Study On 3-methyl-3-butene-1-ol Formation In Supercritical Isobutylene Without Catalyst

Because of unique physical and chemical properties of supercritical fluids,reactions under supercritical condition which conducted in the presence of a supercritical fluid that plays the role of solvent or reactant applied widely in industry.3-Methyl-3-butene-l-ol(MBOH)is a commercially important compound which is widely used in synthesis of concrete polycarboxylic admixtures and biomimetic pesticides.An advanced synthesis technique of MBOH is uncatalyzed Prins reaction of isobutylene and formaldehyde in supercritical isobutylene,in which isobutylene is solvent as well as reactant.The depolymerization composition of paraformaldehyde(PA)is identified by gas chromatography-mass spectrometry(GC-MS),which includes methanol and methoxymethanol,also a bit of methyl formate,dimethoxy methane,2,4,6-trioxaheptane,2,4,6,8-tetraoxanonane,(methoxymethoxy)methanol and triethylamine.Supercritical isobutylene used as solvent,synthesis of MBOH from supercritical isobutylene and formaldehyde without catalyst was conducted at temperature 513.15-543.15K and pressure 15-20MPa in batch stirred tank reactor.The structures of main byproducts 3-methylbut-3-en-1-yl formate,3-methylenepentane-1,5-diol,(E)-3-methylpent-2-ene-1,5-diol and(Z)-3-methylpent-2-ene-1,5-diol were determined by GC-MS and nuclear magnetic resonance(NMR).PA feed rates changed,we found that more byproducts of formaldehyde and less MBOH are generated with the increase of PA feed rate.The reaction network of main reactions and corresponding kinetics model were established.Through experimental data fitting,the reaction rate constants for isobutylene with formaldehyde and MBOH with formaldehyde under different temperatures were obtained,and activation energies for the reactions were 101.95kJ/mol and 83.99kJ/mol,respectively.High reaction temperature favors MBOH selectivity.