Methanol Dosage Research Articles

Synthesis of Zr/La-BTC Bimetallic Metal-Organic Framework (MOF) for Oleic Acid Esterification

Biodiesel plays an essential role in renewable energy as an alternative fuel to tackle the challenges of global warming, environmental degradation, and alternative fossil fuels. Oleic acid can be converted into biodiesel by the esterification process, which employs heterogeneous catalysts such as metal-organic frameworks (MOF). In this study, Zr/La-BTC MOFs were used as different kinds of catalysts to change oleic acid into biodiesel. The characterization results of Zr-BTC, La-BTC, and Zr/La-BTC using FTIR and XRD show that the MOF has been successfully formed. The crystallite sizes for La-BTC, and Zr/La-BTC MOFs are 15.7407 nm and 39.0392 nm, respectively. The surface area of Zr-BTC, La-BTC, and Zr/La-BTC MOFs are 167.101 m2/g, 12.328 m2/g, and 4.764 m2/g. The morphology of Zr-BTC MOF using SEM is irregular, La-BTC is rod-shaped crystal, and Zr/La-BTC is like a knot bond with a narrow waist. The most optimal reaction was obtained at a 5% (w/w) catalyst dosage of total oleic acid and methanol (1:60 mol), 65 °C, and a reaction time of 4 hours, producing 78.11% oleic acid conversion. GC-MS analysis identified that the biodiesel contains oleic acid, palmitic acid, methyl oleate, and methyl palmitate.

Water-Soluble Fe(III) Complex Catalyzed Coupling Aquathermolysis of Water-Heavy Oil-Methanol

In this experimental study, diverse water-soluble Fe(III) complexes were synthesized and employed to catalyze the aquathermolysis of heavy oil. A ternary reaction system comprising heavy oil, water, and methanol was established to facilitate the process. Viscometry, thermogravimetric analysis, DSC, and elemental analysis were utilized to thoroughly investigate the treated heavy oil. The findings reveal that, under optimal conditions of water, catalyst, and methanol dosage, the viscosity of heavy oil can be significantly reduced by up to 88.22% after reacting at 250 °C for 12 h. Notably, apart from viscosity reduction, the catalytic aquathermolysis also effectively removes heteroatoms such as sulfur, nitrogen, and oxygen, enabling in situ modification and viscosity reduction of heavy oil. This study demonstrates the potential of water-soluble Fe(III) complexes in enhancing the efficiency of heavy oil extraction and processing.

Short alkyl-imidazolium ionic liquids enhanced in-situ transesterification of microalgae

Ionic liquids (ILs) catalyzed in-situ transesterification (IST) of microalgae is a promising strategy to improve biodiesel yield through enhancing cellulose solubility and catalyzing transesterification. Effect of anions of ILs on biodiesel has been widely investigated previously. However, how do cations of ILs affect IST of microalgae is still unclear. On this basis, ILs composed of alkyl-imidazolium cations with different length, 1-ethyl-3-methylimidazolium tetrafluoroborate ([Emim][BF4]), 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]), and 1-hexyl-3-methylimidazolium tetrafluoroborate ([Hmim][BF4]) catalyzed IST of microalgae are experimentally and theoretically investigated. The results indicate that increasing alkyl chains of cations weakens interactions of ILs-cellulose, and reduces acidities of ILs, subsequently leads to decrease of cellulose extraction yield and biodiesel yield. Although cellulose extraction yield and biodiesel yield are affected by reaction temperature, dosage of methanol, and MILs: Algae, however, H-bonding interactions of ILs-cellulose and acidities of ILs are still dominate parameters affecting cellulose extraction yield and biodiesel yield, respectively, leading to their unchanged sort under variable reaction conditions as following: [Emim][BF4] > [Bmim][BF4] > [Hmim][BF4]. This work reveals that short alkyl chain of cation is favorable to both cellulose extraction and biodiesel yield, providing theoretical guides for screen and design of benign ILs to further improve biodiesel of in-situ transesterification of microalgae.

Investigation on in-situ deoxygenation performance of bio-oil model compound guaiacol over Ce-Fe/Al2O3 catalyst

The investigation of the low-cost deoxygenation of guaiacol (GUA, a model bio-oil compound) is of importance for upgrading bio-oil. At present, common sulfide catalysts for GUA deoxygenation reactions cause contamination of the liquid product, and noble metal catalysts are economically disadvantageous. In this study, four reduced Fe-based oxides with different Ce doping ratios were prepared and their effects on the in-situ deoxygenation performance of GUA in aqueous/methanol hydrogen donor solvents were explored. The results based on the deoxygenation degree, conversion degree, and higher heating value (HHV) of the products showed that the oxide catalyst with a Fe/Ce molar ratio of 2:1 in the methanol solvent performed very well. After selecting an excellent catalyst and a better hydrogen donor solvent, four factors (reaction temperature, reaction time, volume ratio of GUA dosage and methanol dosage, and the ratio of catalyst dosage at the bottom of the reactor to that at the top) in the deoxygenation degree of GUA were investigated using an orthogonal experimental method to further explore the performance of the catalyst. The results showed that the reaction temperature and time greatly influenced GUA deoxygenation. Under optimal experimental conditions, the deoxygenation degree and conversion degree of GUA could reach 34.36% and 92.56%, respectively, based on the relative peak area of gas chromatography–mass spectrometry, and the HHV of the liquid product was 32.27 MJ/kg. Although Fe/Ce catalysts mainly promote demethoxylation, demethylation, and methylation, the stability and quality of the liquid products were improved compared with GUA owing to the reduction in phenolic hydroxyl and ether content. The reduced catalyst in the process of GUA in-situ deoxygenation reactions in methanol maintained a steady performance, as revealed by X-ray diffraction and X-ray fluorescence.

Retention of high-value tocols during enzymatic esterification of palm fatty acid distillate using liquid lipase for improving the economics and sustainability of biodiesel production

Liquid lipase has recently been gaining popularity in converting secondary lipid feedstocks to biodiesel. However, it was unknown whether enzymatic biodiesel production could affect the retention of high-value phytonutrient(s) in the feedstocks. For the first time, the retention of tocols (a highly potent antioxidant) during enzymatic conversion of palm fatty acid distillate (PFAD) to biodiesel using a low-cost liquid lipase, Eversa® Transform 2.0, was studied. This study investigated the effects of methanol dosage on ester and fatty acid contents alongside tocols retention. The highest ester content (92.03 wt%) was achieved within a short reaction time of 4 h using 2 wt% enzyme concentration and 3:1 methanol-to-PFAD molar ratio. Interestingly, tocols retention was found to be correlated to the extent of fatty acid conversion. The maximum tocols retention was determined to be 91.98%. After vacuum distillation, the tocols content was enriched 25-fold (∼66,000 ppm) in the heavy phase, whereas the ester content increased to ∼96 wt% in a light-colored distillate (biodiesel). In conclusion, it is feasible to efficiently produce high-value phytonutrient(s) alongside biodiesel from secondary feedstock via an enzymatic route using a liquid lipase. The findings from this work provide the industry an opportunity to improve process economics and sustainability of biodiesel production.

Transfer-Free Quasi-Suspended Graphene Grown on a Si Wafer.

The direct growth of graphene affording wafer-scale uniformity on insulators is paramount to electronic and optoelectronic applications; however, it remains a challenge to date, because it entails an entirely different growth mode than that over metals. Herein, the metal-catalyst-free growth of quasi-suspended graphene on a Si wafer is demonstrated using an interface-decoupling chemical vapor deposition strategy. The employment of lower-than-conventional H2 dosage and concurrent introduction of methanol during growth can effectively weaken the interaction between the synthesized graphene and the underlying substrate. The growth mode can be thus fine-tuned, producing a predominantly monolayer graphene film with wafer-level homogeneity. Graphene thus grown on a 4 inch Si wafer enables the transfer-free fabrication of high-performance graphene-based field-effect transistor arrays that exhibit almost no shift in the charge neutral point, indicating a quasi-suspended feature of the graphene. Moreover, a carrier mobility up to 15 000 cm2 V-1 s-1 can be attained. This study is anticipated to offer meaningful insights into the synthesis of wafer-scale high-quality graphene on dielectrics for practical graphene devices.

MOF-Derived Co3O4 Nanoparticles Catalyzing Hydrothermal Deoxygenation of Fatty Acids for Alkane Production

Designing economical and nonprecious catalysts with a catalytic performance as good as that of noble metals is of great importance in future renewable bioenergy production. In this study, the metal–organic framework (MOF) was applied as a precursor template to synthesize Co3O4 nanoparticles with a carbon matrix shell (denoted as M-Co3O4). To select the synthesized optimal catalyst, stearic acid was chosen as the model reactant. The effects of catalyst dosage, methanol dosage, water dosage, temperature, and reaction time on catalytic efficiency were examined. Under the designed condition, M-Co3O4 exhibited high catalytic performance and the catalyst showed higher conversion of stearic acid (98.7%) and selectivity toward C8–C18 alkanes (92.2%) in comparison with Pt/C (95.8% conversion and 93.2% selectivity toward C8–C18). Furthermore, a series of characterization techniques such as scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption isotherms (Brunauer–Emmett–Teller (BET) method), and thermogravimetric analysis (TGA) was applied to investigate the physicochemical properties of the catalysts. Finally, we proposed that decarbonization (deCO) could be the presumably mechanistic pathway for the production of C8–C18 alkanes from the decomposition of stearic acid.

Comparison of different small molecular weight alcohols for sustaining sulfidogenic bioreactors maintained at moderately low pH.

Sulfate-reducing bacteria (SRB) catalyse the dissimilatory reduction of sulfate to hydrogen sulfide using a wide range of small molecular weight organic compounds, and hydrogen, as electron donors. Here we report the effects of different combinations of small molecular weight alcohols on the performance and bacterial composition of a moderately low pH sulfidogenic bioreactor (pH 4.0–5.5) operated at 35°C in continuous flow mode. Ethanol alone and methanol or ethanol used in combination with glycerol were evaluated based on their equivalent amounts of carbon. Although evidenced that methanol was utilised as electron donor to fuel sulfidogenesis at pH 5.5, rates of sulfate reduction/sulfide production were negatively impacted when this alcohol was first introduced to the system, though these rates increased in subsequent phases as a result of adaptation of the microbial community. Further increased dosage of methanol again caused rates of sulfidogenesis to decrease. Methanol addition resulted in perturbations of the bioreactor microbial community, and species not previously detected were present in relatively large abundance, including the sulfate-reducer Desulfovibrio desulfuricans. Ethanol utilization was evidenced by the increase in rates of sulfidogenesis as the dosage of ethanol increased, with rates being highest when the bioreactor was fed with ethanol alone. Concentrations of acetate in the effluent liquor also increased (up to 8 mM) as a result of incomplete oxidation of ethanol. This alcohol continued to be used as the electron donor for sulfate reduction when the bioreactor pH was decreased incrementally (to pH 4.0), but rates of sulfidogenesis decreased. The relative abundance of Dv. desulfuricans diminished as the bioreactor pH was lowered, while that of the acidophilic Firmicute Desulfosporosinus acididurans increased. This study has shown that all three alcohols can be used to fuel microbial sulfidogenesis in moderately acidic liquors, though the cost-effectiveness, availability and toxicity to the microbial community will dictate the choice of substrate.

The desulfurization of coal tar pitch with potassium permanganate oxidation method

Needle coke is widely used as precursor of some carbon material, such as graphite electrodes or negative material for lithium-ion battery of new energy vehicle. Coal tar pitch (CTP) is its raw material. The sulfur content in the CTP has an adverse effect on the quality of needle coke. Therefore, reducing the sulfur content in CTP has important practical significance to produce high-quality needle coke. The common methods of hydrogenation or oxidation for the CTP desulfurization is not easy operation with high energy consumption. This paper innovatively proposed a new method that is easy operation with low energy consumption for desulfurization of the CTP. It is carried out under room temperature and pressure with KMnO4 as the oxidant, ferric chloride (FeCl3) as the catalyst, and methanol as an extractant. The single factor method was used to investigate the optimal condition of oxidant concentration, oxidant dosage, methanol dosage, and reaction time on the desulfurization rate (DR) of the CTP. The result showed that the DR of the CTP reached 62% at the optimal condition. The remove ratio of different forms of sulfur in the CTP was in the order of thiophene sulfur > mercaptan and thioether > sulfoxides. This method was effective and showed promising in commercial application.

Mixotrophic denitrification for enhancing nitrogen removal of municipal tailwater: Contribution of heterotrophic/sulfur autotrophic denitrification and bacterial community

The heterotrophic and autotrophic denitrification system can be used to remove wastewater nitrogen effectively. However, the relationship between nitrogen removal performance and microbial community composition variation needs to be explored further. Therefore, a combined heterotrophic‑sulfur autotrophic biofilter (HSAD) was established to remove nitrogen from municipal tailwater. As methanol dosage increased from 12 mg/L to 36 mg/L, NO3−-N removal efficiency increased from 86.1% to 98.9%, and the generation of SO42− in the effluent was controlled within 167.6–113.2 mg/L under the condition of 30 mg/L NO3−-N in influent and 3 h hydraulic retention time. Increasing methanol dosage promoted the synergism of heterotrophic denitrification (HD) and sulfur autotrophic denitrification (SAD). Different denitrification performance was associated with the microbial community composition. Proteobacteria, Bacteroidetes, and Chloroflexi were major phyla with cumulative abundance of over 70% and Proteobacteria was predominate in all samples. Denitrifying bacteria, such as Ferritrophicum, Thiobacillus, Thauera and Comamonas dominated in different operation stages of mixotrophic reactor. The decrease in dominant HD bacteria accompanied with the increase in SAD bacteria, and the SAD bacterial richness declined with the rise of HD contribution in the total denitrification process. Correlation networks analysis indicated that the dominant bacteria had positive or negative correlation with each other, but a stable coexistence state of microbial community structure was formed under the mixotrophic conditions. This work deepens our understanding of HSAD and reveals the interconnection between nitrogen removal mechanism and microbial community composition variation.

Application of Ag/TiO2 in photocatalytic degradation of 2,2′,4,4′-tetrabromodiphenyl ether in simulated washing waste containing Triton X-100

Pollution by polybrominated diphenyl ethers (PBDEs) has been a major concern due to their bioaccumulation, persistence, and carcinogenicity. This study aims to use Ag/TiO2 for photocatalytic degradation of PBDEs in washing wastes to reuse Triton X-100 (TX-100) surfactant. The results indicated that Ag/TiO2 accelerated 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) photocatalytic degradation in TX-100 surfactant solutions under anaerobic conditions. When the catalyst is 200 mg/L and the Ag loading is 5%, BDE-47 shown the fastest degradation rate. The adsorption experiments confirmed that BDE-47 adsorption on the photocatalyst or held in micelles depended significantly on the initial concentration of TX-100 (CTX-0). The BDE-47 degradation rate increased first and then decreased with the increasing initial CTX-0 and reached the fastest degradation rate of 0.982 min−1 at 4 CMC. The TX-100 adsorption monolayer on Ag/TiO2 can capture the BDE-47 molecules remarkably well, leading to BDE-47 degradation due to the accumulated electrons on Ag0 in the photocatalysis process. The BDE-47 mainly decays to lower-brominated diphenyl ethers and fewer products accumulated in the Ag/TiO2 system. The loss of TX-100 could be attributed to oxidation by the holes and •OH. The addition of methanol could accelerate the photocatalytic degradation of BDE-47 and decrease the decay of TX-100 during the photocatalysis process. The best methanol dosage is 1%.

Biodiesel production catalysed by low-cost liquid enzyme Eversa® Transform 2.0: Effect of free fatty acid content on lipase methanol tolerance and kinetic model

A low-cost liquid lipase from genetically modified Aspergillus oryzae (Eversa® Transform 2.0) was used in this study for biodiesel production. The catalytic performance of this enzyme was evaluated using refined palm oil adjusted with different free fatty acid (FFA) content. The methanol-to-oil molar ratio was varied from 1:1 to 8:1 to determine the reaction rate, ester conversion and methanol tolerance of this enzyme at different FFA content. The reaction was carried out at low temperature (40 °C) for 24 h using very low enzyme concentration (0.2 wt%). The results showed that the enzyme could tolerate a higher dosage of methanol and could increase reaction rate and conversion when higher FFA content was present in the feedstocks. A biodiesel conversion of 97% could be obtained when the feedstocks contained ≥80 wt% FFA. Furthermore, a new semi-empirical model based on the Ping-Pong Bi-Bi mechanism has been developed to estimate the reaction kinetics of biodiesel production from feedstocks containing a mixture of triacylglycerol and FFA. In conclusion, Eversa® Transform 2.0 can be used for the production of biodiesel from low-quality feedstocks containing high FFA content in a sustainable and economical manner.

Expression of a novel α-glucosidase from Aspergillus neoniger in Pichia pastoris and its efficient recovery for synthesis of isomaltooligosaccharides

A gene conferring α-glucosidase (AG) with high transglycosylation activity from Aspergillus neoniger (a non-niger strain belonging to section Nigri) was cloned and expressed in Pichia pastoris. As the cDNA construction retained intronic portions due to alternative splicing, the exonic portions of the gene were stitched using restriction digestion and overlap extension PCR. Pre-determined open-loop exponential feeding strategies were evaluated for methanol dosage to improve the recombinant enzyme synthesis during high-cell density cultivation in 5 L bioreactor. Specific growth rate of 0.1 h−1 resulted in the highest enzyme activity of 182.3 mU/mL in the supernatant, whereas the activity of 3.8 U/g dry cell weight was obtained in the cell pellet. There was negligible enzyme activity in the cell lysate, indicating that approximately 80 % accumulation of total enzyme is in the periplasm. Later, this unreleased fraction was extracted to 90 % yield using 25 mM cysteine. The enzyme was purified and validated using western blot analysis and MS/MS profile. The SDS PAGE analysis revealed three bands corresponding to 80, 38, and 33 kDa indicating the multimeric nature of the enzyme. Thus, obtained enzyme was utilized in synthesis of a potential prebiotic molecule, isomaltooligosaccharides (IMOs), which can be used as a sweetener and bulk filler in the food industry. This is the first report to demonstrate challenges in cloning and expression of transglycosylating α-glucosidase from Aspergillus neoniger.

In situ transesterification of wet sewage sludge via hydrothermal process: Biodiesel production and residue utilization

Recent studies show the feasibility of choosing sewage sludge as feedstock to produce biodiesel. However, low yield of biodiesel as using wet sludge directly, high cost of the pretreatment of sludge drying, and poor cognition about residues utilization, lead to the urgent need of new processes. In this study, hydrothermal process (HP) was introduced for biodiesel production by in situ transesterification. A favorable condition was determined as methanol dosage of 20 g g−1 dried sludge, and 2% sulfuric acid at 160 °C for 4 h, where the biodiesel yield reached 8.63%. HP also shows the ability to break the distinction of biodiesel yield derived from wet or dried sludge, since a similar yield of 8.71% was obtained when using dried sludge as feedstock. Furthermore, solid and liquid residues from HP could be applied as adsorbent for organic pollutant removal and nutrient substrate for yeast cultivation, respectively. A maximum adsorption capacity of 75.52 mg g−1 for Congo red (CR) was obtained using the solid residue as adsorbent. A 4.6 g L−1 biomass of Candida utili and 35.33% of protein in yeast cell were harvested using the liquid residue as nutrient substrate. This study not only demonstrates the feasibility of applying HP for biodiesel production from wet sludge, but also brings new insights about full utilization of wet sludge.

Enhanced isophthalonitrile complexation-reduction removal using a novel anaerobic fluidized bed reactor in a bioelectrochemical system based on electric field activation (AFBR-EFA)

On account of the recalcitrant and highly toxicity of organonitrile substrates, traditional processes are limited by HCN poisoning thus inefficient. This article proposed a novel anaerobic fluidized bed reactor with electric field activation (AFBR-EFA) which had a 260-day continuous operation. The operation aims to explore the practicability of the enhanced reduction of isophthalonitrile (IPN), with emphasis on the optimum operation parameters and synergistic effect between electric field and anaerobic processes. The results showed that relatively higher voltage (1.0 V < V < 1.6 V) had a positive impact on reduction enhancement. High removal could be obtained at high initial concentration, low methanol dosage and short HRT which indicated that tolerance to shock loading was significantly enhanced in AFBR-EFA. Furthermore, EFA visibly motivated the enrichment of electrochemically active bacteria and various autotrophic IPN degradation-related species. The significantly efficient performance makes the potential for full-scale application of the AFBR-EFA markedly improved, particularly for treating hard-biodegraded contaminants.

Reliability and efficiency of an advanced tertiary treatment process for wastewater reclamation

Abstract A reliability study for the reclamation of wastewater treatment plant effluent using continuous sand filtration-multimedia filtration (CSF-MMF) combined with ultrafiltration (UF) and reverse osmosis (RO) has been conducted. The objectives of the research are two-fold: (1) effluent of CSF-MMF can be used for surface water supplementation and (2) permeate of UF-RO can be applied as greenhouse irrigation water. The removal efficiencies for nutrients and electric conductivity (EC) as well as some operational parameters of the pilot plant were investigated. The concentration of T-N, chemical oxygen demand (COD) and turbidity in the filtrate of CSF-MMF with external C-course methanol dosage and FeCl3 dosage could be kept at less than 2.2 mg/L, 35 mg/L and 0.9 NTU respectively. Average EC exceeded the required surface water standard by 10% and it was difficult to meet the low surface water standard for T-P (below 0.15 mg/L). The EC of RO permeate was below 20 μS/cm, which was much lower than the standard for greenhouse irrigation. With frequent back flushes, cleaning in place (CIP) and enhanced cleaning the UF could be operated with a constant permeability of 100 L/(m2·h·bar). An appropriate CIP resulted in a recovery of 47–52% of the RO. The protective cartridge filter prior to the RO should be replaced every 2 weeks.

Bench-scale production of sewage sludge derived-biodiesel (SSD-BD) and upgrade of its quality

Even if sewage sludge gain acceptance as a potential feedstock for biodiesel (BD) production, water content and contaminants in sewage sludge still remain as obstacles for the production and quality of biodiesel, respectively. Crude BD was produced from a feedstock of wet sewage sludge with 85% water content via in-situ wet-transesterification in a bench-scale (10 L) reactor, and then further treated for enhancing the BD quality to a transportation grade through a series of refining processes. The wet-transesterification was optimized in terms of crude BD yield by varying methanol dosage, methanol/co-solvent (xylene) ratio and reaction time. The maximum crude BD yield and the fatty acid methyl ester (FAME) content were 11.05 and 67.41%, respectively, when methanol dosage, methanol/co-solvent and reaction time were 15 mL/g, 0.5 and 12 h, respectively. The refining process consisting of vacuum distillation, degumming and neutralization, which satisfied the BD standards (EN14214) and visually improved color and transparency. Based on GC-FID analysis, the FAME content in the refined BD highly increased by eliminating the residual impurities. Applicability of the refined BD as a transportation fuel was confirmed by comparing the quality of the BD blended with the commercial petroleum-diesel (PD) at 3% (BD3) with the standard specification.

Chemical Recycling of Bio-based Poly(3-hydroxybutyrate) Wastes Under Methanolysis Condition Catalyzed by Fe-Containing Magnetic Ionic Liquid

An efficient method for chemical recycling of bio-based polymers Poly(3-hydroxybutyrate) (PHB) wastes was established from the perspective of biorefinery. This methanolysis reaction archived successfully transformation PHB into corresponding monomer catalyzed by imidazolium-based Fe-containing ionic liquid, 1-butyl-3-methylimidazolium tetrachloroferrate ([Bmim]FeCl4). Compared with FeCl3 or ionic liquid [Bmim]Cl, this ionic liquid showed excellent catalytic performance. The obtained product methyl 3-hydroxybutyrate (M3HB) with high purity, as a chemical raw material, can be used in various fields. Investigation also indicated that the thermal stability of catalyst played an important role in this reaction, this ionic liquid could be reused for six times without apparent decrease in the conversion of PHB or yield of M3HB. Furthermore, the effects of experimental factors, such as temperature, time, catalyst dosage and methanol dosage on the methanolysis results of PHB were examined. Kinetic study indicated that this reaction was first-order kinetic reaction with activation energy of 27.44 kJ/mol. Additionally, a possible mechanism of PHB methanolysis was proposed.

Lipase-catalyzed transesterification of epoxidized soybean oil to prepare epoxy methyl esters

Epoxidized soybean oil methyl esters could be efficiently prepared with the transesterification of epoxidized soybean oil (ESBO) with a lower dosage of methanol using lipase Novozym 435 as catalyst. The optimum parameters were as follows: the molar ratio of 5:1 (methanol to ESBO), 5% Novozym 435 as catalyst, at 45 °C for 14 h, with a stirring speed of 600rpm, under which the epoxidized soybean oil methyl esters (ESBOME) could be obtained at a 95.7% yield. During the enzymatic transesterification process, the oxirane oxygen values were kept unchangeable, which indicated that excellent functional group tolerance could be achieved under such mild reaction conditions. In addition, the recyclability of the immobilized enzyme Novozym 435 in this transesterification process was examined and the results showed that the biocatalyst could be reused ten times without losing any reaction activity or selectivity. And the final products of ESBOME were also identified by IR and NMR analysis. The kinetic data obtained followed the Ping-Pong Bi mechanism model (Vmax = 6.132 mol·L-1min-1, Km,S = 0,0001 mol·L-1, Km, A = 796.148 mol·L-1, Ki, A = 0,0004 mol·L-1) with competitive inhibition by methanol.

Transient Simulation for Hydrate Mitigation Aims for Optimal Production in Kuwait Fields

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 182237, “Assuring Optimal Production and Enhanced Operational Efficiency Through Transient Simulation—A Case Study in North Kuwait Jurassic Fields,” by Mohammad Al-Sharrad, Kuwait Oil Company; Roshan Prakash, SPE, and Christian F. Trudvang, SPE, Schlumberger; and Noura Al-Mai, Abrar A. Hajjeyah, SPE, and Abdulaziz H. Al-Failakawi, SPE, Kuwait Oil Company, prepared for the 2016 SPE Asia Pacific Oil and Gas Conference and Exhibition, Perth, Australia, 25–27 October. The paper has not been peer reviewed. In the deep high-pressure/high-temperature North Kuwait Jurassic (NKJ) fields, the pipelines connecting the wells to the processing facility are neither buried nor insulated. During the winter, the well fluid cools to below hydrate-formation temperature in the flowline, causing hydrate crystallization and even plugging. This paper presents the traditional methods of hydrate mitigation used in the NKJ fields and the way in which a transient model was initially built and continuously improved. Challenges Hydrate Formation. When the well forms hydrates, usually at night and early morning in winter, the field operators must wait for the ambient temperature to rise in order to melt the hydrate plugs. In general, well production declines for 6–8 hours because of hydrates. Because hydrate formation is the main cause of concern, a robust solution is needed to minimize production downtime. No proper flow-assurance study or modeling was conducted to understand the effect of water and inhibition details on the hydrate curve. To address this challenge, a predictive transient tool is needed to know in advance when hydrate will start to form, the location of hydrate formation, and the required methanol (MeOH) dosage rate to avoid hydrate formation. The current practice of hydrate inhibition is mainly based on past experience. Injecting MeOH on the basis of past experience, without knowing the optimal MeOH-injection rate, could lead to other flow-assurance challenges. Slug Flow. Low-condensate/gas-ratio and high-water/gas-ratio wells have a tendency to create slug flow in the pipeline because of continuous changes in the phase holdups. Because of wide temperature fluctuations between night and day, the fluid in the pipeline is always in a transient state. The pipeline acts as storage because of its large volume (1,000–3,000 bbl). In the morning, when the pipeline is heated, the fluids expand and gas holdup increases in the line, which pushes the liquid to the facility and causes a surge at the facility inlet. At night, when the pipeline cools, liquid hydrocarbon accumulates in the line, increasing the liquid holdup. High-water wells always will have a tendency to accumulate water in the low-lying zones. This water generally moves as a slug. Modeling of the multiphase fluids to understand the slug behavior is required for balancing the fluid in and fluid out of the facility. Long and complicated flowline geometry further complicates the system dynamics and will affect the flow behavior.