Catalytic cracking performance of alkaline-treated zeolite Beta in the terms of acid sites properties and their accessibility

The zeolite Beta is considered as a promising additive for FCC catalyst in diesel oil production. In this article, it is shown that hierarchical zeolite Beta obtained by an optimized desilication procedure increases diesel and propylene yields during gas oil cracking reaction. The alkaline treatment of zeolite Beta (Si/Al = 22) by desilication with NaOH and NaOH&TBAOH was investigated. The catalytic performance improvement of desilicated zeolite Beta has been rationalized by deep characterization of the samples including X-ray diffraction, low-temperature adsorption of nitrogen, solid-state 29Si MAS NMR and IR studies of acidity. Finally, the catalytic performance of the zeolites Beta was evaluated in the cracking of n-decane, 1,3,5-tri-iso-propylbenzene, and vacuum gas oil. It was found that desilication with NaOH&TBAOH ensures the more uniform intracrystalline mesoporosity with the formation of narrower mesopores, while preserving full crystallinity resulting in catalysts with the most appropriated acidity and then with better catalytic performance.Also, M.C.I.L., J.M.T. and F.R. thank financial support from the Spanish Ministry of Economy and Competitiveness through the Severo Ochoa program (SEV-2012-0267) as well as operating grants Consolider Ingenio Multicat (CSD-2009-00050) and MAT-2012-3856-0O2-01.Tarach, K.; Gora-Marek, K.; Tekla, J.; Brylewska, K.; Datka, J.; Mlekodaj, K.; Makowski, W.... (2014). Catalytic cracking performance of alkaline-treated zeolite Beta in the terms of acid sites properties and their accessibility. Journal of Catalysis. 312:46-57. https://doi.org/10.1016/j.jcat.2014.01.009S465731

Decay of /sup 199m, g/Po: isomeric transitions in /sup 199/PO and /sup 199/BI

The M4 isomeric transition (E/sub gamma /-238 keV) of the 13/2/sup +/ state in /sup 199/PO to the 5/2/sup -/ level, with a half life of a 4.17 min, has been observed in mass separated sources. An approximately 72 keV transition in coincidence with the isomeric transition suggests the placement the 5/2/sup -/ level above the 3/2 /sup -/, and when combined with alpha -decay Q values, this results in a placement of the 13/2/sup +/ isomeric state in /sup 195/Pb at approximately 200 keV. The transition rate for the M4 transition in /sup 199/PO is similar to those for other M4 transitions in this region. Contrastingly, a M4 transition in /sup 199/Bi, which is highly likely to occur on the basis of systematics of /sup 1///sub 2//sup +/ and 9/2/sup -/ states and a sequence of gamma rays among low spin states observed in the authors' data, is highly retarded. Although, this M4 transition is not observable in their data, an upper limit for its strength is established at approximately 1/1000 the intensity of typical M4 transitions in this region. Possible interpretations of this retardation are discussed. (23 refs)

Decay properties of /sup 186/Pb and the lead alpha-decay rate anomaly

Alpha-decay transitions between ground states of doubly-even nuclei are taken to represent unhindered decays. Reduced widths for these s-wave transitions behave in a regular fashion as a function of both neutron and atomic number. They are largest for nuclei two or four particles beyond a closed shell (with sharp minima at the shell) and they then decrease as the next closure is approached. The s-wave widths for /sup 186/ /sup 188/ /sup 190/ /sup 192/Pb, however, have been reported to behave anomalously, i.e., they purportedly increase by a factor of 30 between /sup 186/Pb (N = 104) and /sup 192/Ob (N = 110) instead of decreasing as one nears N = 126. Theoretical calculations have not reproduced this unusual behavior. The (electron-capture (EC) + ..beta../sup +/) strengths were deduced from K x-ray intensities. A number of corrections are involved in such determinations. We undertook the investigation of the (EC + ..beta../sup +/) decay schemes of these neutron-deficient lead isotopes, in conjunction with studies of their ..cap alpha..-decay properties, to obtain more reliable ..cap alpha..-branching ratios. Herein we present new information on /sup 186/Pb and discuss the partial ..cap alpha.. half-lives for /sup 192/Pb, /sup 190/Pb, /sup 188/Pb, and /sup 186/Pb together with ..cap alpha..-decay rates for even-even nuclei with Z greater than or equal to 78

Alpha-decay rates of even-even lead isotopes

The alpha -decay rates of /sup 186,188,190,192/Pb have been reported to have an anomalous dependence on neutron number. Theoretical calculations do not reproduce this unusual behavior. To obtain more precise alpha -decay branching ratios, the authors reinvestigated the decay properties of /sup 188,190,192/Pb. Their result in alpha -decay reduced widths whose dependence on N is similar to that observed for other elements. (16 refs)

Energy Levels and Structure of Light Rare-earth Nuclei, /sup 136,138,140/Sm and /sup 132,134,136/Nd, via Beta Decay

Levels in /sup 136,138,140/Sm were populated by the beta decay of Eu, following (HI,pxn) reactions and on-line mass separation. Members of the ..gamma.. band were observed in all three daughter nuclei. Spectroscopic calculations were made using the triaxial rotor model, with all parameters derived microscopically from a Woods-Saxon deformed shell model. Comparison with the data supports the characterization of these nuclei in terms of a triaxial intrinsic shape. Improved decay schemes for /sup 132,134,136/Nd are given. 3 refs., 7 figs

The UNISOR ISOL data acquisition system

The data collection system of the on-line separator at Oak Ridge (UNISOR) is described including an overview of the operation and a discussion of some new techniques. Tape transport and computer based data acquisition systems have been developed which allow several experiments to be performed simultaneously on a given mass chain and also enable experiments to be changed quickly. To make efficient use of the cyclotron beam time, methods have been developed for quickly extracting short-lived side masses from the separator. Also described are an on-line scanning Gerholm lens spectrometer, a multiple time analysis system and an angular correlation station for the tape transport. © 1976

Decays of 117Xe 117I 117 Te

Mass separated 117117I117Te decays were studied on-line by bombarding Pd104 with 86 MeV O16 ions and off-line by bombarding Ag107,109 with 50-70 MeV C12. From gamma ray and x ray singles, half-life, excitation function, and coincidence measurements, 26 gamma rays are assigned to the deccay of Xe117 and 31 gamma rays are assigned to the I117 decay. The half-lives were measured to be 612 sec, 2.22±0.04 min, 62±2 min, and 2.8×0.2 h for Xe117, I117, Te117,, and Sb117, respectively. Eight new levels are deduced in I117 and seven new levels in Te117. From the Kurie plot of the positron spectrum, the QEC(117Xe117I) was determined to be 6.27±0.30 MeV. © 1985 The American Physical Society

On-line mass separator investigation of the new isotope 2.9-sec I116

Using on-line mass separation I116 has been identified and its half-life determined to be 2.91 0.15 sec. The activity was produced by the Rh103(O16, 3n)I116 reaction and by the decay of 57-sec Xe116. The I116 decays primarily to the ground state of Te116 and also to excited states at 678.9 and 1219.1 keV. From positron measurements, a decay energy of QEC=7.710.20 MeV is assigned to I116. rays of 540.2 and 678.9 keV are observed in this decay and are assigned to depopulate levels in Te116 at 1219.1 and 678.9 keV, respectively. The former is a new level with a probable spin-parity of either 2+ or 0+. From the logft values, a spinparity assignment of 1+ is deduced for the ground state of I116, which is interpreted to have a configuration of [(d52)(d32)]. A decay energy of QEC=4.340.20 MeV observed from activity produced by the Pd104 + O16 reaction is assigned to Xe116. NUCLEAR REACTIONS Rh103(O16, 3n), E=83 MeV; Pd104(O16, 4n) and Pd104(O16,p 3n), E=91 MeV. Natural Rh targets and enriched Pd targets. RADIOACTIVITY I116, Xe116; measured E, I, T12(), T12(+), +- coin., + end point; Te116 deduced levels, J, , logft; I116 deduced ground state J, , logft; Ge(Li) detectors and plastic scintillators; mass separated sources. © 1976 The American Physical Society

Rotation-aligned coupling and axial asymmetry in \u3csup\u3e189-195\u3c/sup\u3eAu

Levels in 189, 191, 193Au have been studied by radioactive decay of isotopically separated 189, 191, 193Hg. The systematics of the levels are followed from 195Au to 189Au and show a remarkable insensitivity to neutron number. The h1 1 2 bands are identified and provide a critical test of the model of a single-j nucleon subject to rotation-aligned coupling to an asymmetric core. Within the framework of the model the triaxial degree of freedom appears to be very stable. © 1975

Decay of mass-separated Tl190 and Hg190

Radioactive sources containing Tl190 and Hg190 have been produced and mass separated with the University Isotope Separator on line to the Oak Ridge isochronous cyclotron. Multiscaled spectra of γ rays, x rays, conversion electrons, and positrons were obtained, and γ-γ and γ-x-ray coincidences were measured. Two isomers in Tl190 decay have half-lives of 2.6 ± 0.3 min (2-) and 3.7 ± 0.3 min (7+). From β decay endpoint energies the 7+ and 2- isomers lie within 0.1 MeV of each other, but which is the ground state was not determined. Both isomers have ground-state QEC values of approximately 7 MeV. The 2- level undergoes β decay primarily to the 2+ states at 416.4 and 1099.9 keV in Hg190, while the decay of the 7+ isomer feeds a number of different states with spins ranging from 5 to 9. We observed the 5-, 7-, and 9- members of the previously identified structure of negative-parity states resulting from coupling of a rotation-aligned i132 neutron with 3p32 and 2f52 neutrons. Some additional states having decays consistent with (6-) and (8-) assignments perhaps are candidates for less aligned members of the 13/2+ band coupled with p32 and f52 neutrons. The 20-min Hg190 isotope decays approximately 65% of the time to a level at 171.5 keV, thus making it difficult to study other levels in Au190. Four new states in Au190 were definitely established, while several new ones were suggested by the present work. The populated levels are predominantly low spin and are fairly closely spaced. The logft value for the transition to the 171.5 keV level is 5.7, so it is likely that this state has a spin and parity of 1+. RADIOACTIVITY Tl190, Tlm190, Hg190 [from Ta, W(O16,xp+yn), E=143,124 MeV]; mass-separated radioactivities. Measured T12, Eγ, Iγ, Ice, Eβ, γγ coin, γx coin. Deduced logft, Q. Hg190, Au190 deduced levels, J, π, ICC, Λ. © 1976 The American Physical Society