Char Catalyst Research Articles

Catalytic pyrolysis of biomass with char modified by cathode materials of spent lithium-ion batteries for tar reduction and syngas production

The char modified by the battery cathode material was studied for catalytic pyrolysis of rice husk (RH). Compared to the direct mixing, the addition of cathode material to char by the impregnation was more favorable to synthesize the lignin char catalyst (i.e. char 1) with hierarchical pore structure and larger specific surface area. The char 1 decreased the Ea of the RH pyrolysis from 79 kJ/mol to 66 kJ/mol. The char 1 decreased the yield of liquid product from 23.2% to 12.3% and increased the yield of gas product from 35.2% to 52.2%. The char 1 decreased the contents of acids from 20.6% to 3.6% and phenols (tar surrogates) from 29.4% to 8.0%. The increase of hydrocarbons and CO2 indicated that the char catalysts had high catalytic reactivity in converting the oxygenated components (e.g., sugars, furans, acids, phenols) into light hydrocarbons (e.g., alkanes, aromatics) and micro-molecular gases (e.g., CO2, H2).

Pyrolysis of RDF and Catalytic Decomposition of the Produced Tar in a Char Bed Secondary Reactor as an Efficient Source of Syngas

One of the technical limitations of refuse-derived fuel (RDF) pyrolysis is the high content of tar in its gas products. In order to resolve this problem, a two-stage RDF pyrolysis with a catalyst based on char from RDF pyrolysis is proposed. This paper presents the results of municipal waste pyrolysis beginning in an oven heated to 480 °C and ending with catalytic tar cracking carried out in the temperature range from 800 to 1000 °C. Thermal and catalytic pyrolysis with a char catalyst containing a minimum of 6% Fe resulted in increases in the CO and H2 contents in gas products and decreases in CO2 and CH4. At 1000 °C, the mass ratio of gaseous products to liquids was greater than 6. The residence time of the gases in the catalytic zone was about 3–5 s. The reactor was a good source of hydrogen and carbon monoxide.

Catalytic conversion of gaseous tar using coal char catalyst in the two-stage downer reactor

The effect of catalyst height (0–50 mm) and catalyst temperature (600–900 °C) on the catalytic cracking of gaseous tar is investigated using a two-stage down reactor. Results show that the utilization of catalyst promotes the removal of coal tar. The yield of coal tar at the pyrolysis temperature of 900 °C is 7.14% and tar is composed of aromatics and high-carbon-number aliphatics. The coal char prepared by fast coke-making method at 900 °C is directly used as a catalyst in the catalytic cracking of coal tar. When the catalyst temperature and the catalyst height are 900 °C and 50 mm, the tar produced by coal pyrolysis is connected with high-temperature coal char for a short time, reducing the tar yield from 7.14% to 4.26%. Among them, aliphatic hydrocarbons with carbon number of C10 and C11 and aromatics are the main components of coal tar. Similarly, compared with the pyrolysis, the content of CH4 and H2 obtained with the addition of the catalyst increase from 0.56 to 0.97 to 1.64%g/g coal and 1.02%g/g coal, respectively. Moreover, GC/MS results show that the increment of catalyst height and catalyst temperature increases aromatics content and facilitates the conversion of high-carbon-number component to low-carbon-number ones.

Catalytic toluene steam reforming using Ni supported catalyst from pyrolytic peat

The paper aims to investigate an effective method of catalytic reforming of toluene using peat char-supported Ni metal to achieve clean gas production. Utilizing KOH or CO2 activation to increases the surface area and pore volume of peat char during catalyst preparation. The chemical and structural properties of catalysts is explained based on SEM, EDS, XRD, BET method. Meanwhile, the influence of reaction temperature, residence times (τ), steam-to‑carbon ratios (S/C) in catalytic reaction and the molar ratio of CO, CO2, H2, CH4 in clean gas were investigated. The results indicated that SiO2 structure plays a significant role in nickel-based peat char catalyst, and the catalyst exhibited high catalytic performance. Conversion efficiencies of toluene can reach about 95.3% using Ni/APC catalyst at residence time of 0.5 s, steam-to‑carbon ratio of 3:1, temperature of 850 °C. The catalyst also exerted a positive effect on the syngas (CO + H2) production with the maximum molar ratio reaching up to 94.7 mol% under the optimized conditions. The high catalytic activity was mainly attributed to the structure of AlNi2Si and NiSi on the catalyst surface. Therefore, the cost-effective peat char-supported Ni catalysts could be used for aromatic tar conversion.

Production of bio-based chemicals from palmitic acid by catalytic hydrotreating over low-cost Ni/LY char and limonite catalysts

Catalytic hydrotreating of fatty acid is respected to produce bio-based chemicals especially oleochemicals that can be applied as a high valuable raw material or intermediate materials for industries. Low-cost Ni/LY char and limonite catalysts can compensate the expensively commercial catalysts. Palmitic acid (PA) was represented as reactant. Chemical compositions of liquid product were analyzed and presented in compound group, carbon number distribution and product selectivity. Catalyst characteristics and liquid product properties were also investigated. BET surface area, pore volume, and pore size of the prepared Ni/LY char catalyst were 308 m2/g, 0.188 cm3/g and 2.43 nm, respectively, and those of limonite catalyst were 95 m2/g, 0.3 cm3/g and 12.59 nm, respectively. Based on the initial 3 MPa H2 at 300 °C, the obtained oleochemicals depended on catalyst type, reaction time and solvent. In case of Ni/LY char catalyst, ester was found in yield of 58.94% that mainly contained with isopropyl palmitate up to 82% of ester, meanwhile product from limonite was principally distributed in alcohol group with 51.84% in which n-pentadecanol was the major compound with 37.05% yield. The products showed the oxygen removal in range of 19.11–65.15 mol% and HHVs were increased to 32.11–34.13 MJ/kg when compared with PA.

Waste furniture gasification using rice husk based char catalysts for enhanced hydrogen generation

Present study provides biohydrogen production methods from waste furniture via catalytic steam gasification with bio-char catalysts (raw char, KOH-activated char and steam-activated char). Total gas yield for the prepared chars was in the order of KOH-activated char > steam-activated char > raw char, whereas, H2 selectivity was in the sequence of raw char > steam-activated char > KOH-activated char. Though KOH-activated char showed the highest gas yield, highest H2 selectivity was obtained at the gasification experiment with raw char due to the large amount of Ca and K and its reasonable surface area (146.89 m2/g). Although the activation of raw biochar results in the increase of gas yield, it has the negative effect on H2 generation due to the removal of alkali and alkaline earth metals for the KOH activated char and steam-activated char. This study shows that raw bio-char could be a potential solution for eco-friendly hydrogen production.

Activated char supported Fe-Ni catalyst for syngas production from catalytic gasification of pine wood

Char-based catalyst has a promising application for biomass thermal conversion technology. In this work, Fe-Ni/Activated Char (AC) catalyst was prepared by impregnation method and used for the catalytic gasification of pine wood to obtain syngas. Further, the catalytic performance of Fe-Ni/AC was established by doing a comparative study of catalytic gasification of different biomass feedstocks. The results showed that under the catalysis of Fe-Ni/AC, the increase of gasification temperature was beneficial to increase gas yield, but not conducive to regulate the H2/CO ratio of syngas. The steam flow rate was directly related to the catalytic effect of Fe-Ni. The H2/CO ratio of syngas could reach 1.97 under the optimal conditions. Fe-Ni/AC had different catalytic effects on different biomass feedstocks, with the best for pine wood and the worst for cotton stalk, indicating that gasification intermediates of pine wood were difficult to decompose and depended more on catalyst.

Catalytic conversion characteristics of tar at different temperatures during circulating fluidized bed gasification

Char catalytic conversion of tar at different temperatures was carried out on a laboratory-scale circulating fluidized bed to providing theoretical support for the removal of tar. Various modern detection techniques were used to analyze the gas, tar and char, such as the gas chromatograph, the specific surface area analyzer and the gas chromatograph mass spectroscopy (GC-MS). The efficiency of tar conversion (ETC) could be effectively improved by the increasing temperature, while transformation characteristics of the organic compounds of the used tar also changed. When the temperature increased from 850 °C to 900 °C, the catalytic capability of char was improved, resulting a reducing of the heavy polycyclic aromatic hydrocarbon compounds (heavy PAH compounds) of the produced tar. When the temperature increased from 900 °C to 950 °C, the catalytic capability of char weakened, so the heavy PAH compounds increased, caused by the intensifying of tar thermal cracking. At the tested temperature (850–950 °C), the conversion of naphthalene, the most abundant organic compound in the used tar, has not been seem a significant change, showing a selectivity of the char catalyst.

Understanding the catalytic upgrading of bio-oil from pine pyrolysis over CO2-activated biochar

To understand the catalytic upgrading of bio-oil over char-based catalyst, pyrolysis of pine sawdust with various char catalysts under different reaction temperatures was performed in a fixed-bed reactor, from which the liquid product was analyzed with gas chromatography-mass spectrometry (GC/MS). The main pyrolytic liquids were ketones and acids in the non-catalytic pyrolysis run, which were mainly derived from the pyrolysis of cellulose and hemicellulose in biomass by ring opening and side chain cracking reactions, while the relative content of phenolic substances obtained from catalytic reaction at 400 °C over CO2-activated char increased from 33.79% to 78.12% with the increasing char activation time from 0.5 to 2.0 h, resulting from the formation of more multiple active sites (including surface active groups and the pore characteristics) on activated char. When the catalytic reaction temperature reached 600 °C, the quality of the bio-oil was further improved since the relative content of aromatic hydrocarbons increased from 7.30% to 21.04% at the expense of elimination of some oxygen-containing compounds (e.g., ketones, acids, aldehydes, etc). Furthermore, the content of phenol in phenolic compounds increased from 26–64% to 51–97%.

Nitrogen-doped char as a catalyst for wet oxidation of phenol-contaminated water

Catalytic wet oxidation (CWO) of aqueous effluents rich in organic compounds is a very promising technology for the treatment of liquid wastes from biomass conversion processes. CWO reactions occur through the formation of free radical species, produced in the presence of an oxidant, which act on organic contaminates in the effluent. Although the reaction is well known, there exists a lack of affordable catalysts to conduct this process at the lower temperatures and pressures in novel bioenergy processes. This study assessed the catalytic effect of nitrogen-doped chars as such an option. Phenol in aqueous solution was used as a model waste effluent. Treatment was conducted at moderate temperatures (190 to 260 °C), oxygen partial pressure of 1 MPa, and reaction times of 15, 30, and 45 min in stainless steel and glass-lined tube reactors. High pressure liquid chromatography (HPLC) analyses of the products quantified phenol and by-product concentrations used in the calculation of reaction activation energy. The char catalyst was studied by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) in order to gain insight into its structure and surface composition. The results indicate that nitrogen-doped char catalysts accelerate the oxidation of phenol by decreasing its reaction activation energy from 82.2 kJ/mol (non-catalyzed) to 40.4 kJ/mol (catalyzed). An analysis from first principles using density functional theory (DFT) was conducted to ascertain which N functional group has the most significant impact on free radical formation in the presence of oxygen. Among all the N functional groups studied, the dipyridinic functional groups showed the most promising characteristics to facilitate the formation of hydroxyl free radicals.

Pyrolysis of Rice Husk with Char Catalyst from Lignin and Spent Lithium-Ion Battery Cathode

Pyrolysis of Rice Husk with Char Catalyst from Lignin and Spent Lithium-Ion Battery Cathode

Influence of coal treatments on the Ni loading mechanism of Ni-loaded lignite char catalysts

Many kinds of lignite coals have been used as catalyst supporters for preparing the Ni-loaded lignite char catalyst. However, these coals have different properties; especially ash content. The ash in coal affects the mechanism of Ni-loading on the position of the functional group structures in coal. In catalyst preparation, it is interesting that the difference in coal properties might directly influence the mechanism of Ni loading. To prove this point, the coal sample needed to be treated before the catalyst preparation. MM coal (original coal) was treated with acid (HClMM and AceMM coals), alkali (NaMM coal) and alkali followed by acid treatments (NaHClMM and NaAceMM coals). Then, Ni was loaded on the five treated coals by the ion-exchange technique. The Ni-loaded lignite coals were pyrolyzed at 650 °C under a N2 atmosphere to prepare the Ni-loaded lignite char catalysts. The Ni-loading mechanisms were studied via FTIR, XRD, AAS and SEM-EDS analyses. The results showed that the different treatments affected the ash content and the functional groups in the coals. The decreases in the ash contents of HClMM, AceMM, NaHClMM and NaAceMM coals indicated that the exchangeable metallic species were removed by transforming metal-carboxylates into carboxyl groups. The transformations of metal-carboxylates were confirmed by the increased Δϑ(COO−) value. For acid treatment, the ion exchange of Ni was controlled by carboxyl groups, while in alkali treatment it occurred through hydroxyl and metal-carboxyl groups. In alkali followed by acid treatment, Ni ions were exchanged with hydroxyl and carboxyl groups. The Ni ion forms, Ni(NH3)62+ and/or Ni(H2O)62+, appeared on the modified coals. Through pyrolysis, the Ni ion was reduced to Ni metal that was observed in the XRD patterns of the catalysts. The Ni contents of the catalysts were in the range of 16.51–20.07 wt%. The thermal behaviours of the catalysts were presented via TGA-DTG.

Athmospheric Hydrocracking of Jatropha Oil Using Woodchar Catalyst

Jatropha oil which is non-edible oil were hydro-crack at atmospheric pressure using an activated wood char catalyst in a fixed bed reactor. The hydro-cracking process was carried out at three temperature variations of 400, 450 and 500oC, and three variations of the oil feed injection rate of 2/2, 2/5 and 2 mL/10 minutes. The catalysts were characterized using SEM and BET. The composition of the liquid product obtained from the hydro-cracking process was analyzed using GC-MS. The effects of operating temperature and oil feed injection rate on oil recovery and conversion have been discussed. The results showed that the feed injection temperature and rate had an effect on the yield and conversion. The highest yield of 59.8% oil liquid products was achieved at a temperature of 450oC with injection rate of 2 mL/10 min. The composition of the oil-liquid product was dominated by heptanal at 32.9% -mass. Alkanes group contain C5 to C20 and alkene compounds consist of C8 until C18.

Catalytic conversion of toluene over a biochar bed under an inert atmosphere – The comparison of chars from different types of wood and the role of selected metals

In this paper, toluene, a tar-representing compound, was used in pyrolytic conversion tests with a wood-derived char catalyst. The decomposition mainly occurred via two competing heterogeneous reactions; the favoured reaction led to coke formation on the catalyst bed. With char saturation of the carbon deposit, a second demethylation reaction gained significance, until selectivity towards benzene formation reached 12–16%. By-products of the secondary reaction (xylenes, ethylbenzene and styrene) were also detected; however, no gas-phase toluene decomposition occurred. The principles of toluene conversion were the same for all of the examined chars from the different tree species. However, a quantitative difference was observed between the chars from the wood from coniferous and deciduous trees. Pine yielded char with less mesopores and active sites and thus demonstrated a lower efficiency as a catalyst for toluene decomposition. An assessment of alkali and alkaline earth metals importance revealed that, while their presence in the char strongly enhances its oxidation rate, they did not affect the toluene pyrolysis.

Hydrodeoxygenation of guaiacol via rice husk char supported Ni based catalysts: The influence of char supports

Six different treatments were carried out on the pyrolyzed and raw rice husks, including hydrothermal carbonization (HI), pyrolysis-acidification (PAI), pyrolysis-steam activation (PSI), pyrolysis (PI), pyrolysis-impregnation-steam activation (PIS) and acidification-pyrolysis (API). The modified chars were used as the supports for Ni-based catalysts, and activated carbon (AC) was used as the comparison. In situ vapour-phase hydrodeoxygenation (HDO) of guaiacol was performed at atmospheric and low temperature. The effect of different char catalysts on the HDO activity of guaiacol was investigated. The physical and chemical properties of the catalysts were characterised by BET, XRD, SEM, H2-TPR, NH3-TPD, etc. The mass transfer process of char heterogeneous catalyst was analysed. The results showed that the catalyst 20Ni/RH-HI obtained a medium-strong acidity and a smallest grain size, and achieved the highest HDO ratio of 55.28% and BTX selectivity of 7.56%. BTX (benzene, toluene and xylene), phenols and cyclohexanones were the main products, indicating that most of hydrogenolysis occurred on the Caromatic-OH and O–CH3 skeleton. And small part of hydrogenolysis was on the phenyl-ring. The HDO activity was determined by the pore structure, acidity and active metal grain size of the char catalysts.

Selective production of aromatics from waste plastic pyrolysis by using sewage sludge derived char catalyst

Sewage sludge char was used as the catalyst to realize the selective production of aromatics in the pyrolysis of waste mixed plastics. The effect of catalytic temperature, residence time, and plastic compositions on the product yield and distribution were investigated. The catalytic behavior of main ash components was evaluated and discussed. It was found that the selectivity of sludge char to monocyclic aromatics was up to 75.3% when catalytic temperature was 600 °C with a residence time of 1 s. The content of styrene and xylene reached 29.1% and 12.5% in oil, respectively. The selectivity of sludge char to bicyclic aromatics was up to 64.4% when the temperature was 800 °C with the same residence time of 1 s. Naphthalenes accounted for 47.5% of the pyrolysis oil. The interaction among polyethylene, polypropylene, and polystyrene improved the selectivity of bicyclic aromatics from 46.8% to 53.7%. It can be concluded that principal ash components in sludge char could increase the aromatization degree of chain hydrocarbons and reduce the condensation degree of already formed aromatics. Acid sites (mainly aluminum phosphate) and dehydrogenation active sites (mainly -PO, sulfides, etc.) could promote the formation of aromatics by catalyzing direct dehydrogenation, hydrogen transfer reaction, and Diels-Alder reaction; while ring-opening active sites (mainly calcium oxide and iron species) could prevent the formation of excessively heavy aromatics by hydrogenation and ring-opening process.

Reactivity and deactivation mechanisms of toluene reforming over waste peat char-supported Fe/Ni/Ca catalyst

The pyrolysis char from waste peat with impregnated metal (Fe/Ni/Ca) were investigated for catalytic reforming of toluene in a laboratory dual-stage reactor. The prepared catalysts were examined in microstructure and textural characterization to analyze catalytic performance and stability. The results indicated that under the optimized conditions, the toluene conversions are greater than 92.7% for three types of peat char-supported catalysts, and the maximum molar ratio of syngas (CO + H2) can reach up to 94.7% using Ni/peat char catalyst. The promising results demonstrated that the H2 and CO are favored for Fe/peat char and Ni/peat char catalysts while the H2 and CH4 are favored for Ca/peat char catalyst. After 320 min of experiment, the mol% of syngas decreased by less than 30% for three types of peat char catalysts. Significantly, peat char (C-SiO2) as a carrier can enhance the performance of catalyst through interaction with the metal, and it can be used as an adsorption carrier to absorb unreacted toluene. Such peat char-supported catalysts are thus promising for tar conversion and useful syngas production.

Syngas production by catalytic pyrolysis of rice straw over modified Ni-based catalyst

Ni-xLa/Al2O3-MgO-sawdust char catalysts were prepared by modifying the Ni/Al2O3 catalyst from two aspects of support and active components. The effect of Al2O3, MgO, sawdust char molar ratio, and La content of catalysts on syngas (H2 + CO) production in the catalytic pyrolysis of rice straw was investigated in a horizontal fixed-bed quartz tube reactor. Furthermore, the stability of catalysts with the optimum catalytic performance was tested and compared with that of the Ni/Al2O3 catalysts. X-ray diffraction, X-ray fluorescence, field emission scanning electron microscopy, energy disperse X-ray, and Brunauer-Emmett-Teller analyses were applied to understand the physiochemical properties of the supports and catalysts. The study revealed that the supports were composed of many irregular flaky particles and thus formed many pores. Moreover, the addition of La decreased the particle size of NiAl2O4 and increased the active metal surface of the Ni/Al2O3-MgO-sawdust catalysts. When the molar ratio of Al2O3, MgO, and sawdust char was 1:1:1 and the La content was 10 wt% (dry weight basis), the catalysts presented the highest syngas concentration of 78.9 vol% and the most stable performance during the catalytic pyrolysis process.

Catalytic conversion of gaseous tars using land, coastal and marine biomass-derived char catalysts in a bench-scale downstream combined fixed bed system

The catalytic activity of biochar for tar removal was evaluated in a bench-scale combined fixed bed reactor by comparison of gaseous tar catalytic cracking behaviors over land (Corn stalks, Cs), coastal (Reed, Re) and marine (Sargassum horneri, Sh) char catalyst. The experiments demonstrated that the tar yield after addition of the biochar was reduced significantly; the tar conversion efficiency reached to 94.6% for catalytic at 850 °C with 50 mm char bed length using Re char. And the yield and composition of gas also changed markedly. The percentage of H2 and CO in the product gas were obviously increased. Sh has a higher H2 content (49.3% of the total gas content), whereas, CO dominated in the gas products for Cs (45.4%) and Re (48.1%). The results from GC–MS analysis illustrated that the increase in temperature promoted the tar cracking and also promotes the polymerization of some tar components.

Mini-Review on Char Catalysts for Tar Reforming during Biomass Gasification: The Importance of Char Structure

With the depletion of fossil fuel reserves and the increasing concern about greenhouse gas emission, the need to develop technologies for using renewable and sustainable energy resources is becomin...