Scholarly Articles

Solid Acid Catalyst Based on Single-Layer α-Zirconium Phosphate Nanosheets for Biodiesel Production via Esterification

In this study, a solid acid was prepared by the sulfonation of surface modified α-zirconium phosphate (ZrP) single-layer nanosheets (SO3H@ZrP), and the prepared solid acid was investigated for the esterification of oleic acid with methanol to produce biodiesel. For comparison, liquid H2SO4 and commercial Amberlyst® 15 catalyst were also evaluated for the same reaction under the same conditions. The experimental results showed that the SO3H@ZrP solid acid catalyst has a superior catalytic efficiency for the esterification reaction, as well as excellent recyclability. The SO3H@ZrP single-layer solid acid catalyst can be uniformly dispersed in the reaction media, but remains heterogeneous and thus can be easily separated and recycled.

Jatropha curcas L. oil extracted by switchable solvent N, N- dimethylcyclohexylamine for Biodiesel Production

Biodiesel, which is a renewable and environmentally friendly fuel, has been studied widely to help remedy increasing environmental problems. One of the key processes of biodiesel production is oil extraction from oilseed materials. Switchable solvents can reversibly change from molecular to ionic solvents under atmospheric CO2, and can be used for oil extraction. N, N-dimethylcyclohexylamine (DMCHA), a switchable solvent, was used to extract oil from Jatropha curcas L. oil seeds to produce biodiesel. The appropriate extraction conditions were: 1:2 ratio of seed mass to DMCHA volume, 0.3-1mm particle size, 200 rpm agitation speed, 60min extraction time, and 30 °C extraction temperature. The extraction ratio was about 83%. This solvent extracted the oil more efficiently than hexane, and is much less volatile. By bubbling CO2 under 1atm and 25 °C for 5h, the oil was separated, and DMCHA was recovered after releasing CO2 by bubbling N2 under 1atm and 60 °C for 2h. The residual solvent content in oil was about 1.7%. Selectivity of DMCHA was evaluated by detecting the protein and sugar content in oil. Using the oil with residual solvent to conduct transesterification process, the oil conversion ratio was approximately 99.5%.

Inter-solubility of product systems in biodiesel production from Jatropha curcas L. oil with the switchable solvent DBU/methanol

The switchable solvent 1,8-diazabicyclo-[5.4.0]-undec-7-ene (DBU)/methanol can be used in transesterification with oil to produce biodiesel (fatty acid methyl ester). The reactants (methanol, oil and catalyst DBU) and the products (fatty acid methyl ester and glycerol) are partially soluble in the production process. The phase equilibrium of the product components is essential data for biodiesel separation and process operation. In this work, the effects of catalyst dosage and temperature were studied on the phase equilibrium of the product systems. The phase composition of the product systems and the distribution of components were measured. The results showed the distribution of methanol, DBU and glycerol in the biodiesel-rich phase increases with the increase of DBU dosage from 1 wt% of oil to 15 wt% of oil and temperature from 298.1 K  0.1 K to 333.1 K  0.1 K, and decreases accordingly in the glycerol-rich phase. The distribution of biodiesel in both phases varies little. Increasing the dosage of DBU and/or temperature enhances the distribution and solubility of methanol, DBU and glycerol in the biodiesel-rich phase. This phenomenon was explained by estimating and analyzing van der Waals forces and hydrogen bonds.

Catalyzed production of biodiesel and bio-chemicals from brown grease using Ionic Liquid functionalized ordered mesoporous polymer

Brown grease is a common waste product responsible for many sewer overflows and illnesses, and it contains useful free fatty acids and other hydrocarbon-like molecules. This work demonstrates the potential to transform nearly 100% of the brown grease into biodiesel, synthesis gas and bio-oil for use as biofuel or
for power generation. A solid acid catalyst was synthesized with excellent activity for esterification of the free fatty acids and relatively high activity for transesterification of triglycerides, which make up the oil phase of the brown grease. The catalyst is synthesized using a tri-block copolymer template that leads to
mesopores with diameters narrowly centered at 11.1 nm. Residual solids, which make up roughly 10% of the brown grease, were found by elemental analysis to be a hydrogen rich feedstock, with H/Ceff ratio greater than wood or sugar. Preliminary gasification and pyrolysis experiments illustrate nearly 100%
conversion of the residual solids. Fast pyrolysis in a drop tube furnace at 600 C produced oil consisting predominantly of long chain hydrocarbons.

Transesterification Catalyzed by Superhydrophobic–Oleophilic Mesoporous Polymeric Solid Acids: An Efficient Route for Production of Biodiesel

We report here an efficient mesoporous polymeric solid acid catalyst (p-PDVB-SO3H) with superhydrophobic– oleophilic properties synthesized from copolymerization of divinylbenzene (DVB) with sodium p-styrene sulfonate under solvothermal conditions. N2 isotherm showed that p-PDVBSO3H has large BET surface area and uniform mesopore. Contact angle tests showed that p-PDVB-SO3H exhibits superhydrophobic–oleophilic property for triolein and methanol, which results in its good miscibility and high exposition degree of active sites for various organic reactants. Catalytic tests showed that p-PDVB-SO3H has much better catalytic activities and recyclability toward transesterification to biodiesel than those of H-form mesoporous ZMS-5 zeolite, carbon solid acid and commercially acidic resin of Amberlyst 15, which will be very important for its wide applications for biodiesel production in industry.

The interplay of phase equilibria and chemical kinetics in a liquid/liquid multiphase biodiesel reactor

A countercurrent liquid/liquid phase biodiesel reactor achieved 99% triglyceride to methyl ester conversion at the same time as separating 90% of the produced glycerin. However, a low inverse sensitivity of the conversion to the glycerin separation efficiency led to biodiesel that did not meet ASTM quality standards in previous work. A distributed methanol injection strategy is demonstrated herein to improve reactor performance, yielding ASTM quality biodiesel and 90% separation efficiencies. Preliminary data on feed rate changes yields counterintuitive results where conversion increases as feed rate increases. A model that assumes equilibrium between the reacting oil phase and the settling glycerol phase simulates the experimental results and provides insight into the reactor behavior.

Continuous production of biodiesel from waste cooking oil in a reactive distillation column catalyzed by solid heteropolyacid: Optimization using response surface methodology (RSM)

This study aims to develop an optimal continuous process to produce fatty acid methyl esters (biodiesel) from waste cooking oil in a reactive distillation column catalyzed by a heteropolyacid, H3PW12O40!6H2O. The conventional production of biodiesel in the batch reactor has some disadvantage such as excessive
alcohol demand, short catalyst life and high production cost. Reactive distillation combines reaction and separation to simplify the process operation. The reaction catalyzed by H3PW12O40!6H2O overcomes the neutralization problem that occurs in conventional transesterification of waste cooking oil with high
free fatty acid (FFAs) and water content. Response surface methodology (RSM) based on central composite design (CCD) was used to design the experiment and analyzed four operating parameters: total feed flow, feed temperature, reboiler duty and methanol/oil ratio. The optimum conditions were determined
to be 116.23 (mol/h) total feed flow, 29.9 !C feed temperature, 1.3 kW reboiler duty, and 67.9 methanol/ oil ratio. The optimum and actual free fatty acid methyl ester (FAME) yield was 93.98% and 93.94%, respectively, which demonstrates that RSM is an accurate method for the current procedure.

Bioenergy production from glycerol in hydrogen producing bioreactors (HPBs) and microbial fuel cells (MFCs)

The supply of glycerol has increased substantially in recent years as a by-product of biodiesel production. To explore the value of glycerol for further application, the conversion of glycerol to bioenergy (hydrogen and electricity) was investigated using Hydrogen Producing Bioreactors (HPBs) and Microbial Fuel Cells (MFCs). Pure-glycerol and the glycerol from biodiesel waste stream were compared as the substrates for bioenergy production. In terms of hydrogen
production, the yields of hydrogen and 1,3-propanediol at a pure-glycerol concentration of 3 g/L were 0.20 mol/mol glycerol and 0.46 mol/glycerol, respectively. With glucose as the cometabolism substrate at the ratio of 3:1 (glycerol:glucose), the yields of hydrogen and 1,3-propanediol from glycerol significantly increased to 0.37 mol/mol glycerol and 0.65 mol/ glycerol, respectively. The glycerol from biodiesel waste stream had good hydrogen yields
(0.17e0.18 mol H2/mole glycerol), which was comparable with the pure-glycerol. In terms of power generation in MFCs, pure-glycerol was examined at concentrations of 0.5e5 g/L with the highest power density of 4579 mW/m3 obtained at a concentration of 2 g/L. The power densities from the biodiesel waste glycerol were 1614e2324 mW/m3, which were likely caused by the adverse effects of impurities on electrode materials. An economic analysis indicates
that with the annual waste stream of 70 million gallons of glycerol, the expected values generated from HPBs and MFCs were $311 and $98 million, respectively.

Investigation into the relationship between the gravity vector and the flow vector to improve performance in two-phase continuous flow biodiesel reactor

The following study analyzes the performance of a continuous flow biodiesel reactor/separator. The reactor achieves high conversion of vegetable oil triglycerides to biodiesel while simultaneously separating co-product glycerol. The influence of the flow direction, relative to the gravity vector, on the reactor performance was measured. Reactor performance was assessed by both the conversion of vegetable oil triglycerides to biodiesel and the separation efficiency of removing the co-product glycerol. At slightly elevated temperatures of 40-50 C, an overall feed of 1.2 L/min, a 6:1 M ratio of methanol to vegetable oil triglycerides, and a 1–1.3 wt.% potassium hydroxide catalyst loading, the reactor converted more than 96% of the pretreated waste vegetable oil to biodiesel. The reactor also separated 36–95% of the glycerol that was produced. Tilting the reactor away from the vertical direction produced a large increase in glycerol separation efficiency and only a small decrease in conversion. 2010

The feasibility of converting Cannabis sativa L. oil into biodiesel

Cannabis sativa Linn, known as industrial hemp, was utilized for biodiesel production in this study. Oil from hemp seed was converted to biodiesel through base-catalyzed transesterification. The conversion is greater than 99.5% while the product yield is 97%. Several ASTM tests for biodiesel quality were implemented on the biodiesel product, including acid number, sulfur content, flash point, kinematic viscosity, and free and total glycerin content. In addition, the biodiesel has a low cloud point (!5 !C) and kinematic viscosity (3.48 mm2 /s). This may be attributed to the high content of poly-unsaturated fatty acid of hemp seed oil and its unique 3:1 ratio of linoleic to a-linolenic acid.

Demonstration of a Liquid-Tin Anode Solid-Oxide Fuel Cell (LTA-SOFC) Operating from Biodiesel Fuel

In this paper, the authors present the first demonstration of a liquid-tin anode solid-oxide fuel cell (LTASOFC) operating on pure biodiesel (B100) prepared via base-catalyzed transesterification of virgin and waste cooking oils. The LTA-SOFC was able to convert the biodiesel to electricity at commercially viable
power densities, i.e., greater than 100 mW cm-2 . The peak power for each cell was 3.5 W over an active area of 30 cm-2, which translates to a power density of 117 mW cm-2 and current density of 217 mA cm-2. The peak power densities correspond to ∼80% fuel use at the liquid-tin anode surface and overall cell efficiencies of >40%. These findings demonstrate the flexibility in operating a solid-oxide fuel cell capable of internal reforming from a blend of petroleum- and biomass-derived diesels for greater resource flexibility. Cells were operated for short times (∼4.5 h), owing to the experimental nature of the balance
of plant. Results support future efforts in developing an efficient balance-of-plant system for demonstrating long-term (>1000 h) power generation from biodiesel using the LTA-SOFC design.

Pilot Scale Two-phase Continuous Flow Biodiesel Production via Novel Laminar Flow Reactor-Separator

The following study presents the first quantitative performance data for a novel laminar flow biodiesel reactor/ separator. The reactor ideally achieves high conversion of vegetable oil triglycerides to biodiesel while simultaneously allowing glycerol to phase separate and settle from the reacting flow. The reactor was operated using pretreated waste canola oil as a feedstock; potassium hydroxide dissolved in methanol was used as a catalyst. Reactor performance was assessed by computing conversion of vegetable oil triglycerides to biodiesel as well as subsequent separation of the coproduct glycerol stream. At slightly elevated temperatures (40-50 °C), an overall feed of 1.2 L/min, a 6:1 molar ratio of methanol to vegetable oil triglycerides, and a 1.3 weight% catalyst loading, the reactor was able to achieve greater than 99% conversion of pretreated waste canola oil to biodiesel and remove 70-99% of glycerol produced.

Variables affecting homogeneous acid catalyst recoverability and reuse after esterification of concentrated omega-9 polyunsaturated fatty acids in vegetable oil triglycerides

Global concerns regarding greenhouse gas emissions combined with soaring oil prices have driven the search for renewable diesel fuels derived from either virgin or waste vegetable oils, dubbed “bio-diesels”. A key challenge in the emerging bio-diesel industry is cost-effective pre-treatment of
waste vegetable oils to reduce free-fatty acid content prior to transesterification. This article reports, for the first time, recoverability and reusability of hydrochloric and sulfuric acid catalysts for efficient pre-treatment of waste cooking oils for subsequent conversion to bio-diesels. Esterification of omega-9 polyunsaturated fatty acids, particularly 18:2,18:3 linoleic acid with methanol and a homogenous acid catalyst was investigated over a range of fatty acid concentrations. It was determined that greater than 95% by weight of each catalyst was recovered after esterification under all conditions investigated. When recovered methanol was used, containing recovered catalyst and water, it was determined that hydrochloric acid catalyzed esterification exhibits a higher tolerance to water accumulation. After sulfuric acid was recovered and re-used, the observed rate constant decreased more than 50% to a value comparable to that observed for hydrochloric acid at more than three times the water concentration.