Excess Methanol Research Articles

Pichia pastoris Mut(S) strains are prone to misincorporation of O-methyl-L-homoserine at methionine residues when methanol is used as the sole carbon source.

BackgroundOver the last few decades the methylotrophic yeast Pichia pastoris has become a popular host for a wide range of products such as vaccines and therapeutic proteins. Several P. pastoris engineered strains and mutants have been developed to improve the performance of the expression system. Yield and quality of a recombinant product are important parameters to monitor during the host selection and development process but little information is published regarding quality differences of a product produced by different P. pastoris strains.ResultsWe compared titer and quality of several Nanobodies® produced in wild type and MutS strains. Titer in fed-batch fermentation was comparable between all strains for each Nanobody but a significant difference in quality was observed. Nanobodies expressed in MutS strains contained a product variant with a Δ−16 Da mass difference that was not observed in wild type strains. This variant showed substitution of methionine residues due to misincorporation of O-methyl-l-homoserine, also called methoxine. Methoxine is likely synthesized by the enzymatic action of O-acetyl homoserine sulfhydrylase and we confirmed that Nanobodies produced in the corresponding knock-out strain contained no methoxine variants. We could show the incorporation of methoxine during biosynthesis by its addition to the culture medium.ConclusionWe showed that misincorporation of methoxine occurs particularly in P. pastoris MutS strains. This reduction in product quality could outweigh the advantages of using Mut strains, such as lower oxygen and methanol demand, heat formation and in some cases improved expression. Methoxine incorporation in recombinant proteins is likely to occur when an excess of methanol is present during fermentation but can be avoided when the methanol feed rate protocol is carefully designed.Electronic supplementary materialThe online version of this article (doi:10.1186/s12934-016-0499-2) contains supplementary material, which is available to authorized users.

Determination of methanol in Iranian herbal distillates.

Herbal distillates have been used as beverages, for flavoring, or as phytomedicines in many countries for a long time. Recently, the occurrence of blindness after drinking herbal distillates has created concerns in Iran. The aim of this study was to determine the concentrations of methanol in herbal distillates produced in Iran. Eighty-four most commonly used herbal distillates purchased from herbal distillate factories were analyzed for methanol contents by gas chromatography and flame ionization detection, with ethanol as internal standard. In 15 herbal distillates, the methanol concentration was below the limit of quantitation. The methanol concentrations in all samples ranged from 43 to 277 mg/L. Forty-five samples contained methanol in excess of the Iranian standard. The maximum concentration was found in an herbal distillate of Mentha piperita (factory E) (277±12), and the minimum in a distillate of Carum carvi (factory B) (42.6 ± 0.5). Since the 45 Iranian herbal distillates containing methanol levels were beyond the legal limits according to the Iranian standard, it seems necessary to monitor the amount of methanol and give a warning to watch out for the latent risk problem of methanol uptake, and establish a definitive relationship between the degree of intoxication observed and the accumulation of methanol in the blood.

Techno-economic evaluation of the direct conversion of CO2 to dimethyl carbonate using catalytic membrane reactors

The production of dimethyl carbonate (DMC) caught more interest in the past decades due to its versatile use (e.g. as fuel additive), low toxicity and fast biodegradability. Different ‘green’ production routes are being developed to replace the conventional and rather toxic production of DMC via phosgene. The direct conversion of CO2 and methanol toward DMC is an environmental and economically interesting production route for the chemical industry.This work describes the process design of the direct conversion of CO2 to dimethyl carbonate, providing a valuable insight and a better understanding of the process limitations. In this design, membrane reactors are used for continuous removal of water by-product, in order to overcome the equilibrium limitations. The rigorous Aspen Plus simulations show that even when using an excess of methanol, the attainable conversion is low and the DMC concentration in the reactor effluent is less than 1.5mol%. Purifying this diluted stream to the desired concentrations demands large size equipment and a substantial amount of energy (13.61kWh/kg DMC) resulting in high investment and utility costs, thus making the process not profitable. The focus for new membrane reactors could be on the selective removal of DMC (instead of water) from the reaction area to allow for a more concentrated DMC stream.

The issue of reducing or removing phospholipids from total lipids of a microalgae and an oleaginous fungus for preparing biodiesel

ABSTRACTThis study is divided into three parts and examines recommendations made in the literature to remove or reduce phospholipids, a class of polar lipids, from microalgal and fungal lipids, so that transesterification of the neutral lipids with methanol improves the yield of fatty acid methyl esters (FAME) (biodiesel). Literature on the role of phospholipids lowering the yield of FAME during transesterification of vegetable oils is reviewed in the first part of this study. The second part of this study scrutinizes two published papers on the preparation and yield of FAME by transesterification of total lipids present in microalgae of Chlorella pyrenoidosa (CP) and oleaginous fungus Mucor circinelloides (MC) with or without biomass in different solvent systems. Mole balance between acyl groups present in total lipids of CP and MC with methanol in part 3 makes it possible to use the results reviewed in part 1 of reduction in the yield of FAME in vegetable oils due to phospholipids and excess methanol. In conclusion, it is recommended to separate neutral lipids from polar lipids/phospholipids present in the total lipids of microalgae and fungi by supercritical carbon dioxide to prepare FAME in improved yields and keep phosphorus content below the polluting limit in the biodiesel prepared.

Exploratory study on internal recycling of crude glycerol for biodiesel production: Catalyst replacement

The present study evaluated the recycling of crude glycerol as source of catalyst for biodiesel production. For that purpose, two sets of experiments were conducted. In the first set (A), biodiesel was synthesized by conventional methanolysis of sunflower oil using NaOH as catalyst at 65?C during 1 h and varying catalyst concentration (0.4 - 1.2 wt.%) or methanol to oil molar ratio (6:1-12:1). The second set (B) was performed by replicating the conditions of set A and considering the use of crude glycerol as source of catalyst. The evaluation of excess methanol and catalyst distribution in the crude products was performed. For both sets of experiments, product yield and quality (viscosity and purity) were determined. Methanol was predominantly in the glycerol phase (54 - 68%), with negligible effect of variation in catalyst concentration and higher percentages found when higher methanol to oil molar ratios were used, due to a higher polarity of this phase. In most cases, catalyst was predominantly in the crude glycerol (53 wt.% in average) and no clear relation was found between catalyst distribution and the different reaction conditions studied. The results from set A showed a clear influence of catalyst concentration in biodiesel conversion and a minor effect of methanol to oil molar ratio. The best conditions were 6:1 methanol to oil molar ratio and 0.6 wt.% of catalyst leading to a product yield of 95.1 wt.%, a purity of 99.3% and a viscosity of 4.59 mm2s-1. The second set of experiments showed different trends and variability compared to the first one and the results indicated that catalyst might be altered during glycerol storage. It was found an effect of methanol to oil molar ratio in reaction conversion with the highest purity (96.9 wt.%) being obtained when the highest molar ratio was used (12:1) possibly due to the reduced mass transfer limitations. Overall, the results clearly show the potential of using crude glycerol as source of catalyst, avoiding the use of new catalyst and allowing a more sustainable biodiesel production.

KOH-알코올 용액의 탄산화를 통한 이산화탄소 포집 및 탄산염 합성

This work investigates the carbonation of KOH-dissolved methanol and ethanol solution systems carried out for fixation. Potassium methyl carbonate (PMC) and potassium ethyl carbonate (PEC) were synthesized during the reaction in each solution as the solid powder, and they were characterized in detail. The amount of chemically absorbed to produce the PMC and PEC precipitates were calculated to be 97.90% and 99.58% of their theoretical values, respectively. In addition, a substantial amount of was physically absorbed in the solution during the carbonation. PMC precipitates were consisted of the pure PMC and with the weight ratio of 5:5, respectively. PEC precipitates were also mixture of the pure PEC and with the weight ratio of 8:2, respectively. When these two precipitates were dissolved in excess water, methanol and ethanol were regenerated remaining solid in the solutions. Therefore, the process has the potential to be one of the efficient options of CCS and CCU technologies.

Enzymatic pretreatment of low-grade oils for biodiesel production.

The alkaline process for making biodiesel (fatty acid methyl esters, or FAME) is highly efficient at the transesterification of glycerides. However, its performance is poor when it comes to using oil that contain significant amounts of free fatty acids (FFA). The traditional approach to such feedstocks is to employ acid catalysis, which is slow and requires a large excess of methanol, or to evaporate FFA and convert that in a separate process. An attractive option would be to convert the FFA in oil feedstocks to FAME, before introducing it into the alkaline process. The high selectivity of enzyme catalysis makes it a suitable basis for such a pretreatment process. In this work, we present a characterization of the pretreatment of high-FFA rapeseed oil using immobilized Candida antarctica lipase B (Novozym 435), focused on the impact of initial FFA and methanol concentration. Based on experimental results, we have identified limitations for the process in terms of FFA concentration in the feedstock and make suggestions for process operation. It was found that, using 5% catalyst and 4% methanol at 35°C, the FFA concentration could be reduced to 0.5% within an hour for feedstock containing up to 15% FFA. Further, the reaction was observed to be under kinetic control, in that the biocatalyst converts FFA (and FAME) at a much higher rate than glyceride substrates. There is thus, both a minimum and a maximum reaction time for the process to achieve the desired concentration of FFA. Finally, an assessment of process stability in a continuous packed bed system indicates that as much as 15 m(3) oil could potentially be pretreated by 1 kg of biocatalyst at the given process conditions.

Synthesis and characterization of switchable ionic compound based on DBU, CH3OH, and CO2

Switchable ionic compounds have wide applications in chemical processes. A switchable ionic compound based on 1,8-diazabicyclo-[5.4.0]-undec-7-ene (DBU), CH3OH and CO2 was synthesized and characterized. DBU/CH3OH/CO2 ionic compound was prepared in the presence of excess methanol, and then the excess methanol was removed by reduced pressure distillation in CO2 atmosphere. The product yield (100%) reached the theoretical maximum for the first time. Its structure was identified by NMR, FT-IR, and XRD. The crystal product shows 8 strong peaks in XRD at 2θ values of 16.0547°, 16.4308°, 16.7651°, 18.8714°, 19.2140°, 21.9471°, 22.0780°, and 25.5661°. Its decomposition onset temperature (53°C) was affirmed by TGA, which is lower than its melting point. And its ionic switch point was measured by conductivity.

Preparation and characterization of aluminum oxide coated extracted silica from rice husk ash for monoglyceride removal in crude biodiesel production

In this study, aluminum oxide was coated on extracted silica from rice husks (AO_RHA). First, the silica was produced by heating the rice husk at 700 °C for 6 h following precipitation using NaOH and H2SO4 (RHA). The coating process was carried out using AlCl3 solution. The effect of stirring times, pH, and calcination conditions were investigated. The characterization of AO_RHA was performed using BET, XRD, FTIR, and ICP techniques. This study demonstrated the influence of the AO_RHA structure on monoglyceride removal. Langmuir and Freundlich adsorption isotherms were used to model the equilibrium isotherms and determine the isotherm constants. The adsorption capacity increased after the excess methanol was removed. In addition, the spent AO_RHA was regenerated and can be efficiently reused up to four times.

Estimation of kinetic parameters and diffusion coefficients for the transesterification of triolein with methanol on a solid ZnAl2O4 catalyst

The transesterification of vegetable oils by methanol implies a set of three parallel–series reversible reactions. Over a heterogeneous catalyst, reactions are limited by molecular diffusion, resulting in the use of a large excess of methanol to achieve a high conversion. This excess is detrimental to process efficiency because it involves large energy requirement for downstream separation. In order to identify the coupled physico-chemical phenomena and to optimize the process, a pilot unit was developed to perform transesterification of triglycerides with methanol over a solid ZnAl2O4 catalyst in a tubular fixed bed reactor under high pressure and temperature. The effects of different parameters such as particle diameter, temperature, residence time and molar feed ratio of methanol to triglyceride on fatty acid methyl ester (FAME) yield and triglyceride (TG) conversion were studied. A pseudo-homogeneous reactor model has been developed to identify rate laws and kinetic parameters by exploiting the experimental data in stationary regime. A set of kinetic constants was also determined for the given catalyst considering two kinetic models: an Eley–Rideal model with the reaction between TG and methanol as the rate determining step and a classical second order model taking into account thermodynamic equilibrium without adsorption. A heterogeneous model has also been established to determine molecular diffusion coefficients for each species in the mixture, through the use of experimental results in the transient regime. These molecular diffusion coefficients are dependent on the mixture viscosity and temperature. As a result, it was determined that diffusion of triglycerides and the first reaction kinetic rates are limiting the global conversion of the system.

One step cracking/transesterification of vegetable oil: Reaction–regeneration cycles in a capillary fluidized bed

CaO/Al2O3 catalytically transesterifies and cracks vegetable oils in the gas phase at temperatures beyond 400°C. The products are biodiesel (fatty acid methyl esters) and hydrocarbons. Oil conversion was complete with excess methanol in the feed. The gas residence time was less than 1s and the weight-hourly-space velocity in the capillary fluidized bed was on the order of 5h−1 (0.12mgmin−1 oil feed rate with 1.6g of catalyst). Periodic regeneration cycles with O2 converted the coke on the catalyst to CO and CO2. Regenerated catalyst is initially less selective towards biodiesel. Coke preserves the active sites that are selective for the conversion of the triglycerides into biodiesel. The biodiesel yield was highest (44%) dosing the catalyst with oil for 5min then regenerating it for 1min.

Nb2O5-catalyzed kinetics of fatty acids esterification for reactive distillation process simulation

On the basis of kinetic data obtained for the first time in the presence of pelletized niobium oxide as a catalyst, the esterification with methanol of single fatty acids or their mixtures has been simulated in a reactive distillation unit, which is a promising intensification technique in the frame of biodiesel synthesis. The kinetic behaviour of the reversible esterification of capric, lauric, myristic, palmitic, stearic and oleic acid at different temperatures was fitted through a pseudo-homogeneous reversible model suitable for the process design. The simulations showed that the reactivity of the acids and the acid composition of the feed affect both the column temperature profile and conversion, and that the benefit of a methanol excess is limited by the temperature decrease in the reactive section. The simulations also provided some preliminary design guidelines about the role of the main parameters, such as top reflux ratio, column pressure, feed temperature and number of stages, on the process performance.

ChemInform Abstract: Hydrogen‐Borrowing and Interrupted‐Hydrogen‐Borrowing Reactions of Ketones and Methanol Catalyzed by Iridium.

Abstract[IrCl(cod)]2 as the catalyst promotes hydrogen‐borrowing reaction of ketone enolates with methanol to give enones (III) which can react with excess methanol as nucleophile to yield mixtures of methoxymethyl derivatives (IV) and the enones (III).

A route to produce renewable diesel from algae: Synthesis and characterization of biodiesel via in situ transesterification of Chlorella alga and its catalytic deoxygenation to renewable diesel

Abstract In situ transesterification of Chlorella alga was performed using 5–20 wt% sulfuric acid as a catalyst at either 60 or 100 °C. The maximum ester yield in the range of 96–98% is comparative to the specification of ester content in biodiesel, 96%. A high excess of methanol was used in transesterification ensured also a high ester yield. The FAME was purified via adsorption of chlorophyll and carotenoids onto a clay. Properties of the purified biodiesel were investigated with several methods. The results showed that the Chlorella based biodiesel exhibits slightly lower oxidative and thermal stability compared to soybean based biodiesel due to the presence of polyunsaturated FAMEs. In addition to biodiesel, also the residual biomass was characterized showing that it contained sugars and proteins. An additional hydrogenation would increase the oxidative stability. Hydrodeoxygenation of Chlorella based biodiesel was also demonstrated over 5 wt% Ni–HY-80 zeolite with SiO2/Al2O3 ratio of 80 and with 5 wt% Pd/C at 300 °C and 30 bar in dodecane as a solvent. Ni–HY-80 was superior to Pd/C catalyst giving more than 95% yield of hydrocarbons.

Ultrasound intensification suppresses the need of methanol excess during the biodiesel production with Lipozyme TL-IM

The synthesis of biodiesel from sunflower oil and methanol based on transesterification using the immobilized lipase from Thermomyces lanuginosus (Lipozyme TL-IM) has been investigated under silent conditions and under an ultrasound field. Ultrasound assisted process led to reduced processing time and requirement of lower enzyme dosage. We found for the first time that oil to methanol ratio of 1:3 was favored for the ultrasound assisted enzymatic process which is lower than that observed for the case of conventional stirring based approach (ratio of 1.4). Our results indicate that intensification provided by ultrasound suppresses the need of the excess of the methanol reactant during the enzymatic biodiesel production. Ultrasound assisted enzymatic biodiesel production is therefore a faster and a cleaner processes.

Effect of oxomolybdate species dispersion on direct methanol oxidation to dimethoxymethane over MoOx/TiO2 catalysts

AbstractThe one‐step selective oxidation of methanol to dimethoxymethane (DMM) was demonstrated over titania‐supported molybdenum oxide catalysts, containing different amounts of molybdenum and prepared using two different impregnation techniques, namely wet impregnation and incipient wetness impregnation. The corresponding catalysts exhibited both acidic and redox properties, which are necessary for the oxidation of methanol to formaldehyde with subsequent condensation of the latter with excess methanol to finally yield DMM. The formation of well‐dispersed polyoxomolybdate species on the catalyst surface was evidenced using IR‐Raman, X‐ray diffraction, and nitrogen physisorption. Varying the amount of these polyoxomolydate species was associated with a modulation of the acidic and redox properties, as shown by NH3‐TPD and H2‐TPR. With respect to the catalytic performances, the best balance between acid and redox properties was observed over the samples containing 8 wt.% Mo, which corresponds to a theoretical MoOx species coverage close to a monolayer.

Energy saving in a biodiesel production process based on self-heat recuperation technology

Acid-catalyzed biodiesel production processes offer a competitive alternative for biodiesel production using waste cooking oil as raw materials and are less complex than alkali-catalyzed approaches. However, acid-catalyzed biodiesel processes are not yet commercialized because of high energy requirements, especially for the recovery of excess methanol and purification of the biodiesel and glycerol. We have developed an advanced biodiesel production process with energy savings through application of self-heat recuperation technology for methanol recovery and biodiesel and glycerol purification. Both the sensible and latent waste heat were recirculated within the proposed process, significantly reducing energy requirements. Simulation showed that the total energy requirement of the proposed process was 378.7kWh per ton biodiesel, some 71% lower than that of the conventional biodiesel production process.

Transesterification of hazelnut oil by ultrasonic irradiation

ABSTRACTUltrasonic irradiation is considered an effective way to increase mass transfer between immiscible liquid–liquid phases in a heterogeneous system leading to faster transesterification and higher yield and saving excess methanol and catalyst. In this study, the transesterification of hazelnut oil with methanol and ethanol was performed in the presence of potassium hydroxide or sodium methoxide as a catalyst using two types of ultrasonic irradiation with a probe (20 kHz, 200 W) and a bath (35 kHz, 400 W); a conventional production method was also used. The reaction time, alcohol:oil molar ratio, catalyst type (KOH or NaOCH3), and catalyst amount (wt.% of oil) were studied as experimental parameters. The highest methyl ester conversion was obtained as 98.12% by using ultrasonic probe at a 5:1 methanol:oil molar ratio with KOH 1 wt.% of oil as catalyst in 20-min reaction time at autogenous temperature. The application of ultrasonic irradiation by using a probe decreased the level of energy consumption, showing that this method may be a promising alternative compared with the conventional production method.

Extraction of free fatty acids from wet Nannochloropsis gaditana biomass for biodiesel production

The objective of this work is to develop a process for producing biodiesel from the saponifiable lipid (SL) fraction of the wet microalgal biomass Nannochloropsis gaditana. The method consists of five steps. Firstly, crude fatty acid salt extraction was carried out using a KOH-ethanol (96%) solution, which allows one to extract the SLs as potassium salts. This transformation permits better separation of the unsaponifiable lipids (the second step) and finally produces purer biodiesel. The unsaponifiable lipids were then separated with hexane, after establishing the ethanol-water solution water content at 30% w/w. Some unsaponifiable lipids (carotenoids and phytosterols) are products of interest that might be purified from this fraction thus helping to improve the process's profitability. Thirdly, free fatty acids (FFAs) were purified by acidification of the ethanol-water solution to pH 5 and were then extracted with hexane. Fourthly, the FFAs were transformed to biodiesel by esterification with excess of methanol catalyzed using sulphuric acid, removing the excess by washing with hot water. Under these conditions the biodiesel purity and yield were 74.8% and 82% w/w, respectively. Finally, the biodiesel was clarified/purified up to 96.5% purity by adsorption with bentonite. The final biodiesel yield was 80.9%.

Organocatalytic Michael addition-lactonisation of carboxylic acids using α,β-unsaturated trichloromethyl ketones as α,β-unsaturated ester equivalents.

Isothiourea HBTM-2.1 catalyses the Michael addition-lactonisation of 2-aryl and 2-alkenylacetic acids and α,β-unsaturated trichloromethyl ketones. Ring-opening of the resulting dihydropyranones and subsequent alcoholysis of the CCl3 ketone with an excess of methanol gives a range of diesters in high diastereo- and enantioselectivity (up to 95 : 5 dr and >99% ee). Sequential addition of two different nucleophiles to a dihydropyranone gives the corresponding differentially substituted diacid derivative.