回收利用技术的突破或将使废塑料成为高价值商品

新方法将废塑料转化为热解油，其中含有各种工业中使用的有价值的烯烃

这个工艺提供了从废塑料中提取每吨价值高达6000美元的高价值乙醇的机会

这项创新技术具有潜在的环境效益和经济效益，为回收利用行业开辟了一条令人兴奋的发展道路

据油价网2023年8月15日报道，废塑料在这个世界随处可见。废塑料的价值如此之低，以至于没有一个好规划可以推动废塑料回收利用率超过10%。

尽管许多美国人每周都尽职尽责地把塑料垃圾放入合适的垃圾箱里，但其中许多材料，包括柔性薄膜、多层材料和许多彩色废塑料，是不能用传统机械回收方法回收的。

最终，美国只有大约9%的废塑料被重新利用，而且通常是在低价值产品中。然而，最近通过一项新技术，威斯康星大学麦迪逊分校的化学工程师们正在将低价值废塑料转化为高价值产品。

今年8月11日出版的《科学》杂志上描述了这种新方法，它可以增加废塑料回收的经济激励，并为回收新型塑料打开大门。研究人员估计，他们的方法还可以将这些工业化学品的传统生产过程中的温室气体排放量减少大约60%。

这项新技术依赖于几种现有的化学加工技术。第一种是热解，在无氧环境下将废塑料加热到高温。其结果是热解油，一种各种化合物的液体混合物。裂解油含有大量烯烃，这是一种简单的碳氢化合物，是当今化学品和聚合物的主要组成部分，包括各种类型的聚酯、表面活性剂、醇和羧酸。

在目前的能源密集型工艺中，如蒸汽裂解，化学品制造商通过将石油置于极高的热量和压力下生产烯烃。在这个新工艺中，威斯康星大学麦迪逊分校的研究小组从裂解油中回收烯烃，并将其用于一种能源消耗更少的称为均相氢甲酰化催化的化学过程。这个过程将烯烃转化为醛，然后醛可以进一步还原成重要的工业乙醇。

化学和生物工程教授乔治·胡贝尔说：“这些产品可以用来制造各种价值更高的材料。”胡贝尔与博士后研究员李厚谦(音译)和博士生吴家阳(音译)共同领导了这项研究工作。

这些高价值的材料包括用于制造肥皂和清洁剂的成分，以及其他更有用的聚合物。

“我们对这项技术的影响感到非常兴奋。”胡贝尔说，胡贝尔也是美国能源部资助的废塑料化学升级再利用中心主任，“这是一种利用氢甲酰化化学对塑料废物进行升级的平台技术。”

回收利用行业可能很快就会采用这种方法。近几年来，至少有10家大型化工公司已经建成或宣布了从废塑料中生产裂解油设施的计划。他们中的许多人将裂解油通过蒸汽裂解装置生产低价值化合物。新的化学回收技术可以提供一种更可持续、更有利可图的方法来利用这些裂解油。

李厚谦解释说：“目前，这些化工公司没有一个真正的好方法来升级裂解油。在这种情况下，我们可以从每吨仅价值约100美元的废塑料中获得价值1200至6000美元的高价值乙醇。此外，这个过程使用现有的技术和工艺来扩大生产规模相对容易。”

胡贝尔指出，这项研究是威斯康星大学麦迪逊分校几个不同部门的合作成果。化学系系主任、氢甲酰化领域的世界级专家克拉克·兰迪斯提出了将该技术应用于裂解油的可能性。化学和生物工程教授马诺斯·马瓦里卡基斯使用先进的模型来提供对化学过程的分子水平的洞察。化学和生物工程教授维克多·扎瓦拉帮助分析了该技术的经济性和塑料废物的生命周期。

胡贝尔说，这个团队的下一步是调整工艺，更好地了解回收塑料废物和催化剂组合产生的最终化学产品。

胡贝尔说：“有很多不同的产品，有很多不同的路线，我们可以利用这个平台技术。”“我们生产的产品有巨大市场。我认为这真的可以改变废塑料回收利用行业。”

人们希望胡贝尔教授的观点成为现实。塑料垃圾给世界环境带来的混乱、烦恼、污染和破坏是一个日益严重的问题。甚至有早期的研究表明，人类体内有少量的塑料颗粒积聚，其影响尚未完全了解。

毫无疑问，塑料是一种奇妙的材料，而且功能通过长时间的应用得到了充分证明。任何理性人士都不会反对使用它们。但是，市场增长和各种各样的用途使塑料垃圾遍布全球。废塑料污染问题正在成为一个庞然大物，迟早将会得到处理。

李峻 译自 油价网

原文如下：

Recycling Breakthrough Makes Plastic Waste A High Value Commodity

·     The new method converts waste plastic into pyrolysis oil, which contains valuable olefins used in various industries.

·     This process offers an opportunity to derive high-value alcohols worth up to $6,000 per ton from waste plastics.

·     The innovative technique presents potential environmental benefits, economic gains, and an exciting path forward for the recycling sector.

The world is awash in waste plastic. Its value is so low that no good program exists to drive the recycling effort past 10%.

Although many Americans dutifully deposit their plastic trash into the appropriate bins each week, many of those materials, including flexible films, multilayer materials and a lot of colored plastics, are not recyclable using conventional mechanical recycling methods.

In the end, only about 9 percent of plastic in the United States is ever reused, often in low-value products. With a new technique, however, University of Wisconsin-Madison chemical engineers are turning low-value waste plastic into high-value products.

The new method, described in the Aug. 11, 2023 issue of the journal Science, could increase the economic incentives for plastic recycling and open a door to recycling new types of plastic. The researchers estimate their methods could also reduce greenhouse gas emissions from the conventional production of these industrial chemicals by roughly 60 percent.

The new technique relies on a couple of existing chemical processing techniques. The first is pyrolysis, in which plastics are heated to high temperatures in an oxygen-free environment. The result is pyrolysis oil, a liquid mix of various compounds. Pyrolysis oil contains large amounts of olefins – a class of simple hydrocarbons that are a central building block of today’s chemicals and polymers, including various types of polyesters, surfactants, alcohols and carboxylic acids.

In current energy-intensive processes like steam cracking, chemical manufacturers produce olefins by subjecting petroleum to extremely high heat and pressure. In this new process, the UW-Madison team recovers olefins from pyrolysis oil and uses them in a much less energy-intensive chemical process called homogenous hydroformylation catalysis. This process converts olefins into aldehydes, which can then be further reduced into important industrial alcohols.

“These products can be used to make a wide range of materials that are higher value,” said George Huber, a professor of chemical and biological engineering who led the work alongside postdoctoral researcher Houqian Li and PhD student Jiayang Wu.

These higher-value materials include ingredients used to make soaps and cleaners, as well as other more useful polymers.

“We’re really excited about the implications of this technology,” said Huber, who also directs the Department of Energy-funded Center for the Chemical Upcycling of Waste Plastics. “It’s a platform technology to upgrade plastic waste using hydroformylation chemistry.”

The recycling industry could adopt the process soon; in recent years, at least 10 large chemical companies have built or announced plans for facilities to produce pyrolysis oils from waste plastics. Many of them run the pyrolysis oil through steam crackers to produce low-value compounds. The new chemical recycling technique could provide a more sustainable and lucrative way to use those oils.

Li explained, “Currently, these companies don’t have a really good approach to upgrade the pyrolysis oil. In this case, we can get high-value alcohols worth $1,200 to $6,000 per ton from waste plastics, which are only worth about $100 per ton. In addition, this process uses existing technology and techniques. It’s relatively easy to scale up.”

Huber noted the study was a collaborative effort across a few different UW-Madison departments. Clark Landis, chair of the Department of Chemistry and a world expert on hydroformylation, suggested the possibility of applying the technique to pyrolysis oils. Chemical and biological engineering Professor Manos Mavarikakis used advanced modeling to provide molecular-level insight into the chemical processes. And chemical and biological engineering Professor Victor Zavala provided help analyzing the economics of the technique and the life cycle of the plastic waste.

The next step for the team is to tune the process and better understand what recycled plastics and catalyst combinations produce which final chemical products.

“There are so many different products and so many routes we can pursue with this platform technology,” said Huber. “There’s a huge market for the products we’re making. I think it really could change the plastic recycling industry.”

One hopes the professor’s view comes true. The mess, annoyance , pollution and damage due to plastic waste in the environment is a fast growing problem. There are even early of research efforts showing tiny bit of plastic accumulating in our bodies – to effects not yet fully understood.

Plastics are wonderful materials, no doubt and fully proven. No one with any sense is opposed to their use. But the growth of the market and vast array of uses that has spread the refuse across the planet is becoming a monster that would be dealt with better sooner than later.