Controlling cellulose feedstock size allows for modification of cellulose-based carbon-based solid acid size

Carbon-based solid acids (CSA) have grown in popularity in recent years owing to their strong catalytic activity, thermal stability, and reusability. The size effect has a significant influence on the catalytic activity of carbon-based solid acids in heterogeneous catalysts. The impacts of raw material size on the shape, sulfonation degree, and catalytic activity of produced carbon-based solid acids were examined in this article. Various sizes of microcrystalline cellulose (MCC), cellulose nanocrystals (CNCs), and cotton fiber pulp (CP) were used as carbon sources in a simple carbon-sulphonation method to synthesize carbon-based solid acids. The produced CSA has a high concentration of sulphonic acid groups, as well as hydroxyl and carboxyl groups, and exhibits remarkable catalytic activity for the conversion of xylan to xylose. The solid acids generated from MCC have the most homogeneous shape, the greatest degree of sulphonation, and the highest catalytic activity. The conversion rate of xylan hydrolysis to xylose was up to 58.8% under ideal reaction conditions (150 °C, 4 h), and the catalyst retained almost its initial level of activity after five cycles with no appreciable deactivation.


Introduction
Acidic catalysts are classified as homogeneous acid catalysts and heterogeneous solid acid catalysts. Both types of catalysts are used extensively in the manufacture of industrial chemicals (Busca 2010;Fu et al. 2012;Kozhevniko 2009;Okuhara et al. 2001). Homogeneous catalysts having the drawback of creating a considerable volume of waste liquid during the catalytic process, corroding the equipment severely, and being difficult to separate from the source materials and products. Due to their environmental friendliness, efficiency, stability, and reusability, solid acid catalysts are frequently utilized. Unfortunately, solid catalysts such as oxide solid acid and zeolite have an acid hydroxyl group as their acid site. Due to the hydrogenation of -OH, the acidity of these catalysts is significantly decreased in the presence of water, and the acidic groups may be ejected at elevated temperatures, restricting their utilization on a broad scale (Clark 2002;Margolese et al. 2000;Nakajima et al. 2010;Olah et al. 1986;Wilson et al. 2002). In comparison, carbon-based solid acids have a diverse carbon supply and are regarded appropriate catalysts for a broad variety of reactions due to their chemical inertness, high catalytic stability, catalytic characteristics, and high thermal conductivity as well as thermal stability (Cao et al 2015;Emeis 1993;Geng et al. 2011;Li et al. 2015; Thoi et al. 2015). Researchers have recently discovered that the structural morphology of carbon-based solid acid catalysts varies significantly, ranging from mesoporous to microporous carbon, and that these structural dimensions might have a direct effect on catalytic efficiency (Chen et al. 2009;John et al. 2006;Ogaki et al. 2009;Toda et al. 2005).
To improve traditional carbon-based solid acids, the synthesis of carbon-based solid acid catalysts utilizing biomass as raw material has garnered considerable interest (Huang and Yao 2013;Okuhara 2002;Rinaldi and Schüth 2010). Carbon solid acids derived from biomass exhibit not only their own characteristics, but also those of the biomass. Due to the inherent uniqueness of each biomass in nature, the internal structure of the carbon material created from each biomass as a carbon source is similarly unique. Cellulose is a linear homopolymer comprised of D-glucopyranose subunits connected by 1,4-glycosidic linkages. It is common in nature and is the most abundant organic molecule on the planet (Caes et al. 2015). Due to its high carbon content (44.44%), renewable nature, cheap cost, and environmental friendliness, cellulose is a suitable carbon precursor. There are also various derivatives of cellulose, including carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC) and so on. (Khan et al. 2017;Chen et al. 2015). These cellulose derivatives can be modified to enhance their catalytic properties. The high number of active hydroxyl groups in cellulose, which are also rapidly replaced by -SO 3 H during the sulfonation process, provides CSA with a larger active site, hence increasing catalysis efficiency (Konwar et al. 2019). Additionally, the hydroxyl groups function as an adsorbent on the reaction substrate, increasing the surface area of interaction between the CSA and the substrate. Recent study has shown that carbon-based solid acids produced from cellulose exhibit a variety of internal structures, including nanoscale porous structures, mesoporous structures, and spherical internal structures They vary in terms of sulfonation degree and catalytic efficiency, and as a result, the size of the cellulose feedstock has an effect on the following carbonation and sulfonation modification processes, as well as catalytic performance.
The purpose of this work is to compare three different size cellulose (MCC, CNCs, and CP) synthesized as carbon-based solid acid catalysts by a two-step carbonation-sulfonation procedure. The hydrolysis of xylan was used to show the catalytic effectiveness of a biomass carbon-based solid acid catalyst. In comparison to conventional catalysts, the catalyst described in this study is constructed of small carbon spheres that increase the catalyst's active specific surface area and introduce groups such as -SO 3 H, -COOH, and -OH. Simultaneously, because of the synergistic action of its functional groups, xylan chains may be attacked more effectively, resulting in a greater catalytic hydrolysis effect (Suganuma et al. 2010;Hara 2010;Kiichi et al. 2011;Masaaki et al. 2009;Tang et al. 2011).

Materials
Microcrystalline cellulose (column chromatography) was a commercial product from Sinopharm Chemical Reagent Co. Ltd. Sulfuric acid hydrolysised cellulose nanocrystal were purchased from Tianjin Economic and Technological Development Area (TEDA), Tianjin, China. Cotton fiber were purchased from Tianjin Chemical Reagent Company. Sulfuric acid (AR, 95-98%) and sodium hydroxide (AR, > 96%) were from Tianjin Kemiou Chemical Reagent Co., Ltd. Sodium chloride was purchased from Tianjin Guangfu Technology Development Co., Ltd. Xylan (> 98%) were purchased from Sigma Aldridge. Xylose were from Shanghai Maclin Biochemical Technology Co., Ltd.
Preparation of CSA-MCC, CSA-CNCs and CSA-CP To conduct a systematic examination of the performance differences between these three solid acid catalysts, other test conditions, such as the ratio of raw materials to water, the carbonization temperature and time, the amount of sulfuric acid added during the sulfonation process, the sulfonation temperature and time, and so on, are kept constant.
The schematic illustration of the process for the formation of the CSA-MCC, CSA-CNCs and CSA-CP is shown in Fig. 1. 0.5 g of microcrystalline cellulose, and 50 mL of water were weighed. After that, a 30-min ultrasonic treatment with an Ultrasonic cell grinder was used to completely disperse the raw ingredients in water. To produce the cellulose-derived carbon base, a magnetic heating stirrer was utilized to heat and stir at 230 °C, 500 rpm for 10 h. It was taken from the reactor and filtered before being dried in a 60 °C oven. 0.15 g of each carbonized powder was weighed, and 5 mL sulfuric acid (AR, 98% (W/W %)) was added. The mixture was then heated and agitated for 8 h at 150 °C and 500 rpm. The -SO3H group was introduced during this procedure. After heating and stirring, strain and dry in a 60 °C oven. The solid acid catalysts synthesized in this manner were designated as CSA-MCC, CSA-CNCs and CSA-CP are prepared in the same way as the above steps.

Characterization of catalysts
The crystallinity of the catalyst was investigated by X-ray diffraction (XRD) with an XRD7000S (Shimadzu Corp; Kyoto, Japan) using a copper (Cu) Kα ra-diation source in the 10°-60°/2θ range with a scanning step length of 5 °C/min. The graphitization degree and crystallographic structure of the catalysts were characterized by Microscopes Raman Spectrometer (Renishaw Co., UK). The morphologies of the catalysts were imaged by a JSM-7800 F scanning electron microscope (SEM) (JEOL Ltd.; Tokyo, Japan) and a transmission electron microscopy (TEM) (JEM-2100, JEOL, Japan). The specific surface area, pore size, and pore volume of catalyst were calculated by the Brunauer-Emmett-Teller (BET) method as well as the Barrett-Joyner-Halenda (BJH) theory. The functional groups of the catalysts and raw materials were characterized by Fourier transform infrared (FTIR) spectroscopy in the wavenumber range of 500-4000 cm −1 . The number of functional groups within the catalyst and raw materials were characterized via elemental analysis (Vario EL cube, Elementar, Frankfurt, Germany). The elemental composition of the catalyst was characterized by X-ray photoelectron spectroscopy.

Determination of sulfonic acid group density
Using the ion exchange method, 0.05 g catalyst was weighed in a 100 mL beaker, and 20 mL NaCl solution with a concentration of 1 mol/L was added to the catalyst for ultrasonic shock for 30 min to ensure that all H + on the sulfonic group on the catalyst was exchanged by Na + . Then take out and filter, take out 10 mL filtrate and add 3-4 drops of phenolphthalein indicator, and fix it with 0.01 mol/L NaOH standard drops to the end point (the solution changes from colorless to light red, and still does not change color after 30 s of shaking), and record the volume of consumed NaOH standard solution (Lin et al. 2018).
The density of sulfonic acid group is calculated by the following formula:

Determination of carboxyl density
Using reverse titration method, 0.05 g catalyst was accurately weighed in a 100 mL small beaker, and 30 mL of 0.01 mol/L NaHCO3 solution was added to it for ultrasonic shock for 30 min, so that the carboxyl and sulfonic groups on the catalyst could fully react with NaHCO3, and then 10 mL filtrate was taken from it. Add 4-5 drops of bromocresol green-methyl red mixed indicator, and then drop with 0.01 mol/L HCl standard liquid until the filtrate changes from green to dark red, boil for 2 min, cool to room temperature, and continue titration with 0.01 mol/L HCl standard solution until the solution changes from green to dark red again, which is the end point of titration. Record the total volume of HCl standard liquid consumed.
The total density of carboxyl and sulfonic groups can be calculated as follows: The carboxyl density is calculated as follows: Determination of hydroxyl density Using reverse titration method, 0.05 g catalyst was weighed in a 100 mL beaker and 10 mL 0.01 mol/L (1) NaOH solution was added to the catalyst for ultrasonic shock for 30 min to ensure that the sulfonic group, carboxyl group and hydroxyl group on the catalyst could fully react with NaOH. Then, 10 mL filtrate was removed from the catalyst after filtration. Add 3 to 4 drops of phenolphthalein indicator, and drop with 0.01 mol/L HCl standard liquid until the filtrate changes from pink to colorless, that is, the end point of titration, and record the volume of HCl standard liquid consumed.
The total density of sulfonic group, carboxyl group and phenolic hydroxyl group can be calculated as follows: The calculation formula of phenolic hydroxyl density is as follows:

Conversion of xylan to xylose
The prepared CSA-MCC 0.1 g and xylan 0.1 g were combined with 4 mL water and heated and stirred at 120 °C for 4 h in a teflon pot in a reaction kettle. The solution was filtered after the reactor was cooled to room temperature to get CSA-MCC solid powder and hydrolysis solution. The filtered CSA-MCC solid powder was dried in an oven at 60 °C for 12 h. To get the matching solid powder and hydrolytic solution, the preceding operations were performed using various synthesized catalysts (CSA-CNC and CSA-CP). The mechanism of hydrolysis of xylan into xylose is shown in Fig. 2. (4) The contents of xylose in supernatant from xylan solution were determined by HPLC (Waters 2489, USA; HPLC Organic Acid Analysis Column Aminex HPX-87H lon Exclusion Column 300 × 7.8 mm, mobile phase of 5 mM H 2 SO 4 , at a flow rate of 0.5 mL min −1 , column temperature at 50 °C). The sugar oligomers weremeasured according to the method in the literature. The components of xylose were analyzed by the NREL standard analytical method (Jae et al. 2010).
The yields of sugars (xylose) were defined as where N is the mole number of xylose in the hydrolysate and M is the number of moles of the original xylose solution.

Recovery performance of catalyst
After catalysis, the catalyst was removed from the solution and washed with deionized water before being dried in an oven set to 65 °C. Rep the preceding procedures three times more, noting the amount of xylose in the xylan solution after each cycle.

Results and discussion
Morphology characteristics of CSA-MCC, CSA-CNCs and CSA-CP To investigate the effect of different sizes of biomass-cellulose raw materials on the morphology and structure of a carbon-based solid acid catalyst, three different sizes of raw materials were used to prepare the catalyst (microcrystalline cellulose, cellulose nanocrystals, and cotton pulp), and the catalyst  of several nanometers and a length of tens of nanometers. CNCs fiber rods are narrower and longer than MCC and cotton pulp. Following carbonization and sulfonation, the shape and structure underwent dramatic changes in the presence of extreme heat and intense sulfuric acid. MCC and CNCs, for example, transformed the rod-like cellulose structure into spherical particles with a particle size of around 1 micron. Due to the random distribution of raw cotton pulp, the fibers were joined into blocks after carbonization and sulfonation, with some irregular particles on the surface. Both CSA-MCC and CSA-CNCs contained pellets of 1 micron in diameter, which improved the catalyst's active sites, however the pellets of CSA-CNCs were agglomerated. In comparison to the lamellar structure, the spherical form provides the catalyst with more contact sites with the xylan chain. This spherical form enhances adsorption between the catalyst and xylan, potentially increasing the yield of xylose produced during xylan hydrolysis. The EDS pattern of CSA-MCC demonstrates that the C, O, and S elements are scattered uniformly; this suggests that -SO 3 H is distributed evenly in CSA-MCC, which enhances the catalytic action.
Acid site density and yield of CSA The production and acid loading of carbon-based solid acids from three distinct raw materials (cotton pulp, CNCs, and MCC) after carbonization and sulfonation are shown in Table 1. As can be observed, the yields of the three carbon-based solid acids vary between 27 and 31%, indicating that size has no influence on the yield of CSA. The densities of -OH group and -SO 3 H group of CSA-MCC are 2.64 and 1.10, respectively, while those of CSA-CP are 3.03 and 0.53, respectively. this is because the size of CP is too large, resulting in less active sites exposed during carbonation and sulfonation, which is not conducive to the substitution of -SO 3 H group, while the particle size of CSA-MCC is moderate, which is conducive to the sulfonation reaction Therefore, the density of -OH groups of CSA-MCC is lower than that of CSA-CP, and a large number of its -OH groups are smoothly substituted by -SO 3 H groups. While CNCs are cellulose nanocrystals, the particle size is nanoscale as can also be seen from TEM. Due to the tiny size, CNCs will be agglomerated during the carbonization process, which makes the shape of the sample mostly agglomerated spherical. During the sulfonation process, the density of -SO 3 H group of CSA-CNCs is lower than that of CSA-MCC because the agglomeration phenomenon affects the substitution of -SO 3 H group on the sample. The acid densities of CSA-CP, CSA-CNCs, and CSA-MCC are respectively 3.91, 4.27, and 4.02. The overall acid density of CSA-CNCs was the greatest, whereas CSA-MCC had the highest -SO 3 H concentration, with -SO 3 H being the essential group for xylan conversion.

Structural characteristics and thermal analysis of catalysts
The thermostability of CSA-CP, CSA-CNCs and CSA-MCC were evaluated by TG as demonstrated in Fig. 4a. Primarily, CSA-CP and CSA-CNCs had similar thermal stability, CSA-MCC has the best thermal stability. As exhibited in that in the temperature range of 25-100 °C, the weight loss of the catalyst is about 12-18%, mainly due to the volatilization of absorbed water and volatile components. The thermal weight loss curve of three kinds of catalysts is relatively smooth between 110 and 200 °C, which indicates that the carbon-based solid acid catalyst can withstand a high temperature of 200 °C and has good thermal stability. When the temperature is higher than 200-260 °C, the weight of the catalysts has a sharp loss attributed to the decomposition of -SO 3 H groups. A continuous weight loss can be observed over 260 °C, which is probably caused by further condensation of amorphous carbon. And it can be observed that after 350 °C, the raw material weight loses rapidly, while the catalyst weight loses slowly. In summary, the catalysts  have good thermal stability in reaction temperature Liu et al. 2013;Yu et al. 2018). As seen in the infrared spectrum (Fig. 4b), there is a strong absorption peak at 3447 cm −1 , matching the hydroxyl -OH stretching vibration absorption peak. The peak at 2893 cm −1 corresponds to the absorption peak for stretching vibrations of -CH 2 . There is a faint absorption peak about 1641 cm −1 that corresponds to the stretching vibration absorption of the C=C double bond, and there is C-H bending vibration absorption near 1376 cm −1 . The absorption peak around 894 cm −1 corresponds to the stretching vibration of the glycosidic bond -OH, which is the distinctive peak of the -glycosidic bond formed by the dehydration of glucose units in cellulose (Tang et al. 2011).
According to Fig. 4c, the absorbance maxima of 3420 cm −1 and 1730 cm −1 correspond to O-H and C=O stretching vibrations in the -OH and -COOH groups, respectively (Shu et al. 2010;Zhao et al. 2017). The peaks at 1600 cm −1 are attributable to the C=C stretching vibration of aromatic carbon, indicating that the catalysts above form a stable conjugated aromatic structure (Hu et al. 2016). Two peaks at 1038 cm −1 and 1180 cm −1 correspond to the symmetric and asymmetric stretching vibrations of S=O and O=S=O, respectively, while the absorption peak at 650 cm −1 corresponds to the C-S tensile vibration. When compared to Fig. 4b, it is clear that the raw materials lack C-S, S=O, and other chemical linkages, showing that the -SO 3 H group was effectively loaded onto the catalyst surface (Qi et al. 2018;Li et al. 2012). These oxygen-containing groups are regarded to constitute the hydrolysis active site.
The percentage of each element in the three raw materials and three catalysts is shown in Table 2. Clearly, the element S concentration of the three raw materials prior to carbonization and sulfonation treatment is very low, all less than 0.3%. After preparing the solid acid catalyst, the S element concentration grew dramatically, and both CSA-MCC and CSA-CNCs surpassed 6%. S element concentration was greater in CSA-MCC, reaching 6.188% than in CSA-CP, at 3.924%. This is compatible with FT-IR and sulfonic titration results, which indicate that the -SO 3 H group was effectively introduced into the catalyst during the sulfonation procedure, with the maximum concentration of the -SO 3 H group in CSA-MCC. The prepared CSA showed a decrease in both H and O elements compared to the untreated feedstock as a result of the dehydration and carbonation reactions.
N 2 sorption measurements were performed to investigate the textural properties of CSA-MCC, CSA-CNCs and CSA-CP, the results were shown in Table 3. The specific surface area of CSA-MCC was 23.87m 2 g −1 , that of CSA-CNCs was 17.57m 2 g −1 , while CSA-CP had the smallest specific surface area at just 3.17m 2 g −1 . This corresponds to the SEM pictures are described. Due to the aggregation of small carbon spheres in CSA-CNC, the specific surface area of CSA-CNCs is less than that of CSA-MCC, but the structure of CSA-CP is entirely massive and contains few tiny carbon spheres, resulting in the lowest specific surface area. The catalytic efficiency of CSA-MCC with a large specific surface area is superior because it increases the accessibility of reactants to substrates and exposes more tiny carbon spheres, allowing -SO 3 H to approach the xylan chain more frequently, increasing the active site and facilitating catalytic hydrolysis of xylan. Because the catalyst's reactive site is -SO 3 H and its internal structure is made up of tiny carbon spheres, the pore volume of all three catalysts is less than one, yet this has no effect on the catalytic efficiency.
As seen in Fig. 4d, the characteristic diffraction peaks of cellulose emerge between 2 = 16° (101) and 22.5° (200), indicating a type I structure (Wada et al. 2004). Catalysts displayed a single strong diffraction peak (200) at 2 = 26° and a weak peak (110) at 2 = 38°, which are characteristic of amorphous carbonaceous materials composed of an uneven arrangement of aromatic carbon sheets (Konwar et al. 2014). As seen in Fig. 4e, the Raman spectrum of CSA contains two well-characterized bands at 1380 cm −1 (D-band) and 1590 cm −1 (G-band), which correspond to disordered carbon/defects and graphitic carbon, respectively (Su et al. 2011). Due to the increase in ordered structure caused by more H 2 SO 4 entering the pores to promote the activation process at low temperature, the degree of graphitization or defectiveness in carbon materials is proportional to the intensity ratio of the D band to the G band, with I D /I G values of 0.43, 0.50, and 0.58 for CSA-CP, CSA-CNCs, and CSA-MCC, respectively. The I D /I G ratio of CSA-MCC is much greater than that of CSA-CNCs and CSA-CP, suggesting that the structure of CSA-MCC is significantly more faulty and has a lower graphitized degree.
The XPS spectra of CSA-MCC in Fig. 4f-i was utilized to characterize the catalysts' surface chemical properties. The XPS peaks of C 1s may be deconvoluted into two dominant components, C-C and C=C at 284.4 eV, as well as two weaker bands associated with C=O (as found in carboxyl groups) at 288.8 eV and C-O (as seen in hydroxyl groups) at 286.4 eV. The peaks at 531.5 eV and 533.4 eV in the high-resolution O1s spectrum of CSA-MCC are ascribed to oxygen atoms in C=O and C-O, respectively (Zhao et al. 2017). For CSA-MCC, a new O1s peak with center energy of 532.7 eV arises, which may be ascribed to oxygen atoms in -SO 3 H groups (Zhao et al. 2017). The S2p spectra of CSA-MCC at high resolution may be deconvoluted into peaks at 168.4 eV, which correspond to S2p in -SO 3 H groups. XPS tests reveal no additional sulfur-containing configurations.
Hydrolysis efficiency and reusability of CSA Figure 5a illustrates the yield of xylose after catalytic hydrolysis of xylan by the catalyst. As can be observed, the catalytic activity of three catalysts (CSA-CP, CSA-CNCs, and CSA-MCC) are very distinct. Under the same experimental circumstances, the blank group represents the xylose yield of xylan in the absence of a catalyst. Apparently, the catalytic abilities of the three catalysts were significantly different. In comparison to CSA-CP (20.3%) and CSA-CNCs (36.1%), CSA-CNCs demonstrate superior catalytic activity (58.8%). In general, CSA-MCC demonstrates outstanding catalytic performance in xylan hydrolysis, which may be ascribed to its high -SO 3 H group density and globular shape, which increase active site accessibility and ensure the maximum catalytic performance of catalysts.
The catalyst with the best hydrolysis rate in this paper, CSA-MCC, was compared with other catalysts in the literature as shown in Table 4. It can be seen that the catalytic hydrolysis performance of CSA-MCC is higher than Fe 3 O 4 /C-SO 3 H ). Compared to HZSM-5 , it is the absence of groups such as -COOH, -SO 3 H leading to low hydrolysis rate. Amberlyst-15 ) has a slightly higher performance than CSA-MCC, but it has a reaction time of 24 h, while CSA-MCC only needs 4 h to complete the hydrolysis reaction. Taxy11 (Zheng et al. 2020) is a kind of novel    60.2 HZSM-5  11.4 Taxy11 (Zheng et al. 2020) 50.4 CSA-MCC (this work) 58.8 endogenous xylanase that improves the hydrolysis rate of CSA-MCC is higher than it. Due to the high catalytic efficiency of CSA-MCC, the cycle life of CSA-MCC is examined. The reusability of the CSA-MCC catalyst was shown in Fig. 5b during the hydrolysis of xylan. The CSA-MCC used in this cycle may be recycled from the mixture by filtering and then reused under the same reaction conditions in the next cycle after cleaning and drying. As seen in Fig. 5b, the recovered CSA-MCC remained generally steady during a fivecycle period, despite the fact that the reducing sugar yield decreased progressively from 58.8% (Run 1) to 51.3% (Run 5). To ascertain the stability of the -SO 3 H on the catalyst, the density of -SO 3 H on the catalyst was determined after each cycle. It was discovered that the density of -SO 3 H on the catalyst after the fourth recycle run (mmol g −1 ) decreased significantly when compared to the fresh catalyst (mmol g −1 ), which was the primary reason for the decrease in catalyst activity. The density of the -SO 3 H group on the catalyst decreased from 1.10 to 1.05, 1.01, 0.96, 0.94 (mmol/g) in order after four cycles. By and large, the catalyst retained a high catalytic activity.

Conclusion
In summary, an ecologically acceptable and reusable cellulose-based solid acid catalyst was produced for the hydrolysis of xylan to produce platform chemicals, and the influence of feedstock size on the carbonation-sulfonation process and catalytic performance was examined. After a simple carbonization-sulfonation procedure, the density of -SO 3 H groups and total acid on the surface of CSA-MCC was 1.1 mmol g −1 and 4.02 mmol g −1 , respectively. Due to the nanometer-scale size of CNCs, agglomeration is likely to occur during the carbonation-sulfonation process, reducing the catalyst's catalytic activity. However, because the size of CP is in the tens of microns range and the arrangement is disordered and uneven, it is difficult to form microspheres during the carbonization process, and the introduction of the sulfonic group has a limited effect on the catalytic activity, the CSA-MCC catalytic performance prepared by MCC is optimal. The decreasing sugar yield of xylan hydrolysis was 58.5% under ideal circumstances.
Additionally, the CSA-MCC demonstrated excellent reusability. We provide a viable and environmentally friendly approach for catalytically converting xylan into platform chemicals that were intended to replace dilute acid in acid hydrolysis.

Declarations
Competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.