Hydrogen transfer index

HYDROGEN TRANSFER INDEX (HTI1 TEST In this test, 0.5 /xL pulses of 1-hexene feed were carried from a heated sampling valve into a fixed-catalyst bed in a stainless steel reactor by a nitrogen carrier stream at 800 mL/min. (at STP). The catalyst was -250 mesh and diluted with alumina of the same mesh size plus 80-100 mesh acid-washed Alundum. Reactor pressure was controlled by an Annin valve. The effluent stream went to the injector splitter of a gas chromatograph. The reactor conditions included a catalyst temperature of 221°C and 3.45 MPa total pressure. 

Besides feed properties and operational variables, the type of catalyst has a profound effect on hnal olehns level in the gasoline prodnct. Catalysis with better metal tolerance, especially to nickel and vanadium, are most suitable for olehn reduction. Catalyst capacity to saturate olehns and to form corresponding paraffins depend upon the hydrogen transfer index (HTI). 

The hydrothermal deactivation of Y zeolite containing 0, 4, 7 and 12 wt.% of REO and its effects on catalytic activity, stability and selectivity were investigated. The Y zeolites were hydrothermally deactivated at 788°C in three consecutive cycles of two hours each. The fresh and deactivated zeolites were characterized by measuring Unit Cell Size (UCS) and surface area. The acidic properties were measured by the Temperature Programmed Desorption (TPD) of ammonia and IR-pyridine desorption. In order to correlate structural, textural and acid properties with catalytic behavior, the zeolites were evaluated in the conversion of cyclohexane. The Hydrogen Transfer Index (HTI) measured as a ratio of paraffins to olefins is a parameter of the selectivity. It was found that the REO was incorporated into zeolite structure up to high concentrations modifying to some extent XRD deflection, the acidic properties and the HTI ratio. After deactivation, the acidity and HTI were diminished and the Lewis/Bronsted acid ratio was modified. HTI decreased as REO concentration increased. 

Chromatograph was used. The Hydrogen Transfer Index (HTI) measured as ratio of paraffins and olefins was a parameter of selectivity. 

The cyclohexene conversion to paraffins and olefins which is well known as the Hydrogen Transfer Index (HTl) ratio was used to evaluate the catalytic activity of the fi sh and deactivated materials at constant conversion (30 mol %) varying the contact time and at 250°C. The HTl results were related with the REO content, cell parameter and total acidity and are plotted in figures 5,6 and 7, respectively. 

Relative hydrogen transfer activity can be determined using an HTI test (11), where the index is a measure of the degree of saturation in the reaction product. The test determines the product ratio of 3-methylpentenes to 3-methylpentane derived from a 1-hexene feed. While the branched products come mainly from oligomerization followed by cracking, the results should be relevant here as well. The higher the index, the lower the relative hydrogen transfer activity. 

Density differences (Fig. 7) once more qualitatively show an asynchronous transition state with the Cu-O bond breaking/O-Si bond formation being more advanced compared to the hydrogen transfer toward the Cu atom. Wiberg indexes (Table 7) confirm this asynchronicity, although it being less pronounced compared to the previous steps (Sy = 0.90-0.95). At the TS, the Si-H and Cu-O bonds are broken at approximately 75 and 85 %, while almost 85 % of the Si-O bond has been formed. The Cu-H bond has only been formed up to about 60-65 %. SB ay... 

Tables 2,3, and 4 outline many of the physical and thermodynamic properties ofpara- and normal hydrogen in the sohd, hquid, and gaseous states, respectively. Extensive tabulations of all the thermodynamic and transport properties hsted in these tables from the triple point to 3000 K and at 0.01—100 MPa (1—14,500 psi) are available (5,39). Additional properties, including accommodation coefficients, thermal diffusivity, virial coefficients, index of refraction, Joule-Thorns on coefficients, Prandti numbers, vapor pressures, infrared absorption, and heat transfer and thermal transpiration parameters are also available (5,40). Thermodynamic properties for hydrogen at 300—20,000 K and 10 Pa to 10.4 MPa (lO " -103 atm) (41) and transport properties at 1,000—30,000 K and 0.1—3.0 MPa (1—30 atm) (42) have been compiled. Enthalpy—entropy tabulations for hydrogen over the range 3—100,000 K and 0.001—101.3 MPa (0.01—1000 atm) have been made (43). Many physical properties for the other isotopes of hydrogen (deuterium and tritium) have also been compiled (44).

The general or universal effects in intermolecular interactions are determined by the electronic polarizability of solvent (refraction index n0) and the molecular polarity (which results from the reorientation of solvent dipoles in solution) described by dielectric constant z. These parameters describe collective effects in solvate s shell. In contrast, specific interactions are produced by one or few neighboring molecules, and are determined by the specific chemical properties of both the solute and the solvent. Specific effects can be due to hydrogen bonding, preferential solvation, acid-base chemistry, or charge transfer interactions. 

Figure 2.29. Detail of photosystem I, seen from the side, with the division between units A and B (see Fig. 2.27) in the middle. Chlorophyll molecules (chi) other than the six central ones involved in transfer of energy to the three Fe4S4 clusters (FeS) are omitted. Chlorophylls, phylloquinones (phy, also known as vitamin K) and iron-sulphur clusters are further indexed with the subimit label A, B or X (cf. Fig. 2.27), and the chlorophylls are shown with an index number 1 to 3. Other identified molecules include LHG (CggHygOjoP), LMG (C45H84OJQ) and a number of p-carotenes (BCR). The scattered dots are oxygen atoms of water molecules (no hydrogens are shown). Based on Protein Data Bank ID IJBO Jordan et ah, 2001).

An essential difference is observed for the chain transfer with hydrogen in the polymerization on bulk TiClj (the chain transfer is 0.5th order with respect to [Hj]) and on catalysts supported on MgClj (first — order chain transfer with respect to [Hj]). This difference leads to higher values of the melt index of polyethylene prepared on the TiClyMgClj catalyst in the presence of H in comparison with non-supported titanium chloride catalysts... 

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