Error when upgrading SQL 2016 to SP2 - "The given key was not present in the dictionary."
What I am understanding from your requirement to patch a sql clustered environment you are removing a node. This is definitely not the right way to proceed. You need to patch the current passive node first. Once everything goes well do a failover at node level. 

Now the patched passive node becomes active, do your health check for the patching done if all look green. Once ok, proceed with patching on current passive node. 

If there is any node preference you can failback to original active node and do health checks to ensure patching went well.