Study On The Preparation Of Solid Superacid Catalysts And Catalytic Synthesis Of Tri-n-butyl Citrate

Tri-n-butyl citrate (TBC) is a new type of plasticizer. It is preferred green environmental protectionproduct has been proposed to replace phthalic acid esters plasticizer because of its many excellentcharacters. It is a kind of market prospects are very promising non-toxic plasticizer with the requirementincreasing. The number of citric acid production in our country is larger, exploiting and producting thecitric acid ester nontoxic plasticizer not only broadens the application field of citric acid, and provides anew nontoxic plasticizer in plastics and the oil industry, it has good economic value. The synthesistechnology of TBC mainly depends on the difference of the catalyst. Tri-n-butyl citrate (TBC) traditionalsynthesis process use the sulfuric acid as catalyst that corrosiveness to reactors and containers, and theserious problem of three wastes. Studies show that solid superacid catalyst instead of sulfuric acid, whichcan effectively overcome many defects of liquid acid. Exploit and research effective and green catalyst isthe current research hotspot and focus.With the increasing of human environmental consciousness, the application of environmental friendlysolid superacid catalyst is indispensable. Solid super acid catalyst for the advantages of high catalyticactivity and reusable, but most of these catalysts suffer from different defects, such as the decomposition ofsulfuric acid and sintering on the surface, and catalyst deactivation in the process of reaction, etc. Therefore,improve the activity and stability of catalyst and increase the total amount of acid is still an important andurgent task. In this work, various catalysts were prepared and modification, the preparation of catalyst canbe used to substitute for traditional sulfuric acid catalyst, effectively reduce the wear and tear of equipment,and the catalysts be used for the synthesis of Tri-n-butyl citrate, improve the quality of the product TBCand optimize TBC synthesis process, the catalyst has the good application value.The paper is divided intothree parts that are as follow:(1) With Fe2O3-ZrO2as the carrier, in order to improve the number of acid sites of solid super acid, weuse the S2O2-8as promoter, and the solid acid catalysts S22O-8/Fe2O3-ZrO2were prepared with theprecipitation-impregnation method, which modified by the La3+to improve the catalyst activity. Theinfluence of S2-2O8concentration, the mole ratio of metal atom, calcination temperature and La3+concentration on the catalysts structure were characterized by FT-IR, XRD, Raman spectroscopy, TG,NH3-TPD techniques, FT-IR of adsorbed pyridine and XPS. The catalytic activity was evaluated byobserving the esterification reaction for the synthesis TBC. The experimental results show that the additionof lanthanum enhance the activity and stability of catalyst.(2) With ZrO2-3+2-Al2O3as the carrier and the S2-2O8as promoter, we prepared the S2O8/ZrO2-Al2O3/Lasolid super acid catalyst loaded with La3+. The influence of S2-2O8concentration, the mole ratio of metaloxide, calcination temperature and La3+concentration on the catalysts structure were characterized byFT-IR, XRD, TG, NH3-TPD techniques and FT-IR of adsorbed pyridine. The catalytic activity wasevaluated by observing the esterification reaction for the synthesis TBC. The experimental results show thatthe addition of lanthanum enhance the activity and acidity of catalyst. (3) The solid acid catalysts S22O-8/ZrO2-SnO2loaded with La3+were prepared by theprecipitation-impregnation method with ZrO2-SnO2as the carrier and S22O-8as promoter. The effect ofLa3+content on the performance and structure of the catalysts was studied using the synthesis ofTri-n-butyl citrate. Catalysts structure characterized by FT-IR, XRD, Raman spectroscopy, TG, NH3-TPDtechniques, FT-IR of adsorbed pyridine. The results suggest that the specific surface area and acid strengthof catalyst greatly increased.(4) In this paper, we prepared the S2-2O8/ZrO2-CeO2solid super acid catalyst by theprecipitation-impregnation method with the S2-2O8as promoter. Explore the effect of impregnatedconcentration of S2-2O8, calcination temperature and the CeO2content on the structure and properties ofcatalyst. Catalysts structure characterized by FT-IR, XRD, Raman spectroscopy, TG, NH3-TPD techniques,FT-IR of adsorbed pyridine. The results show that the addition of CeO2can stable ZrO2tetragonal phasestructure and the addition of rare earth elements plays an extremely important role in the enhancement thecatalyst activity and acid strength of catalysts.