| Dioctyl adipate is a good cold-resistant plasticizer of PVC. It has many advantages such as high plasticizing efficiency, low toxicity, good biodegradability, even can make products with good flexibility and light resistance in low temperature, and so on. With the expanding range of applications of PVC and increasing development of the plastic processing technology, the study on the synthesis of dioctyl adipate, whether it is for the production of plastic industry or industrial processing industry, is very important. However, in the past, people often use liquid acid catalysts, with mainly concentrated sulfuric acid, to catalyze the synthesis of dioctyl adipate. In order to develop a highly-efficient and environmentally-friendly catalysis process for this esterification, some solid acids instead of liquid acids to catalyze the synthesis of dioctyl adipate was studied in this paper and the obtained results are described as follows:1.HY zeolite catalyst was prepared by exchange and then calcination of NaY raw powder. The catalytic performance of HY, super-stable rare earth Y, and β zeolites was checked on the esterification of adipic acid and2-ethylhexanol. The results showed that these zeolites for the esterification reaction possessed good catalytic activity, and HY zeolite was the best. In using HY zeolite to catalyze the synthesis of dioctyl adipate, various reaction parameters such as reaction temperature and time, molar ratio of acid to alcohol, the amount of catalyst and toluene as a water carrying agent were checked in details. Under the optimum reaction conditions, HY catalyst gave98.7%of esterification yield and an excellent stability, which could be reused more than seven times without any loss of activity. But a relative high reaction temperature (160℃) and catalyst amount (1.0g), as well as a trouble regeneration of catalyst hampered its application.2.A chlorine-containing D-72type sulfonic acid resin and chlorine-free ordinary sulfonic acid resin were used as solid acid catalysts for synthesis of dioctyl adipate and the effect of various reaction parameters on this esterification was checked in details. The results indicated that two strong acidic cation exchange resins showed good catalytic activity. Under the optimum reaction conditions (catalyst,0.23g, mole ratio of acid to alcohol,1:2.5, reaction temperature and time,125℃and4h), both the resins could provide a higher than99%of dioctyl adipate yield with turnover frequency of10.85mol/(mol·h) for D-72resin and6.50mol/(mol·h)for ordinary resin. Moreover, both the resins possessed a good repeatability and could be recovered and reused for9times without significant loss of activity. Notably, D-72type sulfonic acid resin catalyst has better stability than ordinary resin, which was likely due to the stable effect of its Cl substituents on SO3H groups. But the esterification efficiency of D-72and especially ordinary resins is still improved.3.Using bamboo powder as material, a series of biomass char sulfonic acid were prepared through partial carbonization and then sulfonation and characterized by means of FTIR and TG. And their catalytic performance for the esterification of adipic acid and2-ethylhexanol was studied in details. These solid char sulfonic acids were found to show by far higher catalysis efficiency than the resin sulfonic acids aforementioned, providing a TOF of85.54mol/(mol·h). However, they possessed a poor repeatability, which should be due to the serious leaching of their sulfonic acid groups during the reaction. In order to improve the stability of bamboo charcoal sulfonic acid materials, we tried to introduce Si or chlorine element into bamboo charcoal structure. The initial results showed that both modifications had certain effect on the improved stability of bamboo charcoal sulfonic acid, but both modified mehods remain to be studied deeply. |
PDF Full Text Request