Claims:1. An aqueous-phase reforming (APR) process for the production of hydrogen from fast pyrolysis oil, said process comprising:
a. extracting fast pyrolysis oil with excess of water and separating it into aqueous and non-aqueous portions;
b. mild hydrogenation of the diluted aqueous portion of fast pyrolysis oil obtained in the preceding step in a slurry reactor at 125 °C and 7 bar for 1-2 hours over noble metal catalyst (Ru/C); and
c. aqueous-phase reforming of the hydrogenated fraction in the presence of a catalyst selected from the group comprising Pt-NiMgHTlc, Pt-NiCuHTlc and Pt-Ru/MWCNT in a continuous fixed-bed reactor.
2. The process as claimed in claim 1, wherein the catalyst Ru/C is synthesized by using incipient wetness impregnation technique, said technique comprising:
a. dissolving chloride salt precursor of Ruthenium in water, to have a Ru loading of 5 wt. %,
b. contacting precursor solution of step (a) with an activated carbon under stirring, followed by drying of the suspension to obtain the Ru/C catalyst, and
c. reducing the Ru/C catalyst in flowing hydrogen.
3. The process as claimed in claim 1, wherein the separation into aqueous and non-aqueous portions is carried out by centrifugation at 10,000 rpm for 30 minutes.
4. The process as claimed in claim 1, wherein the hydrogenated fraction in the fixed-bed reactor (step c) is at a temperature of 210-225 °C, and at a pressure of 22.4 – 29.3 bar.
5. The process as claimed in claim 1, wherein the APR catalyst is having a selectivity of 20 – 70 % for production of hydrogen from fast pyrolysis oil.
6. The process as claimed in claim 1, wherein the catalyst is selected from a group consisting of powdered form having 30-60 mesh size or 0.3-0.6 mm, and pelleted form.
7. The process as claimed in claim 1, wherein the APR catalyst is Pt-NiMgHTlc.
8. The process as claimed in claim 1, wherein the APR catalyst is Pt-NiCuHTlc.
9. The process as claimed in claim 1, wherein the APR catalyst is Pt-Ru/MWCNT.
10. A catalyst for production of hydrogen in an aqueous-phase reforming process, said catalyst comprising multi-walled carbon nanotubes (MWCNT) impregnated with Pt (Platinum) and Ru (Ruthenium), and wherein the concentration of Ru and Pt is 5 and 1 wt. %, respectively. , Description:FIELD OF THE INVENTION:

The present invention relates to the field of production of hydrogen and more particularly to a process for production of hydrogen from biomass feed i.e., fast pyrolysis oil and to the development of suitable catalysts for such processes.

BACKGROUND OF THE INVENTION:
Hydrogen (H2) is a promising energy carrier for use in fuels cells to generate clean electricity for stationary and mobile applications. Most H2 is currently produced from fossils, e.g., by steam reforming of natural gas (or naphtha) and gasification of coal. However, these processes result in the depletion of fossil fuels and the release of Greenhouse gases such as carbon dioxide (CO2) in the environment. Hence, it is desired to produce H2 from renewable resources such as biomass. In this way, CO2 released during biomass conversions is utilized for biomass growth and a closed carbon cycle is followed. So far, the carbon-neutral production of H2 from biomass energy resources is widely studied. By this way, the polluting and fast-diminishing fossil energy sources can be avoided. However, today’s biomass reforming technologies such as gasification and pyrolysis are complex and make many unwanted products such as coke and tar. Thus, the effective conversion of biofeeds into H2 constitutes an important challenge. It is easier to produce H2 from oxygenates producible from biomass, such as bio-alcohols or bio-oil, because they can be reformed with steam at temperatures lower than those used for reforming of hydrocarbons. Bio-oil – an intermediate renewable energy carrier – is especially promising. However, the energy required to vaporize the feed, the low selectivity to H2 and the difficult processes for purifying H2 are the major challenges of vapor-phase steam reforming of bio-oxygenates.
A low-temperature catalytic process that reforms intermediates from biomass (such as sugars and polyols) in the liquid phase is attractive (Cortright et al., 2002). It is called catalytic aqueous-phase reforming (APR). Here, water is kept in the liquid phase by using high pressure, slightly above the saturation pressure of water vapor at the reforming temperature. APR produces higher quality H2 (with less CO) and CO2 from weak solutions of bio-carbohydrates over a catalyst (e.g., Pt) in a single reactor near 225 °C by promoting water gas shift (WGS) and avoiding unwanted reactions. CO2 formed during this process is consumed for biomass growth, so the process is CO2-neutral. H2 thus produced can be used for fuel cell applications.
APR is selective to H2 and CO2 than gasification of solid biomass. APR has many advantages over steam reforming: APR is safe; needs lower temperatures; provides additional H2 through WGS; produces very less CO; saves energy by avoiding vaporization of feed; reduces cost by avoiding an extra WGS reactor; and lowers catalyst deactivation. Thus, it is advantageous to apply the APR process for reforming biofeeds to H2. In fact, APR is useful for utilizing diluted biomass waste streams from agricultural and industrial supplies.
The production of hydrogen by APR using a supported metal catalyst is limited by low selectivity. The production of a mixture of CO2 and H2 is thermodynamically unfavorable in comparison with the production of methane and higher-molecular-weight alkanes. Clearly, it is necessary to develop APR catalysts suitable for selective H2 generation.
Most APR studies use Pt catalysts with metal oxide supports (e.g., Al2O3, TiO2 and MgO). The Pt/Al2O3 catalyst is renowned for its performance in APR of different oxygenates and is often regarded as a benchmark for the APR process. However, the alumina support is linked to problems of catalyst stability. For instance, hydration of high surface area ?-Al2O3 by hot compressed water leads to the collapse of meso-pores and a phase transition to boehmite Al (OOH) whose surface area is lower. Metal particles deposited inside these pores are encapsulated during collapse, and the catalytic sites are rendered unavailable. Fortunately, phase transition is rapid and just the initial activity drops. Pt/Boehmite is stable for APR in the absence of acidic oxygenates. However, when oxygenates such as carboxylic acids (e.g., acetic acid) are present in feed (e.g., bio-oil) or formed as by-products during reaction (e.g., APR of ethylene glycol), further hydroxylation of the alumina surface occurs, and migration leads to the coverage of the Pt metal particles. Thus, the metal particles become unreachable, and the activity is lost. Thus, it is essential to use durable supports for the APR process. Pt and Ni are most widely reported metals for the catalytic APR process. Pt promotes C-C cleavage and is most selective to H2, but it is expensive. Ni provides a cheaper alternative to Pt but it promotes methane formation, gives into coking, and undergoes leaching in acidic APR conditions.
Carbonaceous supports, which have high hydrothermal stability and surface area, are often used for reactions in hot compressed water. Examples of supports for Pt-based APR catalysts include activated carbon (AC), carbon fibres, carbon nanotubes (CNT) and ordered mesoporous carbon. AC has high micro-porosity, and hence, is liable to diffusion limitations for larger biomass surrogate molecules and pore blockage by coke formed during reaction.
US9095844B2 discloses a catalyst for aqueous-phase reforming of biomass-derived polyols, which comprises platinum and copper as active metals and a mixture of magnesia and alumina as support. Further, a method of producing hydrogen by carrying out aqueous-phase reforming of a feedstock comprising biomass-derived polyols in the presence of a bimetallic catalyst which comprises active metals consisting of platinum and copper and a mixture of magnesia and alumina as a support, wherein the contents of platinum and copper in the catalyst are 0.1-2.0 wt. % and 0.05-1.0 wt. %, respectively, based on total weight of the catalyst, and the mixture of magnesia and alumina has a Mg/Al ratio of 0.5-5.0 and is prepared by calcination of layered double hydroxide.
WO2009/129622 discloses APR of biomass-derived oxygenated compounds in stirred tank reactor using platinum and nickel catalysts supported on alumina, silica, activated carbon and zeolite. Further it discloses a process of producing hydrogen in which water is reacted with an oxygenated hydrocarbon in the condensed phase under pressure and low temperature in the presence of a metal catalyst supported on a carrier material dispersed in said condensed phase, characterized in that the reaction is carried out in a stirred tank reactor in the absence of an electrolyte.
US8231857B2 discloses catalysts and methods for reforming oxygenated compounds, including biomass-derived compounds, to form products such as hydrogen or alkanes via reforming processes, such as aqueous-phase reforming. Aqueous solutions containing at least 20 wt. % of the oxygenated compounds can be reformed over a catalyst comprising a Group VIII transition metal and a Group VIIB transition metal, preferably supported on an activated carbon-supported catalyst. In other embodiments, catalysts are provided for production of hydrogen or alkanes at reaction temperatures less than 300° C.
Dewoolkar et al, ChemCatChem, 2016, discloses a method for the sustainable production of hydrogen. More particularly relates to composites of Ni and cationic-modified hydrotalcite (HTlc) promoted with Pt, resulting in two novel hybrid materials Pt-NiMgHTlc, and Pt-NiCuHTlc. Promotion with Pt improves H2 purity and multi-cycle durability.
Cortright et al, Nature, 2002, relates to the production of hydrogen from sugars and alcohols at temperatures near 500 K in a single-reactor aqueous-phase reforming process using a platinum-based catalyst from catalytic reforming of biomass-derived hydrocarbons in liquid water. Further it discloses conversion of glucose and catalytic aqueous-phase reforming for the generation of hydrogen-rich fuel gas from carbohydrates extracted from renewable biomass and biomass waste streams.
Vispute et al, Green Chem., 2009, discloses the production of hydrogen, alkanes, and polyols by aqueous-phase processing of wood-derived pyrolysis oils. Further, hydrogen is produced at a hydrogen selectivity of 60% from the water-soluble part of bio-oil. Alkanes are produced from the water-soluble bio-oil by aqueous-phase dehydration/hydrogenation with a bifunctional catalyst. Alkane selectivity is 77%, when hydrogen is co-fed with the bio-oil.
Further, there is a need for an improved catalytic APR process for the selective production of hydrogen from bio-carbohydrates and fast pyrolysis oil (or bio-oil). Besides, it is also necessary to develop active and stable catalysts for the APR process.
Objectives of the present invention:

It is a primary objective of the present invention to provide an aqueous-phase reforming (APR) process for the production of hydrogen from fast-pyrolysis oil.

It is a further objective of the present invention to provide a catalyst of high selectivity, durability, and activity for APR process for the production of hydrogen.

It is a further objective of the present invention to provide a process for the production of hydrogen using catalyst systems selected from Pt-NiMgHTlc, Pt-NiCuHTlc, and Pt-Ru/MWCNT.

Summary of the invention:

The present invention discloses an aqueous-phase reforming (APR) process for the production of hydrogen from fast-pyrolysis oil.

The present disclosure provides an aqueous-phase reforming (APR) process for the production of hydrogen from biomass feed, said process being characterized in using an APR catalyst selected from the group comprising Pt-NiMgHTlc, Pt-NiCuHTlc and Pt-Ru/MWCNT.

One of the aspects of the present invention provides an aqueous-phase reforming (APR) process for the production of hydrogen from fast-pyrolysis oil, the process comprising,
a. extracting fast-pyrolysis oil with excess of water to obtain aqueous and non-aqueous portions;
b. mild hydrogenation of diluted aqueous portion in a slurry reactor at 125 °C and 7 bar for 1-2 hours over noble metal catalyst (Ru/C); and
c. hydrogenated fraction is subjected to aqueous-phase reforming (over Pt-NiMgHTlc, Pt-NiCuHTlc and Pt-Ru/MWCNT catalyst) in a continuous fixed-bed reactor to produce hydrogen.
In another aspect of the present invention, the noble metal catalyst (Ru/C) is synthesised by incipient wetness impregnation technique. In this technique, chloride salt precursors of ruthenium are dissolved in water and contacted with activated carbon under stirring. The resulting suspension is dried, and the catalyst is reduced in flowing hydrogen. The loading of Ru is 5 wt. %.
In one of the aspects of the present invention, the catalyst for aqueous-phase reforming (APR) process is selected from Pt-NiMgHTlc, Pt-NiCuHTlc, and Pt-Ru/MWCNT.
In one of the aspects of the present invention, the catalyst for aqueous-phase reforming (APR) process is having a selectivity of 20 – 70 % for the production of hydrogen from biomass feed.
In one of the preferred aspects, the present invention provides a catalyst for the production of hydrogen in an aqueous-phase reforming process, the said catalyst comprising multi-walled carbon nanotubes (MWCNT) impregnated with Pt (Platinum) and Ru (Ruthenium).
In one of the aspects of the present invention, the catalyst for the production of hydrogen in an aqueous-phase reforming process is multi-walled carbon nanotubes (MWCNT) impregnated with 1 wt. % Pt (Platinum) and 5 wt. % Ru (Ruthenium).
In still another aspect of the present invention, the catalyst for the production of hydrogen in an aqueous-phase reforming process is in powdered form (30-60 mesh size or 0.3-0.6 mm), or pelleted form.

The present disclosure provides a selective conversion of fast pyrolysis oil into hydrogen via an improved APR process. Further, the disclosure also provides superior APR catalysts which are active, selective, and stable. In the present process, hydrogen is renewably produced from biomass in a closed carbon cycle. Bio-oil is obtained from fast pyrolysis of lingo-cellulosic biomass residues; thus, this is an effective route for the utilization of waste biomass. The process further provides the opportunity to partly utilize hydrogen product for hydrotreating the non-aqueous portion of fast pyrolysis oil (or pyrolytic lignin) into liquid transportation fuels.

Brief description of the drawings:

Figure 1: illustrates scheme for hydrogen production of the present invention.

Detailed Description of the invention:

For promoting an understanding of the principles of the present disclosure, reference will now be made to the specific embodiments of the present invention further illustrated in the drawings and specific language will be used to describe the same. The foregoing general description and the following detailed description are explanatory of the present disclosure and are not intended to be restrictive thereof. It will nevertheless be understood that no limitation of the scope of the present disclosure is thereby intended, such alterations and further modifications in the illustrated method, and such further applications of the principles of the present disclosure as illustrated herein being contemplated as would normally occur to one skilled in the art to which the present disclosure relates. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinarily skilled in the art to which this present disclosure belongs. The methods, and examples provided herein are illustrative only and not intended to be limiting.

In one of the aspects the present disclosure describes an aqueous-phase reforming (APR) process for the production of hydrogen from fast-pyrolysis oil.

In another aspect the present disclosure describes an efficient catalyst system for APR of fast-pyrolysis oil.

In another aspect the present disclosure describes an efficient catalyst system for aqueous-phase reforming (APR) of fast-pyrolysis oil, i.e., Pt-NiMgHTlc, Pt-NiCuHTlc and Pt-Ru/MWCNT.

In another aspect the present disclosure describes a method for preparation of catalysts, Pt-NiMgAl and Pt-NiCuAl
Hydrotalcite: [M 2+(1-X) M 3+X (OH)2] X+ (A n-) X/n. m H2O
where M 2+ = Mg 2+, Ca 2+, Cu 2+, Zn 2+, Mn 2+, Fe 2+ etc.
M 3+ = Al 3+, Fe 3+, Ga 3+ etc.
A n- = [CO3] 2- , Cl - etc.

In another aspect, the disclosure describes hybrid materials NiMgAl and NiCuAl prepared by co-precipitation of metal nitrates.

In another aspect, it is described that the Mg/Al and Cu/Al ratio is equal to 3.

In another aspect, it is described that the nickel loading is 10 wt. %.

In another aspect, it is described that the hybrid materials were promoted with impregnation of 2.5 wt. % Pt.

In another aspect, it is described that the hydrotalcite used for making catalysts for the aqueous-phase reforming process is: [M 2+(1-X) M 3+X (OH)2] X+ (A n-) X/n. m H2O,
where M 2+ = Mg 2+ or Cu 2+, M 3+ = Al 3+, and A n- = [CO3] 2-

In another aspect, it is described that Ni-based hydrotalcites are promoted with Pt (here, denoted by Pt-NiMgHTlc and Pt-NiCuHTlc). These hydrotalcites are layered double hydroxides that are precursors for reforming catalysts and are also good sorbents for the CO2 sorption-enhanced steam reforming process. Copper is a good dehydrogenation catalyst and improves the performance of Ni. Also, promotion with small amount of Pt is beneficial.

In another aspect, it is described that Pt-Ru/MWCNT catalysts are used for APR of fast-pyrolysis oil. Carbon nanotubes (CNT) are used as support, due to their resistance to acidic conditions, open structure, and absence of meso- and micro-pores. They suppress catalyst deactivation via coke blockage and overcome diffusion limitations. Pt/CNT and Ru/CNT are stable and active during reforming of acetic acid in supercritical water.

In another aspect, it describes preparation of Pt-Ru/MWCNT catalyst using the following steps: pre-treating the carbon nanotubes (CNT) with a solution containing nitric acid, recovering the pre-treated CNT from solution using vacuum filtration, contacting CNT with solution containing pre-cursors of Pt and Ru in water with stirring, followed by heating, ultra-sonication for effective impregnation of Pt and Ru on CNT; and drying of the resulting suspension of catalyst. The loadings of Ru and Pt were 5 and 1 wt. %, respectively.

These aqueous-phase reforming catalysts are used in powdered form (30-60 mesh size or 0.3-0.6 mm) and pelleted form.

A fixed-bed reactor is used for the aqueous-phase reforming process and the diluted feed is at the temperature of 210-225 °C and at a pressure 22.4 – 29.3 bar.

It is described that the process for production of hydrogen comprises the following steps:
a. extraction of fast pyrolysis oil with excess of water and separating it into aqueous and non-aqueous portions;
b. mild hydrogenation of diluted aqueous portion of fast pyrolysis oil in a slurry reactor operating in batch mode at 125 °C and 7 bar for 1-2 hours over noble metal catalyst (Ru/C) synthesized by using incipient wetness impregnation technique (Ru=5 wt. %) by dissolution of the chloride salt pre-cursor of Ruthenium in water; and rapidly contacting with activated carbon under stirring; and drying of the resulting suspension; and reduction of the catalyst in flowing hydrogen; and
c. aqueous-phase reforming of the hydrogenated fraction in the presence of a catalyst selected from the group comprising Pt-NiMgHTlc, Pt-NiCuHTlc and Pt-Ru/MWCNT catalyst in a continuous fixed-bed reactor.
Example 1
As depicted in figure 1, the fast pyrolysis oil is mixed slowly with water for better solubilisation of the liquid. If the solubilisation is carried out the other way around, the water dissolves only the outer part of the pyrolysis liquid sample and the dissolution may be incomplete. Excess water is used for proper mixing and obtaining a homogenous mixture. The mixture is centrifuged at 10,000 rpm for 30 minutes to ensure phase separation into an aqueous-rich phase (WSBO: water soluble fraction of bio-oil/fast pyrolysis oil) and an organic-rich phase (WIBO: water insoluble fraction of bio-oil/fast pyrolysis oil). The two phases, aqueous (bottom) and non-aqueous (top), are separated by decanting. The weight of the aqueous fraction is measured to determine the fraction of fast pyrolysis oil that is dissolved in water. No externally added water goes into WIBO during the extraction process. Next, mild hydrogenation of WSBO is carried out in a high-pressure reactor i.e., slurry reactor operating in batch mode at 125 °C and 7 bar for 1-2 hours over noble metal catalyst (Ru/C). Further aqueous-phase reforming of the hydrogenated fraction over Pt-Ru/MWCNT catalyst is performed in a continuous fixed-bed reactor to obtain hydrogen. The hydrogenated fraction in the fixed-bed reactor is at a temperature of 210-225 °C, and at a pressure of 22.4 – 29.3 bar. Around 75% carbon in the hydrogenated WSBO feed is converted into gas phase over Pt-Ru/MWCNT at 210 oC temperature and 22.4 bar pressure.
Example 2
In another example, the aforesaid hydrogenated WSBO fraction is reformed in the liquid phase over Pt-NiMgHTlc in a continuous fixed-bed reactor at 210 oC temperature and 22.4 bar pressure, and the H2 selectivity is 70%.
Example 3
In another example, the aforesaid hydrogenated WSBO fraction is reformed in the liquid phase over Pt-NiCuHTlc in a continuous fixed-bed reactor at 210 oC temperature and 22.4 bar pressure, and the H2 selectivity is 45%.