Milling Activation for the Solvent-Free Synthesis of Zeolites. A Practical Guide

Round 1

Reviewer 1 Report

This manuscript is highly recommended for publication because this manuscript describe the recent advance in zeolite synthesis. Before publications, I would like to ask the authors to check/consider the following point. 1. Please check minor mistakes, for example, "Bronsted acid" should be "Brønsted acid". 2. The one of the difficulties in ball milling is parameter optimization. Please discuss which conditions is the best for first trial experiment and the effective way to screen/optimize the parameters (ball size, rotation speed, time, interval time, and so on). These information would be very useful for the readers in catalyst community.

Author Response

Thank you for your positive opinion and suggestions.

Ad 1. "Bronsted acid" corrected to "Brønsted acid" in line 32 and Table 6.

Ad 2. The text was broadened in line 377:

The procedure for the first trial experiment may be suggested on basis of mill manufacturer recommendations for bowl filling. The amount of reagent mixture should be in a range corresponding to milling bowl size. For example, for the Fritsch Pulverisette 6 planetary mill, the user manual suggests that the capacity of a 250 ml bowl is 30-125 ml of the reagent mixture. Ball diameter and number of balls for the specific volume of the bowl should also follow manufacturer recommendations. For the Fritsch Pulverisette 6 planetary mill, the user manual instructs to apply 50 balls of 10 mm diameter or 45 balls of 15 mm diameter for a bowl of 250 ml volume. According to the authors’ experience, there was no significant difference in using 10 mm or 15 mm balls. Smaller balls were not applied, because the number of 5 mm balls recommended by the manufacturer was 1500 pieces, and in case the mixture would turn into a paste during milling, that would be difficult to separate them. Bigger balls were not applied for considerations connected with too intense milling and the probability of milling parts destruction (also according to the user manual). Optimization of milling speed and time should be performed starting from the lowest speed (e.g. 200 rpm) and the shortest times (e.g. 5 minutes). After the milling, it should be checked if the mixture activation was effective, which means if high crystallinity zeolite is formed after thermal treatment (synthesis in autoclaves). In case if the products are amorphous, or the crystallinity is low, a higher speed or longer time should be used in the next trial. On the other hand, if the crystallization was successful, the reduction of time and speed might be considered. Particular examples of milling time optimization strategy will be provided in the following Chapter. After each experiment (especially after applying speed higher than 400 rpm or milling time over 20 minutes) the analysis of chemical contamination of milled mixture is advised. The material from milling parts attrition should not appear in the mixture after milling.

Reviewer 2 Report

The paper (review) is well written and consolidates most of the information from literature and can be good resource for a researcher who wishes to work in this area. Automated milling as pointed out by authors does appear to be better method than manual milling it is still far from being used for large scale production of zeolites.

Author Response

Thank you for your comment. We agree that in solvent-free synthesis methods there is a significant gap between the lab-scale procedures and industrial-scale production. That is exactly why we wanted to explore the possibilities of automatized methods, especially in such aspects, where the high-energy milling considerably differs from the manual process. We believe that numerous new studies in this field will appear soon, bringing the gap between laboratory and industry.