Isopropylation of biphenyl (BP) over [Al]-SSZ-31, a large-pore, one-dimensional zeolite has been studied. Effects of temperature, pressure and SiO2/Al2O3 ratio were examined. SSZ-31 was found to be an active catalyst in the isopropylation of biphenyl with propylene. The selectivity for 4-isopropylbiphenyl (4-IPBP) and 4,4'-diisopropylbiphenyl (4,4'-DIPB) was high among isopropylbiphenyl (IPBP) and diisopropylbiphenyl (DIPB) isomers, respectively, indicating SSZ-31 shows shape-selective catalysis. The selectivity for 4,4'-DIPB decreased with temperature increased correspondingly the selectivity for thermodynamically more stable isomers (3,3'- and 3,4' DIPB) increased with temperature. The yield of IPBP isomers decreased while that of DIPB isomers increased with temperature increase. Pressure showed less effect on conversion; however, increase in pressure suppresses the isomerization of 4,4'-DIPB to 3,3'- and 3,4'-DIPB. Conversion decreased with increase in SiO2/Al2O3 ratio. At low SiO2/Al2O3 ratio of 136, relatively high triisopropylbiphenyl (TriIPB) isomers were formed in bulk products and their amount decreased with increase in SiO2/Al2O3 ratio.