solid NaOH, Ca(OH)2 and quartz in normally humid air and heating the mixture in a closed vessel at 180 °C.

Process for manufacturing gaseous mixtures rich in hydrogen

Abstract: A hydrogen manufacturing process is carried out by catalytic steam reforming of normally gaseous or liquid hydrocarbons using a catalyst comprising substantially silica-free aluminum oxide at temperatures above 850° C., the catalyst optionally also comprising more than 10 weight percent, preferably more than 20 weight percent, of at least one of the group consisting of beryllium oxide, calcium oxide and strontium oxide.

Expansive cement additive and process for producing the same

Abstract: An improved finely pulverized expansive cement additive which causes the cement mortar or concrete mixed therewith to bear increased chemical prestressing property, the clinker of said additive substantially consisting of alite crystals containing fine crystals of calcium oxide therein and a phase substantially consisting of optic-microscopically amorphous calcium sulfate in which said alite crystals are dispersed.

Process for the production of reactive calcium oxide

Abstract: Reactive calcium oxide is produced on an industrial scale by decomposing calcium carbonate having a grain size of less than 200 μm at a temperature of at least 850° C and at a CO 2 --partial pressure of not more than 40% of the CO 2 --equilibrium pressure corresponding to the formation of the reactive calcium oxide.

Immediate amelioration of wet cohesive soils by quicklime

Abstract: Immediate amelioration of wet cohesive soils by lime, a current practice in earthwork operations for highway construction in Belgium, is performed with 1 to 1.5 percent quicklime. Such small doses are effective because they agglomerate the soil into crumbs that are stable in free water and retain their individuality after kneading and compaction. Procedures for evaluating the crumb stability have been developed. Additions of 1 percent quicklime produce not only the immediate amelioration effects but long-term strength gains as well. Strontium and barium hydroxides produce the same immediate effects as equivalent amounts of lime but far lower long-term strength gains. Lime percentage has far less incidence on immediate amelioration than on long-term strength gains.

Carrier and catalyst for chemical processes and method of preparing said catalyst

Abstract: The carrier for catalysts used in chemical processes to convert natural gas is a fused mixture of aluminium oxide taken in the quantity of not less than 50 per cent by weight with at least one refractory oxide selected from the group, consisting of titanium oxides, nickel oxides, magnesium oxide, calcium oxide, iron oxides, silicon dioxide, boron oxide, and chromium oxides. An example of such a mixture is metallurgical slag which is formed in the production of ferro titanium ferrochromoboron, ferroboral, nickelboron, ferroboron prepared by the alluminothermy. As an active component is applied to the carrier, the catalyst is prepared. The catalyst can also be a mechanical mixture of the active component with the carrier. The active component can be any metal, for example nickel, chromium, aluminium, silver, platinum, copper and other metals which are selected depending on the requirements of a particular process. The content of the active component is from 0.3 to 40 per cent by weight calculating with reference to metal.

Diffusion and diffuse cementation in lime and cement stabilised clay soils - studies of plasticity and aggregation

Abstract: The studies described provide further evidence for the diffusion of lime into unpulverised lumps in coarsely pulverised soil stabilised with lime or cement. The diffused lime produces cementation of all the clay present, but even when strong cementation has been produced the crystallinity of most of the clay is little altered, and even its surface activity is largely unimpaired: yet every particle of clay becomes cemented. This type of cementation is described as diffuse cementation. The studies reported are of plasticity and linear shrinkage characteristics of whole stabilised systems, and of the particle size distributions produced by various disaggregation procedures from samples taken wholly from within unpulverised lumps. (A) /TRRL/

Catalytic cracking of alkanes

Abstract: Alkanes are catalytically cracked employing a catalyst comprising unpromoted calcium oxide or at least one alkaline earth oxide together with a promoting amount of an additional component. BACKGROUND The invention relates to a method for cracking alkanes. Catalytic cracking of various hydrocarbons to provide more valuable or more useful products constitutes a very important part of refining operations. Although many catalytic cracking processes and catalysts are known, catalytic cracking is an area of continuing research in an effort to find new processes and catalysts which are more efficient, more selective to desired products, and more economical. An object of the invention is to crack alkanes. Another object of the invention is to crack alkanes using a catalyst. Still another object of the invention is to provide a catalyst for cracking alkanes. Other objects, aspects and advantages of the invention will be apparent to those skilled in the art upon studying the specification and the appended claims. SUMMARY According to the invention, alkanes are catalytically cracked employing a catalyst comprising unpromoted calcium oxide or at least one alkaline earth oxide together with a promoting amount of an additional component. DETAILED DESCRIPTION OF THE INVENTION Calcium oxide in the unpromoted form was found to be an effective catalyst for cracking alkanes. However, all the alkaline earth oxides, namely the oxides of magnesium, calcium, strontium and barium, are useful in this invention when used together with a promoting amount of an additional component. Oxides of magnesium and calcium are especially useful, although it is within the scope of the invention to include oxides of strontium and barium. The latter oxides are not preferred since effective calcination of the hydroxides from which the oxides are normally formed is difficult due to their low melting points and relatively high hydration tendencies. Where more than one promoted alkaline earth oxide is used, the proportion of each alkaline earth oxide in the mixture is not critical and varies widely. Generally where a binary mixture is used, the amount of one alkaline earth oxide will be in the range of from about 0.1 to 50 weight percent and the other in the range of from about 99.9 to 50 weight percent. Three and four component mixtures of alkaline earth metal oxides are also within the scope of the invention. One group of additional components found to be useful in promoting amounts in the present invention are the oxides of the Group VIB metals of the Mendeleef Periodic System. Specifically, the promoting metal oxides are selected from oxides of the group consisting of chromium, molybdenum, and tungsten. Although the precise chemical formula of this promoting species has not been determined, it is believed the oxidation state of the metal in the metal oxide is among the higher oxidation states available. In any event, this promoted form of the catalyst of the invention is the reaction product resulting from admixture of suitable alkaline earth oxides and Group VIB metal oxides under suitable catalyst-forming and catalyst-activating conditions. The amount of promotor used in combination with the alkaline earth oxide varies widely. From 0.1 to 30 parts by weight of Group VIB metal per 100 parts by weight alkaline earth oxide or mixture thereof is generally adequate to produce the desired results. Good results were obtained using from about 1 to 10 parts by weight Group VIB metal oxides in combination with 100 parts by weight of the alkaline earth oxide. In the catalyst preparation, oxides of the alkaline earth metals and the additional component, such as oxides of Group VIB metals, or compounds containing these elements which are convertible to the oxides on calcination, such as hydroxides, nitrates, carbonates, acetates, etc., are combined in any suitable catalyst-forming method. Such methods can include precipitation, coprecipitation, impregnation, dry mixing, wet mixing, and the like. The finished catalysts can be in the form of pellets, pills, agglomerates, powders, etc., depending upon the desired form for use. Before use, the catalyst is generally calcined in air at 400° to 650° C for from several minutes to ten hours or more. Where it is desired to use a catalyst of the invention consisting of one or more of the promoted alkaline earth oxides, the following preparation procedure is useful. A weighed amount of an alkaline earth oxide or an alkaline earth compound convertible to the oxide, such as hydroxide, is dry blended with a weighed amount of another such alkaline earth compound or a promoting amount of an additional component. The blend is then slurried with water after which the water is evaporated. The dried solid is compressed into discs, crushed and sieved to 16 to 60 mesh size. The catalyst is then calcined at approximately 550° C for 2 hours under dry air. Where only unpromoted calcium oxide is used, calcination of the compound as above described is generally desirable before use. Feedstocks capable of being cracked by the catalyst system of this invention include any of the normal cracking feedstocks containing linear or branched alkanes. These can be crude oil fractions or other refinery streams. The desired mixture of products will generally determine the selection of feedstock. For example, one feedstock may be more suitable to produce gasoline than another. Any type of reactor normally used in catalytic cracking operations can be used with the catalyst system of this invention. for example, fixed bed, fluidized bed, trickle bed, etc., reactors can be employed, though high velocity fluidized bed reactors are usually used in commercial processes. Conditions for the catalytic cracking reaction are highly dependent upon the feedstock and desired products, Temperatures will normally range from 550° to 725° C, though temperatures from 600° to 675° C have produced good results. Space velocity of the feedstock is dependent to a large extent upon the specific conditions of the reaction, such as feedstock, temperature, diluent, desired products, etc., but a space velocity sufficient to provide a contact time of from 0.1 to 50 seconds is generally desirable. Pressures are ordinarily near atmospheric, but pressures in the range of from 0 to 200 psig can be used. It may be desirable in some cases to employ a diluent. Inert diluents, such as nitrogen or helium gases can be used or it may be advantageous to use active gases, such as hydrogen or oxygen to control dehydrogenation, coke formation, product distribution, etc. It is often advantageous to periodically regenerate the catalyst bed by any suitable means, such as treatment with dry air at elevated temperatures. Such regeneration generally removes deposits of coke which is formed in varying amounts during the cracking reaction. EXAMPLES The reactor used in the following examples was a continuous flow reactor consisting of a vertical quartz tube 1.4 cm inside diameter by 27 cm long with a total volume of 46 cc. A small diameter tube positioned in the center of the large tube contained thermocouples. The lower portion of the tube, 30 cc of volume or approximately 17 cm of length, was used for both the preheating zone and catalytic zone. After the top of the reactor was removed, a mixture of catalyst and quartz chips consisting of an equal volume of each was added to the reactor for the catalyst zone. Then an amount of quartz chips equal in volume to the above mixture was added to the reactor and thus positioned on top of the mixture to function as the preheating zone. The top of the reactor was replaced, and the feed was passed through the reactor from top to bottom. Helium was used as the carrier gas at flow rates generally in the range 45-55 cc/min at standard conditions of temperature and pressure. A gaseous hydrocarbon feed, such as n-butane, was added to the carrier steam at a constant rate. A liquid hydrocarbon feed, such as n-heptane, was added to the carrier stream by bubbling the carrier stream through the liquid prior to entering the reactor. Partial pressures of hydrocarbons in the carrier were determined using flow rates, temperatures, etc. Unless otherwise noted in the following examples, the partial pressure of n-butane in the system was from 31 to 34 torr and that of n-heptane was 45 to 46 torr. Reaction products and amounts thereof were determined by gas-liquid chromatography. The distribution of reaction products produced in the following examples was fairly constant. A typical distribution of products obtained by cracking n-butane is as follows: ______________________________________ Product Weight Percent______________________________________Methane 25-40Ethane and 25-40 ethylenePropane and 15-30 propyleneCarbon dioxide O-25______________________________________ However, the conversion of the feed varied with the catalyst system employed, and therefore the operability of the invention is illustrated by conversion data.

Non-combustible molding material

Abstract: A non-combustible molding material is produced from (a) a hydraulic inorganic mixture consisting of an inorganic substance composed predominantly of silica and an inorganic substance predominantly of calcium oxide, (b) mineral fibers, and (c) a substance selected from the group consisting bitumen, crystalline aluminum oxide, sulfur, metal sulfide and vanadum oxide. A non-combustible molded article having superior flexural strength and low water absorption can be prepared using said material.

Process for manufacturing calcium-sodium-phosphate consisting mainly of Rhenanit and suitable for use as supplementary animal food

Abstract: Calcium-sodium-phosphates suitable for animal feed use are produced by heating a granulated mixture containing 1.75 to 2.25 moles calcium oxide and 1.25 to 0.75 moles sodium oxide per mole of P2 O5 for at least 10 minutes to between 600° to 1,000°C, while being subjected to vigorous movement and cooling to room temperature.

Process for treating borocalcic ores

Abstract: Borax is produced by reacting carbon dioxide, sea water and boracalcic minerals. One embodiment includes the steps of producing borax by reacting carbon dioxide, sea water and a slurry of crude or beneficiated borocalcic ores in the presence of ammonia and the step of reacting calcined and slaked calcium oxide and ammonium chloride in water solution to produce calcium chloride.

Sand-lime bricks with improved compression strengths - produced by addn. of silicon or silicon alloys

Abstract: Sand-line bricks are produced by pressing a mixt. contng. silica and calcium oxide with water and steam-hardening, part of the silica being replaced by Si or Si-alloys which is produced by electro-thermal treatment of dust from SiO2 reduction-oven exhausts. The additives imparting improved compression strengths.

Cold weather lime stabilization

Abstract: In recent years, lime stabilization of poor quality subgrade soils to upgrade quality or provide acceptable subbase material has increased in popularity as a construction alternative. However, in many situations, specifications relative to cutoff dates for lime stabilization construction have rendered the alternative unfeasible. Previous studies have revealed that soil-lime mixtures cured prior to subjection to freeze-thaw conditions undergo autogenous healing that resulted in continued strength gain. The purpose of this study was not to evaluate the ramifications of autogenous healing of soil-lime mixtures but to evaluate the behavior of soil-lime mixtures subjected to cold weather stabilization. The basic premise involved in this study was that soil-lime mixtures subjected to freeze-thaw conditions immediately after compaction would not undergo pazzolanic reactions until favorable curing conditions were attained. Soil-lime reaction that would not occur during cold weather treatment would then be renewed under favorable conditions to produce latent strength gains. The scope of this study involved the investigation of the behavior of only one soil subjected to cold weather lime stabilization. The selected soil was evaluated at only one lime content, which was established as the stabilization lime content for that soil.

Method of decomposing calcium carbonate

Abstract: The method consists of decomposing calcium carbonate into carbon dioxide gas and calcium oxide under the effects of an ionizing radiation dose at a minimum power of absorbed radiation equal to 0.5 Mrad/s. The advantageous feature of the method resides in that it takes much less time to occur, viz., a few minutes and even seconds rather than several scores of hours, and requires no vacuum to occur.

Recovery of rare-earth alloy particles from calcium-containing product using aqueous ammonium chloride

Abstract: An aqueous solution of ammonium chloride is admixed with a material comprised of calcium hydroxide, calcium oxide and rare earth alloy particles The ammonium chloride reacts with and dissolves the calcium hydroxide and oxide and has no significant effect on the rare earth alloy particles which have useful magnetic properties

Method of producing gaseous mixture rich in hydrogen

Abstract: A gaseous mixture rich in hydrogen is prepared by catalytic partial oxidation of hydrocarbons at a temperature of higher than 850°C in the presence of a catalyst containing 10 to 60% by weight of calcium oxide and 40 to 90% by weight of aluminum oxide.

Process for production of magnesium

Abstract: Magnesium is produced from a mixture of magnesium oxide and calcium oxide by blending the mixture with silicon or ferrosilicon and shaping the blend in the form of briquets, heating the briquets in an inert atmosphere under temperature and pressure conditions capable of substantially inhibiting formation of magnesium vapor, said temperature being not lower than the melting point of calcium-silicon alloy, and thereby producing calcium-silicon alloy within said briquets and subsequently heating the briquets for thereby reducing magnesium oxide.

Study on Over-Based Sulfurized Calcium Phenate Homologs (Part 1)

Abstract: Eighteen samples of over-based sulfurized calcium phenates containing from about 150 to 1, 000% of the theoretical amount of calcium were prepared from p-octylphenol, calcium oxide, elemental sulfur, ethylene glycol, carbon dioxide, lauryl alcohol and oil used as starting materials, and their structure, composition and physical properties were studied.From the ebullioscopic results, the active ingredients of these over-based phenates proved to be amphipathic substances having a polymer structure. Based on the material balance, it was revealed that these ingredients consisted of four ligand components (p-octylphenol, sulfur, ethylene glycol and carbon dioxide) and calcium, and there existed among their components continuous quantitative relationships, e. g. a decrease, in a hyperbolic manner, in the molar ratio of the total ligands to calcium in the products with an increase in the blending-molar ratio of calcium to poctylphenol.In conclusion, these over-based phenates seem to be oil solutions of mixed homologs of an amphipathic coordination-condensation polymer homologous series.

Method of producing a non-combustible molding material

Abstract: A non-combustible moulding material is produced from (a) a hydraulic inorganic mixture consisting of an inorganic substance composed predominantly of silica and an inorganic substance predominantly of a source of calcium oxide, (b) mineral fibers, and (c) a substance selected from the group consisting bitumen, crystalline aluminum oxide, sulfur, metal sulfide and vanadum oxide. A non-combustible molded article having superior flexural strength and low water absorption can be prepared using said material.

Process for the production of hydrogen fluoride, phosphoric anhydride, calcium polyphosphates and nitric acid

Abstract: A process for the production of hydrogen fluoride, phosphoric anhydride, calcium polyphosphates and nitric acid, is disclosed, characterized in that natural phosphate is heated by a plasma stream of working gas in the presence of water vapors to form hydrogen fluoride which is recovered as a commercial product. Then the thus defluorinated phosphate is further heated by an air plasma stream having a bulk temperature of at least 3,500° K. and containing nitrogen oxides. Under such conditions, the defluorinated phosphate decomposes to form phosphoric anhydride and calcium oxide. The gas stream carrying the phosphoric anhydride, the calcium oxide and the nitrogen oxides is cooled down to yield, as commercial products, either phosphoric anhydride and nitric acid, or calcium polyphosphates containing up to 70% P2 O5 and nitric acid, or else all of the three products, depending on the cooling conditions. The advantages of the proposed process are as follows: High rate of the process, High concentration of hydrogen fluoride in the gas, and The possibility of simultaneously producing a range of products from cheap raw material while avoiding the use of other commercial products as feedstock for the process.

Hot pressing of reaction sintered CaB6

Abstract: A method for the production of high density compacts of calcium hexaborideomprising the gradual heating of stoichiometric quantities of calcium oxide and boron powder to a temperature of approximately 1500° C and maintaining that temperature for a period of about 30 minutes to produce calcium hexaboride, applying a pressure of about 5500 psi, and maintaining both temperatures and pressures for about 90 minutes.

Process for the recovery of tantalum and niobium and other metals from tin slag

Abstract: Aluminum oxide or calcium oxide is added to tin slag, which contains a relatively high silica content along with a source of carbon, and the mixture is fused. The added aluminum oxide or calcium oxide combines with the silicon oxide and other metallic compositions present to form a slag phase of a new compositiom which has a melting point 100* - 400* C. higher than the original slag composition. In the fusion the carbon reduces the tantalum and niobium and other oxides to the respective metals and the higher melting range of the new slag composition results in super heating of the metal alloy which facilitates a more effective ultimate separation of the metal alloy.

Method of removing slag incrustations containing calcium oxide

Abstract: Residual slag incrustations containing calcium oxide are removed from a surface in the presence of which molten iron has been desulfurized by contacting said incrustations with a source of an oxide of boron.