Ralph H. Staley

Stoichiometry and structural effects in alcohol chemisorption temperature-programmed desorption on molybdenum trioxide.

The mechanism of alcohol oxidation over MoO/sub 3/ has been examined by using temperature-programmed desorption spectroscopy (TPD) with simultaneous microbalance and mass spectral detection. Two types of experiments are reported. The alcohol structure has been varied over the sequence methyl, ethyl, 2-propyl, tert-butyl, and systematic changes in the amount of chemisorption, the peak desorption temperature, and the nature of the products have been observed. The amount of water produced during chemisorption of ethyl alcohol on MoO/sub 3/ at room temperature has been measured. This determination makes it possible to estimate the coverage of alkoxy groups after the chemisorption stage. The fate of these ethoxy groups during subsequent TPD can be followed. A stoichiometric accounting of both acetaldehyde production and catalyst reduction can be made.

Neutron powder diffraction study and physical characterization of zeolite D-RHO shallow-bed calcined at 773 Κ and 873 Κ

Zeolite RHO samples, shallow-bed calcined at 773 Κ and at 873 K, respectively, were studied by time-of-flight neutron powder diffraction, by infrared and by magic angle spinning nuclear magnetic resonance * Permanent address: Mineralogisches Institut der Universität Würzburg, Am Hubland, D-8700 Würzburg, Bundesrepublik Deutschland. ** Contribution no. 4110. 282 W. Η. Baur et al. spectroscopy. The chemical composition of the starting material was (NH4)10.2Cs0.2Al10.4Si37.6O96 · 43H20. After calcination, deuteration and dehydration the framework composition, as determined by NMR, IR, microcalorimetry and neutron powder diffraction, was approximately D9Al9Si39096 (D-RHO-S773 and D-RHO-S873) and 95% and 93% respectively, of the sample was accessible to methanol. About 2 to 4 AI atoms per unit cell were removed from the framework by the calcination. Both samples crystallize in the centrosymmetric space group Imbm at room temperature and at 623 Κ with cell constants a around 15.08 A. One of the samples shows no thermal expansion; the other has a negative thermal expansion coefficient. After correcting the powder patterns for irregular background effects, 250 Bragg peaks were utilized in the refinement. This is more than was previously possible in powder refinements of a zeolite RHO. We found the resulting geometry of the (Si,Al)02 framework to be more regular than in previous crystal structure refinements of zeolite RHO. Nonframework aluminum species could not be located in either sample at either temperature. In D-RHO-S 873 evidence for a deuterium atom bonded to oxygen atom O(l) was found. In zeolites H-RHO and D-RHO crystallizing in space group Imbm the cell constant is strictly dependent on the Τ—Ο bond lengths (where Τ is Si, Al), because of symmetry restrictions and because the angles Τ — Ο — Τ vary only slightly. Therefore the amount of aluminum per unit cell c(Al), in these zeolites can be determined from the known size of the unit cell length a by the relation c(Al) = [36.47a -542.3],

Studies on Organoaluminum Precursors OP Aluminum Nitride Fibers

A melt-spinnable precursor of aluminum nitride fibers derived from triethylaluminum and ammonia contains AlNH, AlNH 2 groups, and a small number of AlN units characteristic of aluminum nitride. The molecular weight of a spinnable composition is 070, corresponding to an average molecular weight of 13 organoaluminum groups. Ammonia, a curing agent for the fibers, accelerates elimination of ethane from the material, and decreases its solubility in toluene.

Positive-ion chemistry of cyclopentadienylcobalt dicarbonyl

Abstract Ion cyclotron resonance (ICR) techniques are used to study the positive-ion chemistry of CpCo(CO) 2 , Cp = η 5 -C 5 H 5 . An order of relative ligand binding energies to CpCo + is established: benzene > MeCN ⋍ NH 3 > tetrahydrofuran ⋍ Me 2 CO > propylene ⋍ Me-CHO ⋍ Me 2 O ⋍ NO ⩾ MeOH > CO. Relative ligand binding energies to CpCo(CO) + are similar. The proton affinity of CpCo(CO) 2 is indicated to be in the range 208 ∓ 4 kcal mol −1 , giving a homolytic bond energy of D (CpCo(CO) 2 + H) = 80 ∓ 6 kcal mol −1 . This suggests that protonation occurs on the ring. Methyl bromide reacts with CpCo + to substitute Me- for H- on the cyclopentadienyl ring. This reaction occurs four times and is followed by oxidative bromine transfer to give (η 5 -Me 4 C 5 H)CoBr + as the final product in this sequence. The results observed with CpCo(CO) 2 are generally very similar to those previously reported for CpNi(NO).

Capacitance bridge detector and signal lock for ion cyclotron resonance spectrometry

The design and operational characteristics of a capacitance bridge detector and accompanying signal lock system are presented. The signal lock is especially well suited for the measurement of small changes in ion concentration during photochemical experiments, thereby alleviating problems caused by resonant frequency shifts.

Gas-Phase Atomic Metal Cations. Ligand Binding Energies, Oxidation Chemistry and Catalysis

Ion cyclotron resonance (ICR) spectroscopy with a pulsed laser volatilization/ ionization source of atomic metal cations has recently been applied to studies of the reactions of gas-phase metal ions with neutral molecules 11,2]. Initial results from this laboratory have included a variety of mechanistic studies [1–4] as well as measurements of gas-phase ligand binding energies for a number of different metal cations [5–9]. These mechanistic and thermodynamic studies yield data which is useful in developing models for understanding molecular interactions.