(CNN) -- White supremacist serial killer Joseph Paul Franklin was executed Wednesday morning after the U.S. Supreme Court rejected his final requests for a stay, the Missouri Department of Public Safety said.
The execution, which had been scheduled for shortly after midnight Wednesday, was delayed for hours because of court appeals. Franklin was administered a lethal injection at 6:07 a.m. CT (7:07 a.m. ET). He died ten minutes later.
Franklin refused his final meal and gave no final statement.
He was on death row for the 1977 murder of Gerald Gordon outside a synagogue in St. Louis. He was blamed for 22 killings between 1977 and 1980 in a bid to start a race war.
Missouri Gov. Jay Nixon denied clemency for Franklin on Monday, saying he had committed "merciless acts of violence, fueled by hate."
In addition to the killings, Franklin admitted to the attempted assassinations of Hustler magazine publisher Larry Flynt in 1978 and civil rights leader Vernon Jordan in 1980. Flynt, who was paralyzed by Franklin's bullet, has called for clemency for Franklin, saying "the government has no business at all being in the business of killing people."
Battle over drugs used
One of Franklin's final legal maneuvers focused on the drug used for the lethal injection, pentobarbital. His attorneys argued that the injection would violate the Constitution's ban on cruel and unusual punishment.
On Tuesday, U.S. District Judge Nanette Laughrey granted a stay of execution, finding Franklin's lawyers showed the use of pentobarbital carried "a high risk of contamination and prolonged, unnecessary pain beyond that which is required to achieve death."
"Given the irreversible nature of the death penalty and plaintiffs' medical evidence and allegations, a stay is necessary to ensure that the defendants' last act against Franklin is not permanent, irremediable cruel and unusual punishment in violation of the Eighth Amendment," Laughrey wrote.
Another federal judge granted a second stay Tuesday, based on a separate defense petition contesting Franklin's competency.
"The Court concludes that a stay of execution is required to permit a meaningful review," U.S. District Judge Carol Jackson wrote.
The state appealed both stays to the 8th U.S. Circuit Court of Appeals, which decided early Wednesday that Franklin's lawyers had not provided enough evidence to warrant a stay.
The U.S. Supreme Court denied Franklin's requests to step in and halt the execution.
Missouri had planned to use propofol, the surgical anesthetic made infamous by the death of pop star Michael Jackson. But Nixon reversed that decision after being warned that the European Union -- whose members forbid capital punishment -- might halt shipments of the drug, leading to shortages for medical purposes.
Missouri and other states that conduct executions have had to scramble for new drugs after European-based manufacturers banned American prisons from using their drugs in executions.
In October, the state announced it would use pentobarbital, which would be provided by an unnamed compounding pharmacy. Franklin's lawyers argued that would raise the risk of contamination and a painful death.
CNN's Dana Ford and Josh Levs contributed to this report.