Catalyst Weight Ratio Research Articles

Alumina-supported multi-metal catalyst for e-waste management for reclamation of valuable products

ABSTRACT Electronic and electrical waste (e-waste) has increased exponentially due to the humungous growth in the information technology and communication sector. Many multi-metal catalysts are developed by researchers for electronic waste plastic conversion into fuel products and recovery of valuable metals. In the present study, an Alumina-supported catalyst powder with selected transition metals metal oxides was prepared to improve the yield of hydrocarbon liquids. FESEM with energy-dispersive spectroscopy, XRD and laser diffraction particle size analysis were used to characterise catalysts. The shredded e-waste chips to catalyst weight ratio was maintained from 2:1 to 10:1 and studied. The experiments were conducted with a reaction temperature range from 300°C to 500°C. The produced fuel density was 0.88 kg/L, with 0.75 liquid fuel conversion and 71.7% overall liquid fuel yield. The light gas percentage was 4–6%. NMR analysis, bomb calorimetric study and gas chromatography-mass spectroscopy of liquid fuel analysis suggest carbon chain compounds of C3–C20 hydrocarbon, indicating a mixture of petrol and diesel-like liquid products. The catalyst can be tuned to improve liquid fuel conversion. The liquid fuel product is promising for fuel use, however, upgrading treatments are needed to meet standard product specifications.

Maximizing High Value Light Products by Catalytic Cracking of VGO Produced by Iraqi Refinery over Formulated FCC Catalyst

Prototype of FCC catalyst were formulated by mixing the stabilised Y zeolites (68wt%) with polyvinal alcohol (PVA) (7%) as a solution binder and bentonite (25%). The Y zeolite including the original HY with Si/Al of 2.6 (cat.-2.6) and dealuminated HY with Si/Al of 30 (cat.-30) were used and tested for catalytic cracking of Iraqi vacuum gas oil (VGO) obtained from Al-Dura refinery using a pilot plant. The cracking process was carried out at a temperature of 520 °C and atmospheric pressure, The weight ratio of catalyst / oil ratio was 3 and 5. The results show that higher conversion of 77 wt. % and better product distribution (gasoline, kerosene and gas oil) could be obtained over cat.30 resulting to a good liquid product yield. The catalytic activity, in terms of VGO conversion was not affected over cat.-30 in spite of its lower acidity, suggesting the determinate of mesoporosity in the Y zeolite (cat.-30) catalysed cracking reactions. A higher yield of ~ 67 wt% to mid-distillates (i.e.Naphtha and kerosene) was as a result of the improvements in the diffusion to and from catalyst structure.

Highly Selective Bio-hydrocarbon Production using Sidoarjo Mud Based-Catalysts in the Hydrocracking of Waste Palm Cooking Oil

In this work, Lapindo mud (LM) was used as catalyst support. This is because the Lapindo mud has a high SiO2 content of 45.33 %. This research aims to produce a hydrocracking catalyst based on Lapindo mud through impregnation of Ni and Pt metals as well as grafting amine groups. Ni and Pt metals impregnation using wet impregnation method followed by amine group grafting. The best catalyst in this study was NiPt-NH2/LM which contained Ni and Pt metals, surface area, and pore diameters of 1.68 wt.% and 0.4 wt.%, 6.59 m2/g, 15.51 nm, respectively. The effectiveness of the catalyst was tested against temperature and catalyst: feed ratio. The catalyst with the best activity and selectivity was tested for reusability 3 times through hydrocracking process. The yield of liquid products obtained in the hydrocracking process of WPO using NiPt-NH2/LM catalyst with the optimum temperature and the weight ratio of catalyst:feed at 550 oC was 79.4 wt. % which consists of hydrocarbon compound of 55.9 wt.%. The yield of liquid products obtained in the hydrocracking WPO using the used NiPt-BH2/LM catalyst was 28.4 wt.% which consists of hydrocarbon compound of 23.6 wt.%. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Kinetics of Catalytic Decarboxylation of Naphthenic Acids over HZSM-5 Zeolite Catalyst

Naphthenic acids are naturally occurring carboxylic acids in crude oil with cyclic or aromatic rings in their structure. These carboxylic acids are responsible for the acidity of crude oil, leading to corrosion problems in refinery equipment and the deactivation of catalysts while creating a continuous need for maintenance. Therefore, removing naphthenic acids has become an important requirement in refining acidic crude oil. In this paper, experiments are conducted to investigate the use of HZSM-5 zeolite catalyst to reduce the total acid number (TAN) of a typical acidic crude oil obtained from Al-Fula blocks in Western Sudan. TAN is an important metric signifying the acidity of crude oil. A full factorial design of the experiment (DOE) framework enabled a better understanding of the efficacy of the catalyst at three parametric levels (reaction temperature: 250-270-300 °C, reaction time: 2-3-4 h, and oil:catalyst weight ratio: 20-22-25 g/g). The results demonstrate that the HZSM-5 zeolite catalyst provides up to 99% removal of naphthenic acids via the decarboxylation route. Additionally, the removal efficiency increases with increasing temperature and residence time. The acidity of the crude oil was shown to decrease after treatment with the catalyst for four hrs.; from 6.5 mg KOH/g crude to 1.24; 0.39 and 0.17 mg KOH/g at 250; 270 and 300 °C, respectively. A sharp decrease of TAN was observed at the oil catalyst mass ratio of 20 g/g at 250 °C, and almost complete conversion of acids was achieved after 4 hrs. Another experiment at 270 °C showed a converse relationship between the oil:catalyst ratio and acid removal; suggesting the activation of side reactions at higher temperature conditions catalyzed by excess acid. Finally; a Langmuir–Hinshelwood (LH) kinetic model has been developed to enable rapid prediction of the performance of the HZSM-5 zeolite catalyst for decarboxylation reaction. The model has also been validated and tested in ASPEN® software for future simulation and scalability studies.

Catalytic Production of Levulinic and Formic Acids from Fructose over Superacid ZrO2–SiO2–SnO2 Catalyst

Catalytic conversion of fructose to levulinic and formic acids over tin-containing superacid (H0 = −14.52) mixed oxide was studied. Mesoporous ZrO2–SiO2–SnO2 (Zr:Si:Sn = 1:2:0.4) was synthesized by the sol–gel method. The fructose transformation was carried out in a rotated autoclave at 160–190 °C for 1–5 h using a 20 wt.% aqueous solution. The results showed that doping ZrO2–SiO2 samples with Sn4+ ions improved both fructose conversion and selectivity toward levulinic and formic acids. Under optimal conditions of 180 °C, 3.5 h and fructose to catalyst weight ratio 20:1, levulinic and formic acids yields were 80% and 90%, respectively, at complete fructose conversion. At this, humic substances formed in the quantity of 10 wt.% based on the target products.

Mesoporous Silica from Parangtritis Beach Sand Templated by CTAB as a Support of Mo Metal as a Catalyst for Hydrocracking of Waste Palm Cooking Oil into Biofuel

In this study, natural source Parangtritis beach sand was extracted into mesoporous silica (MS). Synthesis of mesoporous silica (MS) was carried out at sodium silicate: CTAB ratio of 1:0.5 (w/w). Monometallic catalyst was used to improve the performance of the catalyst. The monometallic used was Mo metal, which was synthesized using the wet impregnation method. Catalysts were characterized using FTIR, XRD, Surface Area Analyzer (SAA), SEM–EDX, and TEM. MS has pore diameters and surface area of 2.62 nm and 897.3 m2/g, respectively. Mo/MS has pore diameters, surface area, and Mo metal concentration of 2.46 nm, 593 m2/g, and 4.75%, respectively. Catalytic activity and selectivity were evaluated in hydrocracking of waste palm cooking oil at 500, 550, and 600 °C, and catalyst: waste palm cooking oil ratio of 1:100, 1:200, and 1:300. The best catalyst will be tested for reusability 3 times through the hydrocracking process. Mo/MS produces better liquid products and hydrocarbon compounds than MS. The results of the conversion of liquid products analyzed using GCMS. The yield of liquid products obtained in the hydrocracking of waste palm cooking oil using Mo/MS with the optimum temperature and the weight ratio of catalyst: feed at 550 °C and 1: 300 was 66.99 wt.% with consists of hydrocarbon compound as 62.79 wt.%. The yield of liquid products obtained in the hydrocracking waste palm cooking oil using the used Mo/MS catalyst in the last run was 80.26 wt.% with consist of hydrocarbon compound as 74.13 wt.%.Graphic Abstract

ANALYSIS AND COMPARISON OF THE FUEL PROPERTIES OF BIO-OILS PRODUCED BY CATALYTIC FAST PYROLYSIS OF Tectona grandis

This study analyzed the fuel properties of bio-oils produced by catalytic fast pyrolysis of Tectona grandis in a fixed bed reactor at different temperatures (400 – 600 oC) and biomass to catalyst (b/c) weight ratios (90/10 – 60/40). Magnesium oxide (MgO) was used as catalyst. The product yields were determined. Bio-oils were characterized with their elemental composition and their Higher Heating Values (HHVs) as well as their basic fuel properties at maximum bio-oil yields conditions, including viscosity, flash point, moisture content, pH value and Conradson Carbon Residue (CCR), were determined and compared with those of non-catalytic pyrolysis bio-oils. The maximum yields of bio-oil at 400, 500 and 600 oC were 31.53, 40.87 and 29.30 wt.%, respectively, obtained at b/c ratios of 70/30, 80/20 and 70/30. Catalytic pyrolysis bio-oils possessed higher carbon and hydrogen but lower oxygen and sulphur contents than non-catalytic pyrolysis bio-oils. The HHVs of catalytic pyrolysis bio-oils (40.31 – 42.08 MJ/kg) were higher than those of non-catalytic bio-oils (36.47 – 36.76 MJ/kg). Catalyst reduced the viscosity (at 400 and 500 oC), moisture content and CCR (at 400 and 600 oC), and increased the pH value of bio-oils (at 400 and 600 oC). Catalytic pyrolysis deoxygenates and enhances the fuel properties of bio-oils.

Au/Ag nanoparticles-decorated TiO2 with enhanced catalytic activity for nitroarenes reduction

A straightforward and environmentally-friendly approach for the fabrication of TiO2 supported nano-Au and Ag catalysts with enhanced activity in nitroarenes reduction is presented. The immobilization of the metal nanoparticles (NPs) onto TiO2 was performed through a first step of metal precursors adsorption (tetrachloroauric(III) acid trihydrate or silver(I) nitrate) onto TiO2, followed by a step of in situ metal cations reduction using three types of reducing agents: citric acid, NaBH4 and simulated sunlight irradiation. The type of reducing agent influenced the size, the oxidation state and loading of the grafted metal NPs. The Au-based nanocomposites contained Au NPs with sizes ranging between 19.3 and 28.2 nm and Au loadings in the range of 7.2–19.8 wt%. NaBH4 was the best reducing agent for the Au NPs immobilization onto TiO2, leading to the highest Au loading (19.8 wt%) and lowest Au+/Au0 ratio (0.07). In the case of the Ag-based materials, citric acid revealed to be the best reducing agent for the Ag NPs immobilization onto TiO2, leading to ultrasmall grafted NPs, 10.1 wt% Ag loading and the highest amount of metallic silver (Ag+/Ag0 ratio = 0.03).The catalytic performance of the Au/Ag-based TiO2 nanocomposites was evaluated in the reduction of 4-nitrophenol (4-NP) and 4-nitroaniline (4-NA) in aqueous medium, at room temperature, using NaBH4 as reducing agent (substrate:reducing agent:catalyst weight ratio = 0.007:1.89:1). The Au- and Ag-based nanocomposites (prepared with NaBH4 and citric acid, respectively) led to 100% conversion of 4-NP within 260 and 40 s, respectively, with rate constants (k) of 19.1 × 10−3 and 94.2 × 10−3 s−1 (pseudo-first-order kinetics), respectively, demonstrating the higher performance of the Ag-based catalyst. In contrast, in the case of the 4-NA reduction, the highest catalytic performance was achieved for the Au-based material, promoting the total substrate conversion within 90 s (k = 29.4 ×10−3 s−1), while for the Ag-based catalyst the total 4-NA conversion was achieved within 120 s (k = 16.6 ×10−3 and 27.5 ×10−3 s−1). Both catalysts were reused in nine consecutive cycles in both 4-NP and 4-NA reduction, with the Au-based material presenting higher stability, especially for 4-NA reduction, with only a small reaction time increment.

Catalytic and kinetic study of the liquid-phase oxidation of lactose over Au/Al2O3 nanostructured catalysts in a monolithic stirrer reactor

The liquid-phase oxidation of lactose (LA) to lactobionic acid (LB) was studied over Au(2 %)/Al2O3 nanostructured catalyst. Catalytic tests were carried out at 65 °C, varying O2 partial pressures in the range of 0.21−1 bar and LA initial concentrations between 0.007 and 0.089 M. In all of the cases, the selectivity to LB was always 100 %. It was observed that the trends for the LA conversion (XLA) with time depends on the ratio of catalyst weight to initial LA moles W/nLA0 and the initial LA concentration CLA0. Experimental data were interpreted by kinetic modelling applying pseudo-homogeneous and Langmuir-Hinshelwood-Hougen-Watson (LHHW) models. It was found that irreversible surface oxidation of LA rules the reaction rate when W/nLA0= 30 g mol−1. At the early stages, the reaction rates did not depend on the LA concentration, and thus the reaction order with respect to LA was zero. In this case, an LHHW model considering total coverage of the active sites gives a very good fitting of the experimental data. As LA was consumed, the progress of conversion with time is different for each case and the reaction order changes to positive. Now, a better fitting is obtained with an LHHW model in which partial coverage of the active sites is considered. When liquid phase was diluted in LA and W/nLA0= 95 g mol−1, the LA chemisorption becomes the controlling step. Therefore, the results obtained by kinetic modelling helped to explain the dependence of LA oxidation rate with CLA0 and W/nLA0.

Dehydration of Methanol in catalytic fixed bed reactor

Dimethyl ether (DME) considered as an important alternative fuel and hence, its production is vital. This study directed to choose suitable catalyst (with high selectivity, high energy conservation and low cost) in catalytic dehydration of methanol to produce DME in fixed bed reactor at gas phase. Three commercial catalysts were used (Alumina, Ziolite 5A and resin) and moderate range of temperature (90-120 0C). Weight ratio of catalyst to molar flow rate (W/FA) from 27 to 81 (gcat.hr/gmol) was selected. Both Alumina and ziolite showed weak activity at this range of temperature while resin was better. Conversion of methanol to dimethyl ether (DME) showed significant dependence on increasing temperature and flow rate (highest conversion was 8% at 120 0C and W/F=81 gcat. hr/gmol). Also, deactivation of resin with time was studied at optimum conditions and the results showed no effect of time on both conversion and selectivity to produce DME. DME production selectivity was 100% at all operation circumstances. In addition, the nature of active sites of resin was studied by using selectivity poison procedure. Accordingly, acidic sites were mainly concerned with the reaction whereas Bronsted acidity has mainly contributed to the acidic sites.

Hydrotreating of Sunan Candlenut Oil using NiMo/ɣ-Al2O3 Catalyst for Renewable Diesel Production

Catalytic hydrotreating process based on NiMo/ɣ-Al2O3 has been conducted in this study using Sunan candlenut oil as the feedstock, in order to obtain renewable diesel products as well as conventional diesel. Hydrotreating process was performed with the variation of several operating conditions including pressure, temperature and weight ratio of catalyst to vegetable oils. Products obtained were then analyzed using Gas Chromatography (GC) and tested to obtain physical and chemical properties. Based on GC results, it was showed that the increase in operating pressure and temperature also increase the yield of hydrocarbon products in the range of diesel, with the highest yield of 30.95% at a pressure of 60 bar and temperature of 400°C. The conversion and selectivity were 33.48% and 95.72%, respectively, where the reaction route tends to the decarbonylation mechanism. However, changes in the weight ratio of catalyst to the vegetable oil did not affect the overall product yield. Analysis of physical and chemical properties of the product prior to distillation showed a decrease in the value of density, viscosity, iodine numbers and acid numbers are quite significant and closer specification commercial diesel oil.

NiCu mixed metal oxide catalyst for alkaline hydrogen evolution in anion exchange membrane water electrolysis

We report on the optimization of nickel-copper catalysts for superior performance as a cathode catalyst in anion exchange membrane (AEM) water electrolysis. The bifunctional system of NiCu mixed metal oxide (MMO) nanosheets includes Ni metallic, NiO, and CuO oxides provide rapid kinetics for the hydrogen-evolution reaction (HER) of the Volmer step. In-situ Raman spectroscopy for NiCu MMO proved that nickel hydroxide was sustained under HER conditions for at least 30,000 s, which may explain why the exceptional activity of NiCu MMO as compared to other nickel-copper catalysts is maintained over time. The activity of the NiCu MMO for the HER activity in alkaline electrolytes increased as KOH concentration raised from 0.1 M to 1 M. The NiCu MMO nanosheets showed superior stability under alkaline HER conditions for 30 h. The use of Nafion ionomer in the ink resulted in a higher HER current density as compared to inks with a Fumion anion ionomer. The maximum HER performance was achieved at a Nafion ionomer to catalyst weight ratio of 0.5. Using Ir black as the anode, the NiCu MMO cathode gave an AEM electrolyzer performance of 1.85 A/cm2 at 2 V in 1 M KOH at 50 °C. The NiCu MMO catalyst developed here delivers AEM performance comparable to PEM water electrolysis.

Enhanced Surface Energetics of CNT-Grafted Carbon Fibers for Superior Electrical and Mechanical Properties in CFRPs.

Surface enhancement of components is vital for achieving superior properties in a composite system. In this study, carbon nanotubes (CNTs) were grown on carbon fiber (CF) substrates to improve the surface area and, in turn, increase the adhesion between epoxy-resin and CFs. Nickel (Ni) was used as the catalyst in CNT growth, and was coated on CF sheets via the electroplating method. Surface energetics of CNT-grown CFs and their work of adhesion with epoxy resin were measured. SEM and TEM were used to analyze the morphology of the samples. After the optimization of surface energetics by catalyst weight ratio (15 wt.% Ni), CF-reinforced plastic (CFRP) samples were prepared using the hand lay-up method. To validate the effect of chemical vapor deposition (CVD)-grown CNTs on CFRP properties, samples were also prepared where CNT powder was added to epoxy prior to reinforcement with Ni-coated CFs. CFRP specimens were tested to determine their electrical resistivity, flexural strength, and ductility index. The electrical resistivity of CNT-grown CFRP was found to be about 9 and 2.3 times lower than those of as-received CFRP and CNT-added Ni-CFRP, respectively. Flexural strength of CNT-grown Ni-CFRP was enhanced by 52.9% of that of as-received CFRP. Interestingly, the ductility index in CNT-grown Ni-CFRP was 40% lower than that of CNT-added Ni-CFRP. This was attributed to the tip-growth formation of CNTs and the breakage of Ni coating.

Ammonia decomposition over 3D-printed CeO2 structures loaded with Ni

Binder-free ceria pastes have been formulated and used to prepare ceria structures with a woodpile arrangement of microchannels through 3D printing. After loading them with nickel, these catalytic structures have been tested for ammonia decomposition to obtain hydrogen, and their performance has been compared with those of conventional Ni/CeO2 powder catalysts and with that of a conventional cordierite honeycomb washcoated with Ni/CeO2. Samples have been characterized by N2 physisorption, inductively coupled plasma optical emission spectrometry (ICP-OES), X-Ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy. At the same reaction temperature and flow rate to catalyst weight ratio (F/W), the 3D-printed ceria structures show a catalytic activity much higher than that of the cordierite honeycomb on a reactor volume basis. Additive manufacturing represents a valuable tool to prepare customized ceria-based catalytic structures for practical application with a variety of geometries not attainable with conventional methods.

Combined microwave assisted roasting and leaching to recover platinum group metals from spent automotive catalysts

A microwave assisted two-step platinum group metal (PGM) extraction process for spent automotive ceramic catalysts was developed. The first step consists of a microwave (MW) sulfation roasting process of spent catalyst in the presence of NaHSO4·H2O or KHSO4 and NaClO3, for which the roasting parameters (i.e. MW power, roasting time, ClO3−:HSO4− molar ratio, salt:catalyst weight ratio) were studied and optimized. During roasting a solid salt mixture and spent catalyst (weight ratio salt:spent catalyst = 5, molar ratio NaClO3:NaHSO4·H2O = 0.05) was volumetric heated (750 W, 30 min) through absorption of MWs without the use of any other heat source. Whereas for the subsequent step, a short (30 min, 105 °C) MW acidic leaching process in 1 M HCl solution at a liquid to salt ratio of 10 was evaluated to give the best PGM leachabilities (i.e. Pd 96 ± 1%, Pt 85 ± 5% and Rh > 96%). An in depth experimental study of the roasting process showed that sulfation roasting attacks both the cordierite (Mg2Al4Si5O18) honeycomb material and rare earth oxides of the wash coat, to form sulfate salts. During roasting metallic Pd oxidized. Mass loss during roasting was ascribed to evaporation of NaHSO4·H2O hydration water and subsequent decomposition of NaHSO4.

Synthesis and modification of mesoporous silica with sulfated titanium dioxide as a heterogeneous catalyst for biodiesel production from palm fatty acid distillate

This study synthesizes fatty acid ethyl ester (FAEE) through esterification reaction of palm fatty acid distillate (PFAD) using SO42−/TiO2 supported by mesoporous silica as a catalyst. The steps of this study were a synthesis of mesoporous silica, catalyst preparation by impregnation and catalyst activity test through esterification reaction of PFAD by using ethanol. The variables of study on the esterification reaction were the weight ratio of catalyst and PFAD as 3%, 5%, 7%. Based on BET characterization, it shows that synthesized silica material is mesoporous silica. The characterization result of silica and catalyst using X-Ray of wide-angle powder (WAXRD) and SEM gives information that the existence of silica as support of SO42−/TiO2 active site. At the catalyst activity test through esterification reaction, it was obtained the best weight ratio of catalyst and PFAD was 5% with the conversion of ethyl ether formation as 98.9 %. Analysis data and physical properties were viscosity at a temperature of 40 °C and density at the temperature of 15 °C, it shows that the value fit a biodiesel standard of ASTM, meanwhile analysis data of GC-MS toward product of ethyl ester and PFAD has shown that most of the fatty acid in PFAD had been converted into ethyl ester.

Polydopamine protected hollow nanosphere with AuAg-nanoframe-core@Carbon@AuAg-nanocrystals-satellite hybrid nanostructure (AuAg@C@AuAg/PDA) for enhancing nanocatalysis

This work reported a facile method for fabricating multi-layered polydopamine (PDA) encapsulated AuAg@C@AuAg core/shell nanosphere with a hollow interior. During the synthetic process, the preliminary Ag@C nanosphere is easily covered by an AuAg/PDA hybrid layer through the in situ redox-oxidized polymerization to form the Ag-AuAg@C@AuAg/PDA precursor, in which the AuAg bimetallic nanocrystals are simultaneously obtained via the electrochemical substitution reaction. After etching the residue Ag core, the final AuAg@C@AuAg/PDA hybrid nanosphere is achieved and the inner AuAg shows a unique nanoframe-like nanostructure. The carbon shell plays an important role for the formation and structure evolution of the AuAg@C@AuAg/PDA, and the composition can be modulated by varying the polymerization process. Owing to the well distributed AuAg nanocrystals and inner AuAg nanoframes, the AuAg@C@AuAg/PDA shows better performance than Ag-AuAg@C@AuAg/PDA precursor in catalyzing 4-nitrophenol, and the rate constant (K) to catalyst weight ratio reaches as high as 3.63 min−1 •mg-1. As a result, this work not only offers a hybrid bi-metallic nanocatalyst with excellent performance, but also has valuable implications for compositional modulation of hollow interior multi-layered nanostructure in adsorption, drug delivery, and nanocatalysis.

The kinetics of enargite dissolution in chloride media in the presence of activated carbon and AF 5 catalysts

This paper pertains to the kinetics study of atmospheric dissolution of enargite in chloride media with and without the addition of two different catalysts: (1) granular coconut shell based activated carbon (AC), and (2) a novel carbon-based catalyst with the commercial name of AF 5 Lanxess Lewatit® (AF 5). Unlike AC or other catalysts, AF 5 is capable of collecting solid sulphur particles on its surface during the atmospheric leaching process, leaving behind insignificant elemental sulphur in the oxidative leaching residues.The addition of both AC and AF 5 considerably enhance the leaching efficiency. Only 70% of copper was recovered in 96 h at 90 °C without the catalyst addition. The copper recovery was increased to 92% and 96% in the presence of AC and AF 5 respectively, in the concentrate to catalyst weight ratio of 1:1. The Cu2+ ions are found to be the main oxidant in the enargite leaching procedure. It was shown that the diffusion of Cu2+ ions through the product layer on the partially-leached enargite particles is the controlling step of the leach process, and the addition of the AC and AF 5 catalysts did not change the process controlling mechanism. The shrinking core model (SCM) has been used as the general kinetic model to study the enargite leaching kinetics at different temperatures. Scanning electron microscopy images of the partially-leached minerals confirmed that no impermeable elemental sulphur layer was formed on the enargite surface.

Activity of Fly Ash-Derived ZSM-5 and Zeolite X on Fast Pyrolysis of Millettia (Pongamia) Pinnata Waste

Fly ash (FA), a by-product of coal combustion, is considered as waste due to its high content of lime and other impurities and is either disposed of in landfills or recycled. Utilization of waste FA as a starting material for the synthesis of zeolite catalysts is a promising solution to reuse this waste. Meanwhile, de-oiled Millettia (Pongamia) pinnata seed waste (PPW) is produced in large amounts from the bio-oil extraction process. This waste is of no value due to its toxicity. However, it was previously shown that the fast pyrolysis of PPW to produce biofuels resulted in oleic acid and other oxygenated (O)-compounds as the main composition (67.2%) with smaller levels of hydrocarbons (HCs). In this work, the catalytic upgrading fast pyrolysis of PPW over the FA-derived ZSM-5 (FA-ZSM-5) and zeolite X (FA-X) catalysts to enhance the formation of HCs was performed using a pyrolyzer interfaced with gas chromatography-mass spectrometry (Py-GCMS), using various biomass to catalyst (B:C) weight ratios (1:1, 1:5 and 1:10). The FA-ZSM-5 and FA-X were derived from FA by alkali hydrothermal and alkali fusion methods, respectively. The result demonstrated that the pyrolysis vapors of PPW had a high content of undesirable components, such as carboxylic acids, oleic acid and other O-compounds (67.2%), whereas the aliphatic and aromatic HC contents were markedly lower. The presence of the synthesized FA-ZSM-5 or FA-X catalysts resulted in a major improvement in the pyrolysis vapor quality. Selectivity on total HCs (aliphatic and aromatic) was significantly increased with greater catalyst contents for both FA-ZSM-5 (90.6%) and FA-X (84.9%). FA-ZSM-5 exhibited a high selectivity for aromatic HCs (82.6%) while zeolite-X showed a higher selectivity towards aliphatic HCs (71.0%). The level of O-compounds was substantially decreased to 1.12% and 21.9% with FA-ZSM-5 at a B:C ratio of 1:10 and FA-X at a B:C ratio of 1:5, respectively. In addition, FA-ZSM-5 and FA-X reduced the content of nitrogenated-compounds from 24.8% (no catalyst) to 8.3% and 0.0%, respectively. Overall, the results suggest that FA-ZSM-5 had a higher HC selectivity and was more effective in promoting deoxygenation reactions, whereas FA-X significantly enhanced the denitrogenation reaction.

Thermo-kinetics and product analysis of the catalytic pyrolysis of Pongamia residual cake

Catalytic fast pyrolysis of Pongamia residual cake (PRC) and the kinetics of this were evaluated using thermogravimetry and pyrolysis-gas chromatography/mass spectrometry analyses. The influence of the heating rate on the devolatilization process was studied to obtain corresponding kinetic information. Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) model-free isoconversion methods were used to predict the kinetic parameters. The major thermal degradation of PRC occurred around 150–550 °C with an activation energy of 97.2–394.3 kJ/mol or 114.5–412.2 kJ/mol as determined by the KAS and FWO methods, respectively. Micro-scale pyrolysis trials were performed to determine the effects of the PRC particle size, reaction temperature and PRC: catalyst weight ratio on the pyrolytic product distribution and upgraded pyrolytic vapor properties for the 5 wt% Ni impregnated on activated carbon (AC), aluminium(III) oxide (Al2O3), kaolin and zeolite NaA supports. The results indicated that using a 1:5 PRC: Ni/AC catalyst weight ratio with medium-sized PRC particles (125–425 μm) was the most effective condition for the conversion of oxygenated (O)-compounds to hydrocarbons (HCs) through decarbonylation, decarboxylation and dehydration reactions, giving the highest decrease (99%) in O-compounds. Increased HC yields, to more than 58%, were also obtained with this catalyst. Similarly, using the other synthesized Ni catalysts resulted in a reduction in the O-compounds and production of favorable HC species, albeit to a lesser extent. Therefore, the catalytic pyrolysis process of this residue, especially with a Ni/AC catalyst, has the potential to be a viable option for producing upgraded pyrolysis oil, which may be applied as a quality alternative biofuel.