Mac Processor upgrade
Apple hardware does not use processor sockets. The CPU is soldered to the logic board. Upgrading a logic board on an older machine is only theoretically possible if there were more powerful processor options created for the same generation of machine, and then the parts and labor cost usually makes this unreasonable compared to the cost of purchasing a new Mac. You will not ever be able to use a current-generation processor in a vintage machine.

If you are unable to upgrade to a new computer, you may be able to find opportunity for increased performance by maxing out your system's RAM and exchanging the internal HDD for an SSD. I highly recommend OWC (macsales.com) as a resource for parts and compatibility when it comes to making these kinds of upgrades to older machines.