Process for the production of fuel and chemicals from waste materials by utilizing carbon dioxide-rich feedstock

Abstract

Process for the production of fuels and chemicals from waste materials comprising the steps of: a) Oxidative gasification of said waste materials to produce synthesis gas; b) Cleaning of said synthesis gas; c) Production of hydrogen and oxygen streams by electrolysis of steam or water; d) Addition of the hydrogen produced in said step c) to said synthesis gas to modify its composition to achieve a desired ratio (H2-CO2 / (CO+CO2); e) Use of said synthesis gas to produce methanol with the methanol synthesis and / or hydrocarbons with the Fischer – Tropsch synthesis.

Description

[0001] PROCESS FOR THE PRODUCTION OF FUEL AND CHEMICALS FROM WASTE MATERIALS BY UTILIZING CARBON DIOXIDE-RICH FEEDSTOCK

[0002] The present invention relates to a process for the production of fuels and chemicals from waste materials by utilizing carbon dioxide-rich feedstock. The invention also relates to an apparatus for carrying out this process.

[0003] BACKGROUND OF THE INVENTION

[0004] The CO2 concentration in the atmosphere has overcome, in 2016, the 400 ppm after having remained between 100 ppm and 300 ppm for thousands of years before, during and after the industrial revolution periods.

[0005] The reduction of greenhouse gases (GHG) concentration, whose main components are CO2 and methane, is crucial and requires a systemic approach for an efficient use of the primary energy sources in which the percentage of renewable energy needs to be increased while the share of fossil sources need to be reduced.

[0006] From another perspective, CO2 is also a synthon but being a highly stable molecule, its transformations require a relevant energy input and / or complex biological cycles.

[0007] PRIOR ART

[0008] Currently, the synthesis gas (syngas) with low H2 vs CO ratios is obtained with steam-CO2 reforming technologies utilizing large amounts of CO2 and often referred to as dry reforming technologies. These technologies are limited in their operation windows by carbon formation reactions.

[0009] As mentioned above, in steam-CO2 reforming, particularly in high pressure conditions, the occurrence of carbon formation reactions onto the catalyst surfaces cause limitations in the operation conditions; these limitations particularly affect the possibility of lowering or avoiding the steam content in the reactant mixtures while operation in low steam vs carbon (moles of carbon in the hydrocarbon feedstock) would be particularly advantageous for producing synthesis gas with low H2 vs CO ratios.

[0010] In other words, the production processes utilizing steam-CO2 reforming and particularly dry reforming are limited by thermodynamic and kinetic affinity towards carbon formation reactions occurring at the surfaces of the catalytic species.

[0011] Processes for the production and use of synthesis gas (syngas) from waste materials are known in the art.

[0012] WO 2008130260 Al discloses a waste to liquid hydrocarbon refinery system designed to convert municipal and industrial wastes, biomass and other carbon containing feedstock into diesel, gasoline and other products. The system involves a high temperature liquid iron bed that generates row syngas from solid and liquid feedstocks and a very high temperature plasma to convert contaminants in the row syngas into ions.

[0013] WO2022078915 Al discloses a process for producing synthesis gas from waste materials and / or biomass through the steps of: i) gasifying with an oxygen containing feed waste materials and / or biomass materials to produce a first raw synthesis gas stream, ii) passing the raw synthesis gas into a second reaction zone producing partial oxidation reactions, iii) decontaminate the obtained synthesis gas stream, iii) combine the obtained synthesis gas with an H2 flow obtained from a steam electrolysis utilizing renewable electric energy sources, iv) subjecting the obtained synthesis gas mixture to a conversion step that could be constituted preferentially by a Fischer-Tropsch (F-T) process, but also by other conversion processes such as NH3 synthesis or methanol synthesis.

[0014] US Pat. N° 6,455,011 B l discloses a method and apparatus for treating wastes into two-stage gasification which recovers metals or ash content in the wastes in such a state that they can be recycled and gases containing carbon monoxide (CO) and hydrogen gas (H2) for use as synthesis gas for ammonia (NH3) or the other chemicals production.

[0015] CN103242134 discloses an invention related to household garbage treatment method, where the waste is subjected to a thermal cracking to form mixed combustible gases containing CO, CO2, H2, nitrogen (N2) and inert argon (Ar) by a full gasification process. The syngas is purified and separated, and then are used for synthesizing methanol and / or dimethyl ether (DME), generating power and synthesizing urea. The system produces significant amounts of tar which be disposed or used.

[0016] US 2014 / 0364517 Al discloses a process and system for producing liquid and gas fuels and other useful chemicals from carbon containing source materials comprises cool plasma gasification and / or pyrolysis to produce syngas which in turn could be used for producing hydrocarbon, methanol, ammonia, urea and other products. The system is carbon neutral but is relatively complex and expensive, requires relatively large amount of energy for the plasma gasification and has quite high cost for maintenance.

[0017] There remains, therefore, a need for carbon neutral process, apparatus and system for producing fuels and chemicals from carbon containing wastes as municipal, refuse derived fuels (RDF) and industrial wastes. RDF is a fuel produced by shredding and dehydrating solid waste (MSW) with a waste converter technology. RDF consists largely of combustible components of municipal waste such as plastics and biodegradable waste.

[0018] US 2011 / 160313 discloses a method for improving the overall carbon conversion efficiency of a gasification process, wherein an organic feedstock, which is agricultural or animal waste, introduced into a gasifier, is converted in syngas that is, in turn, utilized for a chemical production process in a chemical production reactor. This invention provides an improved carbon conversion efficiency by recycling the methane -rich purge gas back to the gasification reactor where the methane -rich purge gas back is converted to syngas via the steam-methane reforming reaction. Additionally, there remains a need for a process, apparatus and system that has minimal or zero CO2 and GHG emissions.

[0019] EP 3 433 341 Bl discloses a method for producing methanol from syngas originated from wastes gasification. The process includes a plurality of high temperature converters and corresponding-pretreatment units, followed by purification sections of the raw syngas, to obtain a composition useful for the methanol synthesis. More in detail the document describes a methodology for purifying the syngas from the contaminants (i.e., metallic materials, as iron, lead, chromium, copper, chlorine compounds mainly present as HCI, Nitrogen compounds mainly present as HCN and NH3, Sulphur compounds mainly present as H2S, COS and CS) and after the syngas purification steps the document describes process solutions for obtaining a syngas composition suitable to the methanol synthesis.

[0020] More in detail, the described syngas purification comprises an acidic scrubbing, a basic scrubbing, a mist removal with a Wet Electrostatic Precipitator (WESP); while the syngas composition is adjusted for achieving a ratio (H2-CO2) / (CO+CO2) ca 2 v / v by employing a water gas shift step (WGS) described with equation [3] in the following of the document, and CO2 removal sections.

[0021] US 2013 / 0149767 Al describes a process for the conversion of carbon-based materials combining direct liquefaction via hydrotreating and indirect liquefaction via non-catalytic partial oxidation (POx), thereby producing syngas which is then converted into hydrocarbons via a Fischer-Tropsch (F-T) process. There is no disclosure of using a short contact time catalytic partial oxidation process (SCT-CPO) to produce syngas and of recycling purged gas or tail gases from the F-T process to use them as feedstock in the SCT-CPO process.

[0022] US 2010 / 294994 Al describes a process for the production of syngas by means of a reactor provided with four sections (I, II, III, IV, Fig. 2) in which the first and the second zones include: i) a device for the nebulization of a liquid hydrocarbon feedstock and ii) a nebulization and mixing chamber for providing a reactant mixture that is subsequently converted into synthesis gas in a reaction zone included in section III having a cylindrical shape and layered catalytic structures for converting the mixture of nebulized liquid hydrocarbons with the oxidant flow. Noteworthy, the state-of-the-art processes include at least two GHG and concentrated CO2 emission points that cannot be avoided. SUMMARY OF THE INVENTION

[0023] An aspect of the present invention is a process to produce methanol and / or hydrocarbons from waste materials comprising the steps of: a) Oxidative gasification of said waste materials with production of a main synthesis gas stream; b) Cleaning of said main synthesis gas stream produced in said step a); c) Production of hydrogen and oxygen streams by electrolysis of steam or water; d) Addition of the hydrogen produced in said step c) to said main synthesis gas stream produced in said step a) to modify its composition to achieve: i) a ratio (H2-CO2 / (CO+CO2) from 1.5 to 2.5 v / v, preferably from 1.7 to 2.3 v / v, more preferably from 1.8 to 2.2 v / v, useful for the methanol synthesis, thereby avoiding any CO2 separation from the main syngas stream; or ii) a ratio H2 / CO from 1.5 to 2.5 v / v, preferably from 1.7 to 2.3 v / v, more preferably from

[0024] 1.8 to 2.2 v / v, for use in the production of hydrocarbons by means of the Fischer- Tropsch synthesis thereby avoiding any CO2 separation from the main syngas stream; e) use of said synthesis gas with the modified composition of said step d) i) to produce methanol by the methanol synthesis or use of said synthesis gas with the modified composition of said step d)ii) to produce hydrocarbons by the Fischer-Tropsch synthesis; f) use of gases purged from said oxidative gasification step a) and from one or more of said steps b), c) and d) as a feedstock of a SCT-CPO process to produce an additional stream of synthesis gas, which is then combined with said main synthesis gas stream and fed to said step e) for the synthesis of methanol and / or hydrocarbons, wherein said feedstock further comprises one or more of recycle gases, tail gases, purge gas of the F-T synthesis, recycle gases of the methanol synthesis and one or more of natural gas and / or a hydrocarbon feedstock having a CO2 content of at least 5% v / v.

[0025] Another aspect of the invention is an apparatus for producing additional synthesis gas utilizing the recycle gases and / or the tail gases of the methanol synthesis and Fischer Tropsch process defined above and the oxygen produced from the electrolysers, comprising a short contact time catalytic partial oxidation reactor including a first portion having a cylindrical shape consisting of an inlet a mixing zone and a thermal shield zone, a second portion containing a catalytic bed having a truncated cone shape, and a third portion having a cylindrical shape with a diameter greater than the diameter of said first cylindrical portion, followed by a second thermal shield zone, wherein: a) in said second portion having the shape of a truncated cone the upper base is smaller than the bottom base; b) said upper base of said truncated cone is joined to said first cylindrical portion and said bottom base is joined to said third cylindrical portion; and c) the external angle (a) of said truncated cone at the upper base is lower than 85° and preferably lower than 75°.

[0026] The term “waste materials” designates any carbon containing waste of organic nature, including municipal waste, biomass, agricultural waste, animal waste, plastics.

[0027] The term “short contact time catalytic partial oxidation” (SCT-CPO) has a well-defined meaning either in the scientific, technical, and patent literature. As used in the present invention, however, certain aspects are quite specific for what concerns the combination of the characteristics of the reactor and the operation conditions.

[0028] The term “electrolysis of steam” or “steam electrolysis” means the High-temperature electrolysis; as known in the field.

[0029] The term “associated gas” designates a gas produced as a byproduct of the production of crude oil. Associated gas is generally regarded as an undesirable byproduct, which is either reinjected, flared, or vented.

[0030] The term “off-gas” designates a gas produced as a byproduct of a chemical process.

[0031] The term “tail gas” designates gases and vapors released into the atmosphere from an industrial process after all reactions and treatments have taken place.

[0032] DETAILED DESCRIPTION OF THE INVENTION

[0033] The present disclosure concerns the conversion of waste materials into fuels and chemicals with process schemes and technologies allowing the avoidance of CO2 and the other GHG emissions. In addition, a CO2 containing gas can also be integrated in the innovative process solutions for providing a pathway for CO2 utilization and its conversion in fuels and / or chemicals.

[0034] More specifically, the disclosure describes process schemes, methods and apparatus integrating the following unit operations:

[0035] - high temperature gasification of waste materials (e.g., municipal wastes, refuse derived fuel, industrial or agricultural wastes);

[0036] - short contact time - catalytic partial oxidation (SCT-CPO) of reactant mixtures containing the recycle gases and / or the tail gases and / or the purge gases produced in the F-T synthesis and / or the Methanol synthesis processes and possibly additional CO2 rich feedstock; - steam or water electrolysis producing H2 and O2 streams in way in which: a) the O2 is utilized in the waste gasification and / or in the SCT-CPO steps for producing the synthesis gas, b) the H2 is added to the synthesis gas for achieving the compositions useful to the F-T and / or to the methanol synthesis.

[0037] This syngas produced with these unit operations is then utilized to obtain:

[0038] - linear or branched liquid hydrocarbons and / or olefins useful as raw materials in the chemical industry through the F-T synthesis,

[0039] - methanol and its derivatives (e.g. fuels through the methanol to gasoline - MTG, olefins trough the methanol to olefins - MTO processes or other products obtained through methanol carbonylation reactions)

[0040] The Fischer-Tropsch (F-T) process for obtaining liquid hydrocarbons and / or olefins and the methanol synthesis require the initial conversion of wastes and of the CO2 rich streams into synthesis gas mixtures with different features.

[0041] In case of the methanol synthesis, the ratio (Fh-CCh CO+CCF) between the main components of the synthesis gas need to reach varies from 1.5 to 2.5 v / v, preferably from 1.7 to 2.3 v / v, more preferably from 1.8 to 2.2 v / v.

[0042] In the case of the F-T processes, the H2 / CO ratio inside the synthesis gas typically needs to be from 1.5 to 2.5 v / v, preferably from 1.7 to 2.3 v / v, more preferably from 1.8 to 2.2 v / v.

[0043] In addition, in both cases, the amount of the other molecules inside the synthesis gas needs to be contained at low percentages (typically the CH4 content typically needs to be lower than 3% v / v in and the CO2 content must be minimized possibly at values below 5%).

[0044] Currently, when the main syngas source is constituted by waste gasification processes, these synthesis gas characteristics are achieved by utilizing water gas shift reactors for increasing the H2 content and decreasing the CO in the synthesis gas, specific CO2 removal sections (typically amine washing sections or membrane separation sections), pressure swing adsorption units (PSA) and by purging some of the recycle gases of the methanol or the F-T synthesis loops.

[0045] These operations result in a release of CO2 and GHG into the atmosphere.

[0046] Here we disclose that the combined use after waste gasification of (a) electrolysis and (b) SCT-CPO allows the avoidance of the emissions of CO2 and of other GHG streams.

[0047] More in detail It is reported that this result is obtained by utilizing Alkaline Electrolysis (AE) either with liquid or solid electrolytes, or Polymer Electrolyte Membrane Electrolysis (PEME), or Solid Oxide Electrolyte Cells (SOEC) and SCT-CPO reactors.

[0048] These last SCT-CPO reactors allow the utilization of: i) the recycle loops and the tail and / or the purge gas flows of the F-T or the Methanol synthesis processes and in case it would be considered advantageous; j) ii) other gaseous hydrocarbon feedstock such as NG and particularly other CO2 rich hydrocarbon feedstock to produce additional synthesis gas.

[0049] The process solutions according to the invention allow the utilization of the co-produced O2 stream associated to the H2 production with steam / water electrolysis either in the SCT-CPO and / or in the waste gasification units.

[0050] Noteworthy, it is reported that the SCT-CPO reactor is particularly advantageous for utilizing the recycle gases, tail gases and / or the purge gas streams of the methanol synthesis or of F-T synthesis loops since the high-temperature catalytic reactions produced with this technology, are extremely selective towards partial oxidation products.

[0051] Noteworthy, the recycle gases, tail gases and the purge gas compositions either of the F-T synthesis and of the methanol synthesis contain relevant amounts of unconverted H2 and CO molecules and relatively minor amounts of small gaseous hydrocarbons and CO2.

[0052] In addition, SCT-CPO reactors are particularly suitable for utilizing CO2 rich feedstock since the reactivity features are not limited by the carbon formation reactions affecting the steam- CO2 reforming reactors, the autothermal reactors, the non-catalytic partial oxidation reactions. It has been found that the presence of the CO2 in the SCT-CPO reactor has an inhibiting effect towards the parasitic gaseous phase radical reactions that, particularly at high pressure conditions, are the only reactions that could lead to unsaturated hydrocarbon molecules formation that could possibly evolve and decompose producing carbonaceous deposits.

[0053] More in detail, with the here described SCT-CPO reactor solutions, we have found that: i) the hydrocarbons content of the recycle loop and / or the purge gas produced either in the methanol synthesis or in the F-T synthesis can be drastically decreased through partial oxidation reactions producing a synthesis gas with high H2 and CO content; ii) the presence of CO2 in the reactant mixture strongly inhibits the propagation of the unselective radical reactions inside the reactant / product gaseous mixture progressing inside the SCT-CPO reactor; iii) the CO2 participates the heterogeneous chemistry inside the catalytic bed after that relevant amounts of hydrocarbons have been already transformed into partial oxidation products that are the main desired components of the synthesis gas; iv) the CO2 reacts inside SCT-CPO reactors with the produced H2 through an internal RWGS in the last section of the SCT-CPO reactor catalytic bed.

[0054] Noteworthy, only the SCT-CPO reactor solutions according to the invention are effective for producing these reactivity features while other CPO reactors utilizing tubular and fixed bed reactors, fluidized bed, moving beds, or bubbling bed reactors cannot be applied in the conditions here described.

[0055] Moreover, it is noted that the features of the SCT-CPO technology are discussed in numerous patent documents, including WO2016016257 (Al), WO2016016256 (Al), WO2016016253 (Al), W02016016251 (Al), WO 2011151082, WO 2009065559, WO 2011072877, US 2009127512, WO 2007045457, WO 2006034868, US 2005211604, WO 2005023710, WO 9737929, EP 0725038, EP 0640559.

[0056] Extensive technical and scientific literature has also been produced and mentioned in the following references.

[0057] “Issues in H2 and synthesis gas technologies for refinery, GTL and small and distributed industrial needs”; Basini, Luca, Catalysis Today, 106 (1-4), p. 34, Oct 2005

[0058] “Fuel rich catalytic combustion: Principles and technological developments in short contact time (SCT) catalytic processes”; Basini, L.; Catalysis Today, 117 (4), 384-393; DOI: 10.1016 / j.cattod.2006.06.043 Published: 15 October 2006

[0059] “Natural Gas Catalytic Partial Oxidation: A Way to Syngas and Bulk Chemicals Production | IntechOpen”; G. laquaniello, E. Antonetti, B. Cucchiella, E. Palo, A. Salladini, A. Guarinoni, A. Lainati and L. Basini; http: / / dx.doi.org / 10.5772 / 48708

[0060] “Short Contact Time Catalytic Partial Oxidation (SCT-CPO) for Synthesis Gas Processes and Olefins Production”; L.E. Basini, A. Guarinoni, Ind. Eng. Chem. Res. 2013, 52, 17023-17037; https: / / doi.org / 10.1021 / ie402463m.

[0061] The term “short contact time catalytic partial oxidation” (SCT-CPO) has then a well-defined meaning either in the scientific, technical, and patent literature but the solutions here adopted are quite specific for what in concerns the combination of the characteristics of the reactor, of the catalyst species and of the operation conditions.

[0062] The invention is described also with reference to the accompanying drawings, wherein:

[0063] Figure 1. Simplified state-of-the art process scheme described in EP 3,433,341 B l that describes a method for producing methanol from syngas originated from wastes gasification. The process determines two main CO2 and GHG emission points that cannot be avoided by recycling these gases into the syngas generation reactors. Figure 2. Simplified block diagram process scheme in which the syngas production and cleaning from waste materials is utilized for High Temperature (HT) and Low Temperature (LT) F-T synthesis for originating a plurality of hydrocarbons.

[0064] Figure 3. Simplified block diagram process scheme describing a method for producing methanol from syngas originated from wastes gasification. The process avoids the utilization of a WGS and of a CO2 removal unit by including a steam or water electrolyzer system that produces the H2 useful for the achievement of an appropriate (H2-CO2) / (CO+CO2) ratio in the synthesis gas and consequently avoids one major CO2 emission point. The steam / water electrolysis unit also provide an 02 stream for the waste gasification step.

[0065] Figure 4. Simplified block diagram process scheme describing a method for producing hydrocarbon fuels and chemicals from syngas originated from wastes gasification. The process solution by including a steam electrolyzer unit that produces the H2 allows the achievement of an appropriate H2 / CO ratio in the synthesis gas and avoids the utilization of a CO2 removal unit and consequently one major CO2 emission point. The steam / water electrolysis unit also provide an O2 stream for the waste gasification step.

[0066] Figure 5. Simplified block diagram process scheme describing a method for producing methanol from syngas originated from waste gasification. The process avoids the utilization of a WGS and of a CO2 removal unit by including a steam electrolyzer system that produces the H2 useful for the achievement of an appropriate (H2-CO2) / (CO+CO2) ratio in the synthesis gas and consequently avoids one major CO2 emission point. The steam / water electrolysis unit also provide an O2 stream for the waste gasification step. Moreover, the process solution includes an SCT-CPO reactor able to process the purge of recycle gas for producing additional synthesis gas thus avoiding the second major GHG emission point. Noteworthy the SCT-CPO reactor can also receive NG or other CO2 rich hydrocarbon (HC) feedstock and in case steam, for boosting the syngas production with appropriate (H2-CO2) / (CO+CO2) ratios.

[0067] Figure 6. Simplified block diagram process scheme describing a method for producing methanol from syngas originated from wastes gasification. The process avoids the utilization of a WGS and of a CO2 removal unit by including a steam electrolyzer system that produces the H2 useful for the achievement of an appropriate H2 / CO ratio in the synthesis gas and consequently avoids one major CO2 emission point. The steam / water electrolysis unit also provide an O2 stream for the waste gasification step. Moreover, the process solution includes an SCT-CPO reactor able to process the purge of the F-T recycle gases for producing additional synthesis gas thus avoiding the second major GHG emission point. Noteworthy the SCT-CPO reactor can also receive NG or other CO2 rich hydrocarbon (HC) feedstock and in case steam, for boosting the syngas production with appropriate H2 / CO ratios.

[0068] Figure 7. (A) Qualitative drawing of the enthalpy / temperature contributions determined by reactions [1], [2], [3-4], [5] and [6] occurring along a tubular reactor including a fixed catalytic bed operated at low mass flow velocity; the solid line represents the total enthalpy variation

[0069] (B) Qualitative drawing of the enthalpy / temperature contributions determined by reactions [1], [2], [3-4], [5] and [6] occurring along a truncated cone geometry including a fixed catalytic bed operated at high mass flow velocity; the solid line represents the total enthalpy variation

[0070] Figure 8. Scheme of the internal zones of a SCT-CPO reactor with a truncated cone reaction zone with elements on the geometry of the truncated cone zone

[0071] Figures 1 and 2 show that the process schemes deriving from the known literature information when utilizing synthesis gas produced by urban, industrial, and agricultural wastes cannot avoid two main CO2 and GHG emission points either in the production of methanol and in the production of liquid fuels and chemicals.

[0072] With reference to Fig. 1, in case of the methanol synthesis, the first CO2 emission point is determined by the necessity of removing some CO2 molecules from the partially shifted synthesis gas produced by the waste gasification and cleaning steps, to adjust the ratio (H2- CO2) / (CO+CO2) to values around 2 v / v.

[0073] With reference to Fig. 2, in case of the F-T synthesis the WGS step is not mandatory but also in this case a CO2 removal section is necessary to achieve the desired H2 / CO v / v ratio (ca. 2 v / v).

[0074] The second GHG emission point is determined by the necessity of purging either the methanol synthesis recycle loop and the F-T synthesis recycle loop. These purges are necessary for avoiding the accumulation of molecules that are not active in these two chemical processes namely CH4 and other gaseous hydrocarbon molecules and an excess of CO2. Noteworthy, the purge operations are not selective towards these molecules and the purge streams also contain relevant amounts of H2 and CO.

[0075] We have now found that by introducing inside the process scheme steam electrolysis and SCT-CPO these two CO2 and GHG emission points are avoided or strongly reduced.

[0076] The same result could not be achieved with non-catalytic partial oxidation since the high H2 and CO content and the low gaseous hydrocarbon content in these streams would determine total oxidation reactions increasing the amount of CO2 and H2O rather than partial oxidation products; namely CO and H2.

[0077] For what concerns the methanol synthesis schemes, the Figures 3 and 5 show how the steam electrolysis providing a stream of pure H2 and a stream of pure O2 avoids either: i) the necessity of introducing a WGS step for adjusting the (H2-CO2) / (CO+CO2) ratios and ii) the necessity of a CO2 removal section. The addition of the hydrogen produced by electrolysis to the main synthesis gas stream produced by gasification of waste allow to modify its composition to achieve a ratio (H2-CO2 / (CO+CO2) from 1.5 to 2.5 v / v, preferably from 1.7 to 2.3 v / v, more preferably from 1.8 to 2.2 v / v, thereby avoiding any CO2 separation from the main syngas stream.

[0078] Figure 5 also shows that the utilization of SCT-CPO allows the conversion of the purge gas into additional synthesis gas also utilizing the O2 stream produced by the steam electrolysis.

[0079] Again, as already mentioned, the same result could not be achieved with non-catalytic partial oxidation since the high H2 and CO content and the low gaseous hydrocarbon content in these streams would determine total oxidation reactions increasing the amount of CO2 and H2O rather than partial oxidation products; namely CO and H2.

[0080] Noteworthy, the production of synthesis gas with SCT-CPO can also utilize other gaseous hydrocarbon streams and in particular CO2 rich hydrocarbon stream. The flexibility towards the feedstock composition and the operation conditions of this technology allows to produce a synthesis gas stream with an appropriate composition for contributing to the final syngas flow to be utilized in the methanol synthesis reactor. In particular, the SCT-CPO reactor allows using the purge of recycle gas for producing additional synthesis gas, thus avoiding a major GHG emission point. Noteworthy the SCT-CPO reactor can also receive NG or other CO2 rich hydrocarbon (HC) feedstock and in case steam, for boosting the syngas production with appropriate (H2-CO2) / (CO+CO2) ratios.

[0081] Analogously, for what it concerns the F-T synthesis schemes the Figures 4 and 6 show how the steam electrolysis providing a stream of pure H2 and a stream of pure O2 avoids the necessity of a CO2 removal section for obtaining a synthesis gas with an appropriated H2 / CO ratio.

[0082] Figure 6 also shows that the utilization of SCT-CPO allows the conversion of the purge gas into additional synthesis gas also utilizing the O2 stream produced by the steam electrolysis. Noteworthy, also in this case, the production of synthesis gas with SCT-CPO can also utilize other gaseous hydrocarbon streams and in particular CO2 rich hydrocarbon stream. The flexibility towards the feedstock composition and the operation conditions of this technology allow to produce a synthesis gas stream with an appropriate composition for contributing to the final syngas flow to be utilized in the F-T synthesis reactor.

[0083] Figures 2, 4 and 6 also show that the proposed process scheme solution consider either the possibility of: a) operating in parallel low temperature and high temperature F-T processes for obtaining a plurality of hydrocarbon products, b) operating only low temperature F-T processes or high temperature F-T processes.

[0084] For what it concerns the SCT-CPO technology and for explaining the unique reactivity features that allows the integration of this technology with the innovative process schemes that are here described we report the following information.

[0085] The thermo-chemical properties of the reaction environment produced in short contact time conditions during the SCT-CPO in a heterogeneous catalytic fixed bed reactor fed with a premixed CH4, Steam, CO2 and O2 stream, can be discussed considering the system composed by the by equations [1-5]

[0086] CH4+ 2O2= CO2+ 2H2O AH° = -803.0 kJ / mol [1]

[0087] CH4+ * / 2 O2= CO + 2 H2AH0= -38 kJ / mol [2]

[0088] CO + H2O CO2 + H2AH° = -41.0 kJ / mol [3]

[0089] CO2+ H2CO + H2O AH° = 41.0 kJ / mol [4]

[0090] CH4+ CO2= 2CO + 2 H2AH° = 247.3 kJ / mol [5]

[0091] CH4+ H2O = 3H2+ CO AH° = +206 kJ / mole [6]

[0092] The exothermic total oxidation reaction [1] has the highest probability to occur at the beginning of the bed, while the endothermic steam-CO2 reforming reactions [5] and [6] and the mildly endothermic (RWGS) reaction [4] would have the highest probability to occur in following zone.

[0093] Noteworthy, by increasing the reaction temperature above 830 °C reaction [4] is favored with respect to reaction [3] and also favored with respect to steam-CCh reforming [5] and [6].

[0094] However, we found that the extent and the localization of these reactions inside the catalytic bed are greatly affected by physical and chemical factors. Total combustion [1] has been found be the most competitive reaction on noble metal base (Rh, Ru, Ir, Pt, Pd) catalysts at "relatively low temperatures" below 750 °C and at high O2 partial pressure.

[0095] These are typically the conditions produced at the beginning of the catalytic beds in tubular reactors operated at “high” contact time values (e.g., above 1 s). In these cases, we found that the thermal profiles of the reaction environments are determined by the strongly exothermic reaction [1] with a minor contribution of reactions [2], [3] and [4], followed by the strongly endothermic steam-CCh reforming reactions [5] and [6].

[0096] These conditions originate very large axial temperature gradients and moreover, the energy release associated to total combustion also determines the propagation of the heterogeneous reactions into the gaseous phase originating a rather unselective radical chemistry leading to unsaturated molecules and soot formation.

[0097] Indeed, it has been found that with tubular reactors the catalytic partial oxidation reactions cannot be performed at high pressures since reaction [1] cannot be controlled and propagate reactions into the gaseous phase with the risk of flame ignition particularly at high pressure (e.g above 10 ATM) but in any case, producing some radical reactions leading to the formation of unsaturated hydrocarbons precursors of solid carbonaceous compounds.

[0098] Instead, it has been found that it is possible that the solid catalyst temperatures reach values higher than 1000 °C while the gas remains relatively cool by utilizing a reaction environment geometry that allows to reduce the contact time at the entrance of the catalytic bed to few milliseconds and that allows the expansion of the reaction volume when the temperature and the mole flow increases due to the progressing of the reaction. This effect is obtained by adopting a truncated shape geometry of the catalytic bed and catalyst geometrical features that allow to reduce the pressure drop inside the reaction zone.

[0099] Accordingly, it has been found that in these short contact time conditions, the methane conversion largely depends on the O2 / C ratios while is almost unaffected by the addition of steam and CO2. This addition instead modifies the H2 / CO ratios in the produced synthesis gas clearly indicating that the reactivity is largely determined by the direct partial oxidation [2] and by the RWGS reaction [4] .Figure 7 shows qualitative pictures of the Enthalpy / Temperature profiles obtained at (A) low mass velocity, high contact time, tubular geometry of the catalytic bed and (B) high mass velocity, short contact time, truncated cone geometry of the catalytic bed.

[0100] Figure 8 shows the main zones of the SCT-CPO reactor including a truncated cone reaction zone; these include:

[0101] The cylindrical first portion includes a mixing inlet zone and a first thermal shield pre-heating zone.

[0102] The central second portion includes a reaction zone,

[0103] The cylindrical third portion includes a second thermal shield and a reactor exit zone.

[0104] The angle a shown in Figure 8 is clearly lower than 85° and preferentially comprised between 75° and 30°.

[0105] The other geometrical features namely the: i) truncated cone inlet radius Rl, ii) the truncated cone exit radius R2, iii) the truncated cone length L and the catalytic bed filling are designed for allowing pressure drop values (AP) inside the catalytic bed between 0.1 and 10 ATM and preferentially between 0.5 and 5 ATM.

[0106] To this purpose the ratios R1 / R2 have to be comprised between 0.9 and 0.1 and preferentially between 0.8 and 0.4 and the shapes of the filling of the catalyst bed need to be defined for minimizing the pressure drop conditions by utilizing pelletized or monolith structures and their combinations.

[0107] It has also been noted the existence of a non-thermal equilibrium between the gas and the solid phases. This has been explained considering that the chemical heat generated at the surfaces and emitted by radiation, is absorbed, and scattered much better by the solid than by the gaseous phase and is transferred along the catalytic bed from the hotter towards the cooler points smoothing the solid surface temperatures.

[0108] The main experimental observations on the thermo-chemical properties of the SCT environments, performed after optimization of the reaction environment characteristics, are synthesized as follows: i) the temperature of the solid phase raises steeply at the beginning of the bed and the temperature profiles are smoothed through radiative and conduction mechanisms in the axial and radial directions; ii) temperature differences are originated between the gas and the solid phases; iii) local surface temperatures values result higher than the adiabatic temperatures; iv) gas temperatures are always lower than the adiabatic temperatures and gradually increase from the entrance to the exit of the bed.

[0109] It has also been found that part of the reaction heat is transferred towards the incoming reactants inside the first thermal shield zone and in this way a reactant pre-heating internal to the reactor is also achieved.

[0110] Accordingly, in the described process solutions, the CO2 emissions are mainly related to the E.E. consumption required for: - compressing the feedstock (compression energy that would be required for any syngas production technology),

[0111] - obtaining the O2 flow with an Air Separation Unit (ASU),

[0112] - obtaining H2 and O2 flows from steam / water electrolysis.

[0113] More in detail, it has been found that the described SCT-CPO reactor has unique features that allow: i) the utilization of CO2 rich feedstock and ii) the utilization of the F-T tail gases and of the other offgases produced in the separation and / or upgrading of the primary F-T products as well as iii) of the tail gas of the methanol synthesis loop. These streams can be utilized for producing additional synthesis gas useful to the F-T synthesis as well as to the MeOH synthesis allowing the incorporation of CO2 molecules in the reaction products and the avoidance of GHG emissions associated to the purge-gas, tail-gas and the other off-gas streams associated the operation of the F-T and / or MeOH synthesis processes. Noteworthy, these possibilities are not allowed by the existing synthesis gas production technologies due to: i) carbon formation reactions [7-10] and ii) to the possibility allowed only by SCT-CPO to avoid heating furnaces for pre-heating the reaction mixture and consequently avoiding CO2 emissions in the heating furnaces.

[0114] The occurrence of carbon formation reactions determines limitations in the operation conditions; these limitations particularly affect the possibility of lowering or avoiding the steam content in the reactant mixtures. More in detail, the carbon formation reactions are particularly relevant at pressures between 15 - 40 ATM.

[0115] 2 CO = CO2+ C AH0= - 171 kJ / mol [7]

[0116] CO + H2= H2O + C AH0= 131 kJ / mol [8]

[0117] CH4= 2 H2+ C AH0= 75 kJ / mol [9]

[0118] CnHm (g) = olefins (g) = coke (s)

[0010]

[0119] Indeed, particularly reactions [7] and [9-10] are the primary sources of carbon that can be divided into three typologies: i) whisker carbon, ii) gum (encapsulating carbon), and iii) pyrolytic carbon. Gum formation and pyrolytic carbon are especially associated with the presence of hydrocarbons with more than two carbon atoms in the feedstock and can be avoided by removing these molecules with a pre-reformer unit upstream dry reforming.

[0120] Instead, the production of whisker carbon can only be avoided by operating in condition having a low thermodynamic affinity towards this species which, once formed, brings to the catalyst pellet destruction and to the plant shut down due to the necessity of avoiding that the heat flow from the furnace not adsorbed by the endothermic reactions could lead to tubes overheating and fracturing.

[0121] The SCT-CPO reactor and process solutions here described overcome the drawbacks related to the occurrence of carbon formation reactions and allow, as already mentioned, the inclusion of the CO2 molecules and of the saturated and unsaturated hydrocarbon molecules of the tail gases, purge gases and off-gases produced in the F-T and MeOH synthesis.

[0122] Noteworthy, it is further underlined that only the reactor structure according to the invention is effective for producing these reactivity features while other CPO reactors utilizing tubular and fixed bed reactors, fluidized bed, moving beds, or bubbling bed reactors cannot be applied in the conditions here described.

Claims

CLAIMS1. Process for the production of methanol and / or hydrocarbons from waste materials comprising the steps of: a) oxidative gasification of said waste materials with production of a main synthesis gas stream; b) cleaning of said main synthesis gas stream produced in said step a); c) production of hydrogen and oxygen streams by electrolysis of steam or water; d) addition of the hydrogen produced in said step c) to said main synthesis gas stream produced in said step a) to modify its composition to achieve: i) a ratio (H2-CO2 / (CO+CO2) from 1.5 to 2.5 v / v, preferably from 1.7 to 2.3 v / v, more preferably from 1.8 to 2.2 v / v, useful for the methanol synthesis, thereby avoiding any CO2 separation from the main syngas stream; or ii) a ratio H2 / CO from 1.5 to 2.5 v / v, preferably from 1.7 to 2.3 v / v, more preferably from 1.8 to 2.2 v / v, for use in the production of hydrocarbons by means of the Fischer-Tropsch synthesis thereby avoiding any CO2 separation from the main syngas stream; e) use of said synthesis gas stream with the modified composition of said step d)i) to produce methanol by the methanol synthesis or use of said synthesis gas with the modified composition of said step d)ii) to produce hydrocarbons by the Fischer- Tropsch synthesis; f) use of gases purged from said oxidative gasification step a) and from one or more of said steps b), c) and d) as a feedstock of a SCT-CPO process to produce an additional stream of synthesis gas, which is then combined with said main synthesis gas stream and fed to said step e) for the synthesis of methanol and / or hydrocarbons, wherein said feedstock further comprises one or more of recycle gases, tail gases, purge gas of the F-T synthesis, recycle gases of the methanol synthesis and one or more of natural gas and / or a hydrocarbon feedstock having a CO2 content of at least 5% v / v.

2. Process according to claim 1, wherein in said step e) said synthesis gas with the modified composition of said step d)i) is used to produce methanol with the methanol synthesis.

3. Process according to claim 1, wherein in said step e) said synthesis gas with the modified composition of said step d)ii) is used for the synthesis of hydrocarbons with the Fischer - Tropsch process.

4. Process according to any claim 1 - 3, wherein said modification of the composition of said main synthesis gas stream of step d) i) is carried out on a first part of said main synthesis gas stream, and said modification of the composition of said main synthesis gas stream of said step d) ii) is carried out on a second part of said main synthesis gas stream, whereby said first part of said main synthesis gas stream is utilized in the methanol synthesis and said second part of said main synthesis gas stream is utilized in the Fischer-Tropsch synthesis.

5. Process according to any claim 1-4, wherein the produced methanol is utilized to produce fuels through the methanol to gasoline process or chemicals selected from the group consisting of acetic acid, dimethyl carbonate, dimethyl ether.

6. Process according to any claim 1-4, wherein the produced methanol is utilized to produce olefins through the methanol to olefins process.

7. Process according to any claim 1-4, wherein said SCT-CPO reactor is fed with a feedstock comprising an organic component and an inorganic component, wherein: i) said organic component is a mixture comprising carbon dioxide included in one or more of natural gas, associated gases, off-gases of industrial activities, biogas and carbon dioxide captured from gaseous streams, said carbon dioxide being from 5 to 50% v / v of said mixture; ii) said inorganic component comprises one or more of air, oxygen, and air enriched with oxygen, and optionally steam; iii) said oxygen is obtained from electrolysis of water or from air; and iv) said short contact time catalytic partial oxidation process is carried out in a reactor on a catalytic bed comprising a portion with truncated cone geometry operated at a gas hourly space velocity from 15,000 to 500,000 h1; v) said syngas has a hydrogen / carbon monoxide ratio from 0.5 to 3;8. Process according to claim 7, wherein said syngas has a hydrogen / CO ratio from 0.7 to 2.5, preferably from 1 to 2.1.

9. Process according to any claim 1-8, comprising an electrolyzer that produces oxygen which is fed to said oxidative gasification step a) of said waste materials, and hydrogen which is mixed to main synthesis gas stream to modify its composition to achieve a ratio (H2-CO2 / (CO+CO2) according to said step d).

10. Apparatus for producing fuels and chemicals from waste materials with the process according to any claim 1-9, comprising a short contact time catalytic partial oxidation reactor containing a catalytic bed comprising a first portion having a cylindrical shape, asecond portion having the shape of a truncated inverted cone and a third portion having a cylindrical shape with a diameter greater than the diameter of said first cylindrical portion, wherein: a) in said second portion having the shape of a truncated inverted cone the upper base is smaller than the bottom base; b) said upper base of said truncated inverted cone is joined to said first cylindrical portion and said bottom base is joined to said third cylindrical portion; and c) the external angle (a) of said truncated cone at the upper base is lower than 80°.

11. Apparatus according to claim 10, wherein said upper base of said catalytic bed having the shape of a truncated inverted cone has a diameter R1 and said bottom base has a diameter R2, wherein the ratio R1 / R2 is from 0.9 to 0.1, preferably from 0.8 to 0.4.

Images