Continuous Removal Of Water Research Articles

Versatile Selective α-Carboxylic Acid Esterification of N-Protected Amino Acids and Peptides by Alcalase

Under continuous removal of water, the industrial protease Alcalase allows selective synthesis of α-carboxylic acid methyl, ethyl, benzyl, allyl, 2-(trimethylsilyl)ethyl, and tert-butyl esters of amino acids and peptides under mild conditions in very high yields. The purified yields range from 72% to 92%.

Aluminum-rich zeolite beta incorporated sodium alginate mixed matrix membranes for pervaporation dehydration and esterification of ethanol and acetic acid

Mixed matrix membranes of sodium alginate (NaAlg) were prepared by solution casting by incorporating 2.5, 5, 7.5 and 10 wt.% of zeolite beta particles. The membranes thus prepared were crosslinked with glutaraldehyde and tested for the pervaporation (PV) dehydration of ethanol and acetic acid at 30–60 °C. The aluminum-rich zeolite beta, with its hydrophilic nature as well as molecular sieving effect and its favorable interaction with hydrophilic NaAlg, was responsible to enhance the PV dehydration of acetic acid and ethanol in terms of separation factor, flux, pervaporation separation index (PSI) and enrichment factor ( β). Thermodynamic model for sorption process was investigated typically for water + ethanol mixtures based on Flory–Huggins theory to explain the PV performance. Based on these results, permeance and driving force mechanisms were also elucidated. Extraction or dissolution of zeolite beta from mixed matrix membranes is confirmed by equilibrium sorption. Additionally, the changes in the dimension of pristine and mixed matrix membranes are compared to provide the influence of swelling on the stabilities of mixed matrix membranes. Arrhenius parameters for the process of permeation were calculated using these data at different temperatures to investigate their effects on the nature of the mixed matrix membrane. The plots of ln J p vs. 1/ T were constructed and found to follow the linear trends in the studied range of 30–60 °C for both the feed mixtures, indicating that flux followed the Arrhenius trend. PV experiments were also carried out for 5 and 10 wt.% incorporated NaAlg mixed matrix membranes at 70 °C to verify the suitability of the membranes at the esterification temperature. PV-aided catalytic esterification of acetic acid with ethanol was studied at 70 °C, which led to a considerable increase in ethyl acetate conversion with a reduction in reaction time as compared to the blank reaction due to continuous removal of water permeating through the barrier membrane.

A Systematic Approach to Predicting Liquid Loading in Gas Wells

Summary Loading up of liquids in wellbore has been recognized as one of the severe problems in gas production for many years. Accurate prediction of the problem is vitally important for taking timely measures to solve the problem. Although previous investigators have suggested several methods to predict the problem, results from these methods often show discrepancies. Also, these methods are not easy to use because of the difficulties with prediction of bottomhole pressure in multiphase flow. An accurate and easy-to-use method is highly desirable. This paper fills the gap. Starting from Turner's analysis for prediction of the minimum gas velocity for liquid removal, the minimum kinetic energy of gas that is required to lift liquid droplets was determined in this study. In order to compare gas kinetic energy with the minimum required kinetic energy, a four-phase (gas, oil, water, and solid particles) flow model was developed for mist flow. Applying the minimum kinetic energy criterion to the four-phase flow model resulted in a closed-form analytical equation for predicting the minimum gas-flow rate. The kinetic energy theory indicates that the controlling conditions for liquid drop removal in gas wells are bottomhole conditions rather than tophole conditions. Our case studies show that Turner's method with 20% adjustment still underestimates the minimum gas velocity for liquid removal, and the newly developed equation is more accurate than Turner's method. The new method is easier to use than other existing methods. This paper provides production engineers with a systematic approach to predicting the minimum gas-production rate for the continuous removal of water and oil from gas wells. Engineering charts are provided for two typical tubing sizes and wellhead pressures.

Synthesis and characterization of 3- and 4-phenylgermatranes: X-ray crystal structures of N(CH 2CH 2O) 2(CH 2CHPhO)GeZ (Z=F, OSiMe 3, CCPh) and N(CH 2CH 2O) 2(CHPhCH 2O)GeOH

Reaction of excess of product A [(HOCH 2CH 2) 2NCH 2CH(Ph)OH ( 1):(HOCH 2CH 2) 2NCH(Ph)CH 2OH ( 2)=9:1] with GeCl 4 led to a mixture of 1-chloro-3-phenylgermatrane ( 3) and 1-chloro-4-phenylgermatrane ( 4). Compound 4 was isolated in yield 9% from this mixture. Reaction of (EtO) 3GeCl with product A gave 3 in yield 55%. 1-(Phenylethynyl)-3-phenylgermatrane ( 5) was prepared in yield 31% by treatment of (EtO) 3GeCCPh with product A. Reaction of product A with mixture of GeO 2 and H 2O produced N(CH 2CH 2O) 2(CH 2CHPhO)GeOH ( 6) in yield 73%. The presence of N(CH 2CH 2O) 2(CHPhCH 2O)GeOH ( 7) among the products of this reaction was confirmed by 1H-, 13C-NMR spectroscopy and X-ray analysis. N(CH 2CH 2O) 2(CH 2CHPhO)GeF ( 8) is formed by the treatment of 6 with BF 3·Et 2O. N(CH 2CH 2O) 2(CH 2CHPhO)GeOSiMe 3 ( 9) was obtained by silylation of 6 with (Me 3Si) 2NH or Me 3SiCl–Et 3N. Refluxing of a suspension of 6 in xylene with continuous removal of water by azeotropic distillation afforded [N(CH 2CH 2O) 2(CH 2CHPhO)Ge] 2O ( 10). 9 reacted with SOCl 2, Me 3SiBr and Me 3SiOTf to give N(CH 2CH 2O) 2(CH 2CHPhO)GeX ( 3, X=Cl; 11, X=Br; 12, X=OTf), respectively. Reaction of 11 with Et 3SnOMe led to the formation of N(CH 2CH 2O) 2(CH 2CHPhO)GeOMe ( 13). Germatranes N(CH 2CH 2O) 2(CH 2CHPhO)GeY [ 14, Y=Flu (fluorenyl); 15, Y=N(SiMe 3) 2] were obtained from the nucleophilic substitution of the substituent X in N(CH 2CH 2O) 2(CH 2CHPhO)GeX (X=OSiMe 3, Br) with the corresponding LiY. All compounds were characterized by 1H- and 13C-NMR spectroscopy and mass spectrometry. Single-crystal structures of 5 and 7– 9 were determined by X-ray diffraction studies.

An easy-to-use heterogeneous catalyst for the Knoevenagel condensation

Physical mixtures of alkali and earth alkali metal carbonates and commercially available zeolites were investigated as solid catalysts for the Knoevenagel condensation. Best results for the model reaction between benzaldehyde and ethyl cyanoacetate were obtained for a 1:4 mixture of Na2CO3 with 4 Å molecular sieves (MS). The effects of the following parameters were investigated: structure of substrate, type and basicity of metal carbonate and zeolite, and temperature. Between 50 and 90°C chemical yields up to >90% were obtained without continuous removal of water and with reasonable catalyst activities and reaction times. Na2CO3 – MS 4 Å proved to be active for the condensation of several aldehydes and ketones with a variety of active methylene components.Key words: Knoevenagel condensation, solid basic catalysts, zeolite – sodium carbonate mixtures.

An easy-to-use heterogeneous catalyst for the Knoevenagel condensation

Physical mixtures of alkali and earth alkali metal carbonates and commercially available zeolites were investigated as solid catalysts for the Knoevenagel condensation. Best results for the model reaction between benzaldehyde and ethyl cyanoacetate were obtained for a 1:4 mixture of Na2CO3 with 4 Å molecular sieves (MS). The effects of the following parameters were investigated: structure of substrate, type and basicity of metal carbonate and zeolite, and temperature. Between 50 and 90°C chemical yields up to >90% were obtained without continuous removal of water and with reasonable catalyst activities and reaction times. Na2CO3 – MS 4 Å proved to be active for the condensation of several aldehydes and ketones with a variety of active methylene components.Key words: Knoevenagel condensation, solid basic catalysts, zeolite – sodium carbonate mixtures.

Large-scale enzymatic production of natural flavour esters in organic solvent with continuous water removal

A new, large-scale process was developed for the enzymatic production of low molecular weight flavour esters in organic solvent. Solutions for the elimination of substrate and product inhibitions are presented. The excess water produced during the process was continuously removed by hetero-azeotropic distillation and esters were produced at yields of over 90%.

Synthesis of sugar fatty acid esters by modified lipase.

A simple synthesis of sugar fatty acid esters was developed in a nonaqueous solution using lipase modified by synthetic detergent. Esterification of sugar was accelerated by continuous removal of water from the reaction mixture with a molecular sieve. When glucose and palmitic acid (1:1 by mole) were used as the starting substrates, more than 90% of glucose was converted to its ester in this system. The resultant product was 6-O-palmitoylglucose. Other mono- or disaccharides were also esterified by the modified lipase with high yield. It was shown that the modified lipase might act as a catalyst for the synthesis of sugar fatty acid esters.

Synthesis of sugar fatty acid esters by modified lipase

A simple synthesis of sugar fatty acid esters was developed in a nonaqueous solution using lipase modified by synthetic detergent. Esterification of sugar was accelerated by continuous removal of water from the reaction mixture with a molecular sieve. When glucose and palmitic acid (1:1 by mole) were used as the starting substrates, more than 90% of glucose was converted to its ester in this system. The resultant product was 6-O-palmitoylglucose. Other mono- or disaccharides were also esterified by the modified lipase with high yield. It was shown that the modified lipase might act as a catalyst for the synthesis of sugar fatty acid esters. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 64: 267–271, 1999.

Lipase‐catalyzed enrichment of long‐chain polyunsaturated fatty acids

AbstractLipase hydrolysis was evaluated as a means of selectively enriching long‐chain ω3 fatty acids in fish oil. Several lipases were screened for their ability to enrich total ω‐3 acids or selectively enrich either docosahexaenoic acid (DHA) or eicosapentaenoic acid (EPA). The effect of enzyme concentration, degree of hydrolysis, and fatty acid composition of the feed oil was studied. Because the materials that were enriched in long‐chain ω3 acids were either partial glycerides or free fatty acids, enzymatic reesterification of these materials to triglycerides by lipase catalysis was also investigated. Hydrolysis of fish oil by eitherCandida rugosa orGeotrichum candidum lipases resulted in an increase in the content of total ω3 acids from about 30% in the feed oil to 45% in the partial glycerides. The lipase fromC. rugosa was effective in selectively enriching either DHA or EPA, resulting in a change of either the DHA/EPA ratio or the EPA/DHA ratio from approximately 1:1 to 5:1. Nonselective reesterification of free fatty acids or partial glycerides that contained ω3 fatty acids could be achieved at high efficiency (approximately 95% triglycerides in the product) by using immobilizedRhizomucor miehei lipase with continuous removal of water.

Enhanced Organic-Phase Enzymatic Esterification with Continuous Water Removal in a Controlled Air-Bleed Evacuated-Headspace Reactor

The yield of organic-phase enzymatic esterification reactions can be improved by continuous removal of product water. When water is the only volatile component of the reaction system, this can be accomplished by carrying out the reaction under a partial vacuum. The performance in such reaction systems can be further improved by employing a controlled leak of air into the headspace of the reactor. This improvement is achieved at a lower vacuum than would be required in an ideal evacuated reactor delivering the same performance. The theory of air-leak effects has been analyzed in this paper. Experiments done to verify this theory have also been presented. Air-bleed evacuated-headspace reactors (ABEHRs) can produce extremely high synthetic yields. For instance, during the lipozyme-catalyzed esterification of a solvent-free solketal−decanoic acid mixture, a yield of 96% ester was obtained in a reactor operated under a vacuum of 0.7 bar and a temperature of 50 °C when air at 20 °C with a relative humidity of 54% was leaked into the headspace.

Synthesis, Structure, Electronic Spectroscopy, Photophysics, Electrochemistry, and X-ray Photoelectron Spectroscopy of Highly-Electron-Deficient [5,10,15,20-Tetrakis(perfluoroalkyl)porphinato]zinc(II) Complexes and Their Free Base Derivatives

The synthesis, optical spectroscopy, photophysical properties, electrochemistry, and X-ray photoelectron spectroscopy of a series of [5,10,15,20-tetrakis(perfluoroalkyl)porphinato]zinc(II) complexes and their free base analogs are reported. The title compounds were prepared by a condensation methodology that utilizes perfluoro-1-(2‘-pyrrolyl)-1-alkanol precursors and employs continuous water removal throughout the course of the reaction to yield the meso perfluorocarbon-substituted porphyrins. The nature of the porphyrin-pendant meso-perfluoroalkyl group exerts considerable influence over the macrocycle's solubility properties. The structure of the monopyridyl adduct of [5,10,15,20-tetrakis(heptafluoropropyl)porphinato]zinc(II) features an S4-distorted porphyrin core; X-ray data are as follows: P1 with a = 15.1330(5) A, b = 19.2780(6) A, c = 14.6030(4) A, α = 110.220(2)°, β = 103.920(2)°, γ = 85.666(2)°, V= 3880.1(2) A3, dcalc = 1.887 g cm-3, and Z = 4. Electrochemical studies carried out on these porph...

Direct Reaction of Phosphorus Acids with Hydroxy of a Silanol and on the Silica Gel Surface

Several phosphorus acids (methyl- and phenylphosphonic, diphenylphosphinic, and ethyl phosphoric acids) were round to give inters on reaction with tert-butyldimethylsilanol. The reactions occurred simply on beating the reactants in an inert solvent (hexane or toluene). The reaction is reversible, and yields or inters were improved by continuous water removal. The dibasic acids gave either mono- or disilyl inters; the latter were more easily purified and characterized. The OH groups on the surface or silica gel were also round to react with various phosphorus acids under similar conditions to give surface-bonded esters. Products were characterized by CP/MAS 31 P and 28 Si NMR

Computational scheme for the calculation of molecular weight distributions for nylon 6 polymerization in homogeneous, continuous‐flow stirred‐tank reactors with continuous removal of water

AbstractAn efficient computational scheme has been established for obtaining the molecular‐weight distributions (MWDs) for Nylon 6 polymerization in homogeneous, continuous‐flow stirred‐tank reactors (HCSTRs) with water vaporization. A three‐step procedure is used: the moment equations are solved by a sequential application of Brown's algorithm, the moments so calculated are used to give an empirical Flory‐Schultz distribution and, finally, this empirical distribution is used as a starting guess in Brown's algorithm applied to species mass‐balance equations to give the exact MWD. The moment‐closure approximations normally used for hutch reactors have been found to work equally well with HCSTRs for residence times of industrial significance.

A Simple Method of Dithioacetal—and Ketalization

Abstract Dithioacetals and ketals are useful synthetic intermediates.1 In general, they are obtained by the acidcatalysed addition of thiol to carbonyl compounds.2 The reaction is however a reversible one, and an excess of thiol together with continuous removal of water are often required for optimum yield. Recently, it was reported3 that methylthiotrimethylsilane converted carbonyl compounds to dithioacetals and ketals. The reaction however can not be applied to other thiols.

Preparation of partial glycerides by direct esterification1

AbstractA previously described procedure for the direct esterification of diglycerides without interesterification occurring has been evaluated for the preparation of mono and diglycerides. The esterifications were accomplished withp‐toluenesulfonic acid catalyst and with continuous removal of water of esterification by azeotropic distillation. The effect of such variables as unsaturation, chain length, mode of addition of solvent and reaction temp on the composition and yield of glycerides was observed. Chemical and chromatographic analyses were used to determine the composition of the glycerides and their component fatty acids and to detect the presence of isomeric glycerides. Simple esterification of 1‐monostearin with oleic acid at 80C yielded as much as 72.3% diglycerides, and esterification of glycerol with stearic acid at 100C yielded up to 70.1% monoglycerides, each calculated on a glyceride basis. It is concluded that simple esterification predominates with some intra‐ and interesterification occurring.

PRODUCTION AND PROPERTIES OF 2,3-BUTANEDIOL: XXIII. CONDENSATION OF THE ISOMERIC 2,3-BUTANEDIOLS WITH ETHYL ACETOACETATE

levo-2,3-Butanediol will condense with ethyl acetoacetate in the presence of hydrochloric acid to give the ethyl ester of levo-2,4,5-trimethyl-2-carboxymethyl-1,3-dioxacyclopentane (I) (yield 48%) from which the free acid may be obtained. If p-toluenesulphonic acid is used as the catalyst and the condensation is carried out in boiling butanol with continuous removal of water, the butyl ester of (I) is obtained (yield 87%). Compounds described for the first time are levo-, dl-, and meso-2,4,5-trimethyl-2-carboxymethyl-1,3-dioxacyclopentanes, their n-butyl and p-bromophenacyl esters (melting points 74.5°, 76°, and 76 °C., respectively) and the ethyl ester of the levo-isomer.