**Catalytic Thermochemical Conversion of Algae and Upgrading of Algal Oil for the Production of High-Grade Liquid Fuel: A Review**

### **Yingdong Zhou and Changwei Hu \***

Key Laboratory of Green Chemistry and Technology, Ministry of Education, College of Chemistry, Sichuan University, Chengdu 610064, Sichuan, China; yingdong\_zhou@163.com **\***Correspondence:changweihu@scu.edu.cn;Tel.: +86-28-85411105

Received: 27 December 2019; Accepted: 18 January 2020; Published: 21 January 2020

**Abstract:** The depletion of fossil fuel has drawn growing attention towards the utilization of renewable biomass for sustainable energy production. Technologies for the production of algae derived biofuel has attracted wide attention in recent years. Direct thermochemical conversion of algae obtained biocrude oil with poor fuel quality due to the complex composition of algae. Thus, catalysts are required in such process to remove the heteroatoms such as oxygen, nitrogen, and sulfur. This article reviews the recent advances in catalytic systems for the direct catalytic conversion of algae, as well as catalytic upgrading of algae-derived oil or biocrude into liquid fuels with high quality. Heterogeneous catalysts with high activity in deoxygenation and denitrogenation are preferable for the conversion of algae oil to high-grade liquid fuel. The paper summarized the influence of reaction parameters and reaction routes for the catalytic conversion process of algae from critical literature. The development of new catalysts, conversion conditions, and e fficiency indicators (yields and selectivity) from di fferent literature are presented and compared. The future prospect and challenges in general utilization of algae are also proposed.

**Keywords:** algae; bio-oil; thermochemical conversion; catalytic upgrading; high-grade liquid fuel
