Ten major Japanese oil and electric power companies have agreed to participate in the Exxon group's $300 million coal liquefaction project, the chairman of the Japanese Energy Policy Promotion Committee announced yesterday.

Sohei Nakayama said the 10 firms will establish Japan Coal Liquefaction Co. with a paid-up capital of $110.000 in early May.

The new company plans to sign an agreement with Exxon Research and Engineering Co., a subsidiary of the Exxon Corp., in mid-May to join the liquefaction technology development project, according to Nakayama.

The Japanese companies include Mitsubishi corp., Sumitomo Shoji, Tokyo Electric Power Co., Toyota Motor Co. and Esso Standard Oil.

The Exxon subsidiary's method, called EDS, can produce such light oil products as gasoline, naphtha and fuel oil from liquefied coal.

Under the project, Exxon Research will start building next month a massive pilot plant, capable of liquefying coal up to 250 metric tons per day, in the suburbs of Houston, Texas. It is expected to be completed at the end of 1979.

The U.S. firm hopes to establish by 1982 designs, technology and operating knowhow necessary for commercial level production of the products, according to Nakayama.

Nakayama said the Japanese member companies are prepared to pay up to $20 million as part of the group's research expenses over next five years.

He added the Japanese government would also provide a subsidy to help finance the project starting in 1979.