
Dragomir Stoyanov VassilevTechnical University of Gabrovo · Mathematics, Informatics and Natural Sciences
Dragomir Stoyanov Vassilev
Vice Rector "Science & Scientific Research"
Ultrasonic synthesis of organic compounds, bio-plasticizers, bio-polymers, organic synthesis
About
84
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Introduction
Working on ultrasound synthesis of organic compounds - aliphatic esters and polyols, carbohydrate esters and others.
Technical university of Gabrovo - www.tugab.bg,
ORCID: https://orcid.org/0000-0003-0579-894X, https://www.scopus.com/authid/detail.uri?authorId=57127984800
Additional affiliations
January 2014 - February 2016
Education
October 2017 - July 2019
April 2014 - February 2016
February 2013 - February 2016
Publications
Publications (84)
The natural polysaccharides described in this study are some of the most widely used biopolymers with food, pharmaceutical, and medical applications. The fundamental understanding needed to fully utilize their potentialin in the food and pharmaceutical industries depends on the detailed study of these polysaccharide molecules. Polysaccharides such...
Comfrey (Symphylus officinale L.) has a long history of use as a medicinal plant. Modern randomized controlled trials have confirmed the effectiveness and safety of comfrey preparations for treating pain, inflammation, and swelling in muscles and joints, particularly in conditions like degenerative arthritis, acute back pain, and sports injuries, i...
Interest in sucrose esters which are surfactants and environmental products, attracts the attention of researchers and manufacturers, due to the fact that renewable, easily available raw materials are used for their production. Sucrose esters are non-toxic, biocompatible and biodegradable products that are widely used in food technology, cosmetics...
Research on the anthropogenic impacts on natural resources at the river basin scale and solutions for its modeling areessential parts of river basin management. To manage the data sets and information effectively, a unified andstandardized geodatabase is necessary, which should provide mechanisms for support the entering, storing, analyzing,and mod...
The purpose of the present study was to determinate the biologically active substance in 95% ethanol and subsequent water extracts from Bulgarian comfrey (Symphylus officinale L.) roots and to evaluate their antioxidant potential. The antioxidant activity was evaluated by several reliable methods such as DPPH-, ABTS-, FRAP-, CUPRAC-, ORAC and HORAC...
The variety of urban landscapes, especially of urban green spaces provide a wide range of human well-being opportunities, physical recreation, sport activities, and urban heat mitigation. Therefore, there are many studies applying remote sensing and GIS methods, which were related to the sustainable city development focused on the �green network�,...
Plasticizers are additives that increase the plasticity of polymers by increasing the flexibility of macromolecules. The selection of substances with a similar function is carried out in accordance with criteria that include requirements for non-toxicity, good miscibility, low migration ability, low volatility, etc. The plasticizers most used in pl...
One of the country's priority directions in the development and management of the water sector is related to the construction, reconstruction and modernization of wastewater treatment plants, which are a fundamental element for improving the quality of life in populated areas. In recent years, more than 170 urban waste water treatment plants (WTPs)...
Sustainable waste management and regulation programs are key to the proper functioning of any city. Old disposal methods are not suitable in Europe. This is a problem that will be left for generations to come. Insufficient resources and the constantly growing needs of the population require a balanced approach to solving economical, social and envi...
The sustainable use of the natural resources and the introduction of the principles of the circular economy are two trends that are particularly relevant in the context of the European efforts for sustainable economic growth. One of the ecologically promising approaches is the municipals's multiannual environmental action programs which sets the fr...
Esters are used in the industry. The rapid increase in demand for esters in the food, cosmetics and pharmaceutical industries makes it mandatory to find alternative ways of synthesis instead of low-yield, expensive, energy-intensive and prolonged reactions. The production process for the synthesis of esters is based on chemical esterification of fa...
Plasticizers are additives that increase the plasticity of polymers by increasing the flexibility of macromolecules. The selection of substances with a similar function is carried out in accordance with criteria that include requirements for non-toxicity, good miscibility, low migration ability, low volatility, etc. The plasticizers most used in pl...
The present study shows the results obtained in the ultrasonic synthesis of sucrose esters with lauric acid, the identification of products, and the study of their possible use as bio-additives with a plasticizing effect in the processing of plastics. Fourier transform infrared spectroscopy (FTIR) and NMR (1 H and 13 C NMR) were used to identify th...
The aim of this study is to demonstrate a simple and rapid "green" method for the ultrasound assisted synthesis of aliphatic esters of capric acid. The spectral characterization of esters was performed by IR and NMR spectroscopies. The impact of ultrasonic irradiation on the reaction in a comparison with the conventional method was analyzed based o...
The aim of the present study is to investigate the application of caprate aliphatic esters as co-plasticizers and biodegradable additives in polyvinyl chloride. i-Bu caprate was used in different proportions. The applicability of a mixture of esters as bio-plasticizers and bio-additives in polyvinyl chloride was studied. The influence of the ester...
Lactose octaacetate is a biodegradable surfactant with antimicrobial, cytotoxic, and antiviral properties. The aim of this study was to obtain lactose octaacetates by microwave irradiation and to apply them in a cosmetic gel. Lactose ester was synthesized by esterification of lactose with acetic anhydride for 10 min (yield 74 %) and degree of acety...
The article presents a review of research and modern engineering solutions based on "green technologies" �for the synthesis of esters. Significant advantages of the method of transesterification of methyl caprate �with sucrose, leading to esters with potential biological activity such �as antifungal and antimicrobial agents, are highlighted.
The aim of the present study is to measure the noise level at workplaces related to metal machining - turning and milling, assessing the risk to the health of exposed workers.
The aim of this study is to demonstrate a simple and rapid "green" method for the ultrasound assisted synthesis of aliphatic esters by reacting isoamyl esters with saturated (capric, lauric, palmitic) acids. The spectral characterization of esters was performed by IR and NMR spectroscopies. The impact of ultrasonic irradiation on the reaction in a...
The aim of the present study is to investigate the application of a mixture of carbohydrate esters as co-plasticizers and biodegradable additives in polyvinyl chloride. Sucrose palmitate and inulin acetate were used in different proportions. The applicability of a mixture of carbohydrate esters as bio-plasticizers and bio-additives in polyvinyl chl...
Sucrose esters of higher fatty acids were obtained by ultrasound. The resulting esters are used as bioadditives in the processing of polyvinyl chloride. The addition of sugar esters causes a significant change in the physicomechanical properties of the resulting plastics, showing a plasticizing effect.
Inulin from the taproots of Cichorium intybus L. was isolated using microwave-assisted solvent extraction and liquid-pressure methods for extraction, respectively. The physicochemical, spectral characteristics (IR-FT and NMR), and anticomplimentary activity of chicory inulin were studied. The resulting inulin was characterized by purity of 97%, DP...
Sucrose is used as a renewable raw material for the preparation of esters in various fields such as detergents, whitening boosters, cosmetics, medicines, nutritional supplements, emulsifiers, stabilizing agents, etc. By transes-terification of all hydroxyl groups with fatty acids, the polysubstituted sucrose esters acquire specific physical and org...
An environmentally friendly and sustainable ultrasound-assisted esterification of long-chained inulin and sucrose with monounsaturated 10-undecylenic acid was performed. The obtained esters were characterized by thin-layer chromatography (TLC), Fourier transforms infrared spectroscopy (FTIR), and nuclear magnetic resonance (NMR) spectroscopy. The s...
Esters are widely used in in-a-kind and are widely used in industry. The rapid increase in demand for esters in the food industry, cosmetics, pharmaceutical industry makes it imperative to find alternative ways of synthesis instead of reactions that have low yield, expensive, energy-intensive and long lasting. Also, long-chain esters of higher fatt...
The aim of this study is to demonstrate a simple and rapid "green" method for the ultrasound assisted synthesis of aliphatic esters by reacting isoamyl esters with saturated (capric, lauric, palmitic) acids. The spectral characterization of esters was performed by IR and NMR spectroscopies. The impact of ultrasonic irradiation on the reaction in a...
The increased consumption of resources and the increased requirements for environmental protection require the finding of alternative, more efficient, environmentally friendly methods for extraction and synthesis, as well as the reduction and recovery of industrial chemical waste. In chemical technologies, various methods and approaches are applied...
Undenicylic acid (10:1) is known as an antifungal agent and an active ingredient of many topical medicines [1-6]. The present research investigates the preparation of aliphatic esters of 10-undecylic acid with butanol and i-amyl alcohol by the conventional and ultrasound-assisted syntheses as well as the structural elucida-tion of the resulting com...
This study aims to demonstrate a simple and rapid "green" method for the ultrasound-assisted synthesis of t-aliphatic esters by reacting t-butanol with saturated (capric, lauric, palmitic) and unsaturated (oleic and undecylenic) acids. The spectral characterization of esters was performed by IR and NMR spectroscopies. The impact of ultrasonic irrad...
Microwave-assisted irradiation was performed for esterification of chicory
inulin with high degree of polymerization with acetic anhydride without a solvent
only with a catalyst. The resulting esters were characterized by melting point,
hydrophilic-lipophilic balance, thin-layer chromatography, ultraviolet spectroscopy,
Fourier transform infrared s...
A number of industrial technologies generate waste that creates a risk of environmental pollution. In this regard, research in recent years has focused on the search for new technological solutions for process intensification. For solution reactions, the use of ultrasound is effective. Ultrasound has been found to influence the rate of chemical rea...
Esters are widely used in a-kind and are widely used in industry. The rapid increase in demand for esters in the food, cosmetics, and pharmaceutical industries makes it imperative to find alternative ways of synthesis instead of reactions that have low yield, expensive, energy-intensive and long lasting. Also, long chain fatty acid esters are used...
The effects of cooking methods (steaming, pressure-cooking, microwaving, frying and boiling) on total phenolic contents of Morchella esculenta mushrooms were evaluated. The best cooking method was microwaving with losses up to 2%, and the worst – boiling with losses amounting to 50%. The results of the study provided some information on the effects...
Jerusalem artichoke (Helianthus tuberosus L.) tubers are industrial crop considered as a promising source for inulin production. "Green" method was performed for accelerated inulin extraction from Helianthus tuberosus L. tubers by the application of microwave irradiation. Further pretreatment of the water extract with acetone and ethanol yielded in...
The paper presents the findings of an experimental study on the microwave synthesis (MW) of inulin acetate and its possible application as bio-additive in poly(vinyl chloride) (PVC). The obtained inulin acetate has been identified and characterized by spectroscopic methods. Advantages of the MW compared with the conventional synthesis were defined....
The aim of the present work is to implement a model for separate collection and construction of a composting facility for bio-waste in Sevlievo municipality, for the production of high-quality compost, recycling of separately collected bio-waste.
As a result of the applied technology, after an external assessment of the quality of the compost, for...
Adverse impacts on nature should be reduced to a minimum or a solution that can completely eliminate the negative consequences and processes.
One of the solutions is to conduct environmental monitoring and its components for the identification of changes, changes and pollution, and to take measures and actions to solve the problems that have arise...
Undenicylic acid (10-) is known as an antifungal agent and an active ingredient of many topical drugs. The present research investigates the preparation of aliphatic esters of 10-undecylic acid with butanol and i-amyl alcohol by the conventional and ultrasound-assisted syntheses as well as the examination of the structure of the resulting compounds...
The aim of this study is to demonstrate a simple and rapid method for “green synthesis” of t-aliphatic esters by reacting t-butanol with saturated (capric, lauric, palmitic) and unsaturated (oleic and undecylenic) acids by ultrasound irradiation. Additional spectral characterization of esters was performed by IR and NMR spectroscopy. The impact of...
Sucrose octaacetate (octa-O-acetylsucrose) has been synthesized by esterification of sucrose with acetic anhydride using ultrasound-assisted irradiation. This sucrose ester is a white, water-insoluble substance with a bitter taste. The FT-IR and NMR spectra confirmed acetylation and revealed the hydrophobic incorporation in sucrose molecule. Furthe...
Plasticizers used in the treatment of polyvinyl chloride (PVC), which in most cases are esters of carboxylic acids with linear or branched aliphatic alcohols (phthalates, octanoates, etc.), possess excellent functional properties. However, they prove to be somewhat toxic. Therefore, they should be replaced with safer and more effective substances l...
Jerusalem artichoke (Helianthus tuberosus L.) tubers are industrial crop considered as promising source for inulin production. Green method was performed for accelerated extraction of inulin from Helianthus tuberosus L. tubers by application of microwave irradiation. Further pretreatment of extract with acetone and ethanol yielded inulin (10 %), wi...
Inulin esters were synthesized by transesterification reaction with methyl esters of three fatty acids (10-undecylenic, lauric and palmitic) under ultrasonic irradiation. The obtained esters were characterized by TLC and IR-FT spectroscopy. These inulin esters were examined for potential antimicrobial properties. The results from antibacterial assa...
The paper presents results obtained by experimental study of polyvinyl chloride (PVC) films containing sucrose
palmitate as bio-plasticizer. Influence of the plasticizer’s concentration on morphology and tensile properties of the polymer has been investigated in order to prove its plasticizing effect. It has been established a specific nonhomogeneo...
The paper presents the development methodology and the results from the interactive learning courses for " compensation e-learning " in Chemistry, Mathematics and Informatics in Technical university of Gabrovo. Survey was carried out among regular and part-time freshmen, in order to evaluate their learning experience with these courses. The survey...
The PhD thesis has investigated the application of ultrasonic irradiation in the esterification of alcohols - i-propanol, n-, i- and t-butanol with capric, lauric, palmitic, and 10-undecylenic acid. The resulting esters were identified by thin-layer and gas chromatography and characterized by NMR and IR spectroscopy. The applicability of sucroester...
This article presents the results obtained by the ultrasound-assisted synthesis of sucrose and fructooligosaccharides (FOS) esters with fatty acids (palmitic and 10-undecylenic), the identification of the products and the study of their possible application as plasticizers in plastics processing. Fourier transform infrared spectroscopy (FTIR) and n...
Pharmacologically interesting sucrose undecylenic acid esters were synthesized by transesterification reaction with methyl ester of 10-undecylenic acid under conventional conditions and ultrasonic irradiation. The effect of catalyst (NaOCH 3 and K 2 CO 3), molar ratio of reactant and temperature of esterification on the esters yield was studied. Th...
Plasticizers are substances which reduce the hardness and increase the plastic properties (elasticityand flexibility) of polymers. Carbohydrate esters and polyols ester have been successfully applied for this purposes to cellulose esters, PVC and Polylactide (PLA). An economic and efficient way to produce them could be ultrasonic synthesis ‐ signif...
Aim of this study is to identify risk factors and to assess the health status of workers in the public administration on the basis of data on morbidity with temporary disability. The subject is working in the field of Institution of Public Administration. Performance of MTD are rated as high to very high for the 2013-2014 period studied, the risk g...
Every year, millions of people in the EU are injured at work, or their health seriously harmed in the workplace. Therefore, the risk assessment is as important as it is the key to healthy workplaces. Risk assessment is a dynamic process that allows enterprises and organizations to implement proactive policy of managing workplace risks.
For these re...
Economic activity "collection, disposal and treatment of waste water" is especially risky in terms of working conditions. A significant proportion of workers in this activity are regularly exposed to humidity and low temperatures. Particularly significant and causing serious damage to the health of employees impact of materials that can cause infec...
One of the considerable disadvantages of Bulgarian educational system in the area of higher education is that it does not offer enough lifelong learning opportunities. In reply to the increasing need for more effective learning forms the Technical University of Gabrovo has developed sets of interactive learning materials designed for students follo...
Risk assessment is an important first step in the prevention of occupational accidents and diseases. OiRA, online interactive risk assessment facilitates this process. The project provides the resources and skills needed to enable micro and small enterprises to carry out their own risk assessment. Available free on the Internet, instruments OiRA ar...
The chemical processes consummated large amount of energy. In this connection, the current situation of
environmental degradation requires the development of efficient and environmentally friendly methods in terms of energy consumption and reduce waste. The synthesis of organic compounds by means of ultrasound is also economical and efficient metho...
One of the most reliable ways to destroy harmful compounds based on their catalytic oxidation involving catalysts for complete oxidation. Full oxidation of the organic matter is an irreversible process and therefore toxic substances using a suitable catalyst, are converted to innocuous products - CO2, and H2O. This article aims to preparation and c...
One of the most reliable and promising methods for the disposal of toxic compounds contained in effluents and gaseous emissions from various chemical industries based on heterogeneous catalytic reactions that can achieve complete oxidation of the substances. The purpose of this study development activity obtained nickel oxide systems for full heter...
Esters are widely used in in-a-kind and are widely used in industry. The rapid increase in demand for esters in the food industry, cosmetics, pharmaceutical industry makes it imperative to find alternative ways of synthesis instead of reactions that have low yield, expensive, energy-intensive and long lasting. Also, long-chain esters of higher fatt...
Biodiesel is an alternative to conventional diesel fuel, which is produced by a process of transesterification of vegetable oils derived from oilseed crops (especially rapeseed, soybean, sunflower, palm, etc.). Or used, as well as animal fat, or green algae.
Studies on transesterification of waste vegetable oil for biodiesel by ultrasound in Bulgar...
Subject of this review are electromagnetic waves generated by currents with low and high frequency. When we talk about the impact of such currents has to be understood not contact their action, and that of the consequences of such an electromagnetic field in space. In this paper the authors suggest an example of the application of the methodology t...
The aim of this work is to develop and implement exemplary methodology for assessing the labour risk from the effect of vibration - hand-arm andwhole body. The authors offer an example of applying the methodology developed in grindingpolished production.
In this work we will examine the risk assessment in the preparation of molds, because of the problem situation in a similar process and the large interest of workers and employers regarding health and safety. The remaining jobs are valued similarly in that methodology. For this purpose, selected a few workers whose jobs were done measuring the conc...
In this paper the authors propose an application of a methodology for assessing the effects of noise on human health. As a possible example of implementation of the proposed methodology for risk assessment chosepolished grinding process due to the constant noise levels associated with it.
The aim of this work is to propose a new approach for conducting risk assessment accompanying the work with chemicals. Proposed is a methodology that justifies the classification of chemical substances or mixtures thereof, under current legislation. The authors illustrate the proposed methodology with an example of widespread plastic production - t...
The Educational conception "Life long Learning"(LLL) opens opportunities in front of the particular person to live a dynamic and reasonable life, to develop a personal, professional carrier and good perspectives. The dynamics of the modern economy requires constant increase of the qualification of the people, acquiring new knowledge and skills in o...
Promoting Life Long Learning of scientific issues is much more difficult, if compared to other subject areas (e.g. humanistic subjects, business management, language learning) as when the compulsory educational path ends up, those that are not interested in science are much more likely to abandon completely the subject. Among the scientific fields,...
The correlation between the structure and the spectroscopic properties of N-methylcodeinium iodide (1) has been studied, using the methods of single crystal X-ray diffraction, IR-LD spectroscopy of oriented samples as a suspension in nematic liquid crystals, UV-vis spectroscopy and 1H and 13C NMR spectroscopy. HPLC tandem mass spectrometry (HPLC ES...
This Implementation Guidance has been developed to assist users in understanding the issues that need to be considered during the coexistence period between ISO 9001:2000 and ISO 9001:2008. While the changes between ISO 9001:2000 and ISO 9001:2008 are expected to have a limited impact on users, some arrangements regarding implementation are needed.
The correlation structure-spectroscopic properties of N-methylcodeinium iodide was studied, using methods of IR-LD spectroscopy of oriented as suspension in nematic liquid crystal. ISSN: 1313-230Х
This article presents a method of cold phosphatizing of metals. The authors were developed different composition for easier phosphatizing of metals.
This article presents example of Quality Function Deployment in high education.
This article presents model procedure for management teaching team for projects.
Article presents how to make risk assessment on the health and the safety of workers for handwork with weight.
This article gives an example steps about risk assessment of effects of chemicals on the health and the safety of workers in foundries. The authors prefer and use one of many known risk assessment methods.
This paper presents a short review of most widespread Management Systems. It gives information about the number of systems implemented in World, Europe and Bulgaria. It also gives the different ways for implementation of Managements Systems in Organizations.
This article presents a model of method for measurement of supplier. The authors offered methodology for evaluate a quality of suppliers.
The article present a method for constructing test papers and relevant ways of their application in progress check-ups for course in chemistry taught at the Technical university of Gabrovo.
The effect of the synthesis conditions of individual and modified with Mn Ni- and Co-oxide systems on the content and the
mobility of their active oxygen has been studied by means of chemical and IR spectral analyses. The results obtained show
that the main part of the active oxygen in Ni-oxide system is located on the catalyst’s surface (Os
* is a...
This article presents the methods of measurement the quality of teaching. In these paper is discussed the method " Pair compare ". The authors offered methodology for assessment of influence the human factor over quality of teaching. С приближаването на България към Европейския съюз все повече български фирми въвеждат различни системи за управление...
The Article presents the order of necessary stages for obtaining adequate assessment of client satisfaction measurement. The Article present an example procedure of client satisfaction measurement in correspondence to BDS EN ISO 9001:2001
The catalytic activity and selectivity of mixed NiCe oxide catalyst has been investigated in the liquid phase oxidation of phenol under mild conditions. The catalyst employed was prepared by oxidation-precipitation method at room temperature and was characterized by powder X-ray diffraction (XRD), IR-spectroscopy, and chemical analysis. The efficie...
A new method for the synthesis of benzoic acid based on the catalytic oxidation of benzyl alcohol with NaOCl using a higher Ni-oxide system as catalyst has been developed. The main advantage of the proposed method is that a benzoic acid of high purity and a yield of about 98 % could be obtained at mild reaction conditions.
These article present new elements from management system, standardization, certification, accreditation, notification, intellectual property, in relation a close bond between Bulgaria and EU. It could to be used from managers, engineers and teachers about improving their work. КЛЮЧОВИ ДУМИ: системи за управление, стандартизация, сертификация, акре...
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International Scientific Conference UNITECH`2024
The university head administration and conference program committee feel privileged to extend their invitation to you for participation in the 24th edition of the international scientific conference UNITECH, which will be held on 21th and 22nd of November 2024.
The first conference was held in 2001 and since then its prestige and influence have been affirmed by the participation of a large number of world renowned scholars and researchers from countries across the globe.
UNITECH is a scientific forum at which scientists from various fields get together to discuss and share their achievements and problems organized in 19 thematic sections. Since 2017 each of the submitted papers is reviewed by two independent reviewers.
Papers accepted with the highest grade are published in a free access on-line collection entitled “UNITECH – Selected Papers”, which is a possible candidate for referencing in world data bases of scientific information.
All ethical code rules related to freedom of speech, elimination of discrimination and encroachment upon the rights of authors and reviewers, observance and protection of copyrights and intellectual property and protection of personal details of users, are strictly adhered to.
UNITECH is held in an atmosphere of rapport and creative attitude. Participants have the unique opportunity to share their experience, expertise and knowledge with colleagues from other national and foreign universities and scientific organizations.