Conversion of bituminous coal in COH2O systems: 3. Soluble metal catalysis

The oxyanions of the highest oxidation states of several transition metals, including W, Mo, Cr and Mn, were found to catalyse the liquefaction of Illinois No. 6 coal in $\text{CO}\text{H}{}_2\text{O}$ systems at 400°C. Unlike the high pH (s> 12) required in the base-catalysed system, the effective range for these metal-mediated conversions extend down to pH < 5.0. The benzene-soluble product was found to have a higher $\text{H}\text{C}$ ratio than the starting coal, and the metals were reduced to water-insoluble, lower oxidation states during conversion. A chain scheme is suggested as an explanation for the data.     

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.     

In situ laser raman spectroscopy of the sulfiding of Moγ-Al2O3 catalysts

Raman spectra of sulfided $\text{Mo}\text{γ-}\text{Al}{}_2\text{O}{}_3$ catalysts were obtained using in situ techniques for two sulfiding methods. For samples sulfided by 10% $\text{H}{}_2\text{S}\text{H}{}_2$ at 400 °C, MoS₂ structures were observed. A stepwise sulfiding using 10% $\text{H}{}_2\text{S}\text{H}{}_2$, with spectra recorded at 150, 250, and 350 °C, resulted in observation of molybdenum oxysulfide, reduced molybdate, and surface “MoS₂” phases. Reexposure of these samples to air led to radical modification of the oxysulfide structures as well as transformation of some sulfide phases. A model incorporating terminal and bridging MoS bonding and anion vacancies is proposed. This model is based on the conversion of isolated and aggregated molybdate and MoO₃ species to oxysulfide and reduced molybdenum phases. Conversion of reduced molybdenum phases to sulfides is observed to be slow.     

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.     

Reinvestigation of the system C4A.nH2O  C4A.Co2.nH2O

The system C₄A.nH₂O  C₄A.CO₂.nH₂O has been reinvestigated at 22°, 100 % and 65 % relative humidity. Formation conditions, composition and crystallographic properties of the phases C₄A.nH₂O, C₄A.1/2CO₂.nH₂O, C₄A.CO₂nH₂O and their dehydration products have been studied by X-ray and elektron diffraction, infrared and Raman spectroscopy, dynamic weight-loss curves and differential thermal analysis. Only very limited solid solution occurs in the system. X-ray single crystal studies showed the quaternary compound C₄A.1/2CO₂.12H₂O to be trigonal with space group R3c or R$\text{3}$c, lattice parameters $\text{a}{}_{\mathrm{o}}\text{=5.77}\text{a}\text{?}\text{,}\text{C}{}_{\mathrm{<mtext>o</mtext>}}\text{=49.16}\text{a}\text{?}$. C₄A.CO₂11H₂O is triclinic with $\text{a}{}_{\mathrm{o}}\text{=5,}{}_{\mathrm{o}}\text{=5.74}\text{A}\text{?}\text{,}\text{C}{}_{\mathrm{o}}\text{=7.86}\text{A}\text{?}\text{α=92.61°, β=101.96°, δ=120.09°}$. Indexed powder diffraction data of both compounds are given.     

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 $\text{Pd}\text{SiO}{}_2$.     

Assessment of the activities of catalysts for the hydrocracking of coal by means of hydrogen evolution

A close relation has been found between hydrogen evolution from coal-catalyst and pitch-catalyst systems and catalytic activities of liquefaction reactions. A MoO₃?TiO₂ catalyst has the highest activity and the order of activity of the catalysts for hydrogen evolution is: MoO₃?TiO₃> MoO₃?SiO₂>10% $\text{Fe}{}_2\text{O}{}_3\text{TiO}{}_2\text{?AI}{}_2\text{O}{}_3\text{>}\text{coal alone}$. The same trend was observed for benzene-soluble materials for the hydrocracking of Akabira Coal.     

Selectivity for nitrogen formation in NH3 oxidation in wet and dry systems over mixed molybdenum oxides

To overcome the problem of NH₃ formation and reoxidation to NO in automotive dual catalytic systems, it has been suggested to use mixed base metal oxides for the conversion of NH₃ to N₂. The present work reexamines this suggestion and the effect of the prevailing high $\text{H}{}_2\text{O}\text{NH}{}_3$ ratio in the exhaust stream on its applicability. It has been found that, at high $\text{H}{}_2\text{O}\text{NH}{}_3$ ratio in the treated gas, the range of conditions under which the formation of NN bonds prevails is drastically narrowed. The behavior of copper, cobalt and iron molybdates in this surface reaction was examined and that of the copper molybdate was compared with the activity and selectivity of the pure oxides-CuO and MoO₃.     

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.     

Highly conducting polymers based on polyacetylene hydrogen sulphate: Preparation and stability studies

Oxidation of polyacetylene with sulphuric acid, leading to the formation of highly conducting polymer films, was studied under varying conditions. It was found that the highest quality films were obtained in the gas phase reaction with 98% H₂SO₄ where the $\text{H}{}_2\text{SO}{}_4\text{H}{}_2\text{O}$ ratio is crucial for correct doping. The reaction product can be formulated as [CH(HSO₄)_y]_x. Oxygen attack leads to the irreversible degradation of the polyene chain and reaction with H₂O results in compensation of the dopant anions.     

Stabilization effect of Co for Mo phase in CoMoAl2O3 hydrodesulfurization catalysts studied with X-Ray photoelectron spectroscopy

The promotional effects of Co in $\text{CoMo}\text{Al}{}_2\text{O}{}_3$ hydrodesulfurization (HDS) catalysts were studied by means of X-ray photoelectron spectroscopy. The higher MoO₃-content $\text{Mo}\text{Al}{}_2\text{O}{}_3$ catalysts (10 and 20 wt% MoO₃) contain mobile Mo, which migrates from the pores to the outermost surface layers of the catalysts and segregates to form less active crystalline MoS₂ during the HDS reaction, while in the case of $\text{Mo}\text{Al}{}_2\text{O}{}_3$ (5 wt% MoO₃) catalyst: no migration of Mo was observed. It is revealed that the Co in $\text{CoMo}\text{Al}{}_2\text{O}{}_3$ catalyst inhibits the migration and segregation of Mo and that it keeps Mo effective for the HDS reaction, since no surface enrichment of Mo was observed. It is concluded that stabilization of the Mo monomolecular layer is the main role of Co. The active species of Mo is suggested to have the composition of S/Mo(IV) = 1 on the basis of the sulfur contents of the catalysts under the mild HDS reaction conditions.     

The kinetics of the catalytic hydrogenolysis of ethane over Ni/SiO2

The rate of hydrogenolysis of ethane over a Ni/SiO₂ catalyst, studied over a large range of pressure and of temperature, is shown to be related to the degree of hydrogen coverage θ_H, by the equation: with K₀ nearly equal to the number of ethane molecules colliding with the Ni surface, E₀ = 14 ? 1 kcal/mole, Y = ?1 ? 2 and X = 15 ? 2. The rate-limiting step is believed to be the irreversible, dissociative adsorption of ethane on an ensemble of at least 12 adjacent Ni atoms, free from adsorbed hydrogen, resulting in the complete cracking of C₂H₆: C₂H₆ + 12Ni → 2

Irreversible adsorption of ethane is assumed to compete with the reversible adsorption of hydrogen. This mechanism, which is compared with those proposed earlier, is in good agreement with data on ethane adsorption studied by magnetic methods, and with a study of ethane hydrogenolysis over NiCu/SiO₂ catalysts.     

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.     

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.     

Tensile deformation of polychlorotrifluoroethylene in He,N2, Ar,O2, and CO2 environments

The tensile stress—strain behaviour of quenched polychlorotrifluoroethylene (PCTFE) was measured from 77K to T_g in gaseous environments of He, N₂, Ar, O₂, and CO₂ and in water. The partial pressure of the gas was varied from 0 to 1 atm. N₂, Ar, O₂ and CO₂ produced crazing and a lowering of the tensile strength relative to the intrinsic tensile strength at that temperature. The effect of pressure and temperature on the tensile strength was quantitatively similar to the effect of these gases on PC and PMMA, and could be described by an equation of the form: $\text{σ}{}_{\mathrm{c}}\text{σ}{}_{\mathrm{i}}\text{= [P}\text{exp}\text{(}\text{Q}\text{RT}\text{/P1]}{}^{\mathrm{?0.10}}$. The constants Q and $\text{P1}$ depended on the gas, and σ_i is the intrinsic strength. The Q values were approximately the same as the heat of vaporization for each gas. CO₂ produces crazing below as well as above its sublimation temperature. The intrinsic yield point varied from 0.033 to 0.054 of E, Young's modulus, as the temperature varied from 300 to 77K. The experimental value of the yield point extrapolated to 0.055E at OK and compares favourably with existing theories for the yield point of glassy polymers.     

Macerals in bituminous coals and the coking process: 2. Coal mass properties and coke mechanical properties

Bituminous coals produced in the Ostrava-Karviná coal basin show considerable variation in their maceral composition, vitrinite reflectance and fluidity. There is a close association of the latter with the $\text{H}\text{O}$ atomic ratio expressing the different chemico-structural properties of vitrinites of lower coalification. These properties of the coal mass all influence the coke mechanical properties; moreover the $\text{H}\text{O}{}_{\mathrm{at}}$ parameter is of principal importance to the course of the coking process. Laboratory, pilot-plant and full-scale experiments show that coals rich in inertinite may give cokes of suitable mechanical properties, providing the $\text{H}\text{O}{}_{\mathrm{at}}$, ratio and the bulk density are high enough. It should be noted, however, that these coals contain finely dispersed inertinite in the vitrinite mass and this may have a positive effect on the coke mechanical properties.     

Relation of the chemical structure of coal to its hydropyrolysis

The hydropyrolysis of Illinois No. 6 coal has been studied in a batch reactor, in which the reactions were initiated by explosion of $\text{H}{}_2\text{O}{}_2$ mixtures. The ratio of H₂ to O₂ was kept at 8, while the total pressure of the gas mixture was changed to vary the reaction temperature. The heating rate was ≈ 50 000 °C s^?1, and the reaction time was < 50 ms. The conversion of the feed coal increased from 19% at 620 °C to 81%at ? 1500 °C. At conversions < 50%, the gaseous product consisted of mainly CH₄ and CO in almost equal proportions, and at conversions ? 60% the concentration of CO increased. Comparison with results from a large flow reactor revealed that comparable conversions were obtained in the present batch reactor, although product distributions were markedly different from each other. The dissimilar product distribution is attributed to different reacting media: preburning of H₂ and O₂ in the flow reactor versus in situ burning of the mixture in the batch reactor. The H/C ratios of solid residues after the hydropyrolysis decreased linearly as the conversion increased, revealing that the portions of coal having high H/C ratios were preferentially gasified. This observation was substantiated by a high H/C ratio, 1.74 of the first portion of coal gasified, and by a sharp decrease in H/C ratio in subsequent gasified portions. These data indicated that aliphatic side chains (or linkages) and single-ring aromatic clusters in the feed coal were gasified first, followed by larger aromatic clusters. Semi-quantitative determination of the distribution of different aromatic clusters showed good agreement with current structural information on coal. Thus, the effects of reaction variables were explained in terms of the structural features of coal, and the ratelimiting steps in the hydropyrolysis process were identified.     

Thermoplastic properties of coal at elevated pressures: 1. Evaluation of a high-pressure microdilatometer

Thermoplastic behaviour of a Pittsburgh seam hvA coal (PSOC1099) was characterized by the use of a high-pressure microdilatometer. Phenomena such as softening, swelling, final resolidification, and the temperatures at which they occur were measured as functions of heating rate (25 ° and 65 °C min^?1), particle size (= 75 μm and 250 × 425 μm), gaseous atmosphere (N₂, H₂, $\text{CO}\text{H}{}_2$) and applied gas pressure (atmospheric to 2.8 M Pa). The results obtained illustrate several important aspects of thermoplastic properties of this coal under the conditions utilized. It is observed that pressure alone can play a major role in determining its overall thermoplastic behaviour. Compared to that at atmospheric pressure, swelling is significantly reduced at 2.8 MPa of pressure for any given heating rate or particle size. In these experiments, the chemical composition of the gaseous atmospheres ($\text{CO}\text{H}{}_2$, H₂ and N₂) does not appear to alter significantly the plastic phenomena at any given pressure. Increasing the heating rate or decreasing the particle size results in increased swelling at all applied pressures and atmospheres.