Catalytic performance of SO₃H-MCM-41 on addition reaction of acrylic acid and i-butene

Mesoporous SO₃H-MCM-41 was prepared by direct hydrothermal condensation method, and characterized by using XRD, N₂ adsorption-desorption, FT-IR, Py-IR and acid-base titration. The catalytic performance of SO₃H-MCM-41 on synthesis of t-butyl acrylate by the direct addition of acrylic acid with isobutene was studied. With n(i-Butene)/n(Acrylic acid) of 1, the effects of the preparation condition of n(Sulfonic acid)/n(Silica) and the direct addition reaction conditions of reaction temperature, m(t-Butanol)/m(Acrylic acid) and m(Catalyst)/m(Acrylic acid) on conversion of acrylic acid and selectivity of t-butyl acrylate were investigated. It was shown that the sulfonic acid functional group was successfully grafted onto the surface of MCM-41 and the typical mesoporous structure of MCM-41 was generally remained. With the increase of n(i-Butene)/n(Acrylic acid) the conversion of acrylic acid could be increased, while t-butyl acrylate selectivity was unchanged. With the SO₃H-MCM-41 as catalyst prepared at n(Sulfonic acid)/n(Silica)=0.3 and under the conditions of reaction time 6 h, reaction temperature 50℃, n(i-Butene)/n(Acrylic acid)=2, m(t-Butanol)/m(Acrylic acid)=0.01 and m(Catalyst)/m(Acrylic acid)=0.04 in the addition reaction, the conversion of acrylic acid could reach 90%, selectivity of t-butyl acrylate and diisobutylene were 92.8% and 4.8%, respectively. Moreover, the catalyst could be reused for 5 times with its catalytic activity essentially unchanged. High conversion of acrylic acid was benefit to reduce energy consumption of separation in industrial process.