Synthesis and characteristics of organotin-based catalysts for acetylene hydrochlorination

Article abstract of DOI:10.1139/cjc-2017-0612

Organotin-based catalysts prepared by a facile and green synthesis route were used in the acetylene hydrochlorination reaction. In detail, organotin-based catalysts were directly synthesized by supporting both organotin and nitrogen compounds on a coal-based columnar activated carbon (AC) using both incipient wetness impregnation and calcination methods. Interestingly, upon addition of nitrogen compounds, the resultant (SnCl₄ + C₁₆H₃₄Cl₂Sn)/AC catalysts showed higher activity and stability when compared the its (SnCl₄ + C₁₆H₃₄Cl₂Sn + C₂N₄H₄)/AC counterpart at 200 °C and a gas hourly space velocity (GHSV, C₂H₂ based) of 30 h¹. According to the results, organotin was demonstrated to be the active site, whereas the incorporation of nitrogen allowed partial mitigation of the loss of active components.

Full text of DOI:10.1139/cjc-2017-0612

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Synthesis and characteristics of organotin-based catalysts for acetylene
hydrochlorination
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Yi-BoWu1, Bo-WenLi1, Fu-XiangLi 1, Jian-WeiXue1, Zhi-Ping Lv1
1Research Institute of Special Chemicals, Taiyuan University of technology, Taiyuan,
030024, P. R. China.
Correspomding author: FuꢀXiang Li, eꢀmail: L63f64x@163.com .
Abstract
Organotinꢀbased catalysts prepared by a facile and green synthesis route were used in
the acetylene hydrochlorination reaction. In detail, organotinꢀbased catalysts were directly
10 synthesized by supporting both organotin and nitrogen compounds on a coalꢀbased columnar
11 activated carbon (AC) using both incipient wetness impregnation and calcination methods.
12 Interestingly, upon addition of nitrogen compounds, the resultant (SnCl4+C16H34Cl2Sn)/AC
13 catalysts showed higher activity and stability when compared to its
14 (SnCl4+C16H34Cl2Sn+C2N4H4)/AC counterpart at 200 ºC and a gas hourly space velocity
15 (GHSV, C2H2 based) of 30 hꢀ1. According to the results, organotin was demonstrated to be the
16 active site, while the incorporation of nitrogen allowed to partly mitigate the loss of active
17 components.
18 Keywords: organotinꢀbased catalyst; organotin compounds; nitrogen compounds; acetylene
19 hydrochlorination.
20
21
1. Introduction
Polyvinylchloride (PVC) plays a significant role in agriculture, industry, electronic
22 science and national defense.1 The industrial production of PVC is typically carried out by
23 direct chlorination of ethylene, oxychlorination of ethylene, and acetylene hydrochlorination,
24 the latter of which is widely used in coalꢀrich regions of China.2 Nevertheless, the traditional
25 mercuryꢀbased catalysts used to carry out this reaction are easily lost during the course of the

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26 reaction. Additionally, mercuric chloride constitutes a potential threat to the environment and
27 to the human health. Thus, developing nonꢀmercury catalysts represents a sustainable
28 acetylene production route.
29
Hutchings et al. reported Auꢀbased catalysts to have superior catalytic performance
30 towards the hydrochlorination of acetylene and studied in detail the reaction mechanism of
31 these materials. The reduction of Au3+ was associated with catalyst deactivation.1,3,4 Although
32 preciousꢀmetal catalysts show excellent catalytic performance, it is of great significance to
33 explore nonꢀprecious metal catalysts with reduced cost. With this aim, numerous researchers
34 have started to develop newꢀtype catalysts.5–13 Later, Dai et al prepared boronꢀand nitrogenꢀ
35 doped graphene catalysts that displayed superior catalytic activity towards acetylene
36 hydrochlorination and demonstrated that boron and nitrogen can promote hydrogen chloride
37 adsorption.7 Additionally, the Dai’s group also reported ACꢀsupported transition metal
38 nitrides to show better activity and selectivity towards acetylene hydrochlorination.11
39
In the past few years, tin compounds have been investigated as promoters to reduce
40 coke deposition and therefore improve the catalytic activity and the stability of catalysts.14–17
41 Moreover, numerous diorganotins and triorganotins have been widely used as stabilizers,
42 catalysts and treatment materials for industrial and agricultural applications owing to their
43 unique structure, low toxicity and superior activity.18–22 In addition, Shinoda found that the
44 hydrochlorination activities of metal chlorides correlate with the affinity of the metal cation,
45 although their study did not include tin ions.23 Moreover, Zhang et al. reported that the
46 superior catalytic performance and relatively long lifetime of AuꢀSn/AC catalysts can be
47 improved by adding SnCl2·2H2O, which prevented coke deposition.8 At the same time,
48 organotin has been scarcely studies as an active site for the hydrochlorination of acetylene.
49 Having this in mind, the better activity of organotin motivated us to prepare organotinꢀbased
50 materials were applied in acetylene hydrochlorination.

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51
In this article, we successfully synthesized organotinꢀbased catalysts using highly
52 porous AC as a support. We simultaneously carried out thermogravimetry/differential thermal
53 analysis (TGꢀDTA), scanning electron microscopycoupled withenergy dispersive Xꢀray
54 spectrometry (SEMꢀEDS) elemental mapping and lowꢀtemperature nitrogen
55 adsorption/desorption experiments to characterize the organotinꢀbased catalyst.
56
2. Experimental
57 2.1 Catalyst preparation
58
The raw material (a coalꢀbased columnar AC) was preꢀtreated with HCl (0.01mol/L)
59 to remove impurities, thoroughly washed with distilled water until neutral pH, and finally
60 dried at 120 ºC for 24 h.
61
The organotinꢀbased catalyst was synthesized by an incipient wetness impregnation
62 technique using AC as a support. The impregnating solution was prepared by dissolving
63 dioctyldichlorotin (2.0 g) and tin (IV) chloride (2.0 g) in ethanol (100 mL) in a beaker. The
64 solution was stirred at 80 ºC (water bath) for 30min. Subsequently, 16 g of fresh AC were
65 gradually added under stirring, and the resulting mixture was stirred at 80 ºC or 2 h and
66 finally dried in an oven at 100 ºC for 12 h. The product was heated to 200 ºC under flowing
67 nitrogen for 4 h with a heating rate of 10 ºC/min to finally yield the catalyst. In addition,
68 different samples were prepared by the same method for comparison. 20%
69 (SnCl4+C16H34Cl2Sn)/ACꢀ200 indicates that the dioctyldichlorotin and tin (IV) chloride
70 loading in all the catalysts was fixed at 20 wt% and the calcination temperature was 200 ºC.
71 2.2 Catalytic performance tests
72
The performance of the organotinꢀbased catalyst was determined in a fixꢀbed glass
73 reactor (i.d. =10mm) at atmosphericpressure. Before initiating the reaction, hydrogen chloride
74 was passed through the fixꢀbed to remove air and water from the reaction system (60min).
75 Once the reactor reached the desired temperature (150–200 ºC), the gas mixture (HCl/C2H2

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76 =1.1:1.0) was calibrated using mass flowmeters and fed into the reactor containing 3.2 mL of
77 catalyst (gas hourly space velocity (GHSV) of 30 hꢀ1). The outlet gas was passed through a
78 glass tube containing medical sodaꢀlime to absorb the unreacted HCl and immediately
79 analyzed onꢀline using a gas chromatograph (GC900) equipped with a GDXꢀ301 column.
80 2.3 Catalyst characterization
81
The Brunauer–Emmett–Teller (BET) surface area and pore volume of the samples
82 were measured by nitrogen adsorption at 77 K using a Quantachrome Nova 2000e gas
83 sorption analyser. All the catalysts were degassed at 100 ºC for 5h before the analysis.
84
The weight loss and stability of the catalysts were analyzed by TGꢀDTA (NETZSCH
85 STA 449F3) under a nitrogen flow of 30 mL/min and at a heating rate of 30 ºC/min within a
86 temperature range of 25–800 ºC.
87
The SEM micrographs and the EDS elemental maps were recorded on a TEACAN
88 MAIA3 microscope at an acceleration voltage of 15 kV.
89
3. Results and discussion
90 3.1 Catalytic performance
91
The surface area and pore volume of the different samples are listed in Table 1, while the
92 catalytic performance of the catalysts is shown in Fig. 1. Fresh AC shows a negligible
93 conversion despite showing the highest specific surface area (987.2 m2/g). Upon calcination at
94 higher temperature, the specific surface area and micropore volume of the 20% C2N4H4/ACꢀ
95 550 sample decreased to 577.9 m2/g and 0.30 cm3/g, respectively, while the maximum
96 acetylene conversion reached 22.5%. Owing to dicyandiamide is easily transformed into gꢀ
97 C3N4,25 which was mostly dispersed on the micropores of the carbon material improving the
98 acetylene conversion. Interestingly, 20% C16H34Cl2Sn/ACꢀ200 significantly increased its
99 catalytic activity at 200 ºC and showed higher activity than SnCl4/ACꢀ200. This result, along

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100 with data in Table 1, confirmed that organotin was successfully loaded on AC and played an
101 active site in the acetylene hydrochlorination reaction.
102
Fig. 1b shows the effect of the dioctyldichlorotin loading (5ꢀ25wt%) on the catalytic
103 performance. The acetylene conversion gradually increased (from 36.3 to 86.4%) with the
104 dioctyldichlorotin loading increasing from 5 to 25 wt%. The decrease in surface area and pore
105 volume with the dioctyldichlorotin loading can be attributed to dioctyldichlorotin partly
106 blocking the surface of the support. 20% C16H34Cl2Sn/AC shows higher acetylene
107 conversions than 25% C16H34Cl2Sn/AC. Thus, the catalytic activity increased with the
108 dioctyldichlorotin content up to 20 wt%.
109
Because of the activity of dioctyldichlorotin and tin (IV) chloride, we focused our
110 investigations on the catalyst containing both components (i.e., (SnCl4+C16H34Cl2Sn)/AC))
111 which showed better catalytic performance than C16H34Cl2Sn/AC and SnCl4/AC. Importantly,
112 the mixture of dioctyldichlorotin and tin (IV) chloride can effectively reduce the cost of the
113 organotinꢀbased catalysts.
114 3.2 Catalytic performance of (SnCl4+C16H34Cl2Sn)/AC
115
The Kocheshkov redistribution reaction is commonly carried out without solvent and
116 thus it was necessary to investigatethe effect of the calcination temperature and mole ratio of
117 tin compounds on the catalytic performance of the materials prepared.26 As shown in Table 2,
118 the external surface area of (SnCl4+C16H34Cl2Sn)/AC gradually increased with the calcination
119 temperature, indicating that dioctyldichlorotin reacted with tin (IV) chloride at an optimal
120 calcination temperature of 200 ºC. As depicted in Fig. 2a, the optimum catalytic activity of
121 (SnCl4+C16H34Cl2Sn)/ACꢀ200 was not ascribed to its specific surface and volume
122 characteristics. Instead, the nature of the active site has a significant influence on the
123 acetylene conversion. As shown in Fig. 2b, the SnCl4:C16H34Cl2Sn mole ratio was 1.6:1.0,
124 suggesting that tin (IV) chloride reacted with dioctyldichlorotin to generate octyltrichlorotin.

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125 This was further supported by the fact that tin (IV) chloride was easily volatilized at
126 temperatures lower than the reaction temperature (114.5 ºC). As illustrated in Fig. 2a, the
127 maximum acetylene conversion of (SnCl4+C16H34Cl2Sn)/ACꢀ200 was 89.1% at 200 ℃, at a
128 SnCl4:C16H34Cl2Sn mole ratio of 1.6:1.0. However, this catalyst showed the maximum weight
129 loss rate at 230.6 ℃(Fig. 5), and we tried to improve the stability of the catalyst by adding
130 some components. For instance, Zhang et al. developed a nitrogenꢀmodified carbon supported
131 AuCl3 catalyst with superior stability, which was ascribed to nitrogen inhibiting the Au3+ to
132 Au0 reaction and enhancing the adsorption of hydrogen chloride.27 By temperatureꢀ
133 programmed adsorption and density functional theory (DFT) calculations, Dai et al.revealed
134 that the addition of nitrogen can improve the adsorption of HCl.6 Therefore, we used
135 dicyandiamide as
a
precursor of gꢀC3N4 for improving the lifetime of the
136 (SnCl4+C16H34Cl2Sn)/AC catalyst.
137 3.3 Catalytic performance of (SnCl4+C16H34Cl2Sn+C2N4H4)/AC
138
139
140
141
142
As shown in Table 3, the specific surface area and total pore volume of
(SnCl4+C16H34Cl2Sn+C2N4H4)/AC were slightly higher than that of
(C16H34Cl2Sn+SnCl4)/AC prepared at similar synthesis conditions, indicating that the active
compounds were successfully loaded on the support. In addition, the catalytic performance
of (SnCl4+C16H34Cl2Sn+C2N4H4)/AC (Fig. 2a and 3a) and (SnCl4+C16H34Cl2Sn)/AC
indistinctively changed over the temperature range of 150–300 ℃, showing that nitrogen
143
144
145
146
147
148
149
compounds played a small effect on the acetylene conversion of organotinꢀbased catalysts
at lower calcination temperatures. Over the temperature range of 350ꢀ500 ℃ (Fig. 3b),
(SnCl4+C16H34Cl2Sn+C2N4H4)/ACꢀ400 shows the lowest specific surface and total volume
values among the samples studied (233.0 m2/g and 0.15 cm3/g, respectively), indicating that
dicyandiamide may have reacted with tin (IV) chloride and dioctyldichlorotin to produce
molecules with larger molecular weight. Therefore, it is essential to study in detail the

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effect of the calcination temperature or nitrogen compounds on the conversion of acetylene.
As shown in Fig. 3c, (SnCl4+C16H34Cl2Sn+C2N4H4)/ACꢀ400 showed the best performance
among the organotin samples with an acetylene conversion of 92.1%. Thus, the optimal
calcination temperature of (SnCl4+C16H34Cl2Sn+C2N4H4)/AC was 400 ºC. The external
surface seems to influence the catalytic performance to a larger extent as compared to the
micropore surface (Table 3). With regard to the nitrogenꢀdoped catalysts,
(SnCl4+C16H34Cl2Sn+C2N4H4)/ACꢀ400 showed slightly higher acetylene conversions than
that of (SnCl4+C16H34Cl2Sn)/ACꢀ200 and (SnCl4+C16H34Cl2Sn)/ACꢀ400, illustrating that
the addition of nitrogen has a positive effect on the acetylene conversion at higher
calcination temperature, in line with results shown in Fig. 4a. The stability of both
catalysts should be investigated in detail.
161 3.4 Stability of (SnCl4+C16H34Cl2Sn)/AC and (SnCl4+C16H34Cl2Sn+C2N4H4)/AC
The catalytic performance and stability of (SnCl4+C16H34Cl2Sn+C2N4H4)/AC and
162
163 (SnCl4+C16H34Cl2Sn)/AC are illustrated in Fig. 4. By thermal condensation experiments, the
164 addition of dicyandiamide showed a minimal effect on the catalytic activity and selectivity,
165 whereas it dramatically improved the stability of the catalysts. As shown in Fig. 4a,
166 (SnCl4+C16H34Cl2Sn+C2N4H4)/AC showed higher catalytic activity and longer lifetimes than
167 (SnCl4+C16H34Cl2Sn)/AC (92.1 versus72.1% acetylene conversion) after 36 h on stream.The
168 acetylene conversion of (SnCl4+C16H34Cl2Sn)/AC decreased from 89.1 to 49.5% after 36 h on
169 stream, revealing poor stability towards the acetylene hydrochlorination reaction. As shown in
170 Fig. 4b, the selectivity towards vinyl chloride monomer (VCM) was above 97.5%. This result
171 demonstrated that organotin are highly active and selective species, while the addition of
172 dicyandiamide can strengthen the catalytic stability of organotinꢀbased catalysts during the
173 hydrochlorination of acetylene. While the catalytic performance of the organotinꢀbased

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174 catalysts was slightly poorer than that of 10%HgCl2/AC, the organotinꢀbased catalysts
175 showed a better selectivity towards vinyl chloride.
176
The TGA results (Fig. 5) confirmed that the addition of dicyandiamide is the main
177 factor affecting the catalytic stability. (SnCl4+C16H34Cl2Sn)/AC showed a mass loss of 22.7%,
178 in agreement with the loaded amount of active component. Nevertheless,
179 (SnCl4+C16H34Cl2Sn+C2N4H4)/AC showed a mass loss close to 13.7%, while the maximum
180 weight loss rates of the SnCl4+C16H34Cl2Sn)/AC and (SnCl4+C16H34Cl2Sn+C2N4H4)/AC
181 samples were found at 298.9 and 230.6 ºC, respectively. Fig. 5 and 6 confirmed that
182 dicyandiamide was added to organotin via calcination, being transformed into a novel
183 compound with a reduced maximum weight loss temperature.
184
We selected several areas to investigate the dispersion of tin and chlorine on the fresh
185 and used catalysts via EDS elemental mapping. As shown in Fig. 6a and c, tin and chlorine
186 were highly dispersed on the surface of the freshꢀ(SnCl4+C16H34Cl2Sn)/AC and freshꢀ
187 (SnCl4+C16H34Cl2Sn+C2N4H4)/AC samples. The distribution of tin in the usedꢀ
188 (SnCl4+C16H34Cl2Sn)/AC and usedꢀ(SnCl4+C16H34Cl2Sn+C2N4H4)/AC samples is shown in
189 Fig. 6b and d.The results of Fig. 5 and 6a and 6c strongly confirmed that organotin was
190 successfully loaded on the coalꢀbased columnar AC. Table 4 indicated that a large amount of
191 tin was dispersed on the surface of usedꢀ(SnCl4+C16H34Cl2Sn+C2N4H4)/AC versus usedꢀ
192 (SnCl4+C16H34Cl2Sn)/AC, because the incorporation of nitrogen effectively and significantly
193 reduced the loss of tin during reaction. Combining the above results, it is concluded that
194 organotin acted as a catalytic active site and the incorporation of nitrogen strongly enhanced
195 the stability of organotinꢀbased catalysts.
196
197
4. Conclusion
In this paper, we successfully synthesized organotinꢀbased catalysts having superior
198 catalytic performance and stability towards the hydrochlorination of acetylene. These

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199 catalysts were prepared by loading organotin and nitrogen compounds on an AC under
200 optimal conditions. The characterization data demonstrated that the effective addition of
201 dicyandiamide can prolong the lifetime of the organotinꢀbased catalysts, and organotin played
202 a positive effect in increasing the acetylene conversion.
203
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Tables
273 Table 1. Textural properties of the different catalysts.
274 [a] SBET is the surface area calculated using the Brunauer–Emmett–Teller (BET) equation
275 over the relative pressure range of 0.05–0.03. [b] Micropore surface area. [c] External surface
276 area calculated by the tꢀplot method. [d] Vmeso= Vtotal－Vmic(Vmic, micropore volume) is also
277 calculated by the tꢀplot method. [e] Vtotal (total volume) at P/P0=0.99 is derived from the
278 nitrogen adsorption isotherm.
279
Sample
Calcinations
Temperature
(℃)
SBET
Smic
Sext
Vmic
Vmeso
Vtotal
(m2/g)a
(m2/g)b
(m2/g)c
(m3/g)
(m3/g)d
(m3/g)e
ACꢀ200
200
550
200
200
200
200
200
200
987.2
641.9
474.2
84.7
864.5
577.9
422.6
51.4
122.7
64.0
51.6
33.8
34.1
58.4
73.3
72.9
0.12
0.23
0.18
0.06
0.06
0.10
0.14
0.19
0.36
0.07
0.05
0.02
0.03
0.06
0.07
0.07
0.48
0.30
0.23
0.08
0.09
0.16
0.21
0.26
20%C2N4H4/ACꢀ550
20%SnCl4/ACꢀ200
25%C16H34Cl2Sn/ACꢀ200
20%C16H34Cl2Sn/ACꢀ200
15%C16H34Cl2Sn/ACꢀ200
10%C16H34Cl2Sn/ACꢀ200
5%C16H34Cl2Sn/ACꢀ200
156.4
281.8
408.9
523.2
122.3
223.4
335.6
450.3
280
281
282
283
284
285
286
287
288

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289 Table 2. Textural properties of (SnCl4+C16H34Cl2Sn)/AC at different calcination
290 temperatures.The molar ratio of SnCl4 and C16H34Cl2Sn was1.6:1.0.
291
Sample
Calcinations
Temperature
(℃)
SBET
Smic
Sext
Vmic
Vmeso
Vtotal
(m2/g)a
(m2/g)b
(m2/g)c
(m3/g)
(m3/g)d
(m3/g)e
(SnCl4+C16H34Cl2Sn)/ACꢀ150
(SnCl4+C16H34Cl2Sn)/ACꢀ200
(SnCl4+C16H34Cl2Sn)/ACꢀ250
(SnCl4+C16H34Cl2Sn)/ACꢀ300
150
200
250
300
442.6
243.5
313.1
378.5
237.2
143.0
181.7
338.4
205.4
100.5
131.4
40.1
0.13
0.11
0.12
0.29
0.11
0.04
0.06
0.02
0.24
0.15
0.18
0.31
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308

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309 Table 3. Textural properties of (SnCl4+C16H34Cl2Sn+C2N4H4)/AC calcined at different
310 temperatures. The molar ratio of SnCl4, C16H34Cl2Sn, and C2N4H4was1.6:1.0:4.9.
311
Sample
Calcinations
Temperature
(℃)
SBET
Smic
Sext
Vmic
Vmeso
Vtotal
(m2/g)a
(m2/g)b
(m3/g)c
(m3/g)
(m3/g)d
(m3/g)e
(SnCl4+C16H34Cl2Sn+C2N4H4)/ACꢀ150
(SnCl4+C16H34Cl2Sn+C2N4H4)/ACꢀ200
(SnCl4+C16H34Cl2Sn+C2N4H4)/ACꢀ250
(SnCl4+C16H34Cl2Sn+C2N4H4)/ACꢀ300
(SnCl4+C16H34Cl2Sn+C2N4H4)/ACꢀ350
(SnCl4+C16H34Cl2Sn+C2N4H4)/ACꢀ400
(SnCl4+C16H34Cl2Sn+C2N4H4)/ACꢀ450
(SnCl4+C16H34Cl2Sn+C2N4H4)/ACꢀ500
(SnCl4+C16H34Cl2Sn)/ACꢀ400
150
200
250
300
350
400
450
500
400
200
173.3
340.5
440.9
567.6
298.9
233.0
314.5
463.8
374.0
571.0
135.0
287.8
372.5
494.3
257.8
160.8
179.7
400.7
300.6
479.6
38.3
52.7
68.4
73.3
47.1
72.2
134.8
63.1
73.4
91.4
0.07
0.12
0.15
0.21
0.11
0.11
0.11
0.17
0.26
0.20
0.05
0.05
0.08
0.06
0.05
0.04
0.08
0.06
0.03
0.09
0.11
0.17
0.23
0.27
0.16
0.15
0.19
0.23
0.29
0.29
HgCl2/AC
312
313
314
315
316
317
318
319
320
321
322
323

Page 15 of 19
15
324 Table 4. Mass percent of tin in the samples as detected by SEMꢀEDS.
Sample
Sn wt%
freshꢀC16H34Cl2Sn+SnCl4)/AC
usedꢀ(C16H34Cl2Sn+SnCl4)/AC
freshꢀ(C16H34Cl2Sn+SnCl4+C2N4H4)/AC
usedꢀ(C16H34Cl2Sn+SnCl4+C2N4H4)/AC
8.94
2.93
7.16
5.06
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344

Page 16 of 19
16
345
346
Figures
347 Fig. 1 (a) Conversion of acetylene for the different catalysts. (b) Catalytic activity of the
348 catalysts containing different amounts of dioctyldichlorotin.
349
350
351
352 Fig.
2
Conversion of acetylene for (SnCl4+C16H34Cl2Sn)/AC at (a) different
353 calcinationtemperatures, and (b) various mole ratio of tin compounds.
354 (1.0SnCl4+1.0C16H34Cl2Sn)/ACꢀ150 with a SnCl4:C16H34Cl2Sn molar ratio of 1.0:1.0. The
355 calcination temperature was150 ºC.
356
357
358 Fig. 3 Conversion of acetylene for (SnCl4+C16H34Cl2Sn+C2N4H4)/AC calcined at different
359 temperatures.

Page 17 of 19
17
360
361
362
363
364 Fig.
4
Catalytic performance of HgCl2/AC, (SnCl4+C16H34Cl2Sn)/AC and
365 (SnCl4+C16H34Cl2Sn+C2N4H4). (a) conversion of acetylene; (b) selectivity towards vinyl
366 chloride monomer (VCM).
367
368

Page 18 of 19
18
369 Fig.
5
TGA and DTG curves of the (SnCl4+C16H34Cl2Sn+C2N4H4)/AC and
370 (SnCl4+C16H34Cl2Sn)/AC catalysts.
371
372
373 Fig. 6 SEM micrographs and tin and chloride EDS elemental maps of the fresh samples: (a)
374 freshꢀ(SnCl4+C16H34Cl2Sn)/AC and (c) freshꢀ(SnCl4+C16H34Cl2Sn+C2N4H4)/AC and after 36
375
h
of
reaction:
(b)
usedꢀ(SnCl4+C16H34Cl2Sn)/AC
and
(d)
usedꢀ
376 (SnCl4+C16H34Cl2Sn+C2N4H4)/AC.
377
378

Page 19 of 19
19
379
380
381
382