To better understand the effect of inherent minerals in oil shale on the pyrolysis behavior of organic matter, Chinese Yilan oil shale is used as the raw material and its minerals are removed sequentially by stepwise acid treatment. The resulting samples are subjected to pyrolysis experiment on a thermogravimetric analyzer coupled with a mass spectrometer (TG–MS), and the effect of acid treatments on the organic matter structure is investigated by Fourier transform infrared (FTIR) and 13C nuclear magnetic resonance (NMR). It is found that the acid treatments have little effect on the structure of organic matter, except oxidation of a tiny amount of aliphatic carbons to carboxyl by HNO3. Inherent calcite, iron oxide, and pyrite in the minerals, with contents of about 0.64, 2.63, and 0.60 wt %, respectively, have obvious catalytic effects on the decomposition of the organic matter. Acid treatment by HF + HCl increases the mass loss of organic matter during pyrolysis but decreases the formation of C2H4, C3H8, C4H10, C6H6, C7H8, and C6H6O. Quartz and kaolinite removed by HF + HCl treatment were reported to have little effect on the pyrolysis process; therefore, inherent montmorillonite may promote the reaction of organic volatiles to form coke and gas.

Coal/char catalytic hydrogasification (CCHG) is a direct method to produce CH4 (synthetic natural gas, SNG). CaO has been studied as a promoter of transition metal compound catalysts for this process for decades. Our earlier work indicated that CaO alone has a high catalytic activity in CCHG as long as the temperature is higher than 750 °C and the Ca loading is higher than 0.42 mmol/(g of char). Our recent work and literature review indicate that the high activity of CaO may be related to the iron in ash of the char used, and the threshold loading of CaO may be attributed to the presence of sulfur in the char. This work aims to address these issues particularly on synergetic catalysis of Fe−CaO and transformation of Fe−CaO−S during the hydrogasification. All the hydrogasification experiments were performed in a fixed-bed reactor at 800 °C and under a H2 pressure of 1.5 MPa. Results indicate that both CaO alone and metallic Fe alone have little catalytic activity, but interaction of them yields a high activity. In this sense, CaO is not a catalyst promoter reported in the literature but a crucial catalytic component. The amount of Fe to fully excite the catalysis of 0.710 mmol of CaO is around 0.170 mmol, while the amount of CaO to fully excite the catalysis of 0.084 mmol of Fe is around 0.310 mmol. To yield a high catalytic activity, the optimum CaO/Fe molar ratio is around 4.0. The synergetic catalysis of Fe−CaO transforms from the CaO-dominate sites to Fe-dominate sites during hydrogasification, possibly due to differences in diffusion of Fe and CaO.

•The quantities of total radicals and bonds cleaved at 380–440 °C are determined.•The bond cleavage can be described by first-order reaction.•The amounts of total and stable radicals show a good linear relation.•Coupling of around 2500 active radicals yields one stable radical.•Not all the bond cleavage results in a mass loss.Pyrolysis of an oil shale starts with cleavage of covalent bonds to generate radical fragments which is followed by coupling of the radical fragments to form volatiles (shale oil and gas) and char. The radical’s reaction determines the distribution, composition and quality of pyrolysis products. However, information about the bond cleavage and the radicals’ reaction during oil shale pyrolysis is very limited in the literature. This paper studies the quantities of total radicals and bonds cleaved in pyrolysis of the organic matter in Huadian oil shale (HDOM) at 380–440 °C. The kinetics of the bond cleavage is established and the behavior of radicals’ coupling is discussed. It is found that the quantities of cleavable bonds in HDOM are 0.62 × 10−2, 0.87 × 10−2, 1.10 × 10−2 and 1.33 × 10−2 mol/g at 380, 400, 420 and 440 °C, respectively. The bond cleavage can be described by the 1st-order reaction kinetics with an activation energy (Ea) of about 90.10 kJ/mol and a pre-exponential factor of 5.23 × 105 min−1. Since not all the bond cleavage yields a mass loss, the activation energy determined for the bond cleavage is different from that for the devolatilization reported in the literature. The number of stable radicals confined in the pyrolysis products shows a good linear relation with that of total radicals generated during pyrolysis and one stable radical is formed among around 2500 radicals generated from HDOM.

Oil shale has been pyrolyzed for shale oil in industry to alleviate the shortage of petroleum in many countries. Some oil shales appear non-uniform in colour, suggesting different ash content and/or organic structure distribution throughout their deposition. This paper takes Yilan oil shale as the raw material to identify the structure and pyrolysis behaviour of the organic matter in fractions of different colour. The oil shale is separated into two parts by a heavy liquid flotation method and then subjected to acid treatments. The heavy part is gray and termed as YL-G-OM, while the light part is black and termed as YL-B-OM. These parts are characterized by proximate and ultimate analyses and 13C-nuclear magnetic resonance. Pyrolysis experiments are carried out in a TG-MS and a fixed-bed tubular reactor. The liquid product from the tubular reactor is analyzed by GC–MS and simulated distillation. Results indicate that the H/C ratios of YL-G-OM and YL-B-OM are 1.21 and 0.95, respectively. In comparison with YL-B-OM, YL-G-OM contains more aliphatic carbon and less aromatic carbon, and has a longer methylene chain and a lower condensation degree, which results in more liquid product and C2-C3 gas during pyrolysis. The yields of liquid product are 46.1 and 35.6% on daf basis for YL-G-OM and YL-B-OM, respectively. The liquid products of both samples contain about 80% heavy fractions including those trapped in the GC column, vacuum residue and vacuum gas oil, as well as some diesel (12.5–17.0%) and a little gasoline (3.3–4.3%). Co-pyrolysis of YL-G-OM and YL-B-OM shows a synergetic effect at temperatures between 425 and 460 °C, which promotes formation of liquid product and reduces the phenolic content in shale oil. The synergetic effect may be attributed to reduced condensation of radical fragments generated by bond cleavage of organic matter.

Carbon-based materials have been used for SO2 removal from flue gases for several decades. In this process, SO2 is captured by storing in the pores of carbons in the form of H2SO4, and regeneration of the SO2-captured materials is necessary to recover SO2 capture ability. V2O5-supported activated coke (V2O5/AC) has been reported to be highly active for SO2 removal, and its regeneration has been investigated from the viewpoint of the reaction mechanism. This work studied the regeneration kinetics with the aid of a thermogravimetric analyzer coupled with a mass spectrometer. The SO2-captured sample was prepared in a fixed-bed reactor with a simulated flue gas containing 1500 ppm of SO2, 5% O2, and 5% H2O. The kinetic equation was obtained by fitting the H2SO4 conversion (α) at different heating rates with nonisothermal kinetic methods called Flynn–Wall–Ozawa and Coats–Redfern. The results indicated that the regeneration kinetic behavior varies with α. At α = 0.1–0.4, regeneration follows first-order reaction model f(α) = 1 – α with an activation energy of about 85.7 kJ/mol. At α = 0.5–0.8, regeneration follows three-dimensional diffusion model f(α) = 1.5(1 – α)2/3[1 – (1 – α)1/3]−1, with the activation energy increasing from 88.9 kJ/mol at α = 0.5 to 112.1 kJ/mol at α = 0.8.

Recovery of vanadium from various sources is important to the environment and industry. This work investigates vanadium leaching from a spent selective catalytic reduction catalyst by sulfuric acid at atmospheric pressure. It includes the effects of stirring speed, solid to liquid ratio, temperature, and sulfuric acid concentration on the vanadium recovery yield. The results show that the vanadium recovery yield increases with increases in temperature, sulfuric acid concentration, and leaching time and decreases with an increase in solid to liquid ratio. The leaching data can not be described well by kinetic models commonly adopted for similar processes in the literature. The Avrami equation, originally developed for crystallization, is found to be most suitable. The leaching is controlled by diffusion in the solid with an activation energy of 5.90 kJ/mol.

The role of SO2 in the selective catalytic reduction (SCR) of NO by NH3 over carbon-based catalysts has been studied by many researchers over the past decade. It has been reported to be positive by some but negative by others. This work examines the multiple roles of SO2 during SCR over V2O5/AC catalyst in the presence of H2O and identifies the effects of the AC source and reaction conditions on the role of SO2. The multiple roles of SO2 can include its competitive adsorption with reactants for V2O5 on the catalyst, its interaction with V2O5 to form VOSO4, and pore blockage and surface modification through the formation of ammonia sulfates from the reaction of SO2 and O2 + H2O + NH3. It was found that competitive adsorption cannot be confirmed, but VOSO4 was observed in the used catalyst. A tiny amount of VOSO4 might result in a sharp decrease in NO conversion. The negative effect of SO2 through VOSO4 formation weakens with increasing SCR temperature and decreasing AC surface area. Pore blockage has little influence on the SCR activity at temperatures of 200 °C and higher. The surface modification is positive to the SCR for V2O5/AC made from anthracite-derived AC but negative for V2O5/AC derived from other sources. However, the positive effect of surface modification is overwhelmed by the negative effect of gaseous SO2, which results in an overall negative effect of SO2.

Much research has shown that V2O5/AC is promising for the selective catalytic reduction (SCR) of NO with NH3 at low temperatures (180−250 °C). However, information on N2O formation and AC oxidation during the SCR process are limited especially under actual conditions in the presence of SO2 and H2O. These are studied in this work through specially designed experiments. Results show that under the conditions used, V2O5 loading, reaction temperature, and SO2 concentration have limited effects on N2O formation. N2O is generated from reduction of NO by both AC and NH3. SCR selectivity to N2 is promoted by V2O5, and less than 1 wt.% V2O5 is sufficient to yield a N2 selectivity of higher than 95%. Oxidation of AC to CO2 is promoted by temperature and SO2 and originates mainly from reaction of carbon-and-oxygen-containing functional groups with sulfuric acid formed from SO2 adsorption in the presence of SO2.