聚苯乙烯泡沫塑料鸡蛋纸箱，硬塑料紧凑型碟片，红色饮用杯和许多其他常见产品由聚苯乙烯组成，聚苯乙烯是一种占全球垃圾填埋场浪费的三分之一的塑料。

“In terms of plastic production and end-of-life waste streams, we are on the road to an unsustainable future,” said Erin Stache, assistant professor of chemistry and chemical biology in the College of Arts and Sciences.

但是有个好消息：Stache发现了一条新的聚苯乙烯废物的途径，其中包括通过使用光，富含氧气的环境和丰富的铁基催化剂的轻度工艺升级为具有广泛商业需求的化学物质。反应甚至可以在阳光明媚的窗户中发生。

该论文“通过催化剂控制的光氧化对商业聚苯乙烯进行化学升级”，于3月23日在《美国化学学会杂志》上发表。博士候选人Sewon OH是主要作者。

Stache说，根据她的实验室通过有趣的化学解决环境问题的使命，新过程对商业废物流进行了温和，对气候友好且可扩展。它有效地生产苯甲酸，苯甲酸是一种在本科和高中化学实验室中的产品，还用于香料，食品防腐剂和其他无处不在的产品。

Moreover, the process is tolerant of additives inherent in a flow of consumer waste, including dirt, dyes and other types of plastics.

聚苯乙烯（PS）塑料的形式，使用和质地差异很大 - 从轻，通风的泡沫聚苯乙烯到硬CD病例，以及介于两者之间的许多形式。Stache说，所有这些产品在化学成分上都是相似的。

“The difference is in how they are processed,” she said. “Polystyrene foam, or Styrofoam, is filled with air, like a meringue, whereas a hard plastic CD case is solid polystyrene.”

Stache说，在分子水平上，聚合物（塑料）由数百个称为单体的小分子组成，这些分子通过复杂的过程组装成长分子链。分解聚合物可能会同样复杂。

The researchers found that optimized conditions require a PS sample in acetone exposed to LED light in an oxygen-rich environment, using an iron chloride catalyst for 20 hours. In the optimized process, PS broke down to 23% benzoic acid. Other products included smaller plastic molecules that can be repurposed in other ways.

Last summer, Stache’s lab ran some degradation experiments in a sunny window; in a place with strong year-round sunlight, the reaction could be done outdoors.

“The advantage of using light is you can get exquisite control over the chemical process based on some of the catalysts we’ve developed to harness the white light. If we can use sunlight to drive the process, that’s a win-win,” Stache said, noting that many existing polymer recycling require heating a polymer for melting and processing, which usually requires fossil fuel.

To test the tolerance of the process to other materials mixed with the PS plastic, the researchers used several products, ranging from packaging materials to coffee cup lids.

他们发现三个物品有效地退化了三个物品 - 白色咖啡杯盖，泡沫塑料和清晰的盖子。Stache说，黑色咖啡杯盖的效率降低了，可能是因为黑色染料抑制了光穿透。

“These results signify that our system could efficiently break down commercial samples of PS, even with additional composite and insoluble material,” she said.

为了证明可扩展性和潜在的商业应用，研究人员在3D打印的光电反应器中创建了一个带有两个注射器泵和两个LED灯的设置。大规模分解过程的效率与小批量相似。

“If we can make the process even more efficient, we can think about how to commercialize it and use it to address waste streams,” Stache said.

参考：哦，S，Stache EE。通过催化剂控制的光氧化对商业聚苯乙烯进行化学升级。J Am Chem Soc。Published online March 23, 2022. doi:10.1021/jacs.2C01411

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