Analysis: We know that Fe can be reduced from its oxide with C (or CO), but active metals such as Na and K cannot be reduced with C (or CO). The situation of aluminum is similar to sodium and potassium.
At the earliest, people used the most active metals such as Na and K to react with Al2O3 at a certain temperature to replace Al. The price of aluminum obtained by this method is close to the price of gold.
After people finally invented electrolytic aluminum, the price of Al was greatly reduced, thus entering people's lives.
However, electrolytic aluminum production needs a lot of electricity, so people have been studying the method of reducing Al2O3 with cheap reducing agents such as C for nearly a hundred years. Unfortunately, although some progress has been made in this kind of research (Japan is more advanced), it basically stays at the laboratory level.
This question can also refer to the following information:
Ironmaking technology has been passed down for many centuries. People have used iron for generations, but they have never seen what aluminum metal looks like. It was not until 1827 that German chemist Willer used metallic potassium as reducing agent to reduce metallic aluminum from anhydrous aluminum trichloride. However, Weiler produces very little metallic aluminum, and the price is more expensive than gold.
Aluminum products at that time were always regarded as treasures. According to legend, at a palace banquet held in Charles Louis Napolé on Bonaparte, the guests used noble gold and silver tableware, while Charles Louis Napolé on Bonaparte himself used rare aluminum tableware at that time, which made the surrounding guests envious. It can be seen how high the price of aluminum was at that time.
The inventor who made aluminum a cheap metal and was widely used was Hall. He believes that to reduce the cost of aluminum smelting, the first thing is to use cheap raw materials, namely alumina, which is a mineral with great reserves; Secondly, electrolysis is adopted, which is cheap in electricity and can be used for large-scale continuous production, thus greatly reducing the cost. So, under the guidance of Yan Weite, a chemistry professor at Oberlin College, Hall began to study electrolysis.
The melting point of alumina is very high, reaching 2020℃. Electrolysis must be melted first, so it is difficult to electrolyze at such a high temperature. Hall envisions adding other substances to alumina to reduce its melting point. Through the study of many compounds, cryolite was finally selected to reduce the melting point of alumina, which reduced the electrolysis temperature by 1000 degrees. Hall finally solved this problem and made aluminum from electrolytic alumina ore. This method not only greatly reduces the production cost of aluminum, but also provides a broad prospect for utilizing the most abundant metals in the earth's crust.
February 23rd, 1886, which is a memorable day. Hall happily came to Yanwitt's laboratory and showed the professor an aluminum ball, which Hall made by electrolysis. These balls are still preserved in Alcoa, which has always regarded them as priceless.
Later, Hall further improved his invention and obtained a patent. Alcoa bought Hall's patent, produced aluminum metal on a large scale at a very low cost, and rapidly expanded the use of aluminum.