Homogeneous Alkali Catalysts Research Articles

RSM optimization and kinetics study of α-Fe2O3/g-C3N4@H photocatalyst with S-type heterojunction for esterifying crude castor oil to reduce acidity and synthesize biodiesel

The preparation of biodiesel from low-quality oil conforms to the concept of sustainable development. In this study, low-quality castor oil was used as raw material, and α-Fe2O3/g-C3N4@halloysite photocatalyst prepared by two-step calcination method was used to pre-esterify the raw material to reduce the acid value, so that the quality of the raw material met the requirements of a homogeneous alkali catalyst, and then biodiesel was prepared by transesterification catalyzed by NaOH. The results show that the doped g-C3N4 has a larger specific surface area and better photoelectric properties, and the photocatalyst loaded with 10 wt% α-Fe2O3 has stronger light absorption characteristics and electron-hole separation ability. Response surface method was used to optimize the experiment: the molar ratio of ethanol to oil was 11.74:1, the amount of catalyst was 3.44 wt%, and the reaction time was 2.72 h. The reaction temperature was 74.57 ℃, and the conversion rate of FFAs (free fatty acids) was 97.62 %. The catalyst was recycled 5 times, and the conversion rate of FFAs still exceeded 80 %. The photocatalytic esterification reaction in this study conformed to the reversible second-order kinetic model. The physicochemical properties of castor oil-based biodiesel prepared by adding additives or preparing B20 biodiesel meet ASTM D6751 and EN 14214 standards.

Bio-Crude Production Improvement during Hydrothermal Liquefaction of Biopulp by Simultaneous Application of Alkali Catalysts and Aqueous Phase Recirculation

This study focuses on the valorization of the organic fraction of municipal solid waste (biopulp) by hydrothermal liquefaction. Thereby, homogeneous alkali catalysts (KOH, NaOH, K2CO3, and Na2CO3) and a residual aqueous phase recirculation methodology were mutually employed to enhance the bio-crude yield and energy efficiency of a sub-critical hydrothermal conversion (350 °C, 15–20 Mpa, 15 min). Interestingly, single recirculation of the concentrated aqueous phase positively increased the bio-crude yield in all cases, while the higher heating value (HHV) of the bio-crudes slightly dropped. Compared to the non-catalytic experiment, K2CO3 and Na2CO3 effectively increased the bio-crude yield by 14 and 7.3%, respectively. However, KOH and NaOH showed a negative variation in the bio-crude yield. The highest bio-crude yield (37.5 wt.%) and energy recovery (ER) (59.4%) were achieved when K2CO3 and concentrated aqueous phase recirculation were simultaneously applied to the process. The inorganics distribution results obtained by ICP reveal the tendency of the alkali elements to settle into the aqueous phase, which, if recovered, can potentially boost the circularity of the HTL process. Therefore, wise selection of the alkali catalyst along with aqueous phase recirculation assists hydrothermal liquefaction in green biofuel production and environmentally friendly valorization of biopulp.

Recent Advances of Biodiesel Production Using Ionic Liquids Supported on Nanoporous Materials as Catalysts: A Review

For the last two decades, the biodiesel attracted increasing attention as a promising biofuel to replace fossil diesel. However, the non-recyclability of homogeneous alkali catalysts and waste generation due to subsequent water washing remained as one of the major drawbacks of the biodiesel production process in the industry. Ionic liquids are one of the best alternatives to replace alkali catalysts owing to their unique properties such as non-volatility, excellent solubility for various organic and inorganic materials, structure tunability, environment-friendliness, and wide liquid temperature. However, high viscosity and difficult recovery have limited their application. Recently, heterogenization of ionic liquids on solid supports has been proposed to circumvent these issues. Among these solids, nanoporous materials have shown great potential in providing stable supports with high porosity and specific surface area. This paper reviews the recent developments in designing ionic liquids deposited on nanoporous materials as catalysts for biodiesel production. The emphasis was on the application of this type of catalysts for the optimization of reaction conditions. Moreover, challenges and opportunities for improving the overall production process in the presence of these catalysts were discussed. Despite that high biodiesel yields were obtained over many of nanoporous material-supported ionic liquids, their significantly higher cost compared to the conventional catalysts remained a major challenge. This issue can be overcome by employing less expensive cations and anions, increasing the loading amount of ionic liquids, and improving catalyst reusability in future studies.

Catalyst Activity of Solid Acid Catalyst Derived From Agricultural Biomass for Biodiesel Production From Waste Cooking Oil

Homogeneous alkali catalyst produces soap as a by-product and generates a large amount of wastewater. This study investigates the potential of three types of biomass namely oil palm frond, coconut shell and groundnut shell to be developed as a solid acid catalyst for transesterification of waste cooking oil into biodiesel. The synthesis of solid acid catalyst is conducted by incomplete carbonization of biomass followed by sulfonation using concentrated sulfuric acid to incorporate the sulfonic group in the carbon body. The porosity of prepared catalyst was characterized by adsorption/desorption technique and surface acidity was evaluated by means of back titration method. Coconut shell showed the highest acid density of 0.51 mmol/g followed by groundnut shell and oil palm frond with 0.16 mmol/g and 0.12 mmol/g respectively. The biodiesel production was carried out at reaction conditions of methanol-to-oil ratio 20:1, reaction temperature 60 ºC, reaction time 6 h and catalyst loading 6 wt%. The highest biodiesel conversion was achieved using a coconut shell as a catalyst with 86.5%, followed by groundnut shell and oil palm frond. The use of solid acid catalyst derived from biomass could explores new market value for waste material while minimizing the solid waste production and further reduces cost and energy consumption in biodiesel production.

Application of magnetic alumina-ferric oxide nanocatalyst supported by KOH for in-situ transesterification of microalgae cultivated in wastewater medium

Nowadays, use of microalgae as a cheap feedstock and heterogeneous catalysts for biodiesel production has gained considerable interest as they mitigate environmental problems induced by the conventional process of biodiesel production using homogeneous alkali catalysts. However, separation of heterogeneous catalysts from tissues and carcass of microalgae is an important task. For this reason, a magnetic Fe2O3–Al2O3 nanocatalyst promoted by potassium groups was synthesized using a modified impregnation method and was profoundly studied and compared with nanocatalysts without ferric oxide using X-ray diffraction, Fourier-transform infrared, Brunauer-Emmett-Teller and Barrett-Joyner-Halenda, scanning electron microscopy, transmission electron microscopy and energy-dispersive spectroscopy analyses. The results revealed that the magnetic nanocatalyst with a core-shell structure had suitable surface area, pore size, and particle size and also had no impurity on its structure. The nanocatalyst was used for biodiesel production from microalgae cultivated in a wastewater medium via in-situ transesterification reaction. The nanocatalyst converted 95.6% of microalgae lipids to esters at optimum conditions of 65 °C, 12 mL g−1 of methanol-to-dry biomass, 4 wt% of magnetic catalyst and 6 h of reaction time. The magnetic K/Fe2O3–Al2O3 core-shell nanocatalyst was reused for several times and presented high stability with less reduction in its activity until six runs.

Biodiesel synthesis from Garcinia gummi-gutta (L. Robson) seed oil: fuel feasibility evaluation of a novel feedstock by homogeneous and heterogeneous transesterification

ABSTRACTGarcinia gummi-gutta (L. Robson) seed oil (GGO), a novel feedstock with high oil content (33.5 wt%), was subjected to homogeneous and heterogeneous transesterification using NaOH, KOH and CaO. The low polyunsaturation (1.7 wt%), high monounsaturation (55.2 wt%) and moderate saturation (39.72 wt%) is a promising factor for biodiesel synthesis. A biodiesel yield of 97.2 and 97% was achieved using NaOH and KOH, respectively, during homogeneous transesterification under optimal conditions: catalyst 1.4wt% (NaOH) 1.6wt% (KOH), molar ratio 1:6, stirring rate 800 rpm, temperature 55°C, time 1.5 h. With CaO as basic heterogeneous catalyst, a yield of 96.5% was accomplished under optimal conditions: catalyst wt% 4.5, molar ratio 1:9, stirring rate 1000 rpm, temperature 60°C, time 2.5 h. High stirring rate played a significant role and resulted in better yield at economical catalyst wt%, moderate temperature and low methanol:oil molar ratio in a short interval of time. The reusability of the CaO catalyst offers a more economical, ecofriendly way of biodiesel synthesis compared to homogeneous alkali catalysts. Even after 10 cycles, CaO was effective for transesterification. The separation of biodiesel was easier in the order CaO > KOH > NaOH. The fuel properties were evaluated as per Bureau of Indian Standards.

Biodiesel synthesis from cottonseed oil using homogeneous alkali catalyst and using heterogeneous multi walled carbon nanotubes: Characterization and blending studies

The trans-esterification of cottonseed oil using strong alkali catalyst and using multi walled carbon nano tubes as catalyst to produce biodiesel was studied. The interaction effects of various factors such as temperature, amount of alkali used, alcohol to oil ratio and reaction time on yield of biodiesel were studied. The maximum yield of 95% biodiesel was obtained. The biodiesel produced was characterized using FT-IR spectral analysis and GC–MS analysis to ascertain the various functional groups and compounds available in it. The properties of biodiesel using homogeneous alkali catalyst and heterogeneous multi walled carbon nanotubes such as calorific value (36.18MJ/kg, 33.78MJ/kg), flash point (160°C, 156°C) and other properties such as viscosity, cloud point, pour point and density were found to determine the quality of biodiesel produced. The studies were done by blending the biodiesel produced with diesel and properties of blended samples were estimated to ascertain the use of blended samples in internal combustion engines.

Use of reactive distillation in biodiesel production: A simulation-based comparison of energy requirements and profitability indicators

The advent of biodiesel, as a viable alternative to replace crude-based diesel as transport fuel, has prompted growing interest worldwide due to the need for low-emission fuels. In this work, two reactive distillation processes using soybean oil as main feedstock along with the corresponding downstream separation units are simulated: the first process involves a homogeneous alkali catalyst; whereas the second involves a heterogeneous catalyst. Both processes yield a high purity biodiesel product. In the present work, ASPEN Plus v8.4 is used as the process simulation tool. The energy requirements of both processes were evaluated based on the optimization of the distillation column duties and performing heat integration on the process streams. The optimization of the column duties was performed by analyzing the Column Grand Composite Curves (CGCC). The process streams were heat integrated, and a Heat Exchanger Network (HEN) was designed to minimize utility consumption. Both processes were compared using profitability indicators such as Return-On-Investment (ROI), payback period and unit production cost. The results show that the heterogeneous-catalyzed process is more profitable than the alkali-catalyzed process for biodiesel production. The ROI, payback period and unit production cost were 486%, 0.2years and $0.712 per kg of biodiesel respectively. For the analysis, an annual production capacity of 35.4kilotonnes/year of biodiesel production was assumed.

The wastewater treatment in the biodiesel production with alkali-catalyzed transesterification

Abstract Biodiesel has been studied in last few decades because of limited energy resources and a huge increase of the energy demand. The basic feedstocks for the production of biodiesel are vegetable oils and animal fats that contain primarily triacylglycerols while the main reaction is transesterification. This reaction is most frequently conducted at commercial scale in the presence of the homogeneous alkali catalyst. Previous studies on biodiesel were mainly focused on its production and fuel properties, while its environmental management is rarely considered. The present work is a review of the previous studies on treating wastewaters generated by the biodiesel production processes involving alkali-catalyzed transesterification. The attention is focused on physical, chemical, physico-chemical, electrochemical, biological and integrated treatment processes of biodiesel wastewaters. Both advantages and disadvantages of different biodiesel wastewater treatment processes are discussed. Since different input biodiesel wastewaters are employed in different studies, it is difficult to compare different treatments with respect to their contaminant removal efficiencies. Proper acidification and chemical coagulation/flocculation or electrocoagulation remove grease and oil successfully but they are unsuccessful in removing COD. The combinations of acidification, coagulation and the electrochemical treatment improve the removal efficiencies of COD and BOD. Advanced oxidation technologies appear not to be effective in removing the contaminants from raw biodiesel wastewaters. The performance of biological processes is improved by the pretreatment of biodiesel wastewater with acidification, chemical coagulation, electrocoagulation or photo-Fenton. When selecting a treatment process, it should be evaluated with respect to its treatment efficiency and operational requirements. The right choice is probably an integration treatment involving acidification, coagulation/flocculation or electrocoagulation and a biological process. The reuse of the pretreated wastewater is also an interesting alternative.

Potassium fluoride impregnated CaO/NiO: An efficient heterogeneous catalyst for transesterification of waste cottonseed oil

Potassium fluoride impregnated CaO/NiO has been prepared by wet impregnation method in nano particle form as supported by powder XRD, scanning electron microscopy, and transmission electron microscopy studies. Brunauer–Emmett–Teller surface area and basic sites measurement studies have been performed to establish the effect of potassium fluoride impregnation on catalyst surface morphology and basic strength. CaO/NiO impregnated with 20 wt% potassium fluoride was used as solid catalyst for the transesterification of waste cottonseed oil having up to 5.8 wt% free fatty acid content. The variables used for the transesterification were, KF impregnated on CaO/NiO, catalyst concentration, reaction temperature, and methanol to oil molar ratio. Reaction parameters have been optimized to achieve the least reaction period for the completion of the reaction. Complete transesterification (>99% FAMEs yield) of waste cottonseed oil with methanol (1:15 molar ratio) required 4 h in the presence of 5 wt% catalyst (with respect to oil) at 65°C. Reusability study suggests that catalyst could be recycled for four successive runs without significant loss in activity. A pseudo first order kinetic equation was applied to evaluate the kinetic parameters and under optimized conditions first order rate constant and activation energy was found to be 0.023 min−1 and 41.2 kJ/mol, respectively. Few physicochemical properties of the prepared biodiesel sample have also been studied and compared with standard values.Practical applications: In India, application of edible vegetable oils for biodiesel production is prohibited to avoid food versus fuel situation. Application of waste cottonseed oil (WCO) for biodiesel production could circumvent this problem. However, homogeneous alkali catalyst could not be employed due to the presence of high free fatty acid contents in such feedstock. In this context present study demonstrates the impregnation preparation of KF impregnated CaO/NiO and its application as reusable solid catalyst for the transesterification of WCO.

Evaluation of catalytic activity of two functionalized imidazolium ionic liquids for biodiesel fuel production by a two-stage process

BACKGROUND Today commercial biodiesel processes use mainly homogeneous alkali catalysts when the feedstock is from refined oil with low FFA content. However, acidic catalysts become important when dealing with cheap feedstock that contains high amounts of FFA (>0.5%), such as crude oils and waste oils. Unfortunately, acid catalyst requires extensive and expensive purification steps for recovery from the valuable esters. Hence this study investigated the production of biodiesel from crude palm oil (CPO) containing high FFA content by a two-stage ionic liquid–KOH catalyzed process. To evaluate their catalytic activities, two functionalized imidazolium ionic liquids (ILs) with different anions were tested for esterifying the FFA. RESULTS Among the ILs investigated, 1-butyl-3-(3-sulfopropyl)-imidazolium hydrogensulfate (BSPIMHSO4) was found to be the better catalyst. Based on the experimental results, a BSPIMHSO4 concentration of 4.0 wt%, methanol:CPO molar ratio of 12:1, temperature of 150°C, and agitation speed of 600 rpm offered FFA conversion of 95.7% within 2 h. In the second step, at optimum conditions of 6:1 mole ratio of methanol:esterified CPO, 60°C, 600 rpm and 50 min; 1.0 wt% of KOH was used a catalyst for the transesterification reaction. The results obtained showed that the properties of synthesized biodiesel conform with the international standard specifications. CONCLUSION To understand the catalytic behavior of the IL during biodiesel synthesis, the effect of ionic liquid on the kinetics of esterification catalysis needs to be considered. © 2013 Society of Chemical Industry

Synthesis of oxygenated fuel additives via the solventless etherification of glycerol

The synthesis of oxygenated fuel additives via solvent freebase-catalyzed etherification of glycerol is reported. The products of glycerol etherification arediglycerol (DG) and triglycerol (TG) with DG being the favorable one. The catalytic activity of different homogeneous alkali catalysts (LiOH, NaOH, KOH and Na2CO3) was investigated during the glycerol etherification process. LiOH exhibited an excellent catalytic activity during this reaction, indicated by the complete glycerol conversion with a corresponding selectivity of 33% toward DG. The best reaction conditions were a reaction temperature of 240°C, a catalyst/glycerol mass ratio of 0.02 and a reaction time of 6h. The influences of various reaction variables such as nature of the catalyst, catalyst loading, reaction time and reaction temperature on glycerol etherification were elucidated. Industrially, the findings attained in this study might contribute towards promoting the biodiesel industry through utilization of its by-products.

Is Excess Methanol Addition Required To Drive Transesterification of Triglyceride toward Complete Conversion?

To clarify whether excess methanol addition is required to drive the transesterification of triglyceride toward complete conversion, the effect of the molar ratio of methanol to triglyceride on the reaction behavior was studied using not only the conventional homogeneous alkali catalyst but also the novel heterogeneous anion-exchange resin catalyst. For the heterogeneous anion-exchange resin catalyst, the transesterification completely proceeded even at the stoichiometric molar ratio of 3:1 because the saponification, which preferentially proceeded at the lower molar ratio of methanol to cause the catalyst depletion and the product contamination, never occurred. The reaction rate at 3:1 was much higher than that at the molar ratio of 6:1, widely used in the industrial production process of the biodiesel fuel. This was because the homogeneous single phase was formed at 3:1 and the mass-transfer resistance between the methanol/triglyceride phases disappeared.

Comparison of the performance of different homogeneous alkali catalysts during transesterification of waste and virgin oils and evaluation of biodiesel quality

A large amount of studies might be found regarding the improvement of biodiesel production; however, there is a lack of information concerning both, the simultaneous comparison of the catalyst performance for different raw materials, and the final product quality. Therefore, the objective of the present study was to evaluate: (i) the biodiesel synthesis from waste frying oil, sunflower and soybean refined oil using KOH, NaOH and CH 3ONa as catalysts; and (ii) the final product quality according to European biodiesel standard EN 14214. The results obtained showed that the use of virgin oils resulted in higher yields (reaching 97%) as compared to waste frying oils (reaching 92%). From the quality parameters, the ones that mostly depended on the reaction conditions were the kinematic viscosity and the methyl ester content (purity). Overall, KOH was less effective than the sodium based catalysts because, using KOH, purity was lower than the minimum required according to standard EN 14214 for all samples. Considering the studied feedstock, the optimum conditions which ensured that the final product was in agreement with the European biodiesel standard were: (i) 0.6 (wt%) CH 3ONa for both virgin oils; (ii) 0.6 (wt%) NaOH for sunflower oil and 0.8 (wt%) for soybean oil and; (iii) 0.8 (wt%) using both sodium based catalysts for waste frying oils. Under optimum conditions, a purity of 99.4 (wt%) could be obtained.

Transesterification of triacetin with methanol on Nafion ® acid resins

Although homogeneous alkali catalysts (e.g., NaOH) are commonly used to produce biodiesel by transesterification of triglycerides (vegetable oils and animal fats) and methanol, solid acid catalysts, such as acidic resins, are attractive alternatives because they are easy to separate and recover from the product mixture and also show significant activity in the presence of fatty acid impurities, which are common in low-cost feedstocks. To better understand solid acid catalyst performance, a fundamental transesterification kinetic study was carried out using triacetin and methanol on Nafion ® (perfluorinated-based ion-exchange resin) catalysts. In particular, Nafion ® SAC-13 (silica-supported Nafion) and Nafion ® NR50 (unsupported Nafion) were investigated, because both show great promise for biodiesel-forming reactions. The reaction kinetics for a common homogeneous acid catalyst (H 2SO 4) were also determined for comparison. Liquid-phase reaction was performed at 60 °C using a stirred batch reactor. The swelling properties of the resin in solvents of diverse polarity that reflect solutions typically present in a biodiesel synthesis mixture were examined. The initial reaction rate was greatly affected by the extent of swelling of the resin, where, as expected, a greater effect was observed for Nafion ® NR50 than for the highly dispersed Nafion ® SAC-13. The reaction orders for triacetin and methanol on Nafion ® SAC-13 were 0.90 and 0.88, respectively, similar to the reaction orders determined for H 2SO 4 (1.02 and 1.00, respectively). The apparent activation energy for the conversion of triacetin to diacetin was 48.5 kJ/mol for Nafion ® SAC-13, comparable to that for H 2SO 4 (46.1 kJ/mol). Selective poisoning of the Brønsted acid sites on Nafion ® SAC-13 using pyridine before transesterification revealed that only one site was involved in the rate-limiting step. These results suggest that reaction catalyzed by the ion-exchange resin can be considered to follow a mechanism similar to that of the homogeneous catalyzed one, where protonated triglyceride (on the catalyst surface) reaction with methanol is the rate-limiting step.