did you check the property "sonar.jdbc.schema" in both files "sonar.properties"?
if you have the two schemas sonar1 & sonar2 already created, you must specify the schema of the database to be used in both files, in your case:
In the sonar1 "sonar.properties" file ==> = sonar.jdbc.schema sonar1
In the sonar2 "sonar.properties" file ==> = sonar.jdbc.schema sonar2
OK, I think I understand better the cause of this problem, checked in your two tomcat instances the value of the variable SONAR_HOME in the file WEB-INF \ classes \ sonar-war.properties. if they are similar, then you must separate the two instances of Sonar / Tomcat in two different directories and then rebuild the war for each.
This will give the following structure:
folder1 contains : Sonar1 + Tomcat1
folder2 contains: Sonar2 Tomcat2
Note that after deploying sonar on Tomcat, it's just a webapp that is generated but the configuration is still in the installation folder in the Finder sonar.properties, therefore this folder must remain in the same directory that Tomcat instance.