Hydrogen/hydrocarbon separation

Dong J, Lin YS, and Liu W. Multicomponent hydrogen/hydrocarbon separation by MFI-type zeolite membranes. AIChE J 2000 46(10) 1957-1966. 

Trowbridge, L.D. Application of inorganic membrane technology to hydrogen-hydrocarbon separations. ORNL/TM-2003/139, June 2003. 

The use of silver fluoroborate as a catalyst or reagent often depends on the precipitation of a silver haUde. Thus the silver ion abstracts a CU from a rhodium chloride complex, ((CgH )2As)2(CO)RhCl, yielding the cationic rhodium fluoroborate [30935-54-7] hydrogenation catalyst (99). The complexing tendency of olefins for AgBF has led to the development of chemisorption methods for ethylene separation (100,101). Copper(I) fluoroborate [14708-11-3] also forms complexes with olefins hydrocarbon separations are effected by similar means (102). 

Conventional polymeric hydrogen separation membranes yield hydrogen at low pressure. Air Products and Chemicals has demonstrated a carbon membrane on an alumina support that removes hydrocarbons from hydrogen/hydrocarbon mixtures and leaves the hydrogen at high pressure40. 

Molten copper absorbs hydrogen9 and sulphur dioxide,10 the occluded gases being eliminated on cooling. The liquid metal does not absorb nitrogen. It combines with oxygen to form cuprous oxide, so that fall of temperature is not attended by evolution of the gas. It decomposes hydrocarbons such as methane and ethane, with occlusion of hydrogen and separation of carbon. 

The products from these hydrogenations were separated into gases (analyzed by G.C.), water (analysed by azeotropic distillation), insolubles (CH2CI2 insolubles), asphaltene (CH2CI2 soluble/X4 insoluble) (Shell X4 40-60 C b.p. light petroleum), oils (CH2CI2 soluble/X4 soluble). Hydrogen transferred from the donor solvent was determined by G.L.C. analysis of the ratio of tetralin to naphthalene in the total hydrocarbon liquid product. 

Coal Liquefaction, Steam is used to produce hydrogen for the liquefaction of coal. In the liquefaction process, coal is crushed, dried, pulverized, and then added to a solvent to produce a slurry. The slurry is heated, usually in the presence of hydrogen to dissolve the coal. The extract is cooled to remove hydrogen, hydrocarbon gases, and hydrogen sulfide. The liquid is then flashed at low pressure to separate condensable vapors from the extract. Mineral matter and organic soHds are separated and used to produce hydrogen for the process. The extract may be desulfurized. The solvent is separated from the products. There are at least six different liquefaction processes (see Coal conversion process, liquefaction Fuels, synthetic-liquid fuels). 

Combinations of high separation factors (> 50) and reasonable permeance interesting for practical applications have been realised for gas separation on small surface areas with microporous membranes. These are discussed in Chapter 9 on transport properties and particularly concern the separation of hydrogen and CO2 from each other and from hydrocarbons as well as some hydrocarbon separations. 

After the treated feedstock leaves the first stage, it is sent to a hydrocarbon separator where the treated feedstock is separated and the hydrogen is recycled to the first-stage feedstock. The treated feedstock is charged to a fractionator and depending on the products desired (gasoline components, jet fuel, and gas oil), the fractionator is operated to selectively separate part of the first stage reactor effluent. 

Cioslowski and Mixon [57] reported atomic interaction lines connecting hydrogen atoms separated by short distances ( /h -h < 2.18 A) in several polycyclic aromatic hydrocarbons (PAHs). These authors describe this interaction as... 

The molecule of 15,23 16,22-dimethenobenzo[l,2-iZ 4,5-fl ]dipentha-phene (C48H24, Figure 2), also known as kekulene or superbenzene, was studied at both the HF/STO-3G and HF/6-31G levels. The optimized geometry was found to be planar and have D f, symmetry, with the six inner hydrogen atoms separated by only 1.851 A. In addition, structures of five other ben-zenoid hydrocarbons (anthracene, phenanthrene, tetracene, benzanthracene, and chrysene) were optimized. The corresponding total energies were found to... 

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