Kinetic study of the catalytic reforming of biomass pyrolysis volatiles over a commercial Ni/Al2O3 catalyst

An original kinetic model has been proposed for the reforming of the volatiles derived from biomass fast pyrolysis over a commercial Ni/Al₂O₃ catalyst. The pyrolysis-reforming strategy consists of two in-line steps. The pyrolysis step is performed in a conical spouted bed reactor (CSBR) at 500 °C, and the catalytic steam reforming of the volatiles has been carried out in-line in a fluidized bed reactor. The reforming conditions are as follows: 600, 650 and 700 °C; catalyst mass, 0, 1.6, 3.1, 6.3, 9.4 and 12.5 g; steam/biomass ratio, 4, and; time on stream, up to 120 min. The integration of the kinetic equations has been carried out using a code developed in Matlab. The reaction scheme takes into account the individual steps of steam reforming of bio-oil oxygenated compounds, CH₄ and C₂-C₄ hydrocarbons, and the WGS reaction. Moreover, a kinetic equation for deactivation has been derived, in which the bio-oil oxygenated compounds have been considered as the main coke precursors. The kinetic model allows quantifying the effect reforming conditions (temperature, catalyst mass and time on stream) have on product distribution.     

Pyrolysis of giant mullein (Verbascum thapsus L.) in a fixed-bed reactor: Effects of pyrolysis parameters on product yields and character

Slow pyrolysis of giant mullein (Verbascum thapsus L.) stalks have been carried out in a fixed-bed tubular reactor with (Al₂O₃, ZnO) and without catalyst at four different temperatures between 400 to 550°C with a constant heating rate of 50°C/min and with a constant sweeping gas (N₂) flow rate of 100 cm³/min. The amounts of bio-char, bio-oil, and gas produced were calculated and the compositions of the obtained bio-oils were determined by gas chromatography-mass spectrometry. The effects of pyrolysis parameters, such as temperature and catalyst, on the product yields were investigated. The results show that both temperature and catalyst have significant effects on the conversion of Verbascum thapsus L. into solid, liquid, and gaseous products. The highest liquid yield of 40.43% by weight including the aqeous phase was obtained with 10% zinc oxide catalyst at 500°C temperature. Sixty-seven different products were identified by gas chromatography-mass spectrometry in the bio-oils obtained at 500°C temperature.     

Highly selective CuO/γ–Al2O3 catalyst promoted with hematite for efficient methanol dehydration to dimethyl ether

A recent alternative for replacing traditional hydrocarbons like gasoline, diesel, and natural gas, is the use of dimethyl ether (DME), which is more environmentally friendly. One of the ongoing challenges is to catalyze methanol dehydration for selectively producing the DME (2CH₃OH → CH₃OCH₃ + H₂O). It is established that the CuO catalyst over alumina performs the methanol dehydration, but the formation of by-products is the main drawback. For these reasons, we synthesized a CuO/γ–Al₂O₃ catalyst promoted with hematite aiming to enhance the activity toward DME at atmospheric conditions. The resulting bimetallic catalyst (CuO-Fe₂O₃/Al₂O₃) performed a 70% conversion at 290 °C, which is similar to other catalysts recently reported in the literature but done in harsh conditions. In addition, this bimetallic catalyst exhibited a 100% in selectivity toward the DME production. XPS spectra of the fresh and used catalyst suggested that the chemical oxidation states of Cu and Fe remain without change. After regenerating the catalyst at 600 °C for 2 h in air, it performed at a similar catalytic conversion, confirming the reusability of the as-synthesized material and reducing the environmental impact.     

Pyrolysis of Alternanthera philoxeroides (alligator weed): Effect of pyrolysis parameter on product yield and characterization of liquid product and bio char

In the present work, fast pyrolysis of Alternanthera philoxeroides was evaluated with a focus to study the chemical and physical characteristics of bio-oil produced and to determine its practicability as a transportation fuel. Pyrolysis of A.philoxeroides was conducted inside a semi batch quartz glass reactor to determine the effect of different operating conditions on the pyrolysis product yield. The thermal pyrolysis of A. philoxeroides were performed at a temperature range from 350 to 550 °C at a constant heating rate of 25 °C/min & under nitrogen atmosphere at a flow rate of 0.1 L/min, which yielded a total 40.10 wt.% of bio-oil at 450 °C. Later, some more sets of experiments were also performed to see the effect on pyrolysis product yield with change in operating conditions like varying heating rates (50 °C/min, 75 °C/min & 100 °C/min) and different flow rates of nitrogen (0.2, 0.3, 0.4 & 0.5 L/min). The yield of bio-oil during different heating rate (25, 50, 75 and 100 °C/min) was found to be more (43.15 wt.%) at a constant heating rate of 50 °C/min with 0.2 L/min N₂ gas flow rate and at a fixed pyrolysis temperature of 450 °C. The High Heating Value (HHV) value of bio-oil (8.88 MJ/kg) was very less due to presence of oxygen in the biomass. However, the high heating value of bio-char (20.41 MJ/kg) was more, and has the potential to be used as a solid fuel. The thermal degradation of A. philoxeroides was studied in TGA under inert atmosphere. The characterization of bio-oil was done by elemental analyser (CHNS/O analyser), FT-IR, & GC/MS. The char was characterized by elemental analyser (CHNS/O analysis), SEM, BET and FT-IR techniques. The chemical characterization showed that the bio-oil could be used as a transportation fuel if upgraded or blended with other fuels. The bio-oil can also be used as feedstock for different chemicals. The bio-char obtained from A. philoxeroides can be used for adsorption purposes because of its high surface area.     

Hydrogen production from the methanolysis of ammonia borane by Pd-Co/Al2O3 coated monolithic catalyst

The aim of this study is to enable high hydrogen production yield from catalytic methanolysis of ammonia borane (AB) in the presence of a cordierite type ceramic monolithic. The monolithic channel surfaces were coated with Al₂O₃ by wash-coating method and then this layer was impregnated with 1 wt%Pd-2 wt%Co bimetallic catalyst. SEM-EDX and multi-point BET analysis were used in order to characterize the catalyst. The experimental studies were conducted in a continuous flow type reactor, which was used for the first time in this study. The reactions were carried on low temperature (40 °C), and with various AB feed concentrations and flow rates. It was found that the highest hydrogen production yield (88.5%) was obtained from AB flow rate of 3.3 mL/min, and AB feed concentration of 0.1 wt%. It was concluded that Pd-Co/Al₂O₃ coated monolithic, which is a stable, active and low-cost catalyst, was a very promising catalyst for on-board hydrogen production from the methanolysis of ammonia borane.     

Pyrolysis of Xanthium strumarium in a fixed bed reactor: Effects of boron catalysts and pyrolysis parameters on product yields and character

Pyrolysis of Xanthium strumarium has been performed in a fixed-bed tubular reactor with boron minerals (ulexite, colemanite, and borax) and without catalyst at three different temperatures ranging from 350°C to 550°C with heating rate of 50°C/min. The amounts of bio-oil, bio-char, and gas generated, also the compositions of the resulting bio-oils were identified by GC-MS and FT-IR. The influences of pyrolysis parameters, such as temperature and catalyst on product yields were investigated. Temperature and catalyst were found to be the main factors affecting the conversion of Xanthium strumarium into solid, liquid, and gaseous products. The highest liquid yield (27.97%) including water was obtained with 10% colemanite (Ca₂B₆O₁₁.5H₂O) catalyst at 550°C temperature at a heating rate of 50°C/min when 0.224 > D_p > 0.150 mm particle size raw material and 100 cm³/min of sweeping gas flow rate were used.     

Characterization of the physicochemical and structural evolution of biomass particles during combined pyrolysis and CO2 gasification

The combination of pyrolysis and CO₂ gasification was studied to synergistically improve the syngas yield and biochar quality. The subsequent 60-min CO₂ gasification at 800 °C after pyrolysis increased the syngas yield from 23.4% to 40.7% while decreasing the yields of biochar and bio-oil from 27.3% to 17.1% and from 49.3% to 42.2%, respectively. The BET area of the biochar obtained by the subsequent 60-min CO₂ gasification at 800 °C was 384.5 m²/g, compared to 6.8 m²/g for the biochar obtained by the 60-min pyrolysis at 800 °C, and 1.4 m²/g for the raw biomass. The biochar obtained above 500 °C was virtually amorphous.     

Utilization possibilities of Albizia amara as a source of biomass energy for bio-oil in pyrolysis process

Pyrolysis is one of the potential routes to harmless energy and useful chemicals from biomass. The pyrolysis of Albizia amara was studied for determining the main characteristics and quantities of liquid products. Particular investigated process variables were temperature from 350 to 550°C, particle size from 0.6 to 1.25 mm, and heating rate from 10 to 30 °C/min. The maximum bio-oil yield of 48.5 wt% at the pyrolysis temperature of 450°C was obtained at the particle size of 1.0 mm and at the heating rate of 30 °C/min. The bio-oil product was analyzed for physical, elemental, and chemical composition using Fourier transform infrared spectroscopy and gas chromatography spectroscopy. The bio-oil contains mostly phenols, alkanes, alkenes, saturated fatty acids and their derivatives. According to the experimental results, the pyrolysis bio-oil can be used as low-grade fuel having heating value of 18.63 MJ/kg and feedstock for chemical industries.     

Performance of active nickel loaded lignite char catalyst on conversion of coffee residue into rich-synthesis gas by gasification

Performance of nickel-loaded lignite char catalyst on conversion of coffee residue into synthesis gas by catalytic steam gasification was carried out at low reaction temperatures ranging from 500 °C to 650 °C in the two-stage quartz fixed bed reactor. The effects of steam pressures (30, 36 and 50 kPa corresponding to S/B = 2.23, 2.92 5.16, respectively) and catalyst to biomass ratios (C/B ratio = 0, 1, 3) were considered. Nickel-loaded lignite char was prepared as a catalyst with a low nickel loading amount of 12.9 wt%. The gas yields in the catalytic steam gasification process strongly depended on the reaction temperature and C/B ratio. The total gas yields obtained in catalytic steam gasification was higher than that of catalytic pyrolysis, steam gasification and non-catalytic pyrolysis with steam absence by factors of 3.0, 3.8 and 7.7, respectively. To produce the high synthesis gas, it could be taken at 600 °C with total gas yields of 67.13 and 127.18 mmol/g biomass-d.a.f. for C/B ratios of 1.0 and 3.0, respectively. However, the maximum H₂/CO ratio was 3.57 at a reaction temperature of 600 °C, S/B of 2.23 and C/B of 1.0. Considering the conversion of coffee residue by catalytic steam gasification using the nickel-loaded lignite char catalyst, it is possible to covert the coffee residue volatiles into rich synthesis gas.     

A comparative study on the quality of bioproducts derived from catalytic pyrolysis of green microalgae Spirulina (Arthrospira) plantensis over transition metals supported on HMS-ZSM5 composite

This study investigated three different types of catalysts: Ni/HMS-ZSM5, Fe/HMS-ZSM5, and Ce/HMS-ZSM5 in the thermochemical decomposition of green microalgae Spirulina (Arthrospira) plantensis. First, non-catalytic pyrolysis tests were conducted in a temperature ranges of 400–700 °C in a dual-bed pyrolysis reactor. The optimum temperature for maximized liquid yield was determined as 500 °C. Then, the influence of acid washing on bio-products upgrading was studied at the optimum temperature. Compared to the product yields from the pyrolysis of raw spirulina, a higher bio-oil yield (from 34.488 to 37.778 %wt.) and a lower bio-char yield (from 37 to 35 %wt.) were observed for pretreated spirulina, indicating that pretreatment promoted the formation of bio-oil, while it inhibited the formation of biochar from biomass pyrolysis. Finally, catalytic pyrolysis experiments of pretreated-spirulina resulted that Fe as an active phase in catalyst exhibited excellent catalytic activity, toward producing hydrocarbons and the highest hydrogen yield (3.81 mmol/gr spirulina).     

Carbon dioxide methanation over Ni-M/Al2O3 (M: Fe,CO, Zr,La and Cu) catalysts synthesized using the one-pot sol-gel synthesis method

In this paper, a series of mesoporous supported nickel based catalysts on nanocrystalline alumina carrier promoted with various metals (Fe, CO, Zr, La and Cu) were prepared and employed in carbon dioxide methanation reaction. The samples were characterized by XRD, BET, TPR and SEM techniques. The BET results showed that the incorporation of promoters into nickel based catalysts decreased the surface area. The results showed that among the prepared catalysts, 30 wt.%Ni-5 wt.%La/Al₂O₃ and 30 wt.%Ni-5 wt.%Fe/Al₂O₃ possessed the highest surface area and the largest pore volume, respectively. Likewise, there was a slight decrease in the pore volume and the average pore diameters of the promoted samples. The TPR results depicted that the incorporation of the promoters enhanced the reducibility of the catalysts and shifted the reduction of NiO species to a lower reduction temperature. The CO₂ conversions of all promoted catalysts except Cu-promoted sample were higher peculiarly at low temperatures compared to those attained for the unpromoted catalyst. 30 wt.%Ni-5 wt.%Fe/Al₂O₃ catalyst exhibited the best catalytic performance (70.63% CO₂ conversion and 98.87% CH₄ selectivity at 350 °C), high stability and desirable resistance against sintering.     

Evaluation of influence of two different catalysts on the pyrolysis of laurel (Laurus nobilis L.) extraction residues

Laurel extraction residues with zeolite and alumina catalysts were pyrolyzed in a fixed-bed reactor with a constant heating rate of 10°C min^–1. The final pyrolysis temperature and sweep gas flow rate were kept constant at 500°C and 100 ml min^–1 in all of the experiments, respectively. The influence of catalysts and their ratio (10, 20, 30, 40, and 50% w/w) on the pyrolysis conversion and product yields were investigated in detail. The physicochemical properties of the catalytic bio-oil were determined and compared to those of non-catalytic bio-oil. The catalytic bio-oils were examined using some spectroscopic and chromatographic techniques.     

Synthesis of nanocrystalline mesoporous Ni/Al2O3SiO2 catalysts for CO2 methanation reaction

A series of nanocrystalline mesoporous Ni/Al₂O₃SiO₂ catalysts with various SiO₂/Al₂O₃ molar ratios were prepared by the sol-gel method for the carbon dioxide methanation reaction. The synthesized catalysts were evaluated in terms of catalytic performance and stability. The catalysts were studied using XRD, BET, TPR and SEM. The BET results indicated that the specific surface area of the samples with composite oxide support changed from 254 to 163.3 m²/g, and an increase in the nickel crystallite size from 3.53 to 5.14 nm with an increment of Si/Al molar ratio was visible. The TPR results showed a shift towards lower temperatures, indicating a better reducibility and easier reduction of the nickel oxide phase into the nickel metallic phase. Furthermore, the catalyst with SiO₂/Al₂O₃ molar ratio of 0.5 was selected as the optimal catalyst, which showed 82.38% CO₂ conversion and 98.19% CH₄ selectivity at 350 °C, high stability, and resistivity toward sintering. Eventually, the optimal operation conditions were specified by investigating the effect of H₂/CO₂ molar ratio and gas hourly space velocity (GHSV) on the catalytic behavior of the denoted catalyst.     

Conversion of hydrogen/carbon dioxide into formic acid and methanol over Cu/CuCr2O4 catalyst

Cu/CuCr₂O₄ catalysts were prepared by impregnation method at various calcination temperatures (300, 400, and 500 °C) and then reduced in H₂ stream. The aggregated particles and decreasing surface area/pore volumes of the deactivated catalysts during HCOOH and CH₃OH formations were also observed. Particularly, the EXAFS data showed that first shells of Cu atoms transforms from Cu–O to Cu–Cu after catalytic reactions, their bond distances and coordination numbers are quite different, respectively. It revealed that metallic Cu atoms are one of the important active species over catalyst surface at different reaction temperatures having many unoccupied binding sites for HCOOH and CH₃OH formations. Additionally, the optimal calcination temperature for Cu/CuCr₂O₄ catalysts was demonstrated at 400 °C that attributed to its strongest acidity and basicity. The catalytic reactions in the duration of HCOOH and CH₃OH preparation were proposed that were composed of HCOOH formation, CH₃OH formation, and CH₃OH decomposition happening at CuCr₂O₄, Cu, and CuO active sites, respectively. The highest CO₂ conversion (14.6%), HCOOH selectivity/yield (87.8/12.8%), and TON/TOF values (4.19/0.84) were obtained at 140 °C and 30 bar in 5 h, respectively. Optimal rate constant (2.57 × 10^?2 min^?1) and activation energy (16.24 kJ mol^?1) of HCOOH formation were evaluated by pseudo first-order model and Arrhenius equation, respectively.     

Effect of metal oxide/alumina on catalytic deoxygentation of biofuel from physic nut residues pyrolysis

Rapid catalytic thermal conversion of Physic nut (Jatropha curcas) residues for upgrading the released vapors was performed using analytical pyrolyzer-gas chromatography/mass spectrometry at 873 K. Conditioning of the evolved vapor product is required since the main vapor products formed without catalysts typically contained around 60% fatty acids, while the total hydrocarbon yields were only 12%. Catalysts tested were alumina (Al₂O₃) alone and modified by 5 wt% impregnation with various transition metal salts and then calcined to metal oxides. A significant decrease in the proportion of oxygenated compounds (including acids) from 73% without a catalyst to less than 10% with, and an increased conversion to hydrocarbons of more than 70% was obtained with the metal/Al₂O₃ catalysts at a Jatropha:catalyst (J:C) ratio of 1:10. The product selectivity was greatly increased as the J:C ratio was increased from 1:1 to 1:10. The total hydrocarbon selectivity of the metal/Al₂O₃ catalysts was increased in the order of Pd > Ni > Ce > Ru > La > none > Co > Mo, with the highest proportion of total hydrocarbons obtained being 75%. In addition, only a low yield (<2%) of polycyclic aromatic hydrocarbons was obtained from the conversion of Jatropha curcas residues. However, these catalysts adversely promoted N-containing compounds, suggesting that a further denitrogenation process is necessary. Nevertheless, the overall performance of these transition metal/Al₂O₃ catalysts is acceptable and they can be considered as good candidates for bio-oil upgrading.     

Salicylaldimine-Ni complex supported on Al2O3: Highly efficient catalyst for hydrogen production from hydrolysis of sodium borohydride

In this study, the Ni-based complex catalyst containing nickel of 1% supported on Al₂O₃ is used as for the hydrogen production from NaBH₄ hydrolysis. The maximum hydrogen production rate from hydrolysis of NaBH₄ with Ni-based complex catalyst supported on Al₂O₃ containing nickel of 1% is 62535 ml min^?1 g^?1 (complex catalyst containing 1 wt% Ni). The resulting complex catalyst is characterised by XRD, XPS, SEM, FT-IR, UV, and BET surface area analyses. The Arrhenius activation energy is found to be 27.29 kJ mol^?1 for the nickel-based complex catalyst supported on Al₂O₃. The reusability of the catalyst used in this study has also been investigated. The Ni-based complex catalyst supported on Al₂O₃ containing nickel of 1% is maintained the activity of 100% after the fifth use, compared to the first catalytic use. The n value for the reaction rate order of NaBH₄ is found to be about 0.33.     

Optimization of renewable hydrogen-rich syngas production from catalytic reforming of greenhouse gases (CH4 and CO2) over calcium iron oxide supported nickel catalyst

Multi-response optimization of hydrogen-rich syngas from catalytic reforming of greenhouses (methane and carbon dioxide over Calcium iron oxide supported Nickel (15 wt%Ni/CaFe₂O₄) catalyst was performed by varying reaction temperature (700–800 °C), feed ratio (0.4–1.0) and gas hourly space velocity (10,000–60,000 h^?1)) using response surface methodology. Four response surface methodology (RSM) models were obtained for the prediction of reactant conversion and the product yield. The analysis of variance (ANOVA) conducted on the model showed that the parameters have significant effect on the responses. Optimum conditions for the methane dry reforming over the 15 wt%Ni/CaFe₂O₄ catalyst were obtained at reaction temperature, feed ratio and gas hourly space velocity (GHSV) of 832.45 °C, 0.96 and 35,000 mL g^?1 h^?1 respectively with overall desirability value of 0.999 resulting in the highest methane (CH₄) and carbon dioxide (CO₂) conversions of 85.00%, 88.00% and hydrogen (H₂) and carbon monoxide (CO) yields of 77.82% and 75.76%, respectively.     

Upgrading of fast pyrolysis bio-oil over Fe modified ZSM-5 catalyst to enhance the formation of phenolic compounds

The present study is aimed to investigate the upgrading of beech sawdust pyrolysis bio-oil through catalytic cracking of its vapors over Fe-modified ZSM-5 zeolite in a fixed bed tubular reactor. The zeolite supported iron catalyst was successfully prepared with varying metal loading ratios (1, 5, 10 wt%) via dry impregnation method and further characterized by BET, XRD, and SEM-EDX techniques. TG/FT-IR/MS analysis was used for the detection of biomass thermal degradation. Product yields of non-catalytic and catalytic pyrolysis experiments were determined and the obtained results show that bio-oil yields decreased in the presence of catalysts. Besides, the bio-oil composition is characterized by GC/MS. It was indicated that the entity of the ZSM-5 and Fe/ZSM-5 catalyst reveal a significant enhancement quality of the pyrolysis products in comparison with non-catalytic experiment. The catalyst increased oxygen removal from the organic phase of bio-oil and further developed the production of desirable products such as phenolics and aromatic compounds.     

Steam reforming of model bio-oil compounds 2-butanone, 1-methoxy-2-propanol,ethyl acetate and butyraldehyde over Ni/Al2O3

Oil derived from fast pyrolysis of biomass (or bio-oil) is a candidate renewable feedstock for producing hydrogen (H₂). In this work, the steam reforming of model oxygenates present in the bio-oil aqueous fraction was studied in a fixed-bed reactor. Using Ni/Al₂O₃ catalyst, the reactions with 2-butanone, 1-methoxy-2-propanol, ethyl acetate and butyraldehyde were studied. To study the efficacy of the chosen catalyst for H₂ production, experiments were performed in the 623–773 K range using varying steam/carbon ratios in feed (15–25 mol/mol). The conversion of the various feeds was of the order: butyraldehyde > ethyl acetate > 1-methoxy-2-propanol > 2-butanone. The catalyst was characterized using SEM, XRD, TPR/TPD and TGA methods. It showed high stability for 7 h of time-on-stream.     

Upgrading of fast pyrolysis bio-oil to drop-in fuel over Ru catalysts

Catalyst plays a key role in the upgrading of fast pyrolysis bio-oil to advanced drop-in fuel, while the selectivity and deactivation of catalyst still remain the biggest challenge. In this study, three Ru catalysts with activated carbon, Al₂O₃ and ZSM-5 as supports were prepared and tested in bio-oil hydrotreating process. The physical properties and components of upgraded bio-oil were detected to identify the difference in catalytic performance of three catalysts. The results showed that furan, phenols and their derivatives in fast pyrolysis bio-oil could be hydrogenated to alkanes, alkenes and benzenes over Ru catalysts. The different components of oil phase over three catalysts may be resulted from the surface properties of three supports. Activated carbon supported Ru catalyst showed the best catalytic performance and was suggested to be the most promising catalyst for pyrolysis bio-oil upgrading.