Torbjorn Tornqvist, the billionaire who controlled about 64 percent of Swiss oil giant Gunvor as of last year, approached rivals about selling a stake in 2017 but failed. Gunvor has returned to the market more recently with preliminary talks with Algeria’s state oil company Sonatrach about a possible joint venture or a sale of the entire company.

Louis Dreyfus boss Margarita Louis-Dreyfus is in a similar boat. She took out a loan last year to help fund an obligation to buy about $900 million worth of other family members’ shares. That left her with 96 percent of the holding company that controls the trading house.

She has recently signaled again she’s open to selling a stake and opening the company to outside capital for the first time since it was founded more than 150 years ago. Louis-Dreyfus sought investors in 2015, but talks with investors including Singapore’s Temasek Holdings Pte Ltd. proved unsuccessful.

Trafigura Group Ltd., the world’s third-biggest oil trader, also toyed with the idea of bringing in an outside investor. Russia’s Rosneft PJSC proposed to take a 20 percent stake in the company in 2015, according to people familiar with the matter. It was rejected.

Officials at Gunvor, Louis Dreyfus and Trafigura declined to comment.

One trading house that has pulled off a deal is Geneva-based Mercuria, which sold a 12 percent stake to a consortium led by China National Chemical Corp. in 2016. That deal worked because both sides could bring something more than just money to the table, Mercuria’s co-founder Dunand said.

“If you have worked with someone for a long time, and you see synergies, and it’s real, it’s natural to seek to strengthen the ties,” he said. “If the only motivation is money, it probably isn’t going to work. ”

No IPO

Despite the failure to find investors, the traders aren’t taking the initial public offering option. The troubles of Hong Kong’s Noble Group Ltd., once Asia’s largest commodity merchant, have highlighted the perils of a public listing for a trader. While Switzerland’s Glencore Plc successfully sold shares, it evolved to become a full-blown mining company before the listing.

Instead they have sold stakes in non-trading businesses. Vitol has listed its Africa fuel-station business Vivo Energy Ltd. and its Australian counterpart Viva Energy Group Ltd. Trafigura, Gunvor and Louis Dreyfus have sold physical assets and issued bonds to raise capital.