Screening of Amine for CO2 Capture Using COSMO-RS Model

The significant and rapid reduction of greenhouse gas emissions is recognized as necessary to mitigate the potential climate effects from global warming. The postcombustion capture (PCC) and storage of carbon dioxide (CO2) that produced from the use of fossil fuels for electricity generation and from contaminant presented in natural gas are a key technologies needed to achieve these reductions. The most mature technology for CO2 capture is reversible chemical absorption into an aqueous amine solution. Although, amine-based solvents became promising solvents in CO2 absorption process, the selection of appropriate amine for specific process is impossible without a prior screening. This work presents the screening technique to identify the potential amine for CO2 capture using COSMO-RS model. To achieve this target we investigated 57 tertiary amine based CO2 absorbents with different chemical structures. Screening procedures were carried out based on their CO2 absorption rate and loading amount. The screening starts with the optimization of the amine compound geometry using TURBOMOLE. Then, we proceed with the prediction of the basicity of every amine candidates using COSMO-RS. The basicity were then compared with experimental results to check the reliability of the prediction. The correlation between predicted basicity value and amine performance in absorbing CO2 was established. Several high performance amine absorbents for CO2 capture were recommended for future studies

Soluut-solvent vastasmõjude eksperimentaalne uurimine ja modelleerimine

Väitekirja elektrooniline versioon ei sisalda publikatsiooneEnamik praktilist tähtsust omavatest keemilistest protsessidest toimub vedelikes – mitte ainult tööstuslik süntees ja laborikeemia, vaid ka bioloogilised protsessid nagu rakkude hingamine toimuvad molekulaarsel tasemel keerulise koostisega lahustes. Neist protsessidest arusaamine ja molekulide käitumise ennustamine lahustes on tähtis arvukate uurimisvaldkondade jaoks, meditsiinist ja farmakoloogiast naftakeemiani. Kahjuks on ainete omaduste ennustamine vedelikes arvutuskeemia jaoks üks keerulisemaid ülesandeid. Käesolevas töös hinnati olemasolevate arvutusmetoodikate sobivust vesiniksideme tekke kirjeldamiseks orgaanilistes lahustites ning molekulide jaotuse kirjeldamiseks kahe vedeliku vahel (sisuliselt vedelik-vedelik ekstraktsiooni modelleerimiseks). Peamine kasutatud arvutusmeetod oli COSMO-RS (Conductor-like Screening Model for Real Solvents), valitud oma erakordse sobivuse tõttu kontsentreeritud ja mitmekomponendiliste lahuste omaduste ennustamiseks ja molekulaardisainiks. Töö käigus leiti, et vesiniksidemed neutraalsete molekulide vahel on kirjeldatavad suhteliselt hästi, kuid vaadeldud arvutusmetoodikad pole piisavalt täpsed negatiivselt laetud vesiniksidemega komplekside modelleerimiseks. Vedelik-vedelik ekstraktsiooni tulemuste ennustamine COSMO-RS meetodiga oli üldjuhul edukas. Saadud tulemustele (nii lõpp- kui vahepealsetele parameetritele) saadi täpsuse hinanngud. Peale selle arendati uus metodoloogia tundmatute ühendite jaotuse ennustamiseks kahe mitteseguneva vedeliku vahel ilma vajaduseta ühendeid identifitseerida. See lihtsustab parima lahusti valikut ainete isoleerimiseks või puhastamiseks, vähendades töö- ja kemikaalide kulu ning jäätmete kogust.The majority of practically relevant chemical processes occur in liquids. Those are not limited to industrial synthesis and laboratory chemistry – biological processes such as cellular respiration on molecular level take place in complex solutions. Understanding and being able to predict the behaviour of molecules in solutions is essential for numerous branches of science, ranging from medicine and pharmacology to petroleum chemistry. However, predicting the behavior of chemical compounds in liquids, especially in many-component solutions, is one of the most challenging tasks for computational chemistry. In this work existing computational methodologies were tested for suitability for describing hydrogen bond formation in organic solvents and distribution of organic compounds between liquids (essentially modeling of liquid-liquid extraction). The main computational method in this work is COSMO-RS (Conductor-like Screening Model for Real Solvents), chosen for its unequalled ability to predict properties of concentrated and multicomponent solutions and usability in molecular design. It was found that properties of hydrogen bonds between uncharged molecules can be predicted relatively well, but the tested computational approaches were not accurate enough for description of hydrogen bonds involving negatively charged ions. Modeling of liquid-liquid extraction using COSMO-RS was generally successful. Accuracy of the predictions and intermediate parameters was evaluated and problematic cases identified and discussed. Also, a new methodology was developed for predicting the distribution of unknown compounds between immiscible solutions without need for compound identification. It allows simplifying the solvent selection for compound isolation or purification, reducing the workload, expenses and waste amount

Basicities of Strong Bases in Water: A Computational Study

Aqueous pKa values of strong organic bases – DBU, TBD, MTBD, different phosphazene bases, etc – were computed with CPCM, SMD and COSMO-RS approaches. Explicit solvent molecules were not used. Direct computations and computations with reference pKa values were used. The latter were of two types: (1) reliable experimental aqueous pKa value of a reference base with structure similar to the investigated base or (2) reliable experimental pKa value in acetonitrile of the investigated base itself. The correlations of experimental and computational values demonstrate that direct computations do not yield pKa predictions with useful accuracy: mean unsigned errors (MUE) of several pKa units were observed. Computations with reference bases lead to MUE below 1 pKa unit and are useful for predictions. Recommended aqueous pKa values are proposed for all investigated bases taking into account all available information: experimental pKa values in acetonitrile and water (if available), computational pKa values, common chemical knowledge

Happelisus ja aluselisus mittevesikeskkondades: solvendi omaduste ja puhtuse mõju

Väitekirja elektrooniline versioon ei sisalda publikatsioone.Käesolev töö koosneb kahest peamisest osast. Esimeses uuritakse kahe komplekti katalüütiliselt aktiivsete ainete happelis-aluselisi omadusi, mis toovad ilmekalt välja vajaduse teada täpselt kasutatava keskkonna omadusi. Fosfoonhapetel ja nende estritel põhinevate ainete juures leitakse sellest tulenevalt olulised vead kirjanduses avaldatud väärtustes, nende vigade tekkeallikaid uuritakse ja erinevused seletatakse. Triarüülfosfaanide pKa väärtuste mõõtmine toob välja atsetonitriili kui solvendi piirangud ja viib alternatiivse solvendi, 1,2-dikloroetaani, paralleelse kasutamiseni. Väitekirja teises osas kvantiseeritakse süstemaatiliste mõõtmiste abil vee, kui kõige levinuma lisandi, mõju hape-alus tasakaaludele madalate kontsentratsioonide piirkonnas atsetonitriilis. Näidatakse, et happed on madalatest veesisaldustest rohkem mõjutatud kui alused. Samuti kvantiseeritakse veesisalduse mõju sõltuvus ainete happelis-aluseliste omaduste tugevusest, happelisuse/aluselisuse tsentrist ja laengu delokalisatsiooni määra ulatusest ioonses vormis.The thesis consist of two major sections. Firstly, pKa values of two sets of catalytically active compounds are measured. These experiments emphasize the need to know the properties of the solvent. Serious errors are revealed in case of compounds derived from phosphonic acids and their esters. These disparities are further investigated and explained in detail. Measurements with triarylphosphanes bring the need for 1,2-dichloroethane as a second solvent next to acetonitrile, due to the limits of the latter. Secondly, the influence of water, the most common impurity in non-aqueous solvents, is systematically investigated at low concentrations in acetonitrile. It is shown that acids are more influenced by the rising water content compared to bases. The effect is studied by changing the strength of the acid-base properties of the compounds, the nature of the acidity/basicity center as well as the charge delocalization in ionized species

Prediction of Vapor/Liquid Equilibrium Behavior from Quantum Mechanical Data

MOSCED (Modified Separation of Cohesive Energy Density) is a particularly attractive model for activity coefficients because it offers intuitive insights into how to tune solvent-solute interactions to achieve optimized formulations. Unfortunately, only 133 compounds have been characterized with the MOSCED method. Furthermore, there is no convenient method for extending MOSCED predictions to new compounds. The hypothesis of the present research is that the surface charge density of a molecule, once normalized over the molecule surface area, provided graphically by a σ-profile from density functional theory (DFT) computations, can be used to estimate the parameters used in the MOSCED model. DFT results are readily available for 1432 compounds through a public database at Virginia Tech, and further DFT computations for new compounds are relatively quick and simple due to minimal additional molecular properties. The predictive functions were regressed based on 4375 binary solution infinite dilution coefficients. The average logarithmic deviation for the predictive MOSCED model was 0.280 while using the original correlative model had a deviation of 0.106 compared to 0.183 for the UNIFAC model. Phase equilibrium predictions were also compared where various models were used for interpolating finite compositions. The average percent deviations of the pressure for the 39 binary systems tested were 17.39% for Wilson, 18.90% for NRTL, and 13.83% for SSCED

Screening of Amine for CO2 Capture Using COSMO-RS Model

The significant and rapid reduction of greenhouse gas emissions is recognized as necessary to mitigate the potential climate effects from global warming. The postcombustion capture (PCC) and storage of carbon dioxide (CO2) that produced from the use of fossil fuels for electricity generation and from contaminant presented in natural gas are a key technologies needed to achieve these reductions. The most mature technology for CO2 capture is reversible chemical absorption into an aqueous amine solution. Although, amine-based solvents became promising solvents in CO2 absorption process, the selection of appropriate amine for specific process is impossible without a prior screening. This work presents the screening technique to identify the potential amine for CO2 capture using COSMO-RS model. To achieve this target we investigated 57 tertiary amine based CO2 absorbents with different chemical structures. Screening procedures were carried out based on their CO2 absorption rate and loading amount. The screening starts with the optimization of the amine compound geometry using TURBOMOLE. Then, we proceed with the prediction of the basicity of every amine candidates using COSMO-RS. The basicity were then compared with experimental results to check the reliability of the prediction. The correlation between predicted basicity value and amine performance in absorbing CO2 was established. Several high performance amine absorbents for CO2 capture were recommended for future studies

Ionisatsiooni efektiivsus elektropihustusionisatsiooni allikas, seosed analüüdi füüsiko-keemiliste omadustega

Väitekirja elektrooniline versioon ei sisalda publikatsiooneVedelikkromatograafi-massispektromeetria (LC-MS) võimaldab tuvastada erinevates proovides väga erinevaid ühendeid ja on tõusnud praegusel ajal domineerivaks analüüsimeetodiks orgaaniliste ühendite madalate sisalduste määramisel. Selle süsteemi üks võtmekomponente on ioonallikas, mida kasutatakse LC-MS aparatuuri juures nende kahe liidesena. Elektropihustusionisatsiooni (ESI) ioonallikas on tänu sellele, et võimaldab ioniseerida ja analüüsida väga laia omaduste spektri ja massivahemikuga ühendeid üks enimkasutatavaid ioonallikaid massispektromeetrias. Vaatamata ESI populaarsusele, ei ole siiani päris selge, millised ühendite füsiko-keemilised omadused määravad aine ioniseerumise effektiivsuse ESI allikas. Nimelt, erinevad ühendid võivad anda sama kontsentratsiooni juures massispektris väga erineva intensiivsusega signaale. Käesoleva töö peamiseks eesmärgiks oli jõuda seosteni, mis määravad ühendi ionisatsiooni efektiivsuse ESI allikas lähtudes ühendi füsiko-keemilistest parameetritest. Selleks töötati välja metoodika analüüsimaks erinevaid ühendeid samadel tingimustel ESI massispektromeetriga. Selle tulemusena on loodud suhteliste ionisatsioonieffektiivsuste skaala (solvendisüsteemis 80% - atsetonitriili, 20% - 0.1% sipelghappe vesilahust), mis hetkel sisaldab 344 väga erinevate füsiko-keemiste omadustega ühendit. Kaasates kõiki analüüsitud ühendeid ja nende 11 parameetrit (aluselisus vees, atsetonitriilis ja gaasifaasis, osakese pindala, ruumala, molekulmass, dipoolmoment, polaarse pinna suurus, lipofiilsus/hüdrofoobsus, protoneerumistsenter ja laengu jaotumist iseloomustav parameeter) viidi läbi multilineaarne regressioonanalüüs (MLR) leidmaks peamised seosed mainitud parameetrite ning ühendi ionisatsioonieffektiivsuse vahel ESI allikas kasutatud tingimustel. Kuna kõigi analüüsitud ühendite jaoks ei ole eksperimentaalseid parameetrite väärtuseid, siis käesoleva töö raames arvutati puuduvad väärtused kõigile ühenditele ja kasutati neid MLR analüüsis. MLR analüüsi tulemusena joonistuvad selgelt välja seosed ühendi ionisatsioonieffektiivsuse (ESI allikas antud tingimustel) ning kolme füsiko-keemilise omaduse vahel: aluselisus (vesilahuses), molekuli/iooni suurus ja iooni lipofiilsus/hüdrofoobsus. Mida tugevamini väljendunud on ainel need kolm omadust, seda intensiivsemalt see ESI allikas ioone annab. Käesolev töö on suure olulisusega kõigile, kes töötavad LC-ESI-MS meetodiga.Liquid chromatography mass spectrometry (LC-MS) enables to identify various compounds from different samples and it is currently the dominant method for detecting organic compounds in low concentrations. Ion source is the interface between the LC and MS and is a key component of an LC-MS apparatus. One of the most widely applied ionization source in mass spectrometry is electrospray ionization source (ESI) due to its capability to ionize and analyse different compounds with wide span of parameters’ values. Despite of the commonness of ESI-MS the relationships between the ionization efficiency and compounds’ physico-chemical parameters have still not been fully elucidated. The signals in mass-spectrum of different compounds having the same concentration in the sample can vary strongly. The main purpose of this study was to analyse the relationships between ionisation efficiencies and physico-chemical properties of analytes and find out which physico-chemical parameters influence ionization efficiency the most. The ESI-MS method for analysing the ionization efficiencies of various compounds under the same experimental conditions and the scale of relative ionization efficiencies of 344 compounds with widely differing physico-chemical parameter values (in solvent system 80% - acetonitrile, 20% - 0.1%formic acid aqueous solution) was developed. Multilinear regression analysis involving all the analysed compounds and the 11 physico chemical parameters (basicity in acetonitrile, in water and gas phase basicity, the area and the volume of the particle, molecular mass, dipole moment, polar surface area, lipophilicity/hydrophobicity, protonation centre and the (de)localization of the charge on the surface of the particle) was used to determine the most relevant relations between ionization efficiencies and those parameters. Since the experimental data on some of those parameters is not available, the computational values were calculated for all the compounds and used in multilinear regression analysis when experimental values were not available. The results of MLR analysis enable concluding that three main descriptors of compound determine its ionization efficiency in ESI source under the used conditions: the basicity on aqueous solution, the size of the ion/molecule and the lipophilicity/hydrophobicity of the ion. The more strongly these mentioned parameters of compounds are expressed, the more intensive is ionization in ESI source. This study is expected to be significant to all chemists and researchers working with the LC-ESI-MS method.https://www.ester.ee/record=b544943

Predicting pK_a for proteins using COSMO-RS

We have used the COSMO-RS implicit solvation method to calculate the equilibrium constants, pKa, for deprotonation of the acidic residues of the ovomucoid inhibitor protein, OMTKY3. The root mean square error for comparison with experimental data is only 0.5 pH units and the maximum error 0.8 pH units. The results show that the accuracy of pKa prediction using COSMO-RS is as good for large biomolecules as it is for smaller inorganic and organic acids and that the method compares very well to previous pKa predictions of the OMTKY3 protein using Quantum Mechanics/Molecular Mechanics. Our approach works well for systems of about 1000 atoms or less, which makes it useful for small proteins as well as for investigating portions of larger proteins such as active sites in enzymes