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.     

Polymer translational diffusion: 2. Non-theta solutions,polystyrene in butan-2-one

The diffusion of linear polystyrene under non-theta conditions in butan-2-one has been studied by Rayleigh light scattered linewidth measurements for the molecular weight range of 2.08 × 10⁶ to 8.7 × 10⁶ and as a function of concentration. By extrapolation of diffusion coefficient values to zero concentration we find that $\text{D}{}_0\text{= 5.5 × 10}{}^{\mathrm{?4}}\text{M}\text{?}{}^{\mathrm{?0.561}}{}_{\mathrm{w}}\text{cm}{}^2\text{s}{}^{\mathrm{?1}}$. The first order concentration dependence $\text{k}{}_{\mathrm{<mtext>d</mtext>}}\text{c}$ changes sign as the molecular weight increases, $\text{k}{}_{\mathrm{<mtext>d</mtext>}}$ being fairly small and negative at low molecular weights and increasingly positive above $\text{M}\text{?}{}_{\mathrm{w}}\text{?230 000}$.     

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.     

Mineral matter as a measure of oxidation of a coking coal

The petrography, agglomerating characteristics, low-temperature ash (LTA) mineralogy and chemistry of ten consecutive channel samples from D seam, Natal Ridge, Crowsnest coalfield, British Columbia, were compared. It was found that there is a direct correlation between oxidation, as indicated by absence or limited caking character, and the presence of the mineral bassanite ($\text{CaS0}{}_4\text{·}\text{1}\text{2}\text{H}{}_2\text{O}$) in LTA. An attempt to estimate quantitatively the extent of oxidation by the anhydrite content in LTA samples further heated to 500 °C has resulted in the detection of partial oxidation of a coal sample having an FSI of $\text{6}\text{1}\text{2}$, reduced from a normal value of 8. The recognition and quantification of oxidation using epigenetic gypsum and its derivatives, however, probably only applies to the weakly pyritic, usually freshwater, coals typical of the Rocky Mountain coalfields of British Columbia and the Gondwana coalfields of the southern hemisphere.     

Studies of a CuY zeolite as a redox catalyst

The stability and behavior of CuY in the redox cycles with $\text{CO}\text{O}{}_2$, $\text{H}{}_2\text{O}{}_2$, and $\text{CO}\text{NO}$ have been studied using a microbalance operating in the flow mode and with a standard (BET) volumetric system. When CO was used as a reducing agent CO₂ was produced, thus removing oxygen from the zeolite lattice, but when H₂ was used only some of the H₂ consumed was evolved as H₂O. The rest was retained as lattice OH groups, but this was minimal when H₂ was used after treating the sample with CO. Oxidation with NO produced only N₂. At 500 °C the sample was stable and could be reversibly oxidized and reduced through many cycles using either $\text{CO}\text{O}{}_2$ or $\text{NO}\text{CO}$. In all cases the ratio $\text{O}\text{Cu}$ was close to 0.5, i.e., $\text{1e}\text{Cu}$. Treatment in CO at higher temperatures did not affect the reversible nature of the oxidation, but now the valence change was substantially larger; it approached $\text{2e}\text{Cu}$. The crystallinity of the exchanged zeolite was studied using X-ray diffraction and by measurement of the pore filling with liquid N₂. No significant changes could be detected after the different treatments, even those performed at 750 °C. Temperature-programmed reduction, temperature-programmed oxidation, and X-ray diffraction studies were made and the different maxima are reported. CuO and Cu ^o appeared in the oxidized and reduced samples, respectively, after treatment at 750 °C in CO but not at lower temperatures. Subsequent redox cycles at 500 °C did not appear to affect the size or amount of Cu ^o crystallites. CuY was active in the oxidation of CO with O₂ or NO. Its activity was lower than that of FeY zeolite when it exhibited an oxygen-carrying capacity of 0.5 $\text{O}\text{Cu}$. Treatment with CO at 750 °C, however, reversed the situation. Kinetic results showed that the fresh CuY catalyst was close to zero order in CO and fractional order in O₂ with an activation energy of 15 kcal/mole. After treatment at 750 °C in CO, the rate law became dependent upon the $\text{CO}\text{O}{}_2$ ratio. It was close to first order in CO and zero order in O₂ under oxidizing conditions ($\text{CO}\text{O}{}_2\text{≤ 2}$), but the orders were reversed under reducing conditions ($\text{CO}\text{O}{}_2\text{> 2}$). The activation energies were 12 and 15 kcal/mole, respectively. The data suggested that the Cu²⁺ with bound oxygen are the species active in the oxidation reaction.     

Upgrading of middle distillate fractions of a syncrude from Athabasca oil sands

Current processes for upgrading bitumen from Athabasca oil sands produce synthetic crudes which are high in aromatics and deficient in hydrogen. As a consequence, middle distillate fractions derived from these syncrudes produce diesel fuels of low cetane number and jet fuels which are hydrogen deficient. Results obtained from bench-scale hydrotreating experiments indicate that quality fuels may be produced from Athabasca syncrudes. Middle distillate fractions from this source were subjected to high-severity hydroprocessing in a continuous-flow reactor unit using conventional hydrotreating catalysts which were pre-sulphided by a mixture of $\text{H}{}_2\text{H}{}_2\text{S}$. Aromatic hydrogenation at high temperatures and pressures was affected by the approach to thermodynamic equilibrium, however, at lower temperatures, in some cases virtually 100% saturation was achieved and treated fractions were found to meet cetane number and jet fuel smoke point requirements. Data treatment in the present study includes a model for the hydrogenation kinetics and correlations between aromatic carbon and fuel combustion properties.     

Oxidation of hydrogen sulfide over microporous carbons

Microporous carbon of high purity was produced by the carbonization of Saran at 900° followed by activation in either CO₂ at 900°, O₂ at 300°, or air at 425°. The activated carbons were characterized using N₂ adsorption at ?195° CO₂ adsorption at 25°, and mercury and helium displacements. Hydrogen sulfide oxidation (at H₂S pressures between 0.4–3.8 Torr) by O₂ (in excess of stoichiometric amount) was studied between 100–160° using a microbalance, that is by weighing the build-up of sulfur on the carbon. The predominant reaction, $\text{H}{}_2\text{S +}\text{1}\text{2}\text{O}{}_2\text{→}\text{1}\text{2}\text{S}{}_2\text{+ H}{}_2\text{O}$ was first order in H₂S concentration and independent of O₂ concentration. The rate was only slightly reduced by sulfur build-up to at least 36%, by weight, on the carbon. The oxidation rate was significantly higher over the O₂-activated carbon than over the CO₂-activated carbon. Throughout the studies, oxidation rates could be correlated with area active to O₂ chemisorption. It is concluded that H₂S oxidation proceeds via rapid dissociative chemisorption of oxygen on carbon sites followed by reaction with H₂S. Rates of H₂S oxidation were also studies over commercial, granular activated carbons of significant ash contents.     

Redispersion of supported platinum catalysts

The redispersion of platinum on γ-Al₂O₃, SiO₂, and TiO₂ is experimentally studied by means of hydrogen chemisorption, X-ray diffraction, transmission electron microscopy, temperature-programmed reduction, and cyclohexene hydrogenation reaction. The increase in dispersion following treatment in oxygen below 600 °C occurs only for $\text{Pt}\text{γ-Al}{}_2\text{O}{}_3$. For $\text{Pt}\text{TiO}{}_2$, only the presence of chlorine during oxidation brings about a significant redispersion. For $\text{Pt}\text{SiO}{}_2$, redispersion does not occur under any condition. Redispersion can occur only in the presence of platinum oxide which could be stabilized by forming a complex with the support. The method for determining whether or not redispersion will occur for any systems and the conditions needed for redispersion are discussed.     

Liquid crystalline polymers as additives to enhance the device properties of low molecular mass liquid crystals

Magnetic and electric fields have been used to determine the splay (k₁₁) and bend (k₃₃) elastic constants in a series of polymer/monomer liquid crystal solutions using the well known Freedericksz transition technique. Measurements have been carried out as a function of concentration and temperature. The polymer used was a smectogenic polysiloxane side chain liquid crystal with both cyanobiphenyl and benzoate ester side groups. The monomeric solvent was the nematogen 4-n-pentyl-4′-cyanobiphenyl. All of the solutions studied were nematogenic up to a concentration of 40% w/w. It has been shown that k₁₁, k₃₃ and $\text{k}{}_{33}\text{k}{}_{11}$ all decrease with increasing polymer concentration and that at high enough concentrations $\text{k}{}_{33}\text{k}{}_{11}$ tends to become independent of temperature. The implications of these results are discussed in terms of the performance of the most common liquid crystal display, i.e. the twisted nematic device.     

Effects of metal-support interactions on the hydrogenation of CO over PdSiO2 and PdLa2O3

A study of CO hydrogenation over $\text{Pd}\text{SiO}{}_2$ and $\text{Pd}\text{La}{}_2\text{O}{}_3$ has been carried out for the purpose of identifying the effects of Pd dispersion, Pd morphology, and support composition on the catalytic activity of supported Pd. The specific activity of each catalyst for methanol and methane synthesis was determined from microreactor studies carried out at a fixed set of reaction conditions. Palladium dispersion was measured by H₂O₂ titration, and the morphology of the Pd crystallites, as expressed by the distribution of Pd(100) and Pd(111) planes, was determined from in situ infrared spectra of adsorbed CO. The crystallite morphology of the $\text{Pd}\text{SiO}{}_2$ catalysts is the same, independent of Pd weight loading: 90% of the surface is comprised of Pd(100) planes and 10% of the surface is comprised of Pd(111) planes. By contrast, the crystallite morphology of the $\text{Pd}\text{La}{}_2\text{O}{}_3$ catalysts changes with Pd loading. Primarily Pd(100) planes are exposed at low-weight loadings while Pd(111) planes are exposed at high-weight loadings. The Pd dispersion has little effect on the methanol turnover frequency over both $\text{Pd}\text{SiO}{}_2$ and $\text{Pd}\text{La}{}_2\text{O}{}_3$, for dispersions between 10 and 20%. On the other hand, the methane turnover frequency is independent of Pd dispersion over $\text{Pd}\text{SiO}{}_2$, but increases with decreasing dispersion over $\text{Pd}\text{La}{}_2\text{O}{}_3$. It is further observed that the Pd morphology influences the specific activity of $\text{Pd}\text{La}{}_2\text{O}{}_3$ for methanol synthesis: Pd(100) is nearly threefold more active than Pd(111). For a fixed morphology, the specific methanol synthesis activity of $\text{Pd}\text{La}{}_2\text{O}{}_3$ is a factor of 7.5 greater than that of $\text{Pd}\text{SiO}{}_2$.     

The time dependent strain potential function for a polymeric glass

Torsion and normal force measurements were made during single step stress relaxation experiments on a polymeric glass (PMMA). Isochronal data were analysed using an approach adapted from that developed by Penn and Kearsley¹ (for incompressible elastic materials) to determine the derivatives $\text{?W}\text{?I}{}_1$, and $\text{?W}\text{?I}{}_2$ of the time dependent strain potential function. $\text{?W}\text{?I}{}_1$ and $\text{?W}\text{?I}{}_2$ are determined from existing solution to the torsion of an incompressible cylinder. A special solution to the torsion of a compressible cylinder is presented and it is shown that the values of $\text{?W}\text{?I}{}_1$ and $\text{?W}\text{?I}{}_2$ obtained using this solution to analyse the data do not differ greatly from those obtained using the incompressible solution. It is found from both solutions that $\text{?W}\text{?I}{}_1$ is negative and increases towards zero with increasing time and deformation while $\text{?W}\text{?I}{}_2$ is positive, greater in magnitude than $\text{?W}\text{?I}{}_1$ and decreases towards zero with increasing time and deformation. These results were unexpected and a full understanding of their meaning has yet to be reached.     

Gel permeation chromatographic analysis of solubilized lignite asphaltenes and preasphaltenes

GPC data have been measured for a series of acetylated solvent refined lignite (SRL) asphaltenes and preasphaltenes and model compounds. Two structural parameters, the degree of aromatic condensation ($\text{H}{}_{\mathrm{aru}}\text{C}{}_{\mathrm{ar}}$) and the molar hydrogen to carbon ratio ($\text{H}\text{C}$), were employed to correct the molecular weight of the samples for linear molecular size. For the model compounds, $\text{H}{}_{\mathrm{aru}}\text{C}{}_{\mathrm{ar}}$ was more effective, whereas the SRL materials were better adjusted by $\text{H}\text{C}$. The calibration standards deemed most suitable for determination of molecular weight of SRL by GPC are the SRL samples themselves.     

Thermomechanical heat of deformation studies on cis-polybutadiene

Thermomechanical heat of torsional deformation measurements have been made on crosslinked cis-polybutadiene by means of a Calvet microcalorimeter operated at 30°C. When corrected for volume changes utilizing the Gaussian statistical theory of elasticity, the data gave a value for the relative energy contribution to the torsional couple, $\text{M}{}_{\mathrm{e}}\text{M}$, of 0.14 ± 0.02. Measurements were also made on a sample subjected to simple tensile deformations. The relative energy contribution to the tensile force ($\text{f}{}_{\mathrm{e}}\text{f}$) was found to agree within experimental error with the value obtained for $\text{M}{}_{\mathrm{e}}\text{M}$, and the two results gave an average value for din $\text{〈r}{}^2{}_0\text{〉}\text{d}\text{T}$ of 4.1 × 10^?4 K^?1.     

Effects of metal-support interactions on the synthesis of methanol over palladium

The synthesis of methanol and other products from CO and H₂ was studied over Pd catalysts prepared by adsorption of Pd(π-C₃H₃)₂ on MgO, ZnO, La₂O₃, γ-Al₂O₃, SiO₂, TiO₂, and ZrO₂ as well as over a SiO₂-supported Pd catalyst prepared from PdCl₂ and Pd black. Both the activity and selectivity of Pd were affected strongly by the nature of the support and the composition of the Pd precursor. The specific activity for methanol synthesis decreased in the order $\text{Pd}\text{La}{}_2\text{O}{}_3$ ? $\text{Pd}\text{SiO}{}_2$ [derived from PdCl₂] > $\text{Pd}\text{ZrO}{}_2$ > $\text{Pd}\text{ZnO}\text{≈}\text{Pd}\text{MgO}$ > PdTiO₂ > $\text{Pd}\text{Al}{}_2\text{O}{}_3\text{≈}\text{Pd}\text{SiO}{}_2$ [derived from Pd(π-C₃H₅)₂] ? Pd black, while the specific activity for hydrocarbon synthesis decreased in the order $\text{Pd}\text{TiO}{}_2\text{?}\text{Pd}\text{ZrO}{}_2$ > $\text{Pd}\text{La}{}_2\text{O}{}_3$ > $\text{Pd}\text{Al}{}_2\text{O}{}_3\text{≈}\text{Pd}\text{SiO}{}_2$ [derived from PdCl₂] ? $\text{Pd}\text{SiO}{}_2$ [derived from Pd(π-C₃3H₅)₂] ≈ Pd black ? $\text{Pd}\text{MgO}\text{?}\text{Pd}\text{ZnO}$. Dimethyl ether production was observed over four of the catalysts and the activity for formation of this product decreased in the order $\text{Pd}\text{Al}{}_2\text{O}{}_3\text{?}\text{Pd}\text{TiO}{}_2\text{?}\text{Pd}\text{MgO}\text{≈}\text{Pd}\text{ZrO}{}_2$. The effects of support composition on the catalytic properties of Pd are discussed in the light of current ideas concerning metal-support interactions and the acid-base properties of the support.     

Molecular weight distribution and stereoregularity of polypropylenes obtained with Ti(OC4H9)4Al2(C2H5)3Cl3 catalyst system

The effects of temperature and catalyst homogeneity on the molecular weight distribution (MWD) and stereochemical regulation of polypropylenes produced by $\text{Ti(OC}{}_4\text{H}{}_9\text{)}{}_4\text{Al}{}_2\text{(}\text{C}{}_2\text{H}{}_5\text{)}{}_3\text{Cl}{}_3$ system have been investigated. The MWD of polymers obtained at temperatures below 21°C were unimodal and narrow ($\text{M}\text{?}{}_{\mathrm{w}}\text{M}\text{?}{}_{\mathrm{n}}\text{?2.0}$), whereas those obtained at temperatures higher than 31°C were bimodal with one narrow distribution and the other broad one ($\text{M}\text{?}{}_{\mathrm{w}}\text{M}\text{?}{}_{\mathrm{n}}\text{=18}$) at higher molecular weights. The existence of two different types of catalyst, one soluble with homogeneous catalytic centres and the other insoluble with heterogeneous catalytic centres was found in the polymerization at 41°C. At temperatures below 21°C only soluble catalyst was present and produced isotactic polypropylenes with [m]=0.65. The isospecific nature of soluble titanium-based catalyst is greatly contrasted to the syndiospecific nature of soluble vanadium-based catalyst.     

Conversion of bituminous coal in COH2O systems: 2. pH Dependence

Under $\text{CO}\text{H}{}_2\text{O}$ systems at initial pH values s> 12.6, an Illinois No. 6 coal, PSOC-26, was converted to a fully pyridine-soluble product, with benzene and hexane solubilities of 50% and 18%, respectively. The product gases were H₂ and CO₂. However, the expected $\text{H}{}_2\text{CO}{}_2$ ratio of 1.0 based on the water gas shift reaction was not observed, but the deficit in hydrogen was found in the increased hydrogen content of the coal product. 95% coal carbon recovery and good hydrogen balances were obtained, and the coal products were found to be very similar to those from conventional tetralin systems. The results suggest an efficient base-catalysed process, and that $\text{CO}\text{H}{}_2\text{O}$ systems are useful for coal studies.     

Branched poly(ethylene terephthalate) correlations between viscosimetric properties and polymerization parameters

Samples of poly(ethylene terephthalate) (PET) modified with small amounts of trimesic acid groups and hence containing long chain branching have been prepared. From the content of trifunctional modifier and from the experimental value of the extent of reaction, the weight-average molecular weight $\text{M}\text{?}{}_{\mathrm{w}}$ and branching density $\text{B}\text{?}{}_{\mathrm{w}}$ have been calculated, assuming that all the end-groups are equally reactive and intramolecular reactions are absent. The values of $\text{M}\text{?}{}_{\mathrm{w}}$ and $\text{B}\text{?}{}_{\mathrm{w}}$ have been correlated with the experimental values of intrinsic viscosity [η] and the Newtonian melt viscosity η₀. General relations of the following type have been obtained:

$\text{f}{}_1\text{([η],}\text{M}{}_{\mathrm{w}}\text{,}\text{B}{}_{\mathrm{w}}\text{) = 0; f}{}_2\text{(η}{}_0\text{,}\text{M}{}_{\mathrm{w}}\text{,}\text{B}{}_{\mathrm{w}}\text{) =0; f}{}_3\text{(η}{}_0\text{, [η],}\text{B}{}_{\mathrm{w}}\text{) = 0; f}{}_4\text{(η}{}_0\text{, [η],}\text{M}{}_{\mathrm{w}}\text{) = 0;}$

In particular, [η] and η₀ increase on increasing $\text{M}\text{?}{}_{\mathrm{w}}$ and decrease on increasing $\text{B}\text{?}{}_{\mathrm{w}}$, but, at equal [η] values, η₀ increases with $\text{B}\text{?}{}_{\mathrm{w}}$. Through the last relation, the reliability limits of which should be experimentally checked, and from measurements of [η] and η₀, it is possible to calculate $\text{M}\text{?}{}_{\mathrm{w}}$ of a branched PET.     

Studies of cyclic and linear poly(dimethyl siloxanes): 2. Preparative gel permeation chromatography

A preparative gel permeation chromatographic (g.p.c.) instrument has been constructed and used to separate broad fractions of cyclic poly(dimethyl siloxanes) into sharp fractions with heterogeneity indices $\text{M}\text{?}{}_{\mathrm{w}}\text{M}\text{?}{}_{\mathrm{n}}\text{= 1.05 ± 0.02}$. The number-average molecular weights $\text{M}\text{?}{}_{\mathrm{n}}$ of the cyclic polymer fractions obtained were as high as 50 000, corresponding to number-average numbers of skeletal bonds $\text{n}\text{?}{}_{\mathrm{n}}$ up to 1300. The concentrations of linear poly(dimethyl siloxanes) in all but the highest molecular weight cyclic polymer fractions prepared are believed to be negligible. The preparative g.p.c. instrument was also used to obtain some sharp fractions of linear poly(dimethyl siloxanes).     

Cloud-point curves of the polystyrene-cyclohexane system near the critical point

Cloud-point curves for solutions of five polystyrene samples, including three well-fractionated polystyrenes, in cyclohexane have been examined near their critical points. Even for a solution of polystyrene characterized by $\text{M}{}_{\mathrm{w}}\text{M}{}_{\mathrm{n}}\text{<1.03}$, the critical point determined by the phase-volume method is generally situated on the right hand branch of the cloud-point curve. The precipitation threshold concentration is appreciably lower than the critical concentration, while the threshold temperature slightly deviates from the critical temperature. The agreement of the precipitation threshold point with the critical point has been found for a solution of polystyrene characterized by M_w=20×10⁴ and $\text{M}{}_{\mathrm{w}}\text{M}{}_{\mathrm{n}}\text{<1.02}$ in cyclohexane. The η(φ) function derived from critical miscibility data is expressed by $\text{χ(φ) = 0.2798+}\text{67.50}\text{T}\text{+0.3070φ+0.2589φ}{}^2$, which yields θ of 33.2°C and ψ₁ of 0.22.     

Solvent self-diffusion in semidilute polystyrene solutions. Pulsed-gradient spin-echo measurements on a standard Fourier transform n.m.r. spectrometer

Measurements of solvent self-diffusion coefficients in the systems polystyrene/dichloromethane and polystyrene/cyclopentane recorded on a standard Fourier transform n.m.r. spectrometer are reported. The ratio $\text{D}{}_{\mathrm{s}}\text{D}{}_{\mathrm{s,0}}$ was found to decrease linearly with increasing volume fraction of polystyrene, over the interval studied (ø_PS<0.27), for both systems. For PS/cyclopentane an increase in temperature from 12.5°C (close to UCST) to 40°C was not found to alter the concentration dependence of the ratio $\text{D}{}_{\mathrm{s}}\text{D}{}_{\mathrm{s,0}}$ significantly.