Optimization and blends study of heterogeneous acid catalyst-assisted esterification of palm oil industry by-product for biodiesel production

The optimum conditions to produce palm fatty acid distillate (PFAD)-derived-methyl esters via esterification have been demonstrated with the aid of the response surface methodology (RSM) with central composite rotatable design in the presence of heterogeneous acid catalyst. The effect of four reaction variables, reaction time (30–110 min), reaction temperature (30–70°C), catalyst concentration (1–3 wt.%) and methanol : PFAD molar ratio (3 : 1–11 : 1), were investigated. The reaction time had the most influence on the yield response, while the interaction between the reaction time and the catalyst concentration, with an F-value of 95.61, contributed the most to the esterification reaction. The model had an R2-value of 0.9855, suggesting a fit model, which gave a maximum yield of 95%. The fuel properties of produced PFAD methyl ester were appraised based on the acid value, iodine value, cloud and pour points, flash point, kinematic viscosity, density, ash and water contents and were compared with biodiesel EN 14214 and ASTM D-6751 standard limits. The PFAD methyl ester was further blended with petro-diesel from B0, B3, B5, B10, B20 and B100, on a volumetric basis. The blends were characterized by TGA, DTG and FTIR. With an acid value of 0.42 (mg KOH g−1), iodine value of 63 (g.I2/100 g), kinematic viscosity of 4.31 (mm2 s−1), the PFAD methyl ester has shown good fuel potential, as all of its fuel properties were within the permissible international standards for biodiesel.


Recommendation?
Major revision is needed (please make suggestions in comments)

Comments to the Author(s)
In this submitted manuscript, the authors described the esterification of palm oil industry byproduct to produce biodiesel, and studied the properties of the resulted biodiesel. Some useful results were contained. In my opinion, this manuscript could be accepted after considering the following two points. 1. The stability of the used heterogeneous catalyst should be discussed. If possible, the properties of the synthesized catalyst and the recovered catalyst should be characterized. 2. The advantage of the resulted biodiesel should be discussed. At least, a comparison in various properties should be provided between the synthesized biodiesel and some reported typical biodiesel.

Review form: Reviewer 2
Is the manuscript scientifically sound in its present form? Yes

Do you have any ethical concerns with this paper? No
Have you any concerns about statistical analyses in this paper? No

Recommendation?
Accept with minor revision (please list in comments)

Comments to the Author(s)
The manuscript describes the biodiesel production from palm oil industry by-products by acidcatalyzed esterification reactions. The reaction conditions were thoroughly optimized by the response surface methodology (RSM). The various properties of the produced fuels and the blends with petro-diesel were analyzed. It is recommended to be published after revisions.

15-Oct-2019
Dear Dr Rashid: Title: Optimization and blends study of heterogeneous acid catalyst assisted esterification of palm oil industry by-product for biodiesel production Manuscript ID: RSOS-191592 Thank you for your submission to Royal Society Open Science. The chemistry content of Royal Society Open Science is published in collaboration with the Royal Society of Chemistry.
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RSC Subject Editor:
Comments to the Author: (There are no comments.) ********************************************** Reviewers' Comments to Author: Reviewer: 1 Comments to the Author(s) In this submitted manuscript, the authors described the esterification of palm oil industry byproduct to produce biodiesel, and studied the properties of the resulted biodiesel. Some useful results were contained. In my opinion, this manuscript could be accepted after considering the following two points. 1. The stability of the used heterogeneous catalyst should be discussed. If possible, the properties of the synthesized catalyst and the recovered catalyst should be characterized. 2. The advantage of the resulted biodiesel should be discussed. At least, a comparison in various properties should be provided between the synthesized biodiesel and some reported typical biodiesel.

Reviewer: 2
Comments to the Author(s) The manuscript describes the biodiesel production from palm oil industry by-products by acidcatalyzed esterification reactions. The reaction conditions were thoroughly optimized by the response surface methodology (RSM). The various properties of the produced fuels and the blends with petro-diesel were analyzed. It is recommended to be published after revisions.
1. In Table 1, the first column (variables) can be elongated to accommodate the whole word. Besides, the detailed reaction conditions can be provided as the footnote. 2. In Table 2, the "Wt.%" should be changed into "values", because the unit of the values are not all by weight. 3. The FTIR spectra are shown in an unclear manner. The figure should be replotted with higher resolution and different blends should be denoted by various colors. 4. The recyclability of the heterogeneous catalysts should be examined.

Recommendation? Accept as is
Comments to the Author(s) The issues have been properly addressed.
Decision letter (RSOS-191592.R1) 19-Nov-2019 Dear Dr Rashid: Title: Optimization and blends study of heterogeneous acid catalyst assisted esterification of palm oil industry by-product for biodiesel production Manuscript ID: RSOS-191592.R1 It is a pleasure to accept your manuscript in its current form for publication in Royal Society Open Science. The chemistry content of Royal Society Open Science is published in collaboration with the Royal Society of Chemistry.
The comments of the reviewer(s) who reviewed your manuscript are included at the end of this email. Comments to the Author(s) After carefully reviewing the revised version, I am satisfactory with the answers and changes provided by the authors. Therefore, I recommend the revised manuscript to be accepted.