Supporting Information

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1 Supporting Information An acid-free conversion of cellulose to -hydroxymethyl-furfural catalyzed by hot Seawater Xiangcheng Li, Yayun Zhang, Qineng Xia, Xiaohui Liu, Kaihao Peng, Sihai Yang, * Yanqin Wang * Shanghai Key Laboratory of Functional Materials Chemistry, Research Institute of Industrial Catalysis, School of Chemistry and Molecular Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai, 0037, P. R. China. Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Ministry of Education, College of Power Engineering, Chongqing University, Chongqing , China. Bioproducts, Sciences and Engineering Laboratory, Department of Biological Systems Engineering, Washington State University, Richland, WA , USA. School of Chemistry, University of Manchester, Manchester, M13 9PL, UK. * Correspondence s:sihai.yang@manchester.ac.uk; wangyanqin@ecust.edu.cn. S1

2 Lignin hydrodeoxygenation and details of alkylcyclohexanes analysis. The hydrodeoxygenation of lignin was conducted in a 0 ml Teflon-lined stainless-steel autoclave. In a typical run, lignin residue (0.10 g), %Pt/NbP 4 (0.0 g) and cyclohexane (10 ml) were charged in the reactor, which was then sealed, purged three times with and charged to an initial pressure of 3.0 MPa with. The reactor was then slowly heated to 0 C with a magnetic stirring speed of 700 rpm and held at this temperature for 0 h. After the reaction, the reactor was cooled down quickly. The amounts of alkylcyclohexanes were analysed by gas chromatography (GC) and GC-mass spectroscopy (GC-MS) on an Agilent 7890B gas chromatograph with flame ionisation detector (FID) and an Agilent 7890A GC-MS instrument, both equipped with P- capillary columns. Tridecane was added as an internal standard. The mole yield of C 7 ~C 9 cycloalkanes was defined as follows: mole of C 7 ~C 9 cycloalkanes produced (µmol/g lignin) Mole yield of C 7 ~C 9 cycloalkanes= mole of C 7 ~C 9 hydrocarbons obtained by NB method (µmol/g lignin) The mass yield of liquid alkanes was defined as follows: mass of alkylcyclohexanes Mass yield of alkylcyclohexanes = mass of lignin residues Analysis of lignin monomers by alkaline nitrobenzene oxidation method (NB). The analysis of birch lignin monomers was conducted by alkaline nitrobenzene oxidation method (NB) according to literature. 1 In a typical reaction, birch lignin (40 mg) was mixed with nitrobenzene (0.4 ml) and M Na (7 ml) and reacted at 170 C for h. Afterwards, the reactor was cooled in ice-water and 1 ml of freshly prepared ethyl vanillin (3-ethoxy-4-hydroxybenzaldehyde, EV) ( µmol/ml) in 0.1 M Na solution was added to the reaction mixture as an internal standard. The mixture was transferred to a 100-mL separation funnel and washed three times with 1 ml of dichloromethane. The remaining aqueous layer was acidified with M, until the p was below 3.0 and extracted twice with 0 ml of dichloromethane and 0 ml of diethyl ether. The combined organic layer was S

3 washed with deionised water (0 ml) and dried over Na S 4. After filtration, the filtrate was collected in a 100-mL pear-shaped flask and dried under reduced pressure. For the TMS (trimethylsilyl) derivatisation step, NB-products were washed with pyridine (3 00 µl) into a GC vial and BSTFA (10 µl) was added. The mixture was heated to 0 C for 30 min. The silylated NB-products were analyzed by GC-MS (Agilent 7890A GC-MS) equipped with ap- capillary column (30 m 0 µm) to identify the products by the comparison with the peak retention time and mass spectra of the authentic compounds. The identified products were quantified by GC-FID (Agilent 7890B) using the same column. Initial column temperature: 10 C (held for 10 min), raised at C/min to 80 C (held for 0 min). Intensity micro-crystalline cellulose ball-milled cellulose Theta/degree Figure S1. XRD patterns of the micro-crystalline and ball-milled cellulose. S3

4 Table S1. Analysis of the components of seawater a. Sea water (original, ca. 3wt% salts) Sea water (concentrated, ca. 1wt% salts) b Sea water (concentrated, ca. 30wt% salts) b Ions Percentage of simulated Percentage of Percentage of seawater (g/kg) simulated seawater simulated seawater (g/kg) (g/kg) Na S Mg K Ca Total a the components of seawater were analysed by ion chromatography (ICS1100). b As the salts concentration increases, the Ca +, S 4 - are gradually salted out in the form of CaS 4. S4

5 Table S. Yields of MF and furfural obtained from microcrystalline cellulose and various sources of lignocellulosic biomass in the TF/seawater system. Entry Sample Glucan (wt%) Xylan (wt%) The Molar Yield (%) The Mass Yield (%) MF Furfural MF Furfural Total 1 a Microcrystalline cellulose b Cornstalk b Pine b Birch b Poplar a Reaction condition: wt% cellulose, 0. M N, 1 ml concentrated seawater (ca. 30wt% salts), 6 ml TF, 00 C, 6 h; b Reaction condition: wt% biomass, 0. M N, 1 ml concentrated seawater (ca. 30wt% salts), 6 ml TF, 00 C, h. The compositions of lignocellulosic biomass were adapted from ref. according to the procedures of the Van Soest method. S

6 Conversion/Selectivity Cellulose conversion; Glucose selectivity; Fructose selectivity; MF selectivity 0 wt% 10wt% Cellulose concentration 0wt% Figure S. Influence of the cellulose concentration on the products distribution of cellulose conversion in the TF/seawater system. Reaction condition: 0.M N, 1 ml concentrated seawater (ca. 30wt% salts), 6mL TF, 00 C, 6 h. S6

7 (A) Weight (%) (B) Weight (%) TGA umins (cellulose) 449. DTA Temperature ( o C) Lignin residue 493 TGA DTA 36wt% Temperature ( o C) eat Flow Endo Down (mw) eat Flow Endo Down (mw) Figure S3. Thermal analysis of (A) humins (cellulose) and (B) lignin residue in air. The TGA curve shows that one weight loss region is observed and centered at 449. C for humins sample. When temperature reached to 470 C, almost all humins was pyrolyzed. While the lignin residue pryolysis was focused at C with the maximum weight loss rate at 493 C, and ca. 36 wt% may be considered the lignin content of lignin residue based on the weight loss after 470 C. S7

8 Table S3. Summary of product yields from direct hydrodeoxygenation of lignin residues over the Pt/NbP 4 catalyst. a Substrate Products distribution (wt%) C 7 ~C 9 cycloalkanes thers b Total mass Yield (%) Birch a Reaction conditions: lignin 0.1 g, catalyst 0. g, cyclohexane 1 ml, 0 C, MPa, 0 h. The metal loading in catalyst was wt%. b S8

9 Table S4. Representative GC-MS spectra of liquid products obtained from birch lignin conversion for 0 h over the Pt/NbP 4 catalyst. GC Spectra No. Ret. time (min) Compound No. Ret. time (min) Compound C 13 6 (Standard) S9

10 µmol monomers/g lignin C7~C9 cycloalkanes S G 0 NB D Figure S4. Monomer analysis of lignin residues. NB refers to the nitrobenzene oxidation method; D refers to direct hydrodeoxygenation over Pt/NbP 4 ; S refers to syringy units; G refers to guaiacyl units. The corresponding carbon yield of C 7 ~C 9 hydrocarbons is ca. 89.3% based on lignin monomers. Conversion/Selectivity Cellulose conversion; Glucose selectivity; Fructose selectivity; MF selectivity Reaction time (h) Figure S. Influence of reaction time on the products distribution of cellulose conversion in the TF/Na- system. Reaction condition: wt% cellulose, 30wt% Na, 0. M N, 1mL, 6mL TF, 00 C. S10

11 Table S. Products distribution of cellulose conversion catalyzed by a range of salts from seawater. Entry Salt Conv. S MF Y MF Y glucose Y fructose Y LA Y humins 1 Blank a Blank Na K Mg > Ca > b Mg b Ca Na S Reaction condition: wt% cellulose, 30wt% salts, 0.M N, 1mL, 6mL TF, 00 C, h. a reaction time : 6 h. b reaction time : 40 min. S11

12 Table S6. Products distribution of cellulose conversion catalyzed by a range of neutral chloride-, bromide-based salts, N 4 and. Entry Salt Conv. S MF Y MF Y glucose Y fructose Y LA Y humins 1 Blank Li > Na > K > LiBr > NaBr > KBr > a N 4 > b > Reaction condition: wt% cellulose, 30wt% salts, 0.M N, 1mL, 6mL TF, 00 C, 8 h. a reaction time : h. b catalyst: wt%, reaction time : h. S1

13 Table S7. Influence of temperature on the products distribution of cellulose conversion in the TF/Na- system. Entry Temperture / C Conv. S MF Y MF Y glucose Y fructose Y LA Y humins 1 a a a > a > Reaction condition: wt% cellulose, 30wt% Na, 0. M N, 1mL, 6mL TF, 8 h. a reaction without the addition of Na. Conversion/Selectivity Cellulose conversion; Glucose selectivity; Fructose selectivity; MF selectivity 0 Blank wt% 10wt% Na 0wt% 30wt% Figure S6. Influence of Na concentration on the products distribution from cellulose conversion in the TF/Na- system. Reaction condition: wt% cellulose, 0. M N, 1mL, 6mL TF, 00 C, 8 h. S13

14 Conformational 3 3 Ring opening 4 transition 6 - transfer R pathway 1 1-I1 1-I 1-I3 1-I4 ff Ring opening R pathway -I1 -I I3 Conformational 3 transition ff Ring opening R pathway transfer I1 3-I 3-I I4 4 6 Conformational transition ff 4 6 with Ring opening transfer R pathway 1 cl-1-i cl-1-i3 cl-1-i Ring opening R pathway cl--i cl--i1 3 Conformational 3 4 transition cl-1-i4 ff 3 4 Conformational 3 transition cl--i3 ff Ring opening R cl-3-i1 pathway cl-3-i 6 transfer cl-3-i cl-3-i4 6 Conformational transition ff Scheme S1. Reaction pathways of glucose conversion to fructose with and without -. nly one - was added here to present condition with chloride ions. Inserted figures presents reaction free energy change of each step. In aqueous condition without chloride ion (Figure a), the protonation of glucose tends to locate at and the analysis of its geometry (I1) shows a relatively large difference in the distance between C1 and (from Å to 1.9 Å before and after protonation respectively). Meanwhile, the hydroxyl group () is nearly completely formed according to the bond length of 0.983Å. The cationic fragment maintains its stability by developing the hydrogen bond between and 6. While the slight geometrical perturbations is found in the bond length of C1-1, which indicates the C1 site remains sp 3 -hybridized. Whereas, the subsequent ring opening occurs through isomerisation with rotation of group. This configuration change is accompanied by the development of sp character on C1 atom, evidenced from the shortening of the C1-1 bond by 0.09Å (from Å to 1.61Å) and S14

15 approaching of three angles ( θ CC11, θ 1C11, θ CC11) towards the value of 10 o. The C1 atom is located within the C11 plane, further supporting its sp character. Thermodynamic analysis indicates this ring opening step is slightly unfavourable ( G = 3.7kJ/mol). The formed hydrogen bonds ( 3, 3 4, and 6) also contribute to the stability of cationic fragment (I in Figure a). A thermodynamic favorable step (I TS1 I3) then occurs that the hydrogen atom transfers from C to C1 with G = -7.1kJ/mol, which echoes 1,-hydride shift mechanism proposed in our experimental results of glucose conversion using isotope labelling method (Figure 6), moreover, a considerable kinetic isotopic effect is observed that almost a two-fold decrease in the initial reaction rate (k /k D = 1.87, Figure S7) happened due to the deuterium substitution at the C- position, revealing a considerable kinetic isotopic effect, further confirming that the 1,-hydride shift of glucose isomerisation is a rate-determining step. The activation free energy for this elemental reaction is only 6.4 kj/mol, which is also in accordance with 8 kj/mol under the gas phase in the previous theoretical study. 3 The following conformational transition from I3 to I4 is highly preferred due to the sharp drop of G (-6.7kJ/mol), where the group approaches toward C and the distance between and C is shorten to 1.69Å. Finally, the deprotonation of I4 intermediate leads to closure of the furanose ring and generation of fructose (ff), where G is only 18.9 kj/mol revealing tinily unfavorable forward reaction tendency. The ring opening and deprotonation reactions restrict the whole isomerisation of glucose converting to fructose and thus causing a relatively slow reaction rate of glucose decomposition and low fructose selectivity, which agree with corresponding experimental phenomenon mentioned above. Interestingly, chloride ions play a pivotal role in this reaction pathway when - is added to the solvent and the reaction process is described in Scheme S1(a). The average length of hydroxyl bonds of cl-r is elongated by 0.0Å and the hydrogen bonds disappear due to the chelation between chloride ions and glucose, which contributes to accelerating reactivity of reactant. The protonation at of cl-r here with assistance of chloride ions resembles that observed in the absence of -. The Gibbs free energy change, however, decreases to -8.9kJ/mol, which presents much more thermodynamic favorable trend. Similarly, the ring opening step is also greatly promoted with G =9.7kJ/mol and therefore increases the rate of glucose isomerisation. In addition, a slight positive effect ( G changes from -7.1 to -1.7 kj/mol) occurs in the following hydrogen transfer reaction in terms of thermodynamic analysis, which matches very well with the corresponding kinetic study that the activation energy decreases from 6.4 kj/mol to 46.3 kj/mol without and with - respectively. Although the subsequent conformational transition experiences some negative perturbation of S1

16 G, this elemental reaction maintains occurring spontaneously. Most important, the deprotonation prior to forming fructose is accelerated dramatically with G = kj/mol and the hydrogen is released via forming the molecule as studied in previous theoretical work. 4 In the Figure b, the free energy changes along the reaction processes of glucose conversion to fructose are compared together with corresponding configurations in the absence and presence of -. Thermodynamic and kinetic analysis both show the promotion induced by introducing this halogen ion to the reaction system and therefore the MF yield from glucose is enhanced as observed in our experiments. Table S8. Changes of Gibbs free energy of the protonation of glucose and fructose at different sites (kj mol -1 ) Glucose Fructose / -6.4 S16

17 ring opening 4 4 transfer conformational transition cl-r cl-i1 - cl-i cl-i3 cl-i (a) 1 cl-ff (cl-ff) cl-i1 cl-i cl-i3 cl-i4 1 MF cl-i cl-i cl-i cl-i Scheme S. Reaction pathways of glucose to fructose (a) and fructose converts to MF (b) in the presence of chloride ion. (b) The mechanism of MF formation from fructose The reaction of fructose also comes with protonation first under the condition with the Brønsted catalyst in hot water as shown in Figure a. Protonation of the tertiary group is preferred with a free energy change of -1.6 kj/mol (see Table S6 for other protonation reactions). Analysis of geometry shows a large distance between C and (1.61Å) together with generation of a new -, which indicates that a water molecule is almost formed and tends to depart from the carbohydrate (f-i1 in Figure a). Intermediate f-i is then formed through dehydration of f-i1, which is highly preferred because of the large reduction of its free energy. Meanwhile, the development of sp character on the C atom occurs with the water molecule escaping, due to the shortening of C- bond and bond angles relevant to C getting to the value of 10 o. This geometrical perturbations contribute to the stability of cationic configuration with fructofuranose ring (f-i). Whereas, the subsequent deprotonation experiences the slight unfavorable change that hydrogen atom S17

18 escapes from C1 site and C1=C bond formed, where G is 6.7 kj/mol and therefore it is less thermodynamically favorable. Further protonation at the 3 group and the following dehydration are both thermodynamically preferred to produce intermediates f-i4 and f-i, respectively. C1=1 bond is then formed by deprotonation at 1 position to form the intermediate structure (f-i6). Similarly, the protonation at 4, followed by dehydration and deprotonation leads to the production of MF and the thermodynamic analysis also supports these three consecutive reactions. Adding chloride ions in the system of fructose conversion to MF, similarly, brings chelation between chloride ions and hydroxyl groups of fructose in the initial stage (eg.cl-ff in Scheme S (b)). f-i1 in Figure a and cl-i1 in Scheme S(b) present I1 in the absence and presence of -, respectively, Figure c presents the free energy changes along the reaction pathway. Protonation is promoted through the whole pathway with the assistance of -, namely, reactions of cl-ff to cl-i1, cl-i3 to cl-i4 and cl-i6 to cl-i7. In addition, deprotonation is also vastly accelerated in the view of thermodynamic and kinetic analysis. Specifically, the free energy change of reaction I to I3 reduces from 6.7 to -7. kj/mol and the activation energy decreases from 9. to 33.8kJ/mol without and with chloride ions, respectively. ther two deprotonations (cl-i to cl-i6 and cl-i8 to MF) have similar trends of relative energy changes. The reason of these positive influence can be interpreted by strong interaction force between hydrogen atom and chloride ion, which leads to a higher rate of protonation and deprotonation. owever, water molecule elimination from the carbohydrate slows down with a slight increase of the free energy after halogen presenting in the reactions. Based on the aforementioned thermodynamic and kinetic analysis, it can be concluded that adding chloride ions conduces to the protonation and deprotonation to a large extend and therefore promotes the conversion from fructose to MF, which is in excellent agreement with our experiment results. Compared with the process of glucose converting to fructose, it indicates that the completion of reaction degree is larger in MF generation because of lower free energy change, namely, more MF is generated than fructose. But the reaction rate is higher in forming fructose due to lower activation energy in the pathways of fructose formations, presenting shorter reaction time, in the absence of chloride ion. While with the assistance of -, both the completion of reaction degree and reaction rate are higher in the pathway of fructose conversion to MF because of lower Gibbs free energy change and lower activation energy, indicating more MF is formed faster than fructose generation. These analyses are highly consistent with the trends of lines in Figure 3 describing yields of fructose and MF and corresponding reaction time. S18

19 Glucose conversion (%) Glucose-D Unlabeled glucose k /k D = Time/min Figure S7. Profile of glucose isomerization with labeled and unlabeled glucose at 10 C using Na as the catalyst. Reaction condition: 1wt% glucose, 30wt% Na, 0. M N, 10 ml. References (1) Shuai, L.; Amiri, M. T.; Questell-Santiago, Y. M.; éroguel, F.; Li, Y. D.; Kim,.; Meilan, R.; Chapple, C.; Ralph, J.; Luterbacher. J. S. Formaldehyde stabilization facilitates lignin monomer production during biomass depolymerization. Science 016, 34, (DI: /science.aaf7810) () Li, C. Z.; Zheng, M. Y.; Wang, A. Q.; Zhang, T. ne-pot catalytic hydrocracking of raw woody biomass into chemicals over supported carbide catalysts: simultaneous conversion of cellulose, hemicellulose and lignin. Energy Environ. Sci. 01,, (DI: /C1EE0684D) (3) Yang, G.; Pidko, E. A.; ensen, E. J. M. Mechanism of Brønsted acid-catalyzed conversion of carbohydrates. J. Catal. 01, 9, (DI: /j.jcat ) (4) Pidko, E. A.; Degirmenci, V.; ensen, E. J. M. n the mechanism of Lewis acid catalyzed glucose transformations in ionic liquids. ChemCatChem. 01, 4, (DI: /cctc ) S19