In the present work, bifunctional heterogeneous catalysts were studied to develop an effective catalyst for biodiesel production from waste cooking oil with improved catalytic activity and stability. ...The catalysts were characterized by various analytical techniques to explore their physicochemical properties. The catalytic activity was evaluated in the transesterification of waste cooking oil for low cost biodiesel production. The bifunctional heterogeneous catalysts show improved transesterification activities. Among the different catalysts tested, the Mo–Mn/γ-Al2O3-15 wt% MgO catalyst provides the maximum biodiesel yield of 91.4% in reaction time of 4 h at reaction temperature of 100 °C, methanol to oil molar ratio of 27:1 and an agitation speed of 500 rpm. Moreover, the bifunctional heterogeneous catalyst shows substantial chemical stability and could be reused for at least eight times without major loss in its catalytic activity. The physicochemical properties of the biodiesel produced from waste cooking oil were further studied and compared with the ASTM and the EN biodiesel specifications. The results show that the properties of the biodiesel produced comply with the international standard specifications.
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•Synthesis of bifunctional heterogeneous catalysts by modified impregnation method.•Study of physicochemical properties of synthesized catalysts by analytical techniques.•An economical biodiesel production from waste cooking oil.•Optimization of important reaction parameters for biodiesel production.•Study of physicochemical properties of synthesized biodiesel.
Limited solubility of alcohols in vegetable oils hinders transesterification reaction process. Phase transfer catalysis can be of great advantage to enhance the reaction rates. Addition of ...cetyltrimethylammonium bromide as a phase transfer catalyst on in situ transesterification of
Jatropha curcas L. with alkaline ethanol was investigated. Use of cetyltrimethylammonium bromide increased the yield of fatty acid ethyl esters. Optimum operating conditions were experimentally established. Yield of fatty acid ethyl esters increased from 89.2 wt% to 99.5 wt% with reduced requirement of ethanol by 16.7 v%, sodium hydroxide catalyst by 33.3 wt%, at a lower temperature of 30 °C and reduced mixing speed in shorter reaction time. The quality of fatty acid ethyl esters fuel conforms to the standards of ASTM D6751 and EN-14214.
► Cetyltrimethylammonium bromide increases yield of fatty acid ethyl esters. ► Cetyltrimethylammonium bromide reduced the consumption of NaOH and ethanol. ► Cetyltrimethylammonium bromide lowers reaction time, temperature and mixing speed. ► Reaction Mechanism of Cetyltrimethylammonium bromide catalyzed reaction is developed.
Particles in gas–solid flows aggregate to move as “clusters” and simultaneously develop gas “voids” free of particles. A model for gas–solid flow in risers considering the presence of clusters and ...voids is presented. Equations are developed to estimate the size of clusters considering “ratio of cluster volume to void volume to be equal to the ratio of cluster volumetric fraction to void volumetric fraction in the bed”. Estimates of cluster size compare well with the experimental observations reported in the literature. Equations developed for slip ratios and gas to particle effective drag coefficients are inline with the trends reported in the literature.
Particles in gas–solid flows aggregate to move as “clusters” and simultaneously develop gas “voids” free of particles. A model for gas–solid flow in risers considering the presence of clusters and voids is presented. Equations developed to estimate the size of clusters, slip ratios and gas to particle effective drag coefficients compare well with the experimental trends reported in the literature.
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This paper presents the synthesis and characterization of monometallic and bimetallic cobalt and iron nanoparticles supported on alumina. The catalysts were prepared by a wet impregnation method. ...Samples were characterized using temperature-programmed reduction (TPR), temperature-programmed oxidation (TPO), CO-chemisorption, transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM-EDX) and N
2
-adsorption analysis. Fischer-Tropsch synthesis (FTS) was carried out in a fixed-bed microreactor at 543 K and 1 atm, with H
2
/CO = 2 v/v and space velocity, SV = 12L/g.h. The physicochemical properties and the FTS activity of the bimetallic catalysts were analyzed and compared with those of monometallic cobalt and iron catalysts at similar operating conditions.
H
2
-TPR analysis of cobalt catalyst indicated three temperature regions at 506°C (low), 650°C (medium) and 731°C (high). The incorporation of iron up to 30% into cobalt catalysts increased the reduction, CO chemisorption and number of cobalt active sites of the catalyst while an opposite trend was observed for the iron-riched bimetallic catalysts. The CO conversion was 6.3% and 4.6%, over the monometallic cobalt and iron catalysts, respectively. Bimetallic catalysts enhanced the CO conversion. Amongst the catalysts studied, bimetallic catalyst with the composition of 70Co30Fe showed the highest CO conversion (8.1%) while exhibiting the same product selectivity as that of monometallic Co catalyst. Monometallic iron catalyst showed the lowest selectivity for C
5+
hydrocarbons (1.6%).
Limited information is available about the thermodynamic evaluation for biomass gasification process using updraft gasifier. Therefore, to minimize errors, the gasification of dry refinery sludge ...(DRS) is carried out in adiabatic system at atmospheric pressure under ambient air conditions. The objectives of this paper are to investigate the physical and chemical energy and exergy of product gas at different equivalent ratios (ER). It will also be used to determine whether the cold gas, exergy, and energy efficiencies of gases may be maximized by using secondary air injected to gasification zone under various ratios (0, 0.5, 1, and 1.5) at optimum ER of 0.195. From the results obtained, it is indicated that the chemical energy and exergy of producer gas are magnified by 5 and 10 times higher than their corresponding physical values, respectively. The cold gas, energy, and exergy efficiencies of DRS gasification are in the ranges of 22.9–55.5%, 43.7–72.4%, and 42.5–50.4%, respectively. Initially, all 3 efficiencies increase until they reach a maximum at the optimum ER of 0.195; thereafter, they decline with further increase in ER values. The injection of secondary air to gasification zone is also found to increase the cold gas, energy, and exergy efficiencies. A ratio of secondary air to primary air of 0.5 is found to be the optimum ratio for all 3 efficiencies to reach the maximum values.
Strong Electrostatic Adsorption (SEA) is an effective method to synthesize and introduce Cobalt nanoparticles on Carbon Nanotubes (CNTs) support. Point of zero charge (PZC) of CNTs and optimum pH, ...the cobalt uptake versus different pH were investigated. By using the range of characterization methods such as TEM, FESEM and TPR catalyst prepared was studied. TEM and FESEM images indicate well-dispersed cobalt particles on the CNTs support. TPR was proven reduction peak at high temperature (530oC) indicating strong interaction between Cobalt and CNTs support. SEA showed the desired method in preparing supported cobalt catalysts.
In this study, CNTs samples were prepared by refluxing CNTs in nitric acid for 16 h at 110 °C and then followed by thermal treatment. The Co catalyst was synthesized by the strong electrostatic ...adsorption (SEA) method on the treated CNTs support. The Co/CNTs samples were then calcined at temperatures of 300, 350, 400, 450 °C. Samples were characterized by TEM and N2 adsorption. The size of cobalt nanoparticles and the textural properties were influenced by the calcination temperature. The TEM results showed that cobalt nanoparticles were well dispersed on the treated CNTs support.
Fischer-Tropsch （FT） reaction involves conversion of syngas （a mixture of carbon monoxide and hydrogen） into higher hydrocarbons in the presence of an active catalyst. The syngas can be derived from ...non-petroleum feedstocks such as coal, biomass and natural gas, thus the FT reaction provides an alternative route for production of clean fuels. The FT process has received growing interest in recent years due to uncertainty in the Middle East, fast depletion of fossil fuel and environmental concern. This paper reports the synthesis, physicochemical properties and catalytic performance of cobalt-based catalyst in the FT reaction. The catalysts comprised metal nanoparticles supported on carbon nanotubes （CNTs） which were synthesized via a wet impregnation method. The catalysts were characterized using transmission electron microscopy （TEM）, temperature-programmed reduction/desorption （TPR/TPD） and X-ray photoelectron spectroscopy （XPS）. The performance of the cobalt-based catalyts in a FT reaction was evaluated in a fixed bed microreactor equipped with an on-line gas chromatograph for analyses of hydrocarbon products. The catalysts investigated in this work were Co/CNTs, 70Co30Mn/CNTs, 0.06%K/70Co30Fe/CNTs and 0.04%Nb/70Co30Fe/CNTs. TEM analyses revealed that the average sizes of the metal nanoparticles were 4-5 nm. Based on TPD analyses, the dispersion of these nanoparticles on CNTs were greater than 90%. The presence of both Co2＋ and Co3＋ ions were confirmed by XPS analysis. The 0.04% Nb/70Co30Fe/CNTs catalyst performed better than other catalysts in the FT reaction where it resulted in CO conversion of 35% and 16% C5＋ selectivity at pressure of 1 bar, 220 ~C and H2：CO of 2：1. Using the same catalyst, the CO conversion and C5＋ selectivity increased to 60% and 57%, respectively when the pressure was increased to 20 bar.
A series of novel carbon nanofibers (CNFs) supported bimetallic copper/zirconia catalysts are synthesized by deposition precipitation method and calcined at different temperatures. Calcined catalysts ...are characterized by various techniques like X-ray diffraction, N sub(2) adsorption-desorption, N sub(2)O chemisorption, high resolution transmission electron microscopy, temperature programmed reduction, X-ray photo-electron spectroscopy and temperature programmed desorption (CO sub(2) & NH sub(3)). The structure-activity correlation is discussed in details. The results demonstrate 450 degreesC as optimum calcination temperature for methanol synthesis rate with CO sub(2)/H sub(2) feed volume ratio of 1:3. CO sub(2) conversion is found to be directly proportional to copper metallic surface area (S sub(Cu)), while a linear relationship is observed between methanol synthesis rate and fraction of dispersed Cu.
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