You will need to install either the client tools or SQL Server Data Tools on the server that runs the packages. This will install the 32 bit DTExec.exe.

http://msdn.microsoft.com/en-us/library/hh231187(v=sql.110).aspx

Then it's as simple as pointing to "C:\Program Files (x86)\Microsoft SQL Server\110\DTS\Binn\DTExec.exe" in your batch file.