Dow Chemical Co. earned $804.5 million ($4.42 a share) last year on sales of $10.626 billion, up from $783.9 million ($4.33 on 1.1 million fewer shares) and sales of $9.255 billion in 1979.

In the fourth quarter, Dow earned $242.3 million ($1.33) on sales of $2.772 billion compared with $194.3 million ($1.08 on 1.6 million fewer shares) and sales of $2.447 billion a year earlier.

In the final quarters of both years, Dow had capital gains of 28 cents a share on the sale of energy properties.

President Paul F. Oreffice said he was encouraged because the United States appeared to have recovered from the 1980 recession. He said the company also has had better sales recently in Latin America and in the Far East, notably in Korea.

He also said Dow's share of the profits of the Dowell oil and gas well service business and in Dowell-Schlumberger accounted for nearly 20 percent of Dow's profit in 1980.

Tenneco Inc., the nation's 10th-largest oil company, said yesterday that strong performances by its energy operations helped produce a 27 percent increase in earnings last year to a record $726 million ($5.94 a share) from the previous record of $571 million ($5.16) in 1979.

The widely diversified company said operting revenues rose to $13.2 billion from $11.2 billion in 1979.

Fourth-quarter earnings rose 22 percent to $200 million ($1.56) from $164 million ($1.49) in the comparable 1979 period. Revenues increased 11 percent to $3.6 billion in the three months from $3.3 billion a year earlier.

Tenneco Chairman James L. Ketelsen said the company's oil and gas exploration and production operations and natural gas pipeline business reported strong results, but profits were lower for construction and farm equipment, chemicals and automotive operations.

The insurance division also had higher operations because of the acquisition of Southwestern Life last May.

Standard Brands Inc. reported yesterday that net income rose 21 percent last year to $104.4 million ($3.65 a share) from $86.4 million ($3.04) in 1979. l

The foods and beverage manufacturer had record sales of $3 billion in 1980, up 15 percent from $2.6 billion in 1979.

Fourth-quarter profits rose 25 percent to $32.6 million ($1.14) from $26 million (92 cents) a year ago on a 14 percent sales gain to $867.4 million from $759.9 million.