Data on making uniform lignin building blocks via in-situ real-time monitoring of hydroxyethyl modification

In this work, a lab-designed apparatus was developed to collect and record the CO2 amount during the hydroxyethyl modification of lignin. We presented the CO2 volume amount and the production rate under different reaction conditions (80 – 120 °C and 2 – 6 hrs). Nuclear magnetic resonance spectroscopy was performed to analyze the chemical structure of the hydroxyethyl lignin corresponding with different amounts of CO2 that evolved during the reaction. The aliphatic hydroxyl, aromatic hydroxyl, and carboxylic acid groups were analyzed and tabulated. The acetylated hydroxyethyl lignin samples were characterized by 13C NMR to obtain the aliphatic hydroxyl (primary and secondary), phenol (ortho substituted and ortho-free), hydroxyethyl, methoxy, and aromatic hydrogen groups semi-quantitatively. Fourier-transform infrared (FTIR) spectroscopy was adopted to analyze the surface functional groups including alkyl aryl ether bond, carboxylic acid groups, and aromatic hydroxyl groups. Gel permeation chromatography combined with a multi-angle light scattering detector and differential refractive index detector were used to obtain the molar mass of lignin before and after the modification.

Process Chemistry and Technology Specific subject area This data set covers a greener chemical modification procedure to obtain more uniform aromatic polymer resources using in-situ real-time monitoring of the reaction Type of data -The hydroxyethyl reactions were performed in a 50 mL round bottom flask by mixing 2.5 g dried lignin powders with 8 g ethylene carbonate and 0.4 g sodium carbonate (Na 2 CO 3 ). -A water displacement method was used to measure the volume of CO 2 during the hydroxyethyl reaction [1] . The equipment was displayed in Fig. 1 . The volume of CO 2 during the hydroxyethyl reaction was recorded every 10 -15 min. -The hydroxyethyl reaction was then quenched by adding 200 mL cold water, stirred overnight, washed and filtered by another 3 × 200 mL distilled water, dried by lypholization, and kept in the vacuum oven (50 °C) before characterization.
-13 C NMR sample preparation: approximately 150 mg of lignin or acetylated lignin was dissolved into 450 μl DMSO-d6 , followed by the addition of 60 μl of a solution of chromium(III) acetylacetonate (50 mg/mL) in DMSO-d6 as relaxation reagent and 15 mg of trioxane as internal standard [4 , 5] . -These lignin solutions were thoroughly mixed until no solid was left in the solution and transferred into a 5 mm NMR tube for immediate analysis. -The obtained spectra were processed using the Topspin 3.6.1 software including Fourier transform, phase correction, baseline change, and calibration.
Gel permeation chromatography: -Agilent 1100 HPLC system including a guard column (PL PolarGel L) and two GPC column (PolarGel L and M, Agilent). -The fractionated samples were then analyzed using a multi-angle light scattering detector (MALS, Wyatt Corp. US) and optilab T-rEX differential refractive index detector (dRI, Wyatt Corp. US). -The obtained molecular mass traces were collected and analyzed using Astra 6.1 software including conventional calibration analysis, Zimm plots, and dn/dc analysis.

Data format Raw and Analyzed
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Parameters for data collection
In-situ Real-time monitoring: -The reaction temperature of oil bath was set from 80 -120 °C with time length from 0 -6 hrs. -The CO 2 amounts were collected and measured under atmospheric pressure (Vancouver, 102.3 -101.3 kPa) and room temperature (20 -25 °C).
-31 P NMR: an inverse-gated decoupling pulse sequence was employed with parameters: relaxation delay 5 s, acquisition time1.4 s, pulse length 6 μs, 90 °p ulse width, and number scan 800. The chemical shift of each phosphitylation product was calibrated with a product of TMDP with water (132.2 ppm) [6] .

Value of the Data
• This work provided a simple in-situ real-time monitoring method to obtain more uniform hydroxyethyl lignin. • Researchers working on the modification of technical lignin resources will benefit from these data to reduce the workload on the optimization of reaction conditions, and enhance the reproducibility of modification, the quality of hydroxyethyl lignin, and overall economic efficiency. • The lab-based CO 2 measuring equipment and NMR analysis protocol can be adopted by other researchers working on the characterization and modification of lignin resources. • The obtained hydroxyethyl lignin resources as building blocks with higher uniformity can be used to prepare materials, including but not limited to, polyurethane foams, polyesters, and coating materials.

Data Description
In this study, Fig. 1 showed lab-designed equipment for collecting and measuring the CO 2 amount during the hydroxyethyl modification of lignin. The in-situ real-time monitoring data, including the CO 2 amount and CO 2 production rate, were tabulated in Table 1 . With different amounts of CO 2 , the modified lignin was analyzed by 31 P and 13 C NMR quantitatively based on the previous methods, while the original data was uploaded to the Mendeley Data [4 , 5 , 7 , 8] . Fig. 2 showed the 13 C NMR spectra of modified lignin. The analyzed results were displayed in Tables 2 and 3 . FT -IR spectra ( Fig. 3 ) showed the chemical functional groups of lignin. The molar mass of unmodified and modified lignin samples were analyzed by the ASTRA software and tabulated in Table 4 [7] . The molecular weight traces were based on the MALS detector in our related research article [8] .  13 C NMR, the spectra were acquired using Bruker Avance NMR (300 MHz) at 25 °C equipped with a BBO probe. HSQC NMR spectra were acquired using Bruker Avance Bruker AVANCE III (600 MHz) at 25 °C equipped with a cryoprobe. The sample preparation and acquisition parameters has been explained in the specification table. Data analyzed methods: Topspin 3.6.1 software was used to process the obtained spectrum: Fourier transformation, baseline correction, and calibration. A semi-quantitative analysis of the 31 P, 13 C, 1 H, and HSQC spectrum was performed based on previous works [12 , 13] .

Gel permeation chromotography combined with MALS and dRI
PSS standard samples with molar masses of 1.1 kDa, 2.0 kDa, 4.29 kDa, 10 kDa, 29.5 kDa, 63.9 kDa, 145 kDa, and 470 kDa were prepared by dissolving 10 mg PSS in 1 mL DMSO at 50 °C for 48 hrs until they were thoroughly dissolved in the solvent. Gel permeation chromatography (GPC) measurements were carried out using Agilent 1100 GPC equipment (USA) consisting of a pump, an autosampler, and a column oven set at 35 °C. 20 μL lignin solution was injected into the system and separated. Two types of PolarGel column (PolarGel M and L, Agilent) were used to fractionate the lignin at 35 °C using DMSO/LiBr (0.5% w/v) as eluent at 0.5 mL/min. The fractionated lignin was then analyzed by multi-angle laser light scattering (MALLS, Wyatt Tech. CA, USA), and the optilab T-rEX differential refractive index detector (dRI, Wyatt Tech. CA, USA). The data were collected and analyzed by ASTRA 6.0 software. The dn/dc value was calculated through the dRI traces by an on-line method using ASTRA software [14] .  Table 3 Semi-quantitative 13 C NMR analysis of acetylated hydroxyethyl lignin during the modification (100Ar), the carbon signal from the aromatic region (155-100 ppm) was used as an internal standard.
No.  1. Lab-designed equipment for collecting and measuring CO 2 . The simple and accurate water displacement method was developed in the 18th-century [9] and is still widely used to record the generated gas, such as oxygen and hydrogen, during chemical reactions [10 , 11] . Carbon dioxide has a solubility of 1.45 g/L in aqueous water, so an excessive amount of CO 2 was dissolved into the water to ensure the saturated conditions. All the connecting ports were carefully sealed to minimize the potential leaking. The reactor was pre-purged with a nitrogen atmosphere to dry the sample and prevent the backflow of water vapor causing the degradation of ethylene carbonate. The pressure of collected gas in the cylinder was equal to the atmospheric pressure (Vancouver, BC). The water partial vapor pressure is 3169.9 Pa with approximately 3% changes on the pressure of collected gas. It is worth to mention that the impacts from the buoyancy pressure of the water in the cylinder, and the slow leakage of CO 2 gas for extended time periods ( > 6 hrs) may slightly impact the gas pressure in the cylinder as well. Here, we did not consider about these small changes to the volume.  13 C NMR spectra of hydroxyethyl lignin with a different amount of evolved CO 2 ; (a) unmodified SKL; (b) CO 2 = 10 mL/g; (c) CO 2 = 32 mL/g; (d) CO 2 = 54 mL/g; (e) CO 2 = 86 mL/g; the carbon signal from the aromatic region (155-100 ppm) can be used as an internal standard. The relative concentration of functional groups is presented per 100 aromatic units. This was achieved by integrating the aromatic regions (100-155 pm) and setting this to a value 600 (100 aromatic ring), then all chemical groups would be expressed based on this value. Fig. 3. FT-IR spectra of hydroxyethyl lignin based on different amounts of evolved CO 2 ; (a) unmodified SKL; (b) CO 2 = 10 mL/g; (c) CO 2 = 32 mL/g; (d) CO 2 = 54 mL/g; (e) CO 2 = 60 mL/g; (F) CO 2 = 78 mL/g; (g) CO 2 = 86 mL/g; (e) CO 2 = 97 mL/g. alkyl aryl ether (P1, 1030cm −1 and P3, 1256 cm −1 ), primary alcohol (P2 1140 cm −1 ), phenol (p4, 1367 cm −1 ), and CH in plane (P5, 1418 cm −1 ).

Declaration of Competing Interest
The authors declare that they have no known competing financial interests influenced the work reported in this article.