Optimization of biodiesel production process in a continuous microchannel using response surface methodology

We assessed the biodiesel production process in a continuous microchannel through preparation of a heterogeneous catalyst (CaO/MgO) from demineralized water plant sediment. This mixed oxide catalyst was used for transesterification of rapeseed oil as feedstock by methanol to produce biodiesel fuel at various conditions. A microchannel, utilized as a novel reactor, was applied to convert rapeseed oil into biodiesel in multiple steps. The effects of the process variables, such as catalyst concentration, methanol to oil volume ratio, n-hexane to oil volume ratio, and reaction temperature on the purity of biodiesel, were carefully investigated. Box-Behnken experimental design was employed to obtain the maximum purity of biodiesel response surface methodology. The optimum condition for the production of biodiesel was the following: catalyst concentration of 7.875 wt%, methanol to oil volume ratio of 1.75: 3, n-hexane to oil volume ratio of 0.575: 1, and reaction temperature of 70 °C.     

A Transesterification Double Step Process — TDSP for biodiesel preparation from fatty acids triglycerides

This study introduces a two consecutive steps basic–acid transesterification process, (denominated Transesterification Double Step Process — TDSP) for biodiesel production from vegetable oils. The process involves homogeneous consecutive basic–acid catalysis steps and is characterized by formation of well-defined phases, easy separation procedures, high reaction velocity and high conversion efficiency. The proposed TDSP is different in relation to other traditional two-step procedures which normally include acid esterification followed by basic transesterification, or enzymatic or even supercritical transesterification conditions. The biodiesel (fatty acid methyl esters) was analyzed by standard biodiesel techniques in addition to ¹H-NMR, indicating high quality and purity biodiesel products. The transesterification of sunflower and linseed oils resulted in oil conversions higher than 97% corresponding to yields of 85%. A probable reaction mechanism responsible for the process is presented.     

利用熔融结晶法进行芴的提纯

以工业芴为原料，实验研究了利用熔融结晶法制备精芴的工艺过程，考察了结晶降温速率、结晶终温、发汗升温速率及发汗终温对产品纯度及收率的影响，得到了利用熔融结晶方法分离提纯芴的优化工艺条件，产品纯度可达97.4%。同时根据实验结果，对芴与2-甲基氧芴两元物系的固液平衡相图进行了推测分析。     

Optimization of fractional crystallization on crude biodiesel purification via response surface methodology

In order to improve separation and purification efficiency of biodiesel, an alternative method has been explored which is fractional crystallization. In this study, glycerol that has a higher melting point was formed as a solid phase while the pure biodiesel was remained in liquid phase during the crystallization process. Response surface methodology (RSM) and central composite design (CCD) were employed to search for the optimum operating conditions. The best responses were 0.117 and 46.734% for effective partition constant (K) and concentration efficiency (Eff), respectively, while the optimum operating conditions were coolant temperature at ?9.5°C and stirring rate at 362 rpm.     

Comparison of the Crystals Obtained by Precipitation of CL‐20 with Different Chemical Purity

The precipitation of CL‐20 with different chemical purity is presented herein. Studies have shown that the first crystallization of the crude CL‐20 does not allow achieving the expected polymorphic purity and slightly increases chemical purity. Further precipitation processes result in gradual increase of the chemical purity about 1–2 % and in the improvement of the properties of crystals, i.e. density, polymorphic purity, and sensitivity to friction. This paper attempts a preliminary purification of the crude CL‐20 with columns filled with activated charcoal. A material of high purity, obtained by this process, was used in the process of precipitation. As a result of the crystallization a sample of CL‐20 was obtained with high chemical purity of 99.5 % and significantly reduced sensitivity to friction (128 N) and to impact (4 J). Additionally, samples of CL‐20, recovered from the filtrate after crystallization with a chemical purity of about 88 %, were purified on columns filled with activated charcoal. In this process a significant amount of impurities was removed and the purity was increased to 96 %.     

Synthesis of AlPO4 Molecular Sieves with AFI and AEL Structures by Dry-Gel Conversion Method and Catalytic Application of Their SAPO Counterparts on Isopropylation of Biphenyl

AlPO₄-5 and AlPO₄-11 were synthesized by dry-gel conversion (DGC) method. Steam-assisted conversion (SAC) and vapor-phase transport (VPT) techniques were applied for this purpose. The synthesis was successful in presence of a certain minimum amount of external bulk water, without which the crystallization failed. Crystallization by VPT method was slower than corresponding SAC and HTS method. SAPO analogs of the samples, SAPO-5 and SAPO-11 were also synthesized by DGC method. Samples made by DGC methods had higher yield than the conventional hydrothermal synthesis (HTS); otherwise the samples showed similar characteristics as that made by HTS. XRD, SEM and N₂-adsorption results showed high crystallinity and purity of the samples made by DGC, and ²⁷Al MAS NMR spectra indicated the tetrahedral framework nature of Al. SAPO-5 and SAPO-11 were tested for their catalytic activity in isopropylation of biphenyl, and in terms of conversion and selectivity, SAPO-5 was found to be suitable for this application.     

Optimization of process conditions using response surface methodology for the microwave-assisted transesterification of Jatropha oil with KOH impregnated CaO as catalyst

A transesterification reaction of Jatropha curcas oil with methanol in the presence of KOH impregnated CaO catalyst was performed in a simple continuous process. The process variables such as methanol/oil molar ratio (X₁), amount of catalyst (X₂) and total reaction time (X₃) were optimized through response surface methodology, using the Box–Behnken model. Within the range of the selected operating conditions, the optimal ratio of methanol to oil, amount of catalyst and total reaction time were found to be 8.42, 3.17% and 67.9 min, respectively. The results showed that the amount of catalyst and total reaction time have significant effects on the transesterification reaction. For the product to be accepted as a biodiesel fuel, its purity must be above 96.5% of alkyl esters. Based on the optimum condition, the predicted biodiesel conversion was 97.6% while the actual experimental value was 97.1%. The above mentioned results demonstrated that the response surface methodology (RSM) based on Box–Behnken model can well predict the optimum condition for the biodiesel production.     

Comparison of membrane extraction with traditional extraction methods for biodiesel production

Three traditional methods for the refining step in biodiesel production were compared: (i) washing with distilled water; (ii) washing with acid (HCl); and (3) dissolving and extracting in a solvent (hexane or petroleum ether) and then washing with distilled water. Biodiesel with a high purity (97.5%) could be obtained by all three methods, but serious emulsification occurred during the refining processes, which led to high refining losses. A novel refining method was developed by using hollow fiber membrane extraction, and polysulfone was selected as the most suitable membrane. This process effectively avoided emulsification during refining and decreased the refining loss. The purity of the biodiesel obtained was about 99%; and other properties, such as density, kinematic viscosity, water content, and acid value, conformed to the standards.     

Simulation and cost estimate for biodiesel production using castor oil

Brazilian government has established a regulation that imposes the commercialization of diesel blended with 3% of biodiesel by volume. Castor oil has being considered an option to guarantee the supply of biodiesel needed. For this reason, in this work, a continuous biodiesel plant was designed and simulated in HYSYS simulator using castor oil as feedstock. The developed process was capable of producing biodiesel at high purity using an alkali catalyst. Material and energy flows, as well as sized unit operations were used to conduct an economic assessment of the process. Total capital investment, total manufacturing cost and after annual equivalent cost were also calculated. A study of production costs was performed considering the fluctuations of the raw material prices and the glycerin purification step.     

合成硝基麝香溶液结晶分离研究

为了开发低共熔组成酮麝香、二甲苯麝香混合物溶液结晶新过程,计算得到酮麝香、二甲苯麝香、溶剂三元相图。在此基础上研究了麝香混合物溶液结晶分离方法,提出了轮流加入乙腈和庚烷从低共熔组成麝香混合物中,分级冷却结晶分离得到2种产品的过程。由三元相图得到理论产量并进行试验验证,结果表明加入乙腈一级结晶可得到纯度为97.5%的二甲苯麝香,加入庚烷二级结晶后酮麝香的纯度为98.1%。     

Analysis of parameters and interaction between parameters of the microwave-assisted continuous transesterification process of Jatropha oil using response surface methodology

A simple continuous process was designed for the transesterification of Jatropha curcas (J. curcas) oil to alkyl esters using microwave-assisted method. The product with purity above 96.5% of alkyl ester is called the biodiesel fuel. Using response surface methodology, a series of experiments with three reaction factors at three levels were carried out to investigate the transesterification reaction in a microwave and conversion of alkyl ester from J. curcas oil with NaOH as the catalyst. The results showed that the ratio of methanol to oil, amount of catalyst and flow rate have significant effects on the transesterification and conversion of alkyl ester. Based on the response surface methodology using the selected operating conditions, the optimal ratio of methanol to oil, amount of catalyst and flow rate of transesterification process were 10.74, 1.26 wt% and 1.62 mL/min, respectively. The largest predicted and experimental conversions of alkyl esters (biodiesel) under the optimal conditions are 99.63% and 99.36%, respectively. Our findings confirmed the successful development of a two-step process for the transesterification reaction of Jatropha oil by microwave-assisted heating, which is effective and time-saving for alkyl ester production.     

结晶法提纯工业磷酸的数学模型与实验研究

为了制备电子级磷酸,采用了悬浮结晶法对工业磷酸进行提纯。分析了结晶法提纯工业磷酸的原理,并基于结晶过程中杂质的有效分配系数对多次结晶后杂质的分布建立了晶体纯度预测模型,同时考察了酸浓度、结晶次数和磷酸原料杂质初始含量对磷酸提纯效果的影响。研究结果表明,采用结晶法提纯磷酸具有良好的效果,能有效地脱除所考察的五种杂质(Li、Mg、Al、Cr、Mn);以一次晶体为原料,在磷酸浓度为84%的条件下,经过3次结晶,和在磷酸浓度为88%的条件下,经过4次结晶,均可以达到美国典型半导体磷酸要求。所建立的晶体纯度预测模型能很好地预测杂质浓度随结晶次数的变化。     

Comparisons of Biodiesel Produced from Unrefined Oils of Different Peanut Cultivars

Biodiesels were prepared according to standard procedures from unrefined oils of eight commercially available peanut cultivars and compared for differences in physical properties important to fuel performance. Dynamic viscosity, kinematic viscosity and density were measured from 100 to 15 °C, and differences (p < 0.05) in these physical properties occurred more frequently at lower temperatures when comparing the different cultivars. Unlike data for the oil feedstocks, no meaningful correlations among biodiesel fatty acid profiles and either fuel viscosity or density were observed. Low temperature crystallization of the peanut biodiesels was measured via differential scanning calorimetry. Increased concentrations of long chain saturated fatty acid methyl esters (FAME) were associated with an increased propensity for low temperature crystallization, and the single FAME category most associated with low temperature crystallization was C:24. Tempering at 10 °C followed by analysis of the soluble fractions (winterization), improved crystallization properties and confirmed the importance that long chain saturated FAMEs play in the final functionality of peanut biodiesel. Peanut data is also compared to data for canola and soy biodiesels, as these feedstocks are more common worldwide for biodiesel production. Overall, this work suggests that minimizing the concentration of long chain saturated FAMEs within peanut biodiesel, either through processing and/or breeding efforts would improve the low temperature performance of peanut biodiesel.     

芴溶解度的测定及溶液结晶法提纯芴的工艺研究

在测定芴在甲醇、乙醇、正丁醇、甲苯、邻二甲苯中溶解度的基础上,确定正丁醇是溶液结晶法提纯芴的合适溶剂。介绍了采用溶液结晶法对工业芴的提纯分离的工艺过程及不同结晶条件对产品收率和纯度的影响,确定了利用溶液结晶提纯芴的最佳工艺条件,经提纯后可使芴的纯度由89.0%提高到96.6%或由95.0%提高到97.1%。     

Transesterification double step process modification for ethyl ester biodiesel production from vegetable and waste oils

In this study, the transesterification double step process (TDSP) was modified to enable the usage of ethanol as a transesterification agent in the production of biodiesel from vegetable and waste oils. The TDSP comprises a two-step transesterification procedure, which is initiated by a homogeneous basic catalysis step and followed by an acidic catalysis step. To optimize the transesterification parameters, different reaction mixtures and conditions were tested. Compared with methanol transesterification, larger ethanol and catalyst amounts as well as higher reaction times and temperatures were required. However, the results were consistent with those usually reported for ethanol transesterification. The obtained biodiesels (i.e., fatty acid ethyl esters (FAEEs)) were analyzed by standard physico-chemical techniques in addition to ¹H NMR, ¹³C NMR and FTIR spectroscopies, indicating high quality and purity biodiesel products. The obtained conversions were evaluated by ¹H NMR spectroscopy. For the optimized process, the triglyceride conversion to biodiesel was ?97% for all oils used. The overall process yields are considerably high when compared to the single basic catalysis yields.     

Synthesis of hierarchical ZSM-5 microspheres with superior performance for catalytic methanol-to-olefin conversion

Methanol-to-olefin (MTO) conversion on zeolites has encountered severe coke deposition and rapid deactivation. Creating different levels of porosity is essential to mitigate such issues. Herein, we demonstrate a facile and green strategy to synthesize uniform and hierarchically macro/mesoporous ZSM-5 microspheres by combining spray-freeze drying and steaming-assisted crystallization (SAC). The structure, crystallinity, and porosity of the zeolite microspheres are controlled by adjusting the water/gel mass ratio and time in the SAC process. The structure evolution during the SAC process is revealed. In the catalytic MTO reaction, the representative hierarchically porous ZSM-5 catalyst exhibits superior catalytic performance. At a very high weight hourly space velocity of 18 h⁻¹, it shows a dramatically prolonged lifetime (47 h at >99% conversion) and much-improved selectivity to ethylene and propylene compared with the conventional microporous ZSM-5 and nano-sized ZSM-5. The enhanced performance is originated from the hierarchical structure and suitable acidity of the ZSM-5 microspheres.     

Optimizing Conditions for the Purification of Linoleic Acid from Sunflower Oil by Urea Complex Fractionation

The separation and purification of linoleic acid (LA) from sunflower seed oil by urea complex fractionation was studied. Crystallization reaction conditions of urea inclusion were optimized using the response surface method, and the optimal model was developed. Using the linear weighting method of the fitting model for optimization, the optimal balance between the purity and the recovery of LA was obtained. Under optimal conditions, the purity of LA was 87.8%, and the recovery was 83.4% at a urea-to-fatty acids ratio (w/w) of 0.94, 95% ethanol-to-urea (v/w) of 5.00, a crystallization temperature of 18.0 °C, and a crystallization time of 5.0 h. Verification results revealed that the predicted values from these models were reasonably close to the experimentally observed values.     

Recovery and Recycling of Isopropyl Alcohol Used in Biodiesel Production From Yellow Mustard Oil

The recovery of solvents used during biodiesel synthesis is an important factor in the economic feasibility and sustainability of the entire process. In this study, we looked at the use of isopropyl alcohol (IPA) for oil extraction and biodiesel production, as well as its potential for recovery and recycling. We found that multistage extraction improved oil recovery, with up to 86% oil yield using four stages of extraction at an IPA:mustard flour (volume:weight) ratio of 1.5:1 at room temperature. Using acid–base‐catalyzed transesterification, 99% of the mustard oil was converted to biodiesel. At the end of this process, IPA was recovered from the azeotrope by salting out using potassium carbonate or sodium carbonate. The solubility behavior of the components was evaluated by means of ternary‐phase diagrams of IPA/water/sodium carbonate and IPA/water/potassium carbonate, which determined their liquid–liquid–solid equilibrium constants at ambient pressure and at room temperature. Using 20% (w:w) potassium carbonate, 95% of the IPA was recovered at 99% purity from a starting mixture of IPA containing 13% water. Azeotropic distillation of the IPA–water azeotrope with 10% potassium carbonate resulted in the recovery of 99% of the IPA at 94% purity. These results suggest that IPA is not only a suitable solvent for mustard‐oil extraction but also for salt‐enhanced azeotropic distillation resulting in near‐complete recovery from aqueous solutions.     

Statistical optimization for lithium silicate catalyzed production of biodiesel from waste cooking oil

Lithium silicate is one of the suitable heterogeneous catalysts for biodiesel production. The possibilities of large number of combinations of different reaction parameters make the optimization of biodiesel production process over various heterogeneous catalysts highly tedious, necessitating the development of alternate strategies for parameter optimization. Here, Box-Behnken design (BBD) coupled with response surface methodology (RSM) is employed to optimize the process parameters required for the production of biodiesel from waste cooking oil using lithium silicate as catalyst. Simple method of impregnation was performed for the material preparation and the catalyst was analyzed using different techniques. It was found that the activity is directly proportional to the basicity data obtained from temperature programmed desorption (TPD) of CO₂ over various catalyst systems. The material exhibits macroporous morphology and the major crystalline phase of the most active catalyst was found to be Li₂SiO₃. The effects of different reaction parameters were studied and a biodiesel yield of 100% was obtained under the predicted optimum reaction conditions of methanol : oil molar ratio 15 : 1, catalyst amount 7 wt%, reaction temperature 55 °C and reaction time 2.5 h. The validation experiments showed a correlation coefficient of 0.95 between the predicted and experimental yield of biodiesel, which indicates the high significance of the model. The fuel properties of biodiesel obtained under the optimum conditions met the specifications as mentioned in ASTM D6751 and EN 14214 standards. Catalyst heterogeneity and low reaction temperature are the major attractions of the present biodiesel preparation strategy.     

Synthesis of silicalite-1 by dry-gel conversion method: factors affecting its crystal size and morphology

Silicalite-1 crystals were synthesized from clear and diluted solutions by the dry-gel conversion method and the hydrothermal method was used as reference to do a comparative study. The effect of the structure-directing agent, silica source, aging time and crystallization time was investigated. Zeolite crystals, about 200–500 nm and 1 micron, were obtained by the liquid phase hydrothermal (LPH) and steam-assisted crystallization (SAC), called as dry-gel conversion method, respectively. The crystals were identified by XRD and SEM. The results show that the aging time and the water content are crucial in the synthesis of zeolites. Indeed, well formed zeolite crystals are obtained by the SAC technique using a lower amount of water than in the LPH method. However, the presence of the structure directing agent (SDA) into the dry gel determines the crystallization of silicalite-1.