Optimized process for upgrading bio-oils of aromatic bases

Abstract

A process for preparing aromatic compounds from a liquid biofuel feedstock by introducing the feedstock into a hydroreforming stage in the presence of hydrogen and a hydroreforming catalyst that contains a transition metal of a group 3 to 12 element and an activated carbon, silicon carbide, silica, transition alumina, alumina-silica, zirconium oxide, cerium oxide, titanium oxide, or an aluminate of a transition metal substrate, to obtain a liquid effluent that contains an aqueous phase and an organic phase, a stage for hydrotreatment of the organic phase, a hydrocracking stage, recycling a fraction that boils higher than 160° C. in said hydrocracking stage, a separation into a fraction containing naphtha and a fraction that boils higher than 160° C., a stage for catalytic reforming of the fraction containing naphtha to obtain hydrogen and a reformate that contains aromatic compounds and a stage for separation of the aromatic compounds of the reformate.

Description

FIELD OF THE INVENTION[0001]This invention relates to a process for the production of aromatic compounds starting from liquids obtained from biomass and in particular starting from liquefied biomass obtained from the pyrolysis of biomass, also called bio-oil. In a more specific manner, the invention relates to a process for conversion of bio-oil into BTX-type aromatic compounds comprising a hydroreforming stage, followed by a hydrocracking stage in a fixed bed of rigorous conditions suitable for maximizing the production of light aromatic precursors and a catalytic reforming stage.STATE OF THE ART[0002]The aromatic compounds, in particular the C6-C8 aromatic compounds, i.e., benzene, toluene and xylenes / ethylbenzene (BTX), are major intermediate compounds in petrochemistry for the synthesis of resins, plasticizers and polyester fibers.[0003]The primary BTX production source is the catalytic reforming (or aromatizing according to English terminology) that is used by refiners for impr...

AI Technical Summary

Benefits of technology

[0022]One advantage of this invention is to provide a process, starting from a liquid feedstock that comprises at least one bio-oil, comprising a hydroreforming stage followed by a hydrotreatment stage and then a hydrocracking stage that made it possible to obtain, after separation, a naphtha fraction that is particularly well suited by its naphtheno-aromatic chemical nature and by its very small amount of impurities for the production of aromatic compounds by the catalytic reforming. Its unique structure imparts to it excellent reactivity relative to aromatization reactions.

[0023]In a first step, the hydroreforming stage makes it possible to obtain a liquid effluent that comprises at least one aqueous phase and at least one organic phase also containing large amounts of impurities: heteroelements of sulfur, nitrogen and oxygen as well as olefins and polyaromatic compounds. Before sending the light fraction (naphtha) of said organic phase into the catalytic reforming stage, it thus is necessary to carry out a hydrotreatment stage that makes possible the elimination of nitrogen-containing, oxygenated and sulfur-containing impurities, and then a stage of rigorous hydrocracking with recycling of the distilling fraction beyond 160° C. to maximize said naphtha. This hydrocracking stage thus makes it possible to obtain a significant naphtha fraction by cracking.

[0024]Likewise, the rigorous conditions of the hydrocracking stage make it possible to increase the naphtha fraction yield and therefore ultimately to increase the yield of aromatic compounds and hydrogen produced during the reforming.

Problems solved by technology

The bio-oils of pyrolysis have undesirable properties such as: (1) The corrosiveness due to their high content of water and organic acids; (2) A low specific calorific value because of the high content of oxygen, typically on the order of 40% by weight; (3) Chemical instability, in storage as well as under elevated heat conditions, due to the abundance of reactive oxygenated functional groups such as the carbonyl group, which can bring about polymerization during storage and consequently a separation of phases; (4) A viscosity and a tendency toward the separation of relatively high phases under high shearing conditions, in an injector, for example; (5) Solid coal particles obtained from pyrolysis, which will always be present in non-filtered bio-oils in small amounts such that the bio-oil / coal particles ratio is higher than 10:1 and preferably higher than 50:1.

However, said particles can cause the clogging of stationary internal combustion engines or can poison post-treatment catalysts.

All of these aspects are combined to make handling, shipping, storage and use of the bio-oils difficult and costly, thus making their integration into the systems and the current technologies for production of heat and energy very problematic.

One of the major obstacles to the direct catalytic hydrotreatment of bio-oils resides in their tendency to polymerize when they are subjected to higher temperatures than approximately 100° C., which gives rise to the formation of solids at higher temperatures than approximately 140° C., with consequences such as the clogging of feedstock lines, furnaces and reactors as well as the rapid deactivation of the catalyst, and even the clogging of the inlet of the reactor.

The difficulties encountered find their origin in the rapid thermal polymerization of bio-oil, which leads to the clogging of lines and reaction equipment as well as to rapid deactivation of the catalyst.

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