Nopol catalytic production using non-wood forestry biomass: Technical, economic, and environmental aspects

Abstract

ABSTRACT : The use of natural compounds (and their derivatives) which exhibit excellent properties either as additives for the food industry or as pharmaceutical and cosmetic products; has increased research around their extraction, transformation, and purification processes. These compounds can be extracted from plant biomass, but some of them -whether they are used directly or as precursors of other compounds-, are not available in industrial quantities. The use of turpentine oil as a raw material in the synthesis of fine chemicals has been widely reported. One of these products is nopol that is a homoallylic alcohol obtained by the Prins reaction between β-pinene and the anhydrous formaldehyde polymer, known as paraformaldehyde in the presence of a Lewis acid. There is a current great interest in solving contemporary environmental problems, which have been the result of the historical and permanent action of human beings on natural resources. Humanity, to satisfy its needs, has been modifying the characteristics of the Earth, generating problems on a planetary scale, such as overpopulation, climate change, the humanization of the landscape, the extinction of species, erosion, desertification, the destruction of the jungle, the scarcity of fresh water and energy sources, among others. The use of catalytic processes is an important tool for mitigate the negative impact on the environment; furthermore, some important parameters have to be considered within the catalytic processes, such a catalyst performance targets, solvent choice, and operating conditions, on the environmental impact generated by the process. The impact of those parameters can be identified and weighted to take positive decisions in economy, environment and social aspects using life cycle assessment methodology, which is currently the most widely used EIA method, due to its applicability to a large number of processes, products and services. Considering the above, the purpose of this research work is present the environmental impacts evaluation of nopol synthesis by two alternative processes using the Life Cycle Assessment approach, which was developed according to the methodological structure of ISO standards with a “cradle-to-gate” scope, analysis that has not been reported so far in the literature. The Life Cycle Inventory was carried out according to primary and secondary data, where Aspen Plus® was used. Hierarchist ReCiPe (2016) was used as a methodology for the Life Cycle Impact Assessment using the SimaPro software with the Ecoinvent v3.9database. In the life cycle analysis is necessary to incorporate of 3 levels of activities. At the first level, the characteristics of the catalytic material for the synthesis of nopol, Sn/MCM-41, were studied. The characterization by X-ray diffraction, N2 physisorption analysis, TEM, NH3 - TPD and pyridine-FTIR, allowed to establish that the material is suitable for use in the reaction due to its mesoporous structure and the presence of Lewis acid sites, suitable for the Prins reaction. Catalytic test were carried out and the results show the viability of obtaining nopol from turpentine oil; it was found that with an ethyl acetate:β-pinene molar ratio of 1:0.5 the highest conversion of β-pinene in turpentine oil (56.3 %) is obtained when 17.6 % catalyst loading mg is used at 90 °C and a reactant molar ratio of 1:1; at these conditions the nopol selectivity nopol was 78.6%. The kinetic tests showed that a bimolecular surface reaction model under the Langmuir-Hinshelwood approach presents the greatest agreement with the experimental data. At a second level, the stages of a potential nopol synthesis process from turpentine oil were proposed, including four stages, from the extraction and separation of pine oleoresin to the final stage of purification of nopol. The technical analysis of the process allowed to establish the characteristics of the equipments as well as the associated mass and energy flows. A process improvement is reached when the solvent is recirculated. The third level, prior following LCA, was an economic study of the proposed process, to determine profitability. The study determined that the process would be highly profitable if part of the by-products generated in the various stages were commercialized. The results of the LCA allowed to establish that the potential impact categories of the nopol synthesis process are: Human carcinogenic toxicity, freshwater eutrophication, freshwater ecotoxicity, marine ecotoxicity, terrestrial ecotoxicity. The results showed that, in general, raw materials contributes to a much greater extent in the environmental burdens than production process phase. It was found that the hotspot of the process is the solvent; good environmental benefits were obtained when ethyl acetate was recirculated to the process. In each of the stages, the nopol synthesis process from turpentine oil was always in a comparative analysis with the alternative of using pure ß-pinene.