Biodiesel Upgrading to Renewable Diesel over Nickel Supported on Natural Mordenite Catalysts

Abstract

In the present work the valorization of natural mordenite as a catalyst support was investigated. Natural mordenite of Greek origin was activated by acid treatment with an aqueous solution of HCl. This treatment led to a material with a high specific surface area (156 m2 g–1). Ni catalysts (10 wt % Ni) supported on activated mordenite were synthesized by incipient wetness impregnation (IWI), wet impregnation (WI), infiltration (INF), and deposition–precipitation (DP). They were evaluated for the biodiesel upgrading into renewable diesel via hydrotreatment. DP was proven to be the most effective preparation method. In fact, an almost total conversion of biodiesel and production of the highest amount of green diesel (14 wt % of the liquid product) was achieved over the catalyst prepared by DP. Its high efficiency was attributed to its enhanced specific surface area, better nickel dispersion (smaller size of crystallites), and the smaller amount of carbon deposits on its surface compared to the other catalysts of this series. When the DP method was adopted, nickel catalysts supported on activated mordenite were synthesized varying active phase loading in the range 10–30 wt %. The catalyst with the maximum nickel loading exhibited high specific surface area and the highest Ni surface area as well as a balanced population of weak and strong acid sites. These characteristics resulted in the highest efficiency for green diesel production (25 wt % of the liquid product) among the catalysts studied.

Mineral Montmorillonite Valorization by Developing Ni and Mo–Ni Catalysts for Third-Generation Green Diesel Production

“…Moreover, the catalytic efficiency obtained in the present study over nickel species supported on post-treated mineral montmorillonite was comparable to those obtained over nickel species supported on synthetic supports, though a rigorous comparison is very difficult to achieve due to the quite different evaluation conditions adopted in each case. Moreover, the comparison of the present results regarding the Mo–Ni bimetallic catalyst with the corresponding catalysts supported on various synthetic supports [ 20 , 21 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 ] showed that the Mo promoting action was also clearly manifested over nickel catalysts supported on mineral montmorillonite.…”

“…Several methodologies have been developed to minimize these problems involving the use of suitable supports, nickel loading, preparation methods and optimized experimental conditions (mainly reaction temperature and hydrogen pressure) [ 11 ], as well as modification of the structure of the supported nickel through development of nickel phosphide [ 44 , 45 , 46 ], nitride [ 47 , 48 ] or carbide catalysts [ 32 , 48 ]. Another very promising prospect for overcoming the above drawbacks and further increasing the efficiency of nickel catalysts is the use of promoters, among which molybdenum oxides are the most effective [ 20 , 21 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 ]. The literature survey indicated that excellent promoting action is observed in molybdenum oxides, mainly for catalysts with a Ni/(Ni+Mo) atomic ratio close to 0.85–0.95 [ 20 , 21 , 49 , 50 , 52 , 55 , 56 , 59 , 62 , 63 ].…”

“…[ 11 , 20 , 21 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 ]). Studies using cheap minerals as natural supports are very scarce [ 65 , 66 , 67 ]. Taking into account the fact that larger and larger amounts of catalysts will be required for green diesel production, the use of minerals seems to be attractive for decreasing the catalyst cost in the context of sustainable development and the cyclic economy.…”

“…This motivated a relevant research program undertaken by our group. In the frame of this program, we have successfully developed nickel catalysts supported on mineral palygorskite and mordenite, for the production of third-generation green diesel [ 65 , 66 , 67 ].…”

“…In a previous study, we investigated the influence of various parameters of the acid treatment of mineral montmorillonite (originating from soils in the Greek islands) on its physicochemical properties and catalytic efficiency in the transformation of limonene into high-added-value isomers and p-cymene [ 75 ]. This was done in the context of the development of catalysts/catalytic supports based on mineral mordenite and palygorskite for the production of green diesel [ 65 , 66 , 67 ] and green products [ 76 , 77 , 78 ], as well as on montmorillonite for the production of green products by valorizing renewable/waste raw materials [ 75 ].…”