Hydrogen aspects

In the European Union, there are no explicit research activities dedicated to nuclear hydrogen production. Respective research programs are either concentrating on the nuclear or on the hydrogen aspects. There is, however, a little overlap of both areas in such a way that research on irmovative nuclear reactor designs also takes into consideration one of their most pronounced features, which is the possibility of penetration of the non-electricity market with H2 production as a major issue. On the other hand, research projects which deal with large-scale H2 production methods of the future, may also include the option of nuclear power to provide the required primary energy. 

Abstract In this chapter, recent progress on palladium (Pd)-based membrane reactors (MRs) is outUned concentrating, in particular, on the production of pure hydrogen. Aspects of many reactions, as well as analysis of both the Pd-based and the amorphous membranes under study, and the governing equations are presented. Some critical aspects of non-Pd-based membranes are also discussed. All the preparation techniques for pure, alloyed, amorphous, non-Pd-based membranes used in MRs are briefly summarized and compared. Moreover, some problems related to the effect of contamination of the Pd-based membranes on the H2 flux are discussed. 

Another aspect of my early research in Budapest was in nitration chemistry, specifically the preparation of nitronium tetrafluoroborate, a stable nitronium salt. 1 was able to prepare the salt in a simple and efficient way from nitric acid, hydrogen fluoride, and boron trifluoride. 

Secondary structure refers to the shape of the molecule as a whole, particularly to those aspects of structure which are stabilized by intramolecular hydrogen bonds. 

Incorporation of OH is another critical aspect of the oxidation chemistry. Reduction to the ppb level is necessary for the manufacture of low loss optical fiber. Hydrogen is iacorporated iato the glass according to the reaction... 

Economic Aspects. Pertinent statistics on the U.S. production and consumption of fluorspar are given in Table 4. For many years the United States has rehed on imports for more than 80% of fluorspar needs. The principal sources are Mexico, China, and the Repubflc of South Africa. Imports from Mexico have declined in part because Mexican export regulations favor domestic conversion of fluorspar to hydrogen fluoride for export to the United States. 

The complex nature of coal as a molecular entity (2,3,24,25,35,37,53) has resulted ia the chemical explanations of coal combustion being confined to the carbon ia the system. The hydrogen and other elements have received much less attention but the system is extremely complex and the heteroatoms, eg, nitrogen, oxygen, and sulfur, exert an influence on the combustion. It is this latter that influences environmental aspects. 

In addition to these mechanical problems there are two aspects of the compression process which relate specifically to ethylene. Eirst, there is a tendency for small amounts of low molecular weight polymer to be formed and, second, the gas may decompose into carbon, hydrogen, and methane if it becomes overheated during compression. Cavities in which the gas can collect and form polymer, which hardens with time or in which the gas can become hot, need to be avoided. 

One of the principal aspects of refinery gas cleanup is the removal of acid gas constituents, ie, carbon dioxide, CO2, and hydrogen sulfide, H2S. Treatment of natural gas to remove the acid gas constituents is most often accompHshed by contacting the natural gas with an alkaline solution. The most commonly used treating solutions are aqueous solutions of the ethanolamines or alkah carbonates. There are several hydrogen sulfide removal processes (29), most of which are followed by a Claus plant that produces elemental sulfur from the hydrogen sulfide. 

An important aspect of this procedure is the use of latent acid catalysts, such as phenyl hydrogen maleate, phenyl trifluoracetate, and butadiene sulfone. These catalysts reduce the peak exotherm from over 200°C to 130—160°C. The resin catalyst mixture has a working life of up to several days at RT. The elevated temperature of mol ding these latent catalysts generates the corresponding acids, namely, maleic, trifluoracetic, and phenolsulfonic, which cataly2e the resole reaction. Typically, a cycle time of 1—2 min is requited for a mold temperature of - 150° C. 

Economic Aspects. Most hydrogen sulfide is made and used captively or sold by pipeline at prices which are highly variable, depending on locahty. Production ia the United States exceeds 1.1 X 10 t/yr-It has been estimated that 2.4 x 10 t/yr of sulfur are recovered from H2S-containing refinery streams and 1.8 x 10 t/yr of sulfur are recovered from H S-containing natural gas (120). 

Health nd Safety Factors. Thionyl chloride is a reactive acid chloride which can cause severe bums to the skin and eyes and acute respiratory tract injury upon vapor inhalation. The hydrolysis products, ie, hydrogen chloride and sulfur dioxide, are beheved to be the primary irritants. Depending on the extent of inhalation exposure, symptoms can range from coughing to pulmonary edema (182). The LC q (rat, inhalation) is 500 ppm (1 h), the DOT label is Corrosive, Poison, and the OSHA PEL is 1 ppm (183). The safety aspects of lithium batteries (qv) containing thionyl chloride have been reviewed (184,185). 

Production and Economic Aspects. Thallium is obtained commercially as a by-product in the roasting of zinc, copper, and lead ores. The thallium is collected in the flue dust in the form of oxide or sulfate with other by-product metals, eg, cadmium, indium, germanium, selenium, and tellurium. The thallium content of the flue dust is low and further enrichment steps are required. If the thallium compounds present are soluble, ie, as oxides or sulfates, direct leaching with water or dilute acid separates them from the other insoluble metals. Otherwise, the thallium compound is solubilized with oxidizing roasts, by sulfatization, or by treatment with alkaU. The thallium precipitates from these solutions as thaUium(I) chloride [7791 -12-0]. Electrolysis of the thaUium(I) sulfate [7446-18-6] solution affords thallium metal in high purity (5,6). The sulfate solution must be acidified with sulfuric acid to avoid cathodic separation of zinc and anodic deposition of thaUium(III) oxide [1314-32-5]. The metal deposited on the cathode is removed, kneaded into lumps, and dried. It is then compressed into blocks, melted under hydrogen, and cast into sticks. 

The experimental and theoretical aspects of the radiation and self-induced conversion kinetics and equiUbria between the ortho and para forms of hydrogen, deuterium, and tritium have been correlated (17). In general, the radiation-induced transitions are faster than the self-induced transitions. 

The addition of hydrogen halides to alkenes has been studied from a mechanistic point of view over a period of many years. One of the first aspects of the mechanism to be established was its regioselectivity, that is, the direction of addition. A reaction is described as regioselective if an unsymmetrical alkene gives a predominance of one of the two possible addition products the term regiospecific is used if one product is formed... 

Fluorides and dust are emitted to the air from the fertilizer plant. All aspects of phosphate rock processing and finished product handling generate dust, from grinders and pulverizers, pneumatic conveyors, and screens. The mixer/reactors and dens produce fumes that contain silicon tetrafluoride and hydrogen fluoride. A sulfuric acid plant has two principal air emissions sulfur dioxide and acid mist. If pyrite ore is roasted, there will also be particulates in air emissions that may contain heavy metals such as cadmium, mercury, and lead. 

---