shell - Adding Isolate CPU Cores in /etc/default/grub using sed -

i want add commands file /etc/default/grub using sed.

replace="intel_idle.max_cstate=0 isolcpus=2,4,6,8,10,12,14,16,18,20,22     nohz_full=2,4,6,8,10,12,14,16,18,20,22 rcu_nocbs=2,4,6,8,10,12,14,16,18,20,22"  sed -i 's/[a-za-z0-9]*grub_cmdline_linux=[a-za-z0-9]*/ $replace/g'   /etc/default/grub 

but not work. ideas ?¨