METHOD FOR WHOLLY OR PARTLY HYDROTREATING THE BIO-OILS PRODUCED BY DIFFERENT BIOMASSES. PRODUCTION FROM THESE BIO-OILS OF DIRECTLY USABLE HEATING OR ENGINE FUELS, OR TERNARY OR QUATERNARY EMULSIONS.
KNOWLEDGE OF THE PROPERTIES, IN PARTICULAR THE STORAGE AND COMBUSTIBILITY PROPERTIES OF THE BIO-OILS AND THEIR DERIVATIVES.
Stability of pyrolytic oils necessitates 2-step processing. A low temperature hydrotreatment enables stabilization through reactions like olefin, carbonyl and carboxylic groups reduction. Further hydrotreatment aims at hydrodeoxygenation of phenols and hydrocracking of larger molecules. Essentially, the work has been centred on this final hydrorefining step.

It was found that sulphided hydrotreating catalysts were well adapted to pyrolytic oils hydrotreatment. Nickel based catalysts showed higher hydrogenating and hydrocracking activities than cobalt based catalysts. The advantages were a higher hydrogen carbon ratio and a larger conversion of heavy fractions to lighter hydrocarbon. Disadvantages in total hydrogen consumption and loss of organic material in the form of gaseous products.
Pyrolysis oil composition and specially acidity had a great influence on the polymerization tendancy during hydrotreatment. Coprocessing pyrolytic oils with an hydrogen donor solvent was beneficial due to free radical stabilization and hydrogen transfer to the catalyst surface and hydrogen pressure higher than 8 MPa caused carbon loss as gases to increase from 8% to 18% at 15 MPa.

Research is directed towards a better understanding of the reactions and mechanisms involved in hydrodeoxygenation of pyrolytic oils. The influence of pretreatments on further treatment is of huge importance. Optimization of this step will lead to stabilization of pyrolytic oil and control of polymerization tendency during treatment. Optimal pretreatment would diminish catalyst deactivation as well.

Based on the laboratory data, a very preliminary technoeconomical evaluation was made. 50 weight yields in hydrocarbons for deep hydrorefining of pyrolytic oils can be expected. Nevertheless, a moderate hydroconversion with partial elimination of oxygen would be, economically, more advantageous.
IN A PREVIOUS WORK (CONTRACT NUMBER EN3B-0022-B) IT HAS BEEN SHOWN THAT THE PROPERTIES OF BIO-OILS PRODUCED BY PYROLYSIS OF BIOMASS CAN BE DRAMATICALLY IMPROVED BY HYDROTREATING. IN PARTICULAR IT IS POSSIBLE TO ELIMINATE OXYGEN, RESPONSIBLE OF A NUMBER OF BAD CHARACTERISTICS OF THE OILS, BUT ALSO NITROGEN AND SULFUR.

IN THE PRESENT WORK, IT IS INTENDED TO EXTEND THE STUDY TO OTHER FORMULATIONS OF CATALYSTS WITH THE AIM OF OPTIMISE THE DIFFERENT FUNCTIONS INVOLVED IN THE REACTION, MAINLY THROUGH THE STUDY OF THE INFLUENCE OF ACIDIC AND HYDROGENATING PROPERTIES ON THE ACTIVITY OF THE CATALYSTS AND WITH THE AIM OF DEFINE THE OPTIMAL REACTION CONDITIONS LEADING AT THE SAME TIME TO HYDRODEOXYGENATION AND TO HYDROCRACKING OF HEAVY COMPOUNDS.
DEACTIVATION OF THE CATALYSTS DEMANDS A VERY CAREFULLY STUDY, BECAUSE, BESIDE HEAVY COMPOUNDS THE BIO-OILS CONTAIN HIGHLY DISPERSED CHAR PARTICLES.
THIS CHAR IS FOUND TO AFFECT ACTIVE SITES (BLOCKING) AS WELL AS PHYSICAL PROPERTIES, NAMELY PORE STRUCTURE AND SURFACE, RESTRICTING ACCESS TO PORES. THE CHEMICAL ANALYSIS OF THE OIL IS A MAJOR PROBLEM BECAUSE OF THE PRESENCE OF A MULTIPLICITY OF CHEMICAL FUNCTIONS.
A GOOD KNOWLEDGE OF COMPOSITION IS NEEDED IN ORDER TO MAKE A MORE CORRECT EVALUATION OF THE HYDROTREATMENT. LIQUID CHROMATOGRAPHY AND SPECTROPHOTOMETRIC TECHNIQUES (UV, IR, RMN) WILL BE USED TO CHARACTERISE THE OIL.