The exploitation of minerals originated from soils in Greece (mordenite, montmoril-lonite and palygorskite) was investigated for developing low cost catalysts devoted to catalyze the production of biofuels and green products. The research effort is illustrat-ed in the following seven research works. The first work deals with mineral mordenite originated from volcanic soils in Greek islands. This was treated with sulfuric acid aqueous solutions of different concentra-tions in order to study the influence of the concentration of the acidic solution on the physicochemical characteristics and the catalytic behavior of mineral mordenite. The activated samples were characterized using various techniques (N2-physisorption, XRD, ATR-FTIR, SEM-EDS, TEM, Microelectrophoresis, Equilibrium pH) and evaluated in the transformation of limonene into p-cymene at various temperatures and reaction times under atmospheric air. The relatively slight increase in the Si / Al atomic ratio, due to the removal of aluminum ions caused by acidic treatment, does not substantially affect the crystalline structure and fibrous morphology of the mor-denite, although to some extent it reduces its crystallinity. In contrast, the acidic treatment is bringing about the removal of sodium oxide located in the mouth of the micropores and small mesopores resulting to the impressive increase of the specific surface area and the development of acid sites via adsoption of H+ / H2O+ ions on the deliberated negative surface sites. These are bringing about the transformation of mineral mordenite into very active catalysts for the transformation of limonene into p-cymene. Τhe most promising activated sample resulted by treating the mineral palygorskite with a sulfuric acid aqueous solution of 2M. Over this sample, a limonene conversion at about 95% was obtained at 140ΟC, reaction time 2h and limonene to catalyst mass ratio equal to 15. A yield in p-cymene of 63% was obtained over this catalyst for reaction time equal to seven hours. Ιt has been confirmed that the limo-nene transformation into p-cymene involves two steps: a first relatively rapid catalytic step in which the limonene is transformed at the acid catalytic sites into isomeric ter-pinenes, terpinolenes and polymers and a slower non-catalytic step in which the above terpinenes and terpinolenes are converted into p-cymene by the atmospheric oxygen. In the second work the mineral mordenite was treated with aqueous solutions 2M of various acids (acetic, sulfuric, hydrochloric, and nitric acid) in order to examine the effect of the kind of acid on the physicochemical characteristics and catalytic behavior of the mordenite concerning the transformation of limonene into p-cymene. Activated samples were characterized by the aforementioned techniques and evaluated in the transformation of limonene into p-p-cymene at different temperatures and reaction times in air. As in the first work, acid treatment does not significantly affect the crys-talline structure and fibrous morphology of mordenite. In contrast, it resulted in the removal of oxides / bases of various cations, notably sodium, located at the orifices of the micropores smaller than one nanometer as well as from the elongated mesoporous / macropores formed between the mordenite fibers. The effect is more pronounced after treatment with solutions of strong acids (sulfuric, hydrochloric and nitrate). As in the previous work, this removal leads to a drastic increase in the specific surface area and in the creation of acidic, catalytically active, sites. The sample obtained after treatment with 2M hydrochloric acid solution proved to be the most active. Working at 140 °C, weight ratio of limonene to catalyst = 15 and reaction time of seven hours a yield of 65% in p-cymene was obtained. The development of a highly active catalyst using hydrochloric acid solution instead of sulfuric or nitric acid is important in terms of environmental protection because in this case removal of sodium as sodium chloride does not burden the environment.The prospect of using some of the activated mordenite samples of the two previous works as substrates in the synthesis of supported nickel catalysts for the conversion of vegetable oils to green diesel presupposes heating of the samples in air at relatively high temperature at some stages of the synthesis. It is therefore useful to know the change in the physicochemical characteristics of the activated mordenites brought about upon heating in air at 500 0C for 2h, conditions usually adopted in the synthesis. Thus, in the third work of the present research the effect of heating under these condi-tions on the physicochemical characteristics of the activated solids has been studied. The specimens after heating in air were characterized by the techniques of the two previous works and their physicochemical characteristics were compared with those of the corresponding unheated samples. Air heating was found not to affect the crys-talline structure of the samples, their fibrous morphology and the fibrous morphology of the mesopores. On the contrary, heating significantly reduces in all cases the very high acidity of the specimens obtained upon acidic treatment of the mineral mor-denite. This reduction was attributed to the partial destruction of the very strong acidic [Al - (OH) - Si] sites and is also supported by the reduction in oxygen content of the samples. For the mordenite activated with hydrochloric acid solution, heating does not cause changes in the porous structure, leaving virtually unaffected the high specific surface area achieved upon acid activation. In contrast, the heating for the specimens activated with sulfuric and acetic acid results in partial destruction-closure of micropores and consequently in a significant reduction of the specific surface area. Finally, the heating caused an increase in the specific surface area in the sample activated with nitric acid. The high specific surface area and the moderate acidity determined after heating the sample activated with hydrochloric acid solution make this material promising for the development of supported nickel catalysts for green diesel production, because these catalyst characteristics are desirable for the reaction. In the fourth work, the research effort was extended in exploiting mineral montmoril-lonite for developing catalysts for limonene transformation into high value added products (limonene isomers and p-cymene). Eight samples of activated montmorillo-nite were prepared by treating mineral montmorillonite with aqueous solutions of HCl and HNO3 in order to investigate the influence of several treatment parameters (con-centration of the solution, time of treatment, kind of acid) on the physicochemical characteristics and catalytic behavior. The samples were characterized using various techniques used in the previous works and evaluated in the transformation of limo-nene to isomers and p-cymene utilizing atmospheric oxygen as a green oxidant. The acid treatment caused the removal of sodium and calcium ions from the interlayer re-gions of the triple layers of montmorillonite as well as phases of these elements (for example calcium carbonate) from interparticle regions, but without significant effect on the structure of the triple layers per se. In contrast, the acid treatment brings about the reorganization/dislocation of the triple layers inside a plate -shaped particle causing the development of small mesopores, mainly in the range of 3-3.5 nm, and conse-quently the increase in the specific surface from 62 to 155 m2/g. In parallel, the re-moval of the sodium and calcium ions/phases brings about the development of nega-tively charged surface sites. These are transformed into Bronsted acid sites by adsorb-ing hydronium ions (H3O+) which catalyze the conversion of limonene into interme-diate isomers and finally into polymers. The intermediate isomers are transforming into p-cymene and additional “polymers” through a catalyst-free mechanism, in the presence of atmospheric oxygen. Efforts to optimize the reaction conditions have shown that at 100 0C and reaction time of 20 hours, limonene is converted into high value added products by more than 90%, while the undesired polymer produced is below 1%. The low reaction temperature (100 0C), which can be easily achieved even with the use of solar energy collectors, the use of limonene as a renewable reagent, the use of montmorillonite as a natural catalyst and the use of atmospheric oxygen as green oxidant reduce the environmental footprint of the proposed process rendering it substantially green.In the fifth work of the present research we developed very active nickel catalysts supported on mineral palygorskite originated from Greek soils for the transformation of waste cooking oils (WCO) into green diesel. A series of supported catalysts of var-ying Ni content in the range 10-60 wt % Ni has been prepared. The catalysts were synthesized following the deposition – precipitation method and their physicochemi-cal characteristics were determined using various methods (N2 adsorption–desorption isotherms, XRD, FTIR, SEM-EDS, TEM-HRTEM, XPS, H2-TPR, NH3-TPD, micro-electrophoresis, equilibrium pHs).The evaluation of the catalysts in the aforementioned transformation was performed at 310oC, hydrogen pressure 40 bar, ratio of reactant volume to catalyst mass equal to 100mL/1g and free solvent conditions using a semi-batch reactor. Granular nickel supported nanoparticles, very small NiO supported nanoparticles and surface nickel silicates [NiSiO3 and/or Ni3Si2O5 (OH)4] are formed on the palygorskite surface whereas the main characteristics of the mineral palygorskite(crystal structure, texture, fibrous morphology) remained intact. In the sample with the minimum nickel loading nickel silicates and very small Ni/NiO na-noparticles are mainly developed inside the micropores and the small mesopores of palygorskite. As the nickel content increases, the surface ratio Ni2+ / Ni0 decreases. This is due to the decrease of the relative concentration of the nickel silicates. Moreo-ver, larger and larger nickel nanocrystals are developed inside increasingly larger mesopores of palygorskite resulting in a progressive decrease of the nickel dispersion. A like volcano trend, maximized in the catalyst containing 40 wt % Ni, was thus ob-served for the nickel surface exposed per gram of catalyst as a result of two opposite trends (increase in the nickel content, decrease in the nickel dispersion). Moderately strong acid sites are developed on the surface of the nickel phases. The supported nickel nanoparticles are very active in the transformation of waste cooking oils into green diesel. Normal alkanes (n-C15, n-C16, n-C17, n-C18) and intermediates mole-cules (fatty acids, octadecanol and esters resulting from esterification of fatty acids with fatty alcohols) have been detected. The conversion of the WCO was about 100% over all catalysts. The green diesel content in the liquid reaction product depends mainly on the nickel surface exposed per gram of catalyst. It follows a volcano like trend which is maximized (81.9 wt %) over the sample with 30 wt % total Ni loading. Taking into account the very high ratio of WCO volume to catalyst mass and that the evaluation of the catalysts was performed under solvent free conditions this value is actually very high. Thus, the successful use of mineral palygorskite for developing promising “natural catalysts” for green diesel production has been demonstrated. In the sixth work of the present contribution it was studied the transformation of re-sidual fatty raw materials (RFRMs) into n-alkanes in the diesel range (third generation green diesel). The RFRMs studied were waste cooking oils (WCO), fatty acid distil-lated (FAD), oil extracted from spent coffee grounds (SCGO) and oil from chicken fat (CHO)]. The transformation of biodiesel into green diesel was also studied in the context of an approach where RFRMs should first transformed into biodiesel and then into green diesel. The most active catalyst of the previous work, namely the catalyst contained 30%wt of nickel supported on palygorskite (30Ni/MP) was used in all ex-periments. The evaluation experiments were taken at 3100C, 40bar hydrogen pressure, volume of RFRM to catalyst mass 10ml/0.33g and reaction time up to 4h. Important physicochemical characteristics of the RFRMs were determined in the present work, like iodine and saponification numbers, acidity, humidity and kinematic viscosity. These were correlated with the composition of RFRMs and, in some cases, with the conditions and procedure of their preparation. As in the previous work, normal alkanes in the diesel range (n-C15, n-C16, n-C17, n-C18) and intermediates molecules (fatty acids, octadecanol and esters resulting from esterification of fatty acids with fatty alcohols) have been detected in all cases. A conversion equal to 100% was obtained when WCO, FAD and CHO were used as reactants. This is equal to 88% when using SCGO. The composition of the reaction liquid mixture in total n-alkanes (green diesel), follows the order: 30Ni/MP(CHO) 98%, 30Ni/MP(WCO) 83%, 30Ni /MP(FAD) 68% and 30Ni /MP(SCGO) 10%. Biodiesel is transformed into green die-sel much faster than RFRMs. The catalyst use does not affect the structure of palygor-skite, its fibrous morphology and the uniform nickel distribution at milimetric scale. In contrast, the catalyst use is causing a change in the relative surface concentration of the supported nickel phases [Ni0, NiO, Ni3Si2O5 (OH)4 and /or NiSiO3] as well as a slight shift in the size distribution of the Ni0 and NiO supported nanoparticles towards smaller nanoparticles. The aforementioned activity trend was rationalized in terms of the relative surface concentrations of the supported nickel phases as well as on the base of some molecules present in the RFRMs eventually bringing about catalyst de-activation.The seventh work presents the results of an extensive geographical survey carried out in Greece in the context of the present research. This concerns: (a) greek minerals, in particular those used in the present study, (b) waste cooking oils provided from cater-ing companies, (c) estimates for domestic consumptions of plant oils and (c) lligno-cellulosic biomass of agricultural / forestry residual raw materials estimated from open sources. The geographic information systems methodology and spatial analysis techniques were used concerning the residual raw materials. For this reason geographic information systems, their geological and geographical applications, spatial analysis and basic spatial autocorrelation indices as well as spatial analysis software, data capture and data collection methodology were presented prior to the detailed presentation of the results. It has been shown that there are sufficient quantities of minerals in Greece for all applications studied in the context of development of active catalysts. The prices of the minerals as well as their relatively easy activation developed in this work make them quite competitive with respect to the entirely synthetic catalysts. The quantities of the waste cooking oils and the residual house oils represent a very important, partially untapped, source of residual raw materials that can be used to produce green diesel in the context of a growing cycle economy. The significant concentrations of these materials we found in the two metropolitan centers are justified both by the existence of municipalities with citizens of high income and the very strong geographical proximity that "attracts" spatial autocorrelation indices. Due to the relatively short distances and the very high concentrations of waste cooking oils/ residual house oils in these metropolitan areas, a strategy involving recycling at source, neighborhood level, and central treatment plants could be adopted. The investigation of the spatial distribution of agricultural / forestry residual biomass indicated its geographical dispersion and the heterogeneity of the distributions. The quantities recorded are significant. However, the high spread and the cost of collecting and transporting biomass to central processing plants would be prohibitive. This advocates for smaller, well dispersed, industrial units in combination with the fragmentation of biomass into small pieces and the on-site loading on “mobile – fast pyrolysis reactors” for producing bio-oils. These mobile reactors may transport bio-oil to the aforementioned static units or refineries for upgrading bio-oils into bio-fuels through hydrotreatment. Thus, it can be avoided the transportation of large amounts of water, being inside the original biomass. This will prevent large quantities of water being contained in the original biomass being avoided as it is removed during rapid pyrolysis.
