Is there any recognized online portal where anyone can publish articles without being associated with any university or organization?
Yes, http://www.arxiv.org is the place for you.

But you can of course also publish in regular journals without being affiliated with a university. Science does not require a formal affiliation, just good ideas and data. If you have the latter, you can publish as a private citizen, an employee of a company, an employee of a government, or with any other background.