Wall Street gave up early gains after disappointing earnings from Coca-Cola and weak oil prices offset a boost fromApple.
Coke's revenue miss and forecast cut sent its stock down 3.4 percent, making it the biggest drag on the S&P and the Dow.
However, Apple shares rose 6.7 percent to $103.09 after the company sold more iPhones than expected in the third-quarter and gave an upbeat current-quarter forecast.
Investors are also awaiting the U.S. Federal Reserve's decision on interest rate hikes later in the day.
While the central bank is expected to keep rates steady for now, a recent set of strong economic data could make a case for an increase in the coming months.
"The Fed clearly will not raise interest rates," said Chris Zaccarelli, chief investment strategist at Cornerstone Financial Partners. "But I think you will see a slight move in position where The Fed is going to suggest that they are looking to raise rates at least once this year."
Traders have priced in a 19.5 percent chance of a rate increase in September and a 42.8 percent chance in December, according to CME Group's FedWatch tool.
At 11:08 a.m. ET the Dow Jones Industrial Average was up 10.64 points, or 0.06 percent, at 18,484.39.
The S&P 500 was down 2.98 points, or 0.14 percent, at 2,166.2.
The Nasdaq Composite index was up 22.66 points, or 0.44 percent, at 5,132.70.
Seven of the 10 major S&P sectors were lower, led by 1.2 percent drop in the consumer staples index.
Oil prices tumbled more than 2 percent, hitting a two-month low, after the U.S. government reported a surprise build in crude and gasoline inventories during the peak summer driving season.
Twitter plunged 12.3 percent after the microblogging service provider reported its slowest quarterly revenue growth since going public in 2013.
Facebook, Amgen and Whole Foods are expected to report after the bell on Wednesday.
Declining issues outnumbered advancing ones on the NYSE by 1,463 to 1,371. On the Nasdaq, 1,525 issues rose and 1,137 fell.
The S&P 500 index showed 37 new 52-week highs and no new lows, while the Nasdaq recorded 92 new highs and 11 new lows.
Researchers in US find way to convert carbon dioxide to fuel
Researchers from the US Department of Energy's Argonne National Laboratory and the University of Illinois at Chicago have found a way to convert carbon dioxide to useful fuel.
The researchers converted carbon dioxide to useful fuel by using solar energy which could open up possibility of a new source of energy as well find way in combating climate change.
The main challenge before the researcher was to sequester carbon dioxide which is relatively chemically unreactive. However, the researchers found out a catalyst which could make carbon dioxide react more readily.
Argonne National Laboratory chemist Larry Curtiss and the author of the study said: "On its own, it is quite difficult to convert carbon dioxide into something else.”
In natural way, plants use an organic catalyst called an enzyme to covert carbon dioxide from the atmosphere into a sugar, while the researchers used a metal compound called tungsten diselenide.
The metal compound was fashioned into nanosized flakes to maximize the surface area and to expose its reactive edges.
In this process, scientists managed to convert carbon dioxide to carbon monoxide. Though carbon monoxide is itself a greenhouse gas, it is more reactive than carbon dioxide which will help scientists to convert it into usable fuel, such as methanol.
Argonne National Laboratory physicist Peter Zapol and another author of the study said: "Making fuel from carbon monoxide means travelling 'downhill' energetically, while trying to create it directly from carbon dioxide means needing to go 'uphill.”
The reaction to convert carbon dioxide into carbon monoxide is different from the process found in nature, but the basic inputs are same.
Curtiss added: “In photosynthesis, trees need energy from light, water and carbon dioxide in order to make their fuel; in our experiment, the ingredients are the same, but the product is different."
The research was funded by the U.S. Department of Energy's Office of Science and the National Science Foundation.
Researcher carried the most of the experimental work at the University of Illinois at Chicago, while the computational work was performed at Argonne.
During the study, the researchers also found that the reaction requires less energy and efficient while the tungsten diselenide catalyst used in the reaction is quite durable enough, lasting for more than 100 hour.
Zapol added: "We burn so many different kinds of hydrocarbons — like coal, oil or gasoline — that finding an economical way to make chemical fuels more reusable with the help of sunlight might have a big impact."