Crystal structure of bis(2,6-diaminopyridinium) diaqua-bis-(2,6-pyridinedicarboxylato)-bis(2,6-pyridinedicarboxylato)- dibismuthate(III) tetrahydrate, (C28H16O18N4Bi2)(C5H8N3)2 · 4H2O

C38H40Bi2N10O22, triclinic, P1̅̅ (No. 2), a = 9.699(1) Å, b = 10.500(1) Å, c = 10.890(1) Å, α = 85.587(3)°, β = 88.128(3)°, γ = 84.257(3)°, V = 1099.9 Å3, Z = 1, Rgt(F) = 0.028, wRref(F2) = 0.061, T = 295 K.

Crystal structure of a binuclear polymeric self-assembled lead(II) complex

A polymeric self-assembled complex [[Pb(pydc)(pydc-H2)(H2O)2]2]n is prepared from the complexation of a novel pyridine containing self-assembling system, LH2, [pyda-H2]2+[pydc]2- (pyda = 2,6-pyridindiamine and pydc-H2 = 2,6-pyridinedicarboxilic acid) and lead(II) nitrate in 84% yield. The characterization was performed using X-ray crystallography. The crystal system is triclinic with space group P1 and two molecules per unit cell. The unit cell dimensions are a = 6.913(2) A, b = 10.687(4) A and c = 11.182(4) A with alpha = 92.805(6) degrees, beta = 101.821(6) degrees and gamma = 95.688(6) degrees. The final R value is 0.0373 for 4633 reflections measured. This compound is a nine-coordinate binuclear complex with two metal fragments linked via the central four-membered Pb2O2 ring. The crystal also contains a neutral [pydc-H2] molecule, that form hydrogen and coordination bonds that dominate the crystal packing, by forming layers of molecules.

Synthesis, characterization, and X-ray crystal structures of Co(II) and La(III) complexes of a pyridine containing self-assembling system and solution studies of the Co(II) complex

The complexes [pyda.H]2[Co(pydc)2]·H2O (I) and [pyda·H]2[La2(pydc)4(H2O)4].2H2O (II) were prepared from the complexation of a novel pyridine containing self-assembling system LH2, ([pyda·H2]2+[pydc]2–) (pyda = 2,6-pyridinediamine and pydc·H2 = 2,6-pyridinedicarboxylic acid), with cobalt(II) and lanthanum(III) salts in 82% and 74% yields, respectively. The characterizations were performed using elemental analysis, ESI mass spectroscopy as well as 1H and 13C solution NMR spectroscopy, and X-ray crystallography. The crystal systems I and II are monoclinic and triclinic with space groups P21/n and P[Formula: see text] respectively. Coordination number around each Co atom is six with distorted octahedral geometry, while coordination number around each La atom is nine with highly distorted tricapped trigonal prism geometry. The paramagnetic Co(II) and diamagnetic La(III) complexes show 1H NMR resonances of both anionic [pydc]2- and cationic counter ion [pyda·H]+ in DMSO-d6. The complexation reactions of the complex I in aqueous solution were investigated by potentiometric pH titrations and the equilibrium constants for all major complexes formed are described. The results are presented in the form of distribution diagrams revealing the concentrations of individual complex species as a function of pH. The results revealed that at a pH range 4.0–4.5 the major complex species is [(pyda·H)]2[Co(pydc)2].Key words: self-assembly, X-ray crystal structure, Co(II) complex, La(III) complex, 2,6- pyridinedicarboxylic acid, 2,6-pyridinediamine, hydrogen bonding.

Predicting the reactivity of proteins from their sequence alone: Kazal family of protein inhibitors of serine proteinases

An additivity-based sequence to reactivity algorithm for the interaction of members of the Kazal family of protein inhibitors with six selected serine proteinases is described. Ten consensus variable contact positions in the inhibitor were identified, and the 19 possible variants at each of these positions were expressed. The free energies of interaction of these variants and the wild type were measured. For an additive system, this data set allows for the calculation of all possible sequences, subject to some restrictions. The algorithm was extensively tested. It is exceptionally fast so that all possible sequences can be predicted. The strongest, the most specific possible, and the least specific inhibitors were designed, and an evolutionary problem was solved.

Improvement of Medium And Light Oil Recovery With Thermocatalytic In Situ Combustion

Abstract

The objective of this paper was to improve the understanding of the basic mechanisms responsible for fuel formation in in situ combustion (ISC) and to use that understanding to identify the conditions under which the ISC process can be applied to improve the recovery of heavy, medium and light oils. Using rocks of varying mineralogical composition and crude oils with different contents of asphalteoes and resins, pyrolysis and combustion tests were performed to examine the influence of thermocatalytic mocatalytic reactions on the amount and reactivity of fuel in an ISC process.

From the results, it appears that the controlling mechanism of fuel formation is the conversion of crude oil components by radical polymerization. The conversion rate is influenced by many factors such as process condition and the nature of the crude oil and reservoir rock minerals. The formation of resins from lighter hydrocarbons and their polymerization into asphalrenes can be accelerated by clay minerals and metal components existing in the fuel formation zone. Therefore the importance of low tem-perature oxidation reactions is increasing in the thermocatalytic recovery process of even light and medium oils.

Introduction

The application of thermal energy to hydrocarbon reservoirs for increasing crude oil recovery has been given much attention. There are two main types of thermal recovery process, namely hot fluid injection and in situ combustion (ISC). ISC is thermal oil recovery method with a large theoretical potential but limited success in field application. This technique is also known to be the most complicated oil recovery method. It includes some aspects of nearly every oil recovery process.

An important parameter to be considered in the design of an ISC project is the amount of fuel deposited ahead of the combustion front. Excessive fuel deposition causes a slow rate of advance of the burning front and large air compression costs and reduces the maximum oil recovery. On the other hand, if the fuel concentration is too low, the heat of combustion will not be sufficient to raise the temperature of the rock and the contained fluids to a level of self-sustained combustion. This leads to an unstable burning front and combustion failure. Thus, it is necessary to understand the reactions occurring at different temperatures as the combustion front moves in the reservoir.

The most important controlling factors of the fuel formation are the nature of the crude oil and reservoir rock minerals and During this work, experiments were conducted to describe how the clay minerals and heavy metals derivatives, such as iron, affect the thermocatalytic conversion of crude oil compounds as well as the fuel formation and combustion.

Thermocatalytic Oxidation of Crude Oil Compounds

It has been confirmed by many authors, for example, Bousaid and Ramey(3), Dabous and Fulton(4) Burger and Sahuquet(5), that basically three major reactions occur at different temperature levels in an ISC process. These reactions are known as:Low temperature oxidation (LTO)Fuel deposition reactions (FDR)High temperature oxidation (HTO)