Abstract

Industrial globalization and urbanization has placed man on a path for the quest of energy. Conspicuously there are various types and forms of energy with established technologies on harnessing and utilization wherein fossil fuel still remains the cheapest with straightforward application. Although, conventional fossil fuel resources are depleting because of population growth, unconventional reservoirs are exploited daily with limited production due to inadequate and expensive technology making them stand at approximately 9.1 trillion barrels poised to quell the world's energy insecurity for the next 100 years. The underlying basis for the high-cost of unconventional reservoirs upgrading is the hydrogen required to seal the alkyl chain after cracking to form low molecular weight hydrocarbons. Therefore, in this chapter we aim to provide a comprehensive review of in-situ generation of hydrogen from syngas via water gas shift reaction for the catalytic upgrading of heavy crude oil and bitumen by analyzing the gas chromatography results of gaseous effluents for the presence of syngas in the various works cited. Although, heavy crude oil and bitumen are non-renewable the upgrading method selected is tenable, appropriately the overall technology is partially sustainable.

Keywords: fuel, syngas, water gas shift reaction, heavy crude oil, bitumen, hydrogen, gas chromatography, sustainability

## 1. Introduction

Synthesis gas (Syngas) is a gas mixture containing carbon monoxide (CO) and hydrogen (H2) in dissimilar proportions produced from gasification of a carboncontaining material to gaseous products [1]. Also, water gas reaction (WGR) is a mixture of carbon monoxide and hydrogen produced by passing steam over red-hot coke in an endothermic reaction (Eq. 1).

$$\text{C} + \text{H}\_2\text{O} \rightarrow \text{CO} + \text{H}\_2\tag{1}$$

$$\text{C} + \text{CO}\_2 \rightarrow \text{2CO} \tag{2}$$

$$\text{CO} + \text{H}\_2\text{O} \leftrightarrow \text{CO}\_2 + \text{H}\_2\tag{3}$$

**30**

2018;**232**:420-428

*Sustainable Alternative Syngas Fuel*

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Reaction 3 in the above mechanism is foremost in order to shift the carbon monoxide entirely to hydrogen in the presence of an oxide based catalyst. This reaction can be applied separately and it is called the water gas shift reaction (WGSR) [2]. Detailed reaction mechanism for syngas production is displayed in Table 1 to depict where all these fit in.

2. Heavy oil upgrading

DOI: http://dx.doi.org/10.5772/intechopen.86236

methods of providing hydrogen.

reservoir conditions.

2.2 Production of syngas

direction.

33

2.1 Catalytic reaction in neutral environment

or hydrogen via the redox (syngas) reaction (Figure 1).

tion and carbon forming reactions as shown in Table 1 [34].

Heavy crude oil and bitumen upgrading technologies can be classified into; carbon rejection, hydrogen addition (hydrocracking) and separation processes [13, 14]. Hydrocracking is a process of upgrading heavy crude oil in the presence of hydrogen and a suitable catalyst, whereby the latter is usually dual functional with the hydrogenating and cracking sites, while the former inhibits secondary reactions that produce coke [15]. However, hydrocracking as simply defined above has been established to be the most suitable technology for heavy crude oil and bitumen upgrading [16]. Consequently, various methods abound for hydrocracking processes with distinct strategy along the lines of temperature and pressure operating conditions, type of reactors, composition and type of catalysts, and ultimately the

Sustainability Effect of Water Gas Shift Reaction (Syngas) in Catalytic Upgrading…

Hydrogen can be supplied directly as a pure gas [17–20], produced in-situ from chemical compounds and biological species [21–24], or extracted from syngas process in-situ via water gas shift reaction [20, 25–28]. In the first case, a significant amount of hydrogen proceed to hydrogen sulfide (H2S) [18, 20] and the process is over the odds [19]. The impediment of the second method is low conversion [22] and inability to operate at relatively higher reaction conditions due to biological species [23, 24]. However, supply of hydrogen via syngas is inexpensive [25], has high conversion rate [26–28] and the reaction could be operated between low water gas shift reaction (200–350°C) [28, 29] and high water gas shift reaction conditions (350–450°C) [20, 27]. In addition, higher upgrading has been reported with processes where hydrogen was obtained via syngas to pure hydrogen gas [26].

In heavy crude oil and bitumen upgrading where the hydrogen is supplied from syngas, the source is usually from water in-situ [13] or introduced into the reactor alongside feedstock [20, 25–31]. Irrespective of the method of providing water, the reactor would be pressurized in a neutral environment, usually nitrogen to mimic

Fumoto et al. [32] studied the suppression of coke generation in upgrading of bitumen by examining the time factor (W/F) of the catalyst and mixture of steam and nitrogen as feedstock at 500°C and atmospheric pressure. Meanwhile, Chao et al. [33] developed a new type of difunctional catalyst in heavy oil upgrading. The starting materials include; 100 g of heavy crude oil and water in a designed mass ratio, catalyst and nitrogen gas at 240°C and 3 MPa. Similarly, the role of water in the redox reaction between bitumen and water in the presence of a suitable catalyst was studied by Dejhosseini et al. [25]. They observed that bitumen cracking was supported either through oxidation of active oxygen species generated from water

Syngas process follows a series of endothermic and exothermic reaction steps, subdivided into three major units (not in order of occurrence); reforming, oxida-

It is suitable to state here that only at temperatures above 700°C would the SMR dominate carbon formation reactions, also the other steps of syngas production are reversible reactions except oxidation reactions which only goes in the forward

Reactions in syngas production follows series of steps subdivided into; reforming, oxidation and carbon forming with water gas shift passing off as a very rapid equilibrium reaction step. These three distinct reactions are independent in their own right and characterized by the reaction condition or active ingredient. Reforming reaction is partial combustion of methane or other hydrocarbon sources in the presence of water to form carbon monoxide and hydrogen, while oxidation reaction is the partial combustion of methane in oxygen to give carbon monoxide, carbon dioxide and hydrogen. On the other hand, carbon forming reaction is the reversible pyrolysis of methane or other hydrocarbon sources and disproportionation of carbon monoxide to carbon dioxide to form carbon and syngas.

Moreover, reports of current depletion of conventional fossil fuel reservoirs [3, 4] and increasing discoveries of heavy crude oil and bitumen deposits around the world [5, 6] has threatened global industrialization. However, this energy insecurity perceived in the near future could be averted with unconventional reservoirs upgrading which currently stands at 9.1 trillion barrels making it 70% of the world total oil resources [5].

Conversely, syngas is a promising fuel [7]. In the past it has been used to provide hydrogen for various industrial applications [8], and fuel sources in the case of fuel cells [9] and methanol synthesis [10]. In Fischer-Tropsch synthesis, it is used to manufacture liquid fuels from gas, coal or biomass [11]. Recently, it has found application as a direct fuel in hydrogen internal combustion engines for land and air transportations [12].

In this chapter we attempt to review the sustainable application of syngas in heavy crude oil and bitumen upgrading via water gas shift reaction. Various works on this area were critically discussed to ascertain the participation of syngas in the upgrading process via gas chromatography analysis of the gaseous product which shows high proportions of carbon dioxide and hydrogen when the starting materials are simply water in a neutral environment with a suitable catalyst and the heavy crude oil/bitumen hydrocarbon. Although, these hydrocarbons are non-renewable the upgrading method selected in this chapter is tenable, as a consequence the overall technology is partially sustainable.


Table 1. Reactions in syngas production.

Sustainability Effect of Water Gas Shift Reaction (Syngas) in Catalytic Upgrading… DOI: http://dx.doi.org/10.5772/intechopen.86236
