fabric and in the pores and gaps between the nonwoven fabric fibers the catalytic coating uses solid acid as catalyst and polymer or modified sulfonated polymer as membrane forming material the membrane is formed by coating or immersion method and the composite catalytic membrane is obtained by cross linking after forming the greenization and high efficiency of catalytic esterification and preparation of biodiesel can be achieved owing to the microporous structure and huge specific surface area of the composite catalytic membrane the composite catalytic membrane has high mechanical strength good reproducibility and stability and easily enables continuous repetitive production of catalytic esterification the process is simple and easy to control and scale up application_number US 201113883798 A description the following examples may help professionals in the art fully understand the present invention but shall not be in any way limit the present invention using the base catalyzed hydrolysis method to modify the nonwoven fabric it covers the following steps prepare the naoh solution in ethanol at 5 g l and the aqueous solution of cetyl trimethyl ammonium bromide at 1 g l place the nonwoven fabric into a three necked flask add 50 ml of naoh solution in ethanol and 1 ml of fixed promoting agent then heat the mixed solution in a thermostatic water bath at 40 u00b0.