Congressional leaders expressed disappointment yesterday that Paul A. Volcker will be leaving as chairman of the Federal Reserve Board and mixed reactions to President Reagan's selection of economist Alan Greenspan as his successor.

Economic analysts said Greenspan, an adviser to three presidents, likely will be more politically attuned than Volcker but generally will follow the same economic track.

In Bonn, West German Finance Minister Gerhard Stoltenberg said "Volcker will go into U.S. history as one of the most important Fed chairmen." Foreign officials spoke warmly of Greenspan, however.

Sen. William Proxmire (D-Wis.), chairman of the Senate Banking Committee, which votes on Federal Reserve nominations, did not mention Greenspan's name in a statement praising Volcker.

"I think it is a serious loss to this country," Proxmire said. "Mr. Volcker has been a superb chairman of the Federal Reserve Board. He has the confidence of the business community. He has the confidence of the Congress. He has the confidence of the country. And I thought he had the confidence of the administration."

Proxmire said, "We should keep in mind that it was Paul Volcker's policies, unpopular policies, that broke the back of inflation. And he persisted in those policies for three or four tough years in spite of the overwhelming criticism by both administrations and by the Congress.

"We're going to miss him, miss him very much," he said.

Sen. Jake Garn (R-Utah), former banking committee chairman and now the ranking Republican on the panel, said he had urged Volcker to seek reappointment and urged President Reagan to reappoint him. "Chairman Volcker has enjoyed enormous respect and has served extremely well," Garn said.

But he said Greenspan was an excellent choice to succeed Volcker. "He is a respected, internationally recognized economist. I don't think the president could have found a better replacement."

Sen. Paul Sarbanes (D-Md.), chairman of the Joint Economic Committee, called Volcker a "dedicated public servant who guided the Federal Reserve through particularly turbulent times in the U.S. and world economies. . . .While I have from time to time differed with him on policy matters, I have great respect for his ability and for his commitment to such a demanding job for the past eight years."

Senate Majority Leader Robert C. Byrd (D-W.Va.) called Greenspan a man of considerable knowledge and experience who "will need these skills as he and the Federal Reserve Board confront the daunting challenges ahead -- keeping inflation under control, encourage growth and sustain confidence in our economy, both home and and abroad."

Senate Minority Leader Bob Dole (R-Kan.) said, "While Paul Volcker's retirement is a real loss, this country is very fortunate to have a man of Alan Greenspan's caliber to take his place."

Speaking of Greenspan, House Speaker Jim Wright (D-Tex.) said, "He would not have been my choice."

Wright, reflecting on Greenspan's work as chairman of the Council of Economic Advisers under presidents Ford and Reagan, said: "His previous service . . . indicates a kind of economic policy based on 'trickle-down' rather than 'percolate up.' I think it essential that policies be initiated to reduce the levels of interest rates."

Economic analysts said that if forced to choose between growth at the expense of some price increases and no growth and no inflation, Greenspan probably would take the former.

"The policies of the Fed probably will not change very much even with Volcker gone," said Michael Evans, an economic analyst in Washington. "After all, the alternative was appointing some type of easy-money guy who thinks interest rates have been too high for the past few years. That's not Greenspan at all."

Britain's top Treasury official, Chancellor of the Exchequer Nigel Lawson, describing Greenspan as "an excellent choice" and said he expected no policy changes under Volcker's successor.