Существует постоянно растущий интерес к производству и использованию биовозобновляемых химических веществ в производстве полимерных материалов, предназначенных для получения детских игрушек, медицинского оборудования, находящихся в контакте с пищевыми продуктами. Тризамещенные эфиры лимонной кислоты-триалкилцитраты, получаемые этерификацией лимонной кислоты алифатическими спиртами C 2-C 5 , имеют 4 класс опасности, хорошую пластифицирующую способность, совместимость с полимером, высокую температуру вспышки. Лимонная кислота (объем мирового производства 0.85-1 млн. т/год) является доступным сырьем, получаемым из отходов сахарных производств. Цель исследования-разработка модели этерификации лимонной кислоты линейными спиртами С 2-С 5 на гомогенных кислотных катализаторах для создания отечественной технологии синтеза пластифицирующих композиций на основе возобновляемого сырья. Выбран катализатор-серная кислота; изучена связь реакционной способности алифатических спиртов С 2-С 5 с их строением в реакции этерификации лимонной кислоты, оценены некоторые кинетические параметры (lnk 0 , E акт), предложены режимы синтеза, рассчитано время реакции получения триалкилцитратов при конверсии лимонной кислоты 96% (t = 90 ºС). Наработаны лабораторные образцы и определены некоторые эксплуатационные характеристики.
The necessity and possibility of creating a domestic technology for the production of citric acid esters - trialkyl citrates - effective and environmentally friendly plasticizing compositions based on renewable raw materials are substantiated. Trialkylcitrates a purity of 98-99% are obtained by azeotropic esterification of citric acid with aliphatic alcohols C4-C5 under conditions of homogeneous acid catalysis. Using the synthesis of triamyl citrate as an example, the esterification of a polybasic hydroxy acid has been considered. It was established that during the synthesis a complex mixture is formed consisting of unreacted citric acid, incomplete mono-, diesters and triamyl citrate. The influence of synthesis conditions (temperature, reagent ratio, catalyst amount and reaction time) on the composition of the reaction mass is shown. A method of gas chromatographic analysis of citric acid esters has been developed. Taking into account the structural features of citric acid and its partial esters containing polar carboxyl groups, the reaction mass was pre-methylated with synthesized diazomethane. The resulting mixture consists of six esters of citric acid: trimethylcitrate; 2-hydroxy-1,3-dicarboxymethyl-2-carboxyamylpropane; 2-hydroxy-1,2-dicarboxymethyl-3-carboxyamil propane; 2-hydroxy-1-carboxymethyl-2,3-dicarboxysamyl propane; 2-hydroxy-2-carboxymethyl-1,3-dicarboxyamyl propane; triamylcitrate. The analysis was performed on a chromatographic complex "Crystal-2000M" on a capillary column with a grafted non-polar phase OV-101, length 100 m. The analysis time ranged from 22 to 49.5 min. Empirical equations were obtained using the internal standard method (the standard is dicyclohexyl adipate) to determine the calibration coefficients of the starting (trimethyl citrate т citric acid) and final (triamyl citrate) products in a wide concentration range. The results of identification of structures of six esters of citric acid for which there is no information in existing databases are presented. The study was carried out by method of chromato-mass spectrometry on the instrument SHIMADZU GCMS – QP2010 with ionization by electron impact at ionization energy of 130 eV. The analysis of the obtained spectra made it possible to determine the most probable ways of fragmentation of organic molecules and the intensity of the peaks of the ions formed.
Polyvinyl chloride (PVC) is a body of a great many of composite materials and takes one of the leading places in thermoplastic polymers production capacity. Annual intake of PVC in the world (data of 2014 years) achieves to 35 mtpa. and has a consistent trend to further increase. PVC recycling is impossible without using of plasticizers. Nowdays scopes of use and plasticizers market used in the polymer materials production intended for contact with alimentary products, for medical equipment and children's toys production, are upon essential impact of policy statements of health, safety, security, environment. Plasticizers with citric acid – trialkyl citrates have needed properties: hazard class 4, high plasticize ability, full miscibility with polymer, high boiling and flash points, low volatility. The citric acid is available renewable raw produced from saccharified residues; world production volume is 1.6 mtpa. There are no local plasticizers production technologies with citric acid. Development of plasticizers production technologies with renewable raw material is relevant objective. Purpose of research is to create method of producing of trialkyl citrate, study of esterification regularities of citric acid with low molecular alcohol over different catalysts. In this research, the kinetic of performances of citric acid esterification by pentanol was estimated over different catalysts. Reaction orders were defined using three catalysts: sulphuric acid, orthophosphoric acid and p-toluene sulphonic acid. The rate constants and activation energies of esterification were found. Kinetic formulas were obtained. The time of esterification was defined to achieve 95 % conversion of citric acid. The time varies from 1.5 to 5 h depending on used catalyst. For citation:Sushkova S.V., Levanova S.V., Glazko I.L., Pavlova K.V. Kinetic of esterification of citric acid in production of trialkyl citrates. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N2. P. 74-78.
The features of phenol alkylation by higher alpha-olefins to obtain monoalkylphenols (MAP) using commercial industrial samples of macroporous sulfocationites are considered: Tulsion-66 and Amberlist 36 dry, which are in different price categories and differ significantly in geometric dimensions: pore diameter at Tulsion-66 = 450-500 A; at Amberlist 36 dry =240 A; pore volume (cm3/g) 0.35 and 0.2, respectively. The thermodynamic analysis of a complex mixture of simultaneously occurring reversible reactions of the formation of target monoalkylphenols (the sum of ortho - and para - isomers) and by-products (dialkylphenols and alkylphenyl ether) in the range of 383-408 K was performed. It was found that to obtain 97-98% equilibrium monoalkylphenols yield, it is necessary to have a 4-6 fold molar excess of phenol with respect to olefins. It is not recommended to raise the temperature above 408 K, as this leads to a significant increase in by-products. In the course of kinetic studies, the optimal concentration of sulfocationites was established - 20% for the initial mixture, providing maximum rates for the selected samples under the same conditions while maintaining selectivity for the target monoalkylphenols at the level of 97-98%. Thus, at T=383 K, the phenol/olefin ratio =6: 1, the reaction rate on Tulsion-66 is 1.6-1.7 times higher than on Amberlist 36 dry. The activation energies estimated from experimental data in the studied temperature range had values (kJ/mol) : 14.64±1.89 on Tulsion-66 and 26.53±3.2 on Amberlist 36 dry. Differences in the reactivity of the investigated sulfocationites confirm the known theoretical positions, according to which the reaction rate during ion exchange catalysis depends on the ratio of the sizes of reacting molecules and catalyst pores.
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