Abstract
Esterification between citric acid molecules and molecules of <i>Callistemon citrinus</i>, rice husk and <i>Garcinia dulcis</i> (pulp-peel and pips) were carried out such as the citric acid molecules quantities (moles) were negligible against to these raw materials’ reactive molecules quantities (moles). Results showed generally an important initial, total conversions (after 60 minutes) of citric acids molecules which confirmed the essential role of raw materials’ aromatics molecules characterized by their alkene organic-function titrated with HF-0.00261N (Hydrofluoric acid) as support of citric acid’s protonic acid H<sup>+</sup> catalyst (a portion of the carboxylic acids’ citric acid molecules used), support of non-ionic citric acid’s carboxylic acid (a portion of the carboxylic acids’ citric acid molecules used) and support of raw materials molecules reagents. So, the citric acid partial order of esterification of these used raw materials (<i>Callistemon citrinus</i>, rice husk and <i>Garcinia dulcis</i> (pulp-peel and pips)) with citric acid molecules were determined. Also, the brown citric acid equivalent monomers formed during esterification were calculated and their evolution were followed for all raw materials and results allowed to determine the citric acid’s protonic acid activities. In the same time, relationship between raw materials’ external specific surfaces, estimated by calculated and measured densities, and conversion or brown citric acid equivalent formed were established to conduct finally at the catalyst turnover. The variation of alkene organic-function concentration and/or quantities not only in solution but also in all by-products allowed to an ionic mechanism of these esterification with citric acid catalyzed by citric acid’s protonic acid H<sup>+</sup> (a portion of the carboxylic acids’ citric acid molecules used) supported on all raw materials’ aromatics molecules and fiber structures in glass-flask where not only carbonic acids molecules but also hydrogens molecules gas were emitted. Finally, seeing that a non-negligible alkene organic-function quantities were titrated on all by-products, their valorization as catalytic support of citric acid molecules polymerization were carried out and a procedure constituted principally with estimation of dichloromethane and hexane insoluble/soluble products, titration with HF-0.00261N of the unsaturated organic-function in hexane soluble products and titration with NaOH-0.05N of the black citric acid equivalent quantities evolutions were established and the results confirmed the ionic mechanism of esterification with citric acid molecules during which not only carbonic gas and hydrogen gas were emitted but also new monomers and each equivalent saturated products (characterized by their globally white color and unsaturated organic-function titrated with HF-0.00261N), new polymers and poly-polymers (characterized by their globally black color and titrated with NaOH-0.05N) different to that obtained with radical mechanism catalyzed by Lewis acid sites were formed.
Highlights
The first step the characterizations of raw materials such as their compositions and their sieving-characteristics as such as specific diameter, calculated volumetric mass, calculated external specific surfaces, measured density, measured external specific surfaces deduced by measured density
Noticed that the initial activities and the initial turnovers of citric acid’s protonic acids H+ for different raw materials decreased when initial dispersion increased as shown in the following figure and figure (Table 13). These exceptionnel results signalized the importance of alkene organic function as parameter and guided to create the «Total surface×[C=]initial - index» (Table 13). This index-value obtained by support external total surface multiplied by equivalent alkene organic-function concentration (Table 13) was calculated and it was noticed that at initial time (1’) catalyst-citric acid protonic acid-H+ turnovers and activities increased with this index-value except that at maximum index-value and at 60’ their values go down again and confirmed the alkene-support role to improve esterification and polymerization reactions with citric acid molecules; but at 60’ the formation of important PN-equivalent polymer could impinge upon catalyst-citric acid protonic acid-H+ sites and their deactivations (Table 13)
The previous results confirmed that raw materials’ aromatics molecules and its equivalent fiber structure-porosity characterized by their alkenes organic-function titrated with hydrofluoric acid HF-0.00621N and by their estimated external specific surfaces were efficient support for citric acids’ protonic acid-H+ catalyst and for the reagents during the esterification with citric acid molecules and their polymerization according to the experimental conditions itemized in the manuscript
Summary
The first step the characterizations of raw materials such as their compositions and their sieving-characteristics as such as specific diameter, calculated volumetric mass (density), calculated external specific surfaces, measured density, measured external specific surfaces deduced by measured density. The second step was the esterification reaction with citric acid molecules [1] which consisted to esterify the acid function of the citric acid molecules by rice husk’s, Garcinia dulcis’ and Callistemon citrinus’ organic molecules and to esterify the acid functions of their organic molecules by the citric acid molecules’ alcohol functions. Citric acid polymers and esters of citric acid molecules with rice husks’, Garcinia dulcis’ (pips – pulp-pell) and Callistemon citrinus’ organic molecules in glass-balloon auto-catalysed by citric acids’ protonic acids H+ were obtained with each by-products according to a mechanism. The quantifications of alkene-equivalent content of raw materials, esters solutions and by-products were done to evaluate their aromatics’ functions on surfaces and structures contributions as catalytic support of citric acid molecules esterification, citric acid protonic acid H+-catalyst and polymerization. By-products valorization was made as catalytic support to polymerize citric acid molecules in the same time a control-procedure was established to evaluate the polymerization evolution, to confirm and established the citric acid molecules polymerization on glass-material auto-catalyzed by citric acids’ protonic acid H+
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
