The Study Of New Catalytic Technology Of Self-condensation Of Butanal To 2-ethylhexenal

Octanol is an important basic organic raw material and mainly used as plasticizer. It is primarily obtained by self-condensation of butanal to form 2-ethylhexenal using inorganic liquid base as a catalyst and then hydrogenation of 2-ethylhexenal. The current problems for the inorganic liquid base process are that great loss of alkali and producing waste water with high COD and pH value which is hard to deal with. To pursue green chemistry, to develop a novel process of the self-condensation of butanal to generate 2-ethylhexenal is becoming a trend. In view of this, three improved processes, introducing co-catalysts upon the current commercial process, using organic liquid base and solid base instead of inorganic liquid base, were researched.First, polyethylene glycol (PEG), polyvinylpyrrolidone (PVP) and ionic liquid were introduced to the current process as co-catalysts to enhance reaction process. Effects of molecular weight and concentration of PEG and PVP, the type and content of ionic liquid as well as reaction time and temperature on the catalytic performances were investigated. The results show that with PEG-10000 as co-catalyst, 3/1 mass ratio of PEG/NaOH, 0.5% of NaOH, 25min of the reaction time to catalyze self-condensation of 100ml of butanal, the obtained butanal conversion (XB%) and the 2-ethylhexenal yield (YEH%) attain 99.28% and 98.05%, respectively. It is 3.3% and 11.98% higher than the system without co-catalyst, respectively.Second, the process with the organic liquid base 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) as catalyst in the butanal self-condensation reaction was studied. Effects of H₂O/DBU, molar values and reaction time on the catalytic performances were investigated. Under the conditions of the molar ratio of 30, nDBU of 12.5×10-3 mol, 2h of reaction time, self-condensation of 20ml of butanal was catalyzed, and XB% and SEH% were 99.95% and 91.34%, respectively.Last, two solid base catalysts (inorganic-loaded solid base and organic-inorganic complex solid base) were prepared by impregnation and one-step synthesis, respectively. With MgO, CaO, SrO, and BaO as alkali sources, inorganic-loaded solid base of MgO/Al₂O₃, CaO/Al₂O₃, SrO/Al₂O₃ and BaO/Al₂O₃ were synthesized, respectively with alumina as carrier. The samples were applied to the synthesis of 2-ethylhexenal. While with 3-Aminopropyltrimethoxysilan(APTS), N,N-Diethyl-3- -aminopropyltrimethoxysilane (DAPTES), [N-(2-Aminoethyl)-3-aminopropyltrime- -thoxysilane (AAPTS) as alkali sources, organic-inorganic complex solid base catalysts of NH₂-SBA, NH₂NH-SBA, NR₂-SBA were prepared with SBA-15 as carrier. In terms of the catalytic performances, the results were obtained as the following sequence: NH₂-SBA>NH₂NH-SBA>NR₂-SBA. The SEH% value is obtained 65.64% with NH₂-SBA as catalyst.