Short answer. In the partnership's name. Article 1774 says that immovable property, or an interest in it, may be acquired in the partnership name, and title so acquired can be conveyed only in the partnership name. So when the firm sells the land, the conveyance must be made in the name of the partnership that holds the title.
What the law says
Any immovable property or an interest therein may be acquired in the partnership name. Title so acquired can be conveyed only in the partnership name.
Civil Code, Article 1774 — Property in the Partnership Name. Read the full provision →
Land may be held in the firm's own name
A partnership is a juridical person, separate from the individuals who compose it, so it can own property in its own right. Article 1774 confirms this for real estate: any immovable property or an interest therein may be acquired in the partnership name. The land does not have to be titled in the names of the individual partners; the firm itself can appear as the registered owner. This recognizes that the partnership, and not merely the partners as private persons, is the entity that carries on the business and acquires assets for it. The title stands in the partnership's name because the partnership is the owner.
It can be conveyed only in that same name
The second sentence supplies the answer to the question. Article 1774 states that title so acquired can be conveyed only in the partnership name. Because the partnership holds the title, only the partnership can pass it on. When the land is sold, the deed of conveyance must run in the name of the partnership, transferring the title the partnership owns. The conveyance mirrors the acquisition: what was acquired in the firm's name is disposed of in the firm's name. This keeps the chain of title consistent and makes clear that it is the partnership, as owner, that is parting with the property.
What this means for the deed and the signatory
In practice, the selling party named in the deed should be the partnership itself, not a partner acting in his personal capacity. A partner does not hold the firm's registered title in his own name, so a deed in which he purports to sell the land as if it were personally his does not convey the partnership's title. The individual who signs does so on behalf of the partnership, as its representative. Getting this right protects the buyer, who needs a conveyance from the actual titleholder, and protects the partners, whose asset is transferred only through a proper act of the firm that owns it.
Form of conveyance versus authority to sell
Article 1774 settles the form the conveyance must take — the partnership name — but it does not, on its own, resolve whether a particular partner had authority to sell the land. Whether the sale binds the partnership depends on the partners' powers and the ordinary rules governing when a partner may dispose of firm property. So two questions must both be answered on any sale of partnership land: is the conveyance made in the partnership name, as this article requires, and did the person acting have authority to make it for the firm. This provision addresses the first; the partnership's internal rules of authority address the second.