Hydrogen product purity

Keywords Transalkylation, Selective naphthene cracking, Aromatics hydrogenation, Product purity... 

The purge gas is burned as fuel in the primary reformer furnace, reducing the total fuel requirement for the reformer. Additional hydrogen must be produced to account for the purge gas loss and this increases the feed rate and the size of the reformer furnace. Nevertheless, the overall economics of the PSA unit, due in part to more efficient heat recovery, are superior to the conventional process with the low temperature shift and methanation reactors. Also, because the PSA unit removes all of the methane and carbon oxides from the hydrogen product, the operation of the reformer is independent of hydrogen product purity and, thus, can be operated at optimum conditions [4]. 

The hydrogen product obtained has a purity between 97 and 99.9 volume %. The balance is methane, and the by-product of the process is CO2. 

Other Reactions. Primary amyl alcohols can be halogenated to the corresponding chlorides by reaction with hydrogen chloride in hexamethylphosphoramide (87). Neopentyl chloride [753-89-9] is formed without contamination by rearrangement products. A convenient method for preparing / f/-amyl bromide and iodide involves reaction of / f/-amyl alcohol with hydrobromic or hydroiodic acid in the presence of Li or Ca haUde (88). The metal haUdes increase the yields (85 —95%) and product purity. 

Note that the yield of extract product presented here is lower than that reported earlier in Table 4 because the hydrogenated products were not extracted with NMP but were centrifuged directly. The data show that centrifugation by itself, and without any accompanying filtration, appears to provide pitches of acceptable purity, albeit with an associated lower yield. 

The stereoisomers of olefin saturation are often those derived by cis addition of hydrogen to the least hindered side of the molecule (99). But there are many exceptions and complications (97), among which is the difficulty of determining which side of the molecule is the least hindered. Double-bond isomerization frequently occurs, and the hydrogenation product is the resultant of a number of competing reactions. Experimentally, stereochemistry has been found to vary, sometimes to a marked degree, with olefin purity, reaction parameters, solvent, and catalyst 30,100). Generalizing, it is expedient, when unwanted products arise as a result of prior isomerization, to avoid those catalysts and conditions that are known to favor isomerization. 

The catalytic performances obtained during transalkylation of toluene and 1,2,4-trimethylbenzene at 50 50 wt/wt composition over a single catalyst Pt/Z12 and a dualbed catalyst Pt/Z 121 HB are shown in Table 1. As expected, the presence of Pt tends to catalyze hydrogenation of coke precursors and aromatic species to yield undesirable naphthenes (N6 and N7) side products, such as cyclohexane (CH), methylcyclopentane (MCP), methylcyclohexane (MCH), and dimethylcyclopentane (DMCP), which deteriorates the benzene product purity. The product purity of benzene separated in typical benzene distillation towers, commonly termed as simulated benzene purity , can be estimated from the compositions of reactor effluent, such that [3] ... 

As only small amounts of the hydrogenation products underwent spontaneous cyclization, the compounds were heated in a sealed vessel under microwave irradiation. Due to the low solubility of the cyclized products at room temperature, they precipitated upon cooling and could be easily collected by filtration. The desired dihydropteridinones were obtained in high purity and could be readily used to generate a more diverse library by subsequent N-alkylation [92],... 

The feed gas is introduced at the high adsorption pressure in the adsorption step, impurities are adsorbed on the internal surfaces of the adsorbent leaving high-purity hydrogen product gas in the void spaces of the vessel, and high-purity hydrogen is withdrawn continuously as product from the top of the vessel under pressure. The gas flow is normally... 

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