Sustainably Recycling and Upcycling of Single-Use Plastic Wastes through Heterogeneous Catalysis

Round 1

Reviewer 1 Report

Comment:

This is a comprehensive review paper on recycling and upcycling plastic waste with heterogeneous catalytic approaches. The authors summarize the current catalytic system with different process including thermal cracking and hydrocracking. Also, the manuscript covers both polyolefins and polyesters which are the major plastic waste in the real world. However, there are some remaining questions on the manuscript structure and performance comparison. Thus, I think a minor revision is needed for this manuscript before it published on Catalysts at this stage.

 

Specific comments:

1. This manuscript focuses on the heterogeneous catalysis approach on recycling and upcycling plastic waste with thermal operations. Instead of use ‘catalysis’ as a general word, the title needs to be narrow down to ‘heterogeneous catalysis’ or other specific word.

 

2. The authors summarize the recycling and upcycling process for polyolefins and polyesters. However, there are other groups of plastic waste including polycarbonate and miscellaneous plastics. Some short discussions on the recycling and upcycling approaches of these types of plastic waste is necessary to improve the manuscript.

 

3. From section 3 to 5, the authors discuss the acid catalyzed cracking of polyolefins, hydrogenolysis of polyolefins, and hydrogenolysis of polyesters, separately with a lot of reference. These paragraphs need to be categorized into a better-structured discussion either by the polymer group (e.g., polyolefins and polyesters) or by the reaction condition (e.g., thermal cracking without hydrogen and hydrocracking)

 

4. To upcycling the same plastic waste, both thermal cracking without hydrogen and hydrocracking are available based on the previous works summarized in the manuscript. Beside difference of the operation condition, the authors need to compare them with overall conversion and yield of specific products for a better understanding of the different processes.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript is an interesting and current review including recent advances in catalytic recycling of plastics, with new references of interest.

As an aid to authors, I provide two suggestions:

- The title "Sustainably recycling and upcycling of plastic wastes through catalysis" is too broad. Within this general title are processes in gas phase and in liquid phase, any type of catalysts and a variety of plastic waste (of industrial origin, waste of a single plastic material, mixtures of plastics, mixtures with impurities). I recommend revising the title and bringing it closer to the aspects in which the work deepens.

- Although the manuscript aims to provide useful information for industrial applications of catalytic recycling processes, information on reaction rates or production is scarce. Evaluate reinforcing this aspect. Please check if some recent works could be interesting in these aspects, such as those of the group of Prof. M. Olazar or those of the researcher E.G. Fuentes-Ordonez (PS hydrocracking).

Author Response

Please see the attachment.

Author Response File: Author Response.pdf