Hydrogen partial pressure

Thermolysis of H S was carried out in an open tubular reactor quartz tube with argon/HjS feed over a wide composition spectium (20-100% H S) at four temperatures (1030-1070 K). These experiments show that the reaction is essentially first order in H S partial pressure. Hydrogen yield also increases monotoiucally with feed composition at all temperatures (Adesina et al., 1995). 

At higher temperature and partial pressure, hydrogen is always soluble to a minor extent in construction steels. For this reason it is advisable not to cool vessels too rapidly when taking them out of service, and to hold them at atmospheric pressure for some hours at 300 °C so that the hydrogen can largely diffuse out (soaking). In contrast to the hydrogen attack described above this phenomenon is reversible. 

Partial pressure of benzene Initial benzene partial pressure Hydrogen partial pressure Free radical... 

For the 500 pm thick membrane, the thickest membrane employed, data falls fairly well on the Sieverts Law line, which is interpreted as implying that bulk diffusion of dissociated hydrogen is the rate limiting step. Experimentally measured permeability for the 500 pm membrane was 3.2 x 10 mol m" s" Pa" . As the higher feed pressures were approached (13.1 bar partial pressure hydrogen, 34 bar total pressure with heUum), some deviations from Sieverts Law were observed. These are attributed to gas phase diffusion limitations, as discussed below. 

The effect on catalyst activity of process variables such as LHSV, temperature, hydrogen partial pressure, hydrogen sulfide partial pressure and gas/oil ratio can be predicted by a suitable kinetic expression. It was found that the expression shown in equation 1 could be used to describe the kinetics of CoMo and NiMo catalysts for very deep desulfurization of diesel. ... 

Improving the cetane number as well as lowering the aromatics content requires higher partial pressures as well as higher hydrogen consumption. 

Relationship between the residual aromatics content, the hydrogen partial pressure, and the chemical hydrogen consumption (for a SR gas oil). 

Facilitated transport membranes can be used to separate gases membrane transport is then driven by a difference in the gas partial pressure across the membrane. Metal ions can also be selectively transported across a membrane driven by a flow of hydrogen or hydroxyl ions in the other direction. This process is sometimes called coupled transport. 

The rate of hydroformylation increases with increasing hydrogen and decreases with increasing carbon monoxide partial pressures (9), suggesting that rates of hydroformylation would be satisfactory at high H2 and low CO partial pressures. In industrial practice, however, high pressures of both H2 and CO ate required in order to stabilize the HCo(CO)4 catalyst at the temperatures necessary for practical rates (10). Commercial processes, for example, operate at >24 MPa (3480 psi) and >140 C. 

Ru(1PP)2(00)2, at 2000 ppm mthenium and 1-hexene as substrate, gives only an 86% conversion and a 2.4 1 linear-to-branched aldehyde isomer ratio. At higher temperatures reduced conversions occur. High hydrogen partial pressures increase the reaction rate, but at the expense of increased hydrogenation to hexane. Excess triphenylphosphine improves the selectivity to linear aldehyde, but at the expense of a drastic decrease in rate. 

Conditions cited for Rh on alumina hydrogenation of MDA are much less severe, 117 °C and 760 kPA (110 psi) (26). With 550 kPa (80 psi) ammonia partial pressure present ia the hydrogenation of twice-distilled MDA employing 2-propanol solvent at 121°C and 1.3 MPa (190 psi) total pressure, the supported Rh catalyst could be extensively reused (27). Medium pressure (3.9 MPa = 566 psi) and temperature (80°C) hydrogenation usiag iridium yields low trans trans isomer MDCHA (28). Improved selectivity to aUcychc diamine from MDA has been claimed (29) for alumina-supported iridium and rhodium by iatroduciag the tertiary amines l,4-diazabicyclo[2.2.2]octane [280-57-9] and quiaucHdine [100-76-5]. 

Reductive alkylations and aminations requite pressure-rated reaction vessels and hiUy contained and blanketed support equipment. Nitrile hydrogenations are similar in thein requirements. Arylamine hydrogenations have historically required very high pressure vessel materials of constmction. A nominal breakpoint of 8 MPa (- 1200 psi) requites yet heavier wall constmction and correspondingly more expensive hydrogen pressurization. Heat transfer must be adequate, for the heat of reaction in arylamine ring reduction is - 50 kJ/mol (12 kcal/mol) (59). Solvents employed to maintain catalyst activity and improve heat-transfer efficiency reduce effective hydrogen partial pressures and requite fractionation from product and recycle to prove cost-effective. 

Reactant. Steam can behave as an oxidant. The partial pressure of oxygen generated by the dissociation of steam into hydrogen and oxygen is shown in Figure 17. 

The Phillips Steam Active Reforming (STAR) process catalyticaHy converts isobutane to isobutylene. The reaction is carried out with steam in tubes that are packed with catalyst and located in a furnace. The catalyst is a soHd, particulate noble metal. The presence of steam diluent reduces the partial pressure of the hydrocarbons and hydrogen present, thus shifting the equHibrium conditions for this system toward greater conversions. 

SolubiHty of carbon dioxide in ethanolamines is affected by temperature, amine solution strength, and carbon dioxide partial pressure. Information on the performance of amines is available in the Hterature and from amine manufacturers. Values for the solubiHty of carbon dioxide and hydrogen sulfide mixtures in monoethanolamine and for the solubiHty of carbon dioxide in diethanolamine are given (36,37). SolubiHty of carbon dioxide in monoethanolamine is provided (38). The effects of catalysts have been studied to improve the activity of amines and provide absorption data for carbon dioxide in both mono- and diethanolamine solutions with and without sodium arsenite as a catalyst (39). Absorption kinetics over a range of contact times for carbon dioxide in monoethanolamine have also been investigated (40). 

---