Study On Acetylation And Acetalization Of Glycerin With Solid Acid Catalysts Based On Phenolic Resin

As a renewable biomass energy,the biodiesel industry has achieved rapid development in recent years.The serious surplus of glycerol by-products limits the sustainable development of the biodiesel industry.From the perspective of green and sustainable development,the synthesis route of developing downstream high-value-added fine products with glycerol as raw material through catalytic conversion process has become a research focus in the neighborhood of bio-chemical industry,in which the development of high-efficiency catalysts is the focus.In this thesis,a series of phenolic resin-based solid acids have been designed and synthesized through phenolic condensation reaction,which are used for the acetylation and acetalization of glycerol,and the performance defects of traditional catalysts such as slow reaction rate and poor stability have been mainly solved;The structure and performance of the catalyst were investigated by using relevant characterization methods and correlated with the catalytic activity.The structure-activity relationship of phenolic resin-based solid acids in the process of glycerol acetylation and acetalization was clarified.The main research results were as follows:Using industrial and agricultural waste sodium lignosulfonate（LS-Na）and furfural as raw materials,a renewable phenolic resin-based solid acid catalyst（LFuS）with rich acidic sites on the surface was synthesized by a two-step process of phenolic condensation and sulfonation to catalyze the acetylation reaction of glycerol and acetic acid.The results showed that under the optimal reaction conditions,the conversion of glycerol could reach 98%,and the selectivity for glycerol diacetate and glycerol triacetate（DAG+TAG）was 94%,After 5 cycles of use,the selectivity of DAG+TAG decreased from 94%to 90%.The selectivity of DAG+TAG has a good linear relationship with the concentration of acidic sites on the catalyst surface.The increase of acidic sites and the formation of polyphenol structure are the key to the excellent catalytic activity of LFuS.In order to influence the hydrophilicity of solid acid surface and the concentration of acid sites on the catalytic conversion of glycerol,a series of p-hydroxybenzenesulfonic acid phenolic resins were synthesized by solvothermal method with p-hydroxybenzenesulfonic acid（PhOH-SO3H）and aldehyde monomers with different carbon chain lengths,which were used to catalyze the reaction of glycerol and propylene acetal.The results showed that the change of the carbon chain length in the aldehyde monomer could effectively control the surface hydrophilicity/hydrophobicity and acid site content of the catalyst.Among them,the acid resin PST synthesized by p-hydroxybenzenesulfonic acid and p-benzaldehyde had the best activity,the conversion of glycerol was 93%,the selectivity of acetone glycidyl was 97%,and the activity remained unchanged after 5 cycles.The excellent catalytic performance of PST-1.5 can be attributed to the synergy between hydrophobicity and acidic sites.The resin solid acid（PAG）after partial substitution of o-aminobenzenesulfonic acid for p-hydroxybenzenesulfonic acid and condensation polymerization of glyoxal was modified again with 1,3-propanesulfonate lactone to prepare the o-aminobenzenesulfonic acid phenolic resin solid acid（PSAG）grafted twice with SO3H,which was used to catalyze the reaction of glycerol and acetone acetal at room temperature.It was found that the pore structure of PAG was blocked when too much 1,3-propane lactone was modified,indicating that the morphology changed.Therefore,PSAG-1 has the best activity,can achieve100%catalytic conversion of glycerol at room temperature,and the selectivity of acetone glycidyl product is98%.The characterization structure showed that 1,3-propanolactone was successfully grafted onto the amino group and-SO₃H was successfully introduced,which increased the acid sites of PSAG,thus improving the catalytic activity of the catalyst.PSAG-1 has no obvious change in activity after repeated use,and has excellent stability.