Agricultural Waste-Based Heterogeneous Catalyst for the Production of Biodiesel: A Ranking Study via the VIKOR Method

Abstract

Agricultural waste-based heterogeneous catalysts are emerging as efficient and green catalysts. The present study explored the agricultural waste-based heterogeneous catalyst utilized in the production of biodiesel. The plant waste is composed of organic compounds and various metals which, on combustion, produces ashes that mainly consist of various metal carbonates and oxides. The most commonly employed approach for the solid catalyst preparation from plant materials is the calcination process, and it is performed at temperatures ranging from 300 to 1200°C. It is known that the temperature employed for calcination plays a vital role in the composition and development of the morphology of the catalyst. The variation in alkalinity, porosity, and, accordingly, the catalytic activity of the catalyst is significantly influenced by the calcination temperature. It was found that the potassium present in the form of oxide and carbonate as the main constituent in such catalysts played a significant role in delivering catalytic efficacy. Therefore, a number of agricultural waste-based catalysts were reported as efficient catalysts. The selection of the catalyst may be one of the important issues for application in large-scale biodiesel production. Thus, the present study was undertaken for the preparation of a rank list among the reported catalysts by following the VIKOR (Višekriterijumsko Kompromisno Rangiranje) multicriterion decision-making approach. In this work, the ranking study was performed considering the reported optimum reaction conditions (ORCs) of biodiesel synthesis reactions. The study was conducted strictly on the basis of the parameters, viz., catalyst concentration ( <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" id="M1"> <a:msub> <a:mrow> <a:mtext>C</a:mtext> </a:mrow> <a:mrow> <a:mn>1</a:mn> </a:mrow> </a:msub> </a:math> ), MTOR ( <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" id="M2"> <c:msub> <c:mrow> <c:mtext>C</c:mtext> </c:mrow> <c:mrow> <c:mn>2</c:mn> </c:mrow> </c:msub> </c:math> ), reaction temperature ( <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" id="M3"> <e:msub> <e:mrow> <e:mtext>C</e:mtext> </e:mrow> <e:mrow> <e:mn>3</e:mn> </e:mrow> </e:msub> </e:math> ), reaction time ( <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" id="M4"> <g:msub> <g:mrow> <g:mtext>C</g:mtext> </g:mrow> <g:mrow> <g:mn>4</g:mn> </g:mrow> </g:msub> </g:math> ), and biodiesel yield ( <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" id="M5"> <i:msub> <i:mrow> <i:mtext>C</i:mtext> </i:mrow> <i:mrow> <i:mn>5</i:mn> </i:mrow> </i:msub> </i:math> ). The parameters are considered good if <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" id="M6"> <k:msub> <k:mrow> <k:mtext>C</k:mtext> </k:mrow> <k:mrow> <k:mn>1</k:mn> </k:mrow> </k:msub> </k:math> , <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" id="M7"> <m:msub> <m:mrow> <m:mtext>C</m:mtext> </m:mrow> <m:mrow> <m:mn>2</m:mn> </m:mrow> </m:msub> </m:math> , <o:math xmlns:o="http://www.w3.org/1998/Math/MathML" id="M8"> <o:msub> <o:mrow> <o:mtext>C</o:mtext> </o:mrow> <o:mrow> <o:mn>3</o:mn> </o:mrow> </o:msub> </o:math> , and <q:math xmlns:q="http://www.w3.org/1998/Math/MathML" id="M9"> <q:msub> <q:mrow> <q:mtext>C</q:mtext> </q:mrow> <q:mrow> <q:mn>4</q:mn> </q:mrow> </q:msub> </q:math> are low or minimum and if <s:math xmlns:s="http://www.w3.org/1998/Math/MathML" id="M10"> <s:msub> <s:mrow> <s:mtext>C</s:mtext> </s:mrow> <s:mrow> <s:mn>5</s:mn> </s:mrow> </s:msub> </s:math> is high or maximum. The catalyst prepared from plantain peel showed the best performance and ranked as the first one followed by Musa paradisiaca peel and cocoa pod husk catalysts which are ranked second. Thus, the VIKOR method can be useful for comparison and ranking purposes if there are a large number of data, and this may be expanded for thorough study by considering more criteria which may give more fruitful results.

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