Advances in the Catalytic Production and Utilization of Sorbitol Jun Zhang, Ji-biao Li, Shu-Bin Wu,* and Ying Liu* State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou, Guangdong, 510640, China ABSTRACT: Recently, research on the production and transformation of sorbitol has become exciting in chemical industry and in catalysis studies for its broad applications. It opens up a new path for achieving sustainable energy supply and chemicals production. Here we mainly review the catalytic routes for the synthesis of sorbitol and conversion of sorbitol into high value- added compounds such as lower alcohols, paraffins, isosorbide, and other derivatives. Meanwhile, some promising and valuable research directions are suggested based on the major challenges emerged in current research, such as the development of efficient magnetic catalysts, microwave heating, and other hydrogen sources. 1. INTRODUCTION For energy and economic reasons, extensive research has been carried out worldwide to study the efficient conversion of biomass resources into valuable biofuels and chemical materials in the last decades (Figure 1), since they have great merits such as abundance, renewable, and wide distribution when compared to other raw materials. 1-10 Among these explorations, one attractive route is the preparation and utilization of sorbitol, since it is known as one of the 12 important target chemicals in their biomass program. 11 Sorbitol being the most commonly used sugar alcohol (it is the least costly) holds the biggest market share among similar polyols, which is widely used in food, drugs, cosmetics, toothpaste, and so on. For example, it is an important precursor for the manufacture of L-ascorbic acid that consumes almost 15% of world sorbitol production. 12 Most importantly, sorbitol can be further degraded into polyols that are the downstream products in the petrochemical industry. 13 Meanwhile, it can be used for the synthesis of lactic acid under alkaline hydrothermal conditions. 14 Recent studies showed that the structure and the catalytic performance of some catalysts were significantly enhanced with the addition of sorbitol during catalyst preparation. 15-18 As a selective dehydration product of sorbitol, isosorbide has a special application in cosmetic, biomedicine, and polymers materials due to the rigid molecular structure and chiral centers. 19-21 In brief, the general preparation and conversion routes of sorbitol are clearly shown in Scheme 1. Usually the production of sorbitol is accomplished in a hydrogenation process; 22-25 however, reactions like hydrolysis and hydrogenation may be involved in the same reaction system due to the rapid development of research. Because biomass materials such as starch 26 and cellulose 27-29 are receiving increasing interest in recent work, leading to a great need in the improvement in the catalysts and/or reaction systems. Recently, the ruthenium catalysts showed higher hydrogenation activity than that of nickel and alloy catalysts. 23,30,31 With in-depth studies, unavoidable phenomen- on happens that sorbitol will be easily degraded in the presence of H 2 under high temperatures. Then lower alcohols, including glycol, 1,2-propylene glycol, and methanol, are formed after reaction. 32,33 Notably, these chemicals can be used to synthesize many high value-added products for the replacement of oil resources. As concerns the dehydration product, isosorbide is obtained by 2-fold dehydration of sorbitol via sorbitan under acidic conditions. It was reported that sulfuric acid and other inorganic acids were first used in the synthesis of isosorbide. 34-36 Due to high corrosion and environmental pollution of inorganic acids, some pollution-free and effective catalysts such as solid acids and acidic ion exchange resins are developed. Through the above analysis, we can see that a plethora of useful molecules will be obtained from multifunc- tional sorbitol via a series of reactions by using various catalysts. Although some published work deals with the topic of sorbitol chemistry to a certain degree, including conversion of cellulose into sorbitol and hydrogenolysis and dehydration of sorbitol, 37-39 this Review concentrates mainly on describing and analyzing all aspects of the work on sorbitol chemistry reported up to date. The improvement in catalytic synthesis and conversion of sorbitol with suitable reaction systems are discussed in greater detail, and some of the existing limitations and unsolved challenges are put forward at the same time. Owing to the rapidly expanding nature of this interesting field, we hope that this Review provides a helpful overview and insight to readers in this exciting research area. 2. SORBITOL PRODUCTION In commercial terms, sorbitol is an ideal, versatile compound that has been widely used in the fields of food and chemistry. The detailed information for physical properties of sorbitol is shown in Table 1. Three techniques are mainly introduced in the industrial production, namely, batch, semicontinuous, and continuous technology. It begins with raw materials like cassava, corn, or wheat that are first converted into dextrose through enzymatic hydrolysis and then was hydrogenated into sorbitol at 403-423 K with H 2 pressure ranging from 4.0 to 12.0 MPa. Among the manufacturers, Roquette Freres is the biggest sorbitol producer around the world, together with Cargill and SPI Polyols they hold a market share of over 70%. By the way, the yield of mannitol is accompanied during Received: April 14, 2013 Revised: July 28, 2013 Accepted: July 29, 2013 Published: July 29, 2013 Review pubs.acs.org/IECR © 2013 American Chemical Society 11799 dx.doi.org/10.1021/ie4011854 | Ind. Eng. Chem. Res. 2013, 52, 11799-11815