The catalytic properties of zeolites НY, НBeta, and НZSM-12 and of mesoporous amorphous aluminosilicate in liquid-phase esterifi cation of aliphatic (monobasic С 1 -С 18 , dibasic С 6 , С 10 ) and aromatic (benzoic, trimellitic, phthalic) carboxylic acids with butanol were studied. Zeolite HBeta appeared to be the most active catalyst. Procedures were developed for preparing esters in the presence of zeolitic catalyst НBeta, ensuring 100% selectivity of ester formation at 90-98% conversion of the acid.Carboxylic acid esters are one of the most demanded classes of organic compounds. The fi elds of their application are very diverse: solvents, fruit essences, aromatizers, preservatives, components of lubricating oils and hydraulic fl uids, biodiesel, etc. [1][2][3][4]. In the total volume of production of polymer plasticizers, the share of esters is about 85%, and the total volume of their production exceeded 5 million tons annually [5].The majority of industrial procedures for ester synthesis consist in direct esterifi cation of carboxylic acids with alcohols at elevated temperature (100-200°С) in the presence of various catalysts. Traditional acid catalysts for esterifi cation are sulfuric, hydrochloric, phosphoric, benzenesulfonic, and p-toluenesulfonic acids. To remove them from the crude ester after the synthesis, it is necessary to perform neutralization with a base agent and a series of washings with water, which gives rise to a large amount of liquid wastes and to the product loss. The drawbacks of using mineral acids are possible tarring of organic compounds and formation of by-products as a result of alcohol dehydration. Furthermore, with sulfuric acid as catalyst, unsaturated compounds arising from side reactions undergo sulfonation, and sulfonic acid esters are formed.Progress in the development of modern esterifi cation technologies is associated with the replacement of mineral and organic acids by heterogeneous catalysts.The use of synthetic microporous aluminosilicates (zeolites) and mesoporous metallosilicates as catalysts of ester synthesis has been reported recently [6][7][8][9][10][11][12]. The majority of studies dealing with esterifi cation in the presence of zeolitic catalysts concern synthesis of acetic or phthalic acid esters. Preparation of esters of other mono-and dicarboxylic acids in the presence of zeolites has been studied insuffi ciently.This study was aimed at developing effi cient procedures for preparing butyl esters of various aliphatic and aromatic carboxylic acids, based on using microporous crystalline aluminosilicates (zeolites НY, НBeta, НZSM-12) and mesoporous amorphous aluminosilicates.
EXPERIMENTALZeolites of structural types FAU (Y), BEA (Beta), and MTW (ZSM-12) in the H form, and also mesoporous aluminosilicate (MAS) were studied as catalysts.The starting zeolite NaY (molar ratio SiO 2 /Al 2 O 3 М = 4.9) was prepared by the procedure described in [13]. The NaY decationization (replacement of Na + cations by Н + ) was performed from an NН 4 NО 3 solution in three steps wi...
