The idea of recycling post-consumer PET into valuable products, like aryl polyesters with properties similar to aryl polyamides (e.g., Kevlar and Nomex), is an interesting one. However, the proposed method involves several complex reactions that would need to be evaluated for their technical feasibility, economic practicality, and the final material properties. Let's break down the steps and consider the viability:

1. Hydrogenating PET with Copper Chromate to Obtain 1,4 Benzenedimethanol Ethylene Glycol Ether

Hydrogenating PET (polyethylene terephthalate) in the presence of copper chromate at 3000 psi is theoretically possible, but it would require careful consideration of the reaction conditions. Hydrogenation reactions typically require high pressure and temperature, and the role of copper chromate is to act as a catalyst for the hydrogenation process. However, this approach might be problematic for the following reasons:

Catalyst Selection: Copper chromate is a strong oxidizing agent, and it may not be the most ideal catalyst for this reaction, especially for selective hydrogenation. More commonly, palladium or platinum-based catalysts are used in hydrogenation reactions. Copper chromate could lead to unwanted side reactions or degradation of the PET, potentially reducing the yield of the desired product.

Reaction Conditions: The high pressure (3000 psi) and temperature would need to be optimized. While it's possible to hydrogenate aromatic compounds, the conditions may lead to undesirable polymer degradation or decomposition.

Selectivity and Yield: If the hydrogenation is successful, the goal is to obtain 1,4 benzenedimethanol ethylene glycol ether (a bisphenol ether), which would be a challenging synthesis in this context. Ensuring high selectivity and yield of this specific product would be critical, but hydrogenation could also lead to over-hydrogenation or other side products.

2. Cleaving the 1,4 Benzenedimethanol Ethylene Glycol Ether by Acid Hydrolysis to Obtain 1,4 Benzenedimethanol

The second step involves cleaving the 1,4 benzenedimethanol ethylene glycol ether through acid hydrolysis. This is a plausible reaction, as ether bonds can be cleaved under acidic conditions. The challenge here would be the reaction efficiency and the potential degradation of the resulting product, 1,4 benzenedimethanol, which could be sensitive to the reaction conditions (strong acids, high temperatures).

Hydrolysis Conditions: Mildly acidic conditions (e.g., dilute sulfuric acid or hydrochloric acid) might work, but care must be taken to avoid over-hydrolysis or degradation of the monomer. The yield of 1,4 benzenedimethanol would depend on factors such as temperature, acid concentration, and reaction time.

Purification: After hydrolysis, purification steps would be necessary to isolate the 1,4 benzenedimethanol, as the reaction may yield a mixture of products.

3. Reacting 1,4 Benzenedimethanol with Terephthalic Acid to Produce an Aryl Polyester

The third step is the polymerization of 1,4 benzenedimethanol with terephthalic acid to produce an aryl polyester. This step is similar to the synthesis of polyesters like PET or other high-performance thermoplastics. The reaction between 1,4 benzenedimethanol (a diol) and terephthalic acid (a dicarboxylic acid) would proceed via esterification to form the polymer.

Polymerization Conditions: The reaction would require high temperatures and a catalyst (such as titanium-based catalysts) to promote esterification and remove water. The molecular weight of the polymer would depend on the reaction conditions, and the polymerization process would need to be carefully controlled to avoid incomplete polymerization or low molecular weight chains.

Material Properties: The resulting polyester could have good mechanical properties, such as strength and rigidity, but it may not inherently possess the same thermal stability and strength as aryl polyamides like Kevlar or Nomex. Polyesters, particularly those based on terephthalic acid, are generally not as thermally stable as aryl polyamides. Aryl polyamides (e.g., Kevlar) possess unique strength and heat resistance due to the strong hydrogen bonding between aromatic rings and the rigid, high-strength polymer backbone.

However, modifying the polymer with certain additives or co-monomers might improve its thermal stability and mechanical properties, though it is unlikely to match the exceptional strength and heat resistance of Kevlar or Nomex unless specific modifications are made to the polymer structure (e.g., incorporating additional aromatic groups or rigid linkages).

Economic and Practical Considerations

Economic Viability: Recycling PET in this manner could be economically viable if the process can be optimized to maximize yield and minimize costs. The high pressure (3000 psi) and temperature required for the hydrogenation step could make the process energy-intensive. Additionally, the need for specialized catalysts and the potential for side reactions would add to the cost. If the process is scaled up, the costs of hydrogenation, hydrolysis, and polymerization could be significant.

Post-consumer PET Recycling: PET is a widely recycled polymer, but converting it into high-performance materials like aryl polyamides or specialized polyesters could open up new avenues for recycling. However, this would depend on the efficiency of the conversion process and the market demand for such materials.

Environmental Impact: If this process can be done efficiently, it could help reduce PET waste, contributing to more sustainable recycling practices. However, the environmental impact of using potentially hazardous chemicals (e.g., copper chromate, acids) and the energy required for high-pressure reactions would need to be evaluated.

Conclusion

While the general steps you propose (hydrogenation, hydrolysis, and polymerization) are chemically plausible, there are significant challenges to making the process economically viable and producing a material with properties comparable to aryl polyamides like Kevlar and Nomex. Specifically:

The hydrogenation step could face selectivity issues, and the use of copper chromate as a catalyst might not be ideal.

The hydrolysis step is feasible but would require precise control to avoid side reactions.

The polyester produced would likely have good mechanical properties but would need modifications (e.g., higher aromatic content or co-monomers) to achieve the extreme strength and thermal stability of aryl polyamides.

Ultimately, the concept could be developed into a valuable recycling process, but the properties of the resulting aryl polyester would likely not match the strength and thermal stability of Kevlar or Nomex without further refinement of the polymer chemistry. The economic feasibility would depend heavily on optimizing reaction conditions and minimizing energy and catalyst costs.