Sodium Silicates Modified Calcium Oxide as a High-Performance Solid Base Catalyst for Biodiesel Production

Round 1

Reviewer 1 Report

The authors prepared, characterized and tested a new catalyst for biodiesel synthesis based on silicate of calcium and sodium.The performances of the new catalyst were compared with the ones of CaO in different operative conditions obtaining better results for both activity and reusability. The article is well structured and complete. I have no objection to the publication of the work in the actual form.

Author Response

Point 1: The authors prepared, characterized and tested a new catalyst for biodiesel synthesis based on silicate of calcium and sodium.The performances of the new catalyst were compared with the ones of CaO in different operative conditions obtaining better results for both activity and reusability. The article is well structured and complete. I have no objection to the publication of the work in the actual form.

Response 1: Thank you for your encouragement and recommendation!

Reviewer 2 Report

The paper needs to be revised (Major revision):

1.     The paper lacks novelty and presents routine optimization studies for the effect of operating parameters. The presented results are average.

2.     It is not clear what new advantage or novelty is this catalyst going to bring in, as the results of the present work are inferior in many ways such as catalyst type, catalyst amount, and reaction temperature.

3.     In the statement from Lines 56-62 ‘Rabie et al. [12] prepared a new type of basic heterogeneous catalyst with CaO/MgO composite loaded on diatomite. They found that the diatomaceous earth support can significantly increase the total porosity and surface area of the catalyst, with a biodiesel yield high as 96.47%. Kandis Sudsakorn et al. [17] synthesized strontium (Sr)-doped CaO/MgO catalysts. The results showed that the Sr2+ could provide many strong basic sites over CaO/MgO, and a FAMEs (fatty acid methyl esters) yield of  99.6% was obtained under the optimal condition' is this FAME yield mentioned in literature was obtained before purification or after purification since its very unlikely to get such a high biodiesel yield in transesterification process.

4.     Symbol of degree (°) should be consistent throughout the manuscript, for example, lines 108, 112, 113, 120, and so on need to be corrected.

5.     What is the percentage of FAME conversion in the present work (The author should note that FAME conversion and FAME yield are completely different concepts)?

6.     Author should present GCMS spectra of feedstock and Biodiesel.

7.     What is the surface area of the synthesized catalyst?          

 

8.     The authors need to specify the physicochemical properties of produced biodiesel. 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Zhang et al. studied sodium silicates modified calcium oxide catalyst for biodiesel production.

 Also, the authors studied the  effects of reaction temperature, methanol ratio, catalyst loading, and reaction time on esters of biodiesel production.

The addition of the Na2CaSiO4 phase has improved the activity of CaO,

Although a set of characterizations was performed such as XRD, CO2-TPD, XPS spectroscopy as well as SEM microscopy, i cannot see any correlation among the physicochemical properties and the transesterification of soybean oil to FAME production. Also, textural properties of the solids are lacking. Therefore, the authors should perform major revision before acceptance of the manuscript.

Some examples are given below:

The materials and methods section should be placed after results and discussion to adhere the journal guidelines.

The usage and grammar of language should be corrected by native speakers.

1.Abstract

 Authors should describe the main results of the characterizations of the catalysts

2.            Introduction

The state of art  about FAME production is too weak.  The authors should be more concise in the instead of using 27 references in the introduction . The use of other basic catalysts  should be emphasized and compared with the expected features of the proposed materials.

3.            Materials and Methods

A schematic representation of the synthesis procedure should be given.

The ‘2.3. Catalyst characterization’ section should include the description of the equipment, according to the Catalyst journal rules.

4.            Results and discussion

 

-The authors should reanalysis the experimental data and find out the innovations of the article.

-The SEM results seem to be routine experiments. Remove or summarize these results .

-The structural analysis by XRD analysis and surface analyses by XPS and TPD-CO2 basicity measurements are not correlated.

Thus, why  authors state  that the silicate-strengthen strategy  improved the catalytic performance enabling the solids to have high activity and good reusability.

I can not see any correlation between the layered-like-sheet structure and the catalytic properties

5Conclusions

Conclusions are not supported by the data.  

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

After revision, the manuscript can be accepted for publication in Catalysts.