Not to mention the 9v battery is so small it lacks the capacity. Even if a small 9v battery were capable of 12v, it would discharge whatever power was saved up before it even managed to crank the motor once. Sort of like trying to wash a car with a squirt gun vs a hose. The squirt gun may put out just as much pressure but one or two squirts aren't going to even wet the whole car where a hose can fully rinse it due to much higher volume of water (continual supply).
Options would be a 12v trickle charger (slow, takes hours typically), or for immediate results jumper cables and slave starting off another vehicle or a charged jump pack (smaller version of a 12v battery designed for emergency starting like jumper cables without another vehicle).
Also something to keep in mind, depending on the condition of the battery a simple jump start may work if the battery is just dead enough that it won't start your vehicle. If it's in really bad shape it may not hold much of a charge at all and will leave you stranded again once you reach work or your destination. If the battery's ability to retain much if any charge is that compromised the vehicle could stall while driving as well. A battery in really poor condition could put extra strain on the alternator as well.