Amount Of Coke Research Articles

Development of Silicalite-1-encapsulated Ni nanoparticle catalyst from amorphous silica-coated Ni for dry reforming of methane: Achieving coke formation suppression and high thermal stability

Dry reforming of methane (DRM) is an important reaction for converting CO2 into synthesis gas (H2 + CO). Though Ni is one of the most promising catalysts, the agglomeration of Ni particles and the formation of coke on the catalyst proceed during DRM, resulting in rapid catalyst deactivation. Therefore, the development of Ni-based catalysts that exhibit high thermal stability and suppress coke formation is indispensable. The encapsulation structure of Ni nanoparticles in porous supports is reported to be effective for high DRM activities and the suppression of coke formation.Herein, we synthesized a Silicalite-1-encapsulated Ni catalyst (Ni@Silicalite-1) for DRM using amorphous silica-encapsulated Ni-oxide nanoparticles (NiOx@SiO2) as the Ni precursor, and the effect of physicochemical properties on DRM activities was investigated using Ni@Silicalite-1, Ni@SiO2 (NiOx@SiO2 after H2 reduction), and Ni/Silicalite-1 (impregnation). For Ni@Silicalite-1, Ni phyllosilicate was formed inside Silicalite-1 during the hydrothermal synthesis, and the encapsulation structure of 4.5-nm-sized Ni particles was realized by reducing Ni phyllosilicate to Ni particles inside the zeolite. Because the small Ni particles were stabilized in the porous supports, Ni@Silicalite-1 and Ni@SiO2 exhibited high and stable activity for DRM at 600 °C with negligible coke formation (6.6 and 8.2 mg-C/g-catalyst for Ni@Silicalite-1 and Ni@SiO2 respectively), whereas a large amount of coke was formed on Ni/Silicalite-1 (532 mg-C/g-catalyst). Ni@Silicalite-1 exhibited high and stable DRM activity throughout 24 h at 600 °C and GHSV = 108000 mL/(g-cat·h). Moreover, because Silicalite1 possessed high thermal stability, the high activity of Ni@Silicalite-1 was maintained throughout the 5 h of DRM at 850 °C, whereas the activity of Ni@SiO2 decreased because of the collapse of the pore structure of SiO2. Ni@Silicalite1 exhibited a higher conversion rate of methane (13.3 mol-CH4/(g-Ni·min) at 850 °C and GHSV = 1080000 mL/(g-cat·h)) than previously reported Ni-based catalysts.

Steam reforming of sugar and its derivatives: Functionality dictates thermal properties and morphologies of coke

Coking is a major challenge in steam reforming of oxygenated organics, especially the ones in bio-oil with multiple oxygen-containing functionalities. The property of the resulting coke is believed to relate with structures of the organics. In this study, steam reforming of xylose, xylitol and furfural, which are representatives of sugars, alcohols of multiple hydroxyl groups, and furans, were performed to correlate molecular structure and property of coke. The results showed that xylose polymerized rapidly during the steam reforming, forming initially π-conjugated polymeric organics and substantial amount of coke that was amorphous, aliphatic, thermally unstable with abundant olefin C = C and –OH. In comparison, steam reforming of xylitol generated little coke, as xylitol contains no C = O that was the primary reason for the serious coking in xylose reforming. Steam reforming of furfural also generated large amount of coke that was mainly aromatic with high thermal stability and high resistance towards oxidation, due to the reserve of the furan ring-like structure in the coke. Functionalities of the reactants dictated the thermal properties of the coke and also their morphologies. The amorphous coke formed in xylose reforming was bubble-like, while the coke in furfural reforming mainly included carbon nanofiber of rugged surface and carbon nanotubes of thick wall. The multiple hydroxyl groups in xylitol, however, resulted in the coke of carbon nanotube form with large inner diameters.

Progress of the Catalytic Deactivation of H‐ZSM‐5 Zeolite in Glycerol Dehydration

AbstractGlycerol conversion into value‐added chemicals has received much attention due to the prospect of increasing the biodiesel industry‘s profitability. The dehydration of glycerol is one of the most explored reactions in the valorization of glycerol, and the zeolite H‐ZSM‐5 is one of the furthermost used structures. In this study, several characterization techniques were used to investigate the detailed aging of coke in spent H‐ZSM‐5 zeolites after their use in the gas‐phase glycerol dehydration to produce acrolein. The carbonaceous deposits formed almost totally in the first minutes of the reaction. They rapidly got trapped inside the pores, hampering the accessibility to active sites and the zeolite‘s full catalytic action. Two types of coke were formed during the reaction: polyglycols, on the external surface, and aromatics, inside the pores, representing the majority (∼98 wt.%) of the carbonaceous compounds. Besides, aromatic compounds age over time, becoming bulkier and more deficient in hydrogen. We also found a correlation between the amount of coke, its size, accessibility to the acid active sites, and changes in crystallographic parameters of the zeolite with the presence of coke.

A LaFeO3 supported natural‐clay‐mineral catalyst for efficient pyrolysis of polypropylene plastic material

AbstractThe pyrolysis and catalytic reforming process of waste plastics are the best pathways to handle vast amounts of waste plastics as they can convert these waste polymers into sustainable products. This study aims to incorporate a natural‐clay‐mineral (NCM) with LaFeO3 nanoparticles, with the LaFeO3/NCM catalyst in the pyrolysis of polypropylene (PP) being used as an example of plastic waste. The decomposition of PP with and without catalyst has been theoretically studied using thermogravimetry (TG) and differential scanning calorimetry (DSC) measurements under atmospheric pressure and nitrogen atmosphere. The TG/DSC results show that (i) the required temperature for pyrolysis of PP with or without catalyst in a practical system ranges from 460°C to 480°C; (ii) the amount of coke produced on the surface of the NCM or LaFeO3 is about 2 wt.% compared with the initial plastic levels; (iii) with the catalyst, PP not only goes through the phase transitions of solid to liquid to gas but also decomposition and combination processes between components from the hydrocarbon chain scission of PP. Gas chromatography–mass spectrometry (GC–MS) results show significant differences in the fuel oil recovered from the pyrolysis and catalytic reforming process. In the presence of the catalyst, cracking components consist of 49.3% alkenes (branched‐chain alkenes, cyclo‐alkenes, and alkenes) and 34.4% alkanes, while without the catalyst, branched‐chain alkenes were up to 90.2%. Repeated pyrolysis and GC–MS investigations demonstrated the reusability of the LaFeO3/NCM catalyst, which is promising for its recycling and the efficient pyrolysis of PP.

Catalytic fast pyrolysis of beech wood lignin isolated by different biomass (pre)treatment processes: Organosolv, hydrothermal and enzymatic hydrolysis

Lignin is one of the three main structural components of lignocellulosic biomass and is considered as the most abundant source of aromatic and phenolic compounds. Lignin is produced as side-stream in the pulp/paper industry or as residue in the production of second-generation bioethanol. More recently, novel biomass fractionation processes in biorefineries have been developed aiming at the production of high quality/purity lignin towards its more efficient down-stream catalytic conversion to chemicals, monomers, and fuels. Within this context, in this work, we studied the thermal (non-catalytic) and catalytic fast pyrolysis on a Py/GC–MS system and a fixed-bed reactor unit of three types of lignin, all originating from the same biomass (beech wood sawdust) but with different isolation processes: organosolv lignin derived by the organosolv pretreatment/fractionation of biomass, surface extracted lignin derived by the mild Soxhlet extraction (with ethanol or acetone) from the hydrothermally (HT) in pure water pretreated biomass, and the enzymatic hydrolysis lignin derived as a lignin-rich solid residue from the enzymatic hydrolysis of the HT pretreated biomass. Conventional microporous ZSM-5 and mesoporous ZSM-5 zeolites (with intracrystal mesopores, ˜ 9 nm) were used as catalysts in the pyrolysis experiments. Both zeolites were very active in converting the initially produced via thermal pyrolysis methoxy-substituted phenols, benzenes and benzaldehydes mainly towards BTX mono-aromatics, such as 1,3-dimethylbenzene/p- and o-xylenes, toluene and trimethylbenzenes, as well as polycyclic aromatic hydrocarbons (PAHs, mainly naphthalenes). The mesoporous ZSM-5 induced higher dealkoxylation reactivity compared to the microporous ZSM-5 leading to higher concentration of BTX aromatics without a consequent increase of PAHs. The pronounced dealkoxylation/aromatization reactivity of both ZSM-5 zeolites resulted to lower yields (but highly aromatic) organic bio-oils (e.g. from 32−35 wt.% to 15−22 wt.%) compared to thermal pyrolysis, increased non-condensable gases (mainly CO, CO2, methane, ethylene and propylene) and formation of relatively low amounts of coke on catalysts (e.g. 3−5 wt.% on lignin) in addition to thermal pyrolysis char. The observed moderate variations in the characteristics of the three types of beech wood lignin, i.e. molecular weight (GPC), S/G ratio, inter-unit linkages (2D HSQC NMR) and elemental composition, did not induce a systematic/substantial differentiation in the thermal and catalytic fast pyrolysis product yields and composition.

Comparison and Synthesis of Molybdenum Carbonyl Complexes Substituted with Mono- and Bis-Triphenylphosphine Ligands for Hydrocracking of Vacuum Residue.

(PPh₃)Mo(CO)5 and (PPh₃)₂Mo(CO)₄ were synthesized by the reaction of molybdenum hexacar-bonyl with triphenylphosphine and applied as precursors to hydrocracking of vacuum residue under high-pressure and high-temperature conditions. (PPh₃)₂Mo(CO)₄ could also be synthesized by the reaction of (PPh₃)Mo(CO)5 with triphenyl phosphine. A commercial precursor (Mo-octoate) for hydrocracking of vacuum residue was used for comparison. The thermal decomposition behavior of (PPh₃)Mo(CO)5, (PPh₃)₂Mo(CO)₄, and Mo-octoate was also examined by the thermogravimetric analysis. The TGA curve of (PPh₃)Mo(CO)5 and (PPh₃)₂Mo(CO)₄ showed a similar weight-loss pattern. (PPh₃)Mo(CO)5 and (PPh₃)₂Mo(CO)₄ were decomposed into Mo metal and ligands rapidly in the range of 140 °C~270 °C. There were no ligands bound to a metal center of (PPh₃)Mo(CO)5 and (PPh₃)₂Mo(CO)₄ at the reaction temperature (430 °C) of hydrocracking. The amount of coke formed after hydrocracking over (PPh₃)Mo(CO)5 and (PPh₃)₂Mo(CO)₄ was 2.3% and 0.5%, respectively. Upgrading the qualities of heavy oils is an important issue in the energy industry. It is not easy to achieve the complete conversion of vacuum residue due to coke forming during hydrocracking of vacuum residue. This study showed that (PPh₃)₂Mo(CO)₄ was considerably effective in reducing coke formation.

Acidity tuning of HZSM-5 zeolite by neutralization titration for coke inhibition in supercritical catalytic cracking of n-dodecane

Reducing the acid density and strength of HZSM-5 zeolite are typical strategies to inhibit coke deposition during catalytic cracking reactions. Herein, direct titration of HZSM-5/H2O suspension using dilute NaOH aqueous solution at room temperature was introduced to neutralize excessive Brønsted acid sites of HZSM-5 zeolite (Si/Al = 25). SEM, XRD, N2 adsorption and n-propylamine temperature-programmed decomposition confirmed that simultaneous acid strength weakening and acid density reducing were achieved without obvious influence on crystalline or textural property. The evolution of the surface charge during the titration process tracked by Zeta-potential measurement reveals that the mechanism of such neutralization is: liquid phase neutralization between H+ and OH− & solid phase ion exchange between Na+ and H+. Supercritical catalytic cracking of n-dodecane over a series of partial neutralized HZSM-5 catalysts showed that moderate neutralization can enhance the conversion of n-dodecane by alleviating both the coke amount and harmfulness per unit mass of coke.

Dimethyl ether conversion to light olefins in slurry and fixed‐bed reactors: coke nature and location on Mg/ZSM‐5 catalyst

AbstractBACKGROUNDThe goal of this study was to investigate the deactivation of ZSM‐5 in the DTO process (dimethyl ether to light olefins) in a slurry reactor (SLR) in polydimethylsiloxane dispersion medium compared with its deactivation in a fixed‐bed reactor (FBR), and to unveil reasons behind the rapid deactivation of the catalyst in the SLR.RESULTSUnder suspension conditions coke formation proceeds more slowly compared with fixed‐bed conditions: The amount of coke formed under suspension conditions is less than under fixed‐bed conditions, 1.4 mg versus 1.7 mg, respectively. Also, in terms of the chemical composition the coke is lighter (xylenes and trimethylbenzenes versus С4,5,6‐substituted benzenes). Using thermogravimetric analysis and gas chromatography/mass spectrometry pyrolytic system, it was shown that the decomposition products of the dispersion medium contribute to the blocking of micropores and the rapid deactivation of the catalyst in SLR. The localization of coke in both SLR and FBR occurs primarily in the microporous channels of the zeolite (>60%). In SLR, the weight fraction of coke on the external catalyst surface was 11% higher than that on the FBR. This finding can be attributed to the blocking of micropores by decomposition products of the dispersion medium.CONCLUSIONUnder suspension conditions, сoke formation in the DTO process proceeds more slowly compared with fixed‐bed conditions. The rapid loss of catalyst activity in the SLR was related not to coke formation, but instead to the blocking of catalyst pores by products of thermal decomposition of the dispersion medium. For the same reason, in SLR the weight fraction of coke on the external surface of the catalyst was higher than that in the FBR. © 2021 Society of Chemical Industry (SCI).

Coke formation on activated carbon during catalytic upgrading of coal pyrolysis volatiles

The content of heavy pitch in tar generated from coal pyrolysis is high. To improve the quality of tar, catalysts are applied for adjusting the reaction of volatiles during coal pyrolysis. However, catalysts are easy to deactivate due to coke deposition. In this study, coke amount on activated carbon catalysts during catalytic upgrading of coal pyrolysis volatiles was investigated in the downer-bed reactor. The process of coke formation was studied at different feed time (30, 60 and 100 min) of coal. Results show that a great amount of coke is generated on the activated carbons. With the increase of feed time, the amount of coke on activated carbon increases, while the rate of coke formation decreases, thus decreasing the coke yield based on dry coal. The specific surface area and catalytic cracking activity of the activated carbon decrease with the increase of coke amount. Hence, the yields of tar and pitch increase with the increase of feed time. The relative content of oxygen-containing compounds in the tar increases with the increase of feed time, which indicates that the cleavage of weak chemical bond C–O is suppressed. That may result in a decrease in the rate of coke formation.

Coking behavior and syngas composition of the char supported Fe catalyst of biomass pyrolysis volatiles reforming

The biomass for flammable gas production and its carbon deposition behaviour has been studied in a lab-scale fixed bed reactor, comprising pyrolysis and subsequent volatiles reforming produced in situ reaction. The distribution of pyrolysis products varies greatly with the addition of WS@5 Fe catalyst. During catalyst cycle process, both the char and heavy oil yield decreases significantly from 27.34% and 6.73% to 20.41% and 4.12%, respectively. This work also focuses on the carbon deposition of the WS@5 Fe catalyst used in the second step. The amount of coke on quartz tube wall (coke 1) decrease with increasing the temperature, and the surface carbon of the catalyst (coke 2) is found. Deactivated catalyst samples are recovered. The results present that the deactivation is attributed to the wrapping and covering of Fe by coke. There are reactions such as the coke deposition, the coke consumption, and the gasification reaction of char.

Catalytic performance of hydrotalcite-like-compound-derived Ni-metal alloy catalyst for toluene reforming with gasoline engine exhaust model gas as reforming agent

Reforming of toluene with model exhaust gas was carried out as Reformed EGR of gasoline engine mainly at 773 K with Ni-M/Mg/Al (Ni 12 wt%, M = Fe, Co, Cu) prepared from corresponding hydrotalcite-like compounds. Ni-Fe/Mg/Al (Fe/Ni = 0.1–0.5) showed clearly higher performance than Ni/Mg/Al in terms of activity, coke-deposition resistance and stability. In contrast, Ni-M/Mg/Al (M/Ni = 0.25, M = Co, Cu) showed similar behaviors to Ni/Mg/Al. The optimum Fe/Ni ratio was 0.25 from toluene conversion and the suppression of benzene formation. Ni-Fe/Mg/Al (Fe/Ni = 0.25) showed high coke-deposition resistance at any position of the catalyst bed, indicating that both substrate decomposition and CO disproportionation were suppressed. The coke amount was not increased even at low temperature (773 K) or higher toluene partial pressure (toluene/H2O/N2/CO2 = 0.5–1.2/11.8/71.2/11.8, molar ratio), but the activity gradually decreased under such conditions. The Ni-Fe alloy nanoparticles in the reduced Ni-Fe/Mg/Al were almost unchanged during the reaction. The deactivated catalyst was regenerated successfully by the treatment under N2 at 873 K, catalytic use at 973 K or re-reduction. These results suggest that the deactivation was caused by carbonaceous species which can be removed easily even by N2 treatment, rather than by graphite-like coke that is difficult to be eliminated via such simple treatment.

Evaluation of Na-13X zeolites activity in the catalytic pyrolysis of rapeseed oil cake to produce bio-oil

Zeolite with cavities (Na-13XCAV) was obtained by treating of a commercially Na-13X zeolite with tetrapropyl ammonium hydroxide aqueous solution (TPAOH, 0.3 mol/L). In addition, to generate secondary mesopores in the zeolite network (Na-13XCAV-SM), the Na-13X zeolite was treated with a mixture solution of TPAOH/NaOH (ratio 1:1). The charaterization of the zeolites was performed by N2 sorption, X-ray diffraction spectroscopy and scanning electron microscopy. Na-13XCAV-SM showed a higher selectivity and was effective for increasing the hydrocarbon content in bio-oil, it was obtained a hydrocarbon yield of 6.8 wt %, which was over three times bigger than that resulted with Na-13 × . The properties of bio-oil produced were determined and a comparison of the properties depending on the catalyst used was made. In the presence of secondary mesopores,the diffusion of intermediates compounds became faster and their re-polymerization reactions were slowed down, thus, the resulting amount of coke was reduced and bio-oil fraction increased.

Catalytic upgrading of lignocellulosic biomass pyrolysis vapors: Insights into physicochemical changes in ZSM-5

Catalytic fast pyrolysis of biomass is an effective strategy for the preparation of high value-added liquid fuels or chemicals. Understanding the effects of different biomass materials on the physicochemical property changes of ZSM-5 is important for the design of modified catalysts and targeted regulation of products. In this study, the catalytic upgrading of lignocellulosic biomass over ZSM-5 was investigated. Lignin, cellulose and xylan were used as model compounds of lignocellulosic biomass, and the upgraded products were analyzed online. Several techniques were used to gain a deep understanding of the physiochemical changes in ZSM-5. The results showed that the addition of ZSM-5 contributed to the production of aromatic hydrocarbons and olefins. The crystal structure and morphology of ZSM-5 were not changed, but the total acid, Brønsted and Lewis acid contents decreased. The amount of coke deposited on ZSM-5 follows the order cellulose/ZSM-5 > xylan/ZSM-5 > lignin/ZSM-5. Coke on cellulose/ZSM-5 has the lowest H/C ratio of 0.50. Coke on ZSM-5 will create new micropores and increase the specific surface area of micropores.

Effect of coke deposition over microporous and hierarchical ZSM-23 zeolite

The effects of deactivation by coke deposition after the n-heptane cracking reaction were evaluated on crystallinity, acidity and activation energies for the coke thermal oxidation process in microporous and hierarchical ZSM-23 zeolites. The fresh and coked catalysts were characterized by X-ray diffraction, temperature-programmed desorption of ammonia and thermogravimetric analysis. The Flynn–Wall–Ozawa and Vyazovkin kinetic models were used to determine the activation energy of the catalyst regeneration process, using integral dynamic curves from thermogravimetric analysis data obtained with different heating rates. The generation of micro-/mesoporous structures provided a beneficial effect by inhibiting the loss of crystallinity and preserving a certain degree of acidity after catalyst deactivation. The hierarchical ZSM-23 zeolites showed lower deposited coke amounts and activation energy values for the coke thermal oxidation process, providing greater stability, activity and lower energy level required for regeneration in comparison with the microporous zeolites.

Study of thermal resistance of cold mixtures with clay addition

The article analyzes the results of heat resistance of cold-harmful mixtures with the addition of clay. The article presents the results of an experimental laboratory study of the properties of samples from CTS, obtained by various methods. The scientific novelty of the technology lies in the fact that the technology of casting in cold-rolled steel ensures high quality of the casting surface, the absence of gas defects and blockages in the casting. The selection of the composition and technological parameters for the manufacture of the mold, contributing to the production of high-quality defect-free castings, will significantly reduce their cost, which will have a positive effect on the economy of our country. The study of the change in density over time depending on the applied load was studied in a series of experiments. The density of the mixture was determined every thirty seconds during the entire time of the formation of the dispersed medium. These experiments showed that at the beginning of the formation of the shell, its density increases significantly. In works on the thermal stability of polymers, the general laws of thermal decomposition and carbonization of cyclic, spatially crosslinked hot curing polymers were investigated and it was shown that the kinetics of destruction, the composition of gaseous products, the amount of coke formed and its properties depend on the properties of the initial polymers - the degree of crosslinking of molecular chains, chemical structure, the presence of impurities of catalysts and other curing conditions, as well as the heating conditions - speed and temperature. The article summarizes some of the results of the study, which is most appropriate for thin-walled steel castings to use the following mixture composition: filler - quartz sand; binder - clay of the Kazakhstani deposit, epoxy resin, hardener.

Catalytic Deactivation of HY Zeolites in the Dehydration of Glycerol to Acrolein

The study of the deactivation of HY zeolites in the dehydration reaction of glycerol to acrolein has represented a challenge for the design of new catalysts. HY zeolites with SiO2/Al2O3 molar ratios between 3.5 and 80 were studied. The solids were characterized by XRD, N2 physisorption, SEM-EDXS, Raman and UV-vis spectroscopies, infrared spectroscopy of pyridine (FTIR-Py) and catalytic activity tests from 250 °C to 325 °C. It was found that the total amount of acid sites per unit area of catalyst decreased as the SiO2/Al2O3 molar ratio increased from 3.5 to 80, resulting in the decrease in the initial glycerol conversion. The initial acrolein selectivity was promoted with the increase of the Brønsted/Lewis acid sites ratio at any reaction temperature. The deactivation tests showed that the catalyst lifetime depended on the pore structure, improving with the presence of large surface areas as evidenced by the deactivation rate constants. The characterization of the deactivated catalysts by XRD, N2 physisorption and thermogravimetric analysis indicated that the deposition of coke resulted in the total obstruction of micropores and the partial blockage of mesopores. Moreover, the presence of large mesopores and surface areas allowed the amount of coke deposited at the catalyst surface to be reduced.

Catalytic cracking of chlorinated heavy wax from pyrolysis of plastic wastes to low carbon-range fuels: Catalyst effect on properties of liquid products and dechlorination

Catalytic conversion of useless chlorinated heavy wax (chlorine, 0.14 wt%) obtained from pyrolysis of refuse plastic fuel was studied using iron oxide impregnated HY zeolite to produce a useful liquid product. It was found that the largest liquid fraction (gasoline and kerosene/ diesel, 66.9 wt.%) with very low chlorine content was achieved when using Fe[3]/HY among impregnated HY catalysts. This demonstrated that the Fe impregnated HY catalyst had a dual function of catalytic cracking of HY zeolite and dechlorination of iron oxide. Excessive impregnation of Fe, i.e., Fe[20]/HY, showed the least cracking activity of heavy wax owing to the catalyst having lowest total acid sites, but yielded liquid product with the lowest chlorine content (60 ppm) among the tested catalysts. The spent catalysts were deposited by a significant amount of soft coke and chlorine, and they were totally restored by thermal treatment in air (700 ℃).

A comparative study on the chloride effectiveness of synthetic rutile and natural rutile manufactured from ilmenite ore

Studies on continuous and selective chlorination by using ilmenite have been actively conducted because the efficient removal of FeO from ilmenite(FeTiO3) ore using selective chlorination not only improves the reaction purity of TiCl4 but it also leads to price competitiveness compared to TiCl4 synthesized from natural rutile. The chlorination of synthetic rutile with FeO removed was compared with that of natural rutile to examine the reaction efficiency. The selective chlorination efficiency depends on the input amounts of coke and Cl2, as shown by thermodynamic calculation, when FeO is selectively removed. It was found that manufacturing of TiCl4 was easier by using the synthetic rutile, because it had greater porosity than natural rutile. Relatively greater pore volumes were found in the synthetic rutile than in natural rutile. It was confirmed that the reaction efficiency of chlorination for TiCl4 production was directly related to the difference in the porosity distribution between the titanium ores, as verified by a kinetic comparison of synthetic and natural rutiles.

Negative-carbon pyrolysis of biomass (NCPB) over CaO originated from carbide slag for on-line upgrading of pyrolysis gas and bio-oil

In this study, the feasibility and reaction mechanism of using CaO derived from calcined carbide slag in biomass pyrolysis to realize negative-carbon emission was investigated in a fixed bed reactor. The results showed that 0.06 g CO2/g biomass was fixed when the mass ratio of calcined carbide slag/biomass was 1:1. Further increasing the amount of calcined carbide slag increased a little on the yield of fixed-CO2, but the utilization efficiency of carbide slag reduced and large amounts of coke formed. As to the effect on pyrolysis products, calcined carbide slag increased the content of combustible component in pyrolysis gas (H2, CO and CH4) through CO2 absorption, catalytic decarbonylation and cracking effect, increasing the lower heating value (LHV) of pyrolysis gas. Meanwhile, calcined carbide slag favored the dehydration of sugars and furans to cyclopentanones, ketonization of acids to linear ketones, and cracking of heavy compounds to light phenols. As a result, the content of low-oxygen containing compounds in bio-oil increased at the cost of high-oxygen containing compounds. Overall, biomass pyrolysis with calcined carbide slag is a promising negative-carbon technology, which can realize negative-carbon emission and upgrade the quality of pyrolysis products at the same time.

Effects of Alkali Metals on Nickel/Alumina Catalyzed Ethanol Dry Reforming

Although ethanol dry reforming is an attractive carbon utilization technology, problems of severe coke formation and low catalytic activity should be solved for realization of the technology. We demonstrate the effects of alkali metal additives (lithium, sodium, and potassium) on nickel catalyzed ethanol dry reforming. Potassium doped nickel catalyst (Ni/K2O-Al2O3) showed enhanced catalytic activity and durability in ethanol dry reforming. Thermogravimetric analysis (TGA) showed that Ni/K2O-Al2O3 had a high resistance to coke formation. The amounts of coke formed on Ni/K2O-Al2O3 were 1/3 lower than the amounts of coke formed on Ni/Al2O3. The total coke quantities were closely correlated to the number of basic sites of the nickel catalysts. Raman spectroscopy and transmission electron microscopy analyses revealed that the alkali metals control the coke formation on the catalysts.