dbms_utility.exec_ddl_statement errors when executing SQL that works just fine.

I'm trying to create a function that will return a timezone that is buried in the xml column (MY_XML_Column) of the table My_Tablename.

When I execute the results of the dbms_output.put_line( v_sql); in the middle of the stored procedure, it works just fine.

But when I try to use dbms_utility.exec_ddl_statement, I get the following errors:

Error report -

ORA-00905: missing keyword

ORA-06512: at "SYS.DBMS_UTILITY", line 574

ORA-06512: at line 17

00905. 00000 -  "missing keyword"

*Cause:   

*Action:

DECLARE

v_timezone_table  varchar2(50):= 'my_tablename';

  v_id  number :=1;

  v_sql varchar2(1000);

   v_output_time_zone varchar2(50);