Quantitative Study of Straw Bio-oil Hydrodeoxygenation over a Sulfided Ni Mo Catalyst

[NNadir]

The paper I'll discuss in this post is this one: Quantitative Study of Straw Bio-oil Hydrodeoxygenation over a Sulfided NiMo Catalyst (Miloš Auersvald*† , Bogdan Shumeiko†, Martin Staš† , David Kubička† , Josef Chudoba‡, and Pavel Šimáček†, ACS Sustainable Chem. Eng., 2019, 7 (7), pp 7080–7093)

Recently in this space I noted the preparation of a carbon dioxide capture agent, a porous form of magnesium carbonate impregnated with PEI (Polyethylimine) that involved the use (in preparation) of the dangerous fossil fuel derived solvent toluene.

I often argue that petroleum mining, which irrespective of how the "peak oil" hullabaloo turned out in the short run turned out, is unacceptable. As far as motor fuels - to the extent we really want them - are concerned, it is (to my mind) a no-brainer. Gasoline is neither a safe nor clean fuel, but clean fuels are available, notably the wonder fuel dimethyl ether, which can effectively displace all of the world's diesel, gasoline, LPG, and dangerous natural gas wherever they are subject to combustion in heat engines of various types.

The question of replacement of petroleum for chemical feed stocks is a little more problematic, although syn gas can easily displace most aliphatic molecules. The pathway for most of these is seems pretty clear to me from memory.

Aromatic compounds, benzene and its related compounds, at least those lacking oxygen substituents are a little bit more problematic for me. I know routes exist to make them from biomass, but they for some reason don't stick in my mind. It's why this paper caught my eye in my general reading.

From the introductory text:

Fast pyrolysis is one of the simplest and most cost-effective options for the conversion of a lignocellulosic biomass into a bio-oil, achieving yields of up to 75 wt %.(1) Despite its undesirable properties (thermal lability, high acidity, high water/oxygen content),(2) the bio-oil has the potential to be used for the production of advanced biofuels. For this purpose, it is necessary to reduce the oxygen content of the bio-oil and to improve its properties in general. Despite its high operating expenditures, hydrotreatment is one of the most promising methods for bio-oil upgrading, producing higher yields of upgraded products with an acceptable quality.(3) Thus, it is desirable to optimize the bio-oil hydrotreatment process. For this purpose, a quantitative characterization of the chemical composition of the bio-oil and its upgraded products is crucial.(4)

A bio-oil is a complex mixture of hundreds to thousands of oxygenates.(5) Together with the fact that its chemical composition is strongly dependent on the original biomass,(2) this makes a detailed quantitative characterization very difficult and time-consuming. Probably, for this reason, some papers studying bio-oil hydrodeoxygenation (HDO) only focused on the characterization of the physicochemical properties of the HDO products.(6?8) To simplify the determination of the bio-oil composition, some researchers used the percentage of the total peak area obtained from GC-MS to estimate the content of the individual chemical compounds.(4,9?11) However, such an approach can be misleading due to the different response factors of the different oxygenates.

To our best knowledge, just three papers focused on the detailed quantification of the chemical changes occurring during the bio-oil HDO.(12?14) Routary et al.(12) used GC-FID and HPLC-RI to quantify oxygenates and a special GC-MS technique (nitric oxide ionization spectroscopy evaluation) to quantify the hydrocarbons formed. Sanna et al.(14) used GC-MS for the quantification of 28 different compounds and HPLC for the quantification of saccharides. Nevertheless, the most detailed study up to now was apparently carried out by Stankovikj et al.(13) from the National Renewable Energy Laboratory (NREL)...

...In our previous paper, we tested a sulfided NiMo/Al2O3 catalyst for the HDO of a straw bio-oil (as an alternative to the wood bio-oil generally used) from the ablative fast pyrolysis and analyzed the physicochemical properties of the resulting HDO products.(25) To provide a deeper understanding of the whole straw bio-oil HDO process over the sulfided catalysts, we have built upon our previous work and present what, to our best knowledge, is the first such detailed quantitative study of this process including analysis of both the aqueous and organic phases formed. Low-molecular compounds were quantified by GC-MS, 115 of them were quantified directly and the other more than 100 indirectly. The total concentrations of the carboxylic acids, carbonyls and phenols were quantified by the carboxylic acid number (CAN), Faix, and Folin–Ciocalteu methods, respectively. Thanks to the detailed analysis of the volatile compounds, we were able to consider the reactivity of the respective groups in the nonvolatile fractions of the samples...

The authors utilize GC/MS (gas chromatography with mass spec detection) to understand the catalytic approach they are performing.

Bio oils (and lignins, the non-cellulose portion of wood and straw) typically contain large amounts of phenols and polyphenolic compounds, aromatic compounds having -OH groups attached to them. These are subject to oxidation and side reactions which limit the amount of time that they can be utilized as fuels (or solvents) and also result in corrosion of metal and other surfaces.

Some quick pictures from the paper:

Lignin bio-oil composition:



The caption:

Figure 1. Total amount of oxygen in oxygenates determined by GC-MS vs the total amount of oxygen determined by elemental analysis in organic phase of bio-oil and products. The number on the right side of the red column is the share of the blue/red column.

The authors then treat the bio-oil with a nickel molybdenum catalyst as follows:

Before the hydrotreatment experiments, the bio-oil was first filtered to remove residual solids and then doped with 0.5 wt % dimethyl disulfide (Sigma-Aldrich, DMDS ? 99.0%) to maintain the catalyst activity as suggested by Yoshimura et al.(27) A commercial sulfided NiMo/Al2O3 catalyst (5.5 wt % of NiO and 28.3 wt % of MoO3) and hydrogen (SIAD, 99.9 vol %) were used in the continuous fixed-bed hydrotreatment experiments. Two sets of experiments were carried out. In the first one (further labeled as T/4), the temperature (T) was increased from 240 to 350 °C at a constant hydrogen pressure of 4 MPa. The second experiment set was labeled as T/P; the temperature (T) and hydrogen pressure (P) varied between 300–360 °C and 2–8 MPa, respectively. Compared to our previous paper,(25) the T/4 experiment was repeated with a greater emphasis on the reaction conditions around 300 °C and 4 MPa, where the density of the organic phase became lower than that of water for the first time. Therefore, the temperature change step between 280–330 °C was only 10 °C.

Results:



The caption:

Figure 2. Cumulative changes in wt % of the compounds representing each group of oxygenates and their distributions between the aqueous and organic phase.

Chemical pathways:




The caption:

Figure 3. Reaction scheme of the nonalkyl monocyclic compounds. Compounds: (1) syringol; (2) guaiacol; (3) pyrocatechol; (4) phenol; (5) cyclohexanol; (6) cyclohexanone; (7) benzene; (8) cyclohexene; (9) cyclohexane. Reactions: HYD, hydrogenation; DeMEOX, demethoxylation; DeMET, demethylation; HDO, hydrodeoxygenation; K-E, ketone/enol isomerization.

The caption:

Figure 4. Cumulative changes of the nonalkyl monocyclic compounds in the feed and all products.

The caption:

Figure 5. Content of 2-ethylphenol and 3-/4-ethylphenol in the feed and all the organic phases of products from the T/P experiment.

The caption:

Figure 6. Cumulative changes of the compounds with one ring substituted with propyl chain (propyl monocyclic compounds); the black lines separate the compounds that were transformed to 4-propylguaiacol (gray and light blue row) and 4-propylsyringol (brown and dark green row) through hydrogenation of the double bound in the propyl substituen

Some more reaction pathways:




The caption:

Figure 7. Reaction scheme of the propyl monocyclic compounds: (1) 4-allyl-syringol, (2) 4-(1-propenyl)syringol, (3) isoeugenol, (4) eugenol, (5) 4-propylsyringol, (6) 4-propylguaiacol, (7) 4-propylpyrocatechol, (8) 4-propylphenol, (9) propylbenzene, (10) 1-propylcyclohexene, (11) propylcyclohexane. Reactions: HYD, hydrogenation; DeMEOX, demethoxylation; DeMET, demethylation; HDO, hydrodeoxygenation; HYLY, hydrogenolysis. The compounds whose concentration is affected by the decomposition (hydrolysis) of pyrolytic lignin followed by subsequent deoxygenation of aldehydes and free hydroxyl groups are marked by red arrows.

The caption:

Figure 8. Cumulative changes in wt % by hydrocarbon groups A–D for the T/P and E–F for the T/4 experiment. i-Alkanes represent the sum of C5–C9 i-alkanes.

The next several graphs refer to chemical speciation. It is important to note that crude oil is also highly speciated before refining and processing.



The caption:

Figure 9. Amount of carboxylic acids in the organic phase (GC-MS vs CAN). The number on the right side of the blue row is the ratio of the red/blue row.

The caption:

Figure 10. Amount of carbonyls in the organic phase (GC-MS vs Faix method). The number on the right side of the blue row is the ratio of the red/blue row.

The caption:

Figure 11. Amount of phenols in the organic phase (GC-MS vs Folin–Ciocalteu method). The number on the right side of the blue row is the ratio of the red/blue row.

From the conclusion:

We presented the first detailed quantitative study mapping the fate of the individual key oxygenates during the one-stage hydrotreatment of straw bio-oil over a sulfided catalyst in a wide range of reaction conditions. Using a complex analysis of the aqueous and organic phases based on the combination of GC-MS analysis with functional-group-specific analytical methods (i.e., carboxylic acids, carbonyls and phenols determined by the carboxylic acid number, Faix, and Folin–Ciocalteu methods, respectively), we obtained a comprehensive understanding of the formation and/or consumption of oxygenates and hydrocarbons as a function of the reaction conditions used. Among the tested reaction conditions, one-stage bio-oil upgrading at 340 °C and 4 MPa is to be preferred, as there was no significant saturation of the aromatic ring while a majority of the oxygenates was removed. Thus, a sustainable product with minimum hydrogen consumption suitable for the subsequent coprocessing with petroleum fractions in a refinery was obtained. Moreover, the biobased aromatics are very desired components of the gasoline and jet-fuel blending pools.

Note that I am personally not interested in gasoline or jet-fuels, but these nasty fuels do contain valuable chemicals.

To the extent that such chemicals are utilized to make materials, and to the extent to which these chemicals are obtained from biomass, they are sequestered from the atmosphere.

We need to pay attention to such things, or at least the future generations we have screwed will need to do so.

The heat for these reactions is available from nuclear energy, which, as I state often, is the only sustainable form of primary energy available in time to save what is left to be saved.

Have a pleasant evening.

[hunter]

1. The graphics in your post won't be visible to someone who hasn't clicked the link you provided.

I opened your link to https://pubs.acs.org/doi/10.1021/acssuschemeng.8b06860 and then reloaded your post and the graphs appeared.

I can imagine straw as a feedstock for things like pharmaceuticals, some engineering plastics and lubricants, maybe some clothing, but if we use agricultural products for fuels and all the disposable plastic consumer crap affluent people are accustomed to then we'll be doing as much damage to the world as we would using petroleum or coal.

[NNadir]

2. We certainly do need to be careful with polymers.

Recently I've been thinking quite a bit about reformation reactions in seawater as a means of supercritical desalination, phosphorous recovery, and reviving ecosystems killed by eutrophic biomass outbreaks.

It occurs to me that given the large amount of microplastics in seawater, this might have the effect of releasing sequestered dangerous petroleum.

I'm not sure that completely banning polymers would be a very good idea for multi-use plastics, for example. To the extent that municipal waste is reformed, I don't really have a problem with them. The idea would be, to the extent possible, to have a closed system.

This said, single use plastics are an abomination to be sure, a very, very serious problem, but probably not as serious as climate change.

I have been meaning to calculate how large a cube of pure polyethylene would be if it were made from all the carbon dioxide we dump in a year from dangerous fossil fuels. Not counting land use changes, we are dumping about 35 billion tons of CO2 a year while we all wait for the grand "renewable energy" nirvana that never comes and frankly won't come. It would be a scary thing to look at to be sure.

There's no free lunch. The best we can do is combinatorial minimization of environmental impact. There are some carbon materials that are better than others.

Thanks for your perceptive comment. This sort of thing troubles me.

[NNadir]

3. This graphics thing seems to take place in Microsoft Explorer, not other browsers.

I didn't see it before, but I'm on a university computer that doesn't have Google Chrome, and I saw this.

I have no idea why this happens, but all the graphics work fine in Chrome..