Interpretation of hydrogenation kinetics of spent oil distillate from u.v. spectroscopy

Hydrotreatment of spent oil distillate was carried out on a commercial Ni-Mo-alumina catalyst in the temperature range 260–340 °C, with a liquid hourly space velocity (LHSV) of 0.7–2.0 h^?1, pressure of 4.5 MPa and $\text{H}{}_2\text{oil}$ ratio of 300 NL L^?1 (normal litre of H₂ per litre of feedstock). U.v. spectra of hydrogenated and original spent oil distillates (measured in normal hexane) gave a band with a maximum at 230 nm. The change in absorbance at three selected wavelengths for original oil distillate and hydrotreated oil at different operating conditions was taken as a guide for the determination of hydrogenation reaction rates (including partial saturation of aromatics and sulphur compound hydrogenolysis). The rate constants of hydrogenation reactions (k) using a second-order equation and a model of two parallel first-order reactions (k₁ and k₂) were calculated. Finally, the apparent activation energy (E_a), enthalpy of activation ($\text{ΔH}{}^1$) and entropy ($\text{ΔS}{}^1$) were calculated based on the values of k, k₁, and k₂. The calculated values of E_a based on k, k₁ and k₂ were 81.479, 71.188 and 62.882 kJ mol^?1, respectively. The values of $\text{ΔH}{}^1$ based on the same rate constants were 76.670, 66.564 and 58.433 kJ mol^?1, while the values of $\text{ΔS}{}^1$ were ?117.150, ?133.779 and ?150.823 J mol^?1 K^?1, respectively.     

Absorption of sulphur dioxide by sodium humates

As part of a programme for assessing the potential of basic humates as stack gas scrubbing media, the reaction of sodium salts of coal derived humic acids (HA) with sulphur dioxide was investigated. The principal absorption mechanism was found to be acid-base:

$\text{Na-HA(aq) + SO}{}_2\text{(g) + H}{}_2\text{O}\text{?}\text{HA(s) + HSO}{}^{\mathrm{t-}}{}_3\text{(aq) + Na}{}^{\mathrm{+}}\text{(aq)}\text{Soluble sodium}\text{Insoluble humic}\text{humate}\text{acid}$

However, formation of a sulphur dioxide-HA ‘complex’ was observed under conditions (low pH, high temperature) which favoured conversion of a significant fraction (> 5%) of dissolved sulphites to the SO₂(aq) ‘H₂SO₃’ form. Greater complexation of SO₂(aq) was observed for HA preparations which had been stored under basic conditions for periods up to two years. Reversibility of absorption and desorption was demonstrated. Similar experiments with hydrogen sulphide revealed no significant reaction with sodium or iron(III) humates.     

High-temperature 1H n.m.r. study of oxidized coal

Two coking coals, a caking and a non-caking coal are examined in a Bruker pulsed ¹H n.m.r. spectrometer in the temperature range 293–730 K. One coking and the caking coal are oxidized in air at 383 K for 13 days. Temperatures of signal appearance and loss are noted as well as the temperatures of minimum signal half-peak width ($\text{ΔH}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$). There occurs no change in the above three temperatures with oxidation of the coals. The variation of ($\text{ΔH}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$) with temperature of the coal is also measured. Changes in ($\text{ΔH}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$) are more pronounced for the caking coal. The softening and solidification temperatures are below and above, respectively, those reported using the Gieseler method. Values of ($\text{ΔH}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$) increase beyond the minimum value as the fluidity continues to increase. This may be caused by an increase in average molecular weight of constituent molecules and/or an increasing concentration of free radicals in the fluid phase. This experimental approach may afford a new method to characterize coals which are to be used in liquefaction processes.     

Ionic conductivities of poly(methoxy polyethylene glycol monomethacrylate) complexes with LiSO3CH3

Ionic conductivity values for LiSO₃CF₃ complexes with two amorphous poly(methoxy polyethylene glycol monomethacrylates) (PEM) were determined and values as high as $\text{～6 × 10}{}^{\mathrm{?4}}\text{Ω}{}^{\mathrm{?1}}\text{cm}{}^{\mathrm{?1}}$ at 373 K and $\text{～2 × 10}{}^{\mathrm{?5}}\text{Ω}{}^{\mathrm{?1}}\text{cm}{}^{\mathrm{?1}}$ at 293 K were achieved. These values are compared with those obtained for a poly(ethylene oxide) (PEO)-LiSO₃CF₃ complex of similar salt concentration with an ether oxygen to Li⁺ ion ratio of 18. The conductivity results for the complexes are similar at temperatures >343 K but at 293 K the values for the conductivities of the PEM-LiSO₃CF₃ complexes are approximately two orders of magnitude higher than those for the PEO-LiSO₃CF₃ complex. This difference is believed to be due at least in part to the presence of a large amount of crystalline material in the PEO-LiSO₃CF₃ complex below 323 K.     

A calculation of the elastic constant c33 of a graphite crystal as a function of temperature

A calculation is presented of the elastic constant C₃₃ of a graphite crystal as a function of temperature up to 2500 K, taking into account the anharmonic contribution and the changes in interlayer interactions due to the large lattice thermal expansion. Parametric variations in the theory show that the anharmonic contribution to C₃₃ depends principally on the parameter ($\text{?}{}^2\text{C}{}_{33}\text{?e}{}^2{}_{\mathrm{zz}}$) Comparison of theoretical results with the experimental data, which is mainly from neutron scattering experiments, shows that the data can be accounted for if ($\text{?}{}^2\text{C}{}_{33}\text{?e}{}^2{}_{\mathrm{zz}}$) lies in the range 7–10 × 10¹³ dynes/cm². A theoretical estimate of ($\text{?}{}^2\text{C}{}_{33}\text{?e}{}^2{}_{\mathrm{zz}}$) based on Lennard-Jones potentials between atoms in adjacent basal planes gives a value of 9·07 × 10¹³ dynes/cm².     

Kinetics of hydrogasification of coke catalysed by Fe,Co and Ni

The catalysis of hydrogasification of carbon by Fe, Co and Ni was studied using a special petroleum coke with extremely low reactivity. The kinetics were studied with impregnated coke in a fixed-bed flow reactor between 1133 and 1235 K and up to 2 MPa, yielding the following rate equation: Apparent activation energies and heats of adsorption are: Fe, 152 and ?92 kJ mol^?1; Co, 201 and ?82 kJ mol^?1 Ni, 165 and ?50 kJ mol^?1. These studies with impregnated coke as well as further gasification experiments with cokes heat-treated after impregnation with metal salts up to 2273 K confirmed a spillover mechanism and excluded any influence of electronic interactions between carbon and the catalyst metals.     

Characterization of poly(1,4-phenyleneterephthalamide) in concentrated sulphuric acid: 1. Static and dynamic properties

Laser light scattering including angular dependence of total integrated scattered intensity and of the spectral distribution has been used to characterize five samples of poly(1,4-phenylene terephthalamide), PPTA (commercially known as Kevlar), of different molecular weights in 96% sulphuric acid and 0.1 NK₂SO₄. The data are supplemented by intrinsic viscosity measurements used to detect the possible effects of association, by differential refractometry providing a measure of the refractive index increments in mixed solvents (H₂O, H₂SO₄ and K₂SO₄) and by spectrophotometry for the extinction coefficient needed in the correction of attenuation in light scattering studies. The results show 〈D〉Z = 2.11 × 10^?5$\text{M}\text{?}{}_{\mathrm{<mtext>W</mtext>}}{}^{\mathrm{?0.75}}\text{cm}{}^{\mathrm{?2}}\text{s}{}^{\mathrm{?1}}$ in reasonable agreement with an average of many of the published intrinsic viscosity data obeying [η] = 1.09 × 10?3 M_w^1.25 ml g^?1 and _w expressed in g mol^?1.     

Macromolecular properties of heparin in dilute solution: 2. Dimensional parameters as a function of pH,ionic strength and desulphation

A bovine heparin fraction was examined by sedimentation analysis and intrinsic viscosity measurements as a function of ionic strength in the range of 0·1 to 1·0 M, and at pH 2·5 and 6·0. The following experimental parameters were obtained: M, S⁰_20,W, D⁰_20,W, $\text{V}\text{?}$, and [η]. Other physical parameters were calculated based on a random coil model (supported by the theory of Mandelkern and Flory) e.g., $\text{(}\text{r}\text{?}{}^2\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, $\text{(}\text{s}\text{?}{}^2\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$. Similar studies were made on a heparin sample as a function of desulphation as resulting from graded mild hydrolysis. Since desulphation is accompanied by decreasing anticoagulant activity of heparin, the latter was correlated with various calculated and measured physical parameters. Significantly $\text{(}\text{r}\text{?}{}^2\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ decreases with decreased desulphation and therefore decreased biological activity.     

Ionic conductivities for poly(ethylene oxide) complexes with lithium salts of monobasic and dibasic acids and blends of poly(ethylene oxide) with lithium salts of anionic polymers

Lithium salts of two polyanionic addition polymers containing alkyl sulphonic acid and perfluoroalkyl carboxylic acid side groups were prepared. Blends of these polymers were formed with poly(ethylene oxide) (PEO). The blend containing alkyl sulphonate units showed some phase separation but this was not observed for the blend containing perfluoroalkyl carboxylate groups. In the latter case a comparatively high conductivity of $\text{～10}{}^{\mathrm{?5}}\text{Ω}{}^{\mathrm{?1}}$ cm^?1 at 374 K was obtained. The anionic units in these blends are expected to be virtually immobile. Complexes formed from PEO and the Li-salt of hexafluoroglutaric acid had similar high ionic conductivities and there are grounds for supposing that the anions in these complexes may also be substantially immobilized. In addition, conductivity values were obtained for some PEO complexes containing lithium salts of some monobasic acids and it was found that the complex formed from the Li-salt of the strongest acid gave the highest conductivity ($\text{～4 × 10}{}^{\mathrm{?4}}\text{Ω}{}^{\mathrm{?1}}$ cm^?1 at 373 K for a PEO-LiSO₃CF₃ complex).     

Chemical beneficiation of coal with aqueous hydrogen peroxide/sulphuric acid solutions

The removal of sulphur and ash from coal treated with aqueous hydrogen peroxide/sulphuric acid solutions has been studied at ambient temperature, under a variety of experimental conditions. Almost complete elimination of the sulphate and the pyritic sulphur was observed in most cases, as well as substantial reduction in the ash content. The other components of the organic coal matrix were not affected to a significant extent, indicating high selectivity of the $\text{H}{}_2\text{O}{}_2\text{H}{}_2\text{SO4}$ system towards sulphur oxidation. An optimal H₂SO₄ concentration was established, above which the acid was found to have an adverse effect on the oxidation of pyrite by hydrogen peroxide.     

Dielectric constants of coal-water slurries at 750 MHz

Measurements of the real portion of the dielectric constant of coal-water slurries at 750MHz are reported. Slurries of 40–65wt% of either Illinois No. 6, Utah bituminous or Texas lignite coals over the temperature range 11–71 °C were studied. The dielectric constant was independent of coal type and particle size within experimental error. The measured values of dielectric constants agreed with those predicted by the Looyenga equation: $\text{?′}\text{= [?′}{}^{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}{}_2\text{+ φ(?′}{}^{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}{}_1\text{??′}{}^{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}{}_2\text{)]}{}^3$ where: $\text{?′}$, the mean value of the dielectric constant; ?′₁, the dielectric constant (3.8) of the dry coal; ?′₂, the dielectric constant of water; φ, the volume fraction of coal.     

Nucleophilic substitution onto poly (methyl methacrylate): 3. Compositional homogeneity of the substituted polymethacrylates

The chemical homogeneity of a series of copolymers obtained by nucleophilic substitution of organolithium reagents RCH₂Li [R = S(C₆H₅), SOCH₃, SO₂CH₃ and SO₂N(CH₃)₂] on a high molecular weight poly(methyl methacrylate) (PMMA, $\text{DP}{}_{\mathrm{n}}\text{= 700}$) has been studied by different methods, over a wide range of substitution degrees ($\text{0.14 ?}\text{DS}{}_{\mathrm{m}}\text{? 0.76}$). ‘Cross’ fractionation is much more efficient than ‘one direction’ fractionation, and it allows the determination of $\text{}\text{?}\text{gs}{}^2$ variance values as low as 2 × 10^?4 with sufficient accuracy. The light scattering method is far less sensitive in this range of low compositional polydispersity, even for a suitable system. The fairly high chemical homogeneity observed for all the copolymers, prepared either in homogeneous or heterogeneous solution, may be correlated with both the high molecular weight of the PMMA precursor and the autoretarded kinetics of the substitution process.     

Properties of extremely high molecular weight polystyrene in solution

Extremely high molecular weight polystyrenes with a $\text{M}\text{?}{}_{\mathrm{w}}$ in the range 10.8 × 10⁶ to 2.2 × 10⁷ were prepared by emulsion polymerization initiated with a heterogeneous initiator at 30°C, which has a ‘living character’. Samples of polystyrene were characterized by light scattering and viscometry in toluene and benzene at 25°C, and in θ-solvent cyclohexane at 34.8°C. Also determined were the relationships of mean-square radius of gyration 〈s²〉 (m²) and the second virial coefficient A₂ (m³ mol kg^?2) on the molecular weight, which for toluene and benzene are described in equations: Toluene (25°C) $\text{〈s}{}^2\text{〉=1.59 × 10}{}^{\mathrm{?23}}\text{M}\text{?}{}_{\mathrm{w}}{}^{1.23}$; $\text{A}{}_2\text{=4.79 × 10}{}^{\mathrm{?3}}\text{M}\text{?}{}_{\mathrm{w}}{}^{\mathrm{?0.63}}$; Benzene (25°C) $\text{〈s}{}^2\text{〉=1.23 × 10}{}^{\mathrm{?22}}\text{M}\text{?}{}_{\mathrm{w}}{}^{1.20}$; $\text{A}{}_2\text{=2.59 × 10}{}^{\mathrm{?3}}\text{M}\text{?}{}_{\mathrm{w}}{}^{\mathrm{?0.59}}$. The parameters in the Mark-Houwink-Sakurada equation were established, for extremely high molecular weight polystyrene in toluene and in benzene, at 25°C into the form giving for $\text{[η] (}\text{m}{}^3\text{kg}{}^{\mathrm{?1}}\text{): [η] = 8.52 × 10}{}^{\mathrm{?5}}\text{M}\text{?}{}_{\mathrm{w}}{}^{0.61}$; $\text{[η] = 1.47 × 10}{}^{\mathrm{?4}}\text{M}\text{?}{}_{\mathrm{w}}{}^{0.56}$. The mentioned relations, as well as the obtained values of Flory parameter ?₀ and of ratio $\text{[η]}\text{M}\text{?}{}_{\mathrm{w}}{}^{0.5}$ were compared with solution properties of high molecular weight polystyrene with narrow molecular weight distribution prepared by anionic polymerization by Fukuda et al.     

Low-angle laser light scattering from polystyrene solutions: intensity measurements and photon correlation spectroscopy

Light scattering measurements have been made on polystyrenes with a range of molecular weights in toluene and for one polystyrene with a range of molecular weights in toluene and for one polystyrene in a range of solvents including a theta solvent. Intensity data were used to calculate second virial coefficients and molecular weights, whilst photon correlation spectroscopy was used to calculate diffusion coefficients. All measurements were made at 30°C and at a scattering angle of ca.4°. The data were used to examine current theories of polymer diffusion and the relation between hydrodynamic radius (R_H) and radius of gyrations ($\text{〈s}{}^2\text{〉}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$). The results support accepted theories of polymer diffusion, but suggest that the relation between R_H and $\text{〈s}{}^2\text{〉}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ requires further analysis.     

Polymerization of N,N′-methylenebisacrylamide initiated by CEIV-thiourea redox system

The kinetics of polymerization of the symmetrical non-conjugated divinyl monomer N,N′-methylenebisacrylamide has been studied using Ce^IV-thiourea redox system as initiator. The rate of polymerization, R_p is proportional to $\text{[}\text{Ce}{}^{\mathrm{<mtext>IV</mtext>}}\text{]}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, $\text{[}\text{thiourea}\text{]}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ and $\text{[}\text{monomer}\text{]}{}^{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$. A cyclopolymerization mechanism fits in with the experimental results.     

Viscometric behaviour of polystyrene in tetralin/cyclohexane mixtures

For solutions of polystyrene (M=10⁵–10⁶ g mol^?1), intrinsic viscosities [η] have been measured at 34.5°C, which is the θ temperature for the polymer in cyclohexane. The solvents comprised cyclohexane in admixture with a thermodynamically good solvent, 1,2,3,4-tetrahydronaphthalene (tetralin, TET) over the whole range of solvent composition. From an assessment of several extrapolation procedures, a value of 85 × 10^?3$\text{(±1 × 10}{}^{\mathrm{?3}}\text{)}\text{cm}{}^3\text{g}{}^{\mathrm{<mtext>?3</mtext><mtext>2</mtext>}}\text{mol}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ was obtained for K_θ (in the relationship $\text{[η] = K}{}_{\mathrm{\theta }}\text{M}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{α}{}^3$, where α is the expansion factor), thus yielding $\text{0.681}\text{A}\text{?}\text{g}{}^{\mathrm{<mtext>?1</mtext><mtext>2</mtext>}}\text{mol}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, 2.25 and 10.2 for the unperturbed dimensions, steric factor σ and characteristic ratio C_∞ respectively. The value of K_θ was independent of solvent composition despite the finite excess free energy of mixing for the solvent components alone, which has been asserted elsewhere to affect K_θ. The present results, in conjunction with previous ones relating to 98.4°C, indicate a value of ?0.89 × 10^?3 deg^?1 for the temperature coefficient of the unperturbed dimensions.     

The unperturbed molecular dimensions of poly(ethylene oxide) in aqueous solutions from intrinsic viscosity measurements and the evaluation of the theta temperature

Intrinsic viscosity measurements were carried out on five well characterized fractions of poly(ethylene oxide) in aqueous solutions at 24.9°, 34.9°, and 45.5°C. The Stockmayer-Fixman extrapolation was applied to the data: it yields the unperturbed dimensions K₀ of the chain. The unperturbed root-mean-square end-to-end distance $\text{〈}\text{R}\text{?}{}^2\text{〉}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}{}_0$ calculated for the polymer fractions in water indicate that the polymer molecules are expanded in this solvent as the temperature is raised. The temperature coefficient of unperturbed dimension, $\text{d In}\text{〈}\text{R}\text{?}{}^2\text{〉}{}_0\text{d}\text{t}\text{= 0.024}\text{K}{}^{\mathrm{?1}}$, calculated for poly(ethylene oxide) in water using the present data is about 100 times higher than the literature values of 0.23 (±0.02) × 10^?3 K^?1 and 0.2 (±0.2) × 10^?3 K^?1, respectively, obtained from force-temperature (‘thermoelastic’) measurements on elongated networks of the polymer in the amorphouse state and form viscosity measurements on this polymer in benzene. A value of θ=108.3°C was obtained from the temperature dependence of the interaction parameter B in the Stockmayer-Fixman equation.     

Hydrogen mass transfer in liquid hydrocarbons at elevated temperatures and pressures

The mass transfer rate of hydrogen in tetralin and hydrogenated SRC II liquid was studied in a stirred vessel at 606–684 K and 7.0–13.5 MPa. Experiments were carried out using a newly developed in-situ hydrogen probe made of semi-permeable nickel membrane. The effects of stirrer speed, liquid height to vessel diameter ratio, temperature and pressure on mass transfer rate coefficients were investigated. The experimentally determined $\text{K}{}_{\mathrm{<mtext>l</mtext>}}\text{a}$ values were correlated in terms of power input per unit volume of liquid and liquid height to vessel diameter ratio as follows: $\text{k}{}_{\mathrm{<mtext>L</mtext>}}\text{a = 3.43 × 10}{}^{\mathrm{?4}}\text{(}\text{P}\text{V}\text{)}{}^{0.8}\text{(}\text{H}\text{D}{}_{\mathrm{<mtext>T</mtext>}}\text{)}{}^{\mathrm{?1.9}}$ Furthermore, the liquid-phase mass transfer coefficient, $\text{k}{}_{\mathrm{<mtext>l</mtext>}}$, was found to be of the order of 10^?5 m s^?1 for low agitator speeds.     

Carbon formation from methane in combustion products

The rates of deposition of carbon on alumina surfaces and on soot particles, have been measured in a pilot scale tubular reactor in which cold methane was mixed with combustion products at 1920°K. A hard grey metallic film of carbon, quite free of soot, was deposited on alumina surfaces for initial methane concentrations between 12 and 24 per cent. An induction period of slow growth rate, before a film covered the surface completely, was followed by a constant growth rate. Measured growth rates were from 0·06 × 10^?6 to 1·43 × 10^?6 g/cm² sec of carbon on alumina at 1270°K to 1450°K, and from 0·1 × 10^?4 to 1·14 × 10^?4 g/cm² sec on soot particles at 1370°K to 1700°K. Methane decomposition rates were much higher than predicted by the unimolecular mechanism indicating a predominance of radical reactions. Carbon deposition rates were related to the mole fraction, χ, of hydrocarbons in the gas which bear more than three carbon atoms per molecule, by, $\text{m}\text{?}{}_{\mathrm{f}}\text{= 1·0 × 10}{}^2\text{n.χ}$. exp (?42,300/RT_f), g/cm²sec for carbon film, $\text{m}\text{?}{}_{\mathrm{s}}\text{= 4·6 × 10}{}^3\text{nχ}$ exp (? 46,100/RT_g), g/cm² sec for soot. A precoat of soot increased the growth rate of film carbon by 1·8 to 7·8 times yielding a hard adherent dull brown film