Method for producing silica gel-immobolized phosphonium salt catalysts

A method, comprising:

• (a) reacting a silane compound with a silica gel in the presence of xylene, to obtain a catalyst precursor having a haloalkyl group or a haloaryl group, wherein the silane compound has a haloalkyl group or a haloaryl group, and a proportion of the silane compound is from 0.001 to 0.06 mol relative to 1 mol of the silica gel;
• and
• (b) reacting the catalyst precursor with a tertiary phosphine, to obtain a catalyst for synthesizing a cyclic carbonate,
• wherein:
• the reacting (b) is carried out in xylene;
• the silane compound is represented by formula (1), and the tertiary phosphine is represented by formula (2):
• X—R1—Si(OR2)3 (1)
• R1 represents a linear or branched alkylene group haying 2 to 8 of carbon atom, an arylene group, an alkarylene group, an arylenealkylene group or an alkylenearylene group;
• R2 represents an alkyl group having 1 to 4 of carbon atom;
• X represents a halogen atom;
• and
• R3 to R5 each independently represent an alkyl group having 1 to 8 of carbon atom, an aryl group, an aralkyl group, an alkoxyalkyl group or an alkoxy-substituted aryl group.