Kinetics of Hydrogenation of Serine and Glutamic Acid in Aqueous

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Kinetics of hydrogenation of serine and glutamic acid in aqueous solution over a Ru/C catalyst Sachin G. Bhandare, and Prakash D. Vaidya Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.6b04406 • Publication Date (Web): 20 Mar 2017 Downloaded from http://pubs.acs.org on March 28, 2017

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Industrial & Engineering Chemistry Research

Kinetics of hydrogenation of serine and glutamic acid in aqueous solution over a Ru/C catalyst

Sachin G. Bhandare, Prakash D. Vaidya*

Department of Chemical Engineering, Institute of Chemical Technology, Nathalal Parekh Road, Matunga, Mumbai-400019, India

* Corresponding author (Tel.: +91 22 33612014; Fax: +91 22 33611020; Email: [email protected])

ACS Paragon Plus Environment


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Abstract Two amino acids, serine (or 2-amino-3-hydroxypropanoic acid) and glutamic acid (or 2-aminopentanedioic acid), are widely regarded as attractive, renewable platform chemicals. Catalytic hydrogenation of these amino acids to amino alcohols is a crucial step in making many useful products. In this work, the kinetics of hydrogenation of aqueous solutions of serine (SE) and glutamic acid (GA) was investigated over a heterogeneous Ru/C catalyst. Hydrogenation trials were performed in the kinetics-control regime in a batch reactor at 383 and 403 K. Serinol (or 2amino-1,3-propanediol) and 2-amino-1,5-pentanediol were the major hydrogenation products, correspondingly. The effects of the concentrations of the reactants (viz. amino acid and H2) and the catalyst on the rates of disappearance of the acids, and hence, the turnover frequency (TOF) were studied. Also, the influence of addition of phosphoric acid on the hydrogenation process was investigated. From power-law kinetics, the apparent energy of activation for the reactions with SE and GA was 42.3 and 53.9 kJ/mol, respectively. LHHW-type model was considered, too. A model that presumed a slow, dual-site surface reaction between competitively adsorbed amino acid and atomic H2 was used.


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1.

Introduction Amino acids are useful raw materials for making several industrial products.1 Especially,

they are applied in many sectors such as food, personal care, chemicals and pharmaceuticals (as nutrients, additives and drugs).2 Amino acids can be employed for manufacturing bulk chemicals too.3 They can be sustainably produced from biomass, and hence, are promising.2,4 Since amino acids have carboxylic acid and amine functionalities, useful information on their reactivity is widely reported.1 The production of amino alcohols from amino acids via catalytic hydrogenation is a crucial step in making many useful products.5-8 For instance, amino alcohols are of use for making surfactants, pharmaceuticals and fine chemicals.5,6 Hydrogenation of amino acids offers an opportunity to produce chiral compounds of superior enantiopurity.9 Both serine (SE or 2-amino-3-hydroxypropanoic acid) and glutamic acid (GA or 2-aminopentanedioic acid) have attracted much attention as prospective platform chemicals.2,10 The demand for SE is mainly in the pharmaceutical and cosmetic industry.1 Further, serinol (or 2amino-1,3-propanediol) made from SE hydrogenation is of use for making pharmaceutical agents such as antibiotics, X-ray opaque agents and many useful chemicals and intermediates.11 Using hydrogenation, decarboxylation and cyclization reactions for making valuable products from GA is not uncommon.12,13 The catalytic hydrogenation of α-amino acids, producible from biomass, to amino alcohols is renowned. For instance, Metekar et al.14 investigated mild aqueous-phase hydrogenation of the carboxylic group in lysine over Ru/C catalyst and the reaction conditions were so: temperature 373 to 423 K, pressure 4.8-7 MPa. High yield of lysinol was reported (>90%). After purification, the isolated yield was 50-70%. Pimparkar et al.15 investigated hydrogenation of different amino acids such as valine, serine and alanine at 7 MPa H2 pressure and 403 K over Ru/C catalyst. While the reactions with serine and alanine were fast, valine hydrogenation was slower. Alaninol and valinol were selectively formed (>90% selectivity); however, serinol degradation resulted in



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less-than-desired selectivity. Holladay et al.9 reported that valuable chemical intermediates can be produced from hydrogenation of GA over Ru/C. Interestingly, this reaction system is unique than hydrogenation of other amino acids.9 Usually, severe conditions (>473 K, 5–14 MPa) are employed for hydrogenating carboxylic acids to alcohols even with active catalysts.16 In the present work, we investigated hydrogenation of SE and GA in aqueous solutions over Ru/C catalyst. Trials were performed in the kinetics-control regime in a batch reactor at 383 and 403 K. The effects of the concentrations of the reactants, viz. amino acid and H2, and the catalyst on the rates of disappearance of the acids, and hence, the turnover frequency (TOF) were studied. Also, the influence of addition of phosphoric acid on the hydrogenation process was investigated. Finally, heterogeneous power-law type and Langmuir-Hinshelwood-HougenWatson (LHHW) type models were considered too. So far, there is scarce kinetic data available in the literature for the investigated reaction systems. However, the importance of catalytic hydrogenation kinetics and modelling for compounds derived from ligno-cellulosic biomass cannot be overemphasized. This is evident from the large effort focused on the hydrogenation of biomass precursors over noble and nonnoble metal catalysts. For example, Grilc et al.17 reported concurrent liquefaction and hydrodeoxygenation of lignocellulosic biomass in solvents that donate hydrogen. They employed NiMo/Al2O3, Pd/Al2O3 and Zeolite Y catalysts for their study. In another investigation,18 solvolysis of biomass was performed in glycerol and imidazolium-based ionic liquids. After that, Ni-Mo catalyst was used for hydrodeoxygenation. Besides, the performance of oxidized, reduced and sulfided NiMo, Ni, Mo and Pd catalysts for deoxygenation and hydrocracking of solvolysed lignocellulosic biomass was also investigated. Especially, reaction kinetics was studied using levulinic acid, guaiacol and hydroxymethyl furfural (HMF).19 Our long-term interest in this field of mild hydrogenation of oxygenates originating from biomass, using water as the reaction medium, also led us to undertake this work.20-25


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2.

Experimental

2.1. Materials Serine and serinol (purity 99.9%) were purchased from Alfa Aesar Pvt. Ltd., Mumbai. Glutamic acid (99.9%), phosphoric acid (AR grade), sulphuric acid (98%) and acetonitrile (HPLC grade) were purchased from S. D. Fine Chemicals Pvt. Ltd., Mumbai. Inox Air Products, Mumbai, was the provider of cylinders containing H2 and N2 (purity 99.9 %). Arora-Matthey Ltd., Kolkata, supplied Ru/C catalyst (metal loading 5%).

2.2. Setup and Procedure Hydrogenation runs were performed in a 0.1 dm3 capacity autoclave (Parr Instruments Co., USA, model 4848) made of Hastealloy. The reactor was heated electrically and stirred with a turbine agitator. Using a controller, temperature (accuracy 1 K) and agitation speed (accuracy 1 rpm) were controlled. The reactor was provided with two valves, one, for charging H2, and the other, for venting gas. A third valve was provided, together with a chilled water condenser, to periodically collect samples of the reaction mixture. Reactor pressure was read from a pressure gauge (0-2000 psi) with an accuracy of 1%. Before each trial, it was ensured that the reactor assembly had no leak. Typically, 50 mL (or 5×10-5 m3) of aqueous solution of amino acid (A) and known amount of fresh Ru/C catalyst were charged into the reactor. After purging with N2 to ensure inert atmosphere, stirring was started (speed 1200 rpm) and the reactor was heated (heating rate 5 K/min). When the desired reactor temperature (e.g., 383 or 403 K) was reached (usually within 20 min), H2 was charged into the reactor at the desired pressure. More H2 was charged during reaction to make up for the amount lowered by reaction and sampling. Thus, the total pressure was fixed. Vapor pressure of water also contributed to total pressure. Although total pressure



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was held constant, the gas phase composition was varying. The reactions were carried out for 3.5 hours. Liquid samples (0.5 mL) were withdrawn at particular time intervals and analyzed.

2.3. Analysis of Products For analysis of samples, high pressure liquid chromatography (HPLC) technique was used. The HPLC unit (Agilent Technologies) was provided with an injection loop, detector (UV and RI), quaternary pump, degassing unit and Chem Station software. A Cosmosil reverse phase column (5C18-MS-II, 250×4.6 mm, Nacalai USA, Inc.) was employed for detecting SE (retention time 3.47 min), serinol (4.14 min), GA (3.671 min), 2-amino-1,5-pentanediol (4.476 min) and proline. A mixture of 5 mM H2SO4 50% and ACN 50% (flow rate = 0.7 mL/min) was used as the mobile phase. The RI detector was set at a temperature of 313 K. The formation of products was validated by using LC-MS technique (Finnigan LCQ Advantage Max, Thermo Electron Corporation). The experimental error was found to be less than 3% when reproducibility of experiments was checked.

2.4. Catalytic Features For studying the catalyst morphology, SEM technique (JEOL-JSM 6380 LA Scanning Electron Microscope) was used. Honeycomb identical pores are visible in Fig. 1. Using N2 adsorption-desorption isotherm at 77.5 K and the renowned Brunauer–Emmett–Teller (BET) technique, surface area (793 m2/g), average pore diameter (2.2 nm) and micropore volume (0.4 cm3/g) of the unused catalyst were found. The particle size (dp=94 µm) was approximately calculated by using Beckman Coulter LS-make particle size analyzer. High surface area and porosity and low particle size were beneficial for the investigated catalytic reaction systems. Micromeritics 2920 instrument was used for Hydrogen-Temperature Programmed Reduction (H2-TPR) studies. The initial and final temperatures for H2 chemisorption were 393 and 773 K,


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whereas reduction pre-treatment was done at 573 K. In a U-tube quartz reactor, 50 mg of catalyst was kept. A 10% H2-Ar mixture (flow 20.1 cm3/min) was used for reduction. The amount of H2 consumed was found using a thermal conductivity detector (TCD). A major reduction peak, extending from 200-220oC, was seen; this peak is due to the transformation of Ru (III) to metallic Ru. The investigated catalyst showed maximum reduction at 200-220oC. This is in line with its superior activity for hydrogenation. The presence of Ru0, which is responsible for catalyzing the hydrogenation reaction, was evident. The average particle diameter was 48.2 nm, whereas the metal dispersion was 2.74%. To get the XRD patterns, a diffractometer (Rigaku Miniflex D500) and monochromic CuKa radiation operating at 40 kV and 25 mA was used. The patterns were for 2θ values ranging from 5 to 90° with a scanning speed of 0.1/s (see Fig. 2). A prominent peak for carbon was visible at 2θ=25.6°. Diffraction peaks at 2θ=43o were for Ru species. As evident from the broad peak for activated carbon, the catalyst was amorphous. No new peaks or phases were seen in the spent catalyst.

2.5. Mass Transfer Considerations Mass-transfer processes for H2 and amino acids often influence the rates of three-phase hydrogenation systems.8 For that reason, it was made sure that all mass transfer resistances were insignificant. To ascertain the effect of the gas–liquid and liquid-solid interfacial mass transfer on the hydrogenation rate, the method reported by Bindwal and Vaidya24 was used. The external mass transfer was checked at 423 K by varying the agitation speed (300-1400 rpm). It was found that there is no change in the rate above a speed of 900 rpm. So it was concluded that gas-liquid and liquid-solid resistances were absent at 1200 rpm. The well-known Weisz-Prater criterion was used to test the significance of intra-particle diffusion.26 The parameter η was calculated using the relation: η =

ω

,

where i = A, H2


(1)


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Here, r, ω and L denote reaction rate, catalyst loading and the characteristic length of the spherical catalyst particle (= dp/6, where dP = 94 µm). The value of CH2 (kmol/m3) was estimated by using a correlation suggested by Pintar et al.27 C =

(2)

where the dimensionless mole fraction solubility xg is given by the relation28 !

= exp %−125.939 +

../.0. 1

+ 16.8893 ln(T)9

(3)

To find the liquid-phase effective diffusivities of amino acids (SE and GA) and H2, the WilkeChang equation was used.29 It was found that, in this work, the value of η for both the reactants was much less than unity. Thus, all results indicated conformation to the kineticscontrol regime. The reaction conditions used in this work for SE hydrogenation were so: 383-423 K, 0.69-2.76 MPa, 13-38 mM SE and 0.5-1.5 kgcat/m3. For the reaction with GA, the conditions were 383-423 K, 0.69-2.76 MPa, 10-31 mM SE and 0.6-1.8 kgcat/m3. From C vs. t plots (raw data), reaction rates were found from the slopes (-dC/dt) of the tangents using least square regression. Knowing the fractional metal dispersion D, the turnover frequency (TOF) was calculated as follows: TOF = % 0

r × MRu

3.

D

9 (4)

Results and Discussion

3.1. Hydrogenation of SE and GA All hydrogenation reactions were performed in the kinetic regime. The reaction pathways at the conditions employed in this work are described in Fig. 3. Serinol was the major product for the reaction with SE. 2-Amino-1,5-pentanediol was the major product of GA hydrogenation, whereas proline was formed in trace amount. Since amino alcohol is basic, it reduces the electrophilicity of carbonyl carbon atom. As a result, the reaction shifts more towards the left


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side. The role of phosphoric acid is to facilitate the formation of the zwitterion, which is then readily transformed into the amino alcohol.30 The effect of addition of the mineral acid H3PO4 on the hydrogenation of SE and GA was investigated at T=403 K and P =0.69 MPa. The initial concentrations of SE and GA were 25 and 20 mM. The results are shown in Figs. 4a and 4b correspondingly. When no phosphoric acid was added, the conversion was low (9 and 6% for SE and GA). After H3PO4 was added (25 mM), the amino acid conversion was markedly higher. In an earlier work, Tamura et al.30 reported that the alcohol was selectively formed when no acid was added; however, the yield was low. The effect of catalyst loading (ω) on the rate of disappearance of SE and GA was studied at 383 and 403 K. The value of P was 0.69 MPa, whereas the initial concentrations of SE and GA were 25 and 20 mM. The results are represented in Figs. 5a (for SE) and 5b (for GA). It is evident that the initial reaction rate increased linearly with catalyst loading. Thus, it can be concluded that the reaction is of the first order with respect to the catalyst concentration. Also, it proved that that the reaction rates were not influenced by the rates of mass transfer. The effect of the initial TOF values on H2 partial pressure for the reactions with SE and GA were investigated in the 0.69-2.07 MPa range at 383 and 403 K. The results are depicted in Figs. 6a (for SE) and 6b (for GA). The other parameters were so: catalyst loading=1 kg/m3, initial concentrations 25 mM (for SE) and 20 mM (for GA). A three-fold rise in TOF was seen when P was increased from 0.69 to 2.07 MPa. Clearly, the dependence of initial TOF on P was linear. These results suggest first-order kinetics with H2. The dependency of TOF on the amino acid concentration in feed is shown in Figs. 7a (for SE) and 7b (for GA). Trials were performed at T=403 K and P = 0.69 MPa. Feed solution containing 13, 25 and 38 mM SE and 10, 20 and 31 mM GA were employed. It was found that TOF values increased with rising amino acid concentration in feed.



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A power-law model, represented by eq. 5, was used to estimate kinetic parameters: r< = k · (P ) n · (CA,0) m

(5)

The H2 reaction order (n), as determined from POLYMATH by using eq. (5), was 1.03 (at 383 K) and 1.13 (at 403 K) for the reaction with SE and 0.95 (at 383 K) and 0.99 (at 403 K) for the reaction with GA. The reaction order with respect to amino acid (m) was found to be 0.49 and 0.50 for the reaction with SE and 0.61 and 0.65 for the reaction with GA at 383 and 403 K, correspondingly. This suggests that SE and GA were strongly adsorbed on the catalyst. The influence of the reaction temperature was studied in the 383-403 K range at P =0.69 MPa using 25 and 20 mM solutions of SE and GA. As expected, reaction rate increased with the rise in temperature. The apparent energy activation (EA) was determined by fitting an Arrhenius-type relation and the values for the reactions with SE and GA were found to be 42.3 and 53.9 kJ/mol, respectively. The fact that hydrogenation over Ru/C yielded a fractional reaction order with respect to SE and GA indicates that the interaction of SE and GA with the active sites on the catalyst surface is strong. In contrast, the first order with respect to H2 indicates that, at the employed reaction conditions, the interaction of H2 is weak. In order to elucidate the aforesaid inferences on reaction orders, LHHW-type kinetic model was considered.

3.2. Reaction Mechanism A LHHW model was employed for describing the kinetic behavior of the investigated reaction systems. It is well-known that H2 dissociates almost immediately upon binding with Ru. Also, it is probably safe to assume that the adsorption of amino acid and H2 is indeed competitive, as both species are chemisorbed onto Ru, which is almost definitely covered by species. Therefore, a competitive LHHW model with a slow surface reaction between dissociatively chemisorbed H2 and adsorbed amino acid was considered. The individual steps of this mechanism are denoted by (A=amino acid, P=amino alcohol):


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H2 + 2 S

k1 , k-1

=>>?

fast

2H–S

(6)

B , BD

A + S =>>>? A ̶ S fast (7) A ̶ S + 2 H ̶ S P–S

k4 , k-4

=>>?

k3 , k-3

=>>?

P – S + 2 S

P+S

slow

(8)

fast

(9)

When step 8 is rate-controlling, the expression for initial rate is denoted by eq. 10: r =

k3 KH2 KN CH2 CA

3

1/2 O1 + K1/2 H2 CH2 + KA CA P

1/2 Since H2 is weakly adsorbed, the term K1/2 H2 CH2 in the denominator in eq. 10 can be neglected.

Eq. 10 can be simplified to: r =

k3 KH2 KN CH2 CA (1 + KA CA )3

The above eq. 11 is in agreement with the reaction orders determined by the power-law model, viz. fractional with respect to amino acid (between 0 and 1) and integer for H2 (unity).

4.

Conclusions In the present work, two biomass-derived amino acids serine (SE) and glutamic acid (GA)

were hydrogenated to the respective amino alcohols, 2-amino-1,3-propanediol and 2-amino-1,5pentanediol in aqueous solution over Ru/C. It was found that the investigated reaction systems belong to the kinetic-control regime. The dependency of rates (and TOF) on temperature, H2 partial pressure and initial reactant concentration was studied. The reaction conditions used in this work for SE hydrogenation were so: 383-423 K, 0.69-2.76 MPa, 13-38 mM SE and 0.5-1.5 kgcat/m3. For the reaction with GA, the conditions were 383-423 K, 0.69-2.76 MPa, 10-31 mM SE and 0.6-1.8 kgcat/m3. The addition of phosphoric acid facilitated the formation of amino alcohols. A power-law type kinetic model suggested first order with respect to H2 and fractional order (between 0 and 1) for the amino acid. Finally, the inferences drawn from the power-law



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model were elucidated by a LHHW-type model. This model presumed that the surface reaction between competitively adsorbed amino acid and atomic H2 was rate-determining.

Acknowledgment Sachin G. Bhandare is grateful to University Grants Commission, New Delhi, for the financial support (Green Tech. F.8-10/2007 (BSR)).

Nomenclature A

reactant in the liquid phase

CA,0

concentration of the reactant in the liquid phase, kmol/m3

CH2

concentration of H2 in the liquid phase, kmol/m3

D

fractional metal dispersion

k3

surface reaction rate constant, kmol/(kgcat min)

KH2

adsorption equilibrium constant for H2, m3/kmol

KA

adsorption equilibrium constant for the reactant, m3/kmol

MRu

molecular weight of ruthenium, g/mol

P

total operating pressure, MPa

r

rate of reaction, kmol/(kgcat min)

r0

initial rate of reaction, kmol/(kgcat min)

TOF

turnover frequency, 1/min

X

fractional conversion

α

Henry’s law constant, kmol/(m3 kPa)

Greek symbols ρ

Q

density of water, kg/m3


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ω

catalyst loading, kg/m3

η

effectiveness factor

ϕ

Thiele modulus

ηϕ2i

observable modulus for species i in Eq. 1

Literature Cited (1) Scott, E.; Peter, F.; Sanders, J. Biomass in the manufacture of industrial products-the use of proteins and amino acids. Appl. Microbiol. Biotechnol. 2007, 75, 751-762. (2) Sheldon, R. A. Green and sustainable manufacture of chemicals from biomass: state of the art. Green Chem. 2014, 16, 950-963. (3) Sanders, J.; Scott, E.; Weusthuis, R.; Mooibroek, H. Bio-refinery as the bio-inspired process to bulk chemicals. Macromol. Biosci. 2007, 7, 105-117. (4) Eggeling, L.; Sahm, H. Amino acid production. Appl. Microbiol. Ind. 2009, 1, 150-158. (5) Antons, S.; Tilling, A. S.; Wolters, E. Method for producing optically active amino alcohols, US Patent 6,310,254, 2001. (6) Antons, S.; Beitzke B. Process for preparing optically active amino alcohols, US Patent 5,536,879, 1996. (7) Jere, F. T.; Miller, D. J.; Jackson, J. E. Stereoretentive C-H bond activation in the aqueous phase catalytic hydrogenation of amino acids to amino alcohols. Org. Lett. 2003, 5, 527. (8) Jere, F. T.; Jackson, J. E.; Miller, D. J. Kinetics of the aqueous-phase hydrogenation of L-alanine to L-alaninol. Ind. Eng. Chem. Res. 2004, 43, 3297-3303. (9) Holladay, J. E.; Werpy, T.A.; Muzatko, D. S. Catalytic hydrogenation of glutamic acid. Appl. Biochem. Biotechnol. 2004, 115, 857-868. (10) Schaffer, S.; Haas, T. Biocatalytic and fermentative production of α,ω-bifunctional polymer precursors. Org. Process Res. Dev. 2014, 18, 752-766.



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(11) Andreeben, B.; Steinbuchel, A. Serinol: small molecule – big impact. AMB Express, 2011, 1-12. (12) Lammens, T. M.; Potting, J.; Sanders, J. P. M.; De Boer, I. J. M. Environmental comparison of biobased chemicals from glutamic acid with their petrochemical equivalents. Environ. Sci. Technol. 2011, 45, 8521-8528. (13) Lammens, T. M.; De Biase, D.; Franssen, M. C. R.; Scott, E. L.; Sanders, J. P. M. The application of glutamic acid a-decarboxylase for the valorization of glutamic acid. Green Chem. 2009, 11, 1562. (14) Metkar, P. S.; Scialdone, M. A; Moloy, K. G. Lysinol: a renewably resourced alternative to petrochemical polyamines and amino alcohols. Green Chem. 2014, 16, 4575-4586. (15) Pimparkar, K. P.; Miller, D. J.; Jackson, J. E. Hydrogenation of amino acid mixtures to amino alcohols. Ind. Eng. Chem. Res. 2008, 47, 7648-7653. (16) Nishimura S. Handbook of heterogeneous catalytic hydrogenation for organic synthesis, John Wiley & Sons, 2001. (17) Grilc, M.; Likozar, B.; Levec, J. Simultaneous liquefaction and hydrodeoxygenation of lignocellulosic biomass over NiMo/Al2O3, Pd/Al2O3, and Zeolite Y catalysts in hydrogen donor solvents. ChemCatChem. 2016, 8, 180-191. (18) Grilc, M.; Likozar, B.; Levec, J. Kinetic model of homogeneous lignocellulosic biomass solvolysis in glycerol and imidazolium-based ionic liquids with subsequent heterogeneous hydrodeoxygenation over NiMo/Al2O3 catalyst. Catalysis Today. 2015, 256, 302-314. (19) Grilc, M.; Likozar, B.; Levec, J. Hydrodeoxygenation and hydrocracking of solvolysed lignocellulosic biomass by oxide, reduced and sulphide form of NiMo, Ni, Mo and Pd catalysts. Appl. Catal. B: Environ. 2014, 150–151, 275-287. (20) Jain, A. B.; Vaidya, P. D. Kinetics of the ruthenium-catalyzed hydrogenation of levulinic acid to γ-valerolactone in aqueous solutions. Can. J. Chem. Eng. 2016, 94, 2364-2372.


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(21) Jain,

A.

B.;

Vaidya,

P.

D.

Kinetics

of

catalytic

hydrogenation

of

5-

hydroxymethylfurfural to 2,5-bis-hydroxymethylfuran in aqueous solution over Ru/C. Int. J. Chem. Kin. 2016, 48, 318-328. (22) Jain, A. B.; Vaidya, P. D. Kinetics of aqueous-phase hydrogenation of model bio-oil compounds over a Ru/C catalyst. Energy Fuels 2015, 29, 361-368. (23) Bindwal, A. B.; Vaidya, P. D. Reaction kinetics of vanillin hydrogenation in aqueous solutions using a Ru/C catalyst. Energy Fuels 2014, 28, 3357-3362. (24) Bindwal A. B.; Vaidya P.D. Kinetics of aqueous-phase hydrogenation of levoglucosan over Ru/C catalyst. Ind. Eng. Chem. Res. 2013, 52, 17781-17789. (25) Bindwal A. B.; Bari, A. H.; Vaidya P.D. Kinetics of low temperature aqueous-phase hydrogenation of model bio-oil compounds. Chem. Eng. J. 2012, 207-208, 725-733. (26) Fogler, H. S. Elements of Chemical Reaction Engineering; Prentice-Hall of India, New Delhi, India, 2008. (27) Pintar, A.; Bercic, G.; Levec, J. Catalytic liquid-phase nitrite reduction: kinetics and catalyst deactivation. AIChE J. 1998, 44, 2280-2292. (28) Fogg, P. G. T.; Gerrard, W. Solubility of Gases in Liquids; Wiley Sons, Chichester, England, 1991. (29) Wilke, C. R.; Chang, P. Correlation of diffusion coefficients in dilute solutions. AIChE J. 1955, 1, 264-270. (30) Tamura M.; Tamura R.; Takeda Y.; Nakagawa Y.; Tomishige K. Insight into the mechanism of hydrogenation of amino acids to amino alcohols catalyzed by a heterogeneous MoOx-modified Rh catalyst. Chem. Eur. J. 2015, 21, 3097-3107.

LIST OF FIGURES Fig. 1. SEM images of the fresh Ru/C catalyst



Page 16 of 24 16

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Fig. 2. XRD images of fresh and spent Ru/C catalyst Fig. 3. Reaction schemes of SE and GA hydrogenation Fig. 4. Effect of mineral acid H3PO4 at T=403 K for hydrogenation of (a) SE (CSE,0=25 mM, ω=1 kg/m3, PH2 =0.69 MPa) and (b) GA (CGA,0=20mM, ω=1.2 kg/m3, PH2 =0.69 MPa) Fig. 5. Effect of catalyst loading on the initial rates at 383 and 403 K for hydrogenation of (a) SE (CSE,0=25 mM, PH2 =0.69 MPa) and (b) GA (CGA,0=20 mM, PH2 =0.69 MPa) Fig. 6. Effect of H2 partial pressure (PH2 ) on the initial TOF values at 383 and 403 K for hydrogenation of (a) SE (CSE,0=25 mM, ω=1 kg/m3) and (b) GA (CGA,0=20 mM, ω=1.2 kg/m3) Fig. 7. The dependence of the initial TOF values on initial SE and GA concentration at various temperatures for hydrogenation of (a) SE (PH2 =0.69 MPa, ω=1 kg/m3) and (b) GA (PH2 =0.69 MPa, ω=1.2 kg/m3)


Page 17 of 24


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Fig. 1



Page 18 of 24 18

9000

7500

Counts (Arbitrary units)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

6000

Ru/C spent

4500

3000

1500

Ru/C Fresh

0 5

15

25

35

45

55

2Ɵ

Fig. 2


65

75

85

Page 19 of 24


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

O

HO

O

H3PO4

OH

HO

Ru/C

O-

HO

OH NH2

NH2

NH3+

Serinol

Zwitter ion

Serine

Fig. 3a

O

O

O

HO

OH NH2

Glutamic acid

H3PO4

O O

HO

Ru/C

NH3+

Zwitter ion

Fig. 3b


HO

OH NH2

2-amino-1,5-pentanediol


Page 20 of 24 20

80

a

With Phosphoric acid

70

Without phoshoric acid

% Conversion

60

50

40

30

20

10

0 0

1

2

3

4

Time (h)

Fig. 4a 80

b

With phosphoric acid 70 Without phophoric acid 60

% Conversion

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

50

40

30

20

10

0 0

1

2 Time (h)

Fig. 4b


3

4

Page 21 of 24


0.8

383 K 403 K

Initial rate (kmol/(m3 min))

0.6

0.4

0.2

a 0 0

0.4

0.8

1.2

1.6

2

Catalyst loading (kg/m3)

Fig. 5a 0.6 383 K 0.5 403 K

Initial rate (kmol/(m3 min))

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

0.4

0.3

0.2

0.1

b 0 0

0.4

0.8

1.2

Catalyst loading (kg/m3)

Fig. 5b


1.6

2


Page 22 of 24 22

1.6

383 K 403 K

Initial TOF (1/min)

1.2

0.8

0.4

a 0 0

0.8

1.6

2.4

H2 partial pressure (MPa)

Fig. 6a 1

383 K 0.8

Initial TOF (1/min)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

403 K

0.6

0.4

0.2

b 0 0

0.5

1

1.5

H2 partial pressure (MPa)

Fig. 6b


2

2.5

Page 23 of 24


0.90

383 K 0.75

403 K

Initial TOF (1/min)

0.60

0.45

0.30

0.15

a 0.00 0

10

20

30

40

CA,0 (mM)

Fig. 7a

0.40

383 K 403 K 0.30

Initial TOF (1/min)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

0.20

0.10

b 0.00 0

10

20 CA,0 (mM)

Fig.7b


30


Page 24 of 24 24

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Table of Contents Graphic

O

HO

O

H3PO4

OH

HO

Ru/C

O-

HO

OH NH2

NH2

NH3+

a

Zwitter ion

Serine

O

O

O

HO

OH NH2

Glutamic acid

H3PO4

Serinol

O O

HO

Ru/C

NH3+

Zwitter ion


HO

OH NH2

2-amino-1,5-pentanediol

Kinetics of Hydrogenation of Serine and Glutamic Acid in Aqueous

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