One big thing that the US is doing to reduce climate emissions is replacing the refrigerants that are major greenhouse gases (HFC) with HFO-1234y and so called natural refrigerants like propane and carbon dioxide. Many new cars use HFO-1234y in their air conditioner, it’s a big part of complying for with the carbon emissions standards implemented for cars during the Obama administration.
But outside of the HVAC and automotive engineering industry, virtually nobody knows this. Yet it’s not particularly controversial and as such the politicians don’t talk about it. It doesn’t require any action by consumers – a refrigerator that cools using CFC, HCFC, HFC or HFO-1234y works exactly the same – just some refrigerants destroy the ozone layer, others cause climate change. And others like HFO-1234y, Carbon Dioxide or Propane have a modest to almost zero impact on the climate when emitted into the atmosphere.
The other day, I mentioned that with thyristors connected to buck and boost converters, we could have built a much more efficient Direct Current electricity grid without the inherent losses from impedance with Alternating Current. We use 60 Hz AC mainly because it works well with (large) mains transformers and has a relatively low impedance, but it still has a lot of losses from impedance compared to direct current — and causes radio noise and hum. A high-voltage, direct current grid would not only be more efficient, you could bury direct-current lines easier, and not have to worry about storm damage.
The one issue I didn’t really address is the inherent dangers of high-voltage direct current — namely the difficulty of quenching arching, due to the lack of zero voltage crossing point. Direct current, especially high voltage direct current is difficult to break, as if you break mechanically, it will arc over — quite a long distance as the natural quenching of the zero voltage crossing point doesn’t exist like with AC. You can safely break a DC current using a thyristor, but what happens if a power line mechanically fails? It could arc over for some time, before fully breaking, causing enormous amounts of heat to be produced in the mean-time, turning large sections of wire into plasma. A high-voltage alternating current line might arc over and burn for a while, but it would relatively quickly break the connection, once enough of the line vaporized and sufficient air gap existed and the zero-point was crossed.
I often wonder if low cost thyristors existed in the first half of the century to produce buck and boost converters if the electrical grid would use direct current. High voltage DC doesn’t suffer from impedance, although it is more dangerous to touch as there is no zero point for seized muscle of a human to release themselves from it. High voltage DC is also much more difficult to break with a mechanical switch, due to a lack of zero point to prevent arcing, which is why they usually use thyristors rather than mechanical switches to break DC current.
As a building block chemical, benzene is reacted with other chemicals to produce a variety of other chemistries, materials and, ultimately, consumer goods.
Benzene is used to make other chemicals like ethylbenzene, cumene and cyclohexane, which are then reacted and used in the manufacture of a variety of materials and plastics such as polystyrene, ABS, and nylon. There can be many steps in the process that starts with the benzene molecule and ends with a completed material or consumer product. For example, benzene is a building block used to make ethylbenzene, which is then used to make styrene, which is used to make polystyrene. The end material, polystyrene, is a completely different material chemically than benzene.
For consumer products where benzene is used as a building block or intermediate, the benzene is typically fully reacted in a closed system, with little to no benzene remaining in the finished consumer product.
Benzene also is used to make some types of lubricants, rubbers, dyes, detergents, drugs, explosives and pesticides.
