Fixed-bed Tubular Reactor Research Articles

Experimental investigation of fixed-bed pyrolysis and steam gasification of food waste blended with woody biomass

The co-pyrolysis and co-gasification of woody biomass (oak) blended with food waste in a 2:1 ratio were investigated in a fixed bed tubular reactor. Gas compositions, gas yields, LHVs, H2/CO ratios and carbon conversions were evaluated between 700 and 900 °C reactor temperature and 7–22 g h−1 steam flow rate. The highest LHV of 11.03 MJ m−3 was measured during gasification at 900 °C reactor temperature with 7 g h−1 steam flow, and the LHV remained similar in both pyrolysis and gasification period. Typically, the H2/CO ratio ranged between 0.53 and 0.81 during pyrolysis, however, the ratio decreased by increasing the temperature. The gasification performed at 900 °C reactor temperature and 22 g h−1 steam flow resulted the most promising H2/CO ratio of 2.03 which has a great potential for further chemical processing. Additionally, the highest carbon conversion (99.7%) and gas yield (888.7 l kg−1) were measured at these conditions. Based on the results the co-pyrolysis and co-gasification of woody biomass and food waste is a viable method to reduce the accumulation of food waste and generate value added products.

One-step conversion of syngas to hydrocarbons and ethers over ZIF-8 derived ZnO coupling HZSM-5

Zeolitic imidazolate frameworks (ZIF-8) were synthesized by solvothermal method. Used as precursor, ZIF-8 was decomposed into nanoparticles ZnO at different pyrolysis temperature in air atmosphere. The composition, structure and crystal size of ZnO were characterized by XRD, TEM, XPS, and Raman methods. The ZnO nanoparticles were coupled with HZSM-5 to form bifunctional catalysts. The catalytic performances of bifunctional catalysts in the syngas conversion were investigated in a fixed-bed tubular reactor. The results demonstrate that the pyrolysis temperature has an important influence on the particle size of ZnO. The temperature affects the rate of grain formation. High temperature promotes the aggregation of ZnO. The ZnO grain size by changing the temperature plays a role in changing the product distribution. When the pyrolysis temperature is near or below 450°C, carbon-coated ZnO nanoparticles are obtained, and the ZnO grain size is less than 20 nm. The carbon-coated ZnO coupled with HZSM-5 catalyzes syngas mainly into dimethyl ether (DME). When the temperature is higher than 450°C, pure phase ZnO nanoparticles are obtained, and the ZnO grain size is larger than 20 nm. The pure ZnO coupled with HZSM-5 catalyzes syngas mainly into hydrocarbons. Obviously, the coupling modes of ZnO and HZSM-5 have a significant effect on the product selectivity of bifunctional catalysts.

Hydrogen production via CO2[sbnd]CH4 reforming over cobalt-supported mesoporous alumina: A kinetic evaluation

The performance of cobalt supported on mesoporous alumina (MA) under the influence of reaction temperature (923 K–1073 K) and reactant partial pressure (10 kPa–40 kPa) for CO2–CH4 reforming was executed by using a tubular fixed-bed reactor. 10%Co/MA exhibited great catalytic performance (XCH4=70.9%, XCO2=71.7% andDa=1.3%), credited to the well dispersion of Co within pore MA, strong metal-support interaction, and MA confinement ability. Based on Langmuir-Hinshelwood kinetic analysis, the dissociative adsorption of both reactants on a single Co active site was selected for this study. The lower value of activation energy (28.9 kJ mol−1) suggested that Co particles were finely scattered on the MA surface. Regardless of carbon types, the amount of coke accumulated on the spent 10%Co/MA within 8 h of CO2–CH4 reforming was inhibited due to fine Co distribution inside MA structure, as well as lessened with the raise of reforming temperature from 923 to 1073 K due to improvement in reverse Boudouard reaction.

Hydrocracking of Fischer-Tropsch Wax

The low-temperature Fischer-Tropsch synthesis (LTFT) processing of renewable feedstocks combined with the hydrocracking of its solid product is an effective way to produce synthetic renewable engine fuels. The hydrocracking of an FT wax derived from natural gas using the LTFT synthesis was studied in this paper. The hydrocracking was carried out in a tubular fixed-bed reactor with a cocurrent flow of the feedstock and hydrogen. Reaction temperatures in the range of 305– 370 °C, a pressure of 8 MPa, an H2/feed ratio of 500 m3/m3 and weight hour space velocities (WHSV) of 1; 2 and 4 h-1 were tested. The naphtha fraction (boiling up to 200 °C) was the main product of the hydrocracking under all the tested reaction conditions. It could be used as a component into petroleum-derived gasoline in a neat form or the after processing by common refinery processes (isomerization and/or reforming). The production of low-sulfur and low-aromatic paraffinic solvent or the utilization as a feedstock for steam cracking could be some other options of the naphtha fraction utilization. The maximum yield of the gaseous products (depending on the reaction temperatures and WHSV) was 20 wt.%. They were primarily composed of n-alkanes and isoalkanes and could be, therefore, used as an optimal feedstock for steam cracking as well. The C3-C4 fraction of the gaseous products could be also utilized as an LPG fuel. Very low yields (up to 10.4 wt.%) of the middle distillates were obtained under all the tested reaction conditions. Due to their saturated nature, their densities were very low and, additionally, poor low-temperature properties can be expected.

Hydrotreating of Methyl Esters to Produce Green Diesel over Co- and Ni-Containing Zr-SBA-15 Catalysts

This work explores the performance of Zr-SBA-15 as a support for the conversion of methyl esters into green diesel. Thereby, a series of SBA-15 samples incorporating different amounts of Zr into the walls have been synthesized and impregnated with Ni and Co as hydrogenating species. All materials have been characterized, pelletized and tested in the hydrotreating of methyl esters using a fixed-bed tubular reactor at 300 °C, 30 bar of H2 and a continuous flow of 0.1 mL/min for 6 h. Co and Ni phases are present both over the surface and within the pores of the support. Interactions between the metals and the Zr species are more pronounced for Co-containing samples, leading to smaller Co particles at low Si/Zr ratios. Materials having higher Zr contents resulted in more methyl ester conversion, although an adequate metal-support combination was required to promote the hydrodeoxygenation (HDO) route. Co/Zr-SBA-15 materials exhibited more conversion (>90%) and higher yields of C11-C20 hydrocarbons (>60%) than their Ni-based counterpart catalysts. Specifically, Co/Zr-SBA-15(17) sample showed remarkable behavior, favoring the HDO pathway (n-C18/(n-C18 + n-C17) > 0.5), while keeping the methyl esters’ conversion close to 100% along the time on stream. These results evidence a synergistic effect between Co and Zr.

Parametric Studies on Hydrodeoxygenation of Rubber Seed Oil for Diesel Range Hydrocarbon Production

Hydrodeoxygenation (HDO) is considered as a substantial path for cleaner production of fatty acids and triglycerides into diesel range hydrocarbons (DRHs) (C15–C18) generally identified as green diesel fuel. Heterogeneous catalysis suggests a supplementary approach for the conversion of biomass into significant biochemicals possibly selective hydrocarbons by an inventive method. The present study reveals the optimization of reaction parameters for the process of HDO of rubber seed oil (RSO) over the transition metal NiMo/γ-Al₂O₃ (NMA) catalyst (designed via sonochemical co-impregnation approach) into DRHs, that is, n-C15-n-C18. The comprehensive studies have been performed to investigate the parametric effects employing response surface methodology using central composite design. The experimental design was conducted on the four most influential operating factors, namely, temperature within the range of 300–400 °C, weight hourly space velocity (WHSV) (1–3 h–¹), H₂/oil ratio (400–1000 N (cm³/cm³)), and pressure (30–80 bar), for triglyceride conversion and DRH yield. All the experimental runs were performed in continuous process using a fixed bed tubular reactor over the NMA catalyst. The product analysis showed that triglycerides are completely hydrodeoxygenated into DRHs with an optimum production of 84.94 wt % yield led by prime reaction conditions at a temperature of 400 °C, WHSV of 1 h–¹, pressure of 80 bar, and H₂/oil ratio of 400 N (cm³/cm³). The parametric interaction between temperature and WHSV has significantly influenced the diesel yield. The investigations validated that HDO tracked the corresponding reaction condition in competitive mode and obligated the diverse optimum and limiting reaction conditions. In addition, deactivation of the catalyst study was performed at the optimized reaction condition. The catalyst was found to be active until 18 h without bringing to sulfidization process with 80% diesel yield and 100% triglyceride conversion. The slight deactivation of the catalyst is observed, with a very small amount coke deposition even after 18 h of time on stream at the optimized reaction condition. The novelty of the present study lies in the performance of sonochemically synthesized catalyst for HDO of RSO to produce green diesel and to optimize the reaction condition and catalysts deactivation performance at optimized reaction conditions.

Biogas dry reforming over Ni-Al catalyst: Suppression of carbon deposition by catalyst preparation and activation

Biogas dry reforming is as an alternative renewable route for the hydrogen production. However, the major drawback of this process is the catalyst deactivation by carbon deposition and sintering. In this work, Ni-Al catalysts were studied aiming to suppress the carbon deposition in the dry reforming of biogas. The catalysts were prepared by coprecipitation and evaluated the washing step. The reactions were carried out with unreduced and reduced catalysts in a fixed bed tubular reactor using a synthetic biogas (60% CH4 and 40% CO2). The washing and activation steps influenced the characteristics of the catalysts and the catalytic properties in the biogas reforming. The unwashed sample resulted in an oxide containing potassium nickelate with high basicity and low surface area. Both washed samples, reduced and unreduced, showed a high amount of carbon formation, whereas no carbon formation was observed in the unwashed samples for the reactions in the temperature range of 500–750 °C. The unwashed and unreduced sample was the only one that maintained the activity during all the reaction time at 700 °C (40% CH4 conversion and 75% CO2 conversion), low coke amount and no evidence of sintering, which was confirmed by XRD, TPO, and SEM analyses. The carbon suppression was related to the nickelate phase and to the Ni carbide formation in the unwashed and unreduced catalyst. In summary, the carbon deposition in biogas dry reforming was completely controlled between 600 and 750 °C using the unwashed and unreduced Ni-Al catalyst.

Tuning metal-support interaction and oxygen vacancies of ceria supported nickel catalysts by Tb doping for n-dodecane steam reforming

Hydrogen is a green and efficient energy carrier that can be applied directly in fuel cell system. On-board/on-site hydrogen production for a portable fuel cell is urgently required, and catalytic steam reforming of liquid hydrocarbons is a promising pathway. In this context, Ni catalysts supported on various Tb-doped ceria were synthesized by a citric-acid-assisted sol-gel method. The textural and physicochemical properties of the fresh and spent catalysts were characterized by different techniques including XRD, N2 physical adsorption, H2-TPR, H2-TPD, TEM, SEM, XPS, EPR, TG and Raman. Catalytic performance of the as-prepared catalysts was evaluated in steam reforming of n-dodecane. The conversion of n-dodecane and hydrogen production rate were measured at LHSV of 10 ml/gcat·h and H2O/C = 2 and 4 in a fixed-bed tubular reactor. The reaction data showed that Tb dopant affected both the conversion of n-dodecane and the gas product composition. The origins of the improved performance by Tb doping were investigated, in which the moderate interaction between metal and support, highly dispersed Ni particles, increased basicity sites and abundant surface oxygen vacancies play key roles.

Hydrogen production by glycerol steam reforming over Ni based catalysts prepared by different methods

Ni supported and co-precipitated catalysts promoted by Mg were evaluated for hydrogen production by the glycerol steam reforming. The samples were prepared by incipient wetness impregnation of alumina and by the continuous co-precipitation method. The catalysts were characterized by XRD, SBET, TPR, NH3-TPD, TPO and SEM/TEM. The catalytic tests were performed in the range from 500 to 650 °C in a fixed bed tubular reactor. The gaseous products were analyzed online by gas chromatography. It was found that the partial substitution of Ni by Mg improves the dispersion of Ni, decreases the acidity of the catalysts and increases the resistance to sintering of Ni. The unreduced catalysts presented higher selectivity for H2 than the previously reduced catalysts. The catalyst unreduced impregnated with 20% Ni showed the highest selectivity in the production of hydrogen (55%), at the temperature of 650 °C. Unreduced samples prepared by co-precipitation presented smaller Ni0 crystallite size after the reaction. The catalyst reduction step is unnecessary for this reaction.

Kinetic Study Based on the Carbide Mechanism of a Co-Pt/γ-Al2O3 Fischer–Tropsch Catalyst Tested in a Laboratory-Scale Tubular Reactor

A Co-Pt/γ-Al2O3 catalyst was manufactured and tested for Fischer–Tropsch applications. Catalyst kinetic experiments were performed using a tubular fixed-bed reactor system. The operative conditions were varied between 478 and 503 K, 15 and 30 bar, H2/CO molar ratio 1.06 and 2.11 at a carbon monoxide conversion level of about 10%. Several kinetic models were derived, and a carbide mechanism model was chosen, taking into account an increasing value of termination energy for α-olefins with increasing carbon numbers. In order to assess catalyst suitability for the determination of reaction kinetics and comparability to similar Fischer–Tropsch Synthesis (FTS) applications, the catalyst was characterized with gas sorption analysis, temperature-programmed reduction (TPR), and X-ray diffraction (XRD) techniques. The kinetic model developed is capable of describing the intrinsic behavior of the catalyst correctly. It accounts for the main deviations from the typical Anderson-Schulz-Flory distribution for Fischer–Tropsch products, with calculated activation energies and adsorption enthalpies in line with values available from the literature. The model suitably predicts the formation rates of methane and ethylene, as well as of the other α-olefins. Furthermore, it properly estimates high molecular weight n-paraffin formation up to carbon number C80.

Experimental Study on Catalytic Oxidation of Toluene with Manganese Catalysts and Ozone at Low Temperature

The single metal oxide catalyst of transition metal element Mn and the composite metal oxide catalysts of Mn-Co and Mn-Fe are prepared by impregnation method using activated carbon (AC) as carrier. The catalysts are characterized by x-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The performance of the catalysts for catalytic ozonation of toluene is tested in a fixed bed tubular reactor. The results show that the activity of the single metal oxide catalyst of Mn is lower than that of the composite metal oxide catalysts of Mn-Co and Mn-Fe, and the activity of Mn-Co is higher than that of Mn-Fe. The catalytic efficiency of three catalysts is Mn/AC< Mn-Fe/AC> Mn-Co/AC. In this study, the factors influencing the degradation of toluene by catalytic ozonation are analyzed, and the mechanism is explored.

Zn‐Al hydrotalcite‐derived Co x Zn y AlO z catalysts for hydrogen generation by auto‐thermal reforming of acetic acid

Auto-thermal reforming (ATR) of acetic acid (HAc) is considered as a promising route for hydrogen generation from renewable resources, while oxidation, coking, and sintering need to be addressed for durable catalysts in ATR. In the current work, Zn-Al hydrotalcite-derived CoxZnyAlOz catalysts were prepared by co-precipitation and evaluated in a fixed-bed tubular quartz continuous-flow reactor. The Co0.70Zn3.30AlO5.5 ± δ catalyst presented a HAc conversation near 100% and a stable hydrogen yield near 3.01 mol-H2/mol-HAc. The characterization results of XRD, H2-TPR, BET, SEM, XPS, and TG indicated that the hydrotalcite structure was obtained via co-precipitation method; over the hydrotalcite-derived mixed oxides, (a) the specific surface area was increased with high dispersion of Co, (b) the phases of ZnO with spinel of ZnAl2O4,CoAl2O4, Co3O4, and ZnCo2O4 were beneficial to improve resistance to coking and oxidation, and (c) the relative stability of Co species over ZnO and spinel phases helps to suppress sintering. Meanwhile, ratio of O/C and temperatures near 0.28 and 650 °C, respectively, were also evaluated and proposed as optimized conditions for hydrogen generation, and the durable Co0.70Zn3.30AlO5.5 ± δ catalyst produced a rate of 114.9 mmol-H2/s/g-catalyst in a 15-hour ATR test, showing promising potential for hydrogen generation.

Biogas dry reforming for hydrogen production over Ni-M-Al catalysts (M = Mg, Li, Ca, La, Cu, Co, Zn)

Biogas can be highlighted as a renewable raw material for the production of hydrogen. In this study, Ni-M-Al catalysts were evaluated to obtain hydrogen from the biogas reforming. The catalysts were synthesized by coprecipitation with Ni and Al with a molar percentage of 55 and 33%, respectively, varying the third component M = Mg, Li, Ca, La, Cu, Co, Zn, with a molar percentage of 11%. The reactions were carried out in a fixed bed tubular reactor using a synthetic biogas (70% of CH4 and 30% of CO2). The results showed that the CH4 conversion increased with the temperature up to 700 °C for La11, Cu11, and Zn11 catalysts. CO2 conversion increased for all catalysts in the range of 500–700 °C. The H2/CO molar ratios observed in the reactions were higher than 1 due to the contribution of the CH4 decomposition reaction. The catalyst containing La presented better stability in the reactions due to the stronger acid sites and high resistance to sintering. Carbon filaments were produced by all catalysts at 600 and 700 °C. Sintering was the main cause of deactivation of the catalysts, except for La11.

Facile preparation of highly thermal conductive ZnAl2O4@Al composites as efficient supports for cobalt-based Fischer-Tropsch synthesis

The development of alternative to silicon carbide (SiC) holds great promise in energy and environmental related catalysis because the harsh preparation process and high cost limit its large-scale application. In this work, the core-shell structured ZnAl2O4@Al ceramic-metal composites (Zn-Al-T) are prepared from low cost metallic Al powder by a facile and environment-friendly approach to replace silicon carbide for Co-based Fischer-Tropsch synthesis (FTS, a typical strong exothermic heterogeneous catalytic reaction). The composition, thermal conductivity, surface chemical properties and pore configuration of the ZnAl2O4@Al composites can be easily modulated by controlling the calcination condition. Among Zn-Al-T composites, the Zn-Al-650 and Zn-Al-750 samples demonstrate optimum coupling of physicochemical properties, i.e., robust chemical stability, meso-macropore structure (wide mesopore and high macroporosity) and high thermal conductivity. Thus, the excellent FT performance (low CH4 selectivity and high selectivity to C5+) was obtained on the Co/Zn-Al-650 and Co/Zn-Al-750 catalysts. The heat transfer experiments were conducted on a special tubular fixed-bed reactor (I.D. = 22 mm) under near-industrial conditions. At similar reaction rates, the effective radial thermal conductivity coefficient (keaff) in the Co/Zn-Al-650 catalyst bed is 3–4 times and 1–2 times that in the Co/Al2O3 and Co/SiC catalyst beds respectively, resulting in a more uniform temperature distribution in Co/Zn-Al-650 catalyst bed. In addition, the ZnAl2O4@Al composite has wide application prospect in strong exothermic/endothermic catalytic system owing to its high thermal conductivity, adjustable physico-chemical properties, facile preparation method and low cost.

Experimental study on H2S adsorption on gasification char under different operative conditions

Char is the solid by-product of biomass gasification. It usually represents a cost for plant owners, who have to dispose of it at a cost. However, its high carbon content and surface area could make it suitable for further applications, such as adsorption. In this work, we studied its potential for the adsorptive removal of hydrogen sulphide (H2S), a common pollutant present in the producer gas of gasification, as well as in biogas from anaerobic digestion. Different samples of char collected from commercial gasification plants in South Tyrol (Italy) were tested. The adsorption was reproduced in a lab-scale tubular fixed-bed reactor. The results highlight that all samples could capture hydrogen sulphide, showing different adsorption performances. The materials’ specific surface area and metal and oxygen content seem to affect the removal capacity. After these tests, we selected the best-performing char, and tested its adsorption performance in different operative conditions, i.e. at different inlet concentrations of H2S and temperatures.

Pyrolysis and characterization of &lt;i&gt;Jatropha curcas&lt;/i&gt; shell and seed coat

The utilization of dedicated energy crops and agricultural residues for producing biofuels and bio-oil in a range of energy conversion technology is attracting more research interests. Pyrolysis is one of such important thermochemical method for converting lignocellulosic biomass into biofuels. This work investigates the pyrolysis of residues from a dedicated energy crop, jatropha of Nigerian origin using intermediate pyrolysis. Pyrolysis of Jatropha biomass residues [Jatropha fruit shells (JFS) and Jatropha seed coat (JSC)] was carried out in a tubular fixed bed reactor at a temperature of 450 o C, using intermediate pyrolysis method. Bio-oils were obtained and subsequently characterised for their physico-chemical properties. The yields of the resulting bio-oil, biochar and gas were determined. The compositions of the bio-oils obtained were also determined by gas-chromatography mass spectrometry (GC-MS) and carbon, hydrogen, nitrogen, sulphur (CHNS) elemental analysis. The main constituents of the bio-oils obtained from JFS and JSC were acetic acid, guaiacol, 2,6-dimethoxyphenol and phenol. The empirical formula of the obtained JFS and JSC bio-oils were found to be CH 1.77 O 0.28 N 0.04 and CH 2.03 O 0.47 N 0.04 respectively. The bio-oil samples that were produced from JSC and JFS of Nigerian origin were found suitable for bio-oil production. Valuable compounds found in the bio-oils indicated potential industrial applications. Keywords: Jatropha shell, pyrolysis, biomass waste, biofuel, bio-products

The Effect of Hydrolysis on Properties of Soot and Tar During the Pyrolysis of Sewage Sludge

In this study, we evaluate the effect of hydrolysis treatment on the properties of tar and soot produced during the pyrolysis of sewage sludge at different operating temperatures (500–800 °C). The pyrolysis experiments were performed in a two-stage tubular fixed-bed reactor at atmospheric pressure. Raw sludge and hydrolysis-treated sludge (at pressure of 0.4 MPa and temperature 200 °C) samples were collected from local municipal sewage sludge treatment plant. The tar and soot samples obtained from pyrolysis at different temperatures were characterized by gas chromatography–mass spectrometry and scanning electron microscopy with energy dispersive X-ray spectroscopy, respectively. The results showed that increase in the pyrolysis temperature decreases the tar and soot yield for both raw and hydrolysis-treated sludge. The minimum tar yield was achieved with hydrolysis-treated sludge at 800 °C. The soot from raw sludge pyrolysis was of greater yield at high temperature than hydrolysis-treated sludge pyrolysis. The tar from pyrolysis of hydrolysis-treated sludge had more aliphatic character as compared to raw sewage sludge. The formation of heavy polycyclic aromatic hydrocarbons during pyrolysis of hydrolysis-treated sludge was lower at high temperatures than that of raw sludge. The aromatic hydrocarbons yield of hydrolysis-treated sludge was higher as compared to raw sludge at 800 °C.

Low-cost preparation of carbon-supported cobalt catalysts from MOFs and their performance in CO hydrogenation

Abstract With terephthalic acid (H2BDC) as ligand and cobalt acetate as Co source, metal-organic frameworks (Co-BDC MOFs) were synthesized in water by co-precipitation; after that, core-shell Co@C catalysts were prepared by chemical vapor deposition (CVD) of Co-BDC MOFs in acetylene and Ar atmosphere. The structure, composition and properties of Co@C catalysts were characterized by XRD, nitrogen physisorption, SEM, TEM, XPS, TGA and Raman spectroscopy and their catalytic performance in Fischer-Tropsch synthesis (FTS) were investigated in a fixed-bed tubular reactor. The results demonstrated that the carbonization atmosphere has an important influence on the graphitization degree of carbon shell, whereas has little effect on the phase and size of Co core. The pore of graphite shell is significantly improved by CVD in acetylene, which can enhance the selectivity to heavier hydrocarbons (C5+) for CO hydrogenation; in particular, the Co@C-C2H2 catalyst shows a high selectivity of 82.66% to the C5+ hydrocarbons. As the carbon shell can effectively inhibit the cobalt nanoparticles from migration and agglomeration during the FTS reaction, the Co species were well distributed in both the fresh and spent catalysts and no significant sintering and deactivation are observed for the Co@C catalysts upon the FTS tests. During the FTS reaction, the active phase changes from metallic Co to a mixture of metallic Co and Co2C, whilst the catalytic activity of Co@C-C2H2 keeps almost unchanged, suggesting that Co2C may also be an active phase for the Fischer-Tropsch synthesis.

The effect of metal loading over Ni/γ-Al2O3 and Mo/γ-Al2O3 catalysts on reaction routes of hydrodeoxygenation of rubber seed oil for green diesel production

Abstract Hydrodeoxygenation (HDO) of vegetable oil is one of the promising key processes designed for a possible convenient method for automotive clean fuel production. The HDO of rubber seed oil into diesel range hydrocarbon over non-sulphided monometallic (Ni/γ-Al2O3 and Mo/γ-Al2O3) catalysts were investigated. The catalysts were synthesized via conventional wet impregnation method using 3 wt.%, 12 wt.% and 15 wt.% Ni and Mo loading over γ-Al2O3 support, to examine the influence of metal loading on catalytic activity, coke deposition, and reaction routes. The synthesized catalysts were subjected to characterization techniques including XRD, FESEM coupled with EDX, BET, TEM, TGA, ICP-OES and H2TPR. All the catalysts were tested for HDO reaction at 623.15 K, 3.5 MPa, H2/oil of 1000 N (cm3/cm3) with WHSV = 1 h−1 in a continuous flow fixed bed tubular reactor. The hydrocarbon products were analyzed using gas chromatography, and intermediates were identified using GC–MS. The Ni supported catalysts showed comparatively higher surface area, small particle size, homogeneous dispersion of particles, higher crystallinity and lower reduction temperature, low coke deposition. Proposed reaction mechanism suggests the decarboxylation (DCO2) reaction occurred mainly over Ni supported catalysts. Whereas, higher Ni loading reduced the extent of decarboxylation (DCO2) reaction. Additionally, Mo supported catalysts allowed the deoxygenation reaction to occur and higher Mo loading enhanced the extent of hydrodeoxygenation (HDO). The triglycerides conversion for all the catalysts was 99.9%. The catalysts with higher metal loading showed overall higher catalytic activity for hydrodeoxygenation of RSO. 15 wt.% Ni loading produced higher hydrocarbon yield (55.1 wt.%) whereas, 15 wt.% Mo loading produced up to 61.7 wt.%. Mo comparatively produced high amount of C16 (15.7 wt.%), and C18 (30.7 wt.%) hydrocarbons. Whereas, Ni produced mainly C15 (20.9 wt.%) and C17 (20.3 wt.%) hydrocarbons. Significant findings were observed on hydrocarbon yield, intermediates, and amount of coke formation. Mo supported catalysts shows significant HDO activity with less concentration of oxygenated component in the mixture. Besides Mo supported catalysts exhibit the high amount of coke deposition compared to Ni supported catalysts.

Hydrogen-rich gas production by steam and oxidative steam reforming of crude glycerol over Ni-La-Me mixed oxide catalysts (Me= Ce and/or Zr)

Abstract The production of H2-rich gaseous mixtures from steam and oxidative steam reforming of crude glycerol was investigated on catalysts with general formula Ni(12 wt.%)-La2(Ce1-xZrx)2O7 (x = 0, 0.5, 1). The catalysts were prepared by the polymerized complex method based on the Pechini-type reaction route and characterized by a variety of physical and spectroscopic techniques. Samples were calcined in air at 850 °C for 4 h. All catalysts showed a well-defined NiO phase and a mixed oxide with a general formula A2B2O7 (A: La; B: Ce and/or Zr). NiO was completely reduced to metallic Ni on all catalysts under pure H2 at 650 °C. Ni reducibility is favored by the presence of Ce. Redox properties of Ce can also explain a synergetic effect leading to the higher basicity of the catalyst containing Ce and Zr (x = 0.5). Catalytic tests were performed at 650 °C by feeding the fixed-bed tubular reactor with a crude glycerol:water solution containing 30 wt% glycerol. The best results were achieved on the catalyst displaying the highest basicity (Ni-La2(Ce0.5Zr0.5)2O7 both under steam and oxidative reforming conditions. Removal of carbon and alkali metals by simple procedures allows to a significant recovery of the initial catalytic activity without changes in their chemical and phase structure.