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Why did the contact process replace the lead-chamber process for making sulfuric acid?

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A labeled diagram highlights sulfur's position on the periodic table, showing its atomic number 16, symbol S, atomic weight range, electron configuration, and classification as a solid, strongly acidic, orthorhombic nonmetal at room temperature. — sulfur Chemical properties of sulfur.

The contact process has largely replaced the chamber process for the industrial production of sulfuric acid primarily due to limitations in the older method's efficiency and output quality.

The chamber process relied on large, boxlike chambers constructed of lead, which is an awkward material for industrial construction. Furthermore, the chamber process is incapable of producing acid with a concentration greater than approximately 78 percent without undergoing additional, specialized treatment.1

In contrast, the modern contact process utilizes a hot reactor and a catalyst—typically a vanadium compound—to efficiently oxidize sulfur dioxide into sulfur trioxide. This method allows for higher conversion rates, exceeding 99 percent, and produces more concentrated acid, making it the standard for modern industrial production. Additionally, the contact process allows for the efficient capture and utilization of heat generated by the exothermic reactions, which helps maintain the cost-effectiveness of the acid.231