Raney Copper Catalyst for Selective Polyol Synthesis
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Solution Overview
Problem
Current methods for converting cellulose to alkyl glycosides, sugar alcohols, and reduced polyols like 1,2,5,6-hexanetetrol are inefficient and costly, often requiring harsh conditions and low yields, with limited economic viability for industrial scale production.
Innovation Solution
The methods involve heating acetyl cellulose pulp with an alcohol and an acid catalyst like phosphonic acid or sulfonic acid to form R-glycosides, followed by hydrogenation with catalysts containing copper and ruthenium to produce sugar alcohols, and using Raney copper catalysts to convert these into 1,2,5,6-hexanetetrol, while acid catalysis converts hexanetriols into tetrahydrofuran derivatives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If concentrated sulfuric acid is used for hydrolysis of cellulose to glucose, then good yields of glucose are achieved, but HMF and tarry humins are formed which negatively impact yield and require additional separation steps
Solution Approach 1:
The patent extracts and removes the harmful concentrated sulfuric acid from the hydrolysis process, replacing it with dilute acid or enzymatic catalysts. This extraction of the harmful element eliminates the formation of HMF and humins while maintaining glucose production capability through alternative catalytic pathways.
Solution Approach 2:
The patent changes the concentration parameter of the acid catalyst from concentrated to dilute, fundamentally altering the reaction conditions. This parameter change prevents the degradation of glucose to HMF and humins while still achieving effective hydrolysis of cellulose to glucose through optimized dilute acid or enzymatic conditions.
2Object-affected harmful factors
If enzymatic hydrolysis is used to convert cellulose to glucose, then mild conditions are achieved, but reaction rates are low and expenses are high making it impractical for industrial scale
Solution Approach 1:
The patent merges the advantages of enzymatic hydrolysis (mild conditions, high selectivity) with the productivity of chemical catalysis. By combining enzyme pretreatment to activate cellulose followed by dilute acid hydrolysis, or using engineered enzymes with improved stability and activity, the process achieves both mild conditions and industrial-scale productivity.
Solution Approach 2:
The patent applies preliminary enzymatic activation or pretreatment to the cellulose structure before main hydrolysis. This preliminary action opens up the crystalline structure of cellulose, making it more accessible to catalysts and significantly improving subsequent hydrolysis rates while maintaining mild conditions throughout the process.
3Reliability
If traditional Fischer glycosidation is used to prepare R-glycosides from glucose, then glycoside bonds are formed, but strong acids, elevated temperatures and pressures are required
Solution Approach 1:
The patent introduces alternative catalysts as intermediaries to mediate the glycosidation reaction. Instead of using strong mineral acids, the patent employs organic acid catalysts, ionic liquids, or enzymatic catalysts that provide the necessary catalytic activity under milder conditions, enabling glycoside bond formation at lower temperatures and pressures.
Solution Approach 2:
The patent changes the physical parameters of the reaction conditions by using alternative catalytic systems. These catalysts enable the reaction to proceed at lower temperatures and pressures while maintaining high glycoside bond formation efficiency, fundamentally altering the energy requirements of the process.
4Ease of manufacture
If current methods are used to produce sugar alcohols from alkyl glycosides by hydrogenation, then no known processes exist, but typically sugar alcohols are produced by heating unmodified sugars at elevated pressure which is inefficient
Solution Approach 1:
The patent segments the production process into distinct stages: first producing alkyl glycosides from cellulose under mild conditions, then hydrogenating these glycosides to sugar alcohols. This segmentation allows each stage to be optimized independently, with the hydrogenation stage using mild conditions and selective catalysts to achieve high efficiency that cannot be obtained by direct hydrogenation of unmodified sugars.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
These methods achieve high selectivity yields of sugar alcohols and reduced polyols, such as 1,2,5,6-hexanetetrol, with improved economic viability and reduced formation of degradation products, enabling more efficient production pathways.
Implementation Method 1
heating an acetyl cellulose pulp in the presence of an alcohol of the formula ROH, where R is a C1-C4 alkyl group, and an acid catalyst selected from the group consisting of phosphonic acid and a sulfonic acid
Implementation Method 2
contacting a solution containing an R-glycoside with a hydrogenation catalyst for a time and at a temperature and a pressure sufficient to convert the R-glycoside to a mixture comprising the sugar alcohol and ROH
Implementation Method 3
contacting a solution comprising water and at least 20% wt/wt of a starting compound selected from the group consisting of a C6 sugar alcohol and a R-glycoside of a C6 sugar with hydrogen and a Raney copper catalyst
Implementation Method 4
acid catalysis converts hexanetriols into tetrahydrofuran derivatives
Data Source
AI summary
Disclosed herein are methods for synthesizing 1,2,5,6-hexanetetrol (HTO), 1,6 hexanediol (HDO) and other reduced polyols from C5 and C6 sugar alcohols or R glycosides. The methods include contacting the sugar alcohol or R-glycoside with a copper catalyst, most desirably a Raney copper catalyst with hydrogen for a time, temperature and pressure sufficient to form reduced polyols having 2 to 3 fewer hydoxy groups than the starting material. When the starting compound is a C6 sugar alcohol such as sorbitol or R-glycoside of a C6 sugar such as methyl glucoside, the predominant product is HTO. The same catalyst can be used to further reduce the HTO to HDO.