The chemical reaction that feeds the world - Daniel D. Dulek

餵飽世界的化學反應 - Daniel D. Dulek

譯者: Regina Chu 審譯者: Marssi Draw

What would you say

你說在過去幾世紀裡

is the most important discovery

made in the past few centuries?

什麼是人類最重要的發現？

Is it the computer?

是電腦？

The car?

汽車？

Electricity?

電力？

Or maybe the discovery of the atom?

還是發現原子？

I would argue that it is this chemical reaction:

我會說是這項化學反應：

a nitrogen gas molecule

一個氮氣分子

plus three hydrogen gas molecules

加上三個氫氣分子

gets you two ammonia gas molecules.

得到兩個氨氣分子

This is the Haber process

這就是哈柏法

of binding nitrogen molecules in the air

將空氣中的氮分子

to hydrogen molecules,

與氫分子結合

or turning air into fertilizer.

或將空氣變成肥料

Without this reaction,

沒有這項反應

farmers would be capable of producing enough food

農夫僅可生產足夠

for only 4 billion people;

四十億人口所需的食物

our current population is just over 7 billion people.

我們目前的人口剛剛超過七十億

So, without the Haber process,

所以，沒有哈柏法

over 3 billion people would be without food.

有超過三十億的人會沒食物吃

You see, nitrogen in the form of nitrate, NO3,

你看，氮以硝酸鹽 NO3 的形式存在

is an essential nutrient for plants to survive.

是植物生存的一種基本營養素

As crops grow, they consume the nitrogen,

當作物生長，他們消耗氮

removing it from the soil.

從土壤中吸收氮

The nitrogen can be replenished

土壤中的氮可經由

through long, natural fertilization processes

長時間的自然施肥法補充

like decaying animals,

像動物腐化

but humans want to grow food

但人類想以更快的方法

much faster than that.

種植糧食

Now, here's the frustrating part:

那麼，這就是令人沮喪的部分：

78% of the air is composed of nitrogen,

空氣的組成中有 78% 為氮

but crops can't just take nitrogen from the air

但作物不能從空氣直接利用氮

because it contains very strong triple bonds,

因為它含有非常強的三鍵

which crops cannot break.

作物無法分解

What Haber did basically

基本上哈柏所做的

was figure out a way

是找出一種方法

to take this nitrogen in the air

把空氣中的氮

and put it into the ground.

放進土壤中

In 1908, the German chemist Fritz Haber

1908 年，德國化學家弗里茨·哈柏

developed a chemical method

發展出一種化學方法

for utilizing the vast supply of nitrogen in the air.

以利用空氣中取之不盡的氮

Haber found a method

which took the nitrogen in the air

哈柏發現一種方法 把空氣中的氮

and bonded it to hydrogen

與氫氣鍵結

to form ammonia.

以形成氨

Ammonia can then be injected into the soil,

然後氨可被注入土壤中

where it is quickly converted into nitrate.

在土裡快速轉變成硝酸鹽

But if Haber's process was going to be used

但如果哈柏法要能拿來用在

to feed the world,

餵飽全世界

he would need to find a way

他必須找出一種 能快速簡易製造出氨的方法

to create a lot of this ammonia quickly and easily.

In order to understand

為了瞭解

how Haber accomplished this feat,

哈柏如何達成這項豐功偉業

we need to know something

我們必須對

about chemical equilibrium.

化學平衡有一番瞭解

Chemical equilibrium can be achieved

要達到化學平衡

when you have a reaction in a closed container.

你的化學反應要在封閉容器下進行

For example, let's say you put

舉例來說，你把

hydrogen and nitrogen into a closed container

氫氣及氮氣放在封閉容器內

and allow them to react.

讓它們反應

In the beginning of the experiment,

實驗開始時

we have a lot of nitrogen and hydrogen,

我們有大量的氮及氫

so the formation of ammonia

所以氨的形成

proceeds at a high speed.

以高速進行

But as the hydrogen and nitrogen react

但當氫及氮反應一段時間

and get used up,

到快用完的時候

the reaction slows down

反應變慢

because there is less nitrogen and hydrogen

因為瓶子裡的氮及氫變少了

in the container.

Eventually, the ammonia molecules reach a point

最終，氨分子會達到一種情況

where they start to decompose

就是它們又開始分解

back into the nitrogen and hydrogen.

成為氮氣及氫氣

After a while, the two reactions,

一段時間後，這兩種反應

creating and breaking down ammonia,

就是產生及分解氨氣

will reach the same speed.

會達到相同速率

When these speeds are equal,

當這兩個速率相等時

we say the reaction has reached equilibrium.

我們就說反應達到平衡

This might sound good, but it's not

這聽起來不錯，但並非如此

when what you want

尤其當你只想要

is to just create a ton of ammonia.

產生一噸的氨氣時

Haber doesn't want the ammonia

哈柏根本不想讓氨氣

to break down at all,

再分解回去

but if you simply leave the reaction

但如果你就是把這項反應

in a closed container,

放在封閉容器裡進行

that's what will happen.

那就是必然的結果

Here's where Henry Le Chatelier,

這也就是亨利·路易·勒夏特列

a French chemist,

這位法國化學家

can help.

可以幫忙的地方

What he found was

他發現

that if you take a system in equilibrium

如果你把達到反應平衡的系統

and you add something to it,

加入某項東西

like, say, nitrogen,

像是，這麼說，氮氣

the system will work

這個系統會持續進行

to get back to equilibrium again.

直到再達到平衡為止

Le Chatelier also found

勒夏特列同時發現

that if you increase

如果你增加

the amount of pressure on a system,

一個系統的壓力

the system tries to work

這個系統會試著

to return to the pressure it had.

回到原有的壓力

It's like being in a crowded room.

這就像身處擁擠的房間

The more molecules there are,

分子愈多

the more pressure there is.

壓力愈大

If we look back at our equation,

如果我們回頭去看我們的方程式

we see that on the left-hand side,

我們會看見在左邊

there are four molecules on the left

左邊有四個分子

and just two on the right.

而右邊只有兩個

So, if we want the room to be less crowded,

所以，如果我們想讓房間不那麼擠

and therefore have less pressure,

並因而產生較小的壓力

the system will start

這個系統就會開始

combining nitrogen and hydrogen

結合氮及氫

to make the more compact ammonia molecules.

製造出較小巧緊密的氨分子

Haber realized that in order to make

哈柏瞭解到為了製造

large amounts of ammonia,

大量的氨

he would have to create a machine

他必須發明一種機器

that would continually add nitrogen and hydrogen

可以持續加入氮及氫

while also increasing the pressure

同時也要增加壓力

on the equilibrium system,

在這平衡系統上

which is exactly what he did.

這也正是他所做的

Today, ammonia is one of the most produced

今天，氨是世上產量最多的

chemical compounds in the world.

化學化合物之一

Roughly 131 million metric tons are produced a year,

每年產量粗估為 1 .31 億公噸

which is about 290 billion pounds of ammonia.

亦即二千九百億磅的氨

That's about the mass

這是大約

of 30 million African elephants,

三千萬隻非洲象的總重

weighing roughly 10,000 pounds each.

每頭約以一萬磅來算

80% of this ammonia is used in fertilizer production,

80% 生產出的氨拿來做肥料

while the rest is used

其餘則使用在

in industrial and household cleaners

工業及家用清潔用品上

and to produce other nitrogen compounds,

並拿來生產其他種氮化合物

such as nitric acid.

譬如硝酸

Recent studies have found

最近的研究發現

that half of the nitrogen from these fertilizers

半數肥料中的氮

is not assimilated by plants.

沒有被植物同化

Consequently, the nitrogen is found

結果是，氮就以

as a volatile chemical compound

揮發性化學化合物的形式

in the Earth's water supplies and atmosphere,

在地球的供水及大氣中被發現

severely damaging our environment.

嚴重破壞我們的環境

Of course, Haber did not foresee this problem

當然，在哈柏發表他的發明時

when he introduced his invention.

無法預測這個問題

Following his pioneering vision,

為了承接他的開創視野

scientists today are looking

當代科學家正在尋找

for a new Haber process of the 21st century,

21 世紀的新哈柏法

which will reach the same level of aid

以達到同樣程度的幫助

without the dangerous consequences.

卻無危險的後果