# Improved Bio-Oil Quality from Pyrolysis of Pine Biomass in Presurized Hydrogen
## 1 Introduction  
Biomass is one of the most potential renewable resources [1], which can replace fossil feedstocks to produce chemicals [2]. Biomass is renewable and widely distributed, causing low pollution [3]. The production of various chemicals from biomass is essential to alleviate the resource shortage and environmental problems currently [4].  
In recent years, much research has focused on pyrolysis, gasification, liquefaction, combustion, and carbonization of biomass [5]. Among these research topics, pyrolysis has attracted extensive attention [6]. With a low-cost and continuous production process, pyrolysis usually costs energy and produces renewables [7].  
Bio-oil, the liquid product of pyrolysis of biomass, has some similar properties to petroleum. The composition of bio-oil obtained from pyrolysis is very complex, and it has characteristics of high moisture content, oxygen content, and acidity, low heating value, poor thermal stability, and low content of each component. The method of refining this pyrolysis bio-oil to obtain specific chemicals is very inefficient [8]. The pyrolysis under different atmospheres and pressures can regulate the thermochemical conversion process of biomass, promote some reactions, and inhibit other reactions to realize the high enrichment of high value-added chemicals in pyrolysis bio-oil [9]. Then, chemicals with high purity are obtained through conventional separation treatment, and the remaining part of pyrolysis bio-oil can also be upgraded into fuel [10]. Therefore, pyrolysis could produce chemicals or fuels, thus remarkably increasing the utilization rate of biomass and improving the economy of the whole process [11].  
At present, hydrogasification of biomass involves a reaction under high temperature and pressure. The energy utilization rate of hydrogasification of biomass is high, and its thermal efficiency is close to 80%. Hydrogasification of biomass is an ideal technology thatcan convert coal to natural gas, and this method has attracted much researcher interest [12]. In recent years. The development and application of biomass conversion technologies (e.g., pyrolysis and catalytic pyrolysis) have also attracted extensive attention all over the world [13]. Among various biomass technologies, thermochemical conversion and hydro pyrolysis are considered relatively new methods to convert biomass into substitutes [14]. During hydrogasification of biomass, hydrogen may inhibit the re-polymerization of free radical fragments into carbon. Therefore, compared with ordinary pyrolysis, hydropyrolysis has the advantages of high carbon content, hydrocarbon yield, and bio-oil quality [15]. In addition, the hydrop pyrolysis process is self-heating and does not require additional heat, which is easier to expand to the commercial scale [16].  
In some studies, the pyrolysis bio-oil was upgraded through catalytic technology [17]. [PERSON] et al. [18] studied the hydrogasification of biomass and found that hydrogenolysis can directly generate high-quality and high-yield pyrolysis bio-oil and gaseous hydrocarbons without catalysts. The obtained pyrolysis bio-oil has low oxygen content and a high yield of light aromatics. The yields of benzene, toluene, and xylene (BTX) can reach 2.6%.  
In recent years, the study on pyrolysis mostly concentrated in the nitrogen atmosphere, and limited studies have focused on the pyrolysis of biomass for bio-oil production in the hydrogen atmosphere. In this paper, the pyrolysis bio-oil in a hydrogen atmosphere at a certain temperature and pressure was analyzed, characterized, and compared with the results of pyrolysis bio-oil in a nitrogen atmosphere. The pyrolysis mechanism of bio-oil in a hydrogen atmosphere is discussed, and the composition of the obtained pyrolysis bio-oil is preliminarily explored, thus providing support for the quality improvement of pyrolysis bio-oil from nuclear energy. This work improves the bio-oil quality of pine biomass pyrolysis in pressurized hydrogen gas and is an interesting experimental scheme for wood pyrolysis.